< draft-ietf-spring-sr-replication-segment-05.txt		draft-ietf-spring-sr-replication-segment-06.txt >
	Network Working Group D. Voyer, Ed.		Network Working Group D. Voyer, Ed.
	Internet-Draft Bell Canada		Internet-Draft Bell Canada
	Intended status: Standards Track C. Filsfils		Intended status: Standards Track C. Filsfils
	Expires: 21 February 2022 R. Parekh		Expires: 28 April 2022 R. Parekh
	Cisco Systems, Inc.		Cisco Systems, Inc.
	H. Bidgoli		H. Bidgoli
	Nokia		Nokia
	Z. Zhang		Z. Zhang
	Juniper Networks		Juniper Networks
	20 August 2021		25 October 2021
	SR Replication Segment for Multi-point Service Delivery		SR Replication Segment for Multi-point Service Delivery
	draft-ietf-spring-sr-replication-segment-05		draft-ietf-spring-sr-replication-segment-06
	Abstract		Abstract
	This document describes the SR Replication segment for Multi-point		This document describes the SR Replication segment for Multi-point
	service delivery. A SR Replication segment allows a packet to be		service delivery. A SR Replication segment allows a packet to be
	replicated from a Replication Node to downstream nodes.		replicated from a Replication Node to downstream nodes.
	Requirements Language		Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	skipping to change at page 1, line 44 ¶		skipping to change at page 1, line 44 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on 21 February 2022.		This Internet-Draft will expire on 28 April 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 27 ¶		skipping to change at page 2, line 27 ¶
	2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3		2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3
	2.1. SR-MPLS data plane . . . . . . . . . . . . . . . . . . . 4		2.1. SR-MPLS data plane . . . . . . . . . . . . . . . . . . . 4
	2.2. SRv6 data plane . . . . . . . . . . . . . . . . . . . . . 5		2.2. SRv6 data plane . . . . . . . . . . . . . . . . . . . . . 5
	3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5		3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 6		5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
	7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6		7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	8.1. Normative References . . . . . . . . . . . . . . . . . . 7		8.1. Normative References . . . . . . . . . . . . . . . . . . 7
	8.2. Informative References . . . . . . . . . . . . . . . . . 7		8.2. Informative References . . . . . . . . . . . . . . . . . 8
	Appendix A. Illustration of a Replication Segment . . . . . . . 8		Appendix A. Illustration of a Replication Segment . . . . . . . 8
	A.1. SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 9		A.1. SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 9
	A.2. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 10		A.2. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
	1. Introduction		1. Introduction
	We define a new type of segment for Segment Routing [RFC8402], called		We define a new type of segment for Segment Routing [RFC8402], called
	Replication segment, which allows a node (henceforth called as		Replication segment, which allows a node (henceforth called as
	Replication Node) to replicate packets to a set of other nodes		Replication Node) to replicate packets to a set of other nodes
	(called Downstream Nodes) in a Segment Routing Domain. Replication		(called Downstream Nodes) in a Segment Routing Domain. Replication
	segments provide building blocks for Point-to-Multipoint Service		segments provide building blocks for Point-to-Multipoint Service
	delivery via SR Point-to-Multipoint (SR P2MP) policy. A Replication		delivery via SR Point-to-Multipoint (SR P2MP) policy. A Replication
	segment can replicate packet to directly connected nodes or to		segment can replicate packet to directly connected nodes or to
	skipping to change at page 4, line 38 ¶		skipping to change at page 4, line 38 ¶
	Replication segment will not have any Replication State and the		Replication segment will not have any Replication State and the
	operation is NEXT. At an egress node, the Replication SID MAY be		operation is NEXT. At an egress node, the Replication SID MAY be
	used to identify that portion of the multi-point service. Notice		used to identify that portion of the multi-point service. Notice
	that the segment on the leaf node is still referred to as a		that the segment on the leaf node is still referred to as a
	Replication segment for the purpose of generalization.		Replication segment for the purpose of generalization.
	A node can be a bud node, i.e. it is a Replication Node and a leaf		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		node of a multi-point service at the same time
	[I-D.ietf-pim-sr-p2mp-policy].		[I-D.ietf-pim-sr-p2mp-policy].
	There MUST not be any topological SID after a Replication SID in a
	packet. Otherwise, the behavior at Downstream nodes of a Replication
	segment is undefined and outside the scope of this document.
	2.1. SR-MPLS data plane		2.1. SR-MPLS data plane
	When the Active Segment is a Replication SID, the processing results		When the Active Segment is a Replication SID, the processing results
	in a POP operation and lookup of the associated Replication state.		in a POP operation and lookup of the associated Replication state.
	For each replication in the Replication state, the operation is a		For each replication in the Replication state, the operation is a
	PUSH of the downstream Replication SID and an optional segment list		PUSH of the downstream Replication SID and an optional segment list
	on to the packet which is forwarded to the Downstream node. For leaf		on to the packet which is forwarded to the Downstream node. For leaf
	nodes the inner packet is forwarded as per local configuration.		nodes the inner packet is forwarded as per local configuration.
	When the root of a multi-point service steers a packet to a		When the root of a multi-point service steers a packet to a
	skipping to change at page 5, line 18 ¶		skipping to change at page 5, line 12 ¶
	the replication SID and an optional segment list on to the packet		the replication SID and an optional segment list on to the packet
	which is forwarded to the downstream node.		which is forwarded to the downstream node.
