rfc9252v3.txt		rfc9252.txt
	skipping to change at line 14 ¶		skipping to change at line 14 ¶
	Category: Standards Track K. Talaulikar, Ed.		Category: Standards Track K. Talaulikar, Ed.
	ISSN: 2070-1721 Cisco Systems		ISSN: 2070-1721 Cisco Systems
	R. Raszuk		R. Raszuk
	NTT Network Innovations		NTT Network Innovations
	B. Decraene		B. Decraene
	Orange		Orange
	S. Zhuang		S. Zhuang
	Huawei Technologies		Huawei Technologies
	J. Rabadan		J. Rabadan
	Nokia		Nokia
	June 2022		July 2022
	BGP Overlay Services Based on Segment Routing over IPv6 (SRv6)		BGP Overlay Services Based on Segment Routing over IPv6 (SRv6)
	Abstract		Abstract
	This document defines procedures and messages for SRv6-based BGP		This document defines procedures and messages for SRv6-based BGP
	services, including Layer 3 Virtual Private Network (L3VPN), Ethernet		services, including Layer 3 Virtual Private Network (L3VPN), Ethernet
	VPN (EVPN), and Internet services. It builds on "BGP/MPLS IP Virtual		VPN (EVPN), and Internet services. It builds on "BGP/MPLS IP Virtual
	Private Networks (VPNs)" (RFC 4364) and "BGP MPLS-Based Ethernet VPN"		Private Networks (VPNs)" (RFC 4364) and "BGP MPLS-Based Ethernet VPN"
	(RFC 7432).		(RFC 7432).
	skipping to change at line 120 ¶		skipping to change at line 120 ¶
	plane. This document defines procedures and messages for SRv6-based		plane. This document defines procedures and messages for SRv6-based
	BGP services, including L3VPN, EVPN, and Internet services. It		BGP services, including L3VPN, EVPN, and Internet services. It
	builds on "BGP/MPLS IP Virtual Private Networks (VPNs)" [RFC4364] and		builds on "BGP/MPLS IP Virtual Private Networks (VPNs)" [RFC4364] and
	"BGP MPLS-Based Ethernet VPN" [RFC7432].		"BGP MPLS-Based Ethernet VPN" [RFC7432].
	SRv6 SID refers to an SRv6 Segment Identifier, as defined in		SRv6 SID refers to an SRv6 Segment Identifier, as defined in
	[RFC8402].		[RFC8402].
	SRv6 Service SID refers to an SRv6 SID associated with one of the		SRv6 Service SID refers to an SRv6 SID associated with one of the
	service-specific SRv6 Endpoint Behaviors on the advertising PE		service-specific SRv6 Endpoint Behaviors on the advertising PE
	router, such as (but not limited to) End.DT (table look up in VPN		router, such as (but not limited to) End.DT (look up in the Virtual
	Routing and Forwarding (VRF)) or End.DX (cross-connect to a next hop)		Routing and Forwarding (VRF) table) or End.DX (cross-connect to a
	behaviors in the case of L3VPN service, as defined in [RFC8986].		next hop) behaviors in the case of L3VPN service, as defined in
	This document describes how existing BGP messages between PEs may		[RFC8986]. This document describes how existing BGP messages between
	carry SRv6 Service SIDs to interconnect PEs and form VPNs.		PEs may carry SRv6 Service SIDs to interconnect PEs and form VPNs.
	To provide SRv6 service with best-effort connectivity, the egress PE		To provide SRv6 service with best-effort connectivity, the egress PE
	signals an SRv6 Service SID with the BGP overlay service route. The		signals an SRv6 Service SID with the BGP overlay service route. The
	ingress PE encapsulates the payload in an outer IPv6 header where the		ingress PE encapsulates the payload in an outer IPv6 header where the
	destination address is the SRv6 Service SID provided by the egress		destination address is the SRv6 Service SID provided by the egress
	PE. The underlay between the PEs only needs to support plain IPv6		PE. The underlay between the PEs only needs to support plain IPv6
	forwarding [RFC8200].		forwarding [RFC8200].
	To provide SRv6 service in conjunction with an underlay Service Level		To provide SRv6 service in conjunction with an underlay Service Level
	Agreement (SLA) from the ingress PE to the egress PE, the egress PE		Agreement (SLA) from the ingress PE to the egress PE, the egress PE
	colors the overlay service route with a Color Extended Community		colors the overlay service route with a Color Extended Community
	[BGP-SR-POLICY] for steering flows for those routes, as specified in		[RFC9012] for steering flows for those routes, as specified in
	Section 8 of [SEGMENT-ROUTING-POLICY]. The ingress PE encapsulates		Section 8 of [SEGMENT-ROUTING-POLICY]. The ingress PE encapsulates
	the payload packet in an outer IPv6 header with the SR Policy segment		the payload packet in an outer IPv6 header with the SR Policy segment
	list associated with the related SLA along with the SRv6 Service SID		list associated with the related SLA along with the SRv6 Service SID
	associated with the route using the Segment Routing Header (SRH)		associated with the route using the Segment Routing Header (SRH)
	[RFC8754]. The underlay nodes whose SRv6 SIDs are part of the SRH		[RFC8754]. The underlay nodes whose SRv6 SIDs are part of the SRH
	segment list MUST support the SRv6 data plane.		segment list MUST support the SRv6 data plane.
	1.1. Requirements Language		1.1. 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 line 165 ¶		skipping to change at line 165 ¶
	[RFC8669] to carry SRv6 SIDs and their associated information with		[RFC8669] to carry SRv6 SIDs and their associated information with
	the BGP address families that are listed further in this section.		the BGP address families that are listed further in this section.
	The SRv6 Service TLVs are defined as two new TLVs of the BGP Prefix-		The SRv6 Service TLVs are defined as two new TLVs of the BGP Prefix-
	SID attribute to achieve signaling of SRv6 SIDs for L3 and L2		SID attribute to achieve signaling of SRv6 SIDs for L3 and L2
	services.		services.
