💾 Archived View for gmi.noulin.net › rfc › rfc7551.gmi captured on 2022-04-29 at 02:43:20. Gemini links have been rewritten to link to archived content
⬅️ Previous capture (2022-01-08)
-=-=-=-=-=-=-
Updated by:
Internet Engineering Task Force (IETF) F. Zhang, Ed.
Request for Comments: 7551 Huawei
Category: Standards Track R. Jing
ISSN: 2070-1721 China Telecom
R. Gandhi, Ed.
Cisco Systems
May 2015
RSVP-TE Extensions
for Associated Bidirectional Label Switched Paths (LSPs)
Abstract
This document describes Resource Reservation Protocol (RSVP)
extensions to bind two point-to-point unidirectional Label Switched
Paths (LSPs) into an associated bidirectional LSP. The association
is achieved by defining new Association Types for use in ASSOCIATION
and in Extended ASSOCIATION Objects. One of these types enables
independent provisioning of the associated bidirectional LSPs on both
sides, while the other enables single-sided provisioning. The
REVERSE_LSP Object is also defined to enable a single endpoint to
trigger creation of the reverse LSP and to specify parameters of the
reverse LSP in the single-sided provisioning case.
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/rfc7551.
Zhang, et al. Standards Track [Page 1]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
Copyright Notice
Copyright (c) 2015 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
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.
Zhang, et al. Standards Track [Page 2]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
Table of Contents
1. Introduction ....................................................4
2. Conventions Used in This Document ...............................5
2.1. Key Word Definitions .......................................5
2.2. Reverse Unidirectional LSPs ................................5
2.3. Message Formats ............................................5
3. Overview ........................................................6
3.1. Provisioning Model Overview ................................6
3.1.1. Single-Sided Provisioning ...........................6
3.1.2. Double-Sided Provisioning ...........................6
3.2. Association Signaling Overview .............................6
3.2.1. Single-Sided Provisioning ...........................7
3.2.2. Double-Sided Provisioning ...........................7
3.3. Asymmetric Bandwidth Signaling Overview ....................8
3.3.1. Single-Sided Provisioning ...........................8
3.3.2. Double-Sided Provisioning ...........................8
3.4. Recovery LSP Overview ......................................8
4. Message and Object Definitions ..................................9
4.1. RSVP Message Formats .......................................9
4.2. ASSOCIATION Object .........................................9
4.3. Extended ASSOCIATION Object ...............................10
4.4. REVERSE_LSP Object Definition .............................11
4.4.1. REVERSE_LSP Object Format ..........................11
4.4.2. REVERSE_LSP Subobjects .............................11
5. Processing Rules ...............................................12
5.1. Rules for ASSOCIATION Object ..............................12
5.1.1. Compatibility for ASSOCIATION Object ...............14
5.2. Rules for REVERSE_LSP Object ..............................14
5.2.1. Compatibility for REVERSE_LSP Object ...............16
6. IANA Considerations ............................................16
6.1. Association Types .........................................16
6.2. REVERSE_LSP Object ........................................16
6.3. Reverse LSP Failure PathErr Sub-code ......................17
7. Security Considerations ........................................17
8. References .....................................................18
8.1. Normative References ......................................18
8.2. Informative References ....................................19
Acknowledgements ..................................................20
Contributors ......................................................20
Authors' Addresses ................................................20
Zhang, et al. Standards Track [Page 3]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
1. Introduction
The MPLS Transport Profile (MPLS-TP) requirements document [RFC5654]
specifies that MPLS-TP MUST support associated bidirectional point-
to-point Label Switched Paths (LSPs). These requirements are given
in Section 2.1 ("General Requirements") of that document and are
partially rephrased below:
7. MPLS-TP MUST support associated bidirectional point-to-point
LSPs.
11. The end points of an associated bidirectional LSP MUST be aware
of the pairing relationship of the forward and reverse LSPs used
to support the bidirectional service.
