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Keywords: [--------], Diameter, AAA, QoS, Policy, VoIP, SIP
Internet Engineering Task Force (IETF) D. Sun, Ed.
Request for Comments: 5866 Alcatel-Lucent
Category: Standards Track P. McCann
ISSN: 2070-1721 Motorola Labs
H. Tschofenig
Nokia Siemens Networks
T. Tsou
Huawei
A. Doria
Lulea University of Technology
G. Zorn, Ed.
Network Zen
May 2010
Diameter Quality-of-Service Application
Abstract
This document describes the framework, messages, and procedures for
the Diameter Quality-of-Service (QoS) application. The Diameter QoS
application allows network elements to interact with Diameter servers
when allocating QoS resources in the network. In particular, two
modes of operation, namely "Pull" and "Push", are defined.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in 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/rfc5866.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Sun, et al. Standards Track [Page 1]
RFC 5866 Diameter QoS Application May 2010
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Network Element Functional Model . . . . . . . . . . . . . 7
3.2. Implications of Endpoint QoS Capabilities . . . . . . . . 8
3.2.1. Endpoint Categories . . . . . . . . . . . . . . . . . 8
3.2.2. Interaction Modes between the Authorizing Entity
and Network Element . . . . . . . . . . . . . . . . . 9
3.3. Authorization Schemes . . . . . . . . . . . . . . . . . . 10
3.3.1. Pull Mode Schemes . . . . . . . . . . . . . . . . . . 10
3.3.2. Push Mode Schemes . . . . . . . . . . . . . . . . . . 13
3.4. QoS Application Requirements . . . . . . . . . . . . . . . 14
4. QoS Application Session Establishment and Management . . . . . 17
4.1. Parties Involved . . . . . . . . . . . . . . . . . . . . . 17
4.2. Session Establishment . . . . . . . . . . . . . . . . . . 18
4.2.1. Session Establishment for Pull Mode . . . . . . . . . 18
4.2.2. Session Establishment for Push Mode . . . . . . . . . 21
4.2.3. Discovery and Selection of Peer Diameter QoS
Application Node . . . . . . . . . . . . . . . . . . . 24
4.3. Session Re-Authorization . . . . . . . . . . . . . . . . . 24
4.3.1. Client-Side Initiated Re-Authorization . . . . . . . . 25
4.3.2. Server-Side Initiated Re-Authorization . . . . . . . . 26
4.4. Session Termination . . . . . . . . . . . . . . . . . . . 28
4.4.1. Client-Side Initiated Session Termination . . . . . . 28
4.4.2. Server-Side Initiated Session Termination . . . . . . 28
5. QoS Application Messages . . . . . . . . . . . . . . . . . . . 29
5.1. QoS-Authorization Request (QAR) . . . . . . . . . . . . . 30
5.2. QoS-Authorization-Answer (QAA) . . . . . . . . . . . . . . 31
5.3. QoS-Install Request (QIR) . . . . . . . . . . . . . . . . 32
5.4. QoS-Install Answer (QIA) . . . . . . . . . . . . . . . . . 32
5.5. Re-Auth-Request (RAR) . . . . . . . . . . . . . . . . . . 33
5.6. Re-Auth-Answer (RAA) . . . . . . . . . . . . . . . . . . . 34
6. QoS Application State Machine . . . . . . . . . . . . . . . . 34
6.1. Supplemented States for Push Mode . . . . . . . . . . . . 34
7. QoS Application AVPs . . . . . . . . . . . . . . . . . . . . . 35
7.1. Reused Base Protocol AVPs . . . . . . . . . . . . . . . . 36
7.2. QoS Application-Defined AVPs . . . . . . . . . . . . . . . 36
8. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Sun, et al. Standards Track [Page 2]
RFC 5866 Diameter QoS Application May 2010
9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
9.1. Example Call Flow for Pull Mode (Success Case) . . . . . . 38
9.2. Example Call Flow for Pull Mode (Failure Case) . . . . . . 40
9.3. Example Call Flow for Push Mode . . . . . . . . . . . . . 43
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45
10.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 45
10.2. Application IDs . . . . . . . . . . . . . . . . . . . . . 45
10.3. Command Codes . . . . . . . . . . . . . . . . . . . . . . 46
11. Security Considerations . . . . . . . . . . . . . . . . . . . 46
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 47
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 47
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
14.1. Normative References . . . . . . . . . . . . . . . . . . . 48
14.2. Informative References . . . . . . . . . . . . . . . . . . 48
1. Introduction
This document describes the framework, messages, and procedures for
the Diameter [RFC3588] Quality-of-Service (QoS) application. The
Diameter QoS application allows Network Elements (NEs) to interact
with Diameter servers when allocating QoS resources in the network.
Two modes of operation are defined. In the first, called "Pull"
mode, the network element requests QoS authorization from the
Diameter server based on some trigger (such as a QoS signaling
protocol) that arrives along the data path. In the second, called
"Push" mode, the Diameter server proactively sends a command to the
network element(s) to install QoS authorization state. This could be
triggered, for instance, by off-path signaling, such as Session
Initiation Protocol (SIP) [RFC3261] call control.
A set of command codes is specified that allows a single Diameter QoS
application server to support both Pull and Push modes based on the
requirements of network technologies, deployment scenarios, and end-
host capabilities. In conjunction with Diameter Attribute Value
Pairs (AVPs) defined in [RFC5777] and in [RFC5624], this document
depicts basic call-flow procedures used to establish, modify, and
terminate a Diameter QoS application session.
This document defines a number of Diameter-encoded AVPs, which are
described using a modified version of the Augmented Backus-Naur Form
(ABNF), see [RFC3588].
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].
Sun, et al. Standards Track [Page 3]
RFC 5866 Diameter QoS Application May 2010
The following terms are used in this document:
AAA Cloud
An infrastructure of Authentication, Authorization, and Accounting
(AAA) entities (clients, agents, servers) communicating via a AAA
protocol over trusted, secure connections. It offers
authentication, authorization, and accounting services to
applications in local and roaming scenarios. Diameter and RADIUS
[RFC2865] are both widely deployed AAA protocols.
Application Endpoint (AppE)
An Application Endpoint is an entity in an end-user device that
exchanges signaling messages with Application Servers or directly
with other Application Endpoints. Based on the result of this
signaling, the endpoint may make a request for QoS from the
network. For example, a SIP User Agent is one kind of Application
Endpoint.
Application Server (AppS)
An Application Server is an entity that exchanges signaling
messages with an Application Endpoint (see above). It may be a
source of authorization for QoS-enhanced application flows. For
example, a SIP server is one kind of Application Server.
Authorizing Entity (AE)
The Authorizing Entity is a Diameter server that supports the QoS
application. It is responsible for authorizing QoS requests for a
particular application flow or aggregate. The Authorizing Entity
may be a standalone entity or may be integrated with an
Application Server and may be co-located with a subscriber
database. This entity corresponds to the Policy Decision Point
(PDP) [RFC2753].
Network Element (NE)
A QoS-aware router that acts as a Diameter client for the QoS
application. This entity triggers the protocol interaction for
Pull mode, and it is the recipient of QoS information in Push
mode. The Diameter client at a Network Element corresponds to the
Policy Enforcement Point (PEP) [RFC2753].
Pull Mode
In this mode, the QoS authorization process is invoked by the QoS
reservation request received from the Application Endpoint. The
Network Element then requests the QoS authorization decision from
the Authorizing Entity.
Sun, et al. Standards Track [Page 4]
RFC 5866 Diameter QoS Application May 2010
Push Mode
In this mode, the QoS authorization process is invoked by the
request from the Application Server or local policies in the
Authorizing Entity. The Authorizing Entity then installs the QoS
authorization decision to the Network Element directly.
Resource Requesting Entity (RRE)
A Resource Requesting Entity is a logical entity that supports the
protocol interaction for QoS resources. The RRE resides in the
end-host and is able to communicate with peer logical entities in
an Authorizing Entity or a Network Element to trigger the QoS
authorization process.
3. Framework
The Diameter QoS application runs between an NE (acting as a Diameter
client) and the resource AE (acting as a Diameter server). A high-
level picture of the resulting architecture is shown in Figure 1.
+-------+---------+
| Authorizing |
| Entity |
|(Diameter Server)|
+-------+---------+
|
|
/\-----+-----/\
//// \\\\
|| AAA Cloud ||
| (Diameter application) |
|| ||
\\\\ ////
\-------+-----/
|
+---+--+ +-----+----+ +---+--+
| | | NE | | | Media
+ NE +===+(Diameter +===+ NE +=============>>
| | | Client) | | | Flow
+------+ +----------+ +------+
Figure 1: An Architecture Supporting QoS-AAA
Figure 1 depicts NEs through which media flows need to pass, a cloud
of AAA servers, and an AE. Note that there may be more than one
router that needs to interact with the AAA cloud along the path of a
given application flow, although the figure only depicts one for
clarity.
Sun, et al. Standards Track [Page 5]
RFC 5866 Diameter QoS Application May 2010
In some deployment scenarios, NEs may request authorization through
the AAA cloud based on an incoming QoS reservation request. The NE
will route the request to a designated AE. The AE will return the
result of the authorization decision. In other deployment scenarios,
the authorization will be initiated upon dynamic application state,
so that the request must be authenticated and authorized based on
information from one or more AppSs. After receiving the
authorization request from the AppS or the NE, the AE decides the
appropriate mode (i.e., Push or Pull). The usage of Push or Pull
mode can be determined by the Authorizing Entity either statically or
dynamically. Static determination might be based on a configurable
defined policy in the Authorizing Entity, while dynamic determination
might be based on information received from an application server.
For Push mode, the Authorizing Entity needs to identify the
appropriate NE(s) to which QoS authorization information needs to be
pushed. It might determine this based on information received from
the AppS, such as the IP addresses of media flows.