	SRv6 L3 Service TLV:		SRv6 L3 Service TLV:
	This TLV encodes Service SID information for SRv6-based L3		This TLV encodes Service SID information for SRv6-based L3
	services. It corresponds to the equivalent functionality provided		services. It corresponds to the equivalent functionality provided
	by an MPLS Label when received with a Layer 3 service route, as		by an MPLS label when received with a Layer 3 service route, as
	defined in [RFC4364], [RFC4659], [RFC8950], and [RFC9136]. Some		defined in [RFC4364], [RFC4659], [RFC8950], and [RFC9136]. Some
	SRv6 Endpoint Behaviors that may be encoded, but not limited to,		SRv6 Endpoint Behaviors that may be encoded are, but not limited
	are End.DX4, End.DT4, End.DX6, End.DT6, and End.DT46.		to, End.DX4, End.DT4, End.DX6, End.DT6, and End.DT46.
	SRv6 L2 Service TLV:		SRv6 L2 Service TLV:
	This TLV encodes Service SID information for SRv6-based L2		This TLV encodes Service SID information for SRv6-based L2
	services. It corresponds to the equivalent functionality provided		services. It corresponds to the equivalent functionality provided
	by an MPLS Label1 for Ethernet VPN (EVPN) Route Types, as defined		by an MPLS label for Ethernet VPN (EVPN) Route Types for Layer 2
	in [RFC7432]. Some SRv6 Endpoint Behaviors that may be encoded		services, as defined in [RFC7432]. Some SRv6 Endpoint Behaviors
	are, but not limited to, End.DX2, End.DX2V, End.DT2U, and		that may be encoded are, but not limited to, End.DX2, End.DX2V,
	End.DT2M.		End.DT2U, and End.DT2M.
	When an egress PE is enabled for BGP Services over the SRv6 data		When an egress PE is enabled for BGP Services over the SRv6 data
	plane, it signals one or more SRv6 Service SIDs enclosed in an SRv6		plane, it signals one or more SRv6 Service SIDs enclosed in an SRv6
	Service TLV(s) within the BGP Prefix-SID attribute attached to		Service TLV(s) within the BGP Prefix-SID attribute attached to
	Multiprotocol BGP (MP-BGP) Network Layer Reachability Information		Multiprotocol BGP (MP-BGP) Network Layer Reachability Information
	(NLRI) defined in [RFC4760], [RFC4659], [RFC8950], [RFC7432],		(NLRI) defined in [RFC4760], [RFC4659], [RFC8950], [RFC7432],
	[RFC4364], and [RFC9136], where applicable, as described in Sections		[RFC4364], and [RFC9136], where applicable, as described in Sections
	5 and 6.		5 and 6.
	The support for BGP Multicast VPN (MVPN) Services [RFC6513] with SRv6		The support for BGP Multicast VPN (MVPN) Services [RFC6513] with SRv6
	skipping to change at line 224 ¶		skipping to change at line 224 ¶
	SRv6 Service Sub-TLVs (variable):		SRv6 Service Sub-TLVs (variable):
	This field contains SRv6 service-related information and is		This field contains SRv6 service-related information and is
	encoded as an unordered list of Sub-TLVs whose format is described		encoded as an unordered list of Sub-TLVs whose format is described
	below.		below.
	A BGP speaker receiving a route containing the BGP Prefix-SID		A BGP speaker receiving a route containing the BGP Prefix-SID
	attribute with one or more SRv6 Service TLVs observes the following		attribute with one or more SRv6 Service TLVs observes the following
	rules when advertising the received route to other peers:		rules when advertising the received route to other peers:
	* If the next hop is unchanged during the advertisement, the SRv6		* If the BGP next hop is unchanged during the advertisement, the
	Service TLVs, including any unrecognized Types of Sub-TLV and Sub-		SRv6 Service TLVs, including any unrecognized Types of Sub-TLV and
	Sub-TLV, SHOULD be propagated further. In addition, all Reserved		Sub-Sub-TLV, SHOULD be propagated further. In addition, all
	fields in the TLV, Sub-TLV, or Sub-Sub-TLV MUST be propagated		Reserved fields in the TLV, Sub-TLV, or Sub-Sub-TLV MUST be
	unchanged.		propagated unchanged.
	* If the next hop is changed, the TLVs, Sub-TLVs, and Sub-Sub-TLVs		* If the BGP next hop is changed, the TLVs, Sub-TLVs, and Sub-Sub-
	SHOULD be updated with the locally allocated SRv6 SID information.		TLVs SHOULD be updated with the locally allocated SRv6 SID
	Any unrecognized and received Sub-TLVs and Sub-Sub-TLVs MUST be		information. Any received Sub-TLVs and Sub-Sub-TLVs that are
	removed.		unrecognized MUST be removed.
	3. SRv6 Service Sub-TLVs		3. SRv6 Service Sub-TLVs
	The format of a single SRv6 Service Sub-TLV is depicted below:		The format of a single SRv6 Service Sub-TLV is depicted below:
	0 1 2 3		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		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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SRv6 Service | SRv6 Service | SRv6 Service //		| SRv6 Service | SRv6 Service | SRv6 Service //
	| Sub-TLV | Sub-TLV | Sub-TLV //		| Sub-TLV | Sub-TLV | Sub-TLV //
	skipping to change at line 311 ¶		skipping to change at line 311 ¶
	SRv6 Service SID Flags (1 octet):		SRv6 Service SID Flags (1 octet):
	This field encodes SRv6 Service SID Flags -- none are currently		This field encodes SRv6 Service SID Flags -- none are currently
	defined. It MUST be set to 0 by the sender and any unknown flags		defined. It MUST be set to 0 by the sender and any unknown flags
	MUST be ignored by the receiver.		MUST be ignored by the receiver.