12. Nodes on the LSP of an associated bidirectional LSP where both
the forward and backward directions transit the same node in the
same (sub)layer as the LSP SHOULD be aware of the pairing
relationship of the forward and the backward directions of the
LSP.
50. The MPLS-TP control plane MUST support establishing associated
bidirectional P2P LSP including configuration of protection
functions and any associated maintenance functions.
The above requirements are also repeated in [RFC6373].
Furthermore, an associated bidirectional LSP is also useful for
protection-switching for Operations, Administration, and Maintenance
(OAM) messages that require a return path.
A variety of applications, such as Internet services and the return
paths of OAM messages, exist and may have different upstream and
downstream bandwidth requirements. [RFC5654] specifies an asymmetric
bandwidth requirement in Section 2.1 ("General Requirements"), and it
is repeated below:
14. MPLS-TP MUST support bidirectional LSPs with asymmetric
bandwidth requirements, i.e., the amount of reserved bandwidth
differs between the forward and backward directions.
The approach for supporting asymmetric bandwidth co-routed
bidirectional LSPs is defined in [RFC6387].
The method of association and the corresponding Resource Reservation
Protocol (RSVP) ASSOCIATION Object are defined in [RFC4872],
[RFC4873], and [RFC6689]. In that context, the ASSOCIATION Object is
used to associate a recovery LSP with the LSP it is protecting. This
Zhang, et al. Standards Track [Page 4]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
object also has broader applicability as a mechanism to associate
RSVP states. [RFC6780] defines the Extended ASSOCIATION Objects that
can be more generally applied for this purpose. This document uses
the term "(Extended) ASSOCIATION Objects" to refer collectively to
the ASSOCIATION Objects defined in [RFC4872] and the Extended
ASSOCIATION Objects defined in [RFC6780].
This document specifies mechanisms for binding two reverse
unidirectional LSPs into an associated bidirectional LSP. The
association is achieved by defining new Association Types for use in
(Extended) ASSOCIATION Objects. One of these types enables
independent provisioning of the associated bidirectional LSPs, while
the other enables single-sided provisioning. The REVERSE_LSP Object
is also defined to enable a single endpoint to trigger creation of
the reverse LSP and to specify parameters of the reverse LSP in the
single-sided provisioning case. For example, the REVERSE_LSP Object
allow asymmetric upstream and downstream bandwidths for the
associated bidirectional LSP.
2. Conventions Used in This Document
2.1. Key Word Definitions
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 [RFC2119].
2.2. Reverse Unidirectional LSPs
Two reverse unidirectional LSPs are setup in the opposite directions
between a pair of source and destination nodes to form an associated
bidirectional LSP. A reverse unidirectional LSP originates on the
same node where the forward unidirectional LSP terminates, and it
terminates on the same node where the forward unidirectional LSP
originates.
2.3. Message Formats
This document uses the Routing Backus-Naur Form (RBNF) to define
message formats as defined in [RFC5511].
Zhang, et al. Standards Track [Page 5]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
3. Overview
3.1. Provisioning Model Overview
This section provides an overview and definition of the models for
provisioning associated bidirectional LSPs.
The associated bidirectional LSP's forward and reverse unidirectional
LSPs are established, monitored, and protected independently as
specified by [RFC5654]. Configuration information regarding the LSPs
can be provided at one or both endpoints of the associated
bidirectional LSP. Depending on the method chosen, there are two
models of creating an associated bidirectional LSP -- single-sided
provisioning and double-sided provisioning.
3.1.1. Single-Sided Provisioning
For the single-sided provisioning, the Traffic Engineering (TE)
tunnel is configured only on one endpoint. An LSP for this tunnel is
initiated by the initiating endpoint with the (Extended) ASSOCIATION
and REVERSE_LSP Objects inserted in the Path message. The other
endpoint then creates the corresponding reverse TE tunnel and signals
the reverse LSP in response using information from the REVERSE_LSP
Object and other objects present in the received Path message.
