Keywords: QoS
Internet Engineering Task Force (IETF) J. Manner
Request for Comments: 5974 Aalto University
Category: Experimental G. Karagiannis
ISSN: 2070-1721 University of Twente/Ericsson
A. McDonald
Roke
October 2010
NSIS Signaling Layer Protocol (NSLP) for Quality-of-Service Signaling
Abstract
This specification describes the NSIS Signaling Layer Protocol (NSLP)
for signaling Quality of Service (QoS) reservations in the Internet.
It is in accordance with the framework and requirements developed in
NSIS. Together with General Internet Signaling Transport (GIST), it
provides functionality similar to RSVP and extends it. The QoS NSLP
is independent of the underlying QoS specification or architecture
and provides support for different reservation models. It is
simplified by the elimination of support for multicast flows. This
specification explains the overall protocol approach, describes the
design decisions made, and provides examples. It specifies object,
message formats, and processing rules.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5974.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Overall Approach . . . . . . . . . . . . . . . . . . . . . 6
3.1.1. Protocol Messages . . . . . . . . . . . . . . . . . . 9
3.1.2. QoS Models and QoS Specifications . . . . . . . . . . 10
3.1.3. Policy Control . . . . . . . . . . . . . . . . . . . . 12
3.2. Design Background . . . . . . . . . . . . . . . . . . . . 13
3.2.1. Soft States . . . . . . . . . . . . . . . . . . . . . 13
3.2.2. Sender and Receiver Initiation . . . . . . . . . . . . 13
3.2.3. Protection against Message Re-ordering and
Duplication . . . . . . . . . . . . . . . . . . . . . 14
3.2.4. Explicit Confirmations . . . . . . . . . . . . . . . . 14
3.2.5. Reduced Refreshes . . . . . . . . . . . . . . . . . . 14
3.2.6. Summary Refreshes and Summary Tear . . . . . . . . . . 15
3.2.7. Message Scoping . . . . . . . . . . . . . . . . . . . 15
3.2.8. Session Binding . . . . . . . . . . . . . . . . . . . 16
3.2.9. Message Binding . . . . . . . . . . . . . . . . . . . 16
3.2.10. Layering . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.11. Support for Request Priorities . . . . . . . . . . . . 18
3.2.12. Rerouting . . . . . . . . . . . . . . . . . . . . . . 19
3.2.13. Preemption . . . . . . . . . . . . . . . . . . . . . . 24
3.3. GIST Interactions . . . . . . . . . . . . . . . . . . . . 24
3.3.1. Support for Bypassing Intermediate Nodes . . . . . . . 25
3.3.2. Support for Peer Change Identification . . . . . . . . 25
3.3.3. Support for Stateless Operation . . . . . . . . . . . 26
3.3.4. Priority of Signaling Messages . . . . . . . . . . . . 26
3.3.5. Knowledge of Intermediate QoS-NSLP-Unaware Nodes . . . 26
4. Examples of QoS NSLP Operation . . . . . . . . . . . . . . . . 26
4.1. Sender-Initiated Reservation . . . . . . . . . . . . . . . 27
4.2. Sending a Query . . . . . . . . . . . . . . . . . . . . . 28
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4.3. Basic Receiver-Initiated Reservation . . . . . . . . . . . 29
4.4. Bidirectional Reservations . . . . . . . . . . . . . . . . 31
4.5. Aggregate Reservations . . . . . . . . . . . . . . . . . . 33
4.6. Message Binding . . . . . . . . . . . . . . . . . . . . . 34
4.7. Reduced-State or Stateless Interior Nodes . . . . . . . . 38
4.7.1. Sender-Initiated Reservation . . . . . . . . . . . . . 38
4.7.2. Receiver-Initiated Reservation . . . . . . . . . . . . 40
4.8. Proxy Mode . . . . . . . . . . . . . . . . . . . . . . . . 41
5. QoS NSLP Functional Specification . . . . . . . . . . . . . . 42
5.1. QoS NSLP Message and Object Formats . . . . . . . . . . . 42
5.1.1. Common Header . . . . . . . . . . . . . . . . . . . . 42
5.1.2. Message Formats . . . . . . . . . . . . . . . . . . . 44
5.1.3. Object Formats . . . . . . . . . . . . . . . . . . . . 47
5.2. General Processing Rules . . . . . . . . . . . . . . . . . 60
5.2.1. State Manipulation . . . . . . . . . . . . . . . . . . 61
5.2.2. Message Forwarding . . . . . . . . . . . . . . . . . . 62
5.2.3. Standard Message Processing Rules . . . . . . . . . . 62
5.2.4. Retransmissions . . . . . . . . . . . . . . . . . . . 62
5.2.5. Rerouting . . . . . . . . . . . . . . . . . . . . . . 63
5.3. Object Processing . . . . . . . . . . . . . . . . . . . . 65
5.3.1. Reservation Sequence Number (RSN) . . . . . . . . . . 65
5.3.2. Request Identification Information (RII) . . . . . . . 66
5.3.3. BOUND-SESSION-ID . . . . . . . . . . . . . . . . . . . 67
5.3.4. REFRESH-PERIOD . . . . . . . . . . . . . . . . . . . . 67
5.3.5. INFO-SPEC . . . . . . . . . . . . . . . . . . . . . . 68
5.3.6. SESSION-ID-LIST . . . . . . . . . . . . . . . . . . . 70
5.3.7. RSN-LIST . . . . . . . . . . . . . . . . . . . . . . . 71
5.3.8. QSPEC . . . . . . . . . . . . . . . . . . . . . . . . 71
5.4. Message Processing Rules . . . . . . . . . . . . . . . . . 72
5.4.1. RESERVE Messages . . . . . . . . . . . . . . . . . . . 72
5.4.2. QUERY Messages . . . . . . . . . . . . . . . . . . . . 77
5.4.3. RESPONSE Messages . . . . . . . . . . . . . . . . . . 78
5.4.4. NOTIFY Messages . . . . . . . . . . . . . . . . . . . 79
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 80
6.1. QoS NSLP Message Type . . . . . . . . . . . . . . . . . . 81
6.2. NSLP Message Objects . . . . . . . . . . . . . . . . . . . 81
6.3. QoS NSLP Binding Codes . . . . . . . . . . . . . . . . . . 82
6.4. QoS NSLP Error Classes and Error Codes . . . . . . . . . . 82
6.5. QoS NSLP Error Source Identifiers . . . . . . . . . . . . 83
6.6. NSLP IDs and Router Alert Option Values . . . . . . . . . 83
7. Security Considerations . . . . . . . . . . . . . . . . . . . 83
7.1. Trust Relationship Model . . . . . . . . . . . . . . . . . 85
7.2. Authorization Model Examples . . . . . . . . . . . . . . . 87
7.2.1. Authorization for the Two-Party Approach . . . . . . . 87
7.2.2. Token-Based Three-Party Approach . . . . . . . . . . . 88
7.2.3. Generic Three-Party Approach . . . . . . . . . . . . . 90
7.3. Computing the Authorization Decision . . . . . . . . . . . 90
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 91
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9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 91
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 91
10.1. Normative References . . . . . . . . . . . . . . . . . . . 91
10.2. Informative References . . . . . . . . . . . . . . . . . . 91
Appendix A. Abstract NSLP-RMF API . . . . . . . . . . . . . . . . 94
A.1. Triggers from QOS-NSLP towards RMF . . . . . . . . . . . . 94
A.2. Triggers from RMF/QOSM towards QOS-NSLP . . . . . . . . . 96
A.3. Configuration Interface . . . . . . . . . . . . . . . . . 99
Appendix B. Glossary . . . . . . . . . . . . . . . . . . . . . 100
1. Introduction
This document defines a Quality of Service (QoS) NSIS Signaling Layer
Protocol (NSLP), henceforth referred to as the "QoS NSLP". This
protocol establishes and maintains state at nodes along the path of a
data flow for the purpose of providing some forwarding resources for
that flow. It is intended to satisfy the QoS-related requirements of
RFC 3726 [RFC3726]. This QoS NSLP is part of a larger suite of
signaling protocols, whose structure is outlined in the NSIS
framework [RFC4080]. The abstract NTLP has been developed into a
concrete protocol, GIST (General Internet Signaling Transport)
[RFC5971]. The QoS NSLP relies on GIST to carry out many aspects of
signaling message delivery.
The design of the QoS NSLP is conceptually similar to RSVP [RFC2205]
and uses soft-state peer-to-peer refresh messages as the primary
state management mechanism (i.e., state installation/refresh is
performed between pairs of adjacent NSLP nodes, rather than in an
end-to-end fashion along the complete signaling path). The QoS NSLP
extends the set of reservation mechanisms to meet the requirements of
RFC 3726 [RFC3726], in particular, support of sender- or receiver-
initiated reservations, as well as a type of bidirectional
reservation and support of reservations between arbitrary nodes,
e.g., edge-to-edge, end-to-access, etc. On the other hand, there is
currently no support for IP multicast.
A distinction is made between the operation of the signaling protocol
and the information required for the operation of the Resource
Management Function (RMF). This document describes the signaling
protocol, whilst [RFC5975] describes the RMF-related information
carried in the QSPEC (QoS Specification) object in QoS NSLP messages.
This is similar to the decoupling between RSVP and the IntServ
architecture [RFC1633]. The QSPEC carries information on resources
available, resources required, traffic descriptions, and other
information required by the RMF.
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This document is structured as follows. The overall protocol design
is outlined in Section 3.1. The operation and use of the QoS NSLP is
described in more detail in the rest of Section 3. Section 4 then
clarifies the protocol by means of a number of examples. These
sections should be read by people interested in the overall protocol
capabilities. The functional specification in Section 5 contains
more detailed object and message formats and processing rules and
should be the basis for implementers. The subsequent sections
describe IANA allocation issues and security considerations.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The terminology defined by GIST [RFC5971] applies to this document.
In addition, the following terms are used:
QNE: an NSIS Entity (NE), which supports the QoS NSLP.
QNI: the first node in the sequence of QNEs that issues a reservation
request for a session.
QNR: the last node in the sequence of QNEs that receives a
reservation request for a session.
P-QNE: Proxy-QNE, a node set to reply to messages with the PROXY
scope flag set.
Session: A session defines an association between a QNI and QNR
related to a data flow. Intermediate QNEs on the path, the QNI, and
the QNR use the same identifier to refer to the state stored for the
association. The same QNI and QNR may have more than one session
active at any one time.
Session Identification (SESSION-ID, SID): This is a cryptographically
random and (probabilistically) globally unique identifier of the
application-layer session that is associated with a certain flow.
Often, there will only be one data flow for a given session, but in
mobility/multihoming scenarios, there may be more than one, and they
may be differently routed [RFC4080].
Source or message source: The one of two adjacent NSLP peers that is
sending a signaling message (maybe the upstream or the downstream
peer). Note that this is not necessarily the QNI.
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QoS NSLP operation state: State used/kept by the QoS NSLP processing
to handle messaging aspects.
QoS reservation state: State used/kept by the Resource Management
Function to describe reserved resources for a session.
Flow ID: This is essentially the Message Routing Information (MRI) in
GIST for path-coupled signaling.
Figure 1 shows the components that have a role in a QoS NSLP
signaling session. The flow sender and receiver would in most cases
be part of the QNI and QNR nodes. Yet, these may be separate nodes,
too.
QoS NSLP nodes
IP address (QoS-unaware NSIS nodes are IP address
= Flow not shown) = Flow
Source | | | Destination
Address | | | Address
V V V
+--------+ Data +------+ +------+ +------+ +--------+
| Flow |-------|------|------|------|-------|------|---->| Flow |
| Sender | Flow | | | | | | |Receiver|
+--------+ | QNI | | QNE | | QNR | +--------+
| | | | | |
+------+ +------+ +------+
=====================>
<=====================
Signaling
Flow
Figure 1: Components of the QoS NSLP Architecture
A glossary of terms and abbreviations used in this document can be
found in Appendix B.
3. Protocol Overview
3.1. Overall Approach
This section presents a logical model for the operation of the QoS
NSLP and associated provisioning mechanisms within a single node.
The model is shown in Figure 2.
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+-----------------+
| Local |
| Applications or |
|Management (e.g.,|
| for aggregates) |
+-----------------+
^
V
V
+----------+ +----------+ +---------+
| QoS NSLP | | Resource | | Policy |
|Processing|<<<<<<>>>>>>>|Management|<<<>>>| Control |
+----------+ +----------+ +---------+
. ^ | * ^
| V . * ^
+----------+ * ^
| NTLP | * ^
|Processing| * V
+----------+ * V
| | * V
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
. . * V
| | * .............................
. . * . Traffic Control .
| | * . +---------+.
. . * . |Admission|.
| | * . | Control |.
+----------+ +------------+ . +---------+.
<-.-| Input | | Outgoing |-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->
| Packet | | Interface | .+----------+ +---------+.
===>|Processing|====| Selection |===.| Packet |====| Packet |.==>
| | |(Forwarding)| .|Classifier| Scheduler|.
+----------+ +------------+ .+----------+ +---------+.
.............................
<.-.-> = signaling flow
=====> = data flow (sender --> receiver)
<<<>>> = control and configuration operations
****** = routing table manipulation
Figure 2: QoS NSLP in a Node
This diagram shows an example implementation scenario where QoS
conditioning is performed on the output interface. However, this
does not limit the possible implementations. For example, in some
cases, traffic conditioning may be performed on the incoming
interface, or it may be split over the input and output interfaces.
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Also, the interactions with the Policy Control component may be more
complex, involving interaction with the Resource Management Function,
and the AAA infrastructure.
From the perspective of a single node, the request for QoS may result
from a local application request or from processing an incoming QoS
NSLP message. The request from a local application includes not only
user applications but also network management and the policy control
module. For example, a request could come from multimedia
applications, initiate a tunnel to handle an aggregate, interwork
with some other reservation protocol (such as RSVP), and contain an
explicit teardown triggered by a AAA policy control module. In this
sense, the model does not distinguish between hosts and routers.
Incoming messages are captured during input packet processing and
handled by GIST. Only messages related to QoS are passed to the QoS
NSLP. GIST may also generate triggers to the QoS NSLP (e.g.,
indications that a route change has occurred). The QoS request is
handled by the RMF, which coordinates the activities required to
grant and configure the resource. It also handles policy-specific
aspects of QoS signaling.
The grant processing involves two local decision modules, 'policy
control' and 'admission control'. Policy control determines whether
the user is authorized to make the reservation. Admission control
determines whether the network of the node has sufficient available
resources to supply the requested QoS. If both checks succeed,
parameters are set in the packet classifier and in the link-layer
interface (e.g., in the packet scheduler) to obtain the desired QoS.
Error notifications are passed back to the request originator. The
Resource Management Function may also manipulate the forwarding
tables at this stage to select (or at least pin) a route; this must
be done before interface-dependent actions are carried out (including
sending outgoing messages over any new route), and is in any case
invisible to the operation of the protocol.
Policy control is expected to make use of the authentication
infrastructure or the authentication protocols external to the node
itself. Some discussion can be found in a separate document on
authorization issues [qos-auth]. More generally, the processing of
policy and Resource Management Functions may be outsourced to an
external node, leaving only 'stubs' co-located with the NSLP node;
this is not visible to the protocol operation. A more detailed
discussion of authentication and authorization can be found in
Section 3.1.3.
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Admission control, packet scheduling, and any part of policy control
beyond simple authorization have to be implemented using specific
definitions for types and levels of QoS. A key assumption is made
that the QoS NSLP is independent of the QoS parameters (e.g., IntServ
service elements). These are captured in a QoS model and interpreted
only by the resource management and associated functions, and are
opaque to the QoS NSLP itself. QoS models are discussed further in
Section 3.1.2.
The final stage of processing for a resource request is to indicate
to the QoS NSLP protocol processing that the required resources have
been configured. The QoS NSLP may generate an acknowledgment message
in one direction, and may forward the resource request in the other.
Message routing is carried out by the GIST module. Note that while
Figure 2 shows a unidirectional data flow, the signaling messages can
pass in both directions through the node, depending on the particular
message and orientation of the reservation.
3.1.1. Protocol Messages
The QoS NSLP uses four message types:
RESERVE: The RESERVE message is the only message that manipulates QoS
NSLP reservation state. It is used to create, refresh, modify, and
remove such state. The result of a RESERVE message is the same
whether a message is received once or many times.
QUERY: A QUERY message is used to request information about the data
path without making a reservation. This functionality can be used to
make reservations or to support certain QoS models. The information
obtained from a QUERY may be used in the admission control process of
a QNE (e.g., in case of measurement-based admission control). Note
that a QUERY does not change existing reservation state.
RESPONSE: The RESPONSE message is used to provide information about
the result of a previous QoS NSLP message. This includes explicit
confirmation of the state manipulation signaled in the RESERVE
message, and the response to a QUERY message or an error code if the
QNE or QNR is unable to provide the requested information or if the
response is negative. The RESPONSE message does not cause any
reservation state to be installed or modified.
NOTIFY: NOTIFY messages are used to convey information to a QNE.
They differ from RESPONSE messages in that they are sent
asynchronously and need not refer to any particular state or
previously received message. The information conveyed by a NOTIFY
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message is typically related to error conditions. Examples would be
notification to an upstream peer about state being torn down or
notification when a reservation has been preempted.
QoS NSLP messages are sent peer-to-peer. This means that a QNE
considers its adjacent upstream or downstream peer to be the source
of each message.
Each protocol message has a common header which indicates the message
type and contains various flag bits. Message formats are defined in
Section 5.1.2. Message processing rules are defined in Section 5.4.
QoS NSLP messages contain three types of objects:
1. Control Information: Control information objects carry general
information for the QoS NSLP processing, such as sequence numbers
or whether a response is required.
2. QoS specifications (QSPECs): QSPEC objects describe the actual
resources that are required and depend on the QoS model being
used. Besides any resource description, they may also contain
other control information used by the RMF's processing.
3. Policy objects: Policy objects contain data used to authorize the
reservation of resources.
Object formats are defined in Section 5.1.3. Object processing rules
are defined in Section 5.3.
3.1.2. QoS Models and QoS Specifications
The QoS NSLP provides flexibility over the exact patterns of
signaling messages that are exchanged. The decoupling of QoS NSLP
and QSPEC allows the QoS NSLP to be ignorant about the ways in which
traffic, resources, etc., are described, and it can treat the QSPEC
as an opaque object. Various QoS models can be designed, and these
do not affect the specification of the QoS NSLP protocol. Only the
RMF specific to a given QoS model will need to interpret the QSPEC.
The Resource Management Function (RMF) reserves resources for each
flow.
The QSPEC fulfills a similar purpose to the TSpec, RSpec, and AdSpec
objects used with RSVP and specified in RFC 2205 [RFC2205] and RFC
2210 [RFC2210]. At each QNE, the content of the QSPEC is interpreted
by the Resource Management Function and the Policy Control Function
for the purposes of traffic and policy control (including admission
control and configuration of the packet classifier and scheduler).
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The QoS NSLP does not mandate any particular behavior for the RMF,
instead providing interoperability at the signaling-protocol level
whilst leaving the validation of RMF behavior to contracts external
to the protocol itself. The RMF may make use of various elements
from the QoS NSLP message, not only the QSPEC object.
Still, this specification assumes that resource sharing is possible
between flows with the same SESSION-ID that originate from the same
QNI or between flows with a different SESSION-ID that are related
through the BOUND-SESSION-ID object. For flows with the same
SESSION-ID, resource sharing is only applicable when the existing
reservation is not just replaced (which is indicated by the REPLACE
flag in the common header). We assume that the QoS model supports
resource sharing between flows. A QoS Model may elect to implement a
more general behavior of supporting relative operations on existing
reservations, such as ADDING or SUBTRACTING a certain amount of
resources from the current reservation. A QoS Model may also elect
to allow resource sharing more generally, e.g., between all flows
with the same Differentiated Service Code Point (DSCP).
The QSPEC carries a collection of objects that can describe QoS
specifications in a number of different ways. A generic template is
defined in [RFC5975] and contains object formats for generally useful
elements of the QoS description, which is designed to ensure
interoperability when using the basic set of objects. A QSPEC
describing the resources requested will usually contain objects that
need to be understood by all implementations, and it can also be
enhanced with additional objects specific to a QoS model to provide a
more exact definition to the RMF, which may be better able to use its
specific resource management mechanisms (which may, e.g., be link
specific) as a result.
