draft-ietf-spring-sr-replication-segment-01.txt		draft-ietf-spring-sr-replication-segment-02.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: May 1, 2021 R. Parekh		Expires: May 2, 2021 R. Parekh
	Cisco Systems, Inc.		Cisco Systems, Inc.
	H. Bidgoli		H. Bidgoli
	Nokia		Nokia
	Z. Zhang		Z. Zhang
	Juniper Networks		Juniper Networks
	October 28, 2020		October 29, 2020
	SR Replication Segment for Multi-point Service Delivery		SR Replication Segment for Multi-point Service Delivery
	draft-ietf-spring-sr-replication-segment-01		draft-ietf-spring-sr-replication-segment-02
	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 May 1, 2021.		This Internet-Draft will expire on May 2, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 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		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3		2. Replication Segment . . . . . . . . . . . . . . . . . . . . . 3
	2.1. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.1.1. End.Replicate: Replicate and/or Decapsulate . . . . . 6		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	2.1.2. H.Encaps.Replicate: SR Headend encapsulation in		5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	Replication Segment . . . . . . . . . . . . . . . . . 7		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
	3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 7		7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 5
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 8		8.1. Normative References . . . . . . . . . . . . . . . . . . 6
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8		8.2. Informative References . . . . . . . . . . . . . . . . . 7
	7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8		Appendix A. Illustration of a Replication Segment . . . . . . . 7
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	8.1. Normative References . . . . . . . . . . . . . . . . . . 10
	8.2. Informative References . . . . . . . . . . . . . . . . . 10
	Appendix A. Illustration of a Replication Segment . . . . . . . 11
	A.1. SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 11
	A.2. SRv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 13
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
	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
	downstream nodes (without need for state on the transit routers).		downstream nodes (without need for state on the transit routers).
	Replication segments apply equally to both SR-MPLS and SRv6		This document focuses on the Replication Segment building block. The
	instantiations of Segment Routing. This document focuses on the		use of one or more stitched Replication Segments constructed for SR
	Replication Segment building block. The use of one or more stitched		P2MP Policy tree is specified in [I-D.voyer-pim-sr-p2mp-policy].
	Replication Segments constructed for SR P2MP Policy tree is specified
	in [I-D.ietf-pim-sr-p2mp-policy].
	2. Replication Segment		2. Replication Segment
	In a Segment Routing Domain, a Replication segment is a logical		In a Segment Routing Domain, a Replication segment is a logical
	construct which connects a Replication Node to a set of Downstream		construct which connects a Replication Node to a set of Downstream
	Nodes. A Replication segment is a local segment instantiated at a		Nodes. A Replication segment is a local segment instantiated at a
	Replication node. It can be either provisioned locally on a node or		Replication node. It can be either provisioned locally on a node or
	programmed by a PCE.		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,		A Replication segment is identified by the tuple <Replication-ID,
	Node-ID>, where:		Node-ID>, where:
	o Replication-ID: An identifier for a Replication segment that is		o Replication-ID: An identifier for a Replication segment that is
	unique in context of the Replication Node.		unique in context of the Replication Node.
	o Node-ID: The address of the Replication Node that the Replication		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		segment is for. Note that the root of a multi-point service is
	also a replication node.		also a replication node.
	In simplest case, Replication-ID can be a 32-bit number, but it can		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		be extended or modified as required based on specific use of a
	Replication segment. When the PCE signals a Replication segment to		Replication segment. When the PCE signals a Replication segment to
	its node, the <Replication-ID, Node-ID> tuple identifies the segment.		its node, the <Replication-ID, Node-ID> tuple identifies the segment.
	Examples of such signaling and extension are described in		Examples of such signaling and extension are described in
	[I-D.ietf-pim-sr-p2mp-policy].		[I-D.voyer-pim-sr-p2mp-policy].
	A Replication segment includes the following elements:		A Replication segment includes the following elements:
	o Replication SID: The Segment Identifier of a Replication segment.		o Replication SID: The Segment Identifier of a Replication segment.
