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Versions: (draft-gandhi-shah-teas-assoc-corouted-bidir) 00 01 02 03 04 draft-ietf-teas-assoc-corouted-bidir-frr

TEAS Working Group                                        R. Gandhi, Ed.
Internet-Draft                                             Cisco Systems
Intended Status: Standards Track                                 H. Shah
Expires: September 8, 2016                                         Ciena
                                                        Jeremy Whittaker
                                                                 Verizon
                                                           March 7, 2016


         RSVP-TE Extensions For Associated Co-routed Bidirectional
                        Label Switched Paths (LSPs)
             draft-gandhishah-teas-assoc-corouted-bidir-00


Abstract

   In packet transport networks, there are requirements where reverse
   unidirectional LSP of a bidirectional LSP needs to follow the same
   path as its forward unidirectional LSP.  This document describes how
   RSVP Extended ASSOCIATION Object can be used to bind two co-routed
   point-to-point unidirectional LSPs into an associated co-routed
   bidirectional LSP in single-sided provisioning case.  The RSVP
   REVERSE_LSP Object is used to enable an endpoint to trigger creation
   of the reverse LSP along the same path as the forward LSP.
   Fast-reroute procedures to ensure that the traffic flows on the
   co-routed path after a failure event are also described.


Status of this Memo

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   provisions of BCP 78 and BCP 79.

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Copyright and License Notice

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   described in the Simplified BSD License.





Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  3
     2.2.  Reverse Co-routed Unidirectional LSPs  . . . . . . . . . .  3
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Message and Object Definitions . . . . . . . . . . . . . . . .  4
     4.1.  Extended ASSOCIATION Object  . . . . . . . . . . . . . . .  4
   5.  Signaling Procedure  . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Co-routed Bidirectional LSP Association  . . . . . . . . .  6
     5.2.  Fast-Reroute For Associated Co-routed Bidirectional LSP  .  6
   6.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  8
     9.2.  Informative References . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9













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1.  Introduction

   In packet transport networks, there are requirements where a reverse
   LSP of a bidirectional LSP needs to follow the same path as its
   forward LSP [RFC6373].

   The RSVP Extended ASSOCIATION Object is specified in [RFC6780] which
   can be used generically to associate (G)MPLS LSPs.  [RFC7551] defines
   mechanisms for binding two point-to-point unidirectional LSPs
   [RFC3209] into an associated bidirectional LSP.  There are two models
   described for provisioning the LSP, single-sided and double-sided.
   The double-sided provisioned bidirectional LSPs are not considered in
   this document.

   The MPLS TP [RFC6370] architecture facilitates the co-routed
   bidirectional LSP by using GMPLS extensions [RFC3473] to achieve
   congruent paths.  The RSVP association signaling allows to take
   advantages of the co-routed bidirectional LSPs without having to
   deploy GMPLS extensions in the existing networks.  The association
   signaling also allows to take advantage of the existing TE mechanisms
   such as fast-reroute.

   [GMPLS-FRR] defines fast-reroute procedures for GMPLS signaled LSPs
   to ensure traffic flows on a co-routed path after a failure event on
   the primary LSP path.  [GMPLS-FRR] defined fast-reroute mechanisms
   are equally applicable to the associated co-routed bidirectional
   LSPs.

   This document describes how Extended ASSOCIATION Object can be used
   to bind two reverse co-routed unidirectional LSPs into an associated
   co-routed bidirectional LSP in single-sided provisioning case.  The
   REVERSE_LSP Object is used to enable an endpoint to trigger creation
   of the reverse LSP along the same path as the forward LSP.
   Fast-reroute procedures to ensure that the traffic flows on the
   co-routed path after a failure event are also described.


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 RFC 2119 [RFC2119].

2.2.  Reverse Co-routed Unidirectional LSPs

   Two reverse unidirectional LSPs are setup in the opposite directions



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   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.  A reverse co-routed unidirectional LSP traverses along
   the same path of the forward direction unidirectional LSP in the
   opposite direction.


3.  Overview

   For single-sided provisioning, the RSVP Traffic Engineering (TE)
   tunnel is configured only on one endpoint.  An LSP for this tunnel is
   initiated by the originating endpoint with Extended ASSOCIATION
   Object containing Association Type set to "single-sided associated
   bidirectional LSP" and REVERSE_LSP Object inserted in the Path
   message.  The remote 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 [RFC7551].  The reverse LSP thus created may or may not
   be congruent.


                       LSP1 -->
               +-----+           +-----+           +-----+
               |  A  +-----------+  C  +-----------+  B  |
               +-----+           +-----+           +-----+
                                          <-- LSP2

      Figure 1: An Example of Associated Co-routed Bidirectional LSP

   As shown in Figure 1, creation of reverse LSP2 on remote endpoint B
   is triggered by LSP1.  LSP2 follows the path in the reverse direction
   using the EXPLICIT_ROUTE Object (ERO) from the received REVERSE_LSP
   Object in the Path message of LSP1.

   For co-routed bidirectional LSP, the originating endpoint A ensures
   the reverse LSP follow the same path as the forward LSP by populating
   EXPLICIT_ROUTE Object in the REVERSE_LSP Object using the hops
   traversed by the forward LSP in the reverse order.



4.  Message and Object Definitions

4.1.  Extended ASSOCIATION Object

   The Extended ASSOCIATION Object is populated using the rules defined



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   in [RFC7551] for the Association Type "single-sided associated
   bidirectional LSP".

   The Extended Association ID is set by the originating node to the
   value specified as following.