A QoS Model defines the behavior of the RMF, including inputs and
outputs, and how QSPEC information is used to describe resources
available, resources required, traffic descriptions, and control
information required by the RMF. A QoS Model also describes the
minimum set of parameters QNEs should use in the QSPEC when signaling
about this QoS Model.
QoS Models may be local (private to one network), implementation/
vendor specific, or global (implementable by different networks and
vendors). All QSPECs should follow the design of the QSPEC template.
The definition of a QoS model may also have implications on how local
behavior should be implemented in the areas where the QoS NSLP gives
freedom to implementers. For example, it may be useful to identify
recommended behavior for how a forwarded RESERVE message relates to a
received one, or for when additional signaling sessions should be
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started based on existing sessions, such as required for aggregate
reservations. In some cases, suggestions may be made on whether
state that may optionally be retained should be held in particular
scenarios. A QoS model may specify reservation preemption, e.g., an
incoming resource request may cause removal of an earlier established
reservation.
3.1.3. Policy Control
Getting access to network resources, e.g., network access in general
or access to QoS, typically involves some kind of policy control.
One example of this is authorization of the resource requester.
Policy control for QoS NSLP resource reservation signaling is
conceptually organized as illustrated below in Figure 3.
+-------------+
| Policy |
| Decision |
| Point (PDP) |
+------+------+
|
/-\-----+-----/\
//// \\\\
|| ||
| Policy transport |
|| ||
\\\\ ////
\-------+------/
|
+-------------+ QoS signaling +------+------+
| Entity |<==============>| QNE = Policy|<=========>
| requesting | Data Flow | Enforcement |
| resource |----------------|-Point (PEP)-|---------->
+-------------+ +-------------+
Figure 3: Policy Control with the QoS NSLP Signaling
From the QoS NSLP point of view, the policy control model is
essentially a two-party model between neighboring QNEs. The actual
policy decision may depend on the involvement of a third entity (the
Policy Decision Point, PDP), but this happens outside of the QoS NSLP
protocol by means of existing policy infrastructure (Common Open
Policy Service (COPS), Diameter, etc.). The policy control model for
the entire end-to-end chain of QNEs is therefore one of transitivity,
where each of the QNEs exchanges policy information with its QoS NSLP
policy peer.
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The authorization of a resource request often depends on the identity
of the entity making the request. Authentication may be required.
The GIST channel security mechanisms provide one way of
authenticating the QoS NSLP peer that sent the request, and so may be
used in making the authorization decision.
Additional information might also be provided in order to assist in
making the authorization decision. This might include alternative
methods of authenticating the request.
The QoS NSLP does not currently contain objects to carry
authorization information. At the time of writing, there exists a
separate individual work [NSIS-AUTH] that defines this functionality
for the QoS NSLP and the NAT and firewall (NATFW) NSLP.
It is generally assumed that policy enforcement is likely to
concentrate on border nodes between administrative domains. This may
mean that nodes within the domain are "Policy-Ignorant Nodes" that
perform no per-request authentication or authorization, relying on
the border nodes to perform the enforcement. In such cases, the
policy management between ingress and egress edge of a domain relies
on the internal chain of trust between the nodes in the domain. If
this is not acceptable, a separate signaling session can be set up
between the ingress and egress edge nodes in order to exchange policy
information.
3.2. Design Background
This section presents some of the key functionality behind the
specification of the QoS NSLP.
3.2.1. Soft States
The NSIS protocol suite takes a soft-state approach to state
management. This means that reservation state in QNEs must be
periodically refreshed. The frequency with which state installation
is refreshed is expressed in the REFRESH-PERIOD object. This object
contains a value in milliseconds indicating how long the state that
is signaled for remains valid. Maintaining the reservation beyond
this lifetime can be done by sending a RESERVE message periodically.
3.2.2. Sender and Receiver Initiation
The QoS NSLP supports both sender-initiated and receiver-initiated
reservations. For a sender-initiated reservation, RESERVE messages
travel in the same direction as the data flow that is being signaled
for (the QNI is at the side of the source of the data flow). For a
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receiver-initiated reservation, RESERVE messages travel in the
opposite direction (the QNI is at the side of the receiver of the
data flow).
Note: these definitions follow the definitions in Section 3.3.1 of
RFC 4080 [RFC4080]. The main issue is about which node is in charge
of requesting and maintaining the resource reservation. In a
receiver-initiated reservation, even though the sender sends the
initial QUERY, the receiver is still in charge of making the actual
resource request and maintaining the reservation.
3.2.3. Protection against Message Re-ordering and Duplication
RESERVE messages affect the installed reservation state. Unlike
NOTIFY, QUERY, and RESPONSE messages, the order in which RESERVE
messages are received influences the eventual reservation state that
will be stored at a QNE; that is, the most recent RESERVE message
replaces the current reservation. Therefore, in order to protect
against RESERVE message re-ordering or duplication, the QoS NSLP uses
a Reservation Sequence Number (RSN). The RSN has local significance
only, i.e., between a QNE and its downstream peers.
3.2.4. Explicit Confirmations
A QNE may require a confirmation that the end-to-end reservation is
in place, or a reply to a query along the path. For such requests,
it must be able to keep track of which request each response refers
to. This is supported by including a Request Identification
Information (RII) object in a QoS NSLP message.
3.2.5. Reduced Refreshes
For scalability, the QoS NSLP supports an abbreviated form of refresh
RESERVE message. In this case, the refresh RESERVE references the
reservation using the RSN and the SESSION-ID, and does not include
the full reservation specification (including QSPEC). By default,
state refresh should be performed with reduced refreshes in order to
save bytes during transmission. Stateless QNEs will require full
refresh since they do not store the whole reservation information.
If the stateful QNE does not support reduced refreshes, or there is a
mismatch between the local and received RSN, the stateful QNE must
reply with a RESPONSE carrying an INFO-SPEC indicating the error.
Furthermore, the QNE must stop sending reduced refreshes to this peer
if the error indicates that support for this feature is lacking.
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3.2.6. Summary Refreshes and Summary Tear
For limiting the number of individual messages, the QoS NSLP supports
summary refresh and summary tear messages. When sending a refreshing
RESERVE for a certain (primary) session, a QNE may include a SESSION-
ID-LIST object where the QNE indicates (secondary) sessions that are
also refreshed. An RSN-LIST object must also be added. The SESSION-
IDs and RSNs are stacked in the objects such that the index in both
stacks refer to the same reservation state, i.e., the SESSION-ID and
RSN at index i in both objects refers to the same session. If the
receiving stateful QNE notices unknown SESSION-IDs or a mismatch with
RSNs for a session, it will reply back to the upstream stateful QNE
with an error.
In order to tear down several sessions at once, a QNE may include
SESSION-ID-LIST and RSN-LIST objects in a tearing reserve. The
downstream stateful QNE must then also tear down the other sessions
indicated. The downstream stateful QNE must silently ignore any
unknown SESSION-IDs.
GIST provides a SII-Handle for every downstream session. The SII-
Handle identifies a peer and should be the same for all sessions
whose downstream peer is the same. The QoS NSLP uses this
information to decide whether summary refresh messages can be sent or
when a summary tear is possible.
3.2.7. Message Scoping
A QNE may use local policy when deciding whether to propagate a
message or not. For example, the local policy can define/configure
that a QNE is, for a particular session, a QNI and/or a QNR. The QoS
NSLP also includes an explicit mechanism to restrict message
propagation by means of a scoping mechanism.
For a RESERVE or a QUERY message, two scoping flags limit the part of
the path on which state is installed on the downstream nodes that can
respond. When the SCOPING flag is set to zero, it indicates that the
scope is "whole path" (default). When set to one, the scope is
"single hop". When the PROXY scope flag is set, the path is
terminated at a pre-defined Proxy QNE (P-QNE). This is similar to
the Localized RSVP [lrsvp].
The propagation of a RESPONSE message is limited by the RII object,
which ensures that it is not forwarded back along the path further
than the node that requested the RESPONSE.
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3.2.8. Session Binding
Session binding is defined as the enforcement of a relation between
different QoS NSLP sessions (i.e., signaling flows with different
SESSION-IDs (SIDs) as defined in GIST [RFC5971]).
Session binding indicates a unidirectional dependency relation
between two or more sessions by including a BOUND-SESSION-ID object.
A session with SID_A (the binding session) can express its
unidirectional dependency relation to another session with SID_B (the
bound session) by including a BOUND-SESSION-ID object containing
SID_B in its messages.
The concept of session binding is used to indicate the unidirectional
dependency relation between the end-to-end session and the aggregate
session in case of aggregate reservations. In case of bidirectional
reservations, it is used to express the unidirectional dependency
relation between the sessions used for forward and reverse
reservation. Typically, the dependency relation indicated by session
binding is purely informative in nature and does not automatically
trigger any implicit action in a QNE. A QNE may use the dependency
relation information for local resource optimization or to explicitly
tear down reservations that are no longer useful. However, by using
an explicit binding code (see Section 5.1.3.4), it is possible to
formalize this dependency relation, meaning that if the bound session
(e.g., session with SID_B) is terminated, the binding session (e.g.,
the session with SID_A) must be terminated also.
A message may include more than one BOUND-SESSION-ID object. This
may happen, e.g., in certain aggregation and bidirectional
reservation scenarios, where an end-to-end session has a
unidirectional dependency relation with an aggregate session and at
the same time it has a unidirectional dependency relation with
another session used for the reverse path.
3.2.9. Message Binding
QoS NSLP supports binding of messages in order to allow for
expressing dependencies between different messages. The message
binding can indicate either a unidirectional or bidirectional
dependency relation between two messages by including the MSG-ID
object in one message ("binding message") and the BOUND-MSG-ID object
in the other message ("bound message"). The unidirectional
dependency means that only RESERVE messages are bound to each other
whereas a bidirectional dependency means that there is also a
dependency for the related RESPONSE messages. The message binding
can be used to speed up signaling by starting two signaling exchanges
simultaneously that are synchronized later by using message IDs.
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This can be used as an optimization technique, for example, in
scenarios where aggregate reservations are used. Section 4.6
provides more details.
3.2.10. Layering
The QoS NSLP supports layered reservations. Layered reservations may
occur when certain parts of the network (domains) implement one or
more local QoS models or when they locally apply specific transport
characteristics (e.g., GIST unreliable transfer mode instead of
reliable transfer mode). They may also occur when several per-flow
reservations are locally combined into an aggregate reservation.
3.2.10.1. Local QoS Models
A domain may have local policies regarding QoS model implementation,
i.e., it may map incoming traffic to its own locally defined QoS
models. The QSPEC allows this functionality, and the operation is
transparent to the QoS NSLP. The use of local QoS models within a
domain is performed in the RMF.
3.2.10.2. Local Control Plane Properties
The way signaling messages are handled is mainly determined by the
parameters that are sent over the GIST-NSLP API and by the domain
internal configuration. A domain may have a policy to implement
local transport behavior. It may, for instance, elect to use an
unreliable transport locally in the domain while still keeping end-
to-end reliability intact.
The QoS NSLP supports this situation by allowing two sessions to be
set up for the same reservation. The local session has the desired
local transport properties and is interpreted in internal QNEs. This
solution poses two requirements: the end-to-end session must be able
to bypass intermediate nodes, and the egress QNE needs to bind both
sessions together. Bypassing intermediate nodes is achieved with
GIST. The local session and the end-to-end session are bound at the
egress QNE by means of the BOUND-SESSION-ID object.
3.2.10.3. Aggregate Reservations
In some cases, it is desirable to create reservations for an
aggregate, rather than on a per-flow basis, in order to reduce the
amount of reservation state needed as well as the processing load for
signaling messages. Note that the QoS NSLP does not specify how
reservations need to be combined in an aggregate or how end-to-end
properties need to be computed, but only provides signaling support
for aggregate reservations.
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The essential difference with the layering approaches described in
Sections 3.2.10.1 and 3.2.10.2 is that the aggregate reservation
needs a MRI that describes all traffic carried in the aggregate
(e.g., a DSCP in case of IntServ over Diffserv). The need for a
different MRI mandates the use of two different sessions, as
described in Section 3.2.10.2 and in the RSVP aggregation solution in
RFC 3175 [RFC3175].
Edge QNEs of the aggregation domain that want to maintain some end-
to-end properties may establish a peering relation by sending the
end-to-end message transparently over the domain (using the
intermediate node bypass capability described above). Updating the
end-to-end properties in this message may require some knowledge of
the aggregated session (e.g., for updating delay values). For this
purpose, the end-to-end session contains a BOUND-SESSION-ID carrying
the SESSION-ID of the aggregate session.
3.2.11. Support for Request Priorities
This specification acknowledges the fact that in some situations,
some messages or reservations may be more important than others, and
therefore it foresees mechanisms to give these messages or
reservations priority.
Priority of certain signaling messages over others may be required in
mobile scenarios when a message loss during call setup is less
harmful than during handover. This situation only occurs when GIST
or QoS NSLP processing is the congested part or scarce resource.
Priority of certain reservations over others may be required when QoS
resources are oversubscribed. In that case, existing reservations
may be preempted in order to make room for new higher-priority
reservations. A typical approach to deal with priority and
preemption is through the specification of a setup priority and
holding priority for each reservation. The Resource Management
Function at each QNE then keeps track of the resource consumption at
each priority level. Reservations are established when resources, at
their setup priority level, are still available. They may cause
preemption of reservations with a lower holding priority than their
setup priority.
Support of reservation priority is a QSPEC parameter and therefore
outside the scope of this specification. The GIST specification
provides a mechanism to support a number of levels of message
priority that can be requested over the NSLP-GIST API.
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3.2.12. Rerouting
The QoS NSLP needs to adapt to route changes in the data path. This
assumes the capability to detect rerouting events, create a QoS
reservation on the new path, and optionally tear down reservations on
the old path.
From an NSLP perspective, rerouting detection can be performed in two
ways. It can either come through NetworkNotification from GIST, or
from information seen at the NSLP. In the latter case, the QoS NSLP
node is able to detect changes in its QoS NSLP peers by keeping track
of a Source Identification Information (SII) handle that provides
information similar in nature to the RSVP_HOP object described in RFC
2205 [RFC2205]. When a RESERVE message with an existing SESSION-ID
and a different SII is received, the QNE knows its upstream or
downstream peer has changed, for sender-oriented and receiver-
oriented reservations, respectively.
Reservation on the new path happens when a RESERVE message arrives at
the QNE beyond the point where the old and new paths diverge. If the
QoS NSLP suspects that a reroute has occurred, then a full RESERVE
message (including the QSPEC) would be sent. A refreshing RESERVE
(with no QSPEC) will be identified as an error by a QNE on the new
path, which does not have the reservation installed (i.e., it was not
on the old path) or which previously had a different previous-hop
QNE. It will send back an error message that results in a full
RESERVE message being sent. Rapid recovery at the NSLP layer
therefore requires short refresh periods. Detection before the next
RESERVE message arrives is only possible at the IP layer or through
monitoring of GIST peering relations (e.g., by monitoring the Time to
Live (TTL), i.e., the number of GIST hops between NSLP peers, or
observing the changes in the outgoing interface towards GIST peer).
These mechanisms can provide implementation-specific optimizations
and are outside the scope of this specification.
When the QoS NSLP is aware of the route change, it needs to set up
the reservation on the new path. This is done by sending a new
RESERVE message. If the next QNE is in fact unchanged, then this
will be used to refresh/update the existing reservation. Otherwise,
it will lead to the reservation being installed on the new path.
Note that the operation for a receiver-initiated reservation session
differs a bit from the above description. If the routing changes in
the middle of the path, at some point (i.e., the divergence point)
the QNE that notices that its downstream path has changed (indicated
by a NetworkNotification from GIST), and it must send a QUERY with
the R-flag downstream. The QUERY will be processed as above, and at
some point hits a QNE for which the path downstream towards the QNI
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remains (i.e., the convergence point). This node must then send a
full RESERVE upstream to set up the reservation state along the new
path. It should not send the QUERY further downstream, since this
would have no real use. Similarly, when the QNE that sent the QUERY
receives the RESERVE, it should not send the RESERVE further
upstream.
After the reservation on the new path is set up, the branching node
may want to tear down the reservation on the old path (sooner than
would result from normal soft-state timeout). This functionality is
supported by keeping track of the old SII-Handle provided over the
GIST API. This handle can be used by the QoS NSLP to route messages
explicitly to the next node.
If the old path is downstream, the QNE can send a tearing RESERVE
using the old SII-Handle. If the old path is upstream, the QNE can
send a NOTIFY with the code for "Route Change". This is forwarded
upstream until it hits a QNE that can issue a tearing RESERVE
downstream. A separate document discusses in detail the effect of
mobility on the QoS NSLP signaling [NSIS-MOB].
A QNI or a branch node may wish to keep the reservation on the old
branch. For instance, this could be the case when a mobile node has
experienced a mobility event and wishes to keep reservation to its
old attachment point in case it moves back there. For this purpose,
a REPLACE flag is provided in the QoS NSLP common header, which, when
not set, indicates that the reservation on the old branch should be
kept.
Note that keeping old reservations affects the resources available to
other nodes. Thus, the operator of the access network must make the
final decision on whether this behavior is allowed. Also, the QNEs
in the access network may add this flag even if the mobile node has
not used the flag initially.
The latency in detecting that a new downstream peer exists or that
truncation has happened depends on GIST. The default QUERY message
transmission interval is 30 seconds. More details on how NSLPs are
able to affect the discovery of new peers or rerouting can be found
in the GIST specification.
3.2.12.1. Last Node Behavior
The design of the QoS NSLP allows reservations to be installed at a
subset of the nodes along a path. In particular, usage scenarios
include cases where the data flow endpoints do not support the QoS
NSLP.
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In the case where the data flow receiver does not support the QoS
NSLP, some particular considerations must be given to node discovery
and rerouting at the end of the signaling path.
There are three cases for the last node on the signaling path:
1) the last node is the data receiver,
2) the last node is a configured proxy for the data receiver, or
3) the last node is not the data receiver and is not explicitly
configured to act as a signaling proxy on behalf of the data
receiver.
Cases (1) and (2) can be handled by the QoS NSLP itself during the
initial path setup, since the QNE knows that it should terminate the
signaling. Case (3) requires some assistance from GIST, which
provides messages across the API to indicate that no further GIST
nodes that support QoS NSLP are present downstream, and that probing
of the downstream route change needs to continue once the reservation
is installed to detect any changes in this situation.
Two particular scenarios need to be considered in this third case.
In the first, referred to as "Path Extension", rerouting occurs such
that an additional QNE is inserted into the signaling path between
the old last node and the data receiver, as shown in Figure 4.
/-------\ Initial route
/ v
/-\
/--|B|--\ +-+
/ \-/ \ |x| = QoS NSLP aware
+-+ /-\ +-+
----|A| |D|
+-+ \-/ /-\
\ +-+ / |x| = QoS NSLP unaware
\--|C|--/ \-/
+-+
\ ^
\-------/ Updated route
Figure 4: Path Extension
When rerouting occurs, the data path changes from A-B-D to A-C-D.
Initially the signaling path ends at A. Despite initially being the
last node, node A needs to continue to attempt to send messages
downstream to probe for path changes, unless it has been explicitly
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configured as a signaling proxy for the data flow receiver. This is
required so that the signaling path change is detected, and C will
become the new last QNE.
In a second case, referred to as "Path Truncation", rerouting occurs
such that the QNE that was the last node on the signaling path is no
longer on the data path. This is shown in Figure 5.
/-------\ Initial route
/ v
+-+
/--|B|--\ +-+
/ +-+ \ |x| = QoS NSLP aware
+-+ /-\ +-+
----|A| |D|
+-+ \-/ /-\
\ /-\ / |x| = QoS NSLP unaware
\--|C|--/ \-/
\-/
\ ^
\-------/ Updated route
Figure 5: Path Truncation
When rerouting occurs, the data path again changes from A-B-D to
A-C-D. The signaling path initially ends at B, but this node is not
on the new path. In this case, the normal GIST path change detection
procedures at A will detect the path change and notify the QoS NSLP.
GIST will also notify the signaling application that no downstream
GIST nodes supporting the QoS NSLP are present. Node A will take
over as the last node on the signaling path.
