draft-xu-mpls-sr-over-ip-00.txt		draft-xu-mpls-sr-over-ip-01.txt
	Network Working Group X. Xu		Network Working Group X. Xu
	Internet-Draft Alibaba		Internet-Draft Alibaba
	Intended status: Standards Track S. Bryant		Intended status: Standards Track S. Bryant
	Expires: September 2, 2018 Huawei		Expires: December 3, 2018 Huawei
	A. Farrel		A. Farrel
	Juniper		Juniper
	A. Bashandy		S. Hassan
	Cisco		Cisco
	W. Henderickx		W. Henderickx
	Nokia		Nokia
	Z. Li		Z. Li
	Huawei		Huawei
	March 1, 2018		June 1, 2018
	SR-MPLS over IP		SR-MPLS over IP
	draft-xu-mpls-sr-over-ip-00		draft-xu-mpls-sr-over-ip-01
	Abstract		Abstract
	MPLS Segment Routing (SR-MPLS in short) is an MPLS data plane-based		MPLS Segment Routing (SR-MPLS in short) is an MPLS data plane-based
	source routing paradigm in which the sender of a packet is allowed to		source routing paradigm in which the sender of a packet is allowed to
	partially or completely specify the route the packet takes through		partially or completely specify the route the packet takes through
	the network by imposing stacked MPLS labels on the packet. SR-MPLS		the network by imposing stacked MPLS labels on the packet. SR-MPLS
	could be leveraged to realize a source routing mechanism across MPLS,		could be leveraged to realize a source routing mechanism across MPLS,
	IPv4, and IPv6 data planes by using an MPLS label stack as a source		IPv4, and IPv6 data planes by using an MPLS label stack as a source
	routing instruction set while preserving backward compatibility with		routing instruction set while preserving backward compatibility with
	SR-MPLS.		SR-MPLS.
	This document describes how SR-MPLS capable routers and IP-only		This document describes how SR-MPLS capable routers and IP-only
	routers can seamlessly co-exist and interoperate through the use of		routers can seamlessly co-exist and interoperate through the use of
	SR-MPLS label stacks and IP encapsulation/tunnelling such as MPLS-in-		SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-in-
	UDP [RFC7510].		UDP as defined in RFC 7510.
	Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 December 3, 2018.
	This Internet-Draft will expire on September 2, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 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 . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Procedures of SR-MPLS over IP . . . . . . . . . . . . . . . . 5		4. Procedures of SR-MPLS over IP . . . . . . . . . . . . . . . . 5
	4.1. Forwarding Entry Construction . . . . . . . . . . . . . . 5		4.1. Forwarding Entry Construction . . . . . . . . . . . . . . 5
	4.2. Packet Forwarding Procedures . . . . . . . . . . . . . . 7		4.2. Packet Forwarding Procedures . . . . . . . . . . . . . . 7
	4.2.1. Packet Forwarding with Penultimate Hop Popping . . . 7		4.2.1. Packet Forwarding with Penultimate Hop Popping . . . 8
	4.2.2. Packet Forwarding without Penultimate Hop Popping . . 8		4.2.2. Packet Forwarding without Penultimate Hop Popping . . 9
	4.2.3. Additional Forwarding Procedures . . . . . . . . . . 9		4.2.3. Additional Forwarding Procedures . . . . . . . . . . 10
	5. Forwarding Details of SR-MPLS over UDP . . . . . . . . . . . 10		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	5.1. Domain Ingress Nodes . . . . . . . . . . . . . . . . . . 11		6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	5.2. Legacy Transit Nodes . . . . . . . . . . . . . . . . . . 11		7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
	5.3. On-Path Pass-Through SR Nodes . . . . . . . . . . . . . . 12		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
	5.4. SR Transit Nodes . . . . . . . . . . . . . . . . . . . . 12		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
	5.5. Penultimate SR Transit Nodes . . . . . . . . . . . . . . 13		9.1. Normative References . . . . . . . . . . . . . . . . . . 13
	5.5.1. A Note on Segment Routing Paths and Penultimate Hop		9.2. Informative References . . . . . . . . . . . . . . . . . 15
	Popping . . . . . . . . . . . . . . . . . . . . . . . 14		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
	5.6. Domain Egress Nodes . . . . . . . . . . . . . . . . . . . 14
	6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 17
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
	10.1. Normative References . . . . . . . . . . . . . . . . . . 17
	10.2. Informative References . . . . . . . . . . . . . . . . . 18
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
	1. Introduction		1. Introduction
	MPLS Segment Routing (SR-MPLS in short)		MPLS Segment Routing (SR-MPLS in short)
	[I-D.ietf-spring-segment-routing-mpls] is an MPLS data plane-based		[I-D.ietf-spring-segment-routing-mpls] is an MPLS data plane-based
	source routing paradigm in which the sender of a packet is allowed to		source routing paradigm in which the sender of a packet is allowed to
	partially or completely specify the route the packet takes through		partially or completely specify the route the packet takes through
	the network by imposing stacked MPLS labels on the packet. SR-MPLS		the network by imposing stacked MPLS labels on the packet. SR-MPLS
	could be leveraged to realize a source routing mechanism across MPLS,		could be leveraged to realize a source routing mechanism across MPLS,
	IPv4, and IPv6 data planes by using an MPLS label stack as a source		IPv4, and IPv6 data planes by using an MPLS label stack as a source
	routing instruction set while preserving backward compatibility with		routing instruction set while preserving backward compatibility with
	SR-MPLS. More specifically, the source routing instruction set		SR-MPLS. More specifically, the source routing instruction set
	information contained in a source routed packet could be uniformly		information contained in a source routed packet could be uniformly
	encoded as an MPLS label stack no matter whether the underlay is		encoded as an MPLS label stack no matter whether the underlay is
	IPv4, IPv6, or MPLS.		IPv4, IPv6, or MPLS.