3.1.2. Double-Sided Provisioning
For the double-sided provisioning, two unidirectional TE tunnels are
configured independently, one on each endpoint. The LSPs for the
tunnels are signaled with (Extended) ASSOCIATION Objects inserted in
the Path message by both endpoints to indicate that the two LSPs are
to be associated to form a bidirectional LSP.
3.2. Association Signaling Overview
This section provides an overview of the association signaling
methods for the associated bidirectional LSPs.
Three scenarios exist for binding two unidirectional LSPs together to
form an associated bidirectional LSP. These are:
1) Neither unidirectional LSP exists, and both must be established.
2) Both unidirectional LSPs exist, but the association must be
established.
3) One LSP exists, but the reverse associated LSP must be
established.
Zhang, et al. Standards Track [Page 6]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
The following sections describe the applicable provisioning models
for each of these scenarios.
Path Computation Element (PCE)-based approaches [RFC4655] may be used
for path computation of an associated bidirectional LSP. However,
these approaches are outside the scope of this document.
Consider the topology described in Figure 1. LSP1 from node A to B,
takes the path A,D,B, and LSP2 from node B to A takes the path
B,D,C,A. These two LSPs, once established and associated, form an
associated bidirectional LSP between nodes A and B.
LSP1 -->
A-------D-------B
\ / <-- LSP2
\ /
\ /
C
Figure 1: An Example of Associated Bidirectional LSP
3.2.1. Single-Sided Provisioning
For the single-sided provisioning model, creation of reverse LSP1
shown in Figure 1 is triggered by LSP2, or creation of reverse LSP2
is triggered by LSP1. When creation of reverse LSP2 is triggered by
LSP1, LSP1 is provisioned first (or refreshed, if LSP1 already
exists) at node A. LSP1 is then signaled with an (Extended)
ASSOCIATION, and REVERSE_LSP Objects are inserted in the Path
message. The Association Type indicates single-sided provisioning.
Upon receiving this Path message for LSP1, node B establishes reverse
LSP2. The (Extended) ASSOCIATION Object inserted in LSP2's Path
message is the same as that received in LSP1's Path message.
A similar procedure is used if LSP2 is provisioned first at node B,
and the creation of reverse LSP1 at node A is triggered by LSP2. In
both scenarios, the two unidirectional LSPs are bound together to
form an associated bidirectional LSP based on identical (Extended)
ASSOCIATION Objects in the two LSPs' Path messages.
3.2.2. Double-Sided Provisioning
For the double-sided provisioning model, both LSP1 and LSP2 shown in
Figure 1 are signaled independently with (Extended) ASSOCIATION
Objects inserted in the Path messages, in which the Association Type
indicating double-sided provisioning is included. In this case, the
two unidirectional LSPs are bound together to form an associated
bidirectional LSP based on identical (Extended) ASSOCIATION Objects
Zhang, et al. Standards Track [Page 7]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
in the two LSPs' Path messages. In all three scenarios described in
Section 3.2, the LSPs to be selected for the association are
provisioned by the management action applied at both endpoints.
3.3. Asymmetric Bandwidth Signaling Overview
This section provides an overview of the methods for signaling
asymmetric upstream and downstream bandwidths for the associated
bidirectional LSPs.
3.3.1. Single-Sided Provisioning
A new REVERSE_LSP Object for use in the single-sided provisioning
model is defined in this document, in Section 4.4. The REVERSE_LSP
Object allows the initiating node of the single-sided provisioned LSP
to trigger creation of the reverse LSP on the remote node. When the
single-sided provisioning model is used, a SENDER_TSPEC Object can be
added in the REVERSE_LSP Object as a subobject in the initiating
LSP's Path message to specify a different bandwidth for the reverse
LSP. As described in Section 4.4, addition of the REVERSE_LSP Object
also allows the initiating node to control other aspects of the
reverse LSP (such as its path) by including other objects in a
REVERSE_LSP Object.