3.2.12.2. Handling Spurious Route Change Notifications
The QoS NSLP is notified by GIST (with the NetworkNotification
primitive) when GIST believes that a rerouting event may have
occurred. In some cases, events that are detected as possible route
changes will turn out not to be. The QoS NSLP will not always be
able to detect this, even after receiving messages from the 'new'
peer.
As part of the RecvMessage API primitive, GIST provides an SII-Handle
that can be used by the NSLP to direct a signaling message to a
particular peer. The current SII-Handle will change if the signaling
peer changes. However, it is not guaranteed to remain the same after
a rerouting event where the peer does not change. Therefore, the QoS
NSLP mechanism for reservation maintenance after a route change
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includes robustness mechanisms to avoid accidentally tearing down a
reservation in situations where the peer QNE has remained the same
after a 'route change' notification from GIST.
A simple example that illustrates the problem is shown in Figure 6
below.
(1) +-+
/-----\ |x| = QoS NSLP aware
+-+ /-\ (3) +-+ +-+
----|A| |B|-----|C|----
+-+ \-/ +-+ /-\
\-----/ |x| = QoS NSLP unaware
(2) \-/
Figure 6: Spurious Reroute Alerting
In this example, the initial route A-B-C uses links (1) and (3).
After link (1) fails, the path is rerouted using links (2) and (3).
The set of QNEs along the path is unchanged (it is A-C in both cases,
since B does not support the QoS NSLP).
When the outgoing interface at A has changes, GIST may signal across
its API to the NSLP with a NetworkNotification. The QoS NSLP at A
will then attempt to repair the path by installing the reservation on
the path (2),(3). In this case, however, the old and new paths are
the same.
To install the new reservation, A will send a RESERVE message, which
GIST will transport to C (discovering the new next peer as
appropriate). The RESERVE also requests a RESPONSE from the QNR.
When this RESERVE message is received through the RecvMessage API
call from GIST at the QoS NSLP at C, the SII-Handle will be unchanged
from its previous communications from A.
A RESPONSE message will be sent by the QNR, and be forwarded from C
to A. This confirms that the reservation was installed on the new
path. The SII-Handle passed with the RecvMessage call from GIST to
the QoS NSLP will be different to that seen previously, since the
interface being used on A has changed.
At this point, A can attempt to tear down the reservation on the old
path. The RESERVE message with the TEAR flag set is sent down the
old path by using the GIST explicit routing mechanism and specifying
the SII-Handle relating to the 'old' peer QNE.
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If RSNs were being incremented for each of these RESERVE and RESERVE-
with-TEAR messages, the reservation would be torn down at C and any
QNEs further along the path. To avoid this, the RSN is used in a
special way. The RESERVE down the new path is sent with the new
current RSN set to the old RSN plus 2. The RESERVE-with-TEAR down
the old path is sent with an RSN set to the new current RSN minus 1.
This is the peer from which it was receiving RESERVE messages (see
for more details).
3.2.13. Preemption
The QoS NSLP provides building blocks to implement preemption. This
specification does not define how preemption should work, but only
provides signaling mechanisms that can be used by QoS models. For
example, an INFO-SPEC object can be added to messages to indicate
that the signaled session was preempted. A BOUND-SESSION-ID object
can carry the Session ID of the flow that caused the preemption of
the signaled session. How these are used by QoS models is out of
scope of the QoS NSLP specification.
3.3. GIST Interactions
The QoS NSLP uses GIST for delivery of all its messages. Messages
are passed from the NSLP to GIST via an API (defined in Appendix B of
[RFC5971]), which also specifies additional information, including an
identifier for the signaling application (e.g., 'QoS NSLP'), session
identifier, MRI, and an indication of the intended direction (towards
data sender or receiver). On reception, GIST provides the same
information to the QoS NSLP. In addition to the NSLP message data
itself, other meta-data (e.g., session identifier and MRI) can be
transferred across this interface.
The QoS NSLP keeps message and reservation state per session. A
session is identified by a Session Identifier (SESSION-ID). The
SESSION-ID is the primary index for stored NSLP state and needs to be
constant and unique (with a sufficiently high probability) along a
path through the network. The QoS NSLP picks a value for Session-ID.
This value is subsequently used by GIST and the QoS NSLP to refer to
this session.
Currently, the QoS NSLP specification considers mainly the path-
coupled MRM. However, extensions may specify how other types of MRMs
may be applied in combination with the QoS NSLP.
When GIST passes the QoS NSLP data to the NSLP for processing, it
must also indicate the value of the 'D' (Direction) flag for that
message in the MRI.
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The QoS NSLP does not provide any method of interacting with
firewalls or Network Address Translators (NATs). It assumes that a
basic NAT traversal service is provided by GIST.
3.3.1. Support for Bypassing Intermediate Nodes
The QoS NSLP may want to restrict the handling of its messages to
specific nodes. This functionality is needed to support layering
(explained in Section 3.2.10), when only the edge QNEs of a domain
process the message. This requires a mechanism at the GIST level
(which can be invoked by the QoS NSLP) to bypass intermediate nodes
between the edges of the domain.
The intermediate nodes are bypassed using multiple levels of the
router alert option. In that case, internal routers are configured
to handle only certain levels of router alerts. This is accomplished
by marking this message at the ingress, i.e., modifying the QoS NSLP
default NSLPID value to an NSLPID predefined value (see Section 6.6).
The egress stops this marking process by reassigning the QoS NSLP
default NSLPID value to the original RESERVE message. The exact
operation of modifying the NSLPID must be specified in the relevant
QoS model specification.
3.3.2. Support for Peer Change Identification
There are several circumstances where it is necessary for a QNE to
identify the adjacent QNE peer, which is the source of a signaling
application message. For example, it may be to apply the policy that
"state can only be modified by messages from the node that created
it" or it might be that keeping track of peer identity is used as a
(fallback) mechanism for rerouting detection at the NSLP layer.
This functionality is implemented in the GIST service interface with
SII-handle. As shown in the above example, we assume the SII-
handling will support both its own SII and its peer's SII.
Keeping track of the SII of a certain reservation also provides a
means for the QoS NSLP to detect route changes. When a QNE receives
a RESERVE referring to existing state but with a different SII, it
knows that its upstream peer has changed. It can then use the old
SII to initiate a teardown along the old section of the path. This
functionality is supported in the GIST service interface when the
peer's SII (which is stored on message reception) is passed to GIST
upon message transmission.
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3.3.3. Support for Stateless Operation
Stateless or reduced-state QoS NSLP operation makes the most sense
when some nodes are able to operate in a stateless way at the GIST
level as well. Such nodes should not worry about keeping reverse
state, message fragmentation and reassembly (at GIST), congestion
control, or security associations. A stateless or reduced-state QNE
will be able to inform the underlying GIST of this situation. GIST
service interface supports this functionality with the Retain-State
attribute in the MessageReceived primitive.
3.3.4. Priority of Signaling Messages
The QoS NSLP will generate messages with a range of performance
requirements for GIST. These requirements may result from a
prioritization at the QoS NSLP (Section 3.2.11) or from the
responsiveness expected by certain applications supported by the QoS
NSLP. GIST service interface supports this with the 'priority'
transfer attribute.
3.3.5. Knowledge of Intermediate QoS-NSLP-Unaware Nodes
In some cases, it is useful to know that there are routers along the
path where QoS cannot be provided. The GIST service interface
supports this by keeping track of IP-TTL and Original-TTL in the
RecvMessage primitive. A difference between the two indicates the
number of QoS-NSLP-unaware nodes. In this case, the QNE that detects
this difference should set the "B" (BREAK) flag. If a QNE receives a
QUERY or RESERVE message with the BREAK flag set, and then generates
a QUERY, RESERVE, or RESPONSE message, it can set the BREAK flag in
those messages. There are however, situations where the egress QNE
in a local domain may have some other means to provide QoS [RFC5975].
For example, in a local domain that is aware of RMD-QOSM [RFC5977]
(or a similar QoS Model) and that uses either NTLP stateless nodes or
NSIS-unaware nodes, the end-to-end RESERVE or QUERY message bypasses
these NTLP stateless or NSIS-unaware nodes. However, the reservation
within the local domain can be signaled by the RMD-QOSM (or a similar
QoS Model). In such situations, the "B" (BREAK) flag in the end-to-
end RESERVE or QUERY message should not be set by the edges of the
local domain.
4. Examples of QoS NSLP Operation
The QoS NSLP can be used in a number of ways. The examples here give
an indication of some of the basic processing. However, they are not
exhaustive and do not attempt to cover the details of the protocol
processing.
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4.1. Sender-Initiated Reservation
QNI QNE QNE QNR
| | | |
| RESERVE | | |
+--------->| | |
| | RESERVE | |
| +--------->| |
| | | RESERVE |
| | +--------->|
| | | |
| | | RESPONSE |
| | |<---------+
| | RESPONSE | |
| |<---------+ |
| RESPONSE | | |
|<---------+ | |
| | | |
| | | |
Figure 7: Basic Sender-Initiated Reservation
To make a new reservation, the QNI constructs a RESERVE message
containing a QSPEC object, from its chosen QoS model, that describes
the required QoS parameters.
The RESERVE message is passed to GIST, which transports it to the
next QNE. There, it is delivered to the QoS NSLP processing, which
examines the message. Policy control and admission control decisions
are made. The exact processing also takes into account the QoS model
being used. The node performs appropriate actions (e.g., installing
the reservation) based on the QSPEC object in the message.
The QoS NSLP then generates a new RESERVE message (usually based on
the one received). This is passed to GIST, which forwards it to the
next QNE.
The same processing is performed at further QNEs along the path, up
to the QNR. The determination that a node is the QNR may be made
directly (e.g., that node is the destination for the data flow), or
using GIST functionality to determine that there are no more QNEs
between this node and the data flow destination.
Any node may include a request for a RESPONSE in its RESERVE
messages. It does so by including a Request Identification
Information (RII) object in the RESERVE message. If the message
already includes an RII, an interested QNE must not add a new RII
object or replace the old RII object. Instead, it needs to remember
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the RII value so that it can match a RESPONSE message belonging to
the RESERVE. When it receives the RESPONSE, it forwards the RESPONSE
upstream towards the RII originating node.
In this example, the RESPONSE message is forwarded peer-to-peer along
the reverse of the path that the RESERVE message took (using GIST
path state), and so is seen by all the QNEs on this segment of the
path. It is only forwarded as far as the node that requested the
RESPONSE originally.
The reservation can subsequently be refreshed by sending further
RESERVE messages containing the complete reservation information, as
for the initial reservation. The reservation can also be modified in
the same way, by changing the QSPEC data to indicate a different set
of resources to reserve.
The overhead required to perform refreshes can be reduced, in a
similar way to that proposed for RSVP in RFC 2961 [RFC2961]. Once a
RESPONSE message has been received indicating the successful
installation of a reservation, subsequent refreshing RESERVE messages
can simply refer to the existing reservation, rather than including
the complete reservation specification.
4.2. Sending a Query
QUERY messages can be used to gather information from QNEs along the
path. For example, they can be used to find out what resources are
available before a reservation is made.
In order to perform a query along a path, the QNE constructs a QUERY
message. This message includes a QSPEC containing the actual query
to be performed at QNEs along the path. It also contains an RII
object used to match the response back to the query, and an indicator
of the query scope (next node, whole path, proxy). The QUERY message
is passed to GIST to forward it along the path.
A QNE receiving a QUERY message should inspect it and create a new
message based on it, with the query objects modified as required.
For example, the query may request information on whether a flow can
be admitted, and so a node processing the query might record the
available bandwidth. The new message is then passed to GIST for
further forwarding (unless it knows it is the QNR or is the limit for
the scope in the QUERY).
At the QNR, a RESPONSE message must be generated if the QUERY message
includes an RII object. Various objects from the received QUERY
message have to be copied into the RESPONSE message. It is then
passed to GIST to be forwarded peer-to-peer back along the path.
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Each QNE receiving the RESPONSE message should inspect the RII object
to see if it 'belongs' to it (i.e., it was the one that originally
created it). If it does not, then it simply passes the message back
to GIST to be forwarded upstream.
If there was an error in processing a RESERVE, instead of an RII, the
RESPONSE may carry an RSN. Thus, a QNE must also be prepared to look
for an RSN object if no RII was present, and act based on the error
code set in the INFO-SPEC of the RESPONSE.
4.3. Basic Receiver-Initiated Reservation
As described in the NSIS framework [RFC4080], in some signaling
applications, a node at one end of the data flow takes responsibility
for requesting special treatment -- such as a resource reservation --
from the network. Both ends then agree whether sender- or receiver-
initiated reservation is to be done. In case of a receiver-initiated
reservation, both ends agree whether a "One Pass With Advertising"
(OPWA) [opwa95] model is being used. This negotiation can be
accomplished using mechanisms that are outside the scope of NSIS.
To make a receiver-initiated reservation, the QNR constructs a QUERY
message, which MUST contain a QSPEC object from its chosen QoS model
(see Figure 8). The QUERY must have the RESERVE-INIT flag set. This
QUERY message does not need to trigger a RESPONSE message and
therefore, the QNI must not include the RII object (Section 5.4.2) in
the QUERY message. The QUERY message may be used to gather
information along the path, which is carried by the QSPEC object. An
example of such information is the "One Pass With Advertising" (OPWA)
model [opwa95]. This QUERY message causes GIST reverse-path state to
be installed.
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QNR QNE QNE QNI
sender receiver
| | | |
| QUERY | | |
+--------->| | |
| | QUERY | |
| +--------->| |
| | | QUERY |
| | +--------->|
| | | |
| | | RESERVE |
| | |<---------+
| | RESERVE | |
| |<---------+ |
| RESERVE | | |
|<---------+ | |
| | | |
| RESPONSE | | |
+--------->| | |
| | RESPONSE | |
| +--------->| |
| | | RESPONSE |
| | +--------->|
| | | |
Figure 8: Basic Receiver-Initiated Reservation
The QUERY message is transported by GIST to the next downstream QoS
NSLP node. There, it is delivered to the QoS NSLP processing, which
examines the message. The exact processing also takes into account
the QoS model being used and may include gathering information on
path characteristics that may be used to predict the end-to-end QoS.
The QNE generates a new QUERY message (usually based on the one
received). This is passed to GIST, which forwards it to the next
QNE. The same processing is performed at further QNEs along the
path, up to the flow receiver. The receiver detects that this QUERY
message carries the RESERVE-INIT flag and by using the information
contained in the received QUERY message, such as the QSPEC,
constructs a RESERVE message.
The RESERVE is forwarded peer-to-peer along the reverse of the path
that the QUERY message took (using GIST reverse-path state). Similar
to the sender-initiated approach, any node may include an RII in its
RESERVE messages. The RESPONSE is sent back to confirm that the
resources are set up. The reservation can subsequently be refreshed
with RESERVE messages in the upstream direction.
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4.4. Bidirectional Reservations
The term "bidirectional reservation" refers to two different cases
that are supported by this specification:
o Binding two sender-initiated reservations together, e.g., one
sender-initiated reservation from QNE A to QNE B and another one
from QNE B to QNE A (Figure 9).
o Binding a sender-initiated and a receiver-initiated reservation
together, e.g., a sender-initiated reservation from QNE A towards
QNE B, and a receiver-initiated reservation from QNE A towards QNE
B for the data flow in the opposite direction (from QNE B to QNE
A). This case is particularly useful when one end of the
communication has all required information to set up both sessions
(Figure 10).
Both ends have to agree on which bidirectional reservation type they
need to use. This negotiation can be accomplished using mechanisms
that are outside the scope of NSIS.
The scenario with two sender-initiated reservations is shown in
Figure 9. Note that RESERVE messages for both directions may visit
different QNEs along the path because of asymmetric routing. Both
directions of the flows are bound by inserting the BOUND-SESSION-ID
object at the QNI and QNR. RESPONSE messages are optional and not
shown in the picture for simplicity.
A QNE QNE B
| | FLOW-1 | |
|===============================>|
|RESERVE-1 | | |
QNI+--------->|RESERVE-1 | |
| +-------------------->|QNR
| | | |
| | FLOW-2 | |
|<===============================|
| | |RESERVE-2 |
| RESERVE-2 |<---------+QNI
QNR|<--------------------+ |
| | | |
Figure 9: Bidirectional Reservation for Sender+Sender Scenario
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The scenario with a sender-initiated and a receiver-initiated
reservation is shown in Figure 10. In this case, QNI A sends out two
RESERVE messages, one for the sender-initiated and one for the
receiver-initiated reservation. Note that the sequence of the two
RESERVE messages may be interleaved.
A QNE QNE B
| | FLOW-1 | |
|===============================>|
|RESERVE-1 | | |
QNI+--------->|RESERVE-1 | |
| +-------------------->|QNR
| | | |
| | FLOW-2 | |
|<===============================|
| | | QUERY-2 |
| | QUERY-2 |<---------+QNR
QNI|<--------------------+ |
| | | |
|RESERVE-2 | | |
QNI+--------->|RESERVE-2 | |
| +-------------------->|QNR
| | | |
Figure 10: Bidirectional Reservation for Sender+Receiver Scenario
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4.5. Aggregate Reservations
In order to reduce signaling and per-flow state in the network, the
reservations for a number of flows may be aggregated.
QNI QNE QNE/QNI' QNE' QNR'/QNE QNR
aggregator deaggregator
| | | | | |
| RESERVE | | | | |
+--------->| | | | |
| | RESERVE | | | |
| +--------->| | | |
| | | RESERVE | | |
| | +-------------------->| |
| | | RESERVE' | | |
| | +=========>| RESERVE' | |
| | | +=========>| RESERVE |
| | | | +--------->|
| | | | RESPONSE'| |
| | | RESPONSE'|<=========+ |
| | |<=========+ | |
| | | | | RESPONSE |
| | | | RESPONSE |<---------+
| | |<--------------------+ |
| | RESPONSE | | | |
| |<---------+ | | |
| RESPONSE | | | | |
|<---------+ | | | |
| | | | | |
| | | | | |
Figure 11: Sender-Initiated Reservation with Aggregation
An end-to-end per-flow reservation is initiated with the messages
shown in Figure 11 as "RESERVE".
At the aggregator, a reservation for the aggregated flow is initiated
(shown in Figure 11 as "RESERVE'"). This may use the same QoS model
as the end-to-end reservation but has an MRI identifying the
aggregated flow (e.g., tunnel) instead of for the individual flows.
This document does not specify how the QSPEC of the aggregate session
can be derived from the QSPECs of the end-to-end sessions.
The messages used for the signaling of the individual reservation
need to be marked such that the intermediate routers will not inspect
them. In the QoS NSLP, the following marking policy is applied; see
also RFC 3175.
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All routers use essentially the same algorithm for which messages
they process, i.e., all messages at aggregation level 0. However,
messages have their aggregation level incremented on entry to an
aggregation region and decremented on exit. In this technique, the
interior routers are not required to do any rewriting of the RAO
values. However, the aggregating/deaggregating routers must
distinguish the interfaces and associated aggregation levels. These
routers also perform message rewriting at these boundaries.
In particular, the Aggregator performs the marking by modifying the
QoS NSLP default NSLPID value to an NSLPID predefined value; see
Section 6.6. A RAO value is then uniquely derivable from each
predefined NSLPID. However, the RAO does not have to have a one-to-
one relation to a specific NSLPID.
Aggregator Deaggregator
+---+ +---+ +---+ +---+
|QNI|-----|QNE|-----|QNE|-----|QNR| aggregate
+---+ +---+ +---+ +---+ reservation
+---+ +---+ ..... ..... +---+ +---+
|QNI|-----|QNE|-----. .-----. .-----|QNE|-----|QNR| end-to-end
+---+ +---+ ..... ..... +---+ +---+ reservation
Figure 12: Reservation Aggregation
The deaggregator acts as the QNR for the aggregate reservation.
Session binding information carried in the RESERVE message enables
the deaggregator to associate the end-to-end and aggregate
reservations with one another (using the BOUND-SESSION-ID).
The key difference between this example and the one shown in
Section 4.7.1 is that the flow identifier for the aggregate is
expected to be different to that for the end-to-end reservation. The
aggregate reservation can be updated independently of the per-flow
end-to-end reservations.
