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Internet Engineering Task Force (IETF)                          D. DhodyRequest for Comments: 7896                           Huawei TechnologiesUpdates:5440                                                  June 2016Category: Standards TrackISSN: 2070-1721Update to the Include Route Object (IRO) Specificationin 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 updatesRFC 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 inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7896.Dhody                        Standards Track                    [Page 1]

RFC 7896                IRO Specification Update               June 2016Copyright Notice   Copyright (c) 2016 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .32.  Update in the IRO Specification . . . . . . . . . . . . . . .32.1.  Update toRFC 5440  . . . . . . . . . . . . . . . . . . .33.  Operational Considerations  . . . . . . . . . . . . . . . . .44.  Security Considerations . . . . . . . . . . . . . . . . . . .45.  References  . . . . . . . . . . . . . . . . . . . . . . . . .45.1.  Normative References  . . . . . . . . . . . . . . . . . .45.2.  Informative References  . . . . . . . . . . . . . . . . .5   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .5   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .5Dhody                        Standards Track                    [Page 2]

RFC 7896                IRO Specification Update               June 20161.  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 inSection 7.12 of   [RFC5440].2.  Update in the IRO SpecificationSection 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 toRFC 5440   The IRO specification is updated to remove the last line in theSection 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.   -  The content of an IRO is an ordered list of subobjects      representing a series of abstract nodes (refer toSection 4.3.2 of      [RFC3209]).   -  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      perSection 4.3.3.1 of [RFC3209].Dhody                        Standards Track                    [Page 3]

RFC 7896                IRO Specification Update               June 20163.  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.  References5.1.  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 20165.2.  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 inSection 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.comDhody                        Standards Track                    [Page 5]