	SRv6 Endpoint Behavior (2 octets):		SRv6 Endpoint Behavior (2 octets):
	This field encodes the SRv6 Endpoint Behavior codepoint value that		This field encodes the SRv6 Endpoint Behavior codepoint value that
	is associated with the SRv6 SID. The codepoints used are from		is associated with the SRv6 SID. The codepoints used are from
	IANA's "SRv6 Endpoint Behaviors" subregistry under the "Segment		IANA's "SRv6 Endpoint Behaviors" subregistry under the "Segment
	Routing" registry that was introduced by [RFC8986]. The opaque		Routing" registry that was introduced by [RFC8986]. The opaque
	Endpoint Behavior (i.e., value 0xFFFF) MAY be used when the		SRv6 Endpoint Behavior (i.e., value 0xFFFF) MAY be used when the
	advertising router wishes to abstract the actual behavior of its		advertising router wishes to abstract the actual behavior of its
	locally instantiated SRv6 SID.		locally instantiated SRv6 SID.
	RESERVED2 (1 octet):		RESERVED2 (1 octet):
	This field MUST be set to 0 by the sender and ignored by the		This field MUST be set to 0 by the sender and ignored by the
	receiver.		receiver.
	SRv6 Service Data Sub-Sub-TLV Value (variable):		SRv6 Service Data Sub-Sub-TLV Value (variable):
	This field is used to advertise properties of the SRv6 SID. It is		This field is used to advertise properties of the SRv6 SID. It is
	encoded as a set of SRv6 Service Data Sub-Sub-TLVs.		encoded as a set of SRv6 Service Data Sub-Sub-TLVs.
	The choice of SRv6 Endpoint Behavior of the SRv6 SID is entirely up		The choice of SRv6 Endpoint Behavior of the SRv6 SID is entirely up
	to the originator of the advertisement. While Sections 5 and 6 list		to the originator of the advertisement. While Sections 5 and 6 list
	the SRv6 Endpoint Behaviors that are normally expected to be used by		the SRv6 Endpoint Behaviors that are normally expected to be used by
	the specific route advertisements, the reception of other SRv6		the specific route advertisements, the reception of other SRv6
	Endpoint Behaviors (e.g., new behaviors that may be introduced in the		Endpoint Behaviors (e.g., new behaviors that may be introduced in the
	future) is not considered an error. An unrecognized Endpoint		future) is not considered an error. An unrecognized SRv6 Endpoint
	Behavior MUST NOT be considered invalid by the receiver, except for		Behavior MUST NOT be considered invalid by the receiver, except for
	behaviors that involve the use of arguments (refer to Section 3.2.1		behaviors that involve the use of arguments (refer to Section 3.2.1
	for details on argument validation). An implementation MAY log a		for details on argument validation). An implementation MAY log a
	rate-limited warning when it receives an unexpected behavior.		rate-limited warning when it receives an unexpected behavior.
	When multiple SRv6 SID Information Sub-TLVs are present, the ingress		When multiple SRv6 SID Information Sub-TLVs are present, the ingress
	PE SHOULD use the SRv6 SID from the first instance of the Sub-TLV.		PE SHOULD use the SRv6 SID from the first instance of the Sub-TLV.
	An implementation MAY provide a local policy to override this		An implementation MAY provide a local policy to override this
	selection.		selection.
	skipping to change at line 430 ¶		skipping to change at line 430 ¶
	Section 4 describes mechanisms for the signaling of the SRv6 Service		Section 4 describes mechanisms for the signaling of the SRv6 Service
	SID by transposing a variable part of the SRv6 SID value and carrying		SID by transposing a variable part of the SRv6 SID value and carrying
	this variable part in existing MPLS Label fields to achieve more		this variable part in existing MPLS Label fields to achieve more
	efficient packing of those service prefix NLRIs in BGP update		efficient packing of those service prefix NLRIs in BGP update
	messages. The SRv6 SID Structure Sub-Sub-TLV contains appropriate		messages. The SRv6 SID Structure Sub-Sub-TLV contains appropriate
	length fields when the SRv6 Service SID is signaled in split parts to		length fields when the SRv6 Service SID is signaled in split parts to
	enable the receiver to put together the SID accurately.		enable the receiver to put together the SID accurately.
	Transposition Offset indicates the bit position, and Transposition		Transposition Offset indicates the bit position, and Transposition
	Length indicates the number of bits that are being taken out of the		Length indicates the number of bits that are being taken out of the
	SRv6 SID value and put into high order bits of the MPLS Label field.		SRv6 SID value and encoded in the MPLS Label field. The bits that
	The bits that have been shifted out MUST be set to 0 in the SID		have been shifted out MUST be set to 0 in the SID value.
	value.
	A Transposition Length of 0 indicates nothing is transposed and that		A Transposition Length of 0 indicates nothing is transposed and that
	the entire SRv6 SID value is encoded in the SID Information Sub-TLV.		the entire SRv6 SID value is encoded in the SID Information Sub-TLV.
	In this case, the Transposition Offset MUST be set to 0.		In this case, the Transposition Offset MUST be set to 0.
	The size of the MPLS Label field limits the bits transposed from the		The size of the MPLS Label field limits the bits transposed from the
	SRv6 SID value into it. For example, the size of the MPLS Label		SRv6 SID value into it. For example, the size of the MPLS Label
	field is 20 bits in [RFC4364] and [RFC8277] and 24 bits in [RFC7432].		field is 20 bits in [RFC4364] and [RFC8277], and the size is 24 bits
			in [RFC7432].
	As defined in [RFC8986], the sum of the Locator Block Length (LBL),		As defined in [RFC8986], the sum of the Locator Block Length (LBL),
	Locator Node Length (LNL), Function Length (FL), and Argument Length		Locator Node Length (LNL), Function Length (FL), and Argument Length
	(AL) fields MUST be less than or equal to 128 and greater than the		(AL) fields MUST be less than or equal to 128 and greater than the
	sum of Transposition Offset and Transposition Length.		sum of Transposition Offset and Transposition Length.