4.6. Message Binding
Section 4.5 sketches the interaction of an aggregated end-to-end flow
and an aggregate. For this scenario, and probably others, it is
useful to have a method for synchronizing the exchanges of signaling
messages of different sessions. This can be used to speed up
signaling, because some message exchanges can be started
simultaneously and can be processed in parallel until further
processing of a message from one particular session depends on
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another message from a different session. For instance, Figure 11
shows a case where inclusion of a new reservation requires that the
capacity of the encompassing aggregate be increased first. So the
RESERVE (bound message) for the individual flow arriving at the
deaggregator should wait until the RESERVE' (binding message) for the
aggregate arrived successfully (otherwise, the individual flow cannot
be included in the existing aggregate and cannot be admitted).
Another alternative would be to increase the aggregate first and then
to reserve resources for a set of aggregated individual flows. In
this case, the binding and synchronization between the (RESERVE and
RESERVE') messages are not needed.
A message binding may be used (depending an the aggregators policy)
as follows: a QNE (aggregator QNI' in Figure 14) generates randomly a
128-bit MSG-ID (same rules apply as for generating a SESSION-ID) and
includes it as BOUND-MSG-ID object into the bound signaling message
(RESERVE (1) in Figure 13) that should wait for the arrival of a
related binding signaling message (RESERVE' (3) in Figure 13) that
carries the associated MSG-ID object. The BOUND-SESSION-ID should
also be set accordingly. Only one MSG-ID or BOUND-MSG-ID object per
message is allowed. If the dependency relation between the two
messages is bidirectional, then the Message_Binding_Type flag is SET
(value is 1). Otherwise, the Message_Binding_Type flag is UNSET. In
most cases, an RII object must be included in order to get a
corresponding RESPONSE back.
Depending on the arrival sequence of the bound signaling message
(RESERVE (1) in Figure 13) and the "triggering" binding signaling
message (RESERVE' (3) in Figure 13), different situations can be
identified:
o The bound signaling (RESERVE (1)) arrives first. The receiving
QNE enqueues (probably after some pre-processing) the signaling
(RESERVE (1)) message for the corresponding session. It also
starts a MsgIDWait timer in order to discard the message in case
the related "triggering" message (RESERVE' in Figure 13) does not
arrive. The timeout period for this time SHOULD be set to the
default retransmission timeout period (QOSNSLP_REQUEST_RETRY). In
case a retransmitted RESERVE message arrives before the timeout,
it will simply override the waiting message (i.e., the latter is
discarded, and the new message is now waiting with the MsgIDWait
timer being reset).
At the same time, the "triggering" message including a MSG-ID object,
carrying the same value as the BOUND-MSG-ID object is sent by the
same initiating QNE (QNI' in Figure 13). The intermediate QNE' sees
the MSG-ID object, but can determine that it is not the endpoint for
the session (QNR') and therefore simply forwards the message after
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normal processing. The receiving QNE (QNR') as endpoint for the
aggregate session (i.e., deaggregator) interprets the MSG-ID object
and looks for a corresponding waiting message with a BOUND-MSG-ID of
the same value whose waiting condition is satisfied now. Depending
on successful processing of the RESERVE' (3), processing of the
waiting RESERVE will be resumed, and the MsgIDWait timer will be
stopped as soon as the related RESERVE' arrived.
QNI QNE QNE/QNI' QNE' QNR'/QNE QNR
aggregator deaggregator
| | | | | |
| RESERVE | | | | |
+--------->| | | | |
| | RESERVE | | | |
| +--------->| | | |
| | | RESERVE | | |
| | | (1) | | |
| | +-------------------->| |
| | | RESERVE' | | |
| | | (2) | | |
| | +=========>| RESERVE' | |
| | | | (3) | |
| | | +=========>| RESERVE |
| | | | | (4) |
| | | | +--------->|
| | | | RESPONSE'| |
| | | RESPONSE'|<=========+ |
| | |<=========+ | |
| | | | | RESPONSE |
| | | | RESPONSE |<---------+
| | |<--------------------+ |
| | RESPONSE | | | |
| |<---------+ | | |
| RESPONSE | | | | |
|<---------+ | | | |
| | | | | |
| | | | | |
(1): RESERVE: SESSION-ID=F, BOUND-MSG-ID=x, BOUND-SESSION-ID=A
(2)+(3): RESERVE': SESSION-ID=A, MSG-ID=x
(4): RESERVE: SESSION-ID=F (MSG-ID object was removed)
Figure 13: Example for Using Message Binding
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Several further cases have to be considered in this context:
o "Triggering message" (3) arrives before waiting (bound) message
(1): In this case, the processing of the triggering message
depends on the value of the Message_Binding_Type flag. If
Message_Binding_Type is UNSET (value is 0), then the triggering
message can be processed normally, but the MSG-ID and the result
(success or failure) should be saved for the waiting message.
Thus, the RESPONSE' can be sent by the QNR' immediately. If the
waiting message (1) finally arrives at the QNR', it can be
detected that the waiting condition was already satisfied because
the triggering message already arrived earlier. If
Message_Binding_Type is SET (value is 1), then the triggering
message interprets the MSG-ID object and looks for the
corresponding waiting message with a BOUND-MSG-ID of the same
value, which in this case has not yet arrived. It then starts a
MsgIDWait timer in order to discard the message in case the
related message (RESERVE (1) in Figure 14) does not arrive.
Depending on successful processing of the RESERVE (1), processing
of the waiting RESERVE' will be resumed, the MsgIDWait timer will
be stopped as soon as the related RESERVE arrives and the
RESPONSE' can be sent by the QNR' towards the QNI'.
o The "triggering message" (3) does not arrive at all: this may be
due to message loss (which will cause a retransmission by the QNI'
if the RII object is included) or due to a reservation failure at
an intermediate node (QNE' in the example). The MsgIDWait timeout
will then simply discard the waiting message at QNR'. In this
case, the QNR' MAY send a RESPONSE message towards the QNI
informing it that the synchronization of the two messages has
failed.
o Retransmissions should use the same MSG-ID because usually only
one of the two related messages is retransmitted. As mentioned
above: retransmissions will only occur if the RII object is set in
the RESERVE. If a retransmitted message with a MSG-ID arrives
while a bound message with the same MSG-ID is still waiting, the
retransmitted message will replace the bound message.
For a receiving node, there are conceptually two lists indexed by
message IDs. One list contains the IDs and results of triggering
messages (those carrying a MSG-ID object), the other list contains
the IDs and message contents of the bound waiting messages (those who
carried a BOUND-MSG-ID). The former list is used when a triggering
message arrives before the bound message. The latter list is used
when a bound message arrives before a triggering message.
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4.7. Reduced-State or Stateless Interior Nodes
This example uses a different QoS model within a domain, in
conjunction with GIST and NSLP functionality that allows the interior
nodes to avoid storing GIST and QoS NSLP state. As a result, the
interior nodes only store the QSPEC-related reservation state or even
no state at all. This allows the QoS model to use a form of
"reduced-state" operation, where reservation states with a coarser
granularity (e.g., per-class) are used, or a "stateless" operation
where no QoS NSLP state is needed (or created). This is useful,
e.g., for measurement-based admission control schemes.
The key difference between this example and the use of different QoS
models in Section 4.5 is the transport characteristics for the
reservation, i.e., GIST can be used in a different way for the edge-
to-edge and hop-by-hop sessions. The reduced-state reservation can
be updated independently of the per-flow end-to-end reservations.
4.7.1. Sender-Initiated Reservation
The QNI initiates a RESERVE message (see Figure 14). At the QNEs on
the edges of the stateless or reduced-state region, the processing is
different and the nodes support two QoS models. At the ingress, the
original RESERVE message is forwarded but ignored by the stateless or
reduced-state nodes. This is accomplished by marking this message at
the ingress, i.e., modifying the QoS NSLP default NSLPID value to an
NSLPID predefined value (see Section 4.6). The egress must reassign
the QoS NSLP default NSLPID value to the original end-to-end RESERVE
message. An example of such operation is given in [RFC5977].
The egress node is the next QoS-NSLP hop for the end-to-end RESERVE
message. Reliable GIST transfer mode can be used between the ingress
and egress without requiring GIST state in the interior. At the
egress node, the RESERVE message is then forwarded normally.
At the ingress, a second RESERVE' message is also built (Figure 14).
This makes use of a QoS model suitable for a reduced-state or
stateless form of operation (such as the RMD per-hop reservation).
Since the original RESERVE and the RESERVE' messages are addressed
identically, the RESERVE' message also arrives at the same egress QNE
that was also traversed by the RESERVE message. Message binding is
used to synchronize the messages.
When processed by interior (stateless) nodes, the QoS NSLP processing
exercises its options to not keep state wherever possible, so that no
per-flow QoS NSLP state is stored. Some state, e.g., per class, for
the QSPEC-related data may be held at these interior nodes. The QoS
NSLP also requests that GIST use different transport characteristics
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(e.g., sending of messages in unreliable GIST transfer mode). It
also requests the local GIST processing not to retain messaging
association state or reverse message routing state.
Nodes, such as those in the interior of the stateless or reduced-
state domain, that do not retain reservation state cannot send back
RESPONSE messages (and so cannot use the refresh reduction
extension).
At the egress node, the RESERVE' message is interpreted in
conjunction with the reservation state from the end-to-end RESERVE
message (using information carried in the message to correlate the
signaling flows). The RESERVE message is only forwarded further if
the processing of the RESERVE' message was successful at all nodes in
the local domain; otherwise, the end-to-end reservation is regarded
as having failed to be installed. This can be realized by using the
message binding functionality described in Section 4.6 to synchronize
the arrival of the bound signaling message (end-to-end RESERVE) and
the binding signaling message (local RESERVE').
QNE QNE QNE QNE
ingress interior interior egress
GIST stateful GIST stateless GIST stateless GIST stateful
| A B |
RESERVE | | | |
-------->| RESERVE | | |
+--------------------------------------------->|
| RESERVE' | | |
+-------------->| | |
| | RESERVE' | |
| +-------------->| |
| | | RESERVE' |
| | +------------->|
| | | RESPONSE' |
|<---------------------------------------------+
| | | | RESERVE
| | | +-------->
| | | | RESPONSE
| | | |<--------
| | | RESPONSE |
|<---------------------------------------------+
RESPONSE| | | |
<--------| | | |
Figure 14: Sender-Initiated Reservation with Reduced-State Interior
Nodes
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Resource management errors in the example above are reflected in the
QSPEC and QoS model processing. For example, if the RESERVE' fails
at QNE A, it cannot send an error message back to the ingress QNE.
Thus, the RESERVE' is forwarded along the intended path, but the
QSPEC includes information for subsequent QNEs telling them an error
happened upstream. It is up to the QoS model to determine what to
do. Eventually, the RESERVE' will reach the egress QNE, and again,
the QoS model then determines the response.
4.7.2. Receiver-Initiated Reservation
Since NSLP neighbor relationships are not maintained in the reduced-
state region, only sender-initiated signaling can be supported within
the reduced-state region. If a receiver-initiated reservation over a
stateless or reduced-state domain is required, this can be
implemented as shown in Figure 15.
QNE QNE QNE
ingress interior egress
GIST stateful GIST stateless GIST stateful
| | |
QUERY | | |
-------->| QUERY | |
+------------------------------>|
| | | QUERY
| | +-------->
| | | RESERVE
| | |<--------
| | RESERVE |
|<------------------------------+
| RESERVE' | RESERVE' |
|-------------->|-------------->|
| | RESPONSE' |
|<------------------------------+
RESERVE | | |
<--------| | |
Figure 15: Receiver-Initiated Reservation with Reduced-State Interior
Nodes
The RESERVE message that is received by the egress QNE of the
stateless domain is sent transparently to the ingress QNE (known as
the source of the QUERY message). When the RESERVE message reaches
the ingress, the ingress QNE needs to send a sender-initiated
RESERVE' over the stateless domain. The ingress QNE needs to wait
for a RESPONSE'. If the RESPONSE' notifies that the reservation was
accomplished successfully, then the ingress QNE sends a RESERVE
message further upstream.
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4.8. Proxy Mode
Besides the sender- and receiver-initiated reservations, the QoS NSLP
includes a functionality we refer to as Proxy Mode. Here a QNE is
set by administrator assignment to work as a proxy QNE (P-QNE) for a
certain region, e.g., for an administrative domain. A node
initiating the signaling may set the PROXY scope flag to indicate
that the signaling is meant to be confined within the area controlled
by the proxy, e.g., the local access network.
The Proxy Mode has two uses. First, it allows the QoS NSLP signaling
to be confined to a pre-defined section of the path. Second, it
allows a node to make reservations for an incoming data flow.
For outgoing data flows and sender-initiated reservations, the end
host is the QNI, and sends a RESERVE with the PROXY scope flag set.
The P-QNE is the QNR; it will receive the RESERVE, notice the PROXY
scope flag is set and reply with a RESPONSE (if requested). This
operation is the same as illustrated in Figure 7. The receiver-
oriented reservation for outgoing flows works the same way as in
Figure 8, except that the P-QNE is the QNI.
For incoming data flows, the end host is the QNI, and it sends a
RESERVE towards the data sender with the PROXY scope flag set. Here
the end host sets the MRI so that it indicates the end host as the
receiver of the data, and sets the D-flag.
GIST is able to send messages towards the data sender if there is
existing message routing state or it is able to use the Upstream
Q-mode Encapsulation. In some cases, GIST will be unable to
determine the appropriate next hop for the message, and so will
indicate a failure to deliver it (by sending an error message). This
may occur, for example, if GIST attempts to determine an upstream
next hop and there are multiple possible inbound routes that could be
used.
Bidirectional reservations can be used, as discussed in Section 4.4.
The P-QNE will be the QNR or QNI for reservations.
If the PROXY scope flag is set in an incoming QoS NSLP message, the
QNE must set the same flag in all QoS NSLP messages it sends that are
related to this session.
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5. QoS NSLP Functional Specification
5.1. QoS NSLP Message and Object Formats
A QoS NSLP message consists of a common header, followed by a body
consisting of a variable number of variable-length, typed "objects".
The common header and other objects are encapsulated together in a
GIST NSLP-Data object. The following subsections define the formats
of the common header and each of the QoS NSLP message types. In the
message formats, the common header is denoted as COMMON-HEADER.
For each QoS NSLP message type, there is a set of rules for the
permissible choice of object types. These rules are specified using
the Augmented Backus-Naur Form (ABNF) specified in RFC 5234
[RFC5234]. The ABNF implies an order for the objects in a message.
However, in many (but not all) cases, object order makes no logical
difference. An implementation SHOULD create messages with the
objects in the order shown here, but MUST accept the objects in any
order.
5.1.1. Common Header
All GIST NSLP-Data objects for the QoS NSLP MUST contain this common
header as the first 32 bits of the object (this is not the same as
the GIST Common Header).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Message Flags | Generic Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the common header are as follows:
Msg Type: 8 bits
1 = RESERVE
2 = QUERY
3 = RESPONSE
4 = NOTIFY
Message-specific flags: 8 bits
These flags are defined as part of the specification of individual
messages, and, thus, are different with each message type.
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Generic flags: 16 bits
Generic flags have the same meaning for all message types. There
exist currently four generic flags: the (next hop) Scoping flag
(S), the Proxy scope flag (P), the Acknowledgement Requested flag
(A), and the Break flag (B).
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |B|A|P|S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
SCOPING (S) - when set, indicates that the message is scoped and
should not travel down the entire path but only as far as the next
QNE (scope="next hop"). By default, this flag is not set (default
scope="whole path").
PROXY (P) - when set, indicates that the message is scoped, and
should not travel down the entire path but only as far as the P-QNE.
By default, this flag is not set.
ACK-REQ (A) - when set, indicates that the message should be
acknowledged by the receiving peer. The flag is only used between
stateful peers, and only used with RESERVE and QUERY messages.
Currently, the flag is only used with refresh messages. By default,
the flag is not set.
BREAK (B) - when set, indicates that there are routers along the path
where QoS cannot be provided.
The set of appropriate flags depends on the particular message being
processed. Any bit not defined as a flag for a particular message
MUST be set to zero on sending and MUST be ignored on receiving.
The ACK-REQ flag is useful when a QNE wants to make sure the messages
received by the downstream QNE are truly processed by the QoS NSLP,
not just delivered by GIST. This is useful for faster dead peer
detection on the NSLP layer. This liveliness test can only be used
with refresh RESERVE messages. The ACK-REQ flag must not be set for
RESERVE messages that already include an RII object, since a
confirmation has already been requested from the QNR. Reliable
transmission of messages between two QoS NSLP peers should be handled
by GIST, not the NSLP by itself.
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5.1.2. Message Formats
5.1.2.1. RESERVE
The format of a RESERVE message is as follows:
RESERVE = COMMON-HEADER
RSN [ RII ] [ REFRESH-PERIOD ] [ *BOUND-SESSION-ID ]
[ SESSION-ID-LIST [ RSN-LIST ] ]
[ MSG-ID / BOUND-MSG-ID ] [ INFO-SPEC ]
[ [ PACKET-CLASSIFIER ] QSPEC ]
The RSN is the only mandatory object and MUST always be present in
all cases. A QSPEC MUST be included in the initial RESERVE sent
towards the QNR. A PACKET-CLASSIFIER MAY be provided. If the
PACKET-CLASSIFIER is not provided, then the full set of information
provided in the GIST MRI for the session should be used for packet
classification purposes.
Subsequent RESERVE messages meant as reduced refreshes, where no
QSPEC is provided, MUST NOT include a PACKET-CLASSIFIER either.
There are no requirements on transmission order, although the above
order is recommended.
Two message-specific flags are defined for use in the common header
with the RESERVE message. These are:
+-+-+-+-+-+-+-+-+
|Reserved |T|R|
+-+-+-+-+-+-+-+-+
TEAR (T) - when set, indicates that reservation state and QoS NSLP
operation state should be torn down. The former is indicated to the
RMF. Depending on the QoS model, the tear message may include a
QSPEC to further specify state removal, e.g., for an aggregation, the
QSPEC may specify the amount of resources to be removed from the
aggregate.
REPLACE (R) - when set, the flag has two uses. First, it indicates
that a RESERVE with different MRI (but same SID) replaces an existing
one, so the old one MAY be torn down immediately. This is the
default situation. This flag may be unset to indicate a desire from
an upstream node to keep an existing reservation on an old branch in
place. Second, this flag is also used to indicate whether the
reserved resources on the old branch should be torn down or not when
a data path change happens. In this case, the MRI is the same and
only the route path changes.
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If the REFRESH-PERIOD is not present, a default value of 30 seconds
is assumed.
If the session of this message is bound to another session, then the
RESERVE message MUST include the SESSION-ID of that other session in
a BOUND-SESSION-ID object. In the situation of aggregated tunnels,
the aggregated session MAY not include the SESSION-ID of its bound
sessions in BOUND-SESSION-ID(s).
The negotiation of whether to perform sender- or receiver-initiated
signaling is done outside the QoS NSLP. Yet, in theory, it is
possible that a "reservation collision" may occur if the sender
believes that a sender-initiated reservation should be performed for
a flow, whilst the other end believes that it should be starting a
receiver-initiated reservation. If different session identifiers are
used, then this error condition is transparent to the QoS NSLP,
though it may result in an error from the RMF. Otherwise, the
removal of the duplicate reservation is left to the QNIs/QNRs for the
two sessions.
If a reservation is already installed and a RESERVE message is
received with the same session identifier from the other direction
(i.e., going upstream where the reservation was installed by a
downstream RESERVE message, or vice versa), then an error indicating
"RESERVE received from wrong direction" MUST be sent in a RESPONSE
message to the signaling message source for this second RESERVE.
A refresh right along the path can be forced by requesting a RESPONSE
from the far end (i.e., by including an RII object in the RESERVE
message). Without this, a refresh RESERVE would not trigger RESERVE
messages to be sent further along the path, as each hop has its own
refresh timer.
A QNE may ask for confirmation of a tear operation by including an
RII object. QoS NSLP retransmissions SHOULD be disabled. A QNE
sending a tearing RESERVE with an RII included MAY ask GIST to use
reliable transport. When the QNE sends out a tearing RESERVE, it
MUST NOT send refresh messages anymore.
If the routing path changed due to mobility and the mobile node's IP
address changed, and it sent a Mobile IP binding update, the
resulting refresh is a new RESERVE. This RESERVE includes a new MRI
and will be propagated end-to-end; there is no need to force end-to-
end forwarding by including an RII.
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Note: It is possible for a host to use this mechanism to constantly
force the QNEs on the path to send refreshing RESERVE messages. It
may, therefore, be appropriate for QNEs to perform rate-limiting on
the refresh messages that they send.
