RSVP-TE Extensions for Associated Bidirectional LSPs
draft-ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp-02

CCAMP Working Group                                        F. Zhang, Ed.
Internet-Draft                                                       ZTE
Intended status: Standards Track                                 R. Jing
Expires: April 16, 2012                                    China Telecom
                                                        October 14, 2011

          RSVP-TE Extensions for Associated Bidirectional LSPs
         draft-ietf-ccamp-mpls-tp-rsvpte-ext-associated-lsp-02

Abstract

   The MPLS Transport Profile (MPLS-TP) requirements document [RFC5654],
   describes that MPLS-TP MUST support associated bidirectional point-
   to-point LSPs.

   This document provides a method to bind two unidirectional Label
   Switched Paths (LSPs) into an associated bidirectional LSP.  The
   association is achieved by using a new Association Type in the
   Extended ASSOCIATION object.

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."

   This Internet-Draft will expire on April 16, 2012.

Copyright Notice

   Copyright (c) 2011 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

Zhang & Jing             Expires April 16, 2012                 [Page 1]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   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
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Provisioning Model . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Signaling Procedure  . . . . . . . . . . . . . . . . . . .  4
       3.2.1.  Single Sided Provisioning Model  . . . . . . . . . . .  5
       3.2.2.  Double Sided Provisioning Model  . . . . . . . . . . .  5
       3.2.3.  Asymmetric Bandwidth LSPs  . . . . . . . . . . . . . .  6
       3.2.4.  Recovery Considerations  . . . . . . . . . . . . . . .  6
   4.  Association of LSPs  . . . . . . . . . . . . . . . . . . . . .  7
   5.  Single Sided Provisioning  . . . . . . . . . . . . . . . . . .  7
     5.1.  REVERSE_LSP Object . . . . . . . . . . . . . . . . . . . .  8
     5.2.  LSP Control  . . . . . . . . . . . . . . . . . . . . . . .  8
     5.3.  Updated RSVP Message Formats . . . . . . . . . . . . . . .  9
     5.4.  Compatibility  . . . . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Association Type . . . . . . . . . . . . . . . . . . . . . 10
     6.2.  REVERSE_LSP Object . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative references . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

Zhang & Jing             Expires April 16, 2012                 [Page 2]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

1.  Introduction

   The MPLS Transport Profile (MPLS-TP) requirements document [RFC5654]
   describes that MPLS-TP MUST support associated bidirectional point-
   to-point LSPs.  Furthermore, an associated bidirectional LSP is
   useful for protection switching, for Operations, Administrations and
   Maintenance (OAM) messages that require a reply path.

   The requirements described in [RFC5654] are specifically mentioned 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.

   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.

   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].

   The notion of association, as well as the corresponding Resource
   reSerVation Protocol (RSVP) ASSOCIATION object, is defined in
   [RFC4872], [RFC4873] and [I-D.ietf-ccamp-assoc-info] .  In that
   context, the object is used to associate recovery LSPs with the LSP
   they are protecting.  This object also has broader applicability as a
   mechanism to associate RSVP state, and [I-D.ietf-ccamp-assoc-ext]
   defines the Extended ASSOCIATION object that can be more generally
   applied.

   This document provides a method to bind two reverse unidirectional
   Label Switched Paths (LSPs) into an associated bidirectional LSP.
   The association is achieved by using a new Association Type in the
   Extended ASSOCIATION object.

Zhang & Jing             Expires April 16, 2012                 [Page 3]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

2.  Conventions used in this document

   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].

3.  Overview

3.1.  Provisioning Model

   The associated bidirectional LSP's forward and backward directions
   are set up, monitored, and protected independently as required by
   [RFC5654].  Configuration information regarding the LSPs can be sent
   to one end or both ends of the LSP.  Depending on the method chosen,
   there are two models of signaling associated bidirectional LSP.  The
   first model is the single sided provisioning, the second model is the
   double sided provisioning.

   For the single sided provisioning, the configurations are sent to one
   end.  Firstly, a unidirectional tunnel is configured on this end,
   then a LSP under this tunnel is initiated with the Extended
   ASSOCIATION object carried in the Path message to trigger the peer
   end to set up the corresponding reverse TE tunnel and LSP.

