Update to the Include Route Object (IRO) Specification in the Path Computation Element Communication Protocol (PCEP)
draft-ietf-pce-iro-update-07

PCE Working Group                                               D. Dhody
Internet-Draft                                       Huawei Technologies
Updates: 5440 (if approved)                               April 21, 2016
Intended status: Standards Track
Expires: October 23, 2016

 Update to Include Route Object (IRO) specification in Path Computation
                 Element communication Protocol (PCEP)
                      draft-ietf-pce-iro-update-07

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   for communications between a Path Computation Client (PCC) and a PCE,
   or between two PCEs.  RFC 5440 defines the Include Route Object (IRO)
   to specify network elements to be traversed in the computed path.
   The specification did not specify if the IRO contains an ordered or
   un-ordered list of sub-objects.  During recent discussions, it was
   determined that there was a need to define a standard representation
   to ensure interoperability.  It was also noted that there is a
   benefit in handling of an attribute of the IRO's sub-object, the
   Loose hop bit (L bit).

   This document updates RFC 5440 regarding the IRO specification.

Status of This Memo

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Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Update in the IRO specification . . . . . . . . . . . . . . .   3
     2.1.  Update to RFC 5440  . . . . . . . . . . . . . . . . . . .   3
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Path Computation Element Communication Protocol (PCEP) provides
   for communications between a Path Computation Client (PCC) and a PCE,
   or between two PCEs.  [RFC5440] defines the Include Route Object
   (IRO) to specify network elements to be traversed in the computed
   path.  The specification did not define if the IRO is an ordered or
   un-ordered list of sub-objects.  In addition, it defined the Loose
   hop bit (L bit) to have no meaning within an IRO.

   [RFC5441] describes the use of an IRO to indicate the sequence of
   domains to be traversed during inter-domain path computation.

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   During recent discussions, it was determined that there was a need to
   define a standard representation to ensure interoperability.

   This document updates the IRO specifications in section 7.12 of
   [RFC5440].

2.  Update in the IRO specification

   Section 7.12 of [RFC5440] describes the IRO as an optional object
   used to specify a set of network elements to be traversed in the
   computed path.  It stated that the Loose hop bit (L bit) in the sub-
   object has no meaning within an IRO.  It did not mention if the IRO
   contains an ordered or un-ordered list of sub-objects.

2.1.  Update to RFC 5440

   Section 7.12 of [RFC5440] regarding the IRO specification is updated
   to remove the last line in the section 7.12 of [RFC5440], that states
   :

       "The L bit of such sub-object has no meaning within an IRO."

   Further, the Section 7.12 of [RFC5440] is updated to add the
   following two statements at the end of the first paragraph.

   - The content of an IRO is an ordered list of sub-objects
   representing a series of abstract nodes (refer to section 4.3.2 of
   [RFC3209]).

   - The L Bit of an IRO sub-object is set based on the loose or strict
   hop property of the sub-object; it is set if the sub-object
   represents a loose hop.  If the bit is not set, the sub-object
   represents a strict hop.  The interpretation of the Loose bit (L bit)
   is as per section 4.3.3.1 of [RFC3209].

3.  Operational Considerations

   Because of the lack of clarity in [RFC5440], it is possible to
   encounter implementations that always interpret the IRO sub-objects
   as loose.  When these implementations interwork with an
   implementation conforming to this document, the following impact
   might be seen:

   o  If a non-conforming (to this document) PCC sends an IRO to a
      conforming (to this document) PCE, then the PCE may unexpectedly
      fail to find a path (since the PCC may think of the IRO sub-
      objects as loose hops, but the PCE interprets them as strict
      hops).

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   o  If a conforming PCC sends an IRO containing strict hops to a non-
      conforming PCE, then the PCE may erroneously return a path that
      does not comply with the requested strict hops (since the PCE
      interprets them all as loose hops).  The PCC may check the
      returned path and find the issue or it may end up using an
      incorrect path.

4.  Security Considerations

   This update in the IRO specification does not introduce any new
   security considerations, apart from those mentioned in [RFC5440].
   Clarification in the supported IRO ordering or Loose hop bit handling
   will not have any negative security impact.

   It is worth noting that PCEP operates over TCP.  An analysis of the
   security issues for routing protocols that use TCP (including PCEP)
   is provided in [RFC6952].

5.  IANA Considerations

   This document makes no requests to IANA for action.

6.  Acknowledgments

   A special thanks to PCE chairs for guidance regarding this work.

   Thanks to Francesco Fondelli for his suggestions in clarifying the L
   bit usage.

   Thanks to Adrian Farrel for his review and comments.

   Thanks to Jonathan Hardwick for document shepherding and providing
   text in Section 3.

   Thanks to Deborah Brungard for her comments and being the responsible
   AD.

   Thanks to Peter Yee for Gen-ART review.

   Thanks to Alvaro Retana for comments during the IESG review.

7.  References

7.1.  Normative References

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   [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>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <http://www.rfc-editor.org/info/rfc5440>.

7.2.  Informative References

   [RFC5441]  Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
              "A Backward-Recursive PCE-Based Computation (BRPC)
              Procedure to Compute Shortest Constrained Inter-Domain
              Traffic Engineering Label Switched Paths", RFC 5441,
              DOI 10.17487/RFC5441, April 2009,
              <http://www.rfc-editor.org/info/rfc5441>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <http://www.rfc-editor.org/info/rfc6952>.

Author's Address

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: dhruv.ietf@gmail.com

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