Network Working Group D. Voyer, Ed. Internet-Draft Bell Canada Intended status: Standards Track C. Filsfils Expires: December 3, 2020 R. Parekh Cisco Systems, Inc. H. Bidgoli Nokia Z. Zhang Juniper Networks June 1, 2020 SR Replication Segment for Multi-point Service Delivery draft-voyer-spring-sr-replication-segment-03 Abstract 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", "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 https://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 December 3, 2020. Voyer, Ed., et al. Expires December 3, 2020 [Page 1] Internet-Draft SR Replication Segment June 2020 Copyright Notice Copyright (c) 2020 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 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. Replication Segment . . . . . . . . . . . . . . . . . . . . . 2 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 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 Voyer, Ed., et al. Expires December 3, 2020 [Page 2] Internet-Draft SR Replication Segment June 2020 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 , where: o Replication-ID: An identifier for a Replication segment that is unique in context of the Replication Node. o Node-ID: The address of the Replication Node that the Replication segment is for. Note that the root of a Multi-point service is also a replication node. In simplest case, Replication-ID can be a 32-bit number, but it can be extended or modified as required based on specific use of a Replication segment. When the PCE signals a Replication segment to its node, the tuple identifies the segment. Examples of such signaling and extension are described in [I-D.voyer-pim-sr-p2mp-policy]. A Replication segment includes the 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. The Downstream Nodes and Replication State of a Replication segment can change over time, depending on the network state and leaf nodes of a Multi-point service that the segment is part of. Replication State is a list of replication branches to the Downstream Nodes. In this document, each branch is abstracted to a tuple. A 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, a Downstream Node could be represented by a SID-list or a Segment Routing Policy [I-D.ietf-spring-segment-routing-policy] that partially/fully specifies the explicit path from the Replication Node to the Downstream Node, or even represented by another Replication segment. Voyer, Ed., et al. Expires December 3, 2020 [Page 3] Internet-Draft SR Replication Segment June 2020 Replication SID identifies the Replication segment in the forwarding plane. For the root of a Multi-point service, 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. At a downstream node of the Multi-point service, the Replication SID MAY be used to identify that portion of the Multi-point service. 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 PUSH. 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 generalization. A node can be a bud node, i.e. it is a replication node and a leaf node of a Multi-point service at the same time [I-D.voyer-pim-sr-p2mp-policy]. In this case, the Replication segment's Replication State includes a branch with the Downstream Node being itself and the operation for the replicated copy is NEXT. 3. Use Cases In the simplest use case, a single Replication segment includes the root node of a Multi-point service and the egress/leaf nodes of the the service as all the Downstream Nodes. This achieves Ingress Replication [RFC7988] that has been widely used for MVPN [RFC6513] and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast) traffic. 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 specified in [I-D.voyer-pim-sr-p2mp-policy]. Voyer, Ed., et al. Expires December 3, 2020 [Page 4] Internet-Draft SR Replication Segment June 2020 4. IANA Considerations This document makes no request of IANA. 5. Security Considerations There are no additional security risks introduced by this design. 6. Acknowledgements The authors would like to acknowledge Siva Sivabalan, Mike Koldychev, Vishnu Pavan Beeram and Alexander Vainshtein for their valuable inputs. 7. Contributors Clayton Hassen Bell Canada Vancouver Canada Email: clayton.hassen@bell.ca Kurtis Gillis Bell Canada Halifax Canada Email: kurtis.gillis@bell.ca Arvind Venkateswaran Cisco Systems, Inc. San Jose US Email: arvvenka@cisco.com Zafar Ali Cisco Systems, Inc. US Email: zali@cisco.com Swadesh Agrawal Cisco Systems, Inc. San Jose US Voyer, Ed., et al. Expires December 3, 2020 [Page 5] Internet-Draft SR Replication Segment June 2020 Email: swaagraw@cisco.com Jayant Kotalwar Nokia Mountain View US Email: jayant.kotalwar@nokia.com Tanmoy Kundu Nokia Mountain View US Email: tanmoy.kundu@nokia.com Tarek Saad Juniper Networks Canada Email:tsaad@juniper.net 8. References 8.1. Normative References [I-D.ietf-spring-segment-routing-policy] Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", draft- ietf-spring-segment-routing-policy-07 (work in progress), May 2020. [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, . 8.2. Informative References Voyer, Ed., et al. Expires December 3, 2020 [Page 6] Internet-Draft SR Replication Segment June 2020 [I-D.voyer-pim-sr-p2mp-policy] Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z. Zhang, "Segment Routing Point-to-Multipoint Policy", draft-voyer-pim-sr-p2mp-policy-01 (work in progress), April 2020. [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February 2012, . [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, . [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 Montreal CA Email: daniel.voyer@bell.ca Clarence Filsfils Cisco Systems, Inc. Brussels BE Email: cfilsfil@cisco.com Rishabh Parekh Cisco Systems, Inc. San Jose US Email: riparekh@cisco.com Voyer, Ed., et al. Expires December 3, 2020 [Page 7] Internet-Draft SR Replication Segment June 2020 Hooman Bidgoli Nokia Ottawa CA Email: hooman.bidgoli@nokia.com Zhaohui Zhang Juniper Networks Email: zzhang@juniper.net Voyer, Ed., et al. Expires December 3, 2020 [Page 8]