5.1.2.2. QUERY
The format of a QUERY message is as follows:
QUERY = COMMON-HEADER
[ RII ] [ *BOUND-SESSION-ID ]
[ PACKET-CLASSIFIER ] [ INFO-SPEC ] QSPEC [ QSPEC ]
QUERY messages MUST always include a QSPEC. QUERY messages MAY
include a PACKET-CLASSIFIER when the message is used to trigger a
receiver-initiated reservation. If a PACKET-CLASSIFIER is not
included then the full GIST MRI should be used for packet
classification purposes in the subsequent RESERVE. A QUERY message
MAY contain a second QSPEC object.
A QUERY message for requesting information about network resources
MUST contain an RII object to match an incoming RESPONSE to the
QUERY.
The QSPEC object describes what is being queried for and may contain
objects that gather information along the data path. There are no
requirements on transmission order, although the above order is
recommended.
One message-specific flag is defined for use in the common header
with the QUERY message. It is:
+-+-+-+-+-+-+-+-+
|Reserved |R|
+-+-+-+-+-+-+-+-+
RESERVE-INIT (R) - when this is set, the QUERY is meant as a trigger
for the recipient to make a resource reservation by sending a
RESERVE.
If the session of this message is bound to another session, then the
RESERVE message MUST include the SESSION-ID of that other session in
a BOUND-SESSION-ID object. In the situation of aggregated tunnels,
the aggregated session MAY not include the SESSION-ID of its bound
sessions in BOUND-SESSION-ID(s).
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5.1.2.3. RESPONSE
The format of a RESPONSE message is as follows:
RESPONSE = COMMON-HEADER
[ RII / RSN ] INFO-SPEC [SESSION-ID-LIST [ RSN-LIST ] ]
[ QSPEC ]
A RESPONSE message MUST contain an INFO-SPEC object that indicates
the success of a reservation installation or an error condition.
Depending on the value of the INFO-SPEC, the RESPONSE MAY also
contain a QSPEC object. The value of an RII or an RSN object was
provided by some previous QNE. There are no requirements on
transmission order, although the above order is recommended.
No message-specific flags are defined for use in the common header
with the RESPONSE message.
5.1.2.4. NOTIFY
The format of a NOTIFY message is as follows:
NOTIFY = COMMON-HEADER
INFO-SPEC [ QSPEC ]
A NOTIFY message MUST contain an INFO-SPEC object indicating the
reason for the notification. Depending on the INFO-SPEC value, it
MAY contain a QSPEC object providing additional information.
No message-specific flags are defined for use with the NOTIFY
message.
5.1.3. Object Formats
The QoS NSLP uses a Type-Length-Value (TLV) object format similar to
that used by GIST. Every object consists of one or more 32-bit words
with a one-word header. For convenience, the standard object header
is shown here:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|B|r|r| Type |r|r|r|r| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The value for the Type field comes from the shared NSLP object type
space; the various objects are presented in subsequent sections. The
Length field is given in units of 32-bit words and measures the
length of the Value component of the TLV object (i.e., it does not
include the standard header).
The bits marked 'A' and 'B' are flags used to signal the desired
treatment for objects whose treatment has not been defined in the
protocol specification (i.e., whose Type field is unknown at the
receiver). The following four categories of object have been
identified, and are described here.
AB=00 ("Mandatory"): If the object is not understood, the entire
message containing it MUST be rejected, and an error message sent
back.
AB=01 ("Ignore"): If the object is not understood, it MUST be
deleted and the rest of the message processed as usual.
AB=10 ("Forward"): If the object is not understood, it MUST be
retained unchanged in any message forwarded as a result of message
processing, but not stored locally.
AB=11 ("Refresh"): If the object is not understood, it should be
incorporated into the locally stored QoS NSLP signaling
application operational state for this flow/session, forwarded in
any resulting message, and also used in any refresh or repair
message that is generated locally. The contents of this object
does not need to be interpreted, and should only be stored as
bytes on the QNE.
The remaining bits marked 'r' are reserved. These SHALL be set to 0
and SHALL be ignored on reception. The extensibility flags AB are
similar to those used in the GIST specification. All objects defined
in this specification MUST be understood by all QNEs; thus, they MUST
have the AB-bits set to "00". A QoS NSLP implementation must
recognize objects of the following types: RII, RSN, REFRESH-PERIOD,
BOUND-SESSION-ID, INFO-SPEC, and QSPEC.
The object header is followed by the Value field, which varies for
different objects. The format of the Value field for currently
defined objects is specified below.
The object diagrams here use '//' to indicate a variable-sized field.
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5.1.3.1. Request Identification Information (RII)
Type: 0x001
Length: Fixed - 1 32-bit word
Value: An identifier that MUST be (probabilistically) unique within
the context of a SESSION-ID and SHOULD be different every time a
RESPONSE is desired. Used by a QNE to match back a RESPONSE to a
request in a RESERVE or QUERY message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Request Identification Information (RII) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.3.2. Reservation Sequence Number (RSN)
Type: 0x002
Length: Fixed - 2 32-bit words
Value: An incrementing sequence number that indicates the order in
which state-modifying actions are performed by a QNE, and an epoch
identifier to allow the identification of peer restarts. The RSN has
local significance only, i.e., between a QNE and its downstream
stateful peers. The RSN is not reset when the downstream peer
changes.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reservation Sequence Number (RSN) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Epoch Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.3.3. Refresh Period (REFRESH-PERIOD)
Type: 0x003
Length: Fixed - 1 32-bit word
Value: The refresh timeout period R used to generate this message; in
milliseconds.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh Period (R) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.3.4. Bound Session ID (BOUND-SESSION-ID)
Type: 0x004
Length: Fixed - 5 32-bit words
Value: contains an 8-bit Binding_Code that indicates the nature of
the binding. The rest specifies the SESSION-ID (as specified in GIST
[RFC5971]) of the session that MUST be bound to the session
associated with the message carrying this object.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Binding Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Session ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Currently defined Binding Codes are:
o 0x01 - Tunnel and end-to-end sessions
o 0x02 - Bidirectional sessions
o 0x03 - Aggregate sessions
o 0x04 - Dependent sessions (binding session is alive only if the
other session is also alive)
o 0x05 - Indicated session caused preemption
More binding codes may be defined based on the above five atomic
binding actions. Note a message may include more than one BOUND-
SESSION-ID object. This may be needed in case one needs to define
more specifically the reason for binding, or if the session depends
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on more than one other session (with possibly different reasons).
Note that a session with, e.g., SID_A (the binding session), can
express its unidirectional dependency relation to another session
with, e.g., SID_B (the bound session), by including a
BOUND-SESSION-ID object containing SID_B in its messages.
5.1.3.5. Packet Classifier (PACKET-CLASSIFIER)
Type: 0x005
Length: Variable
Value: Contains variable-length MRM-specific data
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Method-specific classifier data (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
At this stage, the QoS NSLP only uses the path-coupled routing MRM.
The method-specific classifier data is four bytes long and consists
of a set of flags:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X|Y|P|T|F|S|A|B| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The flags are:
X - Source Address and Prefix
Y - Destination Address and Prefix
P - Protocol
T - Diffserv Code Point
F - Flow Label
S - SPI
A - Source Port
B - Destination Port
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The flags indicate which fields from the MRI MUST be used by the
packet classifier. This allows a subset of the information in the
MRI to be used for identifying the set of packets that are part of
the reservation. Flags MUST only be set if the data is present in
the MRI (i.e., where there is a corresponding flag in the GIST MRI,
the flag can only be set if the corresponding GIST MRI flag is set).
It should be noted that some flags in the PACKET-CLASSIFIER (X and Y)
relate to data that is always present in the MRI, but are optional to
use for QoS NSLP packet classification. The appropriate set of flags
set may depend, to some extent, on the QoS model being used.
As mentioned earlier in this section, the QoS NSLP is currently only
defined for use with the Path-Coupled Message Routing Method (MRM) in
GIST. Future work may extend the QoS NSLP to additional routing
mechanisms. Such MRMs must include sufficient information in the MRI
to allow the subset of packets for which QoS is to be provided to be
identified. When QoS NSLP is extended to support a new MRM,
appropriate method-specific classifier data for the PACKET-CLASSIFIER
object MUST be defined.
5.1.3.6. Information Object (INFO-SPEC) and Error Codes
Type: 0x006
Length: Variable
Value: Contains 8 reserved bits, an 8-bit error code, a 4-bit error
class, a 4-bit error source identifier type, and an 8-bit error
source identifier length (in 32-bit words), an error source
identifier, and optionally variable-length error-specific
information.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Error Code |E-Class|ESI Typ| ESI-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Error Source Identifier //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional error-specific information //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Class Field:
The four E-Class bits of the object indicate the error severity
class. The currently defined error classes are:
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o 1 - Informational
o 2 - Success
o 3 - Protocol Error
o 4 - Transient Failure
o 5 - Permanent Failure
o 6 - QoS Model Error
Error field:
Within each error severity class, a number of Error Code values are
defined.
o Informational:
* 0x01 - Unknown BOUND-SESSION-ID: the message refers to an
unknown SESSION-ID in its BOUND-SESSION-ID object.
* 0x02 - Route Change: possible route change occurred on
downstream path.
* 0x03 - Reduced refreshes not supported; full QSPEC required.
* 0x04 - Congestion situation: Possible congestion situation
occurred on downstream path.
* 0x05 - Unknown SESSION-ID in SESSION-ID-LIST.
* 0x06 - Mismatching RSN in RSN-LIST.
o Success:
* 0x01 - Reservation successful
* 0x02 - Teardown successful
* 0x03 - Acknowledgement
* 0x04 - Refresh successful
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o Protocol Error:
* 0x01 - Illegal message type: the type given in the Message
Type field of the common header is unknown.
* 0x02 - Wrong message length: the length given for the message
does not match the length of the message data.
* 0x03 - Bad flags value: an undefined flag or combination of
flags was set in the generic flags.
* 0x04 - Bad flags value: an undefined flag or combination of
flags was set in the message-specific flags.
* 0x05 - Mandatory object missing: an object required in a
message of this type was missing.
* 0x06 - Illegal object present: an object was present that must
not be used in a message of this type.
* 0x07 - Unknown object present: an object of an unknown type
was present in the message.
* 0x08 - Wrong object length: the length given for the object
did not match the length of the object data present.
* 0x09 - RESERVE received from wrong direction.
* 0x0a - Unknown object field value: a field in an object had an
unknown value.
* 0x0b - Duplicate object present.
* 0x0c - Malformed QSPEC.
* 0x0d - Unknown MRI.
* 0x0e - Erroneous value in the TLV object's value field.
* 0x0f - Incompatible QSPEC.
o Transient Failure:
* 0x01 - No GIST reverse-path forwarding state
* 0x02 - No path state for RESERVE, when doing a receiver-
oriented reservation
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* 0x03 - RII conflict
* 0x04 - Full QSPEC required
* 0x05 - Mismatch synchronization between end-to-end RESERVE and
intra-domain RESERVE
* 0x06 - Reservation preempted
* 0x07 - Reservation failure
* 0x08 - Path truncated - Next peer dead
o Permanent Failure:
* 0x01 - Internal or system error
* 0x02 - Authorization failure
o QoS Model Error:
This error class can be used by QoS models to add error codes
specific to the QoS model being used. All these errors and events
are created outside the QoS NSLP itself. The error codes in this
class are defined in QoS model specifications. Note that this
error class may also include codes that are not purely errors, but
rather some non-fatal information.
Error Source Identifier (ESI)
The Error Source Identifier is for diagnostic purposes and its
inclusion is OPTIONAL. It is suggested that implementations use this
for the IP address, host name, or other identifier of the QNE
generating the INFO-SPEC to aid diagnostic activities. A QNE SHOULD
NOT be used in any purpose other than error logging or being
presented to the user as part of any diagnostic information. A QNE
SHOULD NOT attempt to send a message to that address.
If no Error Source Identifier is included, the Error Source
Identifier Type field must be zero.
Currently three Error Source Identifiers have been defined: IPv4,
IPv6, and FQDN.
Error Source Identifier: IPv4
Error Source Identifier Type: 0x1
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32-bit IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Error Source Identifier: IPv6
Error Source Identifier Type: 0x2
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ 128-bit IPv6 address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Error Source Identifier: FQDN in UTF-8
Error Source Identifier Type: 0x3
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// FQDN //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If the length of the FQDN is not a multiple of 32-bits, the field is
padded with zero octets to the next 32-bit boundary.
If a QNE encounters protocol errors, it MAY include additional
information, mainly for diagnostic purposes. Additional information
MAY be included if the type of an object is erroneous, or a field has
an erroneous value.
If the type of an object is erroneous, the following optional error-
specific information may be included at the end of the INFO-SPEC.
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Object Type Info:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Object Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This object provides information about the type of object that caused
the error.
If a field in an object had an incorrect value, the following
Optional error-specific information may be added at the end of the
INFO-SPEC.
Object Value Info:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rsvd | Real Object Length | Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Object //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Real Object Length: Since the length in the original TLV header may
be inaccurate, this field provides the actual length of the object
(including the TLV Header) included in the error message.
Offset: Indicates which part of the erroneous object is included.
When this field is set to "0", the complete object is included. If
Offset is bigger than "0", the erroneous object from offset
(calculated from the beginning of the object) to the end of the
object is included.
Object: The invalid TLV object (including the TLV Header).
This object carries information about a TLV object that was found to
be invalid in the original message. An error message may contain
more than one Object Value Info object.
5.1.3.7. SESSION-ID List (SESSION-ID-LIST)
Type: 0x007
Length: Variable
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Value: A list of 128-bit SESSION-IDs used in summary refresh and
summary tear messages. All SESSION-IDs are concatenated together.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Session ID 1 +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Session ID n +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1.3.8. Reservation Sequence Number (RSN) List (RSN-LIST)
Type: 0x008
Length: Variable
Value: A list of 32-bit Reservation Sequence Number (RSN) values.
All RSN are concatenated together.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Epoch Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reservation Sequence Number 1 (RSN1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reservation Sequence Number n (RSNn) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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5.1.3.9. Message ID (MSG-ID)
Type: 0x009
Length: Fixed - 5 32-bit words
Value: contains a 1-bit Message_Binding_Type (D) that indicates the
dependency relation of a message binding. The rest specifies a
128-bit randomly generated value that "uniquely" identifies this
particular message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED |D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Message ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Message Binding Codes are:
* 0 - Unidirectional binding dependency
* 1 - Bidirectional binding dependency
5.1.3.10. Bound Message ID (BOUND-MSG-ID)
Type: 0x00A
Length: Fixed - 5 32-bit words
Value: contains a 1-bit Message_Binding_Type (D) that indicates the
dependency relation of a message binding. The rest specifies a
128-bit randomly generated value that refers to a Message ID in
another message.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED |D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Bound Message ID +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Message Binding Codes are:
* 0 - Unidirectional binding dependency
* 1 - Bidirectional binding dependency
5.1.3.11. QoS Specification (QSPEC)
Type: 0x00B
Length: Variable
Value: Variable-length QSPEC (QoS specification) information, which
is dependent on the QoS model.
The contents and encoding rules for this object are specified in
other documents. See [RFC5975].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// QSPEC Data //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2. General Processing Rules
This section provides the general processing rules used by QoS-NSLP.
The triggers communicated between RM/QOSM and QoS-NSLP
functionalities are given in Appendices Appendix A.1, Appendix A.2,
and Appendix A.3.
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5.2.1. State Manipulation
The processing of a message and its component objects involves
manipulating the QoS NSLP and reservation state of a QNE.
For each flow, a QNE stores (RMF-related) reservation state that
depends on:
o the QoS model / QSPEC used,
o the QoS NSLP operation state, which includes non-persistent state
(e.g., the API parameters while a QNE is processing a message),
and
o the persistent state, which is kept as long as the session is
active.
The persistent QoS NSLP state is conceptually organized in a table
with the following structure. The primary key (index) for the table
is the SESSION-ID:
SESSION-ID
A 128-bit identifier.
The state information for a given key includes:
Flow ID
Based on GIST MRI. Several entries are possible in case of
mobility events.
SII-Handle for each upstream and downstream peer
The SII-Handle is a local identifier generated by GIST and passed
over the API. It is a handle that allows to refer to a particular
GIST next hop. See SII-Handle in [RFC5971] for more information.
RSN from the upstream peer
The RSN is a 32-bit counter.
The latest local RSN
A 32-bit counter.
List of RII for outstanding responses with processing information.
The RII is a 32-bit number.
State lifetime
The state lifetime indicates how long the state that is being
signaled for remains valid.
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List of bound sessions
A list of BOUND-SESSION-ID 128-bit identifiers for each session
bound to this state.
Scope of the signaling
If the Proxy scope is used, a flag is needed to identify all
signaling of this session as being scoped.
Adding the state requirements of all these items gives an upper bound
on the state to be kept by a QNE. The need to keep state depends on
the desired functionality at the NSLP layer.
5.2.2. Message Forwarding
QoS NSLP messages are sent peer-to-peer along the path. The QoS NSLP
does not have the concept of a message being sent directly to the end
of the path. Instead, messages are received by a QNE, which may then
send another message (which may be identical to the received message
or contain some subset of objects from it) to continue in the same
direction (i.e., towards the QNI or QNR) as the message received.
The decision on whether to generate a message to forward may be
affected by the value of the SCOPING or PROXY flags, or by the
presence of an RII object.
5.2.3. Standard Message Processing Rules
If a mandatory object is missing from a message then the receiving
QNE MUST NOT propagate the message any further. It MUST construct a
RESPONSE message indicating the error condition and send it back to
the peer QNE that sent the message.
If a message contains an object of an unrecognised type, then the
behavior depends on the AB extensibility flags.
If the Proxy scope flag was set in an incoming QoS NSLP message, the
QNE must set the same flag in all QoS NSLP messages it sends that are
related to this session.
5.2.4. Retransmissions
Retransmissions may happen end-to-end (e.g., between QNI and QNR
using an RII object) or peer-to-peer (between two adjacent QNEs).
When a QNE transmits a RESERVE with an RII object set, it waits for a
RESPONSE from the responding QNE. QoS NSLP messages for which a
response is requested by including an RII object, but that fail to
elicit a response are retransmitted. Similarly, a QNE may include
the ACK-REQ flag to request confirmation of a refresh message
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reception from its immediate peer. The retransmitted message should
be exactly the same as the original message, e.g., the RSN is not
modified with each retransmission.
The initial retransmission occurs after a QOSNSLP_REQUEST_RETRY wait
period. Retransmissions MUST be made with exponentially increasing
wait intervals (doubling the wait each time). QoS NSLP messages
SHOULD be retransmitted until either a RESPONSE (which might be an
error) has been obtained, or until QOSNSLP_RETRY_MAX seconds after
the initial transmission. In the latter case, a failure SHOULD be
indicated to the signaling application. The default values for the
above-mentioned timers are:
QOSNSLP_REQUEST_RETRY: 2 seconds Wait interval before initial
retransmit of the message
QOSNSLP_RETRY_MAX: 30 seconds Period to retry sending the
message before giving up
Retransmissions SHOULD be disabled for tear messages.
5.2.5. Rerouting
5.2.5.1. Last Node Behavior
As discussed in Section 3.2.12, some care needs to be taken to handle
cases where the last node on the path may change.
A node that is the last node on the path, but not the data receiver
(or an explicitly configured proxy for it), MUST continue to attempt
to send messages downstream to probe for path changes. This must be
done in order to handle the "Path Extension" case described in
Section 5.2.5.1.
A node on the path, that was not previously the last node, MUST take
over as the last node on the signaling path if GIST path change
detection identifies that there are no further downstream nodes on
the path. This must be done in order to handle the "Path Truncation"
case described in Section 5.2.5.1.
5.2.5.2. Avoiding Mistaken Teardown
In order to handle the spurious route change problem described in
Section 3.2.12.2, the RSN must be used in a particular way when
maintaining the reservation after a route change is believed to have
occurred.
We assume that the current RSN (RSN[current]) is initially RSN0.
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When a route change is believed to have occurred, the QNE SHOULD send
a RESERVE message, including the full QSPEC. This must contain an
RSN which is RSN[current] = RSN0 + 2. It SHOULD include an RII to
request a response from the QNR. An SII-Handle MUST NOT be specified
when passing this message over the API to GIST, so that the message
is correctly routed to the new peer QNE.