Consider again the topology described in Figure 1, where the creation
of reverse LSP2 is triggered by LSP1. Node A signals LSP1 with the
(Extended) ASSOCIATION Object with Association Type indicating
single-sided provisioning and inserts a SENDER_TSPEC subobject for
use by LSP2 in the REVERSE_LSP Object in the Path message. Node B
then establishes the LSP2 in the reverse direction using the
asymmetric bandwidth thus specified by LSP1 and allows node A to
control the reverse LSP2.
3.3.2. Double-Sided Provisioning
When the double-sided provisioning model is used, the two
unidirectional LSPs are established with separate bandwidths, which
may or may not be identical. However, these LSPs are associated
purely based on the identical contents of their (Extended)
ASSOCIATION Objects.
3.4. Recovery LSP Overview
Recovery of each unidirectional LSP forming the bidirectional LSP is
independent [RFC5654] and is based on the parameters signaled in
their respective RSVP Path messages.
Zhang, et al. Standards Track [Page 8]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
Recovery LSP association is based on the identical content of the
(Extended) ASSOCIATION Objects signaled in their Path messages during
the initial LSP setup for both single-sided and double-sided
provisioning. As defined in [RFC6780], multiple ASSOCIATION Objects
may be present in the signaling of a single LSP.
4. Message and Object Definitions
4.1. RSVP Message Formats
This section presents the RSVP message-related formats as modified by
this document. Unmodified RSVP message formats are not listed.
The format of a Path message is as follows:
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <PROTECTION> ]
[ <LABEL_SET> ... ]
[ <SESSION_ATTRIBUTE> ]
[ <NOTIFY_REQUEST> ... ]
[ <ADMIN_STATUS> ]
[ <ASSOCIATION> ... ]
[ <REVERSE_LSP> ... ]
[ <POLICY_DATA> ... ]
<sender descriptor>
The format of the <sender descriptor> is not modified by this
document.
4.2. ASSOCIATION Object
The ASSOCIATION Object is populated using the rules defined below for
associating two reverse unidirectional LSPs to form an associated
bidirectional LSP.
Association Types:
In order to bind two reverse unidirectional LSPs to be an
associated bidirectional LSP, the Association Type MUST be set to
indicate either single-sided or double-sided LSPs.
Zhang, et al. Standards Track [Page 9]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
The new Association Types are defined as follows:
Value Type
----- -----
3 Double-Sided Associated Bidirectional LSP (D)
4 Single-Sided Associated Bidirectional LSP (A)
Association ID:
For both single-sided and double-sided provisioning, Association
ID MUST be set to a value assigned by the node that originates the
association for the bidirectional LSP.
Association Source:
Association Source MUST be set to an address selected by the node
that originates the association for the bidirectional LSP. For
example, this may be a management entity or, in the case of
single-sided provisioning, an address assigned to the node that
originates the LSP.
4.3. Extended ASSOCIATION Object
The Extended ASSOCIATION Object is populated using the rules defined
below for associating two reverse unidirectional LSPs to form a
bidirectional LSP.
The Association Type, Association ID, and Association Source MUST be
set as defined for the ASSOCIATION Object in Section 4.1.
Global Association Source:
For both single-sided and double-sided provisioning, Global
Association Source, when used, MUST be set to the Global_ID
[RFC6370] of the node that originates the association for the
bidirectional LSP.
Extended Association ID:
For both single-sided and double-sided provisioning, Extended
Association ID, when used, MUST be set to a value selected by the
node that originates the association for the bidirectional LSP.
Zhang, et al. Standards Track [Page 10]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
4.4. REVERSE_LSP Object Definition
4.4.1. REVERSE_LSP Object Format
The REVERSE_LSP Object is carried in the Path message of a forward
LSP to provide information to be used by the reverse LSP. The object
also indicates that the LSP is the forward LSP of a single-sided
associated bidirectional LSP.
The Object has the following format:
Class_Num = 203, C_Type = 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.4.2. REVERSE_LSP Subobjects
Subobjects are used to override the default contents of a Path
message of a reverse LSP; see Section 5.2. The contents of a
REVERSE_LSP Object is zero or more variable-length subobjects that
have the same format as RSVP Objects; see Section 3.1.2 of [RFC2205].