In some deployment scenarios, there is a mapping between access
network type and the service logic (e.g., selection of Push or Pull
mode and other differentiated handling of the resource admission and
control). The access network type might be derived from the
authorization request from the AppS or the NE, and in this case, the
Authorizing Entity can identify the corresponding service logic based
on the mapping.
If the interface between the NEs and the AAA cloud is identical
regardless of whether or not the AE communicates with an AppS,
routers are insulated from the details of particular applications and
need not know that Application Servers are involved. Also, the AAA
cloud may also encompass business relationships such as those between
network operators and third-party application providers. This
enables flexible intra- or inter-domain authorization, accounting,
and settlement.
Sun, et al. Standards Track [Page 6]
RFC 5866 Diameter QoS Application May 2010
3.1. Network Element Functional Model
Figure 2 depicts a logical operational model of resource management
in a router.
+-------------------------------------------------------+
| DIAMETER Client |
| Functionality |
| +---------------++-----------------++---------------+ |
| | User || QoS Application || Accounting | |
| | Authentication|| Client || Client (e.g., | |
| | Client || (Authorization ||for QoS Traffic| |
| +---------------+| of QoS Requests)|+---------------+ |
| +-----------------+ |
+-------------------------------------------------------+
^
v
+--------------+ +----------+
|QoS Signaling | | Resource |
|Msg Processing|<<<<<>>>>>>>|Management|
+--------------+ +----------+
. ^ | * ^
| v . * ^
+-------------+ * ^
|Signaling msg| * ^
| 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: Network Element Functional Model
Sun, et al. Standards Track [Page 7]
RFC 5866 Diameter QoS Application May 2010
The processing of incoming QoS reservation requests includes three
actions: admission control, authorization, and resource reservation.
The admission control function provides information about available
resources and determines whether there are enough resources to
fulfill the request. Authorization is performed by the Diameter
client, which involves contacting an authorization entity through the
AAA cloud shown in Section 3. If both checks are successful, the
authorized QoS parameters are set in the packet classifier and the
packet scheduler. Note that the parameters passed to the Traffic
Control function may be different from the ones that requested QoS
(depending on the authorization decision). Once the requested
resource is granted, the Resource Management function provides
accounting information to the AE via the Diameter client.
3.2. Implications of Endpoint QoS Capabilities
3.2.1. Endpoint Categories
The QoS capabilities of Application Endpoints are varied, and can be
categorized as follows:
Category 1
A Category 1 Application Endpoint has no QoS capability at either
the application or the network level. This type of AppE may set
up a connection through application signaling, but it is incapable
of specifying resource/QoS requirements through either
application- or network-level signaling.
Category 2
A Category 2 Application Endpoint only has QoS capability at the
application level. This type of AppE is able to set up a
connection through application signaling with certain resource/QoS
requirements (e.g., application attributes), but it is unable to
signal any resource/QoS requirements at the network level.
Category 3
A Category 3 Application Endpoint has QoS capability at the
network level. This type of AppE may set up a connection through
application signaling, translate service characteristics into
network resource/QoS requirements (e.g., network QoS class)
locally, and request the resources through network signaling,
e.g., Resource ReSerVation Protocol (RSVP) [RFC2205] or Next Steps
in Signaling (NSIS) [NSIS-QOS].
Sun, et al. Standards Track [Page 8]
RFC 5866 Diameter QoS Application May 2010
3.2.2. Interaction Modes between the Authorizing Entity and Network
Element
Different QoS mechanisms are employed in packet networks. Those QoS
mechanisms can be categorized into two schemes: IntServ [RFC2211]
[RFC2212] and Diffserv [RFC2474]. In the IntServ scheme, network
signaling (e.g., RSVP, NSIS, or link-specific signaling) is commonly
used to initiate a request from an AppE for the desired QoS resource.
In the Diffserv scheme, QoS resources are provisioned based upon some
predefined QoS service classes rather than AppE-initiated, flow-based
QoS requests.
It is obvious that the eligible QoS scheme is correlated to the
AppE's capability in the context of QoS authorization. Since
Category 1 and 2 AppEs cannot initiate the QoS resource requests by
means of network signaling, using the current mechanism of the
IntServ model to signal QoS information across the network is not
applicable to them in general. Depending on network technology and
operator requirements, a Category 3 AppE may either make use of
network signaling for resource requests or not.
The diversity of QoS capabilities of endpoints and QoS schemes of
network technology leads to the distinction on the interaction mode
between the QoS authorization system and underlying NEs. When the
IntServ scheme is employed by a Category 3 endpoint, the
authorization process is typically initiated by an NE when a trigger
is received from the endpoint such as network QoS signaling. In the
Diffserv scheme, since the NE is unable to request the resource
authorization on its own initiative, the authorization process is
typically triggered by either the request of AppSs or policies
defined by the operator.
As a consequence, two interaction modes are needed in support of
different combinations of QoS schemes and endpoint's QoS
capabilities: Push mode and Pull mode.
Push mode
The QoS authorization process is triggered by AppSs or local
network conditions (e.g., time of day on resource usage and QoS
classes), and the authorization decisions are installed by the AE
to the network element on its own initiative without explicit
request. In order to support Push mode, the AE (i.e., Diameter
server) should be able to initiate a Diameter authorization
session to communicate with the NE (i.e., Diameter client) without
any preestablished connection from the network element.
Sun, et al. Standards Track [Page 9]
RFC 5866 Diameter QoS Application May 2010
Pull mode
The QoS authorization process is triggered by the network
signaling received from end-user equipment or by a local event in
the NE according to pre-configured policies, and authorization
decisions are produced upon the request of the NE. In order to
support Pull mode, the NE (i.e., Diameter client) will initiate a
Diameter authorization session to communicate with the Authorizing
Entity (i.e., Diameter server).
For Category 1 and 2 Application Endpoints, Push mode is REQUIRED.
For a Category 3 AppE, either Push mode or Pull mode MAY be used.
Push mode is applicable to certain networks, for example, Cable
network, DSL, Ethernet, and Diffserv-enabled IP/MPLS. Pull mode is
more appropriate to IntServ-enabled IP networks or certain wireless
networks such as the General Packet Radio Service (GPRS) networks
defined by the Third Generation Partnership Project (3GPP). Some
networks (for example, Worldwide Interoperability for Microwave
Access (WiMAX)) may require both Push and Pull modes.
3.3. Authorization Schemes
3.3.1. Pull Mode Schemes
Three types of basic authorization schemes for Pull mode exist: one
type of two-party scheme and two types of three-party schemes. The
notation adopted here is in respect to the entity that performs the
QoS authorization (QoS Authz). The authentication of the QoS
requesting entity might be done at the NE as part of the QoS
signaling protocol, or by an off-path protocol (on the application
layer or for network access authentication) or the AE might be
contacted with a request for authentication and authorization of the
QoS requesting entity. From the Diameter QoS application's point of
view, these schemes differ in type of information that need to be
carried. Here we focus on the "Basic Three-Party Scheme" (see
Figure 3) and the "Token-Based Three-Party Scheme" (see Figure 4).
In the "Two-Party Scheme", the QoS RRE is authenticated by the NE and
the authorization decision is made either locally at the NE itself or
offloaded to a trusted entity (most likely within the same
administrative domain). In the two-party case, no Diameter QoS
protocol interaction is required.
Sun, et al. Standards Track [Page 10]
RFC 5866 Diameter QoS Application May 2010
+--------------+
| Authorizing |
| Entity |
| authorizing | <......+
| resource | .
| request | .
+------------+-+ .
--^----------|-- . .
///// | | \\\\\ .
// | | \\ .
| QoS | QoS AAA | QoS |.
| authz| protocol |authz |.
| req.| | res. |.
\\ | | // .
\\\\\ | | ///// .
QoS --|----------v-- . .
+-------------+ request +-+------------+ .
| Entity |----------------->| NE | .
| requesting | | performing | .
| resource |granted / rejected| QoS | <.....+
| |<-----------------| reservation | financial
+-------------+ +--------------+ settlement
Figure 3: Three-Party Scheme
In the "Basic Three-Party Scheme", a QoS reservation request that
arrives at the NE is forwarded to the Authorizing Entity (e.g., in
the user's home network), where the authorization decision is made.
As shown, financial settlement -- a business relationship, such as a
roaming agreement -- between the visited network and the home network
ensures that the visited network is compensated for the resources
consumed by the user via the home network.
Sun, et al. Standards Track [Page 11]
RFC 5866 Diameter QoS Application May 2010
financial settlement
...........................+
Authorization V ------- .
Token Request +--------------+ / QoS AAA \ .
+-------------->| | / protocol \ .
| | Authorizing +--------------+ \ .
| | Entity | | | | .
| +------+ |<--+----+ | | .
| | +--------------+ |QoS | |QoS |.
| | |authz| |authz|.
| |Authorization |req.+| |res. |.
| |Token |Token| | |.
| | | | | . | .
| | \ | | . / .
| | \ | | / .
| | QoS request |-----V . .
+-------------+ + Authz Token +--------+-----+ .
| Entity |----------------->| NE | .
| requesting | | performing | .
| resource |granted / rejected| QoS | <....+
| |<-----------------| reservation |
+-------------+ +--------------+
Figure 4: Token-Based Three-Party Scheme
The "Token-Based Three-Party Scheme" is applicable to environments
where a previous protocol interaction is used to request
authorization tokens to assist the authorization process at the NE or
the AE [RFC3521].