	This is a SR-MPLS label or a SRv6 SID [RFC8402].		This is a SR-MPLS label or a SRv6 SID [RFC8402].
	o Downstream Nodes: Set of nodes in Segment Routing domain to which		o Downstream Nodes: Set of nodes in Segment Routing domain to which
	a packet is replicated by the Replication segment.		a packet is replicated by the Replication segment.
	o Replication State: See below.		o Replication State: See below.
	skipping to change at page 4, line 20 ¶		skipping to change at page 4, line 18 ¶
	plane. At a Replication node, the Replication SID is the equivalent		plane. At a Replication node, the Replication SID is the equivalent
	of Binding SID [I-D.ietf-spring-segment-routing-policy] of a Segment		of Binding SID [I-D.ietf-spring-segment-routing-policy] of a Segment
	Routing Policy.		Routing Policy.
	A packet steered into a Replication segment at a Replication node is		A packet steered into a Replication segment at a Replication node is
	replicated to each Downstream Node with the Downstream Replication		replicated to each Downstream Node with the Downstream Replication
	SID that is relevant at that node. A packet is steered into a		SID that is relevant at that node. A packet is steered into a
	Replication Segment in two ways:		Replication Segment in two ways:
	o When the Active Segment [RFC8402] is the Replication SID. In this		o When the Active Segment [RFC8402] is the Replication SID. In this
	case, the operation is NEXT followed by a PUSH for a replicated		case, the operation for a replicated copy is CONTINUE.
	copy.
	o On the root of a multi-point service, based on local policy-based		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		routing. In this case, the operation for a replicated copy is
	PUSH.		PUSH.
	If a Downstream Node is an egress (aka leaf) of the multi-point		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		service, i.e. no further replication is needed, then that leaf node's
	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]. In this case, the Replication		[I-D.voyer-pim-sr-p2mp-policy]. In this case, the Replication
	segment's Replication State includes a branch with the Downstream		segment's Replication State includes a branch with the Downstream
	Node being itself and the operation for the replicated copy is NEXT.		Node being itself and the operation for the replicated copy is NEXT.
	The Replication SID MUST be the last SID (at the bottom of stack for		The Replication SID MUST be the last SID (at the bottom of stack for
	SR-MPLS) in a packet that is steered out from a Replication node of a		SR-MPLS) in a packet that is steered out from a Replication node of a
	Replication Segment. The behavior at Downstream nodes of a		Replication Segment. The behavior at Downstream nodes of a
	Replication Segment is undefined If there are any SIDs after the		Replication Segment is undefined If there are any SIDs after the
	Replication SID and is outside the scope of this document.		Replication SID and is outside the scope of this document.
	2.1. SRv6
	SRv6 network programming [I-D.ietf-spring-srv6-network-programming]
	introduces concept of functions. A function defines local behavior
	on a node and is identified by opaque function part of a SRv6 SID.
	Familiarity with SRv6 Network Programming is expected.
	In SRv6, a Replication Segment can be realized by defining a SRv6
	Segment Endpoint behavior for replication. End.Replicate is an
	Endpoint function for replicating packets and, if required,
	decapsulation and processing of next header. This function is bound
	to a local SRv6 Replication SID at the Replication Node and
	Downstream Nodes of a Replication segment. FUNCT part of a
	Replication SID can represent both replication function as well the
	Replication State of a specific Replication Segment, or the
	Replication state MAY be represented by ARG part of Replication SID.
	For example, assuming two Replication Segments, RS1 and RS2 at a
	node, the node can bind two functions 0x00F1 and 0x00F2 (F=16, A=0)
	to End.Replicate function on Replication Segments RS1 and RS2
	respectively. The node can also choose to bind one function 0x00FA
	with End.Replicate and ARGs 0x0001 and 0x0002 (F=16, A=16) to RS1 and
	RS2 respectively.
	A Replication Node will replicate packet matching local SRv6
	Replication SID to all Downstream Nodes. Each replication is
	equivalent to pushing segment list of an SRv6 policy to a Downstream
	Node, If there is only one SID, the Downstream Replication SID and
	there is no need to use any Flag, Tag or TLV, the SRH MAY be omitted
	and the Downstream Replication SID is set as IPv6 DA in replicated
	copy of packet. In this case, the LOC part of routed Downstream
	Replication SID takes packet from Replication Node to the Downstream
	Node. If an SRH is inserted in a replicated copy of packet, the
	Downstream Replication SID MUST be the last Segment in SRH i.e at
	Segment List index 0.
	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 on packet wtih local Replication SID is decapsulation with
	processing of next header equivalent to End.DT46.
	A bud node performs both the replication and decapsulation part of
	End.Replicate function on a packet with local Replication SID.