When the QNE receives the RESPONSE message that relates to the
RESERVE message sent down the new path, it SHOULD send a RESERVE
message with the TEAR flag sent down the old path. To do so, it MUST
request GIST to use its explicit routing mechanism, and the QoS NSLP
MUST supply an SII-Handle relating to the old peer QNE. When sending
this RESERVE message, it MUST contain an RSN that is RSN[current] -
1. (RSN[current] remains unchanged.)
If the RESPONSE received after sending the RESERVE down the new path
contains the code "Refresh successful" in the INFO-SPEC, then the QNE
MAY elect not to send the tearing RESERVE, since this indicates that
the path is unchanged.
5.2.5.3. Upstream Route Change Notification
GIST may notify the QoS NSLP that a possible upstream route change
has occurred over the GIST API. On receiving such a notification,
the QoS NSLP SHOULD send a NOTIFY message with Informational code
0x02 for signaling sessions associated with the identified MRI. If
this is sent, it MUST be sent to the old peer using the GIST explicit
routing mechanism through the use of the SII-Handle.
On receiving such a NOTIFY message, the QoS NSLP SHOULD use the
InvalidateRoutingState API call to inform GIST that routing state may
be out of date. The QoS NSLP SHOULD send a NOTIFY message upstream.
The NOTIFY message should be propagated back to the QNI or QNR.
5.2.5.4. Route Change Oscillation
In some circumstances, a route change may occur, but the path then
falls back to the original route.
After a route change the routers on the old path will continue to
refresh the reservation until soft state times out or an explicit
TEAR is received.
After detecting an upstream route change, a QNE SHOULD consider the
new upstream peer as current and not fall back to the old upstream
peer unless:
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o it stops receiving refreshes from the old upstream peer for at
least the soft-state timeout period and then starts receiving
messages from the old upstream peer again, or
o it stops receiving refreshes from the new upstream peer for at
least the soft-state timeout period.
GIST routing state keeps track of the latest upstream peer it has
seen, and so may spuriously indicate route changes occur when the old
upstream peer refreshes its routing state until the state at that
node is explicitly torn down or times out.
5.3. Object Processing
This section presents processing rules for individual QoS NSLP
objects.
5.3.1. Reservation Sequence Number (RSN)
A QNE's own RSN is a sequence number which applies to a particular
signaling session (i.e., with a particular SESSION-ID). It MUST be
incremented for each new RESERVE message where the reservation for
the session changes. The RSN is manipulated using the serial number
arithmetic rules from [RFC1982], which also defines wrapping rules
and the meaning of 'equals', 'less than', and 'greater than' for
comparing sequence numbers in a circular sequence space.
The RSN starts at zero. It is stored as part of the per-session
state, and it carries on incrementing (i.e., it is not reset to zero)
when a downstream peer change occurs. (Note that Section 5.2.5.2
provides some particular rules for use when a downstream peer
changes.)
The RSN object also contains an Epoch Identifier, which provides a
method for determining when a peer has restarted (e.g., due to node
reboot or software restart). The exact method for providing this
value is implementation defined. Options include storing a serial
number that is incremented on each restart, picking a random value on
each restart, or using the restart time.
On receiving a RESERVE message a QNE examines the Epoch Identifier to
determine if the peer sending the message has restarted. If the
Epoch Identifier is different to that stored for the reservation then
the RESERVE message MUST be treated as an updated reservation (even
if the RSN is less than the current stored value), and the stored RSN
and Epoch Identifier MUST be updated to the new values.
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When receiving a RESERVE message, a QNE uses the RSN given in the
message to determine whether the state being requested is different
to that already stored. If the RSN is equal to that stored for the
current reservation, the current state MUST be refreshed. If the RSN
is greater than the current stored value, the current reservation
MUST be modified appropriately as specified in the QSPEC (provided
that admission control and policy control succeed), and the stored
RSN value updated to that for the new reservation. If the RSN is
greater than the current stored value and the RESERVE was a reduced
refresh, the QNE SHOULD send upstream a transient error message "Full
QSPEC required". If the RSN is less than the current value, then it
indicates an out-of-order message, and the RESERVE message MUST be
discarded.
If the QNE does not store per-session state (and so does not keep any
previous RSN values), then it MAY ignore the value of the RSN. It
MUST also copy the same RSN into the RESERVE message (if any) that it
sends as a consequence of receiving this one.
5.3.2. Request Identification Information (RII)
A QNE sending QUERY or RESERVE messages may require a response to be
sent. It does so by including a Request Identification Information
(RII) object. When creating an RII object, the QNE MUST select the
value for the RII such that it is probabilistically unique within the
given session. A RII object is typically set by the QNI.
A number of choices are available when implementing this.
Possibilities might include using a random value, or a node
identifier together with a counter. If the value collides with one
selected by another QNE for a different QUERY, then RESPONSE messages
may be incorrectly terminated, and may not be passed back to the node
that requested them.
The node that created the RII object MUST remember the value used in
the RII in order to match back any RESPONSE it will receive. The
node SHOULD use a timer to identify situations where it has taken too
long to receive the expected RESPONSE. If the timer expires without
receiving a RESPONSE, the node MAY perform a retransmission as
discussed in Section 5.2.4. In this case, the QNE MUST NOT generate
any RESPONSE or NOTIFY message to notify this error.
If an intermediate QNE wants to receive a response for an outgoing
message, but the message already included an RII when it arrived, the
QNE MUST NOT add a new RII object nor replace the old RII object, but
MUST simply remember this RII in order to match a later RESPONSE
message. When it receives the RESPONSE, it forwards the RESPONSE
upstream towards the RII originating node. Note that only the node
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that originally created the RII can set up a retransmission timer.
Thus, if an intermediate QNE decides to use the RII already contained
in the message, it MUST NOT set up a retransmission timer, but rely
on the retransmission timer set up by the QNE that inserted the RII.
When receiving a message containing an RII object the node MUST send
a RESPONSE if
o The SCOPING flag is set ('next hop' scope),
o The PROXY scope flag is set and the QNE is the P-QNE, or
o This QNE is the last one on the path for the given session.
and the QNE keeps per-session state for the given session.
In the rare event that the QNE wants to request a response for a
message that already included an RII, and this RII value conflicts
with an existing RII value on the QNE, the node should interrupt the
processing the message, send an error message upstream to indicate an
RII collision, and request a retry with a new RII value.
5.3.3. BOUND-SESSION-ID
As shown in the examples in Section 4, the QoS NSLP can relate
multiple sessions together. It does this by including the SESSION-ID
from one session in a BOUND-SESSION-ID object in messages in another
session.
When receiving a message with a BOUND-SESSION-ID object, a QNE MUST
copy the BOUND-SESSION-ID object into all messages it sends for the
same session. A QNE that stores per-session state MUST store the
value of the BOUND-SESSION-ID.
The BOUND-SESSION-ID is only indicative in nature. However, a QNE
implementation may use BOUND-SESSION-ID information to optimize
resource allocation, e.g., for bidirectional reservations. When
receiving a teardown message (e.g., a RESERVE message with teardown
semantics) for an aggregate reservation, the QNE may use this
information to initiate a teardown for end-to-end sessions bound to
the aggregate. A QoS NSLP implementation MUST be ready to process
more than one BOUND-SESSION-ID object within a single message.
5.3.4. REFRESH-PERIOD
Refresh timer management values are carried by the REFRESH-PERIOD
object, which has local significance only. At the expiration of a
"refresh timeout" period, each QNE independently examines its state
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and sends a refreshing RESERVE message to the next QNE peer where it
is absorbed. This peer-to-peer refreshing (as opposed to the QNI
initiating a refresh that travels all the way to the QNR) allows QNEs
to choose refresh intervals as appropriate for their environment.
For example, it is conceivable that refreshing intervals in the
backbone, where reservations are relatively stable, are much larger
than in an access network. The "refresh timeout" is calculated
within the QNE and is not part of the protocol; however, it must be
chosen to be compatible with the reservation lifetime as expressed by
the REFRESH-PERIOD and with an assessment of the reliability of
message delivery.
The details of timer management and timer changes (slew handling and
so on) are identical to the ones specified in Section 3.7 of RFC 2205
[RFC2205].
There are two time parameters relevant to each QoS NSLP state in a
node: the refresh period R between generation of successive refreshes
for the state by the neighbor node, and the local state's lifetime L.
Each RESERVE message may contain a REFRESH-PERIOD object specifying
the R value that was used to generate this (refresh) message. This R
value is then used to determine the value for L when the state is
received and stored. The values for R and L may vary from peer to
peer.
5.3.5. INFO-SPEC
The INFO-SPEC object is carried by the RESPONSE and NOTIFY messages,
and it is used to report a successful, an unsuccessful, or an error
situation. In case of an error situation, the error messages SHOULD
be generated even if no RII object is included in the RESERVE or in
the QUERY messages. Note that when the TEAR flag is set in the
RESERVE message an error situation SHOULD NOT trigger the generation
of a RESPONSE message.
Six classes of INFO-SPEC objects are identified and specified in
Section 5.1.3.6. The message processing rules for each class are
defined below.
A RESPONSE message MUST carry INFO-SPEC objects towards the QNI. The
RESPONSE message MUST be forwarded unconditionally up to the QNI.
The actions that SHOULD be undertaken by the QNI that receives the
INFO-SPEC object are specified by the local policy of the QoS model
supported by this QNE. The default action is that the QNI that
receives the INFO-SPEC object SHOULD NOT trigger any other QoS NSLP
procedure.
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The Informational INFO-SPEC class MUST be generated by a stateful QoS
NSLP QNE when an Informational error class is caught. The
Informational INFO-SPEC object MUST be carried by a RESPONSE or a
NOTIFY message.
In case of a unidirectional reservation, the Success INFO-SPEC class
MUST be generated by a stateful QoS NSLP QNR when a RESERVE message
is received and the reservation state installation or refresh
succeeded. In case of a bidirectional reservation, the INFO-SPEC
object SHOULD be generated by a stateful QoS NSLP QNE when a RESERVE
message is received and the reservation state installation or refresh
succeeded. The Success INFO-SPEC object MUST be carried by a
RESPONSE or a NOTIFY message.
In case of a unidirectional reservation, the Protocol Error INFO-SPEC
class MUST be generated by a stateful QoS NSLP QNE when a RESERVE or
QUERY message is received by the QNE and a protocol error is caught.
In case of a bidirectional reservation, the Protocol Error INFO-SPEC
class SHOULD be generated by a stateful QoS NSLP QNE when a RESERVE
or QUERY message is received by the QNE and a protocol error is
caught. A RESPONSE message MUST carry this object, which MUST be
forwarded unconditionally towards the upstream QNE that generated the
RESERVE or QUERY message that triggered the generation of this INFO-
SPEC object. The default action for a stateless QoS NSLP QNE that
detects such an error is that none of the QoS NSLP objects SHOULD be
processed, and the RESERVE or QUERY message SHOULD be forwarded
downstream.
In case of a unidirectional reservation, the Transient Failure INFO-
SPEC class MUST be generated by a stateful QoS NSLP QNE when a
RESERVE or QUERY message is received by the QNE and one Transient
failure error code is caught, or when an event happens that causes a
transient error. In case of a bidirectional reservation, the
Transient Failure INFO-SPEC class SHOULD be generated by a stateful
QoS NSLP QNE when a RESERVE or QUERY message is received by the QNE
and one Transient failure error code is caught.
A RESPONSE message MUST carry this object, which MUST be forwarded
unconditionally towards the upstream QNE that generated the RESERVE
or QUERY message that triggered the generation of this INFO-SPEC
object. The transient RMF-related error MAY also be carried by a
NOTIFY message. The default action is that the QNE that receives
this INFO-SPEC object SHOULD re-trigger the retransmission of the
RESERVE or QUERY message that triggered the generation of the INFO-
SPEC object. The default action for a stateless QoS NSLP QNE that
detects such an error is that none of the QoS NSLP objects SHOULD be
processed and the RESERVE or QUERY message SHOULD be forwarded
downstream.
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In case of a unidirectional reservation, the Permanent Failure INFO-
SPEC class MUST be generated by a stateful QoS NSLP QNE when a
RESERVE or QUERY message is received by a QNE and an internal or
system error occurred, or authorization failed. In case of a
bidirectional reservation, the Permanent Failure INFO-SPEC class
SHOULD be generated by a stateful QoS NSLP QNE when a RESERVE or
QUERY message is received by a QNE and an internal or system error
occurred, or authorization failed. A RESPONSE message MUST carry
this object, which MUST be forwarded unconditionally towards the
upstream QNE that generated the RESERVE or QUERY message that
triggered this protocol error. The internal, system, or permanent
RMF-related errors MAY also be carried by a NOTIFY message. The
default action for a stateless QoS NSLP QNE that detects such an
error is that none of the QoS NSLP objects SHOULD be processed and
the RESERVE or QUERY message SHOULD be forwarded downstream.
The QoS-specific error class may be used when errors outside the QoS
NSLP itself occur that are related to the particular QoS model being
used. The processing rules of these errors are not specified in this
document.
5.3.6. SESSION-ID-LIST
A SESSION-ID-LIST is carried in RESERVE messages. It is used in two
cases, to refresh or to tear down the indicated sessions. A SESSION-
ID-LIST carries information about sessions that should be refreshed
or torn down, in addition to the main (primary) session indicated in
the RESERVE.
If the primary SESSION-ID is not understood, the SESSION-ID-LIST
object MUST NOT be processed.
When a stateful QNE goes through the SESSION-ID-LIST, if it finds one
or more unknown SESSION-ID values, it SHOULD construct an
informational RESPONSE message back to the upstream stateful QNE with
the error code for unknown SESSION-ID in SESSION-ID-LIST, and include
all unknown SESSION-IDs in a SESSION-ID-LIST.
If the RESERVE is a tear, for each session in the SESSION-ID-LIST,
the stateful QNE MUST inform the RMF that the reservation is no
longer required. RSN values MUST also be interpreted in order to
distinguish whether the tear down is valid, or whether it is
referring to an old state, and, thus, should be silently discarded.
If the RESERVE is a refresh, the stateful QNE MUST also process the
RSN-LIST object as detailed in the next section.
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If the RESERVE is a tear, for each session in the SESSION-ID-LIST,
the QNE MUST inform the RMF that the reservation is no longer
required. RSN values MUST be interpreted.
Note that a stateless QNE cannot support summary or single reduced
refreshes, and always needs full single refreshes.
5.3.7. RSN-LIST
An RSN-LIST MUST be carried in RESERVE messages when a QNE wants to
perform a refresh or teardown of several sessions with a single NSLP
message. The RSN-LIST object MUST be populated with RSN values of
the same sessions and in the same order as indicated in the SESSION-
ID-LIST. Thus, entries in both objects at position X refer to the
same session.
If the primary session and RSN reference in the RESERVE were not
understood, the stateful QNE MUST NOT process the RSN-LIST. Instead,
an error RESPONSE SHOULD be sent back to the upstream stateful QNE.
On receiving an RSN-LIST object, the stateful QNE should check
whether the number of items in the SESSION-ID-LIST and RSN-LIST
objects match. If there is a mismatch, the stateful QNE SHOULD send
back a protocol error indicating a bad value in the object.
While matching the RSN-LIST values to the SESSION-ID-LIST values, if
one or more RSN values in the RSN-LIST are not in synch with the
local values, the stateful QNE SHOULD construct an informational
RESPONSE message with an error code for RSN mismatch in the RSN-LIST.
The stateful QNE MUST include the erroneous SESSION-ID and RSN values
in SESSION-ID-LIST and RSN-LIST objects in the RESPONSE.
If no errors were found in processing the RSN-LIST, the stateful QNE
refreshes the reservation states of all sessions -- the primary
single session indicated in the refresh, and all sessions in the
SESSION-ID-LIST.
For each successfully processed session in the RESERVE, the stateful
QNE performs a refresh of the reservation state. Thus, even if some
sessions were not in synch, the remaining sessions in the SESSION-ID-
LIST and RSN-LIST are refreshed.
5.3.8. QSPEC
The contents of the QSPEC depend on the QoS model being used. A
template for QSPEC objects can be found in [RFC5975].
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Upon reception, the complete QSPEC is passed to the Resource
Management Function (RMF), along with other information from the
message necessary for the RMF processing. A QNE may also receive an
INFO-SPEC that includes a partial or full QSPEC. This will also be
passed to the RMF.
5.4. Message Processing Rules
This section provides rules for message processing. Not all possible
error situations are considered. A general rule for dealing with
erroneous messages is that a node should evaluate the situation
before deciding how to react. There are two ways to react to
erroneous messages:
a) Silently drop the message, or
b) Drop the message, and reply with an error code to the sender.
The default behavior, in order to protect the QNE from a possible
denial-of-service attack, is to silently drop the message. However,
if the QNE is able to authenticate the sender, e.g., through GIST,
the QNE may send a proper error message back to the neighbor QNE in
order to let it know that there is an inconsistency in the states of
adjacent QNEs.
5.4.1. RESERVE Messages
The RESERVE message is used to manipulate QoS reservation state in
QNEs. A RESERVE message may create, refresh, modify, or remove such
state. A QNE sending a RESERVE MAY require a response to be sent by
including a Request Identification Information (RII) object; see
Section 5.3.2.
RESERVE messages MUST only be sent towards the QNR. A QNE that
receives a RESERVE message checks the message format. In case of
malformed messages, the QNE MAY send a RESPONSE message with the
appropriate INFO-SPEC.
Before performing any state-changing actions, a QNE MUST determine
whether the request is authorized. The way to do this check depends
on the authorization model being used.
When the RESERVE is authorized, a QNE checks the COMMON-HEADER flags.
If the TEAR flag is set, the message is a tearing RESERVE that
indicates complete QoS NSLP state removal (as opposed to a
reservation of zero resources). On receiving such a RESERVE message,
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the QNE MUST inform the RMF that the reservation is no longer
required. The RSN value MUST be processed. After this, there are
two modes of operation:
1. If the tearing RESERVE did not include an RII, i.e., the QNI did
not want a confirmation, the QNE SHOULD remove the QoS NSLP
state. It MAY signal to GIST (over the API) that reverse-path
state for this reservation is no longer required. Any errors in
processing the tearing RESERVE SHOULD NOT be sent back towards
the QNI since the upstream QNEs will already have removed their
session states; thus, they are unable to do anything to the
error.
2. If an RII was included, the stateful QNE SHOULD still keep the
NSLP operational state until a RESPONSE for the tear going
towards the QNI is received. This operational state SHOULD be
kept for one refresh interval, after which the NSLP operational
state for the session is removed. Depending on the QoS model,
the tear message MAY include a QSPEC to further specify state
removal. If the QoS model requires a QSPEC, and none is
provided, the QNE SHOULD reply with an error message and SHOULD
NOT remove the reservation.
If the tearing RESERVE includes a QSPEC, but none is required by the
QoS model, the QNE MAY silently discard the QSPEC and proceed as if
it did not exist in the message. In general, a QoS NSLP
implementation should carefully consider when an error message should
be sent, and when not. If the tearing RESERVE did not include an
RII, then the upstream QNE has removed the RMF and NSLP states, and
it will not be able to do anything to the error. If an RII was
included, the upstream QNE may still have the NSLP operational state,
but no RMF state.
If a QNE receives a tearing RESERVE for a session for which it still
has the operational state, but the RMF state was removed, the QNE
SHOULD accept the message and forward it downstream as if all is
well.
If the tearing RESERVE includes a SESSION-ID-LIST, the stateful QNE
MUST process the object as described earlier in this document, and
for each identified session, indicate to the RMF that the reservation
is no longer required.
If a QNE receives a refreshing RESERVE for a session for which it
still has the operational state, but the RMF state was removed, the
QNE MUST silently drop the message and not forward it downstream.
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As discussed in Section 5.2.5.2, to avoid incorrect removal of state
after a rerouting event, a node receiving a RESERVE message that has
the TEAR flag set and that does not come from the current peer QNE
(identified by its SII) MUST be ignored and MUST NOT be forwarded.
If the QNE has reservations that are bound and dependent to this
session (they contain the SESSION-ID of this session in their BOUND-
SESSION-ID object and use Binding Code 0x04), it MUST send a NOTIFY
message for each of the reservations with an appropriate INFO-SPEC.