	This document describes how SR-MPLS capable routers and IP-only		This document describes how SR-MPLS capable routers and IP-only
	routers can seamlessly co-exist and interoperate through the use of		routers can seamlessly co-exist and interoperate through the use of
	SR-MPLS label stacks and IP encapsulation/tunnelling such as MPLS-in-		SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-in-
	UDP [RFC7510].		UDP [RFC7510].
	Although the source routing instructions are encoded as MPLS labels,		Although the source routing instructions are encoded as MPLS labels,
	this is a hardware convenience rather than an indication that the		this is a hardware convenience rather than an indication that the
	whole MPLS protocol stack needs to be deployed. In particular, the		whole MPLS protocol stack needs to be deployed. In particular, the
	MPLS control protocols are not used in this or any other form of SR-		MPLS control protocols are not used in this or any other form of SR-
	MPLS.		MPLS.
	Section 3 describes various use cases for the tunneling SR-MPLS over		Section 3 describes various use cases for the tunneling SR-MPLS over
	IP. Section 4 describes a typical application scenario and how the		IP. Section 4 describes a typical application scenario and how the
	packet forwarding happens. Section 5 describes the forwarding		packet forwarding happens.
	procedures of different elements when UDP encapsulation is adopted
	for source routing.
	2. Terminology		2. Terminology
	This memo makes use of the terms defined in [RFC3031] and		This memo makes use of the terms defined in [RFC3031] and
	[I-D.ietf-spring-segment-routing-mpls].		[I-D.ietf-spring-segment-routing-mpls].
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
			"OPTIONAL" in this document are to be interpreted as described in BCP
			14 [RFC2119] [RFC8174] when, and only when, they appear in all
			capitals, as shown here.
	3. Use Cases		3. Use Cases
	Tunnelling SR-MPLS using IPv4 and/or IPv6 tunnels is useful at least		Tunneling SR-MPLS using IPv4 and/or IPv6 tunnels is useful at least
	in the following use cases:		in the following use cases:
	o Incremental deployment of the SR-MPLS technology may be		o Incremental deployment of the SR-MPLS technology may be
	facilitated by tunnelling SR-MPLS packets across parts of a		facilitated by tunneling SR-MPLS packets across parts of a network
	network that are not SR-MPLS enabled using an IP tunneling		that are not SR-MPLS enabled using an IP tunneling mechanism such
	mechanism such as MPLS-in-UDP [RFC7510]. The tunnel destination		as MPLS-in-UDP [RFC7510]. The tunnel destination address is the
	address is the address of the next SR-MPLS-capable node along the		address of the next SR-MPLS-capable node along the path (i.e., the
	path (i.e., the egress of the active node segment). This is shown		egress of the active node segment). This is shown in Figure 1.
	in Figure 1.
	________________________		________________________
	_______ ( ) _______		_______ ( ) _______
	( ) ( IP Network ) ( )		( ) ( IP Network ) ( )
	( SR-MPLS ) ( ) ( SR-MPLS )		( SR-MPLS ) ( ) ( SR-MPLS )
	( Network ) ( ) ( Network )		( Network ) ( ) ( Network )
	( -------- -------- )		( -------- -------- )
	( | Border | SR-in-UDP Tunnel | Border | )		( | Border | SR-in-UDP Tunnel | Border | )
	( | Router |========================| Router | )		( | Router |========================| Router | )
	( | R1 | | R2 | )		( | R1 | | R2 | )
	( -------- -------- )		( -------- -------- )
	( ) ( ) ( )		( ) ( ) ( )
	( ) ( ) ( )		( ) ( ) ( )
	(_______) ( ) (_______)		(_______) ( ) (_______)
	(________________________)		(________________________)
	Figure 1: SR-MPLS in UDP to Tunnel Between SR-MPLS Sites		Figure 1: SR-MPLS in UDP to Tunnel Between SR-MPLS Sites
	o If encoding of entropy is desired, IP tunneling mechanims that		o If encoding of entropy is desired, IP tunneling mechanisms that
	allow encoding of entrpopy, such as MPLS-in-UDP encapsulation		allow encoding of entropy, such as MPLS-in-UDP encapsulation
	[RFC7510] where the source port of the UDP header is used as an		[RFC7510] where the source port of the UDP header is used as an
	entropy field, may be used to maximize the untilization of ECMP		entropy field, may be used to maximize the utilization of ECMP
	and/or UCMP, specially when it is difficult to make use of entropy		and/or UCMP, specially when it is difficult to make use of entropy
	label mechanism. Refer to [I-D.ietf-mpls-spring-entropy-label])		label mechanism. Refer to [I-D.ietf-mpls-spring-entropy-label])
	for more discussion about using entropy label in SR-MPLS.		for more discussion about using entropy label in SR-MPLS.
	o Tunneling MPLS into IP provides a transition technology that		o Tunneling MPLS into IP provides a technology that enables SR in an
	enables SR in an IPv4 and/or IPv6 network where many routers have		IPv4 and/or IPv6 network where the routers do not support SRv6
	not yet been upgraded to have SRv6 capabilities		capabilities [I-D.ietf-6man-segment-routing-header] and where MPLS
	[I-D.ietf-6man-segment-routing-header]. It could be deployed as		forwarding is not an option. This is shown in Figure Figure 2.
	an interim until full featured SRv6 is available on more
	platforms. This is shown in Figure 2.