	H.Encaps.Replicate is behavior on the root of a multipoint service to
	steer a packet into a SRv6 Replication Segment.
	Considerations of SRv6 Small SID/Compresion SID for SRv6 Replication
	SID will be addressed in future revision of this document.
	2.1.1. End.Replicate: Replicate and/or Decapsulate
	The "Endpoint with replication and/or decapsulate behavior
	(End.Replicate for short) is variant of End behavior.
	We define a generic Replicate function on a packet for Replication
	State (RS).
	S01. Replicate(RS, packet)
	S02. {
	S03. For each Replication R with Downstream Replication SID, R-SID {
	S04. Make copy of packet
	S05. If (NumSID(R)== 1) {
	S06. Set IPv6 DA = R-SID
	S07. Set NH-Header in copy to Next-Header value of packet
	S08. } Else {
	S09. Insert SRH with R-SID at SID List[0] followed by other SIDS
	S10. Set NH-Header of SRH to Next-Header value of packet
	S10. Set IPv6 DA = First SID of R
	S11. Set NH-Header in copy to SRH
	S12. }
	S13. Submit the packet to the egress IPv6 FIB lookup and
	transmission to the new destination
	S14. }
	When N receives a packet whose IPv6 DA is S and S is a local
	End.Replicate SID, N does:
	S01. Lookup FUNCT OR (FUNCT,ARG) portion of S to get Replication State RS
	S02. Call Replicate(RS, packet)
	S03. If NH==SRH and SL != 0 {
	S04. Send an ICMP Parameter Problem to the Source Address,
	Code 0 (Erroneous header field encountered),
	Pointer set to the Segments Left field,
	interrupt packet processing and discard the packet.
	S05. } Else If "decap check" success: {
	S06. Process packet according to End.DT46 behavior in SRv6 Network Programming
	S07. } Else {
	S08. Drop packet
	S09. }
	Notes:
	The "decap check" would succeed on egress or bud node. The SRv6
	Replication SID is bound to a specific tenant table at these nodes.
	2.1.2. H.Encaps.Replicate: SR Headend encapsulation in Replication
	Segment
	Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1;
	SL=1). B2 is neither a local address nor SID of N.
	Node N is configured with an IPv6 Address T (e.g. assigned to its
	loopback).
	N steers the transit packets P1 and P2 into an SRv6 Replication
	Segment, R, with a Source Address T and Replication State RS..
	The H.Encaps.Replicate encapsulation behavior is defined as follows:
	S01. Push an IPv6 header
	S02. Set outer IPv6 SA = T
	S03. Set outer Payload Length, Traffic Class, Hop Limit and
	Flow Label fields
	S04. Set the outer Next-Header value
	S05. Decrement inner IPv6 Hop Limit or IPv4 TTL
	S06. Call Replicate(RS, Outer packet)
	After the H.Encaps behavior, assuming a directly adjacent Downstream
	Node with Downstream Replication SID, D-RSID, P1' and P2'
	respectively look like:
	- (T, D-RSID) (A, B2)
	- (T, D-RSID) (A, B2) (B3, B2, B1; SL=1)
	After the H.Encaps behavior, assuming a non-adjacent Downstream Node
	with Downstream Replication SID, D-RSID and a Segment list <S1, S2>
	to reach Downstream Node, P1' and P2' respectively look like:
	- (T, S1) (D-RSID, S2, S1; SL=2) (A, B2)
	- (T, S1) (D-RSID, S2, S1; SL=2) (A, B2) (B3, B2, B1; SL=1)
	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
	the service as all the Downstream Nodes. This achieves Ingress		the 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
	replication trees when Replication segments on the root, intermediate		replication trees when Replication segments on the root, intermediate
	replication nodes and leaf nodes are stitched together to achieve		replication nodes and leaf nodes are stitched together to achieve
	efficient replication. That is specified in		efficient replication. That is specified in
	[I-D.ietf-pim-sr-p2mp-policy].		[I-D.voyer-pim-sr-p2mp-policy].
	4. IANA Considerations		4. IANA Considerations
	This document requires registration of End.Replicate behavior in		This document makes no request of IANA.
	"SRv6 Endpoint Behaviors" sub-registry of "Segment Routing
	Parameters" top-level registry.