	As an example, consider that the sum of the Locator Block and the		As an example, consider that the sum of the Locator Block and the
	Locator Node parts is 64. For an SRv6 SID where the entire Function		Locator Node parts is 64. For an SRv6 SID where the entire Function
	part of size 16 bits is transposed, the transposition offset is set		part of size 16 bits is transposed, the transposition offset is set
	to 64 and the transposition length is set to 16. While for an SRv6		to 64 and the transposition length is set to 16. While for an SRv6
	skipping to change at line 470 ¶		skipping to change at line 470 ¶
	specification MUST provide a mechanism to control the advertisement		specification MUST provide a mechanism to control the advertisement
	of SRv6-based BGP service routes on a per-neighbor and per-service		of SRv6-based BGP service routes on a per-neighbor and per-service
	basis. The details of deployment designs and implementation options		basis. The details of deployment designs and implementation options
	are outside the scope of this document.		are outside the scope of this document.
	Arguments may be generally applicable for SIDs of only specific SRv6		Arguments may be generally applicable for SIDs of only specific SRv6
	Endpoint Behaviors (e.g., End.DT2M); therefore, the AL MUST be set to		Endpoint Behaviors (e.g., End.DT2M); therefore, the AL MUST be set to
	0 for SIDs where the Argument is not applicable. A receiver is		0 for SIDs where the Argument is not applicable. A receiver is
	unable to validate the applicability of arguments for SRv6 Endpoint		unable to validate the applicability of arguments for SRv6 Endpoint
	Behaviors that are unknown to it and hence MUST ignore SRv6 SIDs with		Behaviors that are unknown to it and hence MUST ignore SRv6 SIDs with
	arguments (indicated by a non-zero AL) with unknown Endpoint		arguments (indicated by a non-zero AL) with unknown SRv6 Endpoint
	Behaviors. For SIDs corresponding to an Endpoint Behavior that is		Behaviors. For SIDs corresponding to an SRv6 Endpoint Behavior that
	known, a receiver MUST validate that the consistency of the AL with		is known, a receiver MUST validate that the consistency of the AL
	the specific Endpoint Behavior definition.		with the specific SRv6 Endpoint Behavior definition.
	4. Encoding SRv6 SID Information		4. Encoding SRv6 SID Information
	The SRv6 Service SID(s) for a BGP service prefix is carried in the		The SRv6 Service SID(s) for a BGP service prefix is carried in the
	SRv6 Services TLVs of the BGP Prefix-SID attribute.		SRv6 Services TLVs of the BGP Prefix-SID attribute.
	For certain types of BGP Services, like L3VPN where a per-VRF SID		For certain types of BGP Services, like L3VPN where a per-VRF SID
	allocation is used (i.e., End.DT4 or End.DT6 behaviors), the same SID		allocation is used (i.e., End.DT4 or End.DT6 behaviors), the same SID
	is shared across multiple NLRIs, thus providing efficient packing.		is shared across multiple NLRIs, thus providing efficient packing.
	However, for certain other types of BGP Services, like EVPN Virtual		However, for certain other types of BGP Services, like EVPN Virtual
	Private Wire Service (VPWS) where a per-PW SID allocation is required		Private Wire Service (VPWS) where a per-PW SID allocation is required
	(i.e., End.DX2 behavior), each NLRI would have its own unique SID,		(i.e., End.DX2 behavior), each NLRI would have its own unique SID,
	thereby resulting in inefficient packing.		thereby resulting in inefficient packing.
	To achieve efficient packing, this document allows 1) the encoding of		To achieve efficient packing, this document allows either 1) the
	the SRv6 Service SID as a whole in either the SRv6 Services TLVs or		encoding of the SRv6 Service SID as a whole in the SRv6 Services TLVs
	2) the encoding of only the common part of the SRv6 SID (e.g.,		or 2) the encoding of only the common part of the SRv6 SID (e.g.,
	Locator) in the SRv6 Services TLVs and the encoding of the variable		Locator) in the SRv6 Services TLVs and the encoding of the variable
	(e.g., Function or Argument parts) in the existing label fields		(e.g., Function or Argument parts) in the existing label fields
	specific to that service encoding. This later form of encoding is		specific to that service encoding. This later form of encoding is
	referred to as the Transposition Scheme, where the SRv6 SID Structure		referred to as the Transposition Scheme, where the SRv6 SID Structure
	Sub-Sub-TLV describes the sizes of the parts of the SRv6 SID and also		Sub-Sub-TLV describes the sizes of the parts of the SRv6 SID and also
	indicates the offset of the variable part along with its length in		indicates the offset of the variable part along with its length in
	the SRv6 SID value. The use of the Transposition Scheme is		the SRv6 SID value. The use of the Transposition Scheme is
	RECOMMENDED for the specific service encodings that allow it, as		RECOMMENDED for the specific service encodings that allow it, as
	described further in Sections 5 and 6.		described further in Sections 5 and 6.
	skipping to change at line 565 ¶		skipping to change at line 565 ¶
	and egress PE while also encoding the SRv6 Endpoint Behavior.		and egress PE while also encoding the SRv6 Endpoint Behavior.
	When steering for SRv6 services is based on shortest path forwarding		When steering for SRv6 services is based on shortest path forwarding
	(e.g., best effort or IGP Flexible Algorithm [IGP-FLEX-ALGO]) to the		(e.g., best effort or IGP Flexible Algorithm [IGP-FLEX-ALGO]) to the
	egress PE, the ingress PE encapsulates the IPv4 or IPv6 customer		egress PE, the ingress PE encapsulates the IPv4 or IPv6 customer
	packet in an outer IPv6 header (using H.Encaps or H.Encaps.Red		packet in an outer IPv6 header (using H.Encaps or H.Encaps.Red
	flavors specified in [RFC8986]), where the destination address is the		flavors specified in [RFC8986]), where the destination address is the
	SRv6 Service SID associated with the related BGP route update.		SRv6 Service SID associated with the related BGP route update.
