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rfc:rfc7896

Internet Engineering Task Force (IETF) D. Dhody Request for Comments: 7896 Huawei Technologies Updates: 5440 June 2016 Category: Standards Track ISSN: 2070-1721

       Update to the Include Route Object (IRO) Specification
   in the Path Computation Element Communication Protocol (PCEP)

Abstract

 The Path Computation Element Communication Protocol (PCEP) enables
 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 does not specify if the IRO contains an ordered or
 unordered list of subobjects.  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 the handling of an attribute of the IRO's subobject, the L
 bit.
 This document updates RFC 5440 regarding the IRO specification.

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 7841.
 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/rfc7896.

Dhody Standards Track [Page 1] RFC 7896 IRO Specification Update June 2016

Copyright Notice

 Copyright (c) 2016 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.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
 2.  Update in the IRO Specification . . . . . . . . . . . . . . .   3
   2.1.  Update to RFC 5440  . . . . . . . . . . . . . . . . . . .   3
 3.  Operational Considerations  . . . . . . . . . . . . . . . . .   4
 4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
 5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
   5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
 Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

Dhody Standards Track [Page 2] RFC 7896 IRO Specification Update June 2016

1. Introduction

 The Path Computation Element Communication Protocol (PCEP) enables
 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 does not specify if the IRO is an ordered or
 unordered list of subobjects.  In addition, it defines the L bit as
 having 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.
 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 states that the L bit in the subobject has no
 meaning within an IRO.  It does not mention if the IRO contains an
 ordered or unordered list of subobjects.

2.1. Update to RFC 5440

 The IRO specification is updated to remove the last line in the
 Section 7.12 of [RFC5440], which states:
     "The L bit of such sub-object has no meaning within an IRO."
 Further, Section 7.12 of [RFC5440] is updated to add the following
 two statements at the end of the first paragraph.
  1. The content of an IRO is an ordered list of subobjects

representing a series of abstract nodes (refer to Section 4.3.2 of

    [RFC3209]).
  1. The L bit of an IRO subobject is set based on the loose or strict

hop property of the subobject; it is set if the subobject

    represents a loose hop.  If the bit is not set, the subobject
    represents a strict hop.  The interpretation of the L bit is as
    per Section 4.3.3.1 of [RFC3209].

Dhody Standards Track [Page 3] RFC 7896 IRO Specification Update June 2016

3. Operational Considerations

 Because of the lack of clarity in [RFC5440], it is possible to
 encounter implementations that always interpret the IRO subobjects 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 subobjects
    as loose hops, but the PCE interprets them as strict hops).
 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. References

5.1. Normative 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, 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>.

Dhody Standards Track [Page 4] RFC 7896 IRO Specification Update June 2016

5.2. 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>.

Acknowledgments

 A special thanks to the 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 shepherding the document and
 providing text in Section 3.
 Thanks to Deborah Brungard for her comments and being the responsible
 AD.
 Thanks to Peter Yee for the Gen-ART review.
 Thanks to Alvaro Retana for comments during the IESG review.

Author's Address

 Dhruv Dhody
 Huawei Technologies
 Divyashree Techno Park, Whitefield
 Bangalore, Karnataka  560066
 India
 Email: dhruv.ietf@gmail.com

Dhody Standards Track [Page 5]

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