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Versions: (draft-ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp) 00 01 02 03 04 05 06 07 RFC 7551

TEAS Working Group                                        Fei Zhang, Ed.
Internet-Draft                                                    Huawei
Intended status: Standards Track                            Ruiquan Jing
Expires: September 4, 2015                                 China Telecom
                                                      Rakesh Gandhi, Ed.
                                                           Cisco Systems
                                                           March 3, 2015


          RSVP-TE Extensions for Associated Bidirectional LSPs
          draft-ietf-teas-mpls-tp-rsvpte-ext-associated-lsp-07

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 Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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



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   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.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  4
     2.2.  Reverse Unidirectional LSPs  . . . . . . . . . . . . . . .  4
     2.3.  Message Formats  . . . . . . . . . . . . . . . . . . . . .  4
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Provisioning Model Overview  . . . . . . . . . . . . . . .  4
       3.1.1.  Single Sided Provisioning  . . . . . . . . . . . . . .  5
       3.1.2.  Double Sided Provisioning  . . . . . . . . . . . . . .  5
     3.2.  Association Signaling Overview . . . . . . . . . . . . . .  5
       3.2.1.  Single Sided Provisioning  . . . . . . . . . . . . . .  6
       3.2.2.  Double Sided Provisioning  . . . . . . . . . . . . . .  6
     3.3.  Asymmetric Bandwidth Signaling Overview  . . . . . . . . .  6
       3.3.1.  Single Sided Provisioning  . . . . . . . . . . . . . .  7
       3.3.2.  Double Sided Provisioning  . . . . . . . . . . . . . .  7
     3.4.  Recovery LSP Overview  . . . . . . . . . . . . . . . . . .  7
   4.  Message and Object Definitions . . . . . . . . . . . . . . . .  7
     4.1.  RSVP Message Formats . . . . . . . . . . . . . . . . . . .  7
     4.2.  ASSOCIATION Object . . . . . . . . . . . . . . . . . . . .  8
     4.3.  Extended ASSOCIATION Object  . . . . . . . . . . . . . . .  9
     4.4.  REVERSE_LSP Object Definition  . . . . . . . . . . . . . .  9
       4.4.1.  REVERSE_LSP Object Format  . . . . . . . . . . . . . .  9
       4.4.2.  REVERSE_LSP Subobjects . . . . . . . . . . . . . . . . 10
   5.  Processing Rules . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Rules For ASSOCIATION Object . . . . . . . . . . . . . . . 10
       5.1.1.  Compatibility For ASSOCIATION Object . . . . . . . . . 12
     5.2.  Rules For REVERSE_LSP Object . . . . . . . . . . . . . . . 13
       5.2.1.  Compatibility For REVERSE_LSP Object . . . . . . . . . 14
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
     6.1.  Association Types  . . . . . . . . . . . . . . . . . . . . 15
     6.2.  REVERSE_LSP Object . . . . . . . . . . . . . . . . . . . . 15
     6.3.  Reverse LSP Failure PathErr Sub-code . . . . . . . . . . . 16
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  Contributing Authors . . . . . . . . . . . . . . . . . . . . . 17
   10.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 18
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . 18
     10.2.  Informative References  . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20



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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), and are repeated 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, Administrations 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 which may have different upstream
   and downstream bandwidth requirements.  [RFC5654] specifies an
   asymmetric bandwidth requirement in Section 2.1 (General
   Requirements), and 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
   object also has broader applicability as a mechanism to associate



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   RSVP states.  [RFC6780] defines the Extended ASSOCIATION Objects that
   can be more generally applied for this purpose.  This document refers
   to the [RFC4872] defined ASSOCIATION Objects and the [RFC6780]
   defined the Extended ASSOCIATION Objects collectively as the
   (Extended) ASSOCIATION Objects.


   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].


3.  Overview

3.1.  Provisioning Model Overview

   This section provides an overview and definition of the models for
   provisioning associated bidirectional LSPs.



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   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.  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 (an example of associated
   bidirectional LSP).  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 node A and node B.



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                           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 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
   in the two LSPs' Path messages.  The LSPs to be selected for the
   association are provisioned by the management action applied at both
   endpoints in all three scenarios described above.

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.




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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.

   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, see [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



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   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.

      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:




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      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.



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
   provisioned associated bidirectional LSP.

