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Versions: (draft-voyer-spring-sr-p2mp-policy) 00 01 02 03 04

Network Working Group                                      D. Voyer, Ed.
Internet-Draft                                               Bell Canada
Intended status: Standards Track                             C. Filsfils
Expires: May 22, 2020                                          R. Parekh
                                                     Cisco Systems, Inc.
                                                              H. Bidgoli
                                                                Z. Zhang
                                                        Juniper Networks
                                                       November 19, 2019

        SR Replication Segment for Multi-point Service Delivery


   This document describes the SR Replication segment for Multi-point
   service delivery.  A SR Replication segment allows a packet to be
   replicated from a Replication node to downstream nodes.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 22, 2020.

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Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   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.  Replication segment . . . . . . . . . . . . . . . . . . . . .   2
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   We define a new type of segment for Segment Routing [RFC8402], called
   Replication segment, which allows a node (henceforth called as
   Replication node) to replicate packets to a set of other nodes
   (called Downstream nodes) in a Segment Routing Domain.  Replication
   segments provide building blocks for Point-to-Multi-point Service
   delivery.  A Replication segment at ingress node of Multi-point
   service could replicates packets directly to each egress node of the
   service (without need for any state on the internal routers), or it
   could be stitched to other Replication segments to build a tree in SR
   domain for Multi-point service.  The latter is outside the scope of
   this document but specified in [I-D.voyer-pim-sr-p2mp-policy].

2.  Replication segment

   In a Segment Routing Domain, a Replication segment is a logical
   segment which connects a Replication node to a set of Downstream
   nodes.  A Replication segment can be either provisioned locally on a

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   node or programmed by a PCE.  Replication segments apply equally to
   both SR-MPLS and SRv6 instantiations of Segment Routing.

   A Replication segment is identified by the tuple <Replication-ID,
   Node-ID>, where:

   o  Replication-ID: An identifier for a Replication segment that is
      unique in context of the Replication node.  This is an unsigned
      32-bit number.

   o  Node-ID: The address of a node at which a Replication segment is
      instantiated.  Replication segment is instantiated at Downstream
      nodes and at the replication nodes.  Note that the root of a
      Multi-point service is also a replication node.

   The Replicaion-ID can be extended or modified as required based on
   specific use of a Replication segment.

   A Replication segment is defined by following elements:

   o  Replication SID: The Segment Identifier of a Replication Segment.
      This is a SR-MPLS label or a SRv6 SID [RFC8402].

   o  Downstream Nodes: Set of nodes in Segment Routing domain to which
      a packet is replicated by the Replication segment.

   o  Replication State: See below.

   Replication state is a list of Replication branches to the Downstream
   nodes.  In this document, each branch is abstracted to a <Downstream
   Node, Downstream Replication-SID> tuple.  A Replication branch to a
   particular Downstream Node could be represented by the node's Node
   SID (i.e. it does not matter how traffic gets to the Downstream node,
   whether it's directly connected or not), or in case of a directly
   connected node it could be represented by the Adjacency SID (for the
   interface connecting to the directly connected Leaf Node).
   Alternatively, the Downstream Node could also be expanded to a SID-
   list that partially/fully specifies the explicit path to it.  A
   Replication branch can also use a Segment Routing Policy
   [I-D.ietf-spring-segment-routing-policy], if available, from the
   Replication node to the Downstream node.

   Replication SID identifies the Replication Segment in the forwarding
   plane.  The Replication SID SHOULD be considered to be the equivalent
   of Binding SID [I-D.ietf-spring-segment-routing-policy] of a Segment
   Routing Policy, when Replication Segment is instantiated at Ingress
   node of a Multi-point service.  At Downstream nodes, the Replication
   SID MAY be used to identify the Multi-point service.

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   A packet steered into a Replication Segment at a node is replicated
   to each Downstream node with the Downstream Replication SID that is
   relevant at that node.  A packet is steered into a Replication
   Segment in two ways:

   o  When the Active Segment [RFC8402] is the Replication SID.  In this
      case, the operation for a replicated copy is CONTINUE.

   o  On the root of a Multi-point service, based on local policy-based
      routing.  In this case, the operation for a replicated copy is

   Replication segments are instantiated for both a replication node
   itself and the downstream nodes of the Replication segment.  If a
   downstream node is an egress (aka leaf) of the Multi-point service,
   i.e. no further replication is needed, then that leaf node's
   replication segment will not have any replication state and the
   operation is NEXT.  Notice that the segment on the leaf node is still
   referred to as a Replication segment for the purpose of

3.  Use Cases

   In the simplest use case, a replication segment is instantiated on
   the root node of a Multi-point service, with all the downstream nodes
   being the egress/leaf nodes of the the service.  This achieves
   Ingress Replication [RFC7988] that has been widely used for MVPN
   [RFC6513] and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast)

   Replication segments can also be used as building blocks for
   replication trees when replication segments on the root, intermediate
   replication nodes and leaf nodes are stitched together to achieve
   efficient replciation.  That is outside the scope of this document
   but specified in [I-D.voyer-pim-sr-p2mp-policy].

4.  IANA Considerations

   This document makes no request of IANA.

5.  Security Considerations

   There are no additional security risks introduced by this design.

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6.  Acknowledgements

   The authors would like to acknowledge Siva Sivabalan, Mike Koldychev,
   Vishnu Pavan Beeram and Alexander Vainshtein for their valuable

7.  Contributors

   Clayton Hassen
   Bell Canada

   Email: clayton.hassen@bell.ca

   Kurtis Gillis
   Bell Canada

   Email: kurtis.gillis@bell.ca

   Arvind Venkateswaran
   Cisco Systems, Inc.
   San Jose

   Email: arvvenka@cisco.com

   Zafar Ali
   Cisco Systems, Inc.

   Email: zali@cisco.com

   Swadesh Agrawal
   Cisco Systems, Inc.
   San Jose

   Email: swaagraw@cisco.com

   Jayant Kotalwar
   Mountain View

   Email: jayant.kotalwar@nokia.com

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   Tanmoy Kundu
   Mountain View

   Email: tanmoy.kundu@nokia.com

   Tarek Saad
   Juniper Networks


8.  References

8.1.  Normative References

              Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-03 (work in progress),
              May 2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

8.2.  Informative References

              Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
              Zhang, "Segment Routing Point-to-Multipoint Policy",
              draft-voyer-pim-sr-p2mp-policy-00 (work in progress),
              October 2019.

   [RFC6513]  Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
              BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
              2012, <https://www.rfc-editor.org/info/rfc6513>.

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   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7988]  Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress
              Replication Tunnels in Multicast VPN", RFC 7988,
              DOI 10.17487/RFC7988, October 2016,

Authors' Addresses

   Daniel Voyer (editor)
   Bell Canada

   Email: daniel.voyer@bell.ca

   Clarence Filsfils
   Cisco Systems, Inc.

   Email: cfilsfil@cisco.com

   Rishabh Parekh
   Cisco Systems, Inc.
   San Jose

   Email: riparekh@cisco.com

   Hooman Bidgoli

   Email: hooman.bidgoli@nokia.com

   Zhaohui Zhang
   Juniper Networks

   Email: zzhang@juniper.net

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