Network Working Group                                              Z. Li
Internet-Draft                                                   X. Chen
Intended status: Standards Track                                   N. Wu
Expires: May 3, 2017                                 Huawei Technologies
                                                        October 30, 2016


             PCEP Link-State extensions for Segment Routing
                  draft-li-pce-pcep-ls-sr-extension-01

Abstract

   Segment Routing leverages source routing.  A node steers a packet
   through a controlled set of instructions, called segments, by
   prepending the packet with an SR header.  A segment can represent any
   instruction, topological or service-based.  SR allows to enforce a
   flow through any topological path and service chain while maintaining
   per-flow state only at the ingress node of the SR domain.

   IGP protocols have been extended to advertise the segments.  Because
   of IGP's propagation scope limitation, it is not suited for IGP to
   signal paths that span across AS borders.  This document introduces
   extensions of PCEP-LS to solve the problem without the similar
   limitation.

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 3, 2017.




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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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   publication of this document.  Please review these 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
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  PCEP extensions for Segment Routing . . . . . . . . . . . . .   3
     2.1.  Node Attribute TLVs . . . . . . . . . . . . . . . . . . .   3
     2.2.  Link Attribute TLVs . . . . . . . . . . . . . . . . . . .   3
     2.3.  Prefix Attribute TLVs . . . . . . . . . . . . . . . . . .   4
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   4
     3.1.  Segment Routing report  . . . . . . . . . . . . . . . . .   4
     3.2.  Tunnel Segment Identifier . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Segment Routing [I-D.ietf-spring-segment-routing] leverages source
   routing.  A node steers a packet through a controlled set of
   instructions, called segments, by prepending the packet with an SR
   header.  A segment can represent any instruction, topological or
   service-based.  SR allows to enforce a flow through any topological
   path and service chain while maintaining per-flow state only at the
   ingress node of the SR domain.

   IGP protocols have been extended to advertise the segments.  Because
   of IGP's propagation scope limitation, it is not suited for IGP to
   signal paths that span across AS borders.





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   In order to fulfill the need for applications that require visibility
   of SR paths across IGP areas or even across ASes, this document
   defines extensions for the mechanism introduced in
   [I-D.dhodylee-pce-pcep-ls] to propagate SR information in those
   scenarios that have no IGP SR extension or BGP-LS running.

2.  PCEP extensions for Segment Routing

   PCEP-LS [I-D.dhodylee-pce-pcep-ls] introduces new message type and
   new object to accommodate link-state information in PCEP.  This
   document defines new additional TLVs to map segment routing
   information.  The value portion of these new TLVs can reuse the
   structure defined in [I-D.ietf-isis-segment-routing-extensions].

2.1.  Node Attribute TLVs

   Some new optional, non-transitive node attribute TLVs are defined for
   carrying segment routing information and are listed below:

+--------------+-----------------------+----------+-----------------------+
|TLV Code Point| Description           |   Length |     Value defined     |
+--------------+-----------------------+----------+-----------------------+
|     TBD1     | SID/Label Binding     | variable | [ISIS-SR]#section2.4  |
+--------------+-----------------------+----------+-----------------------+
|     TBD2     | SR-Capabilities       | variable | [ISIS-SR]#section3.1  |
+--------------+-----------------------+----------+-----------------------+
|     TBD3     | SR-Algorithm          | variable | [ISIS-SR]#section3.2  |
+--------------+-----------------------+----------+-----------------------+

   [ISIS-SR]: https://datatracker.ietf.org/doc/draft-ietf-isis-segment-
   routing-extensions/

   Table 1: Node Attribute TLVs

2.2.  Link Attribute TLVs

   Some new optional, non-transitive link attribute TLVs are defined for
   carrying segment routing information and are listed below:

+--------------+-----------------------+----------+-----------------------+
|TLV Code Point| Description           |   Length |     Value defined     |
+--------------+-----------------------+----------+-----------------------+
|     TBD4     | Adjacency Segment     | variable | [ISIS-SR]#section2.2.1|
+--------------+-----------------------+----------+-----------------------+
|     TBD5     | LAN Adjacency Segment | variable | [ISIS-SR]#section2.2.2|
+--------------+-----------------------+----------+-----------------------+
|     TBD6     | Tunnel Segment        | variable |                       |
+--------------+-----------------------+----------+-----------------------+



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   [ISIS-SR]: https://datatracker.ietf.org/doc/draft-ietf-isis-segment-
   routing-extensions/

   Table 2: Link Attribute TLVs

2.3.  Prefix Attribute TLVs

   A new optional, non-transitive link attribute TLVs are defined for
   carrying segment routing information and are listed below:

+--------------+-----------------------+----------+-----------------------+
|TLV Code Point| Description           |   Length |     Value defined     |
+--------------+-----------------------+----------+-----------------------+
|     TBD7     | Prefix Segment        | variable | [ISIS-SR]#section2.1.2|
+--------------+-----------------------+----------+-----------------------+

   [ISIS-SR]: https://datatracker.ietf.org/doc/draft-ietf-isis-segment-
   routing-extensions/

   Table 3: Prefix Attribute TLVs

3.  Operational Considerations

3.1.  Segment Routing report

   The procedure for segment routing information reporting from PCC to
   PCE will follow those defined in [I-D.dhodylee-pce-pcep-ls].

3.2.  Tunnel Segment Identifier

   Tunnel Segment introduced in [I-D.li-spring-tunnel-segment] is used
   to identify a tunnel of any kind in a segment routing network.  It is
   originated by the tunnel ingress node and one SID is allocated and
   attached to it either locally or globally.

4.  IANA Considerations

   TBD.

5.  Security Considerations

   TBD.

6.  Acknowledgements

   TBD.





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7.  References

7.1.  Normative References

   [I-D.dhodylee-pce-pcep-ls]
              Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for
              Distribution of Link-State and TE Information.", draft-
              dhodylee-pce-pcep-ls-06 (work in progress), September
              2016.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and j. jefftant@gmail.com,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-08 (work in progress), October
              2016.

   [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-09 (work in progress), July 2016.

   [I-D.li-spring-tunnel-segment]
              Li, Z. and N. Wu, "Tunnel Segment in Segment Routing",
              draft-li-spring-tunnel-segment-01 (work in progress),
              March 2016.

   [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>.

7.2.  Informative References

   [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>.

Authors' Addresses

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com



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Internet-DrafPCEP Link-State extensions for Segment Routing October 2016


   Xia Chen
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: jescia.chenxia@huawei.com


   Nan Wu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: eric.wu@huawei.com



































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