   For the double sided provisioning, the two unidirectional TE tunnels
   are configured independently, then the LSPs under the tunnels are
   signaled with the Extended ASSOCIATION objects carried in the Path
   message to indicate each other to associate the two LSPs together to
   be an associated bidirectional LSP.

   A number of scenarios exist for binding LSPs together to be an
   associated bidirectional LSP.  These include: (1) both of them do not
   exist; (2) both of them exist; (3) one LSP exists, but the other one
   need to be established.  In all scenarios described, the provisioning
   models discussed above are applicable.

3.2.  Signaling Procedure

   This section describes the signaling procedures for associating
   bidirectional LSPs.

   Consider the topology described in Figure 1.  (An example of
   associated bidirectional LSP).  The LSP1 [via nodes A,D,B] (from A to
   B) and LSP2 [via nodes B,D,C,A] (from B to A) are being established
   or have been established, which can form an associated bidirectional
   LSP between node A and node B.

Zhang & Jing             Expires April 16, 2012                 [Page 4]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   LSP1 and LSP2 are referenced at the data plane level by the
   identifiers: A-Node_ID::A-Tunnel_Num::A-LSP_Num::B-Node_ID and
   B-Node_ID::B-Tunnel_Num::B-LSP_Num::A-Node_ID, respectively
   [RFC6370].

                             A-------D-------B
                              \     /
                               \   /
                                \ /
                                 C

           Figure 1: An example of associated bidirectional LSP

3.2.1.  Single Sided Provisioning Model

   For the single sided provisioning model, LSP1 is triggered by LSP2 or
   LSP2 is triggered by LSP1.  When LSP2 is triggered by LSP1, LSP1 is
   initialized or refreshed (if LSP1 already exists) at node A with the
   Extended ASSOCIATION object inserted in the Path message, Association
   Type is set to "Associated Bidirectional LSPs", Association ID set to
   a value that uniquely identifies the sessions to be associated within
   the context of the Association Source field, Association Source set
   to A-Node_ID, Global Association Source set to A-Global_ID.  The
   Extended Association ID field must be included when the Association
   ID field is insufficient to uniquely identify association.  As
   described in [I-D.ietf-ccamp-assoc-ext], when included, this field
   must be set to a value that, together with the other fields in the
   object, uniquely identifies the sessions to be associated.
   Terminating node B is triggered to set up LSP2 by the received
   Extended ASSOCIATION object with the Association Type set to the
   value "Associated Bidirectional LSPs", the Association Object
   inserted in LSP2's Path message is the same as in LSP1's Path
   message.

   When LSP1 is triggered by LSP2, the same rules are applicable.  Based
   on the same values of the Association objects in the two LSPs' Path
   message, the two LSPs can be bound together to be an associated
   bidirectional LSP.

3.2.2.  Double Sided Provisioning Model

   For the double sided provisioning model, the values used in the
   Extended ASSOCIATION object are outside the scope of this document.
   For example they may be communicated via the management plane.  No
   matter how the values are communicate, identification of the LSPs as
   being Associated Bidirectional LSPs occurs based on the identical

Zhang & Jing             Expires April 16, 2012                 [Page 5]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   contents in the LSPs' Extended ASSOCIATION objects.

3.2.3.  Asymmetric Bandwidth LSPs

   A variety of applications, such as internet services and the return
   paths of OAM messages, exist and which MAY have different bandwidth
   requirements for each direction.  Additional [RFC5654] also specifies
   an asymmetric bandwidth requirement.  This requirement is
   specifically mentioned 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].  As to the asymmetric
   bandwidth associated bidirectional LSPs, the existing SENDER_TSPEC
   object must be carried in the REVERSE_LSP object as a sub-object in
   the initialized LSP's Path message to specify the reverse LSP's
   traffic parameters in case single sided provisioning model is
   adopted.  Consider the topology descirbed in Figure 1 in the context
   of asymmetric associated bidirectional LSP, and take LSP2 triggered
   by LSP1 as an example.  Node B is triggered to set up the reverse
   LSP2 with the corresponding asymmetric bandwidth by the Extended
   ASSOCIATION object with Association Type "Associated Bidirectional
   LSPs" and the SENDER_TSPEC sub-object in LSP1's Path message, and the
   SENDER_TSPEC object in the LSP2' Path message is the same as the the
   SENDER_TSPEC sub-object in LSP1's Path message.  When double sided
   provisioning model is used, the two opposite LSPs with asymmetric
   bandwidths are concurrently initialized, and this requirement will be
   satisfied simultanously.