	__________________________________		__________________________________
	__( IP Network )__		__( IP Network )__
	__( )__		__( )__
	( -- -- -- )		( -- -- -- )
	-------- -- -- |SR| -- |SR| -- |SR| -- --------		-------- -- -- |SR| -- |SR| -- |SR| -- --------
	| Ingress| |IR| |IR| | | |IR| | | |IR| | | |IR| | Egress |		| Ingress| |IR| |IR| | | |IR| | | |IR| | | |IR| | Egress |
	--->| Router |===========| |======| |======| |======| Router |--->		--->| Router |===========| |======| |======| |======| Router |--->
	| SR | | | | | | | | | | | | | | | | | | SR |		| SR | | | | | | | | | | | | | | | | | | SR |
	-------- -- -- | | -- | | -- | | -- --------		-------- -- -- | | -- | | -- | | -- --------
	skipping to change at page 5, line 46 ¶		skipping to change at page 5, line 46 ¶
	4.1. Forwarding Entry Construction		4.1. Forwarding Entry Construction
	This sub-section describes the how to construct the forwarding		This sub-section describes the how to construct the forwarding
	information base (FIB) entry on an SR-MPLS-capable router when some		information base (FIB) entry on an SR-MPLS-capable router when some
	or all of the next-hops along the shortest path towards a prefix-SID		or all of the next-hops along the shortest path towards a prefix-SID
	are IP-only routers.		are IP-only routers.
	Consider router A that receives a labeled packet with top label L(E)		Consider router A that receives a labeled packet with top label L(E)
	that corresponds to the prefix-SID SID(E) of prefix P(E) advertised		that corresponds to the prefix-SID SID(E) of prefix P(E) advertised
	by router E. Suppose the ith next-hop router (termed NHi) along the		by router E. Suppose the ith next-hop router (termed NHi) along the
	shortest path from router A toward SID(E) is not SR-MPLS capable.		shortest path from router A toward SID(E) is not SR-MPLS capable
	That is both routers A and E are SR-MPLS capable, but some router NHi		while both routers A and E are SR-MPLS capable. The following
	along the shortest path from A to E is not SR-MPLS capable. The		processing steps apply:
	following processing steps apply:
	o Router E is SR-MPLS capable so it advertises the SR-Capabilities		o Router E is SR-MPLS capable so it advertises the SR-Capabilities
	sub-TLV including the SRGB as described in		sub-TLV including the SRGB as described in
	[I-D.ietf-ospf-segment-routing-extensions] and		[I-D.ietf-ospf-segment-routing-extensions] and
	[I-D.ietf-isis-segment-routing-extensions].		[I-D.ietf-isis-segment-routing-extensions].
	o Router E advertises the prefix-SID SID(E) of prefix P(E) so MUST		o Router E advertises the prefix-SID SID(E) of prefix P(E) so MUST
	also advertise the encapsulation endpoint and the tunnel type of		also advertise the encapsulation endpoint and the tunnel type of
	any tunnel used to reach E. It does this using the mechanisms		any tunnel used to reach E. It does this using the mechanisms
	described in [I-D.ietf-isis-encapsulation-cap] or		described in [I-D.ietf-isis-encapsulation-cap] or
	skipping to change at page 7, line 18 ¶		skipping to change at page 7, line 18 ¶
	bound of the SRGB of E		bound of the SRGB of E
	* Encapsulate the packet according to the encapsulation		* Encapsulate the packet according to the encapsulation
	advertised in [I-D.ietf-isis-encapsulation-cap] or		advertised in [I-D.ietf-isis-encapsulation-cap] or
	[I-D.ietf-ospf-encapsulation-cap]		[I-D.ietf-ospf-encapsulation-cap]
	* Send the packet towards the next hop NHi.		* Send the packet towards the next hop NHi.
	4.2. Packet Forwarding Procedures		4.2. Packet Forwarding Procedures
			[RFC7510] specifies an IP-based encapsulation for MPLS, i.e., MPLS-
			in-UDP, which is applicable in some circumstances where IP-based
			encapsulation for MPLS is required and further fine-grained load
			balancing of MPLS packets over IP networks over Equal-Cost Multipath
			(ECMP) and/or Link Aggregation Groups (LAGs) is required as well.
			This section provides details about the forwarding procedure when
			when UDP encapsulation is adopted for SR-MPLS over IP.
			Nodes that are SR-MPLS capable can process SR-MPLS packets. Not all
			of the nodes in an SR-MPLS domain are SR-MPLS capable. Some nodes
			may be "legacy routers" that cannot handle SR-MPLS packets but can
			forward IP packets. An SR-MPLS-capable node may advertise its
			capabilities using the IGP as described in Section 4. There are six
			types of node in an SR-MPLS domain:
			o Domain ingress nodes that receive packets and encapsulate them for
			transmission across the domain. Those packets may be any payload
			protocol including native IP packets or packets that are already
			MPLS encapsulated.
			o Legacy transit nodes that are IP routers but that are not SR-MPLS
			capable (i.e., are not able to perform segment routing).
			o Transit nodes that are SR-MPLS capable but that are not identified
			by a SID in the SID stack.
			o Transit nodes that are SR-MPLS capable and need to perform SR-MPLS
			routing because they are identified by a SID in the SID stack.
			o The penultimate SR-MPLS capable node on the path that processes
			the last SID on the stack on behalf of the domain egress node.
			o The domain egress node that forwards the payload packet for
			ultimate delivery.
	4.2.1. Packet Forwarding with Penultimate Hop Popping		4.2.1. Packet Forwarding with Penultimate Hop Popping
	The description in this section assumes that the label associated		The description in this section assumes that the label associated
	with each prefix-SID is advertised by the owner of the prefix-SID is		with each prefix-SID is advertised by the owner of the prefix-SID is
	a Penultimate Hop Popping (PHP) label. That is, the NP flag in OSPF		a Penultimate Hop Popping (PHP) label. That is, the NP flag in OSPF
	or the P flag in ISIS associated with the prefix SID is not set.		or the P flag in ISIS associated with the prefix SID is not set.