	Therefore, the ingress PE MUST perform a resolvability check for the		Therefore, the ingress PE MUST perform a resolvability check for the
	SRv6 Service SID before considering the received prefix for the BGP		SRv6 Service SID before considering the received prefix for the BGP
	best path computation. The resolvability is evaluated, as per		best path computation. The resolvability is evaluated as per
	[RFC4271]. If the SRv6 SID is reachable via more than one forwarding		[RFC4271]. If the SRv6 SID is reachable via more than one forwarding
	table, local policy is used to determine which table to use. The		table, local policy is used to determine which table to use. The
	result of an SRv6 Service SID resolvability (e.g., when provided via		result of an SRv6 Service SID resolvability (e.g., when provided via
	IGP Flexible Algorithm) can be ignored if the ingress PE has a local		IGP Flexible Algorithm) can be ignored if the ingress PE has a local
	policy that allows an alternate steering mechanism to reach the		policy that allows an alternate steering mechanism to reach the
	egress PE. The details of such steering mechanisms are outside the		egress PE. The details of such steering mechanisms are outside the
	scope of this document.		scope of this document.
	For service over SRv6 core, the egress PE sets the BGP next hop to		For service over SRv6 core, the egress PE sets the BGP next hop to
	one of its IPv6 addresses. Such an address MAY be covered by the		one of its IPv6 addresses. Such an address MAY be covered by the
	SRv6 Locator from which the SRv6 Service SID is allocated. The next		SRv6 Locator from which the SRv6 Service SID is allocated. The BGP
	hop is used for tracking the reachability of the egress PE based on		next hop is used for tracking the reachability of the egress PE based
	existing BGP procedures.		on existing BGP procedures.
	When the BGP route received at an ingress PE is colored with a Color		When the BGP route received at an ingress PE is colored with a Color
	Extended Community and a valid SRv6 Policy is available, the steering		Extended Community and a valid SRv6 Policy is available, the steering
	for service flows is performed as described in Section 8 of		for service flows is performed as described in Section 8 of
	[SEGMENT-ROUTING-POLICY]. When the ingress PE determines (with the		[SEGMENT-ROUTING-POLICY]. When the ingress PE determines (with the
	help of the SRv6 SID Structure) that the Service SID belongs to the		help of the SRv6 SID Structure) that the Service SID belongs to the
	same SRv6 Locator as the last SRv6 SID (of the egress PE) in the SR		same SRv6 Locator as the last SRv6 SID (of the egress PE) in the SR
	Policy segment list, it MAY exclude that last SRv6 SID when steering		Policy segment list, it MAY exclude that last SRv6 SID when steering
	the service flow. For example, the effective segment list of the		the service flow. For example, the effective segment list of the
	SRv6 Policy associated with SID list <S1, S2, S3> would be <S1, S2,		SRv6 Policy associated with SID list <S1, S2, S3> would be <S1, S2,
	skipping to change at line 702 ¶		skipping to change at line 702 ¶
	SRv6 Service SID before considering the received prefix for the BGP		SRv6 Service SID before considering the received prefix for the BGP
	best path computation. The resolvability is evaluated as per		best path computation. The resolvability is evaluated as per
	[RFC4271]. If the SRv6 SID is reachable via more than one forwarding		[RFC4271]. If the SRv6 SID is reachable via more than one forwarding
	table, local policy is used to determine which table to use. The		table, local policy is used to determine which table to use. The
	result of an SRv6 Service SID resolvability (e.g., when provided via		result of an SRv6 Service SID resolvability (e.g., when provided via
	IGP Flexible Algorithm) can be ignored if the ingress PE has a local		IGP Flexible Algorithm) can be ignored if the ingress PE has a local
	policy that allows an alternate steering mechanism to reach the		policy that allows an alternate steering mechanism to reach the
	egress PE. The details of such steering mechanisms are outside the		egress PE. The details of such steering mechanisms are outside the
	scope of this document.		scope of this document.
	For service over SRv6 core, the egress PE sets the next hop to one of		For service over SRv6 core, the egress PE sets the BGP next hop to
	its IPv6 addresses. Such an address MAY be covered by the SRv6		one of its IPv6 addresses. Such an address MAY be covered by the
	Locator from which the SRv6 Service SID is allocated. The next hop		SRv6 Locator from which the SRv6 Service SID is allocated. The BGP
	is used for tracking the reachability of the egress PE based on		next hop is used for tracking the reachability of the egress PE based
	existing BGP procedures.		on existing BGP procedures.
	When the BGP route received at an ingress PE is colored with a Color		When the BGP route received at an ingress PE is colored with a Color
	Extended Community and a valid SRv6 Policy is available, the steering		Extended Community and a valid SRv6 Policy is available, the steering
	for service flows is performed as described in Section 8 of		for service flows is performed as described in Section 8 of
	[SEGMENT-ROUTING-POLICY]. When the ingress PE determines (with the		[SEGMENT-ROUTING-POLICY]. When the ingress PE determines (with the
	help of the SRv6 SID Structure) that the Service SID belongs to the		help of the SRv6 SID Structure) that the Service SID belongs to the
	same SRv6 Locator as the last SRv6 SID (of the egress PE) in the SR		same SRv6 Locator as the last SRv6 SID (of the egress PE) in the SR
	Policy segment list, it MAY exclude that last SRv6 SID when steering		Policy segment list, it MAY exclude that last SRv6 SID when steering
	the service flow. For example, the effective segment list of the		the service flow. For example, the effective segment list of the
	SRv6 Policy associated with SID list <S1, S2, S3> would be <S1, S2,		SRv6 Policy associated with SID list <S1, S2, S3> would be <S1, S2,
	skipping to change at line 749 ¶		skipping to change at line 749 ¶
	Figure 6: EVPN Route Type 1		Figure 6: EVPN Route Type 1
	6.1.1. Ethernet A-D per ES Route		6.1.1. Ethernet A-D per ES Route
	Ethernet A-D per ES route NLRI encoding over SRv6 core is as per		Ethernet A-D per ES route NLRI encoding over SRv6 core is as per
	[RFC7432].		[RFC7432].