The QoS RRE may be involved in an application-layer protocol
interaction, for example, using SIP [RFC3313], with the AE. As part
of this interaction, authentication and authorization at the
application layer might take place. As a result of a successful
authorization decision, which might involve the user's home AAA
server, an authorization token is generated by the AE (e.g., the SIP
proxy and an entity trusted by the SIP proxy) and returned to the
end-host for inclusion into the QoS signaling protocol. The
authorization token will be used by an NE that receives the QoS
signaling message to authorize the QoS request. Alternatively, the
Diameter QoS application will be used to forward the authorization
token to the user's home network. The authorization token allows for
the authorization decision performed at the application layer to be
associated with a corresponding QoS signaling session. Note that the
authorization token might either refer to established state
concerning the authorization decision or the token might itself carry
the authorized parameters (protected by a digital signature or a
keyed message digest to prevent tampering). In the latter case, the
Sun, et al. Standards Track [Page 12]
RFC 5866 Diameter QoS Application May 2010
authorization token may contain several pieces of information
pertaining to the authorized application session, but at minimum it
should contain:
o An identifier for the AE (for example, an AppS) that issued the
authorization token;
o An identifier referring to a specific application protocol session
for which the token was issued; and
o A keyed message digest or digital signature protecting the content
of the authorization token.
A possible structure for the authorization token and the policy
element carrying it are proposed in the context of RSVP [RFC3520].
In the scenario mentioned above, where the QoS resource requesting
entity is involved in an application-layer protocol interaction with
the AE, it may be worthwhile to consider a token-less binding
mechanism also. The application-layer protocol interaction may have
indicated the transport port numbers at the QoS RRE where it might
receive media streams (for example, in SIP/SDP [RFC4566] signaling,
these port numbers are advertised). The QoS RRE may also use these
port numbers in some IP filter indications to the NE performing QoS
reservation so that it may properly tunnel the inbound packets. The
NE performing QoS reservation will forward the QoS resource
requesting entity's IP address and the IP filter indications to the
AE in the QoS authorization request. The AE will use the QoS RRE's
IP address and the port numbers in the IP filter indication, which
will match the port numbers advertised in the earlier application-
layer protocol interaction, to identify the right piece of policy
information to be sent to the NE performing the QoS reservation in
the QoS Authorization response.
3.3.2. Push Mode Schemes
Push mode can be further divided into two types: endpoint-initiated
and network-initiated. In the former case, the authorization process
is triggered by AppS in response to an explicit QoS request from an
endpoint through application signaling, e.g., SIP; in the latter
case, the authorization process is triggered by the AppS without an
explicit QoS request from an endpoint.
In the endpoint-initiated scheme, the QoS RRE (i.e., the AppE)
determines the required application-level QoS and sends a QoS request
through an application signaling message. The AppS will extract
application-level QoS information and trigger the authorization
process to the AE. In the network-initiated scheme, the AE and/or
Sun, et al. Standards Track [Page 13]
RFC 5866 Diameter QoS Application May 2010
AppS should derive and determine the QoS requirements according to
application attribute, subscription, and endpoint capability when the
endpoint does not explicitly indicate the QoS attributes. The AE
makes an authorization decision based on application-level QoS
information, network policies, end-user subscription, network
resource availability, etc., and installs the decision to the NE
directly.
A Category 1 AppE requires network-initiated Push mode and a Category
2 AppE may use either type of Push Mode.
financial settlement
...........................+
Application V ------- .
signaling msg +--------------+ / QoS AAA \ .
+-------------->| | / protocol \ .
| | Authorizing +--------------+ \ .
| | Entity | | | | .
| + |<--+----+ | | .
| +--------------+ |QoS | |QoS |.
| install| |install
| |rsp. | |req. |.
| | | | |.
| | | | . | .
| \ | | . / .
| \ | | / .
V |-----V . .
+-------------+ +--------+-----+ .
| Entity | | NE | .
| requesting | | performing | .
| resource |QoS rsrc granted | QoS | <....+
| |<-----------------| reservation |
+-------------+ +--------------+
Figure 5: Scheme for Push Mode
3.4. QoS Application Requirements
A QoS application must meet a number of requirements applicable to a
diverse set of networking environments and services. It should be
compatible with different deployment scenarios having specific QoS
signaling models and security issues. Satisfying the requirements
listed below while interworking with QoS signaling protocols, a
Diameter QoS application should accommodate the capabilities of the
QoS signaling protocols rather than introduce functional requirements
on them. A list of requirements for a QoS authorization application
is provided here:
Sun, et al. Standards Track [Page 14]
RFC 5866 Diameter QoS Application May 2010
Identity-based Routing
The Diameter QoS application MUST route AAA requests to the
Authorizing Entity, based on the provided identity of the QoS
requesting entity or the identity of the AE encoded in the
provided authorization token.
Flexible Authentication Support
The Diameter QoS application MUST support a variety of different
authentication protocols for verification of authentication
information present in QoS signaling messages. The support for
these protocols MAY be provided indirectly by tying the signaling
communication for QoS to a previous authentication protocol
exchange (e.g., using network access authentication).
Making an Authorization Decision
The Diameter QoS application MUST exchange sufficient information
between the AE and the enforcing entity (and vice versa) to
compute an authorization decision and to execute this decision.
Triggering an Authorization Process
The Diameter QoS application MUST allow periodic and event-
triggered execution of the authorization process, originated at
the enforcing entity or even at the AE.
Associating QoS Reservations and Application State
The Diameter QoS application MUST carry information sufficient for
an AppS to identify the appropriate application session and
associate it with a particular QoS reservation.
Dynamic Authorization
It MUST be possible for the Diameter QoS application to push
updates towards the NE(s) from Authorizing Entities.
Bearer Gating
The Diameter QoS application MUST allow the AE to gate (i.e.,
enable/disable) authorized application flows based on, e.g.,
application state transitions.
Accounting Records
The Diameter QoS application MAY define QoS accounting records
containing duration, volume (byte count) usage information, and a
description of the QoS attributes (e.g., bandwidth, delay, loss
rate) that were supported for the flow.
Sending Accounting Records
The NE SHOULD be able to send accounting records for a particular
QoS reservation state to an accounting entity.
Sun, et al. Standards Track [Page 15]
RFC 5866 Diameter QoS Application May 2010
Failure Notification
The Diameter QoS application MUST allow the NE to report failures,
such as loss of connectivity due to movement of a mobile node or
other reasons for packet loss, to the Authorizing Entity.
Accounting Correlation
The Diameter QoS application MAY support the exchange of
sufficient information to allow for correlation between accounting
records generated by the NEs and accounting records generated by
an AppS.
Interaction with Other AAA Applications
Interaction with other AAA applications, such as the Diameter
Network Access Server Application [RFC4005], may be required for
exchange of authorization, authentication, and accounting
information.
In deployment scenarios where authentication of the QoS reservation
requesting entity (e.g., the user) is done by means outside the
Diameter QoS application protocol interaction, the AE is contacted
only with a request for QoS authorization. Authentication might have
taken place already via the interaction with the Diameter application
[RFC4005] or as part of the QoS signaling protocol (e.g., Transport
Layer Security (TLS) [RFC5246] in the General Internet Signaling
Transport (GIST) protocol [NSIS-NTLP]).
Authentication of the QoS reservation requesting entity to the AE is
necessary if a particular Diameter QoS application protocol cannot be
related (or if there is no intention to relate it) to a prior
authentication. In this case, the AE MUST authenticate the QoS
reservation requesting entity in order to authorize the QoS request
as part of the Diameter QoS protocol interaction.
This document refers to three types of sessions that need to be
properly correlated.
QoS Signaling Session
The time period during which a QoS signaling protocol establishes,
maintains, and deletes a QoS reservation state at the QoS network
element is referred to as a QoS signaling session. Different QoS
signaling protocols use different ways to identify QoS signaling
sessions. The same applies to different usage environments.
Currently, this document supports three types of QoS session
identifiers, namely a signaling session id (e.g., the Session
Identifier used by the NSIS protocol suite), a flow id (e.g.,
identifier assigned by an application to a certain flow as used in
the 3GPP), and a flow description based on the IP parameters of
the flow's endpoints.
Sun, et al. Standards Track [Page 16]
RFC 5866 Diameter QoS Application May 2010
Diameter Authorization Session
The time period for which a Diameter server authorizes a requested
service (i.e., QoS resource reservation) is referred to as a
Diameter authorization session. It is identified by a Session-Id
included in all Diameter messages used for management of the
authorized service (initial authorization, re-authorization,
termination), see [RFC3588].
Application-Layer Session
The application-layer session identifies the duration of an
application-layer service that requires provision of a certain
QoS. An application-layer session identifier is provided by the
QoS requesting entity in the QoS signaling messages, for example
as part of the authorization token. In general, the application
session identifier is opaque to the QoS-aware NEs. It is included
in the authorization request message sent to the AE and helps it
to correlate the QoS authorization request to the application
session state information.
Correlating these sessions is done at each of the three involved
entities: The QoS requesting entity correlates the application with
the QoS signaling sessions. The QoS NE correlates the QoS signaling
session with the Diameter authorization sessions. The AE SHOULD bind
the information about the three sessions together. Note that in
certain scenarios, not all of the sessions are present. For example,
the application session might not be visible to the QoS signaling
protocol directly if there is no binding between the application
session and the QoS requesting entity using the QoS signaling
protocol.
4. QoS Application Session Establishment and Management
4.1. Parties Involved
Authorization models supported by this application include three
parties:
o Resource Requesting Entity
o Network Elements (Diameter QoS application (DQA) client)
o Authorizing Entity (Diameter QoS application (DQA) server)
Note that the QoS RRE is only indirectly involved in the message
exchange. This entity provides the trigger to initiate the Diameter
QoS protocol interaction by transmitting QoS signaling messages. The
Diameter QoS application is only executed between the Network Element
(i.e., DQA client) and the Authorizing Entity (i.e., DQA server).
Sun, et al. Standards Track [Page 17]
RFC 5866 Diameter QoS Application May 2010
The QoS RRE may communicate with the AE using application-layer
signaling for the negotiation of service parameters. As part of this
application-layer protocol interaction, for example using SIP,
authentication and authorization might take place. This message
exchange is, however, outside the scope of this document. The
protocol communication between the QoS resource requesting entity and
the QoS NE might be accomplished using the NSIS protocol suite, RSVP,
or a link-layer signaling protocol. A description of these protocols
is also outside the scope of this document.
