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Versions: 00 01 02 03 draft-bashandy-isis-srv6-extensions

Network Working Group                                    S. Previdi, Ed.
Internet-Draft                                               L. Ginsberg
Intended status: Standards Track                             C. Filsfils
Expires: November 18, 2016                           Cisco Systems, Inc.
                                                            May 17, 2016


                    Segment Routing IPv6 Prefix-SID
                 draft-previdi-isis-ipv6-prefix-sid-02

Abstract

   This document defines the Segment Routing IPv6-Prefix-SID sub-TLV.
   This new sub-TLV allows to specify which of the prefixes advertised
   by a node are to be used as Segment Routing Identifiers (SID) for the
   IPv6 data plane.

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 RFC 2119 [RFC2119].

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-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 November 18, 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



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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IPv6 Prefix SID . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   With Segment Routing (SR)[I-D.ietf-spring-segment-routing], a node
   steers a packet through an ordered list of instructions, called
   segments.  Segments are identified through Segment Identifiers (SIDs)
   that are advertised by routing protocols.  The IS-IS extensions for
   SR information advertisement are defined in
   [I-D.ietf-isis-segment-routing-extensions].

   Segment Routing can be directly applied to the IPv6 data plane
   through the use of the Segment Routing Header defined in
   [I-D.ietf-6man-segment-routing-header].

   When applied to the IPv6 data plane, the SID is represented by an
   IPv6 address.  This document defines a new IS-IS Prefix sub-TLV where
   information related to the IPv6 address used as SR IPv6 SID is
   conveyed.

2.  IPv6 Prefix SID

   When SR is applied to the IPv6 data plane, Segment Identifiers (SIDs)
   are IPv6 addresses.  In a router, it is desirable to identify which
   of the local prefixes can be used as SIDs.  Also, and in order to
   provide the same functionalities defined in
   [I-D.ietf-spring-segment-routing] and according to
   [I-D.ietf-isis-segment-routing-extensions], a new sub-TLV is defined:
   the IPv6-Prefix-SID sub-TLV.





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   The IPv6-Prefix-SID sub-TLV is attached to an IPv6 prefix advertised
   by a node and MAY be present in any of the following TLVs:

      TLV-236 (IPv6) defined in [RFC5308].

      TLV-237 (MT-IPv6) defined in [RFC5120].

   The IPv6-Prefix-SID sub-TLV is optional, MAY appear only once for a
   given prefix and has the following format:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type        |     Length    |             Flags             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Algorithm   |                                              //
   +-+-+-+-+-+-+-+-+              Sub-TLVs                        //
   //                                                             //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

      Type: To be assigned by IANA (suggested value 5).

      Length: 3 + length of sub-TLVs.

      Flags: 2 octet field of flags.  None of them is defined at this
      stage.

      Algorithm: as defined in
      [I-D.ietf-isis-segment-routing-extensions].

      Sub-TLVs: additional information encoded into the IPv6-Prefix-SID
      Sub-TLV.  Currently, no sub-TLVs are defined yet.

   A prefix with an attached IPv6-Prefix-SID sub-TLV is defined as an
   SR-IPv6 Prefix SID.  If the prefix is to be used as a Node-SID
   (according to [I-D.ietf-isis-segment-routing-extensions]) then the
   following applies:

   o  The IPv6 prefix MUST be advertised with the IPv6-Prefix-SID sub-
      TLV attached.

   o  The Extended Reachability Attribute Flags sub-TLV defined in
      [RFC7794] MUST be attached to the prefix and the N-flag MUST be
      set.





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   When a router has attached an IPv6-Prefix-SID sub-TLV to a prefix, it
   implies that the router supports the Segment Routing Header (SRH,
   defined in [I-D.ietf-6man-segment-routing-header] and its associated
   procedures for packets destined to the advertised prefix.

   A router receiving an IPv6-Prefix-SID from a remote node and with an
   algorithm value that such remote node has not advertised in the SR-
   Capability sub-TLV (as defined in
   [I-D.ietf-isis-segment-routing-extensions]) MUST ignore the IPv6-
   Prefix-SID sub-TLV.

3.  IANA Considerations

   This document makes the following registrations in the "sub-TLVs for
   TLV 135, 235, 236 and 237" registry.

      Type: TBD (suggested value 5)

      Description: IPv6 Prefix Segment Identifier

      TLV 135: no

      TLV 235: no

      TLV 236: yes

      TLV 237: yes

      Reference: This document (Section 2)

4.  Security Considerations

   This document doesn't introduce new security considerations.

5.  Acknowledgements

   The authors would like to thank Nagendra Kumar for his review of this
   document.

6.  References

6.1.  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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   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <http://www.rfc-editor.org/info/rfc5120>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <http://www.rfc-editor.org/info/rfc5308>.

   [RFC7794]  Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
              U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
              and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
              March 2016, <http://www.rfc-editor.org/info/rfc7794>.

6.2.  Informative References

   [I-D.ietf-6man-segment-routing-header]
              Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
              J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment
              Routing Header (SRH)", draft-ietf-6man-segment-routing-
              header-01 (work in progress), March 2016.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
              Extensions for Segment Routing", draft-ietf-isis-segment-
              routing-extensions-06 (work in progress), December 2015.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-08 (work in progress), May 2016.

Authors' Addresses

   Stefano Previdi (editor)
   Cisco Systems, Inc.
   Via Del Serafico, 200
   Rome  00142
   Italy

   Email: sprevidi@cisco.com








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   Les Ginsberg
   Cisco Systems, Inc.
   US

   Email: ginsberg@cisco.com


   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   BE

   Email: cfilsfil@cisco.com






































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