	The 24-bit ESI Label field of the ESI Label extended community		The 24-bit ESI Label field of the ESI Label extended community
	carries the whole or a portion of the Argument part of the SRv6 SID		carries the whole or a portion of the Argument part of the SRv6 SID
	when the ESI filtering approach is used along with the Transposition		when the ESI filtering approach is used along with the Transposition
	Scheme of encoding (Section 4); otherwise, it is set to the Implicit		Scheme of encoding (Section 4); otherwise, it is set to Implicit NULL
	NULL value. In either case, the value is set in the 24 bits (e.g.,		in the higher-order 20 bits (i.e., as 0x000030). In either case, the
	as 0x000030 in the case of Implicit NULL). When using the		value is set in the 24 bits. When using the Transposition Scheme,
	Transposition Scheme, the Transposition Length MUST be less than or		the Transposition Length MUST be less than or equal to 24 and less
	equal to 24 and less than or equal to the AL.		than or equal to the AL.
	A Service SID enclosed in an SRv6 L2 Service TLV within the BGP		A Service SID enclosed in an SRv6 L2 Service TLV within the BGP
	Prefix-SID attribute is advertised along with the A-D route. The		Prefix-SID attribute is advertised along with the A-D route. The
	SRv6 Endpoint Behavior SHOULD be End.DT2M. When the ESI filtering		SRv6 Endpoint Behavior SHOULD be End.DT2M. When the ESI filtering
	approach is used, the Service SID is used to signal the Arg.FE2 SID		approach is used, the Service SID is used to signal the Arg.FE2 SID
	Argument for applicable End.DT2M behavior [RFC8986]. When the local-		Argument for applicable End.DT2M behavior [RFC8986]. When the local-
	bias approach [RFC8365] is used, the Service SID MAY be of value 0.		bias approach [RFC8365] is used, the Service SID MAY be of value 0.
	6.1.2. Ethernet A-D per EVI Route		6.1.2. Ethernet A-D per EVI Route
	Ethernet A-D per EVPN Instance (EVI) route NLRI encoding over SRv6		Ethernet A-D per EVPN Instance (EVI) route NLRI encoding over SRv6
	core is similar to what is described in [RFC7432] and [RFC8214] with		core is similar to what is described in [RFC7432] and [RFC8214] with
	the following change:		the following change:
	MPLS Label:		MPLS Label:
	The 24-bit field carries the whole or a portion of the Function		The 24-bit field carries the whole or a portion of the Function
	part of the SRv6 SID when the Transposition Scheme of encoding		part of the SRv6 SID when the Transposition Scheme of encoding
	(Section 4) is used; otherwise, it is set to the Implicit NULL		(Section 4) is used; otherwise, it is set to Implicit NULL in the
	value. In either case, the value is set in the 24 bits (e.g., as		higher-order 20 bits (i.e., as 0x000030). In either case, the
	0x000030 in the case of Implicit NULL). When using the		value is set in the 24 bits. When using the Transposition Scheme,
	Transposition Scheme, the Transposition Length MUST be less than		the Transposition Length MUST be less than or equal to 24 and less
	or equal to 24 and less than or equal to the FL.		than or equal to the FL.
	A Service SID enclosed in an SRv6 L2 Service TLV within the BGP		A Service SID enclosed in an SRv6 L2 Service TLV within the BGP
	Prefix-SID attribute is advertised along with the A-D route. The		Prefix-SID attribute is advertised along with the A-D route. The
	SRv6 Endpoint Behavior SHOULD be one of these: End.DX2, End.DX2V, or		SRv6 Endpoint Behavior SHOULD be one of these: End.DX2, End.DX2V, or
	End.DT2U.		End.DT2U.
	6.2. MAC/IP Advertisement Route over SRv6 Core		6.2. MAC/IP Advertisement Route over SRv6 Core
	EVPN Route Type 2 is used to advertise unicast traffic Media Access		EVPN Route Type 2 is used to advertise unicast traffic Media Access
	Control (MAC) + IP address reachability through MP-BGP to all other		Control (MAC) + IP address reachability through MP-BGP to all other
	skipping to change at line 819 ¶		skipping to change at line 819 ¶
	Figure 7: EVPN Route Type 2		Figure 7: EVPN Route Type 2
	NLRI encoding over SRv6 core is similar to what is described in		NLRI encoding over SRv6 core is similar to what is described in
	[RFC7432] with the following changes:		[RFC7432] with the following changes:
	MPLS Label1:		MPLS Label1:
	This is associated with the SRv6 L2 Service TLV. This 24-bit		This is associated with the SRv6 L2 Service TLV. This 24-bit
	field carries the whole or a portion of the Function part of the		field carries the whole or a portion of the Function part of the
	SRv6 SID when the Transposition Scheme of encoding (Section 4) is		SRv6 SID when the Transposition Scheme of encoding (Section 4) is
	used; otherwise, it is set to the Implicit NULL value. In either		used; otherwise, it is set to Implicit NULL in the higher-order 20
	case, the value is set in the 24 bits (e.g., as 0x000030 in the		bits (i.e., as 0x000030). In either case, the value is set in the
	case of Implicit NULL). When using the Transposition Scheme, the		24 bits. When using the Transposition Scheme, the Transposition
	Transposition Length MUST be less than or equal to 24 and less		Length MUST be less than or equal to 24 and less than or equal to
	than or equal to the FL.		the FL.
	MPLS Label2:		MPLS Label2:
	This is associated with the SRv6 L3 Service TLV. This 24-bit		This is associated with the SRv6 L3 Service TLV. This 24-bit
	field carries the whole or a portion of the Function part of the		field carries the whole or a portion of the Function part of the
	SRv6 SID when the Transposition Scheme of encoding (Section 4) is		SRv6 SID when the Transposition Scheme of encoding (Section 4) is
	used; otherwise, it is set to the Implicit NULL value. In either		used; otherwise, it is set to Implicit NULL in the higher-order 20
	case, the value is set in the 24 bits (e.g., as 0x000030 in the		bits (i.e., as 0x000030). In either case, the value is set in the
	case of Implicit NULL). When using the Transposition Scheme, the		24 bits. When using the Transposition Scheme, the Transposition
	Transposition Length MUST be less than or equal to 24 and less		Length MUST be less than or equal to 24 and less than or equal to
	than or equal to the FL.		the FL.