Any object that may be carried in a Path message MAY be carried in
the REVERSE_LSP Object. Subobject ordering MUST follow any Path
message Object ordering requirements.
Examples of the Path message Objects that can be carried in the
REVERSE_LSP Object are (but not limited to):
- SENDER_TSPEC [RFC2205]
- EXPLICIT_ROUTE Object (ERO) [RFC3209]
- SESSION_ATTRIBUTE Object [RFC3209]
- ADMIN_STATUS Object [RFC3473]
- LSP_REQUIRED_ATTRIBUTES Object [RFC5420]
- PROTECTION Object [RFC3473] [RFC4872]
Zhang, et al. Standards Track [Page 11]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
5. Processing Rules
In general, the processing rules for the ASSOCIATION Object are as
specified in [RFC4872], and those for the Extended ASSOCIATION Object
are as specified in [RFC6780]. The following sections describe the
rules for processing (Extended) ASSOCIATION Objects for both double-
sided and single-sided associated bidirectional LSPs and REVERSE_LSP
Objects for single-sided associated bidirectional LSPs.
5.1. Rules for ASSOCIATION Object
This section defines the processing for the association of two
unidirectional LSPs to form an associated bidirectional LSP. Such
association is based on the use of an (Extended) ASSOCIATION Object.
The procedures related to the actual identification of associations
between LSPs based on (Extended) ASSOCIATION Objects are defined in
[RFC6780]. [RFC6780] specifies that in the absence of rules for
identifying the association that are specific to the Association
Type, the included (Extended) ASSOCIATION Objects in the LSPs MUST be
identical in order for an association to exist. This document adds
no specific rules for the new Association Types defined, and the
identification of an LSP association therefore proceeds as specified
in [RFC6780].
As described in [RFC6780], association of LSPs can be upstream or
downstream initiated, as indicated by (Extended) ASSOCIATION Objects
in Path or Resv Messages. The association of bidirectional LSPs is
always upstream initiated; therefore, the Association Types defined
in this document are only to be interpreted in Path Messages. These
types SHOULD NOT be used in ASSOCIATION Objects carried in Resv
messages and SHOULD be ignored if present.
To indicate an associated bidirectional LSP, an ingress node MUST
insert an (Extended) ASSOCIATION Object into the Path message of the
unidirectional LSP that is part of the associated bidirectional LSP
it initiates. If either Global Association Source or Extended
Association Address is required, then an Extended ASSOCIATION Object
[RFC6780] MUST be inserted in the Path message. Otherwise, an
ASSOCIATION Object MAY be used. (Extended) ASSOCIATION Objects with
both single-sided and double-sided Association Types MUST NOT be
added or sent in the same Path message.
The ingress node MUST set the Association Type field in the
(Extended) ASSOCIATION Object to "Single-Sided Associated
Bidirectional LSP" when single-sided provisioning is used, and to
"Double-Sided Associated Bidirectional LSP" when double-sided
provisioning is used.
Zhang, et al. Standards Track [Page 12]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
A transit node MAY identify the unidirectional LSPs of an associated
bidirectional LSP based on (Extended) ASSOCIATION Objects, with the
Association Type values defined in this document, carried in Path
messages. Clearly, such associations are only possible when the LSPs
transit the node. As mentioned above, such associations are made per
the rules defined in [RFC6780].
Egress nodes that support the Association Types defined in this
document identify the unidirectional LSPs of an associated
bidirectional LSP based on (Extended) ASSOCIATION Objects carried in
Path messages. Note that an ingress node will normally be the
ingress for one of the unidirectional LSPs that make up an associated
bidirectional LSP. When an egress node receives a Path message
containing an (Extended) ASSOCIATION Object with one of the
Association Types defined in this document, it MUST attempt to
identify other LSPs (including ones for which it is an ingress node)
with which the LSP being processed is associated. As defined above,
such associations are made per the rules defined in [RFC6780]. An
LSP not being associated at the time of signaling (for example,
during rerouting or re-optimization) on an egress node is not
necessarily considered an error condition.