   The Object has the following format:




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   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 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]


5.  Processing Rules

   In general, the processing rules for the ASSOCIATION Object are as
   specified in [RFC4872] and Extended ASSOCIATION Object are specified
   in [RFC6780].  Following sections describe the rules for processing
   (Extended) ASSOCIATION Object for both double sided and single sided
   associated bidirectional LSPs and REVERSE_LSP Object 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.




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   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 Association
   Type-specific rule for identifying association, 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 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 initialized, 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.

   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 which 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



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   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 below
   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 of
   Double Sided Associated Bidirectional LSP.

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 (01) [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
   use a different value for Association Type; multiple ASSOCIATION



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   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 object 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.

   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 (01) [RFC2205]" and Sub-code "Reverse LSP
   Failure" 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.



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   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.

   The removal of the REVERSE_LSP Object in the received Path message
   SHOULD cause the egress node to teardown 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.
   Tear down of the reverse LSP for other reasons SHOULD NOT trigger
   removal of the initiating LSP, but SHOULD result in the egress node
   sending a PathErr with Error code "Admission Control Failure (01)
   [RFC2205]" and Sub-code "Reverse LSP Failure" 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.




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6.  IANA Considerations

   IANA is requested to administer assignment of new values for
   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).  "Association
   Type" subregistry is included in this registry.

   This registry will be 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

   Specified Association Type values are temporary early allocations as
   per RFC7120.


6.2.  REVERSE_LSP Object

   IANA maintains the "RSVP Parameters" registry (see
   http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
    Class Names, Class Numbers, and Class Types subregistry is included
   in this registry.

   This registry will be 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

   Specified REVERSE_LSP Class Number and Class Type values are
   temporary early allocations as per RFC7120.





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6.3.  Reverse LSP Failure PathErr Sub-code

   IANA maintains the "RSVP Parameters" registry (see
   http://www.iana.org/assignments/rsvp-parameters/rsvp-parameters.xml).
   Error Codes and Globally-Defined Error Value Sub-Codes subregistry is
   included in this registry.

   This registry will be extended for the new PathErr Sub-code defined
   in this document as follows:


     Error Code = 01: "Admission Control Failure" (see [RFC2205])

     o  "Admission Control Failure/Reverse LSP Failure" (TBA)


   There are no other IANA considerations introduced by this document.


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.  The introduction of these
   types, by themselves, introduce no additional information to
   signaling.  Related security considerations are already covered for
   this in RFC6780.

   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 are
   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].


8.  Acknowledgement

   The authors would like to thank Lou Berger and George Swallow for
   their great guidance in this work, Jie Dong for the discussion of
   recovery, Lamberto Sterling for his valuable comments on the section
   of asymmetric bandwidths, Attila Takacs for the discussion of the
   provisioning model and Lou Berger, Daniel King and Deborah Brungard
   for the review of the document.  At the same time, the authors would
   also like to acknowledge the contributions of Bo Wu, Xihua Fu,



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   Lizhong Jin for the initial discussions, and Wenjuan He for the
   prototype implementation.  The authors would also like to thank Siva
   Sivabalan, Eric Osborne and Robert Sawaya for the discussions on the
   ASSOCIATION Object.  The authors would like to thank Matt Hartley for
   providing useful suggestions on the document and Lou Berger for
   careful editorial reviews.


9.  Contributing Authors

    Fan Yang
    ZTE

    Email: yang.fan240347@gmail.com


    Weilian Jiang
    ZTE

    Email: jiang.weilian@gmail.com































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10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2205]  Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

   [RFC3473]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.

   [RFC4872]  Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
              Extensions in Support of End-to-End Generalized Multi-
              Protocol Label Switching (GMPLS) Recovery", RFC 4872, May
              2007.

   [RFC4873]  Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
              "GMPLS Segment Recovery", RFC 4873, May 2007.

   [RFC6780]  Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
              Association Object Extensions", RFC 6780, October 2012.

   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF) - A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, April 2009.


10.2.  Informative References

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [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, February 2009.

   [RFC5654]  Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
              and S. Ueno, "Requirements of an MPLS Transport Profile",
              RFC 5654, September 2009.



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   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
              Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.

   [RFC6373]  Andersson, L., Berger, L., Fang, L., Bitar, N., and E.
              Gray, "MPLS Transport Profile (MPLS-TP) Control Plane
              Framework", RFC 6373, September 2011.

   [RFC6387]  Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
              Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
              Switched Paths (LSPs)", RFC 6387, September 2011.

   [RFC6689]  Berger, L., "Usage of The RSVP Association Object", RFC
              6689, July 2012.



































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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

































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