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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: May 21, 2016                                Cisco Systems, Inc.
                                                       November 18, 2015


                    Segment Routing IPv6 Prefix-SID
                 draft-previdi-isis-ipv6-prefix-sid-00

Abstract

   This document defines the Segment Routing IPv6 Prefix-SID in the
   IPv4/IPv6 Extended Reachability Attribute Flags TLV.  The new flag is
   used for advertising the capability to handle the IPv6 Segment
   Routing header for the prefix that has the flag attached.

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 May 21, 2016.

Copyright Notice

   Copyright (c) 2015 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.  SRv6 Prefix SID . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

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 dataplane through
   the use of the Segment Routing Header defined in
   [I-D.previdi-6man-segment-routing-header].

2.  SRv6 Prefix SID

   When SR is applied to the IPv6 dataplane, Segment Identifiers (SIDs)
   are regular IPv6 addresses that are advertised in routing protocols.
   When SR is used over IPv6 dataplane, it is desirable to identify
   which of the prefixes originated by a node can be used as SIDs
   compared to any other prefix that the node advertises.

   [I-D.ietf-isis-prefix-attributes], defines the IPv4/IPv6 Extended
   Reachability Attribute Flags TLV.  This document defines the
   following new flag:

     S6-Flag (bit 3).
             SRv6 Prefix-SID flag: when set, the router
             indicates that the prefix this flag is attached
             to can be used as an IPv6 Prefix-SID.



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   The S6-Flag may also be set in conjunction with the Node-Flag (Bit 2)
   if the prefix does also identifies the node in the topology.

   In the case where the prefix has a shorter mask-length than 128 or
   when the prefix does not identify the node (e.g.: assigned to a
   physical interface instead of a loopback) the S6-Flag MAY be set and
   the N-flag MUST NOT be set.

   When a prefix is flagged as a SRv6-Prefix-SID, the originating router
   MUST support the IPv6 Segment Routing Header (SRH) and its procedures
   described in [I-D.previdi-6man-segment-routing-header].  Therefore
   the originating router MUST set the H-flag in the SR-Capability
   SubTLV as defined in [I-D.ietf-isis-segment-routing-extensions].

   A router receiving the advertisement of the IPv6 prefix with the
   S6-Flag set MUST check whether the originator has set the H-flag in
   its SR-Capability SubTLV if present in the receiving router link
   state database.

   The S6-Flag has relevance only for IPv6 prefixes.  When processing
   IPv4 prefixes, the S6-Flag MUST be ignored.

3.  IANA Considerations

   This document introduces the SRv6-Prefix-SID flag in the Prefix
   Attribute Flags sub-TLV:

   Name       Bit #
   -------    -----
   S6-Flag    3 (suggested value, to be assigned by IANA)

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








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   [I-D.ietf-isis-prefix-attributes]
              Ginsberg, L., Decraene, B., Filsfils, C., Litkowski, S.,
              Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix
              Attributes for Extended IP and IPv6 Reachability", draft-
              ietf-isis-prefix-attributes-01 (work in progress), June
              2015.

   [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>.

6.2.  Informative References

   [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-05 (work in progress), June 2015.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and r. rjs@rob.sh, "Segment Routing Architecture", draft-
              ietf-spring-segment-routing-06 (work in progress), October
              2015.

   [I-D.previdi-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-previdi-6man-segment-routing-
              header-08 (work in progress), October 2015.

Authors' Addresses

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

   Email: sprevidi@cisco.com


   Les Ginsberg
   Cisco Systems, Inc.
   US

   Email: ginsberg@cisco.com



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   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   BE

   Email: cfilsfil@cisco.com













































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