3.2.4.  Recovery Considerations

   Consider the topology described in Figure 1, LSP1 and LSP2 form the
   associated bidirectional LSP.  Under the scenario of recovery, a
   third LSP (LSP3) may be used to protect LSP1.  LSP3 can be
   established before or after the failure occurs, it can share the same
   TE tunnel with LSP1 or not.

   When node A detects that LSP1 is broken, LSP3 will be initialized or
   refreshed with the Extended ASSOCIATION object inherited from LSP1's
   Path message.  In this way, based on the same Extended ASSOCIATION
   object, LSP2 and LSP3 will compose a new associated bidirectional
   LSP.

Zhang & Jing             Expires April 16, 2012                 [Page 6]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

4.  Association of LSPs

   The Extended ASSOCIATION object is defined in
   [I-D.ietf-ccamp-assoc-ext], which enables MPLS-TP required
   identification.  In order to bind two reverse unidirectional LSPs to
   be an associated bidirectional LSP, a new Association Type is defined
   in this document:

   o  Association Type:

   Value      Type
   -----      -----
   4 (TBD)    Associated Bidirectional LSPs (A)

   See [I-D.ietf-ccamp-assoc-ext] for the definition of other fields and
   values.

   As described in [I-D.ietf-ccamp-assoc-ext], association is always
   done based on matching Path state or Resv state.  Upstream
   initializted association is represented in Extended ASSOCIATION
   objects carried in Path message and downstream initializted
   association is represented in Extended ASSOCIATION objects carried in
   Resv messages.  The new defined Association Type in this document is
   only defined for use in upstream initialized association.  Thus it
   can only appear in Extended ASSOCIATION objects signaled in Path
   message.

   The rules associated with the processing of the Extended ASSOCIATION
   objects in RSVP message are discussed in [I-D.ietf-ccamp-assoc-ext].
   It said that in the absence of Association Type-specific rules for
   identifying association, the included Extended ASSOCIATION objects
   MUST be identical.  This document adds no specific rules, the
   association will always operate based on the same Extended
   ASSOCIATION objects.

5.  Single Sided Provisioning

   Path Computation Element (PCE)-based approaches, see [RFC4655], may
   be used for path computation of a GMPLS LSP, and consequently an
   associated bidirectional LSP, across domains and in a single domain.
   The ingress Label Switching Router (LSR), maybe serve as a PCE or
   Path Computation Client (PCC), have more information about the
   reverse LSP.  When the forward LSP is signaled, the reverse LSP's
   traffic parameters, explicit route, LSP attributes, etc, can be

Zhang & Jing             Expires April 16, 2012                 [Page 7]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   carried in the REVERSE_LSP object of the forward LSP's Path message.
   The Egress LSR can be triggered to establish the reverse LSP
   according to the control information.

5.1.  REVERSE_LSP Object

   The information of the reverse LSP is specified via the REVERSE_LSP
   object, which is optional with class numbers in the form 11bbbbbb has
   the following format:

   Class = TBD (of the form 11bbbbbb), C_Type = 1 (TBD)

       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)                          //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This object MUST NOT be used when the Extended ASSOCIATION object do
   not exist or exist but the Association Type is not "Associated
   Bidirectional LSPs".

   Subojects

   The contents of a REVERSE_LSP object are a series of variable-length
   data items called subobjects, which can be SENDER_TSPCE,
   EXPLICIT_ROUTE object (ERO), Session Attribute Object, Admin Status
   Object, LSP_ATTRIBUTES Object, LSP_REQUIRED_ATTRIBUTES Object,
   PROTECTION Object, ASSOCIATION Object, Extended ASSOCIATION Objects,
   etc.