Associated bidirectional LSP teardown follows the standard procedures
defined in [RFC3209] and [RFC3473] either without or with the
administrative status. Generally, the teardown procedures of the
unidirectional LSPs forming an associated bidirectional LSP are
independent of each other, so it is possible that while one LSP
follows graceful teardown with administrative status, the reverse LSP
is torn down without administrative status (using
PathTear/ResvTear/PathErr with state removal). See Section 5.2 for
additional rules related to LSPs established using single-sided
provisioning.
When an LSP signaled with a Path message containing an (Extended)
ASSOCIATION Object with an Association Type defined in this document
is torn down, the processing node SHALL remove the binding of the LSP
to any previously identified associated bidirectional LSP.
No additional processing is needed for Path messages with an
(Extended) ASSOCIATION Object containing an Association Type field
set to "Double-Sided Associated Bidirectional LSP".
Zhang, et al. Standards Track [Page 13]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
5.1.1. Compatibility for ASSOCIATION Object
The ASSOCIATION Object has been defined in [RFC4872] and the Extended
ASSOCIATION Object has been defined in [RFC6780], both with class
numbers in the form 11bbbbbb, which ensures compatibility with non-
supporting nodes. Per [RFC2205], such nodes will ignore the object
but forward it without modification.
Operators wishing to use a function supported by a particular
Association Type SHOULD ensure that the type is supported on any node
that is expected to act on the association [RFC6780].
An egress node that does not support the Association Types defined in
this document is expected to return a PathErr with Error Code
"Admission Control Failure" (1) [RFC2205] and Sub-code "Bad
Association Type" (5) [RFC4872].
LSP recovery as defined in [RFC4872] and [RFC4873] is not impacted by
this document. The recovery mechanisms defined in [RFC4872] and
[RFC4873] rely on the use of the (Extended) ASSOCIATION Objects, but
they use a different value for Association Type; multiple ASSOCIATION
Objects can be present in the LSP Path message and can coexist with
the procedures defined in this document.
5.2. Rules for REVERSE_LSP Object
When a node initiates setup of an LSP using a Path message containing
an ASSOCIATION or Extended ASSOCIATION Object, and the Association
Type set to "Single-Sided Associated Bidirectional LSP", the Path
message MUST carry the REVERSE_LSP Object to trigger creation of a
reverse LSP on the egress node.
The REVERSE_LSP subobject MAY contain any of the objects that the
initiating node desires to have included in the Path message for the
associated reverse LSP. The REVERSE_LSP Object SHOULD NOT be
included in a REVERSE_LSP Object.
A transit node receiving a valid Path message containing a
REVERSE_LSP Object MUST forward the REVERSE_LSP Object unchanged in
the outgoing Path message.
An egress node, upon receiving a Path message containing an
REVERSE_LSP Object MUST verify that the Path message contains an
ASSOCIATION or Extended ASSOCIATION Object with the Association Type
set to "Single-Sided Associated Bidirectional LSP". If it does not,
the Path message MUST NOT trigger a reverse LSP. This verification
failure SHOULD NOT trigger any RSVP message but can be logged
locally, and perhaps reported through network management mechanisms.
Zhang, et al. Standards Track [Page 14]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
Once validated, the egress node MUST create an LSP in the reverse
direction or reject the Path message. If the creation of a reverse
LSP fails, the egress node MUST return a PathErr with Error Code
"Admission Control Failure" (1) [RFC2205] and Sub-code "Reverse LSP
Failure" (6) defined in this document. Note that normal Resv
processing SHOULD NOT be impacted by the presence of an ASSOCIATION
Object with an Association Type set to "Single-Sided Associated
Bidirectional LSP".