4.2. Session Establishment
Pull and Push modes use a different set of command codes for session
establishment. For other operations, such as session modification
and termination, they use the same set of command codes.
The selection of Pull mode or Push mode operation is based on the
trigger of the QoS authorization session. When a QoS-Authorization-
Request (QAR, see Section 5.1) message with a new Session-Id is
received, the AE operates in Pull mode; when other triggers are
received, the AE operates in Push mode. Similarly, when a QoS-
Install-Request (QIR, see Section 5.3} with a new Session-Id is
received, the NE operates in Push mode; when other triggers are
received, the NE operates in Pull mode.
The QoS authorization session is typically established per subscriber
base (i.e., all requests with the same User-ID), but it is also
possible to be established on a per node or per request base. The
concurrent sessions between an NE and an AE are identified by
different Session-Ids.
4.2.1. Session Establishment for Pull Mode
A request for a QoS reservation or local events received by an NE can
trigger the initiation of a Diameter QoS authorization session. The
NE converts the required objects from the QoS signaling message to
Diameter AVPs and generates a QAR message.
Figure 6 shows the protocol interaction between a Resource Requesting
Entity, a Network Element, and the Authorizing Entity.
The AE's identity, information about the application session and/or
identity and credentials of the QoS RRE, requested QoS parameters,
and the signaling session identifier and/or QoS-enabled data flows
identifiers MAY be encapsulated into respective Diameter AVPs and
included in the Diameter message sent to the AE. The QAR is sent to
a Diameter server that can be either the home server of the QoS
requesting entity or an AppS.
Sun, et al. Standards Track [Page 18]
RFC 5866 Diameter QoS Application May 2010
+------------------------------------------+------------------------+
| QoS-Specific Input Data | Diameter AVPs |
+------------------------------------------+------------------------+
| Authorizing Entity ID (e.g., | Destination-Host |
| Destination-Host taken from | Destination-Realm |
| authorization token, Destination-Realm, | |
| or derived from the Network Access | |
| Identifier (NAI) of the QoS requesting | |
| entity) | |
| Authorization Token Credentials of the | QoS-Authorization-Data |
| QoS requesting entity | User-Name |
| QoS-Resources (including QoS parameters) | |
+------------------------------------------+------------------------+
Table 1: Mapping Input Data to QoS AVPs -- Pull Mode
Authorization processing starts at the Diameter QoS server when it
receives the QAR. Based on the information in the QoS-
Authentication-Data, User-Name, and QoS-Resources AVPs, the server
determines the authorized QoS resources and flow state (enabled/
disabled) from locally available information (e.g., policy
information that may be previously established as part of an
application-layer signaling exchange or the user's subscription
profile). The QoS-Resources AVP is defined in [RFC5777]. The
authorization decision is then reflected in the response returned to
the Diameter client with the QoS-Authorization-Answer (QAA) message.
Sun, et al. Standards Track [Page 19]
RFC 5866 Diameter QoS Application May 2010
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
+---QoS-Reserve---->| |
| +- - - - - QAR - - - - - >|
| |(QoS-Resources, |
| | QoS-Auth-Data,User-ID)|
| | +--------+--------------+
| | | Authorize request |
| | | Keep session data |
| | |/Authz-time,Session-Id/|
| | +--------+--------------+
| |< - - - - QAA - - - - - -+
| |(Result-Code, |
| |QoS-Resources,Authz-time)|
| +-------+---------+
| |Install QoS state|
| | + |
| | Authz session |
| | /Authz-time/ | QoS Responder
| | | Node
| +-------+---------+ |
| +----------QoS-Reserve---....--->|
| | |
| |<---------QoS-Response--....----|
|<--QoS-Response----+ |
| | |
|=====================Data Flow==============....===>|
Figure 6: Initial QoS Request Authorization for Pull Mode
The Authorizing Entity keeps authorization session state and SHOULD
save additional information for management of the session (e.g.,
Signaling-Session-Id, authentication data) as part of the session
state information.
The final result of the authorization request is provided in the
Result-Code AVP of the QAA message sent by the Authorizing Entity.
In the case of successful authorization (i.e., Result-Code =
DIAMETER_LIMITED_SUCCESS (see Section 7.1)), information about the
authorized QoS resources and the status of the authorized flow
(enabled/disabled) is provided in the QoS-Resources AVP of the QAA
message. The QoS information provided via the QAA is installed by
the QoS Traffic Control function of the NE. The value
Sun, et al. Standards Track [Page 20]
RFC 5866 Diameter QoS Application May 2010
DIAMETER_LIMITED_SUCCESS indicates that the AE expects confirmation
via another QAR message for successful QoS resource reservation and
for final reserved QoS resources (see below).
One important piece of information returned from the Authorizing
Entity is the authorization lifetime (carried inside the QAA). The
authorization lifetime allows the NE to determine how long the
authorization decision is valid for this particular QoS reservation.
A number of factors may influence the authorized session duration,
such as the user's subscription plan or the currently available
credits at the user's account (see Section 8). The authorization
duration is time-based, as specified in [RFC3588]. For an extension
of the authorization period, a new QoS-Authorization-Request/Answer
message exchange SHOULD be initiated. Further aspects of QoS
authorization session maintenance are discussed in Sections 4.3, 4.4,
and 8.
The indication of a successful QoS reservation and activation of the
data flow is provided by the transmission of a QAR message, which
reports the parameters of the established QoS state: reserved
resources, duration of the reservation, and identification of the QoS
enabled flow/QoS signaling session. The Diameter QoS server
acknowledges the reserved QoS resources with the QA Answer (QAA)
message where the Result-Code is set to 'DIAMETER_SUCCESS'. Note
that the reserved QoS resources reported in this QAR message MAY be
different than those authorized with the initial QAA message, due to
the QoS-signaling-specific behavior (e.g., receiver-initiated
reservations with One-Path-With-Advertisements) or specific process
of QoS negotiation along the data path.
4.2.2. Session Establishment for Push Mode
The Diameter QoS server in the AE initiates a Diameter QoS
authorization session upon the request for a QoS reservation
triggered by application-layer signaling or by local events, and
generates a QoS-Install-Request (QIR) message to the Diameter QoS
client in the NE in which it maps required objects to Diameter
payload objects.
Figure 7 shows the protocol interaction between the AE, a Network
Element, and an RRE.
The NE's identity, information about the application session and/or
identity and credentials of the QoS resource requesting entity,
requested QoS parameters, and signaling session identifier and/or QoS
enabled data flows identifiers MAY be encapsulated into respective
Diameter AVPs and included in the Diameter message sent from a
Diameter QoS server in the Authorizing Entity to a Diameter QoS
Sun, et al. Standards Track [Page 21]
RFC 5866 Diameter QoS Application May 2010
client in the NE. This requires that the AE has knowledge of
specific information for allocating and identifying the NE that
should be contacted and the data flow for which the QoS reservation
should be established. This information can be statically configured
or dynamically discovered, see Section 4.2.3 for details.
+-----------------------------------------+-------------------------+
| QoS-Specific Input Data | Diameter AVPs |
+-----------------------------------------+-------------------------+
| Network Element ID | Destination-Host |
| | Destination-Realm |
| Authorization Token Credentials of the | QoS-Authorization-Data |
| QoS requesting entity | User-Name |
| QoS-Resources (including QoS | |
| parameters) | |
+-----------------------------------------+-------------------------+
Table 2: Mapping Input Data to QoS AVPs -- Push Mode
Authorization processing starts at the Diameter QoS server when it
receives a request from an RRE through an AppS (e.g., SIP Invite) or
is triggered by a local event (e.g., a pre-configured timer). Based
on the received information, the server determines the authorized QoS
resources and flow state (enabled/disabled) from locally available
information (e.g., policy information that may be previously
established as part of an application-layer signaling exchange, or
the user's subscription profile). The authorization decision is then
reflected in the QoS-Install-Request (QIR) message to the Diameter
QoS client.
Sun, et al. Standards Track [Page 22]
RFC 5866 Diameter QoS Application May 2010
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
| | |<-- Trigger --
| | +--------+--------------+
| | | Authorize request |
| | | Keep session data |
| | |/Authz-time,Session-Id/|
| | +--------+--------------+
| | |
| |<-- - -- - QIR - - - - - -+
| |(Initial Request,Decision |
| |(QoS-Resources,Authz-time)|
| +-------+---------+
| |Install QoS state|
| | + |
| | Authz session |
| | /Authz-time/ |
| | |
| +-------+---------+
| + - - - - QIA - - - - - ->|
| | (Result-Code, |
| | QoS-Resources) |
| | +--------+--------------+
| | | Report for successful |
| | | QoS reservation |
| | |Update of reserved QoS |
| | | resources |
| | +--------+--------------+
| | QoS Responder
| | Node
| | |
|=====================Data Flow==============....===>|
Figure 7: Initial QoS Request Authorization for Push Mode
The AE keeps authorization session state and SHOULD save additional
information for management of the session (e.g.,
Signaling-Session-Id, authentication data) as part of the session
state information.
The final result of the authorization decision is provided in the
QoS-Resources AVP of the QIR message sent by the AE. The QoS
information provided via the QIR is installed by the QoS Traffic
Control function of the NE.
Sun, et al. Standards Track [Page 23]
RFC 5866 Diameter QoS Application May 2010
One important piece of information from the AE is the authorization
lifetime (carried inside the QIR). The authorization lifetime allows
the NE to determine how long the authorization decision is valid for
this particular QoS reservation. A number of factors may influence
the authorized session duration, such as the user's subscription plan
or the currently available credits at the user's account (see
Section 8). The authorization duration is time-based as specified in
[RFC3588]. For an extension of the authorization period, a new QoS-
Install-Request/Answer message or QoS-Authorization-Request/Answer
message exchange SHOULD be initiated. Further aspects of QoS
authorization session maintenance are discussed in Sections 4.3, 4.4,
and 8.