	+-------+-----+------------------------+-----------+
	| Value | Hex | Endpoint behavior | Reference |
	+-------+-----+------------------------+-----------+
	| TBD | TBD | End.Replicate | [This.ID] |
	| TBD | TBD | End.Replicate with ARG | [This.ID] |
	+-------+-----+------------------------+-----------+
	Table 1: IETF - SRv6 Endpoint Behaviors
	5. Security Considerations		5. Security Considerations
	There are no additional security risks introduced by this design.		There are no additional security risks introduced by this design.
	6. Acknowledgements		6. Acknowledgements
	The authors would like to acknowledge Siva Sivabalan, Mike Koldychev,		The authors would like to acknowledge Siva Sivabalan, Mike Koldychev,
	Vishnu Pavan Beeram, Alexander Vainshtein, Bruno Decraene and Joel		Vishnu Pavan Beeram, Alexander Vainshtein, Bruno Decraene and Joel
	Halpern for their valuable inputs.		Halpern for their valuable inputs.
	skipping to change at page 10, line 15 ¶		skipping to change at page 6, line 48 ¶
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[I-D.ietf-spring-segment-routing-policy]		[I-D.ietf-spring-segment-routing-policy]
	Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and		Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
	P. Mattes, "Segment Routing Policy Architecture", draft-		P. Mattes, "Segment Routing Policy Architecture", draft-
	ietf-spring-segment-routing-policy-08 (work in progress),		ietf-spring-segment-routing-policy-08 (work in progress),
	July 2020.		July 2020.
	[I-D.ietf-spring-srv6-network-programming]
	Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
	Matsushima, S., and Z. Li, "SRv6 Network Programming",
	draft-ietf-spring-srv6-network-programming-24 (work in
	progress), October 2020.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,		[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
	Decraene, B., Litkowski, S., and R. Shakir, "Segment		Decraene, B., Litkowski, S., and R. Shakir, "Segment
	Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,		Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
	July 2018, <https://www.rfc-editor.org/info/rfc8402>.		July 2018, <https://www.rfc-editor.org/info/rfc8402>.
	8.2. Informative References		8.2. Informative References
	[I-D.filsfils-spring-srv6-net-pgm-illustration]		[I-D.voyer-pim-sr-p2mp-policy]
	Filsfils, C., Camarillo, P., Li, Z., Matsushima, S.,
	Decraene, B., Steinberg, D., Lebrun, D., Raszuk, R., and
	J. Leddy, "Illustrations for SRv6 Network Programming",
	draft-filsfils-spring-srv6-net-pgm-illustration-03 (work
	in progress), September 2020.
	[I-D.ietf-pim-sr-p2mp-policy]
	Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.		Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z.
	Zhang, "Segment Routing Point-to-Multipoint Policy",		Zhang, "Segment Routing Point-to-Multipoint Policy",
	draft-ietf-pim-sr-p2mp-policy-00 (work in progress), July		draft-voyer-pim-sr-p2mp-policy-02 (work in progress), July
	2020.		2020.
	[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>.
	[RFC7988] Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress		[RFC7988] Rosen, E., Ed., Subramanian, K., and Z. Zhang, "Ingress
	Replication Tunnels in Multicast VPN", RFC 7988,		Replication Tunnels in Multicast VPN", RFC 7988,
	DOI 10.17487/RFC7988, October 2016,		DOI 10.17487/RFC7988, October 2016,
	<https://www.rfc-editor.org/info/rfc7988>.		<https://www.rfc-editor.org/info/rfc7988>.
	Appendix A. Illustration of a Replication Segment		Appendix A. Illustration of a Replication Segment
	This section illustrates an example of a single Replication Segment.		This section illustrates an example of a single Replication Segment.
	Examples showing Replication Segment stitched together to form P2MP		Examples showing Replication Segment stitched together to form P2MP
	tree (based on SR P2MP policy) are in [I-D.ietf-pim-sr-p2mp-policy].		tree (based on SR P2MP policy) are in [I-D.voyer-pim-sr-p2mp-policy].
	Consider the following topology:		Consider the following topology:
	R3------R6		R3------R6
	/ \		/ \
	R1----R2----R5-----R7		R1----R2----R5-----R7
	\ /		\ /
	+--R4---+		+--R4---+
	Figure 1		Figure 1
	A.1. SR-MPLS
	In this example, the Node-SID of a node Rn is N-SIDn and Adjacency-		In this example, the Node-SID of a node Rn is N-SIDn and Adjacency-
	SID from node Rm to node Rn is A-SIDmn. Interface between Rm and Rn		SID from node Rm to node Rn is A-SIDmn. Interface between Rm and Rn
	is Lmn.		is Lmn.