The egress node MUST use the subobjects contained in the REVERSE_LSP
Object for initiating the reverse LSP. When a subobject is not
present in the received REVERSE_LSP Object, the egress node SHOULD
initiate the reverse LSP based on the information contained in the
received Path message of the forward LSP as follows:
o The egress node SHOULD copy the information from the received
SESSION_ATTRIBUTE, CLASS_TYPE, LABEL_REQUEST, ASSOCIATION,
ADMIN_STATUS, and PROTECTION Objects in the forward LSP Path
message to form the Path message of the reverse LSP when the
object is not present in the received REVERSE_LSP Object.
o The IP address in the reverse LSP's SESSION Object SHOULD be set
to the IP address carried in the received SENDER_TEMPLATE Object;
and conversely, the IP address in the SENDER_TEMPLATE Object
SHOULD be set to the IP address carried in the received SESSION
Object. There are no additional requirements related to the IDs
carried in the SESSION and SENDER_TEMPLATE Objects.
o When the forward LSP Path message contains a RECORD_ROUTE Object,
the egress node SHOULD include the received RECORD_ROUTE Object in
the reverse LSP Path message. Local node information SHOULD also
be recorded per standard Path message processing.
o There are no specific requirements related to other objects.
The resulting Path message is used to create the reverse LSP. From
this point on, standard Path message processing is used in processing
the resulting Path message.
Note that the contents of a forward LSP, including a carried
REVERSE_LSP Object, may change over the life of an LSP, and such
changes MUST result in corresponding changes in the reverse LSP. In
particular, any object or subobject that was copied during the
creation of the initial reverse LSP's Path message MUST be copied
when modified in the forward LSP, and a trigger Path message MUST be
processed.
Zhang, et al. Standards Track [Page 15]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
The removal of the REVERSE_LSP Object in the received Path message
SHOULD cause the egress node to tear down any previously established
reverse LSP.
When the egress node receives a PathTear message for the forward LSP
or whenever the forward LSP is torn down, the node MUST remove the
associated reverse LSP using standard PathTear message processing.
Teardown of the reverse LSP for other reasons SHOULD NOT trigger
removal of the initiating LSP, but it SHOULD result in the egress
node sending a PathErr with Error Code "Admission Control Failure"
(1) [RFC2205] and Sub-code "Reverse LSP Failure" (6) defined in this
document.
5.2.1. Compatibility for REVERSE_LSP Object
The REVERSE_LSP Object is defined with class numbers in the form
11bbbbbb, which ensures compatibility with non-supporting nodes. Per
[RFC2205], such nodes will ignore the object but forward it without
modification.
6. IANA Considerations
IANA has registered values for the namespace defined in this document
and summarized in this section.
6.1. Association Types
IANA maintains the "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Parameters" registry (see
<http://www.iana.org/assignments/gmpls-sig-parameters>). The
"Association Type" subregistry is included in this registry.
This registry has been updated by new Association Types for
ASSOCIATION and Extended ASSOCIATION Objects defined in this document
as follows:
Value Name Reference
3 Double-Sided Associated Bidirectional LSP (D) Section 4.2
4 Single-Sided Associated Bidirectional LSP (A) Section 4.2
6.2. REVERSE_LSP Object
IANA maintains the "Resource Reservation Protocol (RSVP) Parameters"
registry (see <http://www.iana.org/assignments/rsvp-parameters>).
The "Class Names, Class Numbers, and Class Types" subregistry is
included in this registry.
Zhang, et al. Standards Track [Page 16]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
This registry has been extended for new Class Number (Class-Num) and
Class Type (C-type) for RSVP REVERSE_LSP Object requested in the
11bbbbbb range defined in this document as follows:
Class Number Class Name Reference
203 REVERSE_LSP Section 4.4
o REVERSE_LSP : Class Type or C-type = 1
6.3. Reverse LSP Failure PathErr Sub-code
IANA maintains the "Resource Reservation Protocol (RSVP) Parameters"
registry (see <http://www.iana.org/assignments/rsvp-parameters>).
The "Error Codes and Globally-Defined Error Value Sub-Codes"
subregistry is included in this registry.