The indication of QoS reservation and activation of the data flow can
be provided by the QoS-Install-Answer message immediately. In the
case of successful enforcement, the Result-Code (= DIAMETER_SUCCESS,
(see Section 7.1)) information is provided in the QIA message. Note
that the reserved QoS resources reported in the QIA message may be
different than those initially authorized with the QIR message, due
to the QoS signaling-specific behavior (e.g., receiver-initiated
reservations with One-Path-With-Advertisements) or specific process
of QoS negotiation along the data path. In the case that Multiple
AEs control the same NE, the NE should make the selection on the
authorization decision to be enforced based on the priority of the
request.
4.2.3. Discovery and Selection of Peer Diameter QoS Application Node
The Diameter QoS application node may obtain information of its peer
nodes (e.g., Fully-Qualified Domain Name (FQDN), IP address) through
static configuration or dynamic discovery as described in Section 5.2
of [RFC3588]. In particular, the NE shall perform the relevant
operation for Pull mode; the AE shall perform the relevant operations
for Push mode.
Upon receipt of a trigger to initiate a new Diameter QoS
authorization session, the Diameter QoS application node selects and
retrieves the location information of the peer node that is
associated with the affected user based on some index information
provided by the RRE. For instance, it can be the Authorization
Entity's ID stored in the authorization token, the end-user identity
(e.g., NAI [RFC4282]), or a globally routable IP address.
4.3. Session Re-Authorization
Client- and server-side initiated re-authorizations are considered in
the design of the Diameter QoS application. Whether the
re-authorization events are transparent for the resource requesting
Sun, et al. Standards Track [Page 24]
RFC 5866 Diameter QoS Application May 2010
entity or result in specific actions in the QoS signaling protocol is
outside the scope of the Diameter QoS application. It is directly
dependent on the capabilities of the QoS signaling protocol.
There are a number of options for policy rules according to which the
NE (AAA client) contacts the AE for re-authorization. These rules
depend on the semantics and contents of the QAA message sent by the
AE:
a. The QAA message contains the authorized parameters of the flow
and its QoS and sets their limits (presumably upper). With these
parameters, the AE specifies the services that the NE can provide
and for which it will be financially compensated. Therefore, any
change or request for change of the parameters of the flow and
its QoS that do not conform to the authorized limits requires
contacting the AE for authorization.
b. The QAA message contains authorized parameters of the flow and
its QoS. The rules that determine whether parameters' changes
require re-authorization are agreed out of band, based on a
Service Level Agreement (SLA) between the domains of the NE and
the AE.
c. The QAA message contains the authorized parameters of the flow
and its QoS. Any change or request for change of these
parameters requires contacting the AE for re-authorization.
d. In addition to the authorized parameters of the flow and its QoS,
the QAA message contains policy rules that determine the NEs
actions in case of a change or a request for change in authorized
parameters.
Provided options are not exhaustive. Elaborating on any of the
listed approaches is deployment/solution specific and is not
considered in the current document.
In addition, the AE may use an RAR (Re-Authorization-Request) to
perform re-authorization with the authorized parameters directly when
the re-authorization is triggered by service request or local events/
policy rules.
4.3.1. Client-Side Initiated Re-Authorization
The AE provides the duration of the authorization session as part of
the QoS-Authorization-Answer (QAA) message. At any time before the
expiration of this period, a new QoS-Authorization-Request (QAR)
message MAY be sent to the AE. The transmission of the QAR MAY be
triggered when the NE receives a QoS signaling message that requires
Sun, et al. Standards Track [Page 25]
RFC 5866 Diameter QoS Application May 2010
modification of the authorized parameters of an ongoing QoS session,
or authorization lifetime expires.
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
|=====================Data Flow==========================>
| | |
| +-------+----------+ |
| |Authz-time/CC-Time| |
| | expires | |
| +-------+----------+ |
| +- - - - - QAR - - - - - >|
| |(QoS-Resources, |
| | QoS-Authorization-Data,User-ID) |
| +--------+--------------+
NOTE: | | Authorize request |
Re-authorization | | Update session data |
is transparent to | |/Authz-time,Session-Id/|
the End-Host | +--------+--------------+
|< - - - - QAA - - - - - -+
| |(Result-Code, |
| |QoS-Resources,Authz-time)|
| +-------+---------+ |
| |Update QoS state | |
| | + | |
| | Authz session | |
| | /Authz-time/ | |
| | | |
| +-------+---------+ |
| | |
|=====================Data Flow==========================>
| |
Figure 8: Client-side Initiated QoS Re-Authorization
4.3.2. Server-Side Initiated Re-Authorization
The AE MAY initiate a QoS re-authorization by issuing a
Re-Authorization-Request (RAR) message as defined in the Diameter
base protocol [RFC3588], which may include the parameters of the
re-authorized QoS state: reserved resources, duration of the
reservation, identification of the QoS-enabled flow/QoS signaling
session for re-installation of the resource state by the QoS Traffic
Control function of the NE.
Sun, et al. Standards Track [Page 26]
RFC 5866 Diameter QoS Application May 2010
An NE that receives such an RAR message with Session-Id matching a
currently active QoS session acknowledges the request by sending the
Re-Auth-Answer (RAA) message towards the AE.
If the RAR does not include any parameters of the re-authorized QoS
state, the NE MUST initiate a QoS re-authorization by sending a
QoS-Authorization-Request (QAR) message towards the AE.
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
| | |<-- Trigger --
| | +--------+--------------+
| | | Authorize request |
| | | Keep session data |
| | |/Authz-time,Session-Id/|
| | +--------+--------------+
| | |
| |<-- - -- - RAR - - - - - -+
| |(Request,Decision |
| |(QoS-Resources,Authz-time)|
| +-------+---------+
| |Install QoS state|
| | + |
| | Authz session |
| | /Authz-time/ |
| | |
| +-------+---------+
| + - - - - RAA - - - - - ->|
| | (Result-Code, |
| | QoS-Resources) |
| | +--------+--------------+
| | | Report for successful |
| | | QoS reservation |
| | |Update of reserved QoS |
| | | resources |
| | +--------+--------------+
| | |
Figure 9: Server-Side Initiated QoS Re-Authorization
Sun, et al. Standards Track [Page 27]
RFC 5866 Diameter QoS Application May 2010
4.4. Session Termination
4.4.1. Client-Side Initiated Session Termination
The authorization session for an installed QoS reservation state MAY
be terminated by the Diameter client by sending a Session-
Termination-Request (STR) message to the Diameter server with a
response Session-Termination-Acknowledgement (STA) message. This is
a Diameter base protocol function and it is defined in [RFC3588].
Session termination can be caused by a QoS signaling message
requesting deletion of the existing QoS reservation state, or it can
be caused as a result of a soft-state expiration of the QoS
reservation state.
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
|==Data Flow==>X /Stop of the data flow/ |
| | |
+---QoS-Reserve---->| |
| (Delete QoS +- - - - - STR - - - - - >|
| reservation) | +--------+--------------+
| | | Remove authorization |
| | | session state |
| | +--------+--------------+
| |< - - - - STA - - - - - -+
| +-------+--------+ |
| |Delete QoS state|
| +-------+--------+ QoS Responder
| | Node
| +----------QoS-Reserve-----....--->|
| | (Delete QoS |
| | reservation) |
| |<---------QoS-Response----....----+
|<--QoS-Response----+ |
Figure 10: Client-Side Initiated Session Termination
4.4.2. Server-Side Initiated Session Termination
At any time during a session, the AE MAY send an Abort-Session-
Request (ASR) message to the NE. This is a Diameter base protocol
function and it is defined in [RFC3588]. Possible reasons for
initiating the ASR message to the NE are insufficient credits or
session termination at the application layer. The ASR message
results in termination of the authorized session, release of the
Sun, et al. Standards Track [Page 28]
RFC 5866 Diameter QoS Application May 2010
reserved resources at the NE, and transmission of an appropriate QoS
signaling message indicating a notification to other Network Elements
aware of the signaling session.
Authorizing
End-Host Network Element Entity
requesting QoS (Diameter (Diameter
QoS Client) QoS Server)
| | |
|=====================Data Flow==========================>
| |
| |< - - - - ASR - - - - - -+
| | |
|====Data Flow=====>X | QoS Responder
| | | Node
|<--QoS-Notify------+----------QoS-Reserve-----....--->|
| | (Delete QoS | |
| reservation) |
+-------+--------+ |
|Delete QoS state| |
+-------+--------+ |
+- - - - - ASA - - - - - >|
| +--------+--------------+
| | Remove authorization |
| | session state |
| +--------+--------------+
| QoS Responder
| Node
|<---------QoS-Response----....----+
| |
Figure 11: Server-Side Initiated Session Termination
5. QoS Application Messages
The Diameter QoS application requires the definition of new mandatory
AVPs and Command-Codes (see Section 3 of [RFC3588]). Four new
Diameter messages are defined along with Command-Codes whose values
MUST be supported by all Diameter implementations that conform to
this specification.
Sun, et al. Standards Track [Page 29]
RFC 5866 Diameter QoS Application May 2010
+---------------------------+---------+------+-------------+
| Command Name | Abbrev. | Code | Reference |
+---------------------------+---------+------+-------------+
| QoS-Authorization-Request | QAR | 326 | Section 5.1 |
| QoS-Authorization-Answer | QAA | 326 | Section 5.2 |
| QoS-Install-Request | QIR | 327 | Section 5.3 |
| QoS-Install-Answer | QIA | 327 | Section 5.4 |
+---------------------------+---------+------+-------------+
Table 3: Diameter QoS Commands
In addition, the following Diameter base protocol messages are used
in the Diameter QoS application:
+-----------------------+---------+------+-----------+
| Command-Name | Abbrev. | Code | Reference |
+-----------------------+---------+------+-----------+
| Re-Auth-Request | RAR | 258 | [RFC3588] |
| Re-Auth-Answer | RAA | 258 | [RFC3588] |
| Abort-Session-Request | ASR | 274 | [RFC3588] |
| Abort-Session-Answer | ASA | 274 | [RFC3588] |
| Session-Term-Request | STR | 275 | [RFC3588] |
| Session-Term-Answer | STA | 275 | [RFC3588] |
+-----------------------+---------+------+-----------+
Table 4: Diameter Base Commands
Diameter nodes conforming to this specification MAY advertise support
for the Diameter QoS application by including the value of 9 in the
Auth-Application-Id or the Acct-Application-Id AVP of the
Capabilities-Exchange-Request and Capabilities-Exchange-Answer
commands, see [RFC3588].
