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Working Group                             Dave Allan, Uma Chunduri
Internet Draft                                                 Ericsson
Intended status: Standards Track
Expires: December 2016

                                                              June 2016


   OSPF extensions for Computed Multicast applied to MPLS based Segment
                                  Routing
                   draft-allan-ospf-spring-multicast-00


Abstract
   This document describes the OSPFv2 extensions required to support
   multicast for MPLS based Segment Routing. In this approach OSPF
   speakers compute their role in multicast tree construction based on
   the information in the OSPF routing information base.

Status of this Memo
   This Internet-Draft is submitted to IETF in full conformance
   with the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet
   Engineering Task Force (IETF), its areas, and its working
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   This Internet-Draft will expire on December 2016.

Copyright and License 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
   publication of this document. Please review these documents


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   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
   1.1. Authors......................................................2
   1.2. Requirements Language........................................3
   2. Conventions used in this document..............................3
   2.1. Terminology..................................................3
   3. Overview.......................................................3
   4. New TLVs.......................................................4
   4.1. Additional Router Information TLVs...........................4
   4.1.1. SRM Compute Capability TLV.................................4
   4.1.2. SRM SID Multicast Group Binding Sub-TLV....................4
   4.1.3. SRM Pinned Tree Descriptor sub-TLV.........................5
   5. Acknowledgements...............................................6
   6. Security Considerations........................................6
   7. IANA Considerations............................................7
   8. References.....................................................7
   8.1. Normative References.........................................7
   8.2. Informative References.......................................7
   9. Authors' Addresses.............................................8


1. Introduction

   [ALLAN-1] describes a solution for multicast for Segment Routing with
   MPLS data plane in which source specific multicast distribution trees
   (MDTs) are computed from information distributed via an IGP. Using
   this approach, both any-source multicast (ASM) and engineered p2mp
   trees can be supported.
   This memo describes three additional TLVs for OSPF to support the
   segment routing multicast approach described in [ALLAN-1]

1.1. Authors

   David Allan, Uma Chunduri






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1.2. 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 RFC2119 [RFC2119].

2. Conventions used in this document

2.1. Terminology

   Candidate replication point - is a node will potentially need to
   install state as determined at some intermediate step in MDT
   computation. It will either resolve to having no role or a role as a
   replication point once multicast has converged.

   Candidate role - refers to any potential combination of roles on a
   given MDT as determined at some intermediate step in MDT computation.
   For example, a node with a candidate role may be a leaf and may be a
   candidate replication point.

   Downstream - refers to the direction along the shortest path to one
   or more leaves for a given multicast distribution tree

   Multicast convergence - is when all computation and state
   installation to ensure the FIB reflects the multicast information in
   the IGP is complete.

   Pinned path - Is a unique shortest path extending from a leaf
   upstream towards the root for a given MDT. Therefore is a component
   of an MDT that must be there. It will not necessarily extend from the
   leaf all the way to the root during intermediate computation steps. A
   pinned path can result from pruning operations.

   Role - refers specifically to a node that is either a root, a leaf or
   a replication node for a given multicast distribution tree

   Unicast convergence- is when all computation and state installation
   to ensure the FIB reflects the unicast information in the IGP is
   complete.

   Upstream - refers to the direction along the shortest path to the
   root of a given multicast distribution tree

3. Overview

   The role of the IGP in the multicast architecture described in
   [ALLAN-1] is to synchronize knowledge of the topology, knowledge of


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   unicast SIDs, knowledge of multicast SIDs, multicast group membership
   and agreement on the algorithm to use for computation of multicast
   distribution trees(MDTs) across the set of IGP speakers. This
   document specifies the TLVs necessary for OSPF version 2 to be the
   IGP in said multicast architecture.

4. New TLVs

4.1. Additional Router Information TLVs

   The following three TLV are in the Router Information Opaque LSA
   specified in RFC 7770 for SRM compute capabilities and other TLVs in
   OSPFv2 Extended Prefix Opaque LSA as specified in [RFC7684].

4.1.1. SRM Compute Capability TLV

   The presence of this TLV in a router information LSA [RFC7770]
   indicates both that the originating node supports computed spring
   multicast, but also indicates the algorithm that is configured to be
   used. All nodes supporting computed multicast are required to agree
   on the algorithm for correct operation of the network.

   The format of the sub-TLV is:

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Algorithm OUI  (24 bits)               | Algorithm ID  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   The upper 24 bits contains an organizationally unique identifier (as
   per RFC 7042) and the lower 8 bits contains an algorithm identifier.

