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Versions: (draft-dhody-pce-iro-update) 00 01 02 03 04 05 06 07 RFC 7896

PCE Working Group                                               D. Dhody
Internet-Draft                                       Huawei Technologies
Updates: 5440 (if approved)                               March 14, 2016
Intended status: Standards Track
Expires: September 15, 2016


 Update to Include Route Object (IRO) specification in Path Computation
                 Element communication Protocol (PCEP)
                      draft-ietf-pce-iro-update-06

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.

   An informal survey was conducted to determine the state of current
   and planned implementations with respect to IRO ordering and the
   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, based
   on the survey conclusion and recommendation.

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-
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   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 September 15, 2016.





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Copyright Notice

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Table of Contents

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

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



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   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 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.  In
   order to understand the current usage amongst implementations, a
   survey of existing and planned implementations was conducted.  This
   survey was informal and conducted via email.  Responses were
   collected and anonymized by the PCE working group chair.

   This document updates the IRO specifications in section 7.12 of
   [RFC5440] as per the conclusion of the survey.

1.1.  Requirements Language

   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].

2.  Update in 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.

   A survey of the existing and planned implementations was conducted in
   order to understand the current state of usage amongst
   implementations.

   The survey found that most implementations construct or interpret the
   IRO in an ordered fashion and consider it to be an ordered list.
   More than half of implementations interpreted the IRO sub-objects as
   strict hops, others interpreted as loose or supported both
   interpretation.  The results shown in this survey found that most
   implementations support updating [RFC5440] to specify the IRO as an
   ordered list and supported the use of the Loose hop bit (L bit) such
   that both strict and loose hops could be supported in the IRO.








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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 -

   - The content of IRO is an ordered list of sub-objects representing a
   series of abstract nodes.  An abstract node could be a simple
   abstract node comprising one node or a group of nodes, for example an
   AS (comprising of multiple hops within the AS) (refer section 4.3.2
   of [RFC3209]).

   - The L Bit of 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 Loose bit (L bit) is as per section
   4.3.3.1 of [RFC3209].

3.  Other Considerations

   Based on the survey, it should be noted that most implementations
   already support this update in the IRO specification.  The other
   implementations are expected to make an update to the IRO procedures
   based on this document.

   During the survey, it was also noted that a minority of the
   implementations, interpreted 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 IRO sub-objects 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.






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   Thus it is RECOMMENDED that network operators ensure that all PCEP
   speakers in their network conform to this document if they intend to
   use IRO.

4.  Security Considerations

   This update in 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.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [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>.




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   [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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