5.2.  LSP Control

   The signaling procedure without the REVERSE_LSP object carried in the
   LSP1's Path message is described in section 3.2.1, which is the
   default option.  A node includes a REVERSE_LSP object and Extended
   ASSOCIATION object with an "Associated Bidirectional LSPs"
   Association Type in an outgoing Path message when it wishes to
   control the reverse LSP, and the receiver node B MUST convert the
   subobjects of the REVERSE_LSP object into the corresponding objects
   that carried in LSP2's Path message.  The case of a non-supporting
   egress node is outside of this document.  If node A want to tear down
   the associated bidirectional lSP, a PathTear message will be sent out

Zhang & Jing             Expires April 16, 2012                 [Page 8]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   and Node B is triggered to tear down LSP2.

5.3.  Updated 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> ]
                         [ <EXTENDED_ASSOCIATION> ... ]
                         [ <REVERSE_LSP]
                         [ <POLICY_DATA> ... ]
                         <sender descriptor>

   The format of the <sender descriptor> is not modified by the present
   document.

5.4.  Compatibility

   The REVERSE_LSP object is defined with class numbers in the form
   11bbbbbb, which ensures compatibility with non-supporting nodes.  Per
   [RFC2205], nodes not supporting this extension will ignore the object
   but forward it, unexamined and unmodified, in all messages resulting
   from this message.  Especially, this object received in PathTear, or
   PathErr messages should be forwarded immediately in the same message,
   but should be saved with the corresponding state and forwarded in any
   refresh message resulting from that state when received in Path
   message.

6.  IANA Considerations

   IANA is requested to administer assignment of new values for
   namespace defined in this document and summarized in this section.

Zhang & Jing             Expires April 16, 2012                 [Page 9]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

6.1.  Association Type

   Within the current document, a new Association Type is defined in the
   Extended ASSOCIATION object.

   Value      Type
   -----      -----
   4 (TBD)    Associated Bidirectional LSPs (A)

6.2.  REVERSE_LSP Object

   A new class named REVERSE_LSP has been created in the 11bbbbbb rang
   (TBD) with the following definition:

   Class Types or C-types (1, TBD):

   There are no other IANA considerations introduced by this document.

7.  Security Considerations

   This document introduces a new Association Type, and except this,
   there are no security issues about the Extended ASSOCIATION object
   are introduced here.

   The procedures defined in this document result in an increase in the
   amount of topology information carried in signaling messages since
   the presence of the REVERSE_LSP object necessarily means that there
   is more information about associated bidirectional LSPs.  Thus, in
   the event of the interception of a signaling message, slightly more
   could be deduced about the state of the network than was previously
   the case, but this is judged to be a very minor security risk as this
   information is already available via routing.

   Otherwise, this document introduces no additional security
   considerations.  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 for his great guidance in
   this work, George Swallow and Jie Dong for the discussion of
   recovery, Lamberto Sterling for his valuable comments on the section
   of asymmetric bandwidths, Daniel King for the review of the document,
   Attila Takacs for the discussion of the provisioning model.  At the

Zhang & Jing             Expires April 16, 2012                [Page 10]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

   same time, the authors would also like to acknowledge the
   contributions of Bo Wu, Xihua Fu, Lizhong Jin, and Wenjuan He for the
   initial discussions.

9.  References

9.1.  Normative references

   [I-D.ietf-ccamp-assoc-ext]
              Berger, L., Faucheur, F., and A. Narayanan, "RSVP
              Association Object Extensions",
              draft-ietf-ccamp-assoc-ext-00 (work in progress),
              May 2011.

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

   [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.

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

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

9.2.  Informative References

   [I-D.ietf-ccamp-assoc-info]
              Berger, L., "Usage of The RSVP Association Object",
              draft-ietf-ccamp-assoc-info-02 (work in progress),
              May 2011.

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

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

   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS

Zhang & Jing             Expires April 16, 2012                [Page 11]
Internet-Draft   RSVP-TE Extensions for Associated LSPs     October 2011

              Networks", RFC 5920, July 2010.

   [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.

Authors' Addresses

   Fei Zhang (editor)
   ZTE

   Email: zhang.fei3@zte.com.cn

   Ruiquan Jing
   China Telecom

   Email: jingrq@ctbri.com.cn

   Fan Yang 
   ZTE

   Email: yang.fan5@zte.com.cn
   
   
   Weilian Jiang 
   ZTE

   Email: jiang.weilian@zte.com.cn

Zhang & Jing             Expires April 16, 2012                [Page 12]