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Versions: 00                                                            
SPRING WG                                                     Ting. Liao
Internet-Draft                                                  Ting. Ao
Intended status: Standards Track                         ZTE Corporation
Expires: April 21, 2016                                 October 19, 2015


                    SPRING IPv6 ListID Encapsulation
            draft-lt-6man-sr-listid-encapsulation-00.txt

Abstract

   Segment Routing allows a node to steer a packet through an ordered
   list of instructions, called segments.  The ingress node prepends a
   SR header to a packet containing a set of "segments".  A segment can
   represent any instruction topological or service-based.  Segment
   Routing can be applied to the IPv6 architecture, with a new type of
   routing extension header.  A segment is encoded as an IPv6 address.
   An ordered list of segments is encoded as an ordered list of IPv6
   addresses in the routing extension header.  The segment to process is
   indicated by a pointer in the routing extension header.  Upon
   completion of a segment, the pointer is incremented.  This document
   describes how to decrease the length of the IPv6 list with ListID
   carried.

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 April 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



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   (http://trustee.ietf.org/license-info) in effect on the date of
   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.  Conventions and Abbreviations . . . . . . . . . . . . . . . .   2
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  SLID Encapsulating  . . . . . . . . . . . . . . . . .   4
         3.1.1.1.  A new type of Routing Extension Header  . . . . .   4
         3.1.1.2.  R-flags defined in draft-previdi-6man-segment-
                   routing-header to identify  . . . . . . . . . . .   4
       3.1.2.  SLID Forwarding . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Segment Routing can be applied to the IPv6 data plane with the
   addition of a new type of Routing Extension Header as described in
   [I-D.previdi-6man-segment-routing-header].  A segment is encoded as
   an IPv6 address.  An ordered list of segments is encoded as an
   ordered list of IPv6 addresses in the routing extension header.
   There may be many specified nodes or links included in the path based
   on policy, each ipv6 address is 128 bits, this will greatly increase
   the length of header.  This document describes a method by mapping a
   segment list to a ListID and carrying the ListID in the header.  It
   will decrease the length of the segment routing header.

2.  Conventions and Abbreviations

   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] .

   The following notations and abbreviations are used throughout this
   draft.





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   SR:Segment Routing SID:Segment Identifier SLID: Segment List
   Identifier, a segment list is identified by a Segment list ID (SLID).

3.  Solution

   In this document, we define the Segment List Identifier (SLID).  The
   segment list is identified by a Segment list ID (SLID).  Segment list
   ID (SLID) is allocated by the controller.  The segment list and the
   SLID can be advertised to the related nodes.  When the node receives
   the mapping message, it generates a mapping table about the SLID to
   the Segment List.  The segment routing header could be a new type of
   Routing Extension Header, or be identified by the R-flags as defined
   in [I-D.previdi-6man-segment-routing-header].

3.1.  Example

   As shown in the figure 1.

                    __  +----------------------+
                  /   _ |      Controller      |  __
                 /   /  +----------------------+_   \
                /   /   |   |   |    |     | \    \   \
               /   /    |   |   |    |     |  \    \   \
         +---+    /  +---+  |   |  +---+   | +---+  \   \+---+
-------- |R1 |---/---|R3 |--|---|--|R5 |---|-|R7 |---\-- |R9 |
         +---+  /    +---+  |   |  +---+   | +---+    \  +---+
           |   /       |    /    \   |     \   |       \   |
           |  /        |   /      \  |      \  |        \  |
         +---+       +---+        +---+     +---+       +---+
         |R2 |-------|R4 |--------|R6 |-----|R8 |-------|R10|-----------
         +---+       +---+        +---+     +---+       +---+

                   Figure 1  Scenario 1

   In this example, we assumes that: o All nodes are SR capable.  o Each
   SR node has a global IPv6 address configured by operator to identify
   the node.  o The operator (likely via the SDN Controller) as
   provisioned the Node-SIDs 2001::1001, 2001::1002, 2001::1003,
   2001::1004, 2001::1005, 2001::1006, 2001::1007, 2001::1008,
   2001::1009,and 2001::1010 respectively at nodes R1, R2, R3, R4, R5,
   R6, R7, R8, R9 and R10.  o The controller computes a list for: {R1,
   R2, R4, R3, R5, R6, R8, R7, R9, and R10}, and allocates an unused ID
   2001::1100 to identify the segment list.  o The controller advertises
   the mapping Segment list ID (SLID) 2001::1100 for segment list {R1,
   R2, R4, R3, R5, R6, R8, R7, R9, and R10} to all the nodes in the
   list.  o Each node receives the mapping message, generates the
   mapping table of the SLID to the List.