   The default algorithm supported as per [ALLAN-1] is identified by
   Algorithm OUI = 0x008037 (Ericsson), Algorithm ID = 0x01 (default).

4.1.2. SRM SID Multicast Group Binding Sub-TLV

   The SID Multicast Group Binding TLV communicates the binding between
   the SID specific to the MDT for the multicast group originating at
   the advertising node and the multicast group address, as well as
   transmit and receive interest for the advertising node. Note that if
   the sub-TLV does not have the T bit set, the SID TLV is not included


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   in the message. This sub-TLV is part of OSPFv2 Extended Prefix TLV as
   a sub-TLV from OSPFv2 Extended Prefix Opaque LSA as specified in
   [RFC7684].

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |T|R| Reserved  |                 Group address                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |                 SID sub-TLV                   |
   +-+-+-+-+-+-+-+-+                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Where:

      Type = TBD (IANA assignment from OSPFv2 Extended Prefix TLV Sub-
      TLVs Registry)

      Length = octet size of the T/R, reserved fields, Group ID and the
      SID sub-tlv information

      T-bit indicates that this node is a source for the multicast group
      specified in the sub-tlv.

      R-bit indicates that this node is a receiver for the multicast
      group specified in the sub-tlv.

      Group ID: 4 octet IPv4 multicast address

      SID sub-TLV = the segment ID to use for this source/group MDT. The
      format is as per the SID/label sub-TLV defined in section 2.1 of
      [SPRING-OSPF].

4.1.3. SRM Pinned Tree Descriptor sub-TLV

   The pinned tree descriptor defines all nodes that have a role in a
   multicast distribution tree, and their relationship to the individual
   multicast segments that define the tree. This sub-TLV is part of
   OSPFv2 Extended Prefix TLV as a sub-TLV from OSPFv2 Extended Prefix
   Opaque LSA as specified in [RFC7684]. The encoding is an unstructured
   list, where if the tree description exceeds the size, it may simply
   use more than one sub-TLV.





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   The encoding of a role descriptor is in the form of
   upstream_SID/unicast_SID/downstream _SID, where each of the SIDs is
   encoded as a sub-TLV as per [SPRING-OSPF].

   The root of the MDT (and originator of the TLV) will have a NULL
   upstream SID, transit waypoints will have both a defined upstream and
   downstream multicast segment SID, and a leaf will have a NULL
   downstream SID. The unicast SID corresponds to the node for which the
   entry defines its role.

    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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   role descriptor 1                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   role descriptor 2                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   role descriptor 3                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              . . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   role descriptor n                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Where:

      The encoding of a role descriptor is in the form:

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Upstream Multicast SID sub-TLV        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Unicast SID sub-TLV              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Downstream Multicast SID sub-TLV       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5. Acknowledgements



6. Security Considerations

   For a future version of this document.


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7. IANA Considerations

   This memo requires the assignment of 1 value from the OSPF Router
   Information (RI) TLV registry:

   -  SRM Compute Capability TLV

   This memo also requires the assignment of the following 2 Sub-TLV
   values from the OSPFv2 Extended Prefix TLV Sub-TLV registry:

   -  SRM SID Multicast Group Binding sub-TLV

   -  SRM Pinned Tree Descriptor sub-TLV

8. References

8.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC7042]  Eastlake, D. et. al.,"IANA Considerations and IETF
              Protocol and Documentation Usage for IEEE 802
              Parameters", IETF RFC 7042, October 2013

   [RFC7684]  Psenak et.al., "OSPFv2 Prefix/Link Attribute
              Advertisement", IETF RFC 7684, November 2015

   [RFC7770]  Lindem et.al., "Extensions to OSPF for Advertising
              Optional Router Capabilities", IETF RFC 7770, February
              2016

   [SPRING-OSPF] Psenak et.al., "OSPF Extensions for Segment Routing",
              IETF work in progress, draft-ietf-ospf-segment-routing-
              extensions-08, April 2016

8.2. Informative References

   [ALLAN-1]  Allan et.al., "A Framework for Computed Multicast applied
              to MPLS based Segment Routing", draft-allan-spring-mpls-
              mcast-framework-01, July 2016








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9. Authors' Addresses

   Dave Allan (editor)
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA
   Email: david.i.allan@ericsson.com

   Uma Chunduri
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA
   Email: uma.chunduri@ericsson.com


































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