	2.2. SRv6 data plane		2.2. SRv6 data plane
	In SRv6 [RFC8986], the "Endpoint with replication" behavior		In SRv6 [RFC8986], the "Endpoint with replication" behavior
	(End.Replicate for short) replicates a packet and forwards the packet		(End.Replicate for short) replicates a packet and forwards the packet
	according to a Replication state.		according to a Replication state.
	When processing a packet destined to a local Replication-SID, the		When processing a packet destined to a local Replication-SID, the
	packet is replicated to Downstream nodes in the associated		packet is replicated to Downstream nodes and/or locally delivered off
	Replication state. For replication, the outer header is re-used, and		tree (when this is a bud/leaf node) according to the associated
			replication state. For replication, the outer header is re-used, and
	the Downstream Replication SID is written into the outer IPv6 header		the Downstream Replication SID is written into the outer IPv6 header
	destination address.If required, an optional segment list is used to		destination address. If required, an optional segment list may be
	encapsulate the replicated packet via H.Encaps. For a leaf node, the		used on some branches using H.Encaps.Red (while some other branches
	packet is decapsulated and the inner packet is forwarded as per local		may not need that). Note that this H.Encaps.Red is independent from
	configuration.		the replication segment - it is just used to steer the replicated
			traffic on a traffic engineered path to a Downstream node.
	When the root of a multi-point service steers a packet into a		The above also applies when the Replication segment is for the Root
	Replication segment, for each replication, H.Encaps is used to		node, whose upstream node has placed the Replication-SID in the
	encapsulate the packet with the segment list to the Downstream node .		header. A local application (e.g. MVPN/EVPN) may also apply
			H.Encaps.Red and then steer the resulting traffic into the segment.
			Again note that the H.Encaps.Red is independent of the Replication
			segment - it is the action of the application (e.g. MVPN/EVPN
			service). If the service is on a Root node, the two H.Encaps
			mentioned, one for the service and other in the previous paragraph
			for replication to Downstream node SHOULD be combined for
			optimization (to avoid extra IPv6 encapsulation).
	An End.Replicate SID MUST only appear as the ultimate SID in a SID-		For the local delivery on a bud/leaf node, the action associated with
	list. An implementation that receives a packet destined to a locally		Replication-SID is "look at next SID in SRH". The next SID could be
	instantiated End.Replicate SID that is not the ultimate segment		a SID with End.DT2/4/6 local behavior (equivalent of MVPN/EVPN PMSI
	SHOULD reply with ICMP Parameter Problem error (Erroneous header		label in case of tunnel sharing across multiple VPNs). There may
	field encountered) and discard the packet.		also not be a next SID (e.g. MVPN/EVPN with one tunnel per VPN), in
			which case the Replication-SID is then equivalent to End.DT2/4/6.
			Note that decapsulation is not an inherent action of a Replication
			segment even on a bud/leaf node.
	3. Use Cases		3. Use Cases
	In the simplest use case, a single Replication segment includes the		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		root node of a multi-point service and the egress/leaf nodes of the
	service as all the Downstream Nodes. This achieves Ingress		service as all the Downstream Nodes. This achieves Ingress
	Replication [RFC7988] that has been widely used for MVPN [RFC6513]		Replication [RFC7988] that has been widely used for MVPN [RFC6513]
	and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast) traffic.		and EVPN [RFC7432] BUM (Broadcast, Unknown and Multicast) traffic.
	Replication segments can also be used as building blocks for		Replication segments can also be used as building blocks for
	skipping to change at page 8, line 17 ¶		skipping to change at page 8, line 24 ¶
	srv6-net-pgm-illustration-04.txt>.		srv6-net-pgm-illustration-04.txt>.
	[I-D.ietf-lsr-flex-algo]		[I-D.ietf-lsr-flex-algo]
	Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and		Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
	A. Gulko, "IGP Flexible Algorithm", Work in Progress,		A. Gulko, "IGP Flexible Algorithm", Work in Progress,
	Internet-Draft, draft-ietf-lsr-flex-algo-17, 6 July 2021,		Internet-Draft, draft-ietf-lsr-flex-algo-17, 6 July 2021,
	<https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-		<https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-
	17.txt>.		17.txt>.
	[I-D.ietf-pim-sr-p2mp-policy]		[I-D.ietf-pim-sr-p2mp-policy]
	Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.		(editor), D. V., Filsfils, C., Parekh, R., Bidgoli, H.,
	Zhang, "Segment Routing Point-to-Multipoint Policy", Work		and Z. Zhang, "Segment Routing Point-to-Multipoint
	in Progress, Internet-Draft, draft-ietf-pim-sr-p2mp-		Policy", Work in Progress, Internet-Draft, draft-ietf-pim-
	policy-02, 19 February 2021,		sr-p2mp-policy-03, 23 August 2021,
	<https://www.ietf.org/archive/id/draft-ietf-pim-sr-p2mp-		<https://www.ietf.org/archive/id/draft-ietf-pim-sr-p2mp-
	policy-02.txt>.		policy-03.txt>.
	[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/		[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
	BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February		BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
	2012, <https://www.rfc-editor.org/info/rfc6513>.		2012, <https://www.rfc-editor.org/info/rfc6513>.
	[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,		[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
	Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based		Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
	Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February		Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
	2015, <https://www.rfc-editor.org/info/rfc7432>.		2015, <https://www.rfc-editor.org/info/rfc7432>.
End of changes. 13 change blocks.
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