Update to Include Route Object (IRO) specification in Path Computation Element communication Protocol (PCEP)
draft-ietf-pce-iro-update-05

PCE Working Group                                               D. Dhody
Internet-Draft                                       Huawei Technologies
Updates: 5440 (if approved)                             January 27, 2016
Intended status: Standards Track
Expires: July 30, 2016

 Update to Include Route Object (IRO) specification in Path Computation
                 Element communication Protocol (PCEP)
                      draft-ietf-pce-iro-update-05

Abstract

   During discussions of a document to provide a standard representation
   and encoding of Domain-Sequence within the Path Computation Element
   (PCE) communication Protocol (PCEP) for communications between a Path
   Computation Client (PCC) and a PCE, or between two PCEs, it was
   determined that there was a need for clarification with respect to
   the ordered nature of the Include Route Object (IRO).

   An informal survey was conducted to determine the state of current
   and planned implementation with respect to IRO ordering and handling
   of Loose 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.

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   This Internet-Draft will expire on July 30, 2016.

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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
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.

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   [RFC5440] defines the Include Route Object (IRO) to specify network
   elements to be traversed in the computed path.  The specification did
   not mention if IRO is an ordered or un-ordered list of sub-objects.
   It mentioned that the Loose bit (L bit) has no meaning within an IRO.

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

   In order to discover the current state of affairs amongst
   implementations a survey of the existing and planned implementations
   was conducted.  This survey [I-D.dhody-pce-iro-survey] was informal
   and conducted via email.  Responses were collected and anonymized by
   the PCE working group chair.

   During discussion of [I-D.ietf-pce-pcep-domain-sequence] it was
   proposed to have a new IRO type with ordered nature, as well as
   handling of Loose bit (L bit); however, with the update to [RFC5440]
   described in this document, no new IRO type is needed.

   This document updates the IRO specifications in section 7.12 of
   [RFC5440] as per the conclusion and action points presented in
   [I-D.dhody-pce-iro-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 IRO as an optional object used to
   specify a set of network elements to be traversed in the computed
   path.  It also states that the Loose bit (L bit) in sub-object has no
   meaning within an IRO.  It did not mention if IRO is an ordered or
   un-ordered list of sub-objects.

   A survey of the existing and planned implementations was conducted in
   order to discover the current state of affairs amongst
   implementations.  [I-D.dhody-pce-iro-survey] describe the
   questionnaire, results and presents some conclusions and proposed
   action items.

   The survey suggest that most implementations construct or interpret
   IRO in an ordered fashion and consider it to be an ordered list.
   More than half of implementation under survey consider the IRO sub-
   objects as strict hops, others consider loose or support both.  The
   results shown in this survey seems to suggest that most

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   implementations would be fine with updating [RFC5440] to specify IRO
   as an ordered list as well as to enable support for Loose bit (L bit)
   such that both strict and loose hops could be supported in the IRO.

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 following
   two statements -

   - The content of IRO is an ordered list of sub-objects representing a
   series of abstract nodes.  An abstract node could just 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
   property of the sub-object, which 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 [I-D.dhody-pce-iro-survey], it should be noted
   that most implementation already support the update in the IRO
   specification as per this document.  The other implementation are
   expected to make an update to the IRO procedures based on this
   document.

   During the survey it was also noted that minority of the
   implementations, interpreted the IRO sub-objects as loose, when these
   implementation 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 PCE
      interprets them all as loose hops).  The PCC may check the

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      returned path and find the issue or it may end up using incorrect
      path.

   Thus it is RECOMMENDED that network operators ensure that all PCEP
   speakers in their network conform to this document with updated IRO
   specification 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 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], while [I-D.ietf-pce-pceps] discusses an
   experimental approach to provide secure transport for PCEP.

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>.

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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>.

   [I-D.ietf-pce-pcep-domain-sequence]
              Dhody, D., Palle, U., and R. Casellas, "Domain Subobjects
              for Path Computation Element (PCE) Communication Protocol
              (PCEP).", draft-ietf-pce-pcep-domain-sequence-12 (work in
              progress), December 2015.

   [I-D.ietf-pce-pceps]
              Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure
              Transport for PCEP", draft-ietf-pce-pceps-07 (work in
              progress), January 2016.

   [I-D.dhody-pce-iro-survey]
              Dhody, D., "Informal Survey into Include Route Object
              (IRO) Implementations in Path Computation Element
              communication Protocol (PCEP)", draft-dhody-pce-iro-
              survey-02 (work in progress), December 2014.

Author's Address

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   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560037
   India

   EMail: dhruv.ietf@gmail.com

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