	+-----+ +-----+ +-----+ +-----+ +-----+		+-----+ +-----+ +-----+ +-----+ +-----+
	| A +-------+ B +-------+ C +--------+ D +--------+ H |		| A +-------+ B +-------+ C +--------+ D +--------+ H |
	+-----+ +--+--+ +--+--+ +--+--+ +-----+		+-----+ +--+--+ +--+--+ +--+--+ +-----+
	skipping to change at page 7, line 48 ¶		skipping to change at page 8, line 35 ¶
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	| L(G) | | UDP | | UDP |		| L(G) | | UDP | | UDP |
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	| L(H) | | L(H) | |Exp Null|		| L(H) | | L(H) | |Exp Null|
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	| Packet | ---> | Packet | ---> | Packet |		| Packet | ---> | Packet | ---> | Packet |
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	Figure 3: Packet Forwarding Example with PHP		Figure 3: Packet Forwarding Example with PHP
	In the example shown in Figure 3, assume that routers A, E, G, and H		In the example shown in Figure 3, assume that routers A, E, G and H
	are SR-MPLS-capable while the remaining routers (B, C, D, and F) are		are SR-MPLS-capable while the remaining routers (B, C, D and F) are
	only capable of forwarding IP packets. Routers A, E, G, and H		only capable of forwarding IP packets. Routers A, E, G, and H
	advertise their Segment Routing related information via IS-IS or		advertise their Segment Routing related information via IS-IS or
	OSPF.		OSPF.
	Now assume that router A wants to send a packet via the explicit path		Now assume that router A (the Domain ingress) wants to send a packet
	{E->G->H}. Router A will impose an MPLS label stack corresponding to		to router H (the Domain egress) via the explicit path {E->G->H}.
	that explicit path on the packet. Since the next hop toward router E		Router A will impose an MPLS label stack on the packet that
	is only IP-capable, router A replaces the top label (that indicated		corresponds to that explicit path. Since the next hop toward router
	router E) with a UDP-based tunnel for MPLS (i.e., MPLS-over-UDP		E is only IP-capable (B is a legacy transit node), router A replaces
	[RFC7510]) to router E and then sends the packet. In other words,		the top label (that indicated router E) with a UDP-based tunnel for
	router A pops the top label and then encapsulates the MPLS packet in		MPLS (i.e., MPLS-over-UDP [RFC7510]) to router E and then sends the
	a UDP tunnel to router E.		packet. In other words, router A pops the top label and then
			encapsulates the MPLS packet in a UDP tunnel to router E.
	When the IP-encapsulated MPLS packet arrives at router E, router E		When the IP-encapsulated MPLS packet arrives at router E (which is an
	strips the IP-based tunnel header and then process the decapsulated		SR-MPLS-capable transit node), router E strips the IP-based tunnel
	MPLS packet. The top label indicates that the packet must be		header and then process the decapsulated MPLS packet. The top label
	forwarded toward router G. Since the next hop toward router G is		indicates that the packet must be forwarded toward router G. Since
	only IP-capable, router E replaces the current top label with an		the next hop toward router G is only IP-capable, router E replaces
	MPLS-over-UDP tunnel toward router G and sends it out. That is,		the current top label with an MPLS-over-UDP tunnel toward router G
	router E pops the top label and then encapsulates the MPLS packet in		and sends it out. That is, router E pops the top label and then
	a UDP tunnel to router G.		encapsulates the MPLS packet in a UDP tunnel to router G.
	When the packet arrives at router G, router G will strip the IP-based		When the packet arrives at router G, router G will strip the IP-based
	tunnel header and then process the decapsulated MPLS packet. The top		tunnel header and then process the decapsulated MPLS packet. The top
	label indicates that the packet must be forwarded toward router H.		label indicates that the packet must be forwarded toward router H.
	Since the next hop toward router H is only IP-capable, router G would		Since the next hop toward router H is only IP-capable (D is a legacy
	replace the current top label with an MPLS-over-UDP tunnel toward		transit router), router G would replace the current top label with an
	router H and send it out. However, this would leave the original		MPLS-over-UDP tunnel toward router H and send it out. However, since
			router G reaches the bottom of the label stack (G is the penultimate
			SR-MPLS capable node on the path) this would leave the original
	packet that router A wanted to send to router H encapsulated in UDP		packet that router A wanted to send to router H encapsulated in UDP
	as if it was MPLS even though the original packet could have been any		as if it was MPLS (i.e., with a UDP header and destination port
			indicating MPLS) even though the original packet could have been any
	protocol. That is, the final SR-MPLS has been popped exposing the		protocol. That is, the final SR-MPLS has been popped exposing the
	payload packet.		payload packet.
	To handle this, when a router (here it is router G) pops the final		To handle this, when a router (here it is router G) pops the final
	SR-MPLS label, it inserts an explicit null label [RFC3032] before		SR-MPLS label, it inserts an explicit null label [RFC3032] before
	encapsulating the packet with an MPLS-over-UDP tunnel toward router H		encapsulating the packet in an MPLS-over-UDP tunnel toward router H
	and sending it out. That is, router G pops the top label, discovers		and sending it out. That is, router G pops the top label, discovers
	it has reached the bottom of stack, pushes an explicit null label,		it has reached the bottom of stack, pushes an explicit null label,
	and then encapsulates the MPLS packet in a UDP tunnel to router H.		and then encapsulates the MPLS packet in a UDP tunnel to router H.
	4.2.2. Packet Forwarding without Penultimate Hop Popping		4.2.2. Packet Forwarding without Penultimate Hop Popping
	Figure 4 demonstrates the packet walk in the case where the label		Figure 4 demonstrates the packet walk in the case where the label
	associated with each prefix-SID advertised by the owner of the		associated with each prefix-SID advertised by the owner of the
	prefix-SID is not a Penultimate Hop Popping (PHP) label (i.e., the		prefix-SID is not a Penultimate Hop Popping (PHP) label (i.e., the
	the NP flag in OSPF or the P flag in ISIS associated with the prefix		the NP flag in OSPF or the P flag in ISIS associated with the prefix
	SID is set).		SID is set). Apart from the PHP function the roles of the routers is
			unchanged from Section 4.2.1.