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3.1.1.  SLID Encapsulating

3.1.1.1.  A new type of Routing Extension Header

   A new type of Routing Extension Headers is shown in the figure 2.
   The ingress node could encapsulate frames with SLID carried.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Next Header   |  Hdr Ext Len  | Routing Type  | Segments Left |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            RESV                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |            Segment List ID (128 bits ipv6 address)            |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 2  A new type of Routing Extension Header

   o Next Header: 8-bit selector.  Identifies the type of header
   immediately following the SRH.  o Hdr Ext Len: 8-bit unsigned
   integer, is the length of the SRH header in 8-octet units, not
   including the first 8 octets.  o Routing Type: TBD, to be assigned by
   IANA.  o Segments Left: It is optional, as defined in [RFC2460], it
   contains the index, in the Segment List, of the next segment to
   inspect.  Segments Left is decremented at each segment in the list.
   o RESV: Reserved and for future use.  o Segment List ID: 128 bit IPv6
   addresses identifying the Segment List.  Used to look up the next
   hop, and then the next hop exchanges the destination of the IPv6
   encapsulation.

3.1.1.2.  R-flags defined in draft-previdi-6man-segment-routing-header
          to identify

   As the R-flags have reserved and defined in
   [I-D.previdi-6man-segment-routing-header], such as one of R-flags
   set, it means the SLID instead of the Segment List[n] carrying in the
   encapsulation, there is no need to carry the segment
   list[0]...segment list[n] in this solution.

3.1.2.  SLID Forwarding

   As each node receives the mapping message, each node knows which one
   is the next node of itself.  Such as R1 receives the message of
   Segment list ID (SLID) 2001::1100 mapping to the segment list {R1,



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   R2, R4, R3, R5, R6, R8, R7, R9, and R10}, R1 will know R2 is my next
   segment in the LIST, and when some packets need to forward on the
   path of this list, it encapsulates the packet with the SLID
   2001::1100 carried, the destination of the packet is the addresses of
   R2 which is the next segment of R1.

   When the packet transit to R2, with the next header is routing
   extension header, and the routing extension header is the type of
   SLID carried, or the SRH carried with the R-flags to identify the
   SLID carried.  R2 learns the SLID 2001::1100 mapping to the segment
   list {R1, R2, R4, R3, R5, R6, R8, R7, R9, and R10}, and the next
   segment of R2 in this list is R4.  R2 changes the destination of this
   packet with the address of R4, and then the packet transits to R4.

   R4 knows R3, changes the destination,and the packet transits to R3.
   ... and then R10 receives the packet, it knows itself is the last
   segment in the list, and decapsulates the IPv6 SR header.

4.  Security Considerations

   TBD.

5.  Acknowledgements

   In progress.

6.  IANA Considerations

   TBD.

7.  Normative References

   [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.

   [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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   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <http://www.rfc-editor.org/info/rfc4915>.

   [RFC4970]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
              2007, <http://www.rfc-editor.org/info/rfc4970>.

   [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
              OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
              July 2008, <http://www.rfc-editor.org/info/rfc5250>.

Authors' Addresses

   Ting Liao
   ZTE Corporation
   No.50 Software Avenue
   Nanjing, Jiangsu  210012
   China

   Phone: +86 25 88016576
   Email: liao.ting@zte.com.cn


   Ting Ao
   ZTE Corporation
   No.889 Bibo Rd
   Shanghai  201203
   China

   Phone: +86 21 68897642
   Email: ao.ting@zte.com.cn

















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