If the QNE has reservations that are bound, but that they are not
dependent to this session (the Binding Code in the BOUND-SESSION-ID
object has one of the values: 0x01, 0x02, or 0x03), it MAY send a
NOTIFY message for each of the reservations with an appropriate INFO-
SPEC. The QNE MAY elect to send RESERVE messages with the TEAR flag
set for these reservations.
The default behavior of a QNE that receives a RESERVE with a
SESSION-ID for which it already has state installed but with a
different flow ID is to replace the existing reservation (and to tear
down the reservation on the old branch if the RESERVE is received
with a different SII).
In some cases, this may not be the desired behavior, so the QNI or a
QNE MAY set the REPLACE flag in the common header to zero to indicate
that the new session does not replace the existing one.
A QNE that receives a RESERVE with the REPLACE flag set to zero but
with the same SII will indicate REPLACE=0 to the RMF (where it will
be used for the resource handling). Furthermore, if the QNE
maintains a QoS NSLP state, then it will also add the new flow ID in
the QoS NSLP state. If the SII is different, this means that the QNE
is a merge point. In that case, in addition to the operations
specified above, the value REPLACE=0 is also indicating that a
tearing RESERVE SHOULD NOT be sent on the old branch.
When a QNE receives a RESERVE message with an unknown SESSION-ID and
this message contains no QSPEC because it was meant as a refresh,
then the node MUST send a RESPONSE message with an INFO-SPEC that
indicates a missing QSPEC to the upstream peer ("Full QSPEC
required"). The upstream peer SHOULD send a complete RESERVE (i.e.,
one containing a QSPEC) on the new path (new SII).
At a QNE, resource handling is performed by the RMF. For sessions
with the REPLACE flag set to zero, we assume that the QoS model
includes directions to deal with resource sharing. This may include
adding the reservations or taking the maximum of the two or more
complex mathematical operations.
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This resource-handling mechanism in the QoS model is also applicable
to sessions that have different SESSION-IDs but that are related
through the BOUND-SESSION-ID object. Session replacement is not an
issue here, but the QoS model may specify whether or not to let the
sessions that are bound together share resources on common links.
Finally, it is possible that a RESERVE is received with no QSPEC at
all. This is the case of a reduced refresh. In this case, rather
than sending a refreshing RESERVE with the full QSPEC, only the
SESSION-ID and the RSN are sent to refresh the reservation. Note
that this mechanism just reduces the message size (and probably eases
processing). One RESERVE per session is still needed. Such a
reduced refresh may further include a SESSION-ID-LIST and RSN-LIST,
which indicate further sessions to be refreshed along the primary
session. The processing of these objects was described earlier in
this document.
If the REPLACE flag is set, the QNE SHOULD update the reservation
state according to the QSPEC contained in the message (if the QSPEC
is missing, the QNE SHOULD indicate this error by replying with a
RESPONSE containing the corresponding INFO-SPEC "Full QSPEC
required"). It MUST update the lifetime of the reservation. If the
REPLACE flag is not set, a QNE SHOULD NOT remove the old reservation
state if the SII that is passed by GIST over the API is different
than the SII that was stored for this reservation. The QNE MAY elect
to keep sending refreshing RESERVE messages.
If a stateful QoS NSLP QNE receives a RESERVE message with the BREAK
flag set, then the BREAK flag of newly generated messages (e.g.,
RESERVE or RESPONSE) MUST be set. When a stateful QoS NSLP QNE
receives a RESERVE message with the BREAK flag not set, then the IP-
TTL and Original-TTL values in the GIST RecvMessage primitive MUST be
monitored. If they differ, it is RECOMMENDED to set the BREAK flag
in newly generated messages (e.g., RESERVE or RESPONSE). In
situations where a QNE or a domain is able to provide QoS using other
means (see Section 3.3.5), the BREAK flag SHOULD NOT be set.
If the RESERVE message included an RII, and any of the following are
true, the QNE MUST send a RESPONSE message:
o If the QNE is configured, for a particular session, to be a QNR,
o the SCOPING flag is set,
o the Proxy scope flag is set and the QNE is a P-QNE, or
o the QNE is the last QNE on the path to the destination.
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When a QNE receives a RESERVE message, its processing may involve
sending out another RESERVE message.
If a QNE has received a RESPONSE mandating the use of full refreshes
from its downstream peer for a session, the QNE MUST continue to use
full refresh messages.
If the session of this message is bound to another session, then the
RESERVE message MUST include the SESSION-ID of that other session in
a BOUND-SESSION-ID object. In the situation of aggregated tunnels,
the aggregated session MAY not include the SESSION-ID of its bound
sessions in BOUND-SESSION-ID(s).
In case of receiver-initiated reservations, the RESERVE message must
follow the same path that has been followed by the QUERY message.
Therefore, GIST is informed, over the QoS NSLP/GIST API, to pass the
message upstream, i.e., by setting GIST "D" flag; see GIST [RFC5971].
The QNE MUST create a new RESERVE and send it to its next peer, when:
- A new resource setup was done,
- A new resource setup was not done, but the QOSM still defines that
a RESERVE must be propagated,
- The RESERVE is a refresh and includes a new MRI, or
- If the RESERVE-INIT flag is included in an arrived QUERY.
If the QNE sent out a refresh RESERVE with the ACK-REQ flag set, and
did not receive a RESPONSE from its immediate stateful peer within
the retransmission period of QOSNSLP_RETRY_MAX, the QNE SHOULD send a
NOTIFY to its immediate upstream stateful peer and indicate "Path
truncated - Next peer dead" in the INFO-SPEC. The ACK-REQ flag
SHOULD NOT be added to a RESERVE that already include an RII object,
since a confirmation from the QNR has already been requested.
Finally, if a received RESERVE requested acknowledgement through the
ACK-REQ flag in the COMMON HEADER flags and the processing of the
message was successful, the stateful QNE SHOULD send back a RESPONSE
with an INFO-SPEC carrying the acknowledgement success code. The QNE
MAY include the ACK-REQ flag in the next refresh message it will send
for the session. The use of the ACK-REQ-flag for diagnostic purposes
is a policy issue. An acknowledged refresh message can be used to
probe the end-to-end path in order to check that it is still intact.
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5.4.2. QUERY Messages
A QUERY message is used to request information about the data path
without making a reservation. This functionality can be used to
'probe' the network for path characteristics or for support of
certain QoS models, or to initiate a receiver-initiated reservation.
A QNE sending a QUERY indicates a request for a response by including
a Request Identification Information (RII) object; see Section 5.3.2.
A request to initiate a receiver-initiated reservation is done
through the RESERVE-INIT flag; see Section 5.1.2.2.
When a QNE receives a QUERY message the QSPEC is passed to the RMF
for processing. The RMF may return a modified QSPEC that is used in
any QUERY or RESPONSE message sent out as a result of the QUERY
processing.
When processing a QUERY message, a QNE checks whether the RESERVE-
INIT flag is set. If the flag is set, the QUERY is used to install
reverse-path state. In this case, if the QNE is not the QNI, it
creates a new QUERY message to send downstream. The QSPEC MUST be
passed to the RMF where it may be modified by the QoS-model-specific
QUERY processing. If the QNE is the QNI, the QNE creates a RESERVE
message, which contains a QSPEC received from the RMF and which may
be based on the received QSPEC. If this node was not expecting to
perform a receiver-initiated reservation, then an error MUST be sent
back along the path.
The QNE MUST generate a RESPONSE message and pass it back along the
reverse of the path used by the QUERY if:
o an RII object is present,
o the QNE is the QNR,
o the SCOPING flag is set, or
o the PROXY scope flag is set, and the QNE is a P-QNE.
If an RII object is present, and if the QNE is the QNR, the SCOPING
flag is set or the PROXY scope flag is set and the QNE is a P-QNE,
the QNE MUST generate a RESPONSE message and pass it back along the
reverse of the path used by the QUERY.
In other cases, the QNE MUST generate a QUERY message that is then
forwarded further along the path using the same MRI, Session ID, and
Direction as provided when the QUERY was received over the GIST API.
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The QSPEC to be used is that provided by the RMF as described
previously. When generating a QUERY to send out to pass the query
further along the path, the QNE MUST copy the RII object (if present)
unchanged into the new QUERY message. A QNE that is also interested
in the response to the query keeps track of the RII to identify the
RESPONSE when it passes through it.
Note that QUERY messages with the RESERVE-INIT flag set MUST be
answered by the QNR. This feature may be used, e.g., following
handovers, to set up new path state in GIST and to request that the
other party to send a RESERVE back on this new GIST path.
If a stateful QoS NSLP QNE receives a QUERY message with the RESERVE-
INIT flag and BREAK flag set, then the BREAK flag of newly generated
messages (e.g., QUERY, RESERVE, or RESPONSE) MUST be set. When a
stateful QoS NSLP QNE receives a QUERY message with the RESERVE-INIT
flag set and BREAK flag not set, then the IP-TTL and Original-TTL
values in GIST RecvMessage primitive MUST be monitored. If they
differ, it is RECOMMENDED to set the BREAK flag in newly generated
messages (e.g., QUERY, RESERVE, or RESPONSE). In situations where a
QNE or a domain is able to provide QoS using other means (see
Section 3.3.5), the BREAK flag SHOULD NOT be set.
Finally, if a received QUERY requested acknowledgement through the
ACK-REQ flag in the COMMON HEADER flags and the processing of the
message was successful, the stateful QNE SHOULD send back a RESPONSE
with an INFO-SPEC carrying the acknowledgement success code.
5.4.3. RESPONSE Messages
The RESPONSE message is used to provide information about the result
of a previous QoS NSLP message, e.g., confirmation of a reservation
or information resulting from a QUERY. The RESPONSE message does not
cause any state to be installed, but may cause state(s) to be
modified, e.g., if the RESPONSE contains information about an error.
A RESPONSE message MUST be sent when the QNR processes a RESERVE or
QUERY message containing an RII object or if the QNE receives a
scoped RESERVE or a scoped QUERY. In this case, the RESPONSE message
MUST contain the RII object copied from the RESERVE or the QUERY.
Also, if there is an error in processing a received RESERVE, a
RESPONSE is sent indicating the nature of the error. In this case,
the RII and RSN, if available, MUST be included in the RESPONSE.
On receipt of a RESPONSE message containing an RII object, the
stateful QoS NSLP QNE MUST attempt to match it to the outstanding
response requests for that signaling session. If the match succeeds,
then the RESPONSE MUST NOT be forwarded further along the path if it
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contains an Informational or Success INFO-SPEC class. If the QNE did
not insert this RII itself, it must forward the RESPONSE to the next
peer. Thus, for RESPONSEs indicating success, forwarding should only
stop if the QNE inserted the RII by itself. If the RESPONSE carries
an INFO-SPEC indicating an error, forwarding SHOULD continue upstream
towards the QNI by using RSNs as described in the next paragraph.
On receipt of a RESPONSE message containing an RSN object, a stateful
QoS NSLP QNE MUST compare the RSN to that of the appropriate
signaling session. If the match succeeds, then the INFO-SPEC MUST be
processed. If the INFO-SPEC object is used to send error
notifications then the node MUST use the stored upstream peer RSN
value, associated with the same session, and forward the RESPONSE
message further along the path towards the QNI.
If the INFO-SPEC is not used to notify error situations (see above),
then if the RESPONSE message carries an RSN, the message MUST NOT be
forwarded further along the path.
If there is no match for RSN, the message SHOULD be silently dropped.
On receipt of a RESPONSE message containing neither an RII nor an RSN
object, the RESPONSE MUST NOT be forwarded further along the path.
In the typical case, RESPONSE messages do not change the states
installed in intermediate QNEs. However, depending on the QoS model,
there may be situations where states are affected, e.g.,
- if the RESPONSE includes an INFO-SPEC describing an error
situation resulting in reservations to be removed, or
- the QoS model allows a QSPEC to define [min,max] limits on the
resources requested, and downstream QNEs gave less resources than
their upstream nodes, which means that the upstream nodes may
release a part of the resource reservation.
If a stateful QoS NSLP QNE receives a RESPONSE message with the BREAK
flag set, then the BREAK flag of newly generated message (e.g.,
RESPONSE) MUST be set.
5.4.4. NOTIFY Messages
NOTIFY messages are used to convey information to a QNE
asynchronously. NOTIFY messages do not cause any state to be
installed. The decision to remove state depends on the QoS model.
The exact operation depends on the QoS model. A NOTIFY message does
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not directly cause other messages to be sent. NOTIFY messages are
sent asynchronously, rather than in response to other messages. They
may be sent in either direction (upstream or downstream).
A special case of synchronous NOTIFY is when the upstream QNE is
asked to use reduced refresh by setting the appropriate flag in the
RESERVE. The QNE receiving such a RESERVE MUST reply with a NOTIFY
and a proper INFO-SPEC code indicating whether the QNE agrees to use
reduced refresh between the upstream QNE.
The Transient error code 0x07 "Reservation preempted" is sent to the
QNI whose resources were preempted. The NOTIFY message carries
information to the QNI that one QNE no longer has a reservation for
the session. It is up to the QNI to decide what to do based on the
QoS model being used. The QNI would normally tear down the preempted
reservation by sending a RESERVE with the TEAR flag set using the SII
of the preempted reservation. However, the QNI can follow other
procedures as specified in its QoS Model. More discussion on
preemption can be found in the QSPEC Template [RFC5975] and the
individual QoS Model specifications.
6. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the QoS
NSLP, in accordance with BCP 26, RFC 5226 [RFC5226].
Per QoS NSLP, IANA has created a number of new registries:
- QoS NSLP Message Types
- QoS NSLP Binding Codes
- QoS NSLP Error Classes
- Informational Error Codes
- Success Error Codes
- Protocol Error Codes
- Transient Failure Codes
- Permanent Failure Codes
- QoS NSLP Error Source Identifiers
IANA has also registered new values in a number of registries:
- NSLP Object Types
- NSLP Identifiers (under GIST Parameters)
- Router Alert Option Values (IPv4 and IPv6)
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6.1. QoS NSLP Message Type
The QoS NSLP Message Type is an 8-bit value. This specification
defines four QoS NSLP message types, which form the initial contents
of this registry: RESERVE (0x01), QUERY (0x02), RESPONSE (0x03), and
NOTIFY (0x04).
The value 0 is reserved. Values 240 to 255 are for Experimental/
Private Use. The registration procedure is IETF Review.
When a new message type is defined, any message flags used with it
must also be defined.
6.2. NSLP Message Objects
A new registry has been created for NSLP Message Objects. This is a
12-bit field (giving values from 0 to 4095). This registry is shared
between a number of NSLPs.
Registration procedures are as follows:
0: Reserved
1-1023: IETF Review
1024-1999: Specification Required
Allocation policies are as follows:
2000-2047: Private/Experimental Use
2048-4095: Reserved
When a new object is defined, the extensibility bits (A/B) must also
be defined.
This document defines eleven new NSLP message objects. These are
described in Section 5.1.3: RII (0x001), RSN (0x002), REFRESH-PERIOD
(0x003), BOUND-SESSION-ID (0x004), PACKET-CLASSIFIER (0x005), INFO-
SPEC (0x006), SESSION-ID-LIST (0x007), RSN-LIST (0x008), MSG-ID
(0x009), BOUND-MSG-ID (0x00A), and QSPEC (0x00B).
Additional values are to be assigned from the IETF Review section of
the NSLP Message Objects registry.
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6.3. QoS NSLP Binding Codes
A new registry has been created for the 8-bit Binding Codes used in
the BOUND-SESSION-ID object. The initial values for this registry
are listed in Section 5.1.3.4.
The registration procedure is IETF Review. Value 0 is reserved.
Values 128 to 159 are for Experimental/Private Use. Other values are
Reserved.
6.4. QoS NSLP Error Classes and Error Codes
In addition, Error Classes and Error Codes for the INFO-SPEC object
are defined. These are described in Section 5.1.3.6.
The Error Class is 4 bits in length. The initial values are:
0: Reserved
1: Informational
2: Success
3: Protocol Error
4: Transient Failure
5: Permanent Failure
6: QoS Model Error
7: Signaling session failure (described in [RFC5973])
8-15: Reserved
Additional values are to be assigned based on IETF Review.
The Error Code is 8 bits in length. Each Error Code is assigned
within a particular Error Class. This requires the creation of a
registry for Error Codes in each Error Class. The Error Code 0 in
each class is Reserved.
Policies for the error code registries are as follows:
0-63: IETF Review
64-127: Specification Required
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128-191: Experimental/Private Use
192-255: Reserved
The initial assignments for the Error Code registries are given in
Section 5.1.3.6. Experimental and Reserved values are relevant to
all Error classes.
6.5. QoS NSLP Error Source Identifiers
Section 5.1.3.6 defines Error Source Identifiers, the type of which
is identified by a 4-bit value.
The value 0 is reserved.
Values 1-3 are given in Section 5.1.3.6.
Values 14 and 15 are for Experimental/Private Use.
The registration procedure is Specification Required.
6.6. NSLP IDs and Router Alert Option Values
This specification defines an NSLP for use with GIST. Furthermore,
it specifies that a number of NSLPID values are used for the support
of bypassing intermediary nodes. Consequently, new identifiers must
be assigned for them from the GIST NSLP identifier registry. As
required by the QoS NSLP, 32 NSLPID values have been assigned,
corresponding to QoS NSLP Aggregation Levels 0 to 31.
The GIST specification also requires that NSLPIDs be associated with
specific Router Alert Option (RAO) values (although multiple NSLPIDs
may be associated with the same value). For the purposes of the QoS
NSLP, each of its NSLPID values should be associated with a different
RAO value. A block of 32 new IPv4 RAO values and a block of 32 new
IPv6 RAO values have been assigned, corresponding to QoS NSLP
Aggregation Levels 0 to 31.
7. Security Considerations
The security requirement for the QoS NSLP is to protect the signaling
exchange for establishing QoS reservations against identified
security threats. For the signaling problem as a whole, these
threats have been outlined in NSIS threats [RFC4081]; the NSIS
framework [RFC4080] assigns a subset of the responsibility to GIST,
and the remaining threats need to be addressed by NSLPs. The main
issues to be handled can be summarized as:
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Authorization:
The QoS NSLP must assure that the network is protected against
theft-of-service by offering mechanisms to authorize the QoS
reservation requester. A user requesting a QoS reservation might
want proper resource accounting and protection against spoofing
and other security vulnerabilities that lead to denial of service
and financial loss. In many cases, authorization is based on the
authenticated identity. The authorization solution must provide
guarantees that replay attacks are either not possible or limited
to a certain extent. Authorization can also be based on traits
that enable the user to remain anonymous. Support for user
identity confidentiality can be accomplished.
Message Protection:
Signaling message content should be protected against
modification, replay, injection, and eavesdropping while in
transit. Authorization information, such as authorization tokens,
needs protection. This type of protection at the NSLP layer is
necessary to protect messages between NSLP nodes.
Rate Limitation:
QNEs should perform rate-limiting on the refresh messages that
they send. An attacker could send erroneous messages on purpose,
forcing the QNE to constantly reply with an error message.
Authentication mechanisms would help in figuring out if error
situations should be reported to the sender, or silently ignored.
If the sender is authenticated, the QNE should reply promptly.
Prevention of Denial-of-Service Attacks:
GIST and QoS NSLP nodes have finite resources (state storage,
processing power, bandwidth). The protocol mechanisms in this
document try to minimize exhaustion attacks against these
resources when performing authentication and authorization for QoS
resources.
To some extent, the QoS NSLP relies on the security mechanisms
provided by GIST, which by itself relies on existing authentication
and key exchange protocols. Some signaling messages cannot be
protected by GIST and hence should be used with care by the QoS NSLP.
An API must ensure that the QoS NSLP implementation is aware of the
underlying security mechanisms and must be able to indicate which
degree of security is provided between two GIST peers. If a level of
security protection for QoS NSLP messages that is required goes
beyond the security offered by GIST or underlying security
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mechanisms, additional security mechanisms described in this document
must be used. Due to the different usage environments and scenarios
where NSIS is used, it is very difficult to make general statements
without reducing its flexibility.
7.1. Trust Relationship Model
This specification is based on a model that requires trust between
neighboring NSLP nodes to establish a chain-of-trust along the QoS
signaling path. The model is simple to deploy, was used in previous
QoS authorization environments (such as RSVP), and seems to provide
sufficiently strong security properties. We refer to this model as
the New Jersey Turnpike.