	+-----+ +-----+ +-----+ +-----+ +-----+		+-----+ +-----+ +-----+ +-----+ +-----+
	| A +-------+ B +-------+ C +--------+ D +--------+ H |		| A +-------+ B +-------+ C +--------+ D +--------+ H |
	+-----+ +--+--+ +--+--+ +--+--+ +-----+		+-----+ +--+--+ +--+--+ +--+--+ +-----+
	| | |		| | |
	| | |		| | |
	+--+--+ +--+--+ +--+--+		+--+--+ +--+--+ +--+--+
	| E +-------+ F +--------+ G |		| E +-------+ F +--------+ G |
	+-----+ +-----+ +-----+		+-----+ +-----+ +-----+
	skipping to change at page 9, line 32 ¶		skipping to change at page 10, line 32 ¶
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	| L(H) | | L(H) | | L(H) |		| L(H) | | L(H) | | L(H) |
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	| Packet | ---> | Packet | ---> | Packet |		| Packet | ---> | Packet | ---> | Packet |
	+--------+ +--------+ +--------+		+--------+ +--------+ +--------+
	Figure 4: Packet Forwarding Example without PHP		Figure 4: Packet Forwarding Example without PHP
	As can be seen from the figure, the SR-MPLS label for each segment is		As can be seen from the figure, the SR-MPLS label for each segment is
	left in place until the end of the segment where it is popped and the		left in place until the end of the segment where it is popped and the
	next instruction is processed. Further description can be found in		next instruction is processed.
	Section 5.
	4.2.3. Additional Forwarding Procedures		4.2.3. Additional Forwarding Procedures
	Although the description in the previous two sections is based on the		Non-MPLS Interfaces: Although the description in the previous two
	use of prefix-SIDs, tunneling SR-MPLS packets are useful when the top		sections is based on the use of prefix-SIDs, tunneling SR-MPLS
	label of a received SR-MPLS packet indicates an adjacncy-SID and the		packets is useful when the top label of a received SR-MPLS packet
	corresponding adjacent node to that adjacency-SID is not capable of		indicates an adjacency-SID and the corresponding adjacent node to
	MPLS forwarding but can still process SR-MPLS packets. In this		that adjacency-SID is not capable of MPLS forwarding but can still
	scenario the top label would be replaced by an IP tunnel toward that		process SR-MPLS packets. In this scenario the top label would be
	adjacent node and then forwarded over the corresponding link		replaced by an IP tunnel toward that adjacent node and then
	indicated by the adjacency-SID.		forwarded over the corresponding link indicated by the adjacency-
			SID.
	When encapsulating an MPLS packet with an IP tunnel header that is
	capable of encoding entropy (such as [RFC7510]), the corresponding
	entropy field (the source port in case UDP tunnel) MAY be filled with
	an entropy value that is generated by the encapsulator to uniquely
	identify a flow. However, what constitutes a flow is locally
	determined by the encapsulator. For instance, if the MPLS label
	stack contains at least one entropy label and the encapsulator is
	capable of reading that entropy label, the entropy label value could
	be directly copied to the source port of the UDP header. Otherwise,
	the encapsulator may have to perform a hash on the whole label stack
	or the five-tuple of the SR-MPLS payload if the payload is determined
	as an IP packet. To avoid re-performing the hash or hunting for the
	entropy label each time the packet is encapsulated in a UDP tunnel it
	MAY be desireable that the entropy value contained in the incoming
	packet (i.e., the UDP source port value) is retained when stripping
	the UDP header and is re-used as the entropy value of the outgoing
	packet.
	5. Forwarding Details of SR-MPLS over UDP
	This section provides supplementary details to the description found
	in Section 4.
	[RFC7510] specifies an IP-based encapsulation for MPLS, i.e., MPLS-
	in-UDP, which is applicable in some circumstances where IP-based
	encapsulation for MPLS is required and further fine-grained load
	balancing of MPLS packets over IP networks over Equal-Cost Multipath
	(ECMP) and/or Link Aggregation Groups (LAGs) is required as well.
	This section provides details about the forwarding procedure when
	when UDP encapsulation is adopted for SR-MPLS over IP.
	Nodes that are SR capable can process SR-MPLS packets. Not all of
	the nodes in an SR domain are SR capable. Some nodes may be "legacy
	routers" that cannot handle SR packets but can forward IP packets.
	An SR capable node may advertise its capabilities using the IGP as
	described in Section 4. There are six types of node in an SR domain:
	o Domain ingress nodes that receive packets and encapsulate them for
	transmission across the domain. Those packets may be any payload
	protocol including native IP packets or packets that are already
	MPLS encapsulated.
	o Legacy transit nodes that are IP routers but that are not SR
	capable (i.e., are not able to perform segment routing).
	o Transit nodes that are SR capable but that are not identified by a
	SID in the SID stack.
	o Transit nodes that are SR capable and need to perform SR routing
	because they are identified by a SID in the SID stack.
	o The penultimate SR capable node on the path that processes the
	last SID on the stack on behalf of the domain egress node.
	o The domain egress node that forwards the payload packet for
	ultimate delivery.
	The following sub-sections describe the processing behavior in each
	case.
	5.1. Domain Ingress Nodes
	Domain ingress nodes receive packets from outside the domain and
	encapsulate them to be forwarded across the domain. Received packets
	may already be SR-MPLS packets (in the case of connecting two SR-MPLS
	networks across a native IP network), or may be native IP or MPLS
	packets.
	In the latter case, the packet is classified by the domain ingress
	node and an SR-MPLS stack is imposed. In the former case the SR-MPLS
	stack is already in the packet. The top entry in the stack is popped
	from the stack and retained for use below.
	The packet is then encapsulated in UDP with the destination port set
	to 6635 to indicate "MPLS-UDP" or to 6636 to indicate "MPLS-UDP-DTLS"
	as described in [RFC7510]. The source UDP port is set randomly or to
	provide entropy as described in [RFC7510] and Section 4.2.3, above.