The value of 9 MUST be used as the Application-Id in all QAR/QAA and
QIR/QIA commands.
The value of zero (0) SHOULD be used as the Application-Id in all
STR/STA, ASR/ASA, and RAR/RAA commands.
5.1. QoS-Authorization Request (QAR)
The QoS-Authorization-Request (QAR) message, indicated by the
Command-Code field (see Section 3 of [RFC3588]) being set to 326 and
the 'R' bit being set in the Command Flags field, is used by NEs to
request quality of service related resource authorization for a given
flow.
Sun, et al. Standards Track [Page 30]
RFC 5866 Diameter QoS Application May 2010
The QAR message MUST carry information for signaling session
identification, AE identification, information about the requested
QoS, and the identity of the QoS requesting entity. In addition,
depending on the deployment scenario, an authorization token and
credentials of the QoS requesting entity SHOULD be included.
The message format is defined as follows:
<QoS-Authorization-Request> ::= < Diameter Header: 326, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Request-Type }
[ Destination-Host ]
[ User-Name ]
* [ QoS-Resources ]
[ QoS-Authorization-Data ]
[ Bound-Auth-Session-Id ]
* [ AVP ]
5.2. QoS-Authorization-Answer (QAA)
The QoS-Authorization-Answer (QAA) message, indicated by the Command-
Code field being set to 326 and the 'R' bit being cleared in the
Command Flags field, is sent in response to the QoS-Authorization-
Request (QAR) message. If the QoS authorization request is
successfully authorized, the response will include the AVPs to allow
authorization of the QoS resources and transport plane gating
information.
The message format is defined as follows:
<QoS-Authorization-Answer> ::= < Diameter Header: 326, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Request-Type }
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
* [ QoS-Resources ]
[ Acct-Multisession-Id ]
[ Session-Timeout ]
[ Authorization-Session-Lifetime ]
[ Authorization-Grace-Period ]
* [ AVP ]
Sun, et al. Standards Track [Page 31]
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5.3. QoS-Install Request (QIR)
The QoS-Install Request (QIR) message, indicated by the Command-Code
field being set to 327 and the 'R' bit being set in the Command Flags
field, is used by the AE to install or update the QoS parameters and
the flow state of an authorized flow at the transport plane element.
The message MUST carry information for signaling-session
identification or identification of the flow to which the provided
QoS rules apply, identity of the transport plane element, description
of provided QoS parameters, flow state, and duration of the provided
authorization.
The message format is defined as follows:
<QoS-Install-Request> ::= < Diameter Header: 327, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Request-Type }
[ Destination-Host ]
* [ QoS-Resources ]
[ Session-Timeout ]
[ Authorization-Session-Lifetime ]
[ Authorization-Grace-Period ]
[ Authorization-Session-Volume ]
* [ AVP ]
5.4. QoS-Install Answer (QIA)
The QoS-Install Answer (QIA) message, indicated by the Command-Code
field being set to 327 and the 'R' bit being cleared in the Command
Flags, field is sent in response to the QoS-Install Request (QIR)
message for confirmation of the result of the installation of the
provided QoS reservation instructions.
The message format is defined as follows:
<QoS-Install-Answer> ::= < Diameter Header: 327, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Result-Code }
* [ QoS-Resources ]
* [ AVP ]
Sun, et al. Standards Track [Page 32]
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5.5. Re-Auth-Request (RAR)
The Re-Auth-Request (RAR) message, indicated by the Command-Code
field being set to 258 and the 'R' bit being set in the Command Flags
field, is sent by the AE to the NE in order to initiate the QoS
re-authorization from the DQA server side.
If the RAR command is received by the NE without any parameters of
the re-authorized QoS state, the NE MUST initiate a QoS
re-authorization by sending a QoS-Authorization-Request (QAR) message
towards the AE.
The message format is defined as follows:
<RAR> ::= < Diameter Header: 258, REQ, PXY >
< Session-Id >
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
{ Auth-Application-Id }
{ Re-Auth-Request-Type }
[ User-Name ]
[ Origin-State-Id ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ QoS-Resources ]
[ Session-Timeout ]
[ Authorization-Session-Lifetime ]
[ Authorization-Grace-Period ]
[ Authorization-Session-Volume ]
* [ AVP ]
Sun, et al. Standards Track [Page 33]
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5.6. Re-Auth-Answer (RAA)
The Re-Auth-Answer (RAA) message, indicated by the Command-Code field
being set to 258 and the 'R' bit being cleared in the Command Flags
field, is sent by the NE to the AE in response to the RAR command.
The message format is defined as follows:
<RAA> ::= < Diameter Header: 258, PXY >
< Session-Id >
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
[ User-Name ]
[ Origin-State-Id ]
[ Error-Message ]
[ Error-Reporting-Host ]
* [ Failed-AVP ]
* [ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Host-Max-Cache-Time ]
* [ Proxy-Info ]
* [ QoS-Resources ]
* [ AVP ]
6. QoS Application State Machine
The QoS application defines its own state machine that is based on
the authorization state machine defined in Section 8.1 of the
Diameter base protocol ([RFC3588]). The QoS state machine uses its
own messages, as defined in Section 5, and QoS AVPs, as defined in
Section 7.
6.1. Supplemented States for Push Mode
Using the Diameter base protocol state machine as a basis, the
following states are supplemented to the first two state machines in
which the session state is maintained on the server. These MUST be
supported in any QoS application implementations in support of
server-initiated Push mode (see Section 4.2.2).
Sun, et al. Standards Track [Page 34]
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The following states are supplemented to the state machine on the
server when state is maintained on the client, as defined in Section
8.1 of the Diameter base protocol[RFC3588]:
SERVER, STATEFUL
State Event Action New State
-------------------------------------------------------------
Idle An application or local Send Pending
event triggers an initial QIR initial
QoS request to the server request
Pending Received QIA with a failed Clean up Idle
Result-Code
Pending Received QIA with Result-Code Update Open
= SUCCESS session
Pending Error in processing received Send Discon
QIA with Result-Code = SUCCESS ASR
The following states are supplemented to the state machine on the
client when state is maintained on the server, as defined in Section
8.1 of the Diameter base protocol [RFC3588]:
CLIENT, STATEFUL
State Event Action New State
-------------------------------------------------------------
Idle QIR initial request Send Open
received and successfully QIA initial
processed answer,
reserve
resources
Idle QIR initial request Send Idle
received but not QIA initial
successfully processed answer with
Result-Code
!= SUCCESS
7. QoS Application AVPs
Each of the AVPs identified in the QoS-Authorization-Request/Answer
and QoS-Install-Request/Answer messages and the assignment of their
value(s) is given in this section.
Sun, et al. Standards Track [Page 35]
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7.1. Reused Base Protocol AVPs
The QoS application uses a number of session management AVPs, defined
in the base protocol ([RFC3588]).
Attribute Name AVP Code Reference [RFC3588]
Origin-Host 264 Section 6.3
Origin-Realm 296 Section 6.4
Destination-Host 293 Section 6.5
Destination-Realm 283 Section 6.6
Auth-Application-Id 258 Section 6.8
Result-Code 268 Section 7.1
Auth-Request-Type 274 Section 8.7
Session-Id 263 Section 8.8
Authorization-Lifetime 291 Section 8.9
Auth-Grace-Period 276 Section 8.10
Session-Timeout 27 Section 8.13
User-Name 1 Section 8.14
The Auth-Application-Id AVP (AVP Code 258) is assigned by IANA to
Diameter applications. The value of the Auth-Application-Id for the
Diameter QoS application is 9.
7.2. QoS Application-Defined AVPs
This document reuses the AVPs defined in Section 4 of [RFC5777].
This section lists the AVPs that are introduced specifically for the
QoS application. The following new AVPs are defined: Bound-Auth-
Session-Id and the QoS-Authorization-Data AVP.
The following table describes the Diameter AVPs newly defined in this
document for use with the QoS Application, their AVP code values,
types, possible flag values, and to determine whether the AVP may be
encrypted.
Sun, et al. Standards Track [Page 36]
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+-------------------+
| AVP Flag rules |
+----------------------------------------------|----+--------+-----+
| AVP Section | | SHLD| MUST|
| Attribute Name Code Defined Data Type |MUST| NOT| NOT|
+----------------------------------------------+----+--------+-----+
|QoS-Authorization-Data 579 7.2 OctetString| M | | V |
|Bound-Auth-Session-Id 580 7.2 UTF8String | M | | V |
+----------------------------------------------+----+--------+-----+
|M - Mandatory bit. An AVP with the "M" bit set and its value MUST |
| be supported and recognized by a Diameter entity in order for |
| the message, which carries this AVP, to be accepted. |
|V - Vendor-specific bit that indicates whether the AVP belongs to |
| an address space. |
+------------------------------------------------------------------+
QoS-Authorization-Data
The QoS-Authorization-Data AVP (AVP Code 579) is of type
OctetString. It is a container that carries application-session
or user-specific data that has to be supplied to the AE as input
to the computation of the authorization decision.
Bound-Authentication-Session-Id
The Bound-Authentication-Session AVP (AVP Code 580) is of type
UTF8String. It carries the ID of the Diameter authentication
session that is used for the network access [RFC4005]. It is used
to tie the QoS authorization request to a prior authentication of
the end-host done by a co-located application for network access
authentication ([RFC4005]) at the QoS NE.