	Service SIDs enclosed in the SRv6 L2 Service TLV and optionally in		Service SIDs enclosed in the SRv6 L2 Service TLV and optionally in
	the SRv6 L3 Service TLV within the BGP Prefix-SID attribute are		the SRv6 L3 Service TLV within the BGP Prefix-SID attribute are
	advertised along with the MAC/IP Advertisement route.		advertised along with the MAC/IP Advertisement route.
	Described below are different types of Route Type 2 advertisements.		Described below are different types of Route Type 2 advertisements.
	6.2.1. MAC/IP Advertisement Route with MAC Only		6.2.1. MAC/IP Advertisement Route with MAC Only
	MPLS Label1:		MPLS Label1:
	This is associated with the SRv6 L2 Service TLV. This 24-bit		This is associated with the SRv6 L2 Service TLV. This 24-bit
	field carries the whole or a portion of the Function part of the		field carries the whole or a portion of the Function part of the
	SRv6 SID when the Transposition Scheme of encoding (Section 4) is		SRv6 SID when the Transposition Scheme of encoding (Section 4) is
	used; otherwise, it is set to the Implicit NULL value. In either		used; otherwise, it is set to Implicit NULL in the higher-order 20
	case, the value is set in the 24 bits (e.g., as 0x000030 in the		bits (i.e., as 0x000030). In either case, the value is set in the
	case of Implicit NULL). When using the Transposition Scheme, the		24 bits. When using the Transposition Scheme, the Transposition
	Transposition Length MUST be less than or equal to 24 and less		Length MUST be less than or equal to 24 and less than or equal to
	than or equal to the FL.		the FL.
	A Service SID enclosed in an SRv6 L2 Service TLV within the BGP		A Service SID enclosed in an SRv6 L2 Service TLV within the BGP
	Prefix-SID attribute is advertised along with the route. The SRv6		Prefix-SID attribute is advertised along with the route. The SRv6
	Endpoint Behavior SHOULD be one of these: End.DX2 or End.DT2U.		Endpoint Behavior SHOULD be one of these: End.DX2 or End.DT2U.
	6.2.2. MAC/IP Advertisement Route with MAC+IP		6.2.2. MAC/IP Advertisement Route with MAC+IP
	MPLS Label1:		MPLS Label1:
	This is associated with the SRv6 L2 Service TLV. This 24-bit		This is associated with the SRv6 L2 Service TLV. This 24-bit
	field carries the whole or a portion of the Function part of the		field carries the whole or a portion of the Function part of the
	SRv6 SID when the Transposition Scheme of encoding (Section 4) is		SRv6 SID when the Transposition Scheme of encoding (Section 4) is
	used; otherwise, it is set to the Implicit NULL value. In either		used; otherwise, it is set to Implicit NULL in the higher-order 20
	case, the value is set in the 24 bits (e.g., as 0x000030 in the		bits (i.e., as 0x000030). In either case, the value is set in the
	case of Implicit NULL). When using the Transposition Scheme, the		24 bits. When using the Transposition Scheme, the Transposition
	Transposition Length MUST be less than or equal to 24 and less		Length MUST be less than or equal to 24 and less than or equal to
	than or equal to the FL.		the FL.
	MPLS Label2:		MPLS Label2:
	This is associated with the SRv6 L3 Service TLV. This 24-bit		This is associated with the SRv6 L3 Service TLV. This 24-bit
	field carries the whole or a portion of the Function part of the		field carries the whole or a portion of the Function part of the
	SRv6 SID when the Transposition Scheme of encoding (Section 4) is		SRv6 SID when the Transposition Scheme of encoding (Section 4) is
	used; otherwise, it is set to the Implicit NULL value. In either		used; otherwise, it is set to Implicit NULL in the higher-order 20
	case, the value is set in the 24 bits (e.g., as 0x000030 in the		bits (i.e., as 0x000030). In either case, the value is set in the
	case of Implicit NULL). When using the Transposition Scheme, the		24 bits. When using the Transposition Scheme, the Transposition
	Transposition Length MUST be less than or equal to 24 and less		Length MUST be less than or equal to 24 and less than or equal to
	than or equal to the FL.		the FL.
	An L2 Service SID enclosed in an SRv6 L2 Service TLV within the BGP		An L2 Service SID enclosed in an SRv6 L2 Service TLV within the BGP
	Prefix-SID attribute is advertised along with the route. In		Prefix-SID attribute is advertised along with the route. In
	addition, an L3 Service SID enclosed in an SRv6 L3 Service TLV within		addition, an L3 Service SID enclosed in an SRv6 L3 Service TLV within
	the BGP Prefix-SID attribute MAY also be advertised along with the		the BGP Prefix-SID attribute MAY also be advertised along with the
	route. The SRv6 Endpoint Behavior SHOULD be one of these: for the L2		route. The SRv6 Endpoint Behavior SHOULD be one of these: for the L2
	Service SID, End.DX2 or End.DT2U and for the L3 Service SID,		Service SID, End.DX2 or End.DT2U and for the L3 Service SID,
	End.DT46, End.DT4, End.DT6, End.DX4, or End.DX6.		End.DT46, End.DT4, End.DT6, End.DX4, or End.DX6.
	6.3. Inclusive Multicast Ethernet Tag Route over SRv6 Core		6.3. Inclusive Multicast Ethernet Tag Route over SRv6 Core
	skipping to change at line 1024 ¶		skipping to change at line 1024 ¶
	+-----------------------------------------+		+-----------------------------------------+
	Figure 11: EVPN Route Type 5		Figure 11: EVPN Route Type 5
	NLRI encoding over SRv6 core is similar to what is described in		NLRI encoding over SRv6 core is similar to what is described in
	[RFC9136] with the following change:		[RFC9136] with the following change:
	MPLS Label:		MPLS Label:
	This 24-bit field carries the whole or a portion of the Function		This 24-bit field carries the whole or a portion of the Function
	part of the SRv6 SID when the Transposition Scheme of encoding		part of the SRv6 SID when the Transposition Scheme of encoding
	(Section 4) is used; otherwise, it is set to the Implicit NULL		(Section 4) is used; otherwise, it is set to Implicit NULL in the
	value. In either case, the value is set in the 24 bits (e.g., as		higher-order 20 bits (i.e., as 0x000030). In either case, the
	0x000030 in the case of Implicit NULL). When using the		value is set in the 24 bits. When using the Transposition Scheme,
	Transposition Scheme, the Transposition Length MUST be less than		the Transposition Length MUST be less than or equal to 24 and less
	or equal to 24 and less than or equal to the FL.		than or equal to the FL.