       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      LSP Source Address                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Flags               |            LSP-ID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 2: IPv4 Extended Association ID Format




       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                      LSP Source Address                       |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Flags               |            LSP-ID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 3: IPv6 Extended Association ID Format



   LSP Source Address

      IPv4/IPv6 source address of the originating LSP.

   LSP-ID

      16-bits LSP-ID of the originating LSP.

   Flags

      Bit 0: COROUTED-LSP-FLAG: When set, this flag indicates the
      associated bidirectional LSP is co-routed.




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      Bit 1-15: Not used.  Must be set to 0.


5.  Signaling Procedure

5.1.  Co-routed Bidirectional LSP Association

   In general, the processing rules for the Extended ASSOCIATION Object
   as specified in [RFC6780] and [RFC7551] are followed for co-routed
   bidirectional LSP association.

   The originating head-end MUST add Extended ASSOCIATION Object with
   Association Type set to "single-sided associated bidirectional LSP"
   and the extended association ID as specified in Section 4.1 of this
   document.  The COROUTED-LSP-FLAG MUST be set to indicate the nodes on
   the LSP path that bidirectional LSP is co-routed.  In addition, the
   originating head-end node MUST add EXPLICIT_ROUTE Object (ERO) in the
   REVERSE_LSP Object by using the hops traversed by the forward LSP in
   the reverse order to ensure that reverse LSP follows the same path as
   forward direction LSP in the opposite direction.

   As defined in [RFC7551], the remote endpoint simply copies the
   content of the received Extended ASSOCIATION Object including the
   extended association ID in the reverse LSP Extended ASSOCIATION
   Object.  In addition, the remote endpoint builds the ERO of the
   reverse LSP using the ERO from the received REVERSE_LSP Object of the
   forward LSP.

   As contents of the Extended ASSOCIATION Object are unique for each
   associated co-routed bidirectional LSP, a node can unambiguously
   identify the associated LSP pair by matching their Extended
   ASSOCIATION Objects.   At a transit LSR, reverse LSP can identify the
   matching forward LSP by checking the originating LSP source address
   and LSP-ID in the extended association ID.  In addition, a node can
   identify an originating (forward) LSP by matching the LSP source
   address with the source address in the extended association ID.


5.2.  Fast-Reroute For Associated Co-routed Bidirectional LSP

   The procedures defined in [GMPLS-FRR] are used for associated
   co-routed bidirectional LSP to ensure that traffic flows on a
   co-routed path after a link or node failure.  The COROUTED-LSP-FLAG
   is used by the Point of Local Repair (PLR) nodes to provide fast-
   reroute protection using associated co-routed bypass tunnels.

   As described in [GMPLS-FRR], BYPASS_ASSIGNMENT subobject in RRO is
   used to co-ordinate bypass tunnel assignment between a forward and



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   reverse direction PLRs.  This subobject MUST be added by the forward
   direction PLR in the Path message of the originating LSP.  The
   reverse direction PLR (forward direction LSP merge-point (MP)) simply
   reflects the bypass tunnel assignment for the reverse direction LSP
   on the co-routed path.

   After a link or node failure, PLRs in both directions trigger fast-
   reroute independently using the procedures defined in [RFC4090].

   As specified in [GMPLS-FRR], re-corouting procedure can be used to
   reroute the traffic in the reverse direction on the co-routed bypass
   tunnel path.  Reverse direction PLR will assume the role of Point of
   Remote Repair (PRR) and trigger the fast-reroute in the reverse
   direction on the matching co-routed bypass tunnel to ensure that both
   traffic and RSVP signaling flow on the co-routed path after the
   failure.


6.  Compatibility

   The Extended ASSOCIATION Object has been defined in [RFC6780], with
   class number in the form 11bbbbbb, which ensures compatibility with
   non-supporting nodes.  Per [RFC2205], such nodes will ignore the
   object but forward it without modification.

   This document defines the content of the Extended Association ID for
   the Extended ASSOCIATION Object for co-routed bidirectional LSPs.
   Operators wishing to use this function SHOULD ensure that it is
   supported on the node that is expected to act on the association.


7.  Security Considerations

   This document uses signaling mechanisms defined in [RFC7551] and
   [GMPLS-FRR] and does not introduce any additional security
   considerations other than already covered in [RFC7551], [GMPLS-FRR]
   and the MPLS/GMPLS security framework [RFC5920].

   Using the extended association ID in the intercepted signalling
   message, a node may be able to get additional information of the LSP
   such as co-routed type and the originating node.  This is judged to
   be a very minor security risk as this information is already
   available by other means.

8.  IANA Considerations

   This document does not make any request for IANA action.




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9.  References

9.1.  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.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              May 2005.

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

   [RFC7551]  Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
              Extensions for Associated Bidirectional LSPs", RFC 7551,
              May 2015.

   [GMPLS-FRR] Taillon, M., Saad, T., Ed., Gandhi, R., Ed., Ali, Z.,
              Bhatia, M., Jin, L., "Extensions to Resource Reservation
              Protocol For Fast Reroute of Traffic Engineering GMPLS
              LSPs", draft-ietf-teas-gmpls-lsp-fastreroute.


9.2.  Informative References

   [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.

   [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.




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Authors' Addresses


   Rakesh Gandhi (editor)
   Cisco Systems, Inc.

   EMail: rgandhi.ietf@gmail.com


   Himanshu Shah
   Ciena

   EMail: hshah@ciena.com


   Jeremy Whittaker
   Verizon

   EMail: jeremy.whittaker@verizon.com
































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