	The packet is then encapsulated in IP for transmission across the
	network. The IP source address is set to the domain ingress node,
	and the destination address is set to the address corresponding to
	the label that was previously popped from the stack.
	This processing is equivalent to sending the packet out of a virtual
	interface that corresponds to a virtual link between the ingress node
	and the next hop SR node realized by a UDP tunnel. The packet is
	then sent into the IP network and is routed according to the local
	FIB and applying hashing to resolve any ECMP choices.
	5.2. Legacy Transit Nodes
	A legacy transit node is an IP router that has no SR capabilities.
	When such a router receives an SR-MPLS-in-UDP packet it will carry
	out normal TTL processing and if the packet is still live it will
	forward it as it would any other UDP-in-IP packet. The packet will
	be routed toward the destination indicated in the packet header using
	the local FIB and applying hashing to resolve any ECMP choices.
	If the packet is mistakenly addressed to the legacy router, the UDP
	tunnel will be terminated and the packet will be discarded either
	because the MPLS-in-UDP port is not supported or because the
	uncovered top label has not been allocated. This is, however, a
	misconnection and should not occur unless there is a routing error.
	5.3. On-Path Pass-Through SR Nodes
	Just because a node is SR capable and receives an SR-MPLS-in-UDP
	packet does not mean that it performs SR processing on the packet.
	Only routers identified by SIDs in the SR stack need to do such
	processing.
	Routers that are not addressed by the destination address in the IP
	header simply treat the packet as a normal UDP-in-IP packet carrying
	out normal TTL processing and if the packet is still live routing the
	packet according to the local FIB and applying hashing to resolve any
	ECMP choices.
	This is important because it means that the SR stack can be kept
	relatively small and the packet can be steered through the network
	using shortest path first routing between selected SR nodes.
	5.4. SR Transit Nodes
	An SR capable node that is addressed by the top most SID in the stack
	when that is not the last SID in the stack (i.e., the S bit is not
	set) is an SR transit node. When an SR transit node receives an SR-
	MPLS-in-UDP packet that is addressed to it, it acts as follows.
	o Perform TTL processing as normal for an IP packet.
	o Determine that the packet is addressed to the local node.
	o Find that the payload is UDP and that the destination port
	indicates MPLS-in-UDP.
	o Strip the IP and UDP headers.
	o Examine the label at the top of the stack and process according to
	the FIB entry (see Section 4.1.
	* If the top label identifies this node then no PHP was used on
	the incoming segment and the label is popped. Continue the
	processing with the new top label.
	* Retain the value of the top label.
	* If the top label was advertised requesting PHP, pop the label.
	(Note that the case where this is the last label in the stack
	is covered in Section 5.5.)
	o Encapsulate the packet in UDP with the destination port set to
	6635 (or 6636 for DTLS) and the source port set for entropy. The
	entropy value SHOULD be retained from the received UDP header or
	MAY be freshly generated since this is a new UDP tunnel (see
	Section 4.2.3).
	o Encapsulate the packet in IP with the IP source address set to
	this transit router, and the destination address set to the
	address corresponding to the SID for the label value retained
	earlier.
	o Send the packet into the IP network routing the packet according
	to the local FIB and applying hashing to resolve any ECMP choices.
	5.5. Penultimate SR Transit Nodes
	The penultimate SR transit node is an SR transit node as described in
	Section 5.4 where the top label is the last label on the stack. When
	a penultimate SR transit node receives an SR-MPLS-in-UDP packet that
	is addressed to it, it processes as for any other transit node (see
	Section 5.4) except for a special case if PHP is supported for the
	final SID.
	If PHP is allowed for the final SID the penultimate SR transit node
	acts as follows:
	o Perform TTL processing as normal for an IP packet.
	o Determine that the packet is addressed to the local node.
	o Find that the payload is UDP and that the destination port
	indicates MPLS-in-UDP.
	o Strip the IP and UDP headers.
	o Examine the label at the top of the stack and process according to
	the FIB entry (see Section 4.1.
	* If the top label identifies this node then no PHP was used on
	the incoming segment and the label is popped. Continue the
	processing with the new top label.
	* Retain the value of the top label.
	* If the top label was advertised requesting PHP, pop the label.
	This will have been the last label in the stack. Push an
	explicit null label [RFC3032] (0 for IPv4 and 2 for IPv6) with
	bottom of stack (S bit) set.
	o Encapsulate the packet in UDP with the destination port set to
	6635 (or 6636 for DTLS) and the source port set for entropy. The
	entropy value SHOULD be retained from the received UDP header or
	MAY be freshly generated since this is a new UDP tunnel.
	o Encapsulate the packet in IP with the IP source address set to
	this transit router, and the destination address set to the domain
	egress node IP address corresponding to the SID for the label
	value retained earlier.
	o Send the packet into the IP network routing the packet according
	to the local FIB and applying hashing to resolve any ECMP choices.
	5.5.1. A Note on Segment Routing Paths and Penultimate Hop Popping
	End-to-end SR paths are comprised of multiple segments. The end		When to use IP-based Tunnel: The description in the previous two
	point of each segment is identified by a SID in the SID stack. In		sections is based on the assumption that MPLS-over-UDP tunnel is
	normal SR processing a penultimate hop is the router that performs SR		used when the nexthop towards the next segment is not MPLS-
	routing immediately prior to the end-of-segment router. PHP applies		enabled. However, even in the case where the nexthop towards the
	at the penultimate router in a segment.		next segment is MPLS-capable, an MPLS-over-UDP tunnel towards the
			next segment could still be used instead due to local policies.
			For instance, in the example as described in Figure 4, assume F is
			now an SR-MPLS-capable transit node while all the other
			assumptions keep unchanged, since F is not identified by a SID in
			the stack and an MPLS-over-UDP tunnel is preferred to an MPLS LSP
			according to local policies, router E would replace the current
			top label with an MPLS-over-UDP tunnel toward router G and send it
			out.