	The SRv6 Service SID is encoded as part of the SRv6 L3 Service TLV.		The SRv6 Service SID is encoded as part of the SRv6 L3 Service TLV.
	The SRv6 Endpoint Behavior SHOULD be one of these: End.DT4, End.DT6,		The SRv6 Endpoint Behavior SHOULD be one of these: End.DT4, End.DT6,
	End.DT46, End.DX4, or End.DX6.		End.DT46, End.DX4, or End.DX6.
	6.6. EVPN Multicast Routes (Route Types 6, 7, and 8) over SRv6 Core		6.6. EVPN Multicast Routes (Route Types 6, 7, and 8) over SRv6 Core
	These routes do not require the advertisement of SRv6 Service TLVs		These routes do not require the advertisement of SRv6 Service TLVs
	along with them. Similar to EVPN Route Type 4, the BGP next hop is		along with them. Similar to EVPN Route Type 4, the BGP next hop is
	equal to the IPv6 address of egress PE.		equal to the IPv6 address of egress PE.
	skipping to change at line 1139 ¶		skipping to change at line 1139 ¶
	replaced by the SRv6 L3 Service and SRv6 L2 Service TLVs.		replaced by the SRv6 L3 Service and SRv6 L2 Service TLVs.
	8.2. SRv6 Service Sub-TLV Types Registry		8.2. SRv6 Service Sub-TLV Types Registry
	IANA has created and now maintains a new subregistry called "SRv6		IANA has created and now maintains a new subregistry called "SRv6
	Service Sub-TLV Types" under the "Border Gateway Protocol (BGP)		Service Sub-TLV Types" under the "Border Gateway Protocol (BGP)
	Parameters" registry. The registration procedures, per [RFC8126],		Parameters" registry. The registration procedures, per [RFC8126],
	for this subregistry are according to Table 2.		for this subregistry are according to Table 2.
	+=========+=========================+		+=========+=========================+
	| Range | Registration Procedure |		| Range | Registration Procedures |
	+=========+=========================+		+=========+=========================+
	| 1-127 | IETF Review |		| 1-127 | IETF Review |
	+---------+-------------------------+		+---------+-------------------------+
	| 128-254 | First Come First Served |		| 128-254 | First Come First Served |
	+---------+-------------------------+		+---------+-------------------------+
	| 255 | IETF Review |		| 255 | IETF Review |
	+---------+-------------------------+		+---------+-------------------------+
	Table 2: SRv6 Service Sub-TLV		Table 2: SRv6 Service Sub-TLV
	Types Subregistry Registration		Types Subregistry Registration
	skipping to change at line 1435 ¶		skipping to change at line 1435 ¶
	<https://www.rfc-editor.org/info/rfc8986>.		<https://www.rfc-editor.org/info/rfc8986>.
	[RFC9136] Rabadan, J., Ed., Henderickx, W., Drake, J., Lin, W., and		[RFC9136] Rabadan, J., Ed., Henderickx, W., Drake, J., Lin, W., and
	A. Sajassi, "IP Prefix Advertisement in Ethernet VPN		A. Sajassi, "IP Prefix Advertisement in Ethernet VPN
	(EVPN)", RFC 9136, DOI 10.17487/RFC9136, October 2021,		(EVPN)", RFC 9136, DOI 10.17487/RFC9136, October 2021,
	<https://www.rfc-editor.org/info/rfc9136>.		<https://www.rfc-editor.org/info/rfc9136>.
	[RFC9251] Sajassi, A., Thoria, S., Mishra, M., Patel, K., Drake, J.,		[RFC9251] Sajassi, A., Thoria, S., Mishra, M., Patel, K., Drake, J.,
	and W. Lin, "Internet Group Management Protocol (IGMP) and		and W. Lin, "Internet Group Management Protocol (IGMP) and
	Multicast Listener Discovery (MLD) Proxies for Ethernet		Multicast Listener Discovery (MLD) Proxies for Ethernet
	VPN (EVPN)", RFC RFC9251, DOI 10.17487/RFC9251, June 2022,		VPN (EVPN)", RFC 9251, DOI 10.17487/RFC9251, June 2022,
	<https://www.rfc-editor.org/info/rfc9251>.		<https://www.rfc-editor.org/info/rfc9251>.
	10.2. Informative References		10.2. Informative References
	[BGP-SR-POLICY]
	Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
	P., Jain, D., and S. Lin, "Advertising Segment Routing
	Policies in BGP", Work in Progress, Internet-Draft, draft-
	ietf-idr-segment-routing-te-policy-17, 14 April 2022,
	<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
	segment-routing-te-policy-17>.
	[IGP-FLEX-ALGO]		[IGP-FLEX-ALGO]
	Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,		Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
	and A. Gulko, "IGP Flexible Algorithm", Work in Progress,		and A. Gulko, "IGP Flexible Algorithm", Work in Progress,
	Internet-Draft, draft-ietf-lsr-flex-algo-20, 18 May 2022,		Internet-Draft, draft-ietf-lsr-flex-algo-20, 18 May 2022,
	<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-		<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
	flex-algo-20>.		flex-algo-20>.
	[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:		[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
	Defeating Denial of Service Attacks which employ IP Source		Defeating Denial of Service Attacks which employ IP Source
	Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,		Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
End of changes. 28 change blocks.
	95 lines changed or deleted		87 lines changed or added
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