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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
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
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This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
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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
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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.
- 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]).
- 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].
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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>.
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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
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