	With SR-MPLS-in-UDP encapsulation, each SR segment is achieved using		IP Header Fields: When encapsulating an MPLS packet in UDP, the
	an MPLS-in-UDP tunnel that runs the full length of the segment. The		resulting packet is further encapsulated in IP for transmission.
	SR SID stack on a packet is only examined at the head and tail ends		IPv4 or IPv6 may be used according to the capabilities of the
	of this segment. Thus, each segment is effectively one hop long in		network. The address fields are set as described in Section 3.
	the SR overlay network and if there is any PHP processing it takes		The other IP header fields (such as DSCP code point, or IPv6 Flow
	place at the head-end of the segment.		Label) on each UDP-encapsulated segment can be set according to
			the operator's policy: they may be copied from the header of the
			incoming packet; they may be promoted from the header of the
			payload packet; they may be set according to instructions
			programmed to be associated with the SID; or they may be
			configured dependent on the outgoing interface and payload.
	5.6. Domain Egress Nodes		Entropy and ECMP: When encapsulating an MPLS packet with an IP
			tunnel header that is capable of encoding entropy (such as
			[RFC7510]), the corresponding entropy field (the source port in
			case UDP tunnel) MAY be filled with an entropy value that is
			generated by the encapsulator to uniquely identify a flow.
			However, what constitutes a flow is locally determined by the
			encapsulator. For instance, if the MPLS label stack contains at
			least one entropy label and the encapsulator is capable of reading
			that entropy label, the entropy label value could be directly
			copied to the source port of the UDP header. Otherwise, the
			encapsulator may have to perform a hash on the whole label stack
			or the five-tuple of the SR-MPLS payload if the payload is
			determined as an IP packet. To avoid re-performing the hash or
			hunting for the entropy label each time the packet is encapsulated
			in a UDP tunnel it MAY be desirable that the entropy value
			contained in the incoming packet (i.e., the UDP source port value)
			is retained when stripping the UDP header and is re-used as the
			entropy value of the outgoing packet.
	The domain egress acts as follows:		5. IANA Considerations
	o Perform TTL processing as normal for an IP packet.		This document makes no requests for IANA action.
	o Determine that the packet is addressed to the local node.		6. Security Considerations
	o Find that the payload is UDP and that the destination port		The security consideration of [RFC8354] and [RFC7510] apply. DTLS
	indicates MPLS-in-UDP.		[RFC6347] SHOULD be used where security is needed on an MPLS-SR-over-
			UDP segment.
	o Strip the IP and UDP headers.		It is difficult for an attacker to pass a raw MPLS encoded packet
			into a network and operators have considerable experience at
			excluding such packets at the network boundaries.
	o Examine the label at the top of the stack and process according to		It is easy for an ingress node to detect any attempt to smuggle an IP
	the FIB entry (see Section 4.1.		packet into the network since it would see that the UDP destination
			port was set to MPLS. SR packets not having a destination address
			terminating in the network would be transparently carried and would
			pose no security risk to the network under consideration.
	* If the top label identifies this node then no PHP was used on		Where control plane techniques are used (as described in
	the incoming segment and the label is popped. Continue the		Authors' Addresses it is important that these protocols are
	processing with the new top label.		adequately secured for the environment in which they are run.
	* If there is another label it should be the explicit null. Pop		7. Contributors
	it but retain its value.
	o Forward the payload packet according to its type (as potentially		Ahmed Bashandy
	indicated by the value of the popped explicit null label) and the		Individual
	local routing/forwarding mechanisms.		Email: abashandy.ietf@gmail.com
	6. Contributors
	Clarence Filsfils		Clarence Filsfils
	Cisco		Cisco
	Email: cfilsfil@cisco.com		Email: cfilsfil@cisco.com
	John Drake		John Drake
	Juniper		Juniper
	Email: jdrake@juniper.net		Email: jdrake@juniper.net
	Shaowen Ma		Shaowen Ma
	Juniper		Juniper
	skipping to change at page 17, line 5 ¶		skipping to change at page 13, line 30 ¶
	Email: gunter.van_de_velde@nokia.com		Email: gunter.van_de_velde@nokia.com
	Tal Mizrahi		Tal Mizrahi
	Marvell		Marvell
	Email: talmi@marvell.com		Email: talmi@marvell.com
	Jeff Tantsura		Jeff Tantsura
	Individual		Individual
	Email: jefftant@gmail.com		Email: jefftant@gmail.com
	7. Acknowledgements		8. Acknowledgements
	Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,		Thanks to Joel Halpern, Bruno Decraene, Loa Andersson, Ron Bonica,
	Eric Rosen, Jim Guichard, and Gunter Van De Velde for their		Eric Rosen, Jim Guichard, and Gunter Van De Velde for their
	insightful comments on this draft.		insightful comments on this draft.
	8. IANA Considerations		9. References
	No IANA action is required.
	9. Security Considerations
	TBD.
	10. References
	10.1. Normative References		9.1. Normative References
	[I-D.ietf-isis-encapsulation-cap]		[I-D.ietf-isis-encapsulation-cap]
	Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,		Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
	L., and L. Jalil, "Advertising Tunnelling Capability in		L., and L. Jalil, "Advertising Tunnelling Capability in
	IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in		IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in
	progress), April 2017.		progress), April 2017.
	[I-D.ietf-isis-segment-routing-extensions]		[I-D.ietf-isis-segment-routing-extensions]
	Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,		Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
	Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,		Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
	"IS-IS Extensions for Segment Routing", draft-ietf-isis-		"IS-IS Extensions for Segment Routing", draft-ietf-isis-
	segment-routing-extensions-15 (work in progress), December		segment-routing-extensions-16 (work in progress), April
	2017.		2018.
	[I-D.ietf-ospf-encapsulation-cap]		[I-D.ietf-ospf-encapsulation-cap]
	Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.		Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.