	Assume a Replication Segment identified with R-ID at replication node		Assume a Replication Segment identified with R-ID at replication node
	R1 and downstream Nodes R2, R6 and R7. The Replication SID at node n		R1 and downstream Nodes R2, R6 and R7. The Replication SID at node n
	is R-SIDn. A packet replicated from R1 to R7 has to traverse R4.		is R-SIDn. A packet replicated from R1 to R7 has to traverse R4.
	The Replication Segment state at nodes R1, R2, R6 and R7 is shown		The Replication Segment state at nodes R1, R2, R6 and R7 is shown
	below. Note nodes R3, R4 and R5 do not have state for the		below. Note nodes R3, R4 and R5 do not have state for the
	skipping to change at page 12, line 8 ¶		skipping to change at page 8, line 25 ¶
	Replication Segment <R-ID,R1>:		Replication Segment <R-ID,R1>:
	Replication SID: R-SID1		Replication SID: R-SID1
	Replication State:		Replication State:
	R2: <R-SID2->L12>		R2: <R-SID2->L12>
	R6: <N-SID6, R-SID6>		R6: <N-SID6, R-SID6>
	R7: <N-SID4, A-SID47, R-SID7>		R7: <N-SID4, A-SID47, R-SID7>
	Replication to R2 steers packet directly to R2 on interface L12.		Replication to R2 steers packet directly to R2 on interface L12.
	Replication to R6, using N-SID6, steers packet via IGP shortest path		Replication to R6, using N-SID6, steers packet via IGP shortest path
	to that node. Replication to R7 is steered via R4, using N-SID4 and		to that node. Replication to R7 is steered via R4, using N-SID4 and
	then adjacency SID A-SID47 to R7.		then adjacency SID A-sID47 to R7.
	Replication Segment at R2:		Replication Segment at R2:
	Replication Segment <R-ID,R2>:		Replication Segment <R-ID,R2>:
	Replication SID: R-SID2		Replication SID: R-SID2
	Replication State:		Replication State:
	R2: <Leaf>		R2: <Leaf>
	Replication Segment at R6:		Replication Segment at R6:
	skipping to change at page 13, line 8 ¶		skipping to change at page 9, line 26 ¶
	o R1 performs PUSH operation with <N-SID4, A-SID47, R-SID7> label		o R1 performs PUSH operation with <N-SID4, A-SID47, R-SID7> label
	stack for the replicated copy to R7 and sends it to R2, the		stack for the replicated copy to R7 and sends it to R2, the
	nexthop on IGP shortest path to R4. R2 is the penultimate hop for		nexthop on IGP shortest path to R4. R2 is the penultimate hop for
	N-SID4; it performs penultimate hop popping, which corresponds to		N-SID4; it performs penultimate hop popping, which corresponds to
	the NEXT operation and the packet is then sent to R4 with		the NEXT operation and the packet is then sent to R4 with
	<A-SID47, R-SID1> in the label stack. R4 performs NEXT operation,		<A-SID47, R-SID1> in the label stack. R4 performs NEXT operation,
	pops A-SID47, and delivers packet to R7 with <R-SID7> in the label		pops A-SID47, and delivers packet to R7 with <R-SID7> in the label
	stack. R7, as Leaf, performs NEXT operation, pops R-SID7 label		stack. R7, as Leaf, performs NEXT operation, pops R-SID7 label
	and delivers the payload.		and delivers the payload.