8. Accounting
An NE MAY start an accounting session by sending an Accounting-
Request (ACR) message after successful QoS reservation and activation
of the data flow (see Figures 6 and 7). After every successful re-
authorization procedure (see Figures 8 and 9), the NE MAY initiate an
interim accounting message exchange. After successful session
termination (see Figures 10 and 11), the NE may initiate a final
exchange of accounting messages for the termination of the accounting
session and report final records for the use of the QoS resources
reserved. It should be noted that the two sessions (authorization
and accounting) have independent management by the Diameter base
protocol, which allows for finalizing the accounting session after
the end of the authorization session.
The detailed QoS accounting procedures are out of scope in this
document.
Sun, et al. Standards Track [Page 37]
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9. Examples
9.1. Example Call Flow for Pull Mode (Success Case)
This section presents an example of the interaction between the end-
host and Diameter QoS application entities using Pull mode. The
application-layer signaling is, in this example, provided using SIP.
Signaling for a QoS resource reservation is done using the QoS NSIS
Signaling Layer Protocol (NSLP). The authorization of the QoS
reservation request is done by the Diameter QoS application (DQA).
End-Host SIP Proxy Correspondent
requesting QoS (DQA Server) Node
| | |
..|....Application-layer SIP signaling.......|..............|..
. | Invite (SDP) | | .
. +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-> | .
. | 100 Trying | | .
. <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+ Invite (SDP)| .
. | +-.-.-.....-.-.> .
. | | 180 SDP' | .
. | <-.-.-.....-.-.+ .
. | +--------+--------+ | .
. | |Authorize session| | .
. | | parameters | | .
. | 180 (Session parameters) +--------+--------+ | .
. <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+ | .
..|..........................................|... ..........|..
| | |
| +------------+ | |
| | NE | | |
| |(DQA Client)| | |
| +------+-----+ | |
| | | |
|QoS NSLP Reserve | | |
+------------------> QAR | |
| (POLICY_DATA>v +- - - - -<<AAA>>- - - -> |
| QSPEC) v >===>(Destination-Host, | |
| v >=======>QoS-Authorization-Data++------------+ |
| >===========>QoS-Resources) |Authorize | |
| | |QoS resources| |
| | ++------------+ |
| | QAA | |
| <- - - - -<<AAA>>- - - -+ |
| |(Result-Code, | |
| |QoS-Resources, | |
| |Authorization-Lifetime)| |
Sun, et al. Standards Track [Page 38]
RFC 5866 Diameter QoS Application May 2010
| +---------+--------+ | |
| |Install QoS state1| | |
| |+ Authz session | | |
| +---------+--------+ | |
| |QoS NSLP Reserve |
| +---------------..............--------->
| | |
| | QoS NSLP Response|
|QoS NSLP Response <---------------..............---------+
<------------------+ |
| | QoS NSLP Query|
|QoS NSLP Query <---------------..............---------+
<------------------+ |
|QoS NSLP Reserve | |
+------------------> QAR | |
| +- - - - -<<AAA>>- - - -> |
| | +---+---------+ |
| | |Authorize | |
| | |QoS resources| |
| | QAA +---+---------+ |
| <- - - - -<<AAA>>- - - -+ |
| +---------+--------+ | |
| |Install QoS state2| |
| |+ Authz session | |
| +---------+--------+ |
| | QoS NSLP Reserve |
| +---------------..............--------->
| | QoS NSLP Response|
|QoS NSLP Response <---------------..............---------+
<------------------+ |
| | |
/------------------+--Data Flow---------------------------\
\------------------+--------------------------------------/
| | |
.-.-.-.-. SIP signaling
--------- QoS NSLP signaling
- - - - - Diameter QoS Application messages
========= Mapping of objects between QoS and AAA protocol
Figure 12: QoS Authorization Example - Pull Mode
Sun, et al. Standards Track [Page 39]
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The communication starts with SIP signaling between the two endpoints
and the SIP proxy for negotiation and authorization of the requested
service and its parameters (see Figure 12). As a part of the
process, the SIP proxy verifies whether the user at Host A is
authorized to use the requested service (and potentially the ability
to be charged for the service usage). Negotiated session parameters
are provided to the end-host.
Subsequently, Host A initiates a QoS signaling message towards Host
B. It sends a QoS NSLP Reserve message, in which it includes
description of the required QoS (QSPEC object) and authorization data
for negotiated service session (part of the POLICY_DATA object).
Authorization data includes, as a minimum, the identity of the AE
(e.g., the SIP proxy) and an identifier of the application-service
session for which QoS resources are requested.
A QoS NSLP reserve message is intercepted and processed by the first
QoS-aware Network Element. The NE uses the Diameter QoS application
to request authorization for the received QoS reservation request.
The identity of the AE (in this case, the SIP server that is co-
located with a Diameter server) is put into the Destination-Host AVP,
any additional session authorization data is encapsulated into the
QoS-Authorization-Data AVP, and the description of the QoS resources
is included into the QoS-Resources AVP. These AVPs are included into
a QoS Authorization Request message, which is sent to the AE.
A QAR message will be routed through the AAA network to the AE. The
AE verifies the requested QoS against the QoS resources negotiated
for the service session and replies with a QoS-Authorization-Answer
(QAA) message. It carries the authorization result (Result-Code AVP)
and the description of the authorized QoS parameters (QoS-Resources
AVP), as well as duration of the authorization session
(Authorization-Lifetime AVP).
The NE interacts with the Traffic Control function and installs the
authorized QoS resources and forwards the QoS NSLP reserve message
farther along the data path. Moreover, the NE may serve as a
signaling proxy and process the QoS signaling (e.g., initiation or
termination of QoS signaling) based on the QoS decision received from
the Authorizing Entity.
9.2. Example Call Flow for Pull Mode (Failure Case)
This section repeats the scenario outlined in Section 9.1; however,
in this case, we show a session authorization failure instead of
success. Failures can occur in various steps throughout the protocol
execution, and in this example, we assume that the Diameter QAR
request processed by the Diameter server leads to an unsuccessful
Sun, et al. Standards Track [Page 40]
RFC 5866 Diameter QoS Application May 2010
result. The QAA message responds, in this example, with a permanent
error "DIAMETER_AUTHORIZATION_REJECTED" (5003) set in the Result-Code
AVP. When the NE receives this response, it discontinues the QoS
reservation signaling downstream and provides an error message back
to the end-host that initiated the QoS signaling request. The QoS
NSLP response signaling message would in this case carry an INFO_SPEC
object indicating the permanent failure as "Authorization failure"
(0x02).
Sun, et al. Standards Track [Page 41]
RFC 5866 Diameter QoS Application May 2010
End-Host SIP Proxy Correspondent
requesting QoS (DQA Server) Node
| | |
..|...................SIP Signaling..........|..............|..
. | Invite (SDP) | | .
. +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-> | .
. | 100 Trying | | .
. <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+ Invite (SDP)| .
. | +-.-.-.....-.-.> .
. | | 180 SDP' | .
. | <-.-.-.....-.-.+ .
. | +--------+--------+ | .
. | |Authorize session| | .
. | | parameters | | .
. | 180 (Session parameters) +--------+--------+ | .
. <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+ | .
..|..........................................|... ..........|..
| | |
| +------------+ | |
| | NE | | |
| |(DQA Client)| | |
| +------+-----+ | |
| | | |
|QoS NSLP Reserve | | |
+------------------> QAR | |
| (POLICY_DATA>v +- - - - -<<AAA>>- - - -> |
| QSPEC) v >===>(Destination-Host, | |
| v >=======>QoS-Authorization-Data++------------+ |
| >===========>QoS-Resources) |Authorize | |
| | |QoS resources| |
| | ++------------+ |
| | QAA | |
| <- - - - -<<AAA>>- - - -+ |
| |(Result-Code = 5003) | |
| | | |
|QoS NSLP Response | | |
|(with error 0x02) | | |
<------------------+ | |
| | | |
| | | |
.-.-.-.-. SIP signaling
--------- QoS NSLP signaling
- - - - - Diameter QoS Application messages
========= Mapping of objects between QoS and AAA protocol
Figure 13: QoS Authorization Example - Pull Mode (Failure Case)
Sun, et al. Standards Track [Page 42]
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9.3. Example Call Flow for Push Mode
This section presents an example of the interaction between the end-
host and Diameter QoS application entities using Push mode. The
application-layer signaling is, in this example, provided using SIP.
Signaling for a QoS resource reservation is done using the QoS NSLP.
The authorization of the QoS reservation request is done by the
Diameter QoS application (DQA).
End-Host NE SIP Proxy Correspondent
requesting QoS (DQA Client) (DQA Server) Node
| | | |
..|..................|...SIP Signaling..........|..............|..
. | Invite(SDP Offer)| | | .
. +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+-.-.-.-.-.-.->| .
. | | | 180 | .
. |<-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+-.-.-.-.-.-.-.| .
..|.............................................|..............|..
| | +---------+-------------+|
| | | Authorize Request ||
| | | Keep Session Data ||
| | |/Authz-time,Session-Id/||
| | +---------+-------------+|
| | | |
| |<-- - -- - QIR - -- - -- -+ |
| |(Initial Request,Decision | |
| |(QoS-Resources,Authz-time)| |
| +-------+---------+ | |
| |Install QoS State| | |
| | + | | |
| | Authz Session | | |
| | /Authz-time/ | | |
| +-------+---------+ | |
| + - - -- - QIA - - - - - ->| |
| | (Result-Code, | |
| | QoS-Resources) | |
| | +----------+------------+ |
| | | Successful | |
| | | QoS Reservation | |
| | +----------+------------+ |
Sun, et al. Standards Track [Page 43]
RFC 5866 Diameter QoS Application May 2010
..|.............................................|..............|..
. | | | | .
. | | | 200 OK (SDP)| .
. | | <-.-.-.....-.-.+ .