	Jalil, "The Tunnel Encapsulations OSPF Router		Jalil, "The Tunnel Encapsulations OSPF Router
	Information", draft-ietf-ospf-encapsulation-cap-09 (work		Information", draft-ietf-ospf-encapsulation-cap-09 (work
	in progress), October 2017.		in progress), October 2017.
	[I-D.ietf-ospf-segment-routing-extensions]		[I-D.ietf-ospf-segment-routing-extensions]
	Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,		Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
	Shakir, R., Henderickx, W., and J. Tantsura, "OSPF		Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
	Extensions for Segment Routing", draft-ietf-ospf-segment-		Extensions for Segment Routing", draft-ietf-ospf-segment-
	routing-extensions-24 (work in progress), December 2017.		routing-extensions-25 (work in progress), April 2018.
	[I-D.ietf-spring-segment-routing-mpls]		[I-D.ietf-spring-segment-routing-mpls]
	Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,		Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
	Litkowski, S., and R. Shakir, "Segment Routing with MPLS		Litkowski, S., and R. Shakir, "Segment Routing with MPLS
	data plane", draft-ietf-spring-segment-routing-mpls-12		data plane", draft-ietf-spring-segment-routing-mpls-13
	(work in progress), February 2018.		(work in progress), April 2018.
	[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>.
	[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol		[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
	Label Switching Architecture", RFC 3031,		Label Switching Architecture", RFC 3031,
	DOI 10.17487/RFC3031, January 2001,		DOI 10.17487/RFC3031, January 2001,
	<https://www.rfc-editor.org/info/rfc3031>.		<https://www.rfc-editor.org/info/rfc3031>.
	[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,		[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
	Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack		Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
	Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,		Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
	<https://www.rfc-editor.org/info/rfc3032>.		<https://www.rfc-editor.org/info/rfc3032>.
			[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
			Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
			January 2012, <https://www.rfc-editor.org/info/rfc6347>.
	[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,		[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
	"Encapsulating MPLS in UDP", RFC 7510,		"Encapsulating MPLS in UDP", RFC 7510,
	DOI 10.17487/RFC7510, April 2015,		DOI 10.17487/RFC7510, April 2015,
	<https://www.rfc-editor.org/info/rfc7510>.		<https://www.rfc-editor.org/info/rfc7510>.
	[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,		[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
	Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute		Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
	Advertisement", RFC 7684, DOI 10.17487/RFC7684, November		Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
	2015, <https://www.rfc-editor.org/info/rfc7684>.		2015, <https://www.rfc-editor.org/info/rfc7684>.
	skipping to change at page 18, line 44 ¶		skipping to change at page 15, line 24 ¶
	[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions		[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
	for Advertising Router Information", RFC 7981,		for Advertising Router Information", RFC 7981,
	DOI 10.17487/RFC7981, October 2016,		DOI 10.17487/RFC7981, October 2016,
	<https://www.rfc-editor.org/info/rfc7981>.		<https://www.rfc-editor.org/info/rfc7981>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	10.2. Informative References		9.2. Informative References
	[I-D.ietf-6man-segment-routing-header]		[I-D.ietf-6man-segment-routing-header]
	Previdi, S., Filsfils, C., Raza, K., Dukes, D., Leddy, J.,		Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
	Field, B., daniel.voyer@bell.ca, d.,		d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
	daniel.bernier@bell.ca, d., Matsushima, S., Leung, I.,		(SRH)", draft-ietf-6man-segment-routing-header-13 (work in
	Linkova, J., Aries, E., Kosugi, T., Vyncke, E., Lebrun,		progress), May 2018.
	D., Steinberg, D., and R. Raszuk, "IPv6 Segment Routing
	Header (SRH)", draft-ietf-6man-segment-routing-header-08
	(work in progress), January 2018.
	[I-D.ietf-mpls-spring-entropy-label]		[I-D.ietf-mpls-spring-entropy-label]
	Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,		Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
	Shakir, R., and J. Tantsura, "Entropy label for SPRING		Shakir, R., and J. Tantsura, "Entropy label for SPRING
	tunnels", draft-ietf-mpls-spring-entropy-label-08 (work in		tunnels", draft-ietf-mpls-spring-entropy-label-11 (work in
	progress), January 2018.		progress), May 2018.
			[RFC8354] Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R.,
			Ed., and M. Townsley, "Use Cases for IPv6 Source Packet
			Routing in Networking (SPRING)", RFC 8354,
			DOI 10.17487/RFC8354, March 2018,
			<https://www.rfc-editor.org/info/rfc8354>.
	Authors' Addresses		Authors' Addresses
	Xiaohu Xu		Xiaohu Xu
	Alibaba		Alibaba
	Email: xiaohu.xxh@alibaba-inc.com		Email: xiaohu.xxh@alibaba-inc.com
	Stewart Bryant		Stewart Bryant
	Huawei		Huawei
	Email: stewart.bryant@gmail.com		Email: stewart.bryant@gmail.com
	Adrian Farrel		Adrian Farrel
	Juniper		Juniper
	Email: afarrel@juniper.net		Email: afarrel@juniper.net
	skipping to change at page 19, line 37 ¶		skipping to change at page 16, line 14 ¶
	Stewart Bryant		Stewart Bryant
	Huawei		Huawei
	Email: stewart.bryant@gmail.com		Email: stewart.bryant@gmail.com
	Adrian Farrel		Adrian Farrel
	Juniper		Juniper
	Email: afarrel@juniper.net		Email: afarrel@juniper.net
	Ahmed Bashandy		Syed Hassan
	Cisco		Cisco
	Email: bashandy@cisco.com		Email: shassan@cisco.com
	Wim Henderickx		Wim Henderickx
	Nokia		Nokia
	Email: wim.henderickx@nokia.com		Email: wim.henderickx@nokia.com
	Zhenbin Li		Zhenbin Li
	Huawei		Huawei
	Email: lizhenbin@huawei.com		Email: lizhenbin@huawei.com
End of changes. 55 change blocks.
	368 lines changed or deleted		209 lines changed or added
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