This registry has been extended for the new PathErr Sub-code defined
in this document as follows:
Error Code = 01: "Admission Control Failure" (see [RFC2205])
o "Reverse LSP Failure" (6)
7. Security Considerations
This document introduces two new Association Types for the (Extended)
ASSOCIATION Object, Double-Sided Associated Bidirectional LSP and
Single-Sided Associated Bidirectional LSP. These types, by
themselves, introduce no additional information to signaling.
Related security considerations are already covered for this in RFC
6780.
The REVERSE_LSP Object is carried in the Path message of a forward
LSP of the single-sided associated bidirectional LSP. It can carry
parameters for the reverse LSP. This does allow for additional
information to be conveyed, but this information is not fundamentally
different from the information that is already carried in a
bidirectional LSP message. The processing of such messages is
already subject to local policy as well as security considerations
discussions. For a general discussion on MPLS- and GMPLS-related
security issues, see the MPLS/GMPLS security framework [RFC5920].
Zhang, et al. Standards Track [Page 17]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
[RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
<http://www.rfc-editor.org/info/rfc4872>.
[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
May 2007, <http://www.rfc-editor.org/info/rfc4873>.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511, April
2009, <http://www.rfc-editor.org/info/rfc5511>.
[RFC6780] Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
ASSOCIATION Object Extensions", RFC 6780,
DOI 10.17487/RFC6780, October 2012,
<http://www.rfc-editor.org/info/rfc6780>.
Zhang, et al. Standards Track [Page 18]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
8.2. Informative References
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>.
[RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
Ayyangarps, "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420,
February 2009, <http://www.rfc-editor.org/info/rfc5420>.
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC5654,
September 2009, <http://www.rfc-editor.org/info/rfc5654>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370,
DOI 10.17487/RFC6370, September 2011,
<http://www.rfc-editor.org/info/rfc6370>.
[RFC6373] Andersson, L., Ed., Berger, L., Ed., Fang, L., Ed., Bitar,
N., Ed., and E. Gray, Ed., "MPLS Transport Profile
(MPLS-TP) Control Plane Framework", RFC 6373,
DOI 10.17487/RFC6373, September 2011,
<http://www.rfc-editor.org/info/rfc6373>.
[RFC6387] Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 6387, DOI 10.17487/RFC6387,
September 2011, <http://www.rfc-editor.org/info/rfc6387>.
[RFC6689] Berger, L., "Usage of the RSVP ASSOCIATION Object",
RFC 6689, DOI 10.17487/RFC6689, July 2012,
<http://www.rfc-editor.org/info/rfc6689>.
Zhang, et al. Standards Track [Page 19]
RFC 7551 RSVP-TE Extensions for Associated LSP May 2015
Acknowledgements
The authors would like to thank Lou Berger and George Swallow for
their great guidance in this work; Jie Dong for the discussion of the
recovery LSP; Lamberto Sterling for his valuable comments about
asymmetric bandwidth signaling; Attila Takacs for the discussion of
the provisioning model; Siva Sivabalan, Eric Osborne, and Robert
Sawaya for the discussions on the ASSOCIATION Object; and Matt
Hartley for providing useful suggestions on the document. At the
same time, the authors would like to acknowledge the contributions of
Bo Wu, Xihua Fu, and Lizhong Jin for the initial discussions; Wenjuan
He for the prototype implementation; and Lou Berger, Daniel King, and
Deborah Brungard for the review of the document.
Contributors
Fan Yang
ZTE
EMail: yang.fan240347@gmail.com
Weilian Jiang
ZTE
EMail: jiang.weilian@gmail.com
Authors' Addresses
Fei Zhang (editor)
Huawei
EMail: zhangfei7@huawei.com
Ruiquan Jing
China Telecom
EMail: jingrq@ctbri.com.cn
Rakesh Gandhi (editor)
Cisco Systems
EMail: rgandhi@cisco.com
Zhang, et al. Standards Track [Page 20]