. | | +--------+-----------+ | .
. | | | Activate Session | | .
. | | | Parameters | | .
. | | +--------+-----------+ | .
. | 200 (SDP) | | | .
. <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+ | .
..|.............................................|..............|..
| <- - - - - - RAR - - - - - + |
| +---------+--------+ | |
| |Activate QoS State| | |
| +---------+--------+ | |
| +- - - - - - RAA - - - - - > |
| | |
/------------------+-----Data Flow---------------------------\
\------------------+-----------------------------------------/
| | |
.-.-.-.-. SIP signaling
- - - - - Diameter QoS Application messages
Figure 14: QoS Authorization Example - Push Mode
The communication starts with SIP signaling between the two endpoints
and the SIP proxy for negotiation and authorization of the requested
service and its parameters (see Figure 14). As a part of the
process, the SIP proxy verifies whether the user at Host A is
authorized to use the requested service (and potentially the ability
to be charged for the service usage).
A few implementation choices exist regarding the decision about when
to initiate the QoS reservation. [MMUSIC-MEDIA] discusses this
aspect with a focus on firewalling. In the example above, the DQA
server is triggered to authorize the QoS request based on session
parameters from the Session Description Protocol (SDP) payload. It
will use a QIR message to do so. For this example message flow, we
assume a two-stage commit, i.e., the SIP proxy interacts with the NE
twice. First, it only prepares the QoS reservation, and then, with
the arrival of the 200 OK, the QoS reservation is activated.
This example does not describe how the DQA server learns which DQA
client to contact. We assume pre-configuration in this example. In
any case, the address of the DQA client is put into the Destination-
Host AVP, the description of the QoS resources is included into the
Sun, et al. Standards Track [Page 44]
RFC 5866 Diameter QoS Application May 2010
QoS-Resources AVP, and the duration of the authorization session is
carried in the Authorization-Lifetime AVP.
When the DQA client receives the QIR, it interacts with the Traffic
Control function and reserves the authorized QoS resources
accordingly. At this point in time, the QoS reservation is not yet
activated.
When a 200 OK is returned, the DQA server may verify the accepted QoS
against the pre-authorized QoS resources and send a Diameter RAR
message to the DQA client in the NE for activating the installed
policies and commit the resource allocation.
10. IANA Considerations
This section contains the namespaces that have either been created in
this specification or had their values assigned to existing
namespaces managed by IANA.
10.1. AVP Codes
IANA has allocated two AVP codes to the registry defined in
[RFC3588]:
Registry:
AVP Code AVP Name Reference
-----------------------------------------------------------
579 QoS-Authorization-Data Section 7.2
580 Bound-Auth-Session-Id Section 7.2
10.2. Application IDs
IANA has allocated the following application ID from the registry
defined in [RFC3588] (using the next available value from the
7-16777215 range).
Registry:
ID values Name Reference
-----------------------------------------------------------
9 Diameter QoS application Section 5
Sun, et al. Standards Track [Page 45]
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10.3. Command Codes
IANA has allocated command code values from the registry defined in
[RFC3588].
Registry:
Code Value Name Reference
-----------------------------------------------------------
326 QoS-Authorization-Request (QAR) Section 5.1
326 QoS-Authorization-Answer (QAA) Section 5.2
327 QoS-Install-Request (QIR) Section 5.3
327 QoS-Install-Answer (QIA) Section 5.4
11. Security Considerations
This document describes a mechanism for performing authorization of a
QoS reservation at a third-party entity. The Authorizing Entity
needs sufficient information to make such an authorization decision
and this information may come from various sources, including the
application-layer signaling, the Diameter protocol (with its security
mechanisms), policy information stored available with a AAA server,
and a QoS signaling protocol.
Below there is a discussion about considerations for the Diameter QoS
interaction between an Authorizing Entity and a Network Element.
Security between the Authorizing Entity and the Network Element has a
number of components: authentication, authorization, integrity, and
confidentiality.
Authentication refers to confirming the identity of an originator for
all datagrams received from the originator. Lack of authentication
of Diameter messages between the Authorizing Entity and the Network
Element can seriously jeopardize the fundamental service rendered by
the Network Element. A consequence of not authenticating the message
sender by the Network Element would be that an attacker could spoof
the identity of a "legitimate" Authorizing Entity in order to
allocate resources, change resource assignments, or free resources.
The adversary can also manipulate the state at the Network Element in
such a way that it leads to a denial-of-service attack by, for
example, setting the allowed bandwidth to zero or allocating the
entire bandwidth available to a single flow.
A consequence of not authenticating the Network Element to an
Authorizing Entity is that an attacker could impact the policy-based
admission control procedure operated by the Authorizing Entity that
provides a wrong view of the resources used in the network. Failing
to provide the required credentials should be subject to logging.
Sun, et al. Standards Track [Page 46]
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Authorization refers to whether a particular Authorizing Entity is
authorized to signal a Network Element with requests for one or more
applications, adhering to a certain policy profile. Failing the
authorization process might indicate a resource theft attempt or
failure due to administrative and/or credential deficiencies. In
either case, the Network Element should take the proper measures to
log such attempts.
Integrity is required to ensure that a Diameter message has not been
maliciously altered. The result of a lack of data integrity
enforcement in an untrusted environment could be that an imposter
will alter the messages exchanged between a Network Entity and an
Authorizing Entity potentially causing a denial of service.
Confidentiality protection of Diameter messages ensures that the
signaling data is accessible only to the authorized entities. When
signaling messages from the Application Server (via the Authorizing
Entity towards the Network Element) traverse untrusted networks, lack
of confidentiality will allow eavesdropping and traffic analysis.
Additionally, Diameter QoS messages may carry authorization tokens
that require confidentiality protection.
Diameter offers security mechanisms to deal with the functionality
demanded in the paragraphs above. In particular, Diameter offers
communication security between neighboring Diameter peers using
Transport Layer Security (TLS) or IPsec. Authorization capabilities
are application specific and part of the overall implementation.
12. Acknowledgements
The authors would like to thank John Loughney and Allison Mankin for
their input to this document. In September 2005, Robert Hancock,
Jukka Manner, Cornelia Kappler, Xiaoming Fu, Georgios Karagiannis,
and Elwyn Davies provided a detailed review. Robert also provided us
with good feedback earlier in 2005. Jerry Ash provided us review
comments in late 2005/early 2006. Rajith R provided some inputs to
the document in early 2007.
We would also like to thanks Alexey Melnikov, Adrian Farrel, and
Robert Sparks for their IESG reviews.
13. Contributors
The authors would like to thank Tseno Tsenov and Frank Alfano for
starting the Diameter Quality of Service work within the IETF, for
their significant contributions and for being the driving force for
the first few draft versions.
Sun, et al. Standards Track [Page 47]
RFC 5866 Diameter QoS Application May 2010
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
J. Arkko, "Diameter Base Protocol", RFC 3588,
September 2003.
[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application",
RFC 4005, August 2005.
[RFC5624] Korhonen, J., Tschofenig, H., and E. Davies, "Quality
of Service Parameters for Usage with Diameter",
RFC 5624, August 2009.
[RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M.,
Jones, M., and A. Lior, "Traffic Classification and
Quality of Service (QoS) Attributes for Diameter",
RFC 5777, February 2010.
14.2. Informative References
[MMUSIC-MEDIA] Stucker, B. and H. Tschofenig, "Analysis of Middlebox
Interactions for Signaling Protocol Communication
along the Media Path", Work in Progress, March 2009.
[NSIS-NTLP] Schulzrinne, H. and M. Stiemerling, "GIST: General
Internet Signalling Transport", Work in Progress,
June 2009.
[NSIS-QOS] Manner, J., Karagiannis, G., and A. McDonald, "NSLP
for Quality-of-Service Signaling", Work in Progress,
January 2010.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC2211] Wroclawski, J., "Specification of the Controlled-Load
Network Element Service", RFC 2211, September 1997.
Sun, et al. Standards Track [Page 48]
RFC 5866 Diameter QoS Application May 2010
[RFC2212] Shenker, S., Partridge, C., and R. Guerin,
"Specification of Guaranteed Quality of Service",
RFC 2212, September 1997.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
December 1998.
[RFC2753] Yavatkar, R., Pendarakis, D., and R. Guerin, "A
Framework for Policy-based Admission Control",
RFC 2753, January 2000.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service
(RADIUS)", RFC 2865, June 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G.,
Johnston, A., Peterson, J., Sparks, R., Handley, M.,
and E. Schooler, "SIP: Session Initiation Protocol",
RFC 3261, June 2002.
[RFC3313] Marshall, W., "Private Session Initiation Protocol
(SIP) Extensions for Media Authorization", RFC 3313,
January 2003.
[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.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen,
"The Network Access Identifier", RFC 4282,
December 2005.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP:
Session Description Protocol", RFC 4566, July 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
Sun, et al. Standards Track [Page 49]
RFC 5866 Diameter QoS Application May 2010
Authors' Addresses
Dong Sun (editor)
Alcatel-Lucent
600 Mountain Ave
Murray Hill, NJ 07974
USA
Phone: +1 908 582 2617
EMail: d.sun@alcatel-lucent.com
Peter J. McCann
Motorola Labs
1301 E. Algonquin Rd
Schaumburg, IL 60196
USA
Phone: +1 847 576 3440
EMail: pete.mccann@motorola.com
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
EMail: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Tina Tsou
Huawei
Shenzhen,
P.R.C
EMail: tena@huawei.com
Avri Doria
Lulea University of Technology
Arbetsvetenskap
Lulea, SE-97187
Sweden
EMail: avri@ltu.se
Sun, et al. Standards Track [Page 50]
RFC 5866 Diameter QoS Application May 2010
Glen Zorn (editor)
Network Zen
1310 East Thomas Street
#306
Seattle, Washington 98102
USA
Phone: +1 (206) 377-9035
EMail: gwz@net-zen.net
Sun, et al. Standards Track [Page 51]