On the New Jersey Turnpike, motorists pick up a ticket at a toll
booth when entering the highway. At the highway exit, the ticket is
presented and payment is made at the toll booth for the distance
driven. For QoS signaling in the Internet, this procedure is roughly
similar. In most cases, the data sender is charged for transmitted
data traffic where charging is provided only between neighboring
entities.
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+------------------+ +------------------+ +------------------+
| Network | | Network | | Network |
| X | | Y | | Z |
| | | | | |
| -----------> -----------> |
| | | | | |
| | | | | |
+--------^---------+ +------------------+ +-------+----------+
| .
| .
| v
+--+---+ Data Data +--+---+
| Node | ==============================> | Node |
| A | Sender Receiver | B |
+------+ +------+
Legend:
----> Peering relationship that allows neighboring
networks/entities to charge each other for the
QoS reservation and data traffic
====> Data flow
.... Communication to the end host
Figure 16: New Jersey Turnpike Model
The model shown in Figure 16 uses peer-to-peer relationships between
different administrative domains as a basis for accounting and
charging. As mentioned above, based on the peering relationship, a
chain-of-trust is established. There are several issues that come to
mind when considering this type of model:
o The model allows authorization on a request basis or on a per-
session basis. Authorization mechanisms are elaborated in
Section 7.2. The duration for which the QoS authorization is
valid needs to be controlled. Combining the interval with the
soft-state interval is possible. Notifications from the networks
also seem to be a viable approach.
o The price for a QoS reservation needs to be determined somehow and
communicated to the charged entity and to the network where the
charged entity is attached. Protocols providing "Advice of
Charge" functionality are out of scope.
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o This architecture is simple enough to allow a scalable solution
(ignoring reverse charging, multicast issues, and price
distribution).
Charging the data sender as performed in the model simplifies
security handling by demanding only peer-to-peer security protection.
Node A would perform authentication and key establishment. The
established security association (together with the session key)
would allow the user to protect QoS signaling messages. The identity
used during the authentication and key establishment phase would be
used by Network X (see Figure 16) to perform the so-called policy-
based admission control procedure. In our context, this user
identifier would be used to establish the necessary infrastructure to
provide authorization and charging. Signaling messages later
exchanged between the different networks are then also subject to
authentication and authorization. However, the authenticated entity
is thereby the neighboring network and not the end host.
The New Jersey Turnpike model is attractive because of its
simplicity. S. Shenker, et al. [shenker] discuss various accounting
implications and introduced the edge pricing model. The edge pricing
model shows similarity to the model described in this section, with
the exception that mobility and the security implications are not
addressed.
7.2. Authorization Model Examples
Various authorization models can be used in conjunction with the QoS
NSLP.
7.2.1. Authorization for the Two-Party Approach
The two-party approach (Figure 17) is conceptually the simplest
authorization model.
+-------------+ QoS request +--------------+
| Entity |----------------->| Entity |
| requesting | | authorizing |
| resource |granted / rejected| resource |
| |<-----------------| request |
+-------------+ +--------------+
^ ^
+...........................+
compensation
Figure 17: Two-Party Approach
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In this example, the authorization decision only involves the two
entities, or makes use of previous authorization using an out-of-band
mechanism to avoid the need for active participation of an external
entity during the NSIS protocol execution.
This type of model may be applicable, e.g., between two neighboring
networks (inter-domain signaling) where a long-term contract (or
other out-of-band mechanisms) exists to manage charging and provides
sufficient information to authorize individual requests.
7.2.2. Token-Based Three-Party Approach
An alternative approach makes use of tokens, such as those described
in RFC 3520 [RFC3520] and RFC 3521 [RFC3521] or used as part of the
Open Settlement Protocol [osp]. Authorization tokens are used to
associate two different signaling protocols runs (e.g., SIP and NSIS)
and their authorization decision with each other. The latter is a
form of assertion or trait. As an example, with the authorization
token mechanism, some form of authorization is provided by the SIP
proxy, which acts as the resource-authorizing entity in Figure 18.
If the request is authorized, then the SIP signaling returns an
authorization token that can be included in the QoS signaling
protocol messages to refer to the previous authorization decision.
The tokens themselves may take a number of different forms, some of
which may require the entity performing the QoS reservation to query
the external state.
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Authorization
Token Request +--------------+
+-------------->| Entity C | financial settlement
| | authorizing | <..................+
| | resource | .
| +------+ request | .
| | +--------------+ .
| | .
| |Authorization .
| |Token .
| | .
| | .
| | .
| | QoS request .
+-------------+ + Authz. Token +--------------+ .
| Entity |----------------->| Entity B | .
| requesting | | performing | .
| resource |granted / rejected| QoS | <..+
| A |<-----------------| reservation |
+-------------+ +--------------+
Figure 18: Token-Based Three-Party Approach
For the digital money type of systems (e.g., OSP tokens), the token
represents a limited amount of credit. So, new tokens must be sent
with later refresh messages once the credit is exhausted.
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7.2.3. Generic Three-Party Approach
Another method is for the node performing the QoS reservation to
delegate the authorization decision to a third party, as illustrated
in Figure 19. The authorization decision may be performed on a per-
request basis, periodically, or on a per-session basis.
+--------------+
| Entity C |
| authorizing |
| resource |
| request |
+-----------+--+
^ |
QoS | | QoS
authz| |authz
req.| | res.
QoS | v
+-------------+ request +--+-----------+
| Entity |----------------->| Entity B |
| requesting | | performing |
| resource |granted / rejected| QoS |
| A |<-----------------| reservation |
+-------------+ +--------------+
Figure 19: Three-Party Approach
7.3. Computing the Authorization Decision
Whenever an authorization decision has to be made there is the
question about which information serves as an input to the
authorizing entity. The following information items have been
mentioned in the past for computing the authorization decision (in
addition to the authenticated identity):
Price
QoS objects
Policy rules
Policy rules take into consideration attributes like time of day,
subscription to certain services, membership, etc., when computing an
authorization decision.
The policies used to make the authorization are outside the scope of
this document and are implementation/deployment specific.
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8. Acknowledgments
The authors would like to thank Eleanor Hepworth, Ruediger Geib,
Roland Bless, Nemeth Krisztian, Markus Ott, Mayi Zoumaro-Djayoon,
Martijn Swanink, and Ruud Klaver for their useful comments. Roland,
especially, has done deep reviews of the document, making sure the
protocol is well defined. Bob Braden provided helpful comments and
guidance which were gratefully received.
9. Contributors
This document combines work from three individual documents. The
following authors from these documents also contributed to this
document: Robert Hancock (Siemens/Roke Manor Research), Hannes
Tschofenig and Cornelia Kappler (Siemens AG), Lars Westberg and
Attila Bader (Ericsson), and Maarten Buechli (Dante) and Eric
Waegeman (Alcatel). In addition, Roland Bless has contributed
considerable amounts of text all along the writing of this
specification.
Sven Van den Bosch was the initial editor of earlier draft versions
of this document. Since version 06 of the document, Jukka Manner has
taken the editorship. Yacine El Mghazli (Alcatel) contributed text
on AAA. Charles Shen and Henning Schulzrinne suggested the use of
the reason field in the BOUND-SESSION-ID.
10. References
10.1. Normative References
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic",
RFC 1982, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", RFC 5971, October 2010.
[RFC5975] Ash, G., Bader, A., Kappler, C., and D. Oran, "QSPEC
Template for the Quality-of-Service NSIS Signaling Layer
Protocol (NSLP)", RFC 5975, October 2010.
10.2. Informative References
[NSIS-AUTH] Manner, J., Stiemerling, M., Tschofenig, H., and R.
Bless, Ed., "Authorization for NSIS Signaling Layer
Protocols", Work in Progress, May 2010.
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[NSIS-MOB] Sanda, T., Fu, X., Jeong, S., Manner, J., and H.
Tschofenig, "NSIS Protocols operation in Mobile
Environments", Work in Progress, May 2010.
[RFC1633] Braden, B., Clark, D., and S. Shenker, "Integrated
Services in the Internet Architecture: an Overview",
RFC 1633, June 1994.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version
1 Functional Specification", RFC 2205, September 1997.
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, April 2001.
[RFC3175] Baker, F., Iturralde, C., Le Faucheur, F., and B. Davie,
"Aggregation of RSVP for IPv4 and IPv6 Reservations",
RFC 3175, September 2001.
[RFC3520] Hamer, L-N., Gage, B., Kosinski, B., and H. Shieh,
"Session Authorization Policy Element", RFC 3520,
April 2003.
[RFC3521] Hamer, L-N., Gage, B., and H. Shieh, "Framework for
Session Set-up with Media Authorization", RFC 3521,
April 2003.
[RFC3726] Brunner, M., "Requirements for Signaling Protocols",
RFC 3726, April 2004.
[RFC4080] Hancock, R., Karagiannis, G., Loughney, J., and S. Van
den Bosch, "Next Steps in Signaling (NSIS): Framework",
RFC 4080, June 2005.
[RFC4081] Tschofenig, H. and D. Kroeselberg, "Security Threats for
Next Steps in Signaling (NSIS)", RFC 4081, June 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
Manner, et al. Experimental [Page 92]
RFC 5974 QoS NSLP October 2010
[RFC5973] Stiemerling, M., Tschofenig, H., Aoun, C., and E.
Davies, "NAT/Firewall NSIS Signaling Layer Protocol
(NSLP)", RFC 5973, October 2010.
[RFC5977] Bader, A., Westberg, L., Karagiannis, G., Kappler, C.,
Tschofenig, H., and T. Phelan, "RMD-QOSM: The NSIS
Quality-of-Service Model for Resource Management in
Diffserv", RFC 5977, October 2010.
[lrsvp] Manner, J. and K. Raatikainen, "Localized QoS Management
for Multimedia Applications in Wireless Access
Networks", IASTED IMSA, Technical Specification 101 321,
p. 193-200, August 2004.
[opwa95] Breslau, L., "Two Issues in Reservation Establishment",
Proc. ACM SIGCOMM '95, Cambridge MA, August 1995.
[osp] ETSI, "Telecommunications and Internet Protocol
Harmonization Over Networks (TIPHON); Open Settlement
Protocol (OSP) for Inter-Domain pricing, authorization,
and usage exchange", Technical Specification 101 321,
version 4.1.1.
[qos-auth] Tschofenig, H., "QoS NSLP Authorization Issues", Work
in Progress, June 2003.
[shenker] Shenker, S., et al., "Pricing in computer networks:
Reshaping the research agenda", Proc. of TPRC 1995,
1995.
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Appendix A. Abstract NSLP-RMF API
This appendix is purely informational and provides an abstract API
between the QoS NSLP and the RMF. It should not be taken as a strict
rule for implementors, but rather it helps clarify the interface
between the NSLP and RMF.
A.1. Triggers from QOS-NSLP towards RMF
The QoS-NSLP triggers the RMF/QOSM functionality by using the
sendrmf() primitive:
int sendrmf(sid, nslp_req_type, qspec, authorization_info,
NSLP_objects, filter, features_in, GIST_API_triggers,
incoming_interface, outgoing_interface)
o sid: SESSION-ID - The NSIS session identifier
o nslp_req_type: indicates type of request:
* RESERVE
* QUERY
* RESPONSE
* NOTIFY
o qspec: the QSPEC object, if present
o authorization_info: the AUTH_SESSION object, if present
o NSLP_objects: data structure that contains a list with received
QoS-NSLP objects. This list can be used by, e.g., local
applications, network management, or policy control modules:
* RII
* RSN
* BOUND-SESSION-ID list
* REFRESH-PERIOD
* SESSION-ID-LIST
* RSN-LIST
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* INFO-SPEC
* MSG-ID
* BOUND-MSG-ID
o filter: the information for packet filtering, based on the MRI and
the PACKET-CLASSIFIER object.
o features_in: it represents the flags included in the common header
of the received QOS-NSLP message, but also additional triggers:
* BREAK
* REQUEST REDUCED REFRESHES
* RESERVE-INIT
* TEAR
* REPLACE
* ACK-REQ
* PROXY
* SCOPING
* synchronization_required: this attribute is set (see Sections
Section 4.6 and Section 4.7.1, for example) when the QoS-NSLP
functionality supported by a QNE Egress receives a non-tearing
RESERVE message that includes a MSG-ID or a BOUND-MSG-ID
object, and the BINDING_CODE value of the BOUND-SESSION-ID
object is equal to one of the following values:
+ Tunnel and end-to-end sessions
+ Aggregate sessions
* GIST_API_triggers: it represents the attributes that are
provided by GIST to QoS-NSLP via the GIST API:
+ NSLPID
+ Routing-State-Check
+ SII-Handle
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+ Transfer-Attributes
+ GIST-Hop-Count
+ IP-TTL
+ IP-Distance
o incoming_interface: the ID of the incoming interface. Used only
when the QNE reserves resources on incoming interface. Default is
0 (no reservations on incoming interface)
o outgoing_interface: the ID of the outgoing interface. Used only
when the QNE reserves resources on outgoing interface. Default is
0 (no reservations on outgoing interface)
A.2. Triggers from RMF/QOSM towards QOS-NSLP
The RMF triggers the QoS-NSLP functionality using the "recvrmf()" and
"config()" primitives to perform either all or a subset of the
features listed below.
The recvrmf() primitive represents either a response to a request
that has been sent via the API by the QoS-NSLP or an asynchronous
notification. Note that when the RMF/QOSM receives a request via the
API from the QoS-NSLP function, one or more "recvrmf()" response
primitives can be sent via the API towards QoS-NSLP. In this way,
the QOS-NSLP can generate one or more QoS-NSLP messages that can be
used, for example, in the situation that the arrival of one end-to-
end RESERVE triggers the generation of two (or more) RESERVE
messages: an end-to-end RESERVE message and one (or more) intra-
domain (local) RESERVE message.
The config() primitive is used to configure certain features, such as
QNE type, stateful or stateless operation, or bypassing of end-to-end
messages.
Note that the selection of the subset of triggers is controlled by
the QoS Model.
int recvrmf(sid, nslp_resp_type, qspec, authorization_info, status,
NSLP_objects, filter, features_out, GIST_API_triggers
incoming_interface, outgoing_interface)
o sid: SESSION-ID - The NSIS session identifier
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o nslp_resp_type: indicates type of response:
* RESERVE
* QUERY
* RESPONSE
* NOTIFY
o qspec: the QSPEC object, if present
o authorization_info: the AUTHO_SESSION object, if present
o status: boolean that notifies the status of the reservation and
can be used by QOS-NSLP to include in the INFO-SPEC object:
* RESERVATION_SUCCESSFUL
* TEAR_DOWN_SUCCESSFUL
* NO RESOURCES
* RESERVATION_FAILURE
* RESERVATION_PREEMPTED: reservation was preempted
* AUTHORIZATION_FAILED: authorizing the request failed
* MALFORMED_QSPEC: request failed due to malformed qspec
* SYNCHRONIZATION_FAILED: Mismatch synchronization between an
end-to-end RESERVE and an intra-domain RESERVE (see Sections
Section 4.6 and Section 4.7.1)
* CONGESTION_SITUATION: Possible congestion situation occurred on
downstream path
* QoS Model Error
o NSLP_objects: data structure that contains a list with QoS-NSLP
objects that can be used by QoS-NSLP when the QNE is a QNI, QNR,
QNI_Ingress, QNR_Ingress, QNI_Egress, or QNR_Egress:
* RII
* RSN
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* BOUND-SESSION-ID list
* REFRESH-PERIOD
* SESSION-ID-LIST
* RSN-LIST
* MSG-ID
* BOUND-MSG-ID
o filter: it represents the MRM-related PACKET CLASSIFIER
o features_out: it represents (among others) the flags that can be
used by the QOS-NSLP for newly generated QoS-NSLP messages:
* BREAK
* REQUEST REDUCED REFRESHES
* RESERVE-INIT
* TEAR
* REPLACE
* ACK-REQ
* PROXY
* SCOPING
* BYPASSING - when the outgoing message should be bypassed, then
it includes the required bypassing level. Otherwise, it is
empty. It can be set only by QNI_Ingress, QNR_Ingress,
QNI_Egress, or QNR_Egress. It can be unset only by
QNI_Ingress, QNR_Ingress, QNI_Egress, or QNR_Egress.
* BINDING () - when BINDING is required, then it includes a
BOUND-SESSION-ID list. Otherwise, it is empty. It can only be
requested by the following QNE types: QNI, QNR, QNI_Ingress,
QNR_Ingress, QNI_Egress, or QNR_Egress.
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* NEW_SID - it requests to generate a new session with a new
SESSION-ID. If the QoS-NSLP generates a new SESSION-ID, then
the QoS-NSLP has to return the value of this new SESSION-ID to
the RMF/QOSM. It can be requested by a QNI, QNR, QNI_Ingress,
QNI_Egress, QNR_Ingress, or QNR_Egress.
* NEW_RSN - it requests to generate a new RSN. If the QoS-NSLP
generates a new RSN, then the QoS-NSLP has to return the value
of this new RSN to the RMF/QOSM.
* NEW_RII - it requests to generate a new RII. If the QoS-NSLP
generates a new RII, then the QoS-NSLP has to return the value
of this new RII to the RMF/QOSM.
o GIST_API_triggers: it represents the attributes that are provided
to GIST via QoS-NSLP via the GIST API:
* NSLPID
* SII-Handle
* Transfer-Attributes
* GIST-Hop-Count
* IP-TTL
* ROUTING-STATE-CHECK (if set, it requires that GIST create a
routing state)
o incoming_interface: the ID of the incoming interface. Used only
when the QNE reserves resources on the incoming interface.
Default is 0 (no reservations on the incoming interface).
o outgoing_interface: the ID of the outgoing interface. Used only
when the QNE reserves resources on the outgoing interface.
Default is 0 (no reservations on the outgoing interface).
A.3. Configuration Interface
The config() function is meant for configuring per-session settings,
from the RMF towards the NSLP.
int config(sid, qne_type, state_type, bypassing_type)
o sid: SESSION-ID - The NSIS session identifier
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o qne_type: it defines the type of a QNE
* QNI
* QNI_Ingress: the QNE is a QNI and an Ingress QNE
* QNE: the QNE is not a QNI or QNR
* QNE_Interior: the QNE is an Interior QNE, but it is not a QNI
or QNR
* QNI_Egress: the QNE is a QNI and an Egress QNE
* QNR
* QNR_Ingress: the QNE is a QNR and an Ingress QNE
* QNR_Egress: the QNE is a QNR and an Egress QNE
o state_type: it defines if the QNE keeps QoS-NSLP operational
states
* STATEFUL
* STATELESS
o bypassing_type: it defines if a QNE bypasses end-to-end messages
or not
Appendix B. Glossary
AAA: Authentication, Authorization, and Accounting
EAP: Extensible Authentication Protocol
MRI: Message Routing Information (see [RFC5971])
NAT: Network Address Translator
NSLP: NSIS Signaling Layer Protocol (see [RFC4080])
NTLP: NSIS Transport Layer Protocol (see [RFC4080])
OPWA: One Pass With Advertising
OSP: Open Settlement Protocol
PIN: Policy-Ignorant Node
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QNE: an NSIS Entity (NE), which supports the QoS NSLP (see Section 2)
QNI: the first node in the sequence of QNEs that issues a reservation
request for a session (see Section 22)
QNR: the last node in the sequence of QNEs that receives a
reservation request for a session (see Section 22)
QSPEC: Quality-of-Service Specification
RII: Request Identification Information
RMD: Resource Management for Diffserv
RMF: Resource Management Function
RSN: Reservation Sequence Number
RSVP: Resource Reservation Protocol (see [RFC2205])
SII: Source Identification Information
SIP: Session Initiation Protocol
SLA: Service Level Agreement
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Authors' Addresses
Jukka Manner
Aalto University
Department of Communications and Networking (Comnet)
P.O. Box 13000
FIN-00076 Aalto
Finland
Phone: +358 9 470 22481
EMail: jukka.manner@tkk.fi
URI: http://www.netlab.tkk.fi/~jmanner/
Georgios Karagiannis
University of Twente/Ericsson
P.O. Box 217
Enschede 7500 AE
The Netherlands
EMail: karagian@cs.utwente.nl
Andrew McDonald
Roke Manor Research Ltd
Old Salisbury Lane
Romsey, Hampshire S051 0ZN
United Kingdom
EMail: andrew.mcdonald@roke.co.uk
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