	A.2. SRv6
	For SRv6 , we use SID allocation scheme, reproduced below, from
	Illustrations for SRv6 Network Programming
	[I-D.filsfils-spring-srv6-net-pgm-illustration]
	2001:db8::/32 is an IPv6 block allocated by a RIR to the operator
	2001:db8:0::/48 is dedicated to the internal address space
	2001:db8:cccc::/48 is dedicated to the internal SRv6 SID space
	We assume a location expressed in 64 bits and a function expressed
	in 16 bits
	Node k has a classic IPv6 loopback address 2001:db8::k/128 which
	is advertised in the IGP
	Node k has 2001:db8:cccc:k::/64 for its local SID space. Its SIDs
	will be explicitly assigned from that block
	Node k advertises 2001:db8:cccc:k::/64 in its IGP
	Function :1:: (function 1, for short) represents the End function
	with PSP support
	Function :Cn:: (function Cn, for short) represents the End.X
	function from to Node n
	Each node k has:
	An explicit SID instantiation 2001:db8:cccc:k:1::/128 bound to an
	End function with additional support for PSP
	An explicit SID instantiation 2001:db8:cccc:k:Cj::/128 bound to an
	End.X function to neighbor J with additional support for PSP
	An explicit SID instantiation 2001:db8:cccc:k:Fk::/128 bound to an
	End.Replcate function
	Assume a Replication Segment identified with R-ID at replication node
	R1 and downstream Nodes R2, R6 and R7. The Replication SID at node
	k, bound to an End.Replcate function, is 2001:db8:cccc:k:Fk::/128
	with ARG value 0. A packet replicated from R1 to R7 has to traverse
	R4.
	The Replication Segment state at nodes R1, R2, R6 and R7 is shown
	below. Note nodes R3, R4 and R5 do not have state for the
	Replication Segment.
	Replication Segment at R1:
	Replication Segment <R-ID,R1>:
	Replication SID: 2001:db8:cccc:1:F1::0
	Replication State:
	R2: <2001:db8:cccc:2:F2::0->L12>
	R6: <2001:db8:cccc:6:F6::0>
	R7: <2001:db8:cccc:4:C7::0, 2001:db8:cccc:7:F7::0>
	Replication to R2 steers packet directly to R2 on interface L12.
	Replication to R6, using 2001:db8:cccc:6:F6::0, steers packet via IGP
	shortest path to that node. Replication to R7 is steered via R4,
	using End.X SID 2001:db8:cccc:4:C7::0 at R4 to R7.
	Replication Segment at R2:
	Replication Segment <R-ID,R2>:
	Replication SID: 2001:db8:cccc:2:F2::0
	Replication State:
	R2: <Leaf>
	Replication Segment at R6:
	Replication Segment <R-ID,R6>:
	Replication SID: 2001:db8:cccc:6:F6::0
	Replication State:
	R6: <Leaf>
	Replication Segment at R7:
	Replication Segment <R-ID,R7>:
	Replication SID: 2001:db8:cccc:7:F7::0
	Replication State:
	R7: <Leaf>
	At R1, a H.Encaps.Replicate behavior is associated with the
	replication segment. When a packet, (A,B2), is steered into the
	replication segment at R1:
	o Since R1 is directly connected to R2, R1 creates encapsulated
	replicated copy (2001:db8::1, 2001:db8:cccc:2:F2::0) (A, B2), and
	sends it to R2 on interface L12. R2, as Leaf, executes
	decapsulation operation of End.Replicate, removes outer IPv6
	header and delivers the payload.
	o R1 creates encapsulated replicated copy (2001:db8::1,
	2001:db8:cccc:6:F6::0) (A, B2) then forwards the resulting packet
	on the shortest path to 2001:db8:cccc:6::/64. R2 and R3 forward
	the packet using 2001:db8:cccc:6::/64. R6, as Leaf, executes
	decapsulation operation of End.Replicate, removes outer IPv6
	header and delivers the payload.
	o R1 created encapsulated replicated copy (2001:db8::1,
	2001:db8:cccc:4:C7::0) (2001:db8:cccc:7:F7::0; SL=1) (A, B2) and
	sends it to R2, the nexthop on IGP shortest path to
	2001:db8:cccc:4::/64. R2 forwards packet to R4 using
	2001:db8:cccc:4::/64. R4 executes End.X function on
	2001:db8:cccc:4:C7::0, performs PSP action, removes SRH and sends
	resulting packet (2001:db8::1, 2001:db8:cccc:7:F7::0) (A, B2) to
	R4. R7, as Leaf, executes decapsulation operation of
	End.Replicate, removes outer IPv6 header and delivers the payload.
	Authors' Addresses		Authors' Addresses
	Daniel Voyer (editor)		Daniel Voyer (editor)
	Bell Canada		Bell Canada
	Montreal		Montreal
	CA		CA
	Email: daniel.voyer@bell.ca		Email: daniel.voyer@bell.ca
	Clarence Filsfils		Clarence Filsfils
End of changes. 20 change blocks.
	307 lines changed or deleted		28 lines changed or added
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