< draft-ietf-isis-segment-routing-msd-08.txt		draft-ietf-isis-segment-routing-msd-09.txt >
	IS-IS Working Group J. Tantsura		IS-IS Working Group J. Tantsura
	Internet-Draft Individual		Internet-Draft Individual
	Intended status: Standards Track U. Chunduri		Intended status: Standards Track U. Chunduri
	Expires: July 8, 2018 Huawei Technologies		Expires: July 14, 2018 Huawei Technologies
	S. Aldrin		S. Aldrin
	Google, Inc		Google, Inc
	L. Ginsberg		L. Ginsberg
	Cisco Systems		Cisco Systems
	January 04, 2018		January 10, 2018
	Signaling MSD (Maximum SID Depth) using IS-IS		Signaling MSD (Maximum SID Depth) using IS-IS
	draft-ietf-isis-segment-routing-msd-08		draft-ietf-isis-segment-routing-msd-09
	Abstract		Abstract
	This document proposes a way to signal Maximum SID Depth (MSD)		This document defines a way for an IS-IS Router to advertise multiple
	supported by a node and/or link granularity by an IS-IS Router. In a		types of supported Maximum SID Depths (MSDs) at node and/or link
	Segment Routing (SR) enabled network a centralized controller that		granularity. Such advertisements allow entities (e.g., centralized
	programs SR tunnels needs to know the MSD supported by the head-end		controllers) to determine whether a particular SID stack is
	at node and/or link granularity to impose the SID stack of an		supportable in a given network. This document only defines one type
	appropriate depth. MSD is relevant to the head-end of a SR tunnel or		of MSD (maximum label imposition) - but defines an encoding which can
	Binding-SID anchor node where Binding-SID expansions might result in		support other MSD types.
	creation of a new SID stack.
	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 July 8, 2018.		This Internet-Draft will expire on July 14, 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
	skipping to change at page 2, line 23 ¶		skipping to change at page 2, line 20 ¶
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Conventions used in this document . . . . . . . . . . . . 3		1.1. Conventions used in this document . . . . . . . . . . . . 3
	1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3		1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
	1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3		1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4		2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
	3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4		3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
	4. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5		4. Using Node and Link MSD Advertisements . . . . . . . . . . . 5
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 6		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7		8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
	9.1. Normative References . . . . . . . . . . . . . . . . . . 7		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	9.2. Informative References . . . . . . . . . . . . . . . . . 7		10.1. Normative References . . . . . . . . . . . . . . . . . . 7
			10.2. Informative References . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	When Segment Routing tunnels are computed by a centralized		When Segment Routing(SR) paths are computed by a centralized
	controller, it is critical that the controller learns the MSD		controller, it is critical that the controller learns the Maximum SID
	"Maximum SID Depth" of the node or link SR tunnel exits over, so the		Depth(MSD) which can be imposed at the node/link a given SR path is
	SID stack depth of a path computed doesn't exceed the number of SID's		applied so as to insure that the SID stack depth of a computed path
	the node is capable of imposing. This document describes how to use		doesn't exceed the number of SIDs the node is capable of imposing.
	IS-IS to signal the MSD of a node or link to a centralized
	controller.
	PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD		PCEP SR extensions draft [I-D.ietf-pce-segment-routing] signals MSD
	in SR PCE Capability TLV and METRIC Object. However, if PCEP is not		in SR PCE Capability TLV and METRIC Object. However, if PCEP is not
	supported/configured on the head-end of a SR tunnel or a Binding-SID		supported/configured on the head-end of a SR tunnel or a Binding-SID
	anchor node and controller does not participate in IGP routing, it		anchor node and controller does not participate in IGP routing, it
	has no way to learn the MSD of nodes and links which has been		has no way to learn the MSD of nodes and links which has been
	configured. BGP-LS [RFC7752] defines a way to expose topology and		configured. BGP-LS [RFC7752] defines a way to expose topology and
	associated attributes and capabilities of the nodes in that topology		associated attributes and capabilities of the nodes in that topology
	to a centralized controller. MSD signaling by BGP-LS has been		to a centralized controller. MSD signaling by BGP-LS has been
	defined in [I-D.ietf-idr-bgp-ls-segment-routing-msd]. Typically,		defined in [I-D.ietf-idr-bgp-ls-segment-routing-msd]. Typically,
	BGP-LS is configured on a small number of nodes, that do not		BGP-LS is configured on a small number of nodes, that do not
	necessarily act as head-ends. In order, for BGP-LS to signal MSD for		necessarily act as head-ends. In order, for BGP-LS to signal MSD for
	all the nodes and links in the network MSD is relevant, MSD		all the nodes and links in the network MSD is relevant, MSD
	capabilites should be advertised to every IS-IS router in the		capabilites should be advertised to every IS-IS router in the
	network.		network.
			Other types of MSD are known to be useful. For example,
	[I-D.ietf-isis-mpls-elc] defines Readable Label Depth Capability		[I-D.ietf-isis-mpls-elc] defines Readable Label Depth Capability
	(RLDC) that is used by a head-end to insert Entropy Label (EL) at		(RLDC) that is used by a head-end to insert Entropy Label (EL) at
	appropriate depth, so it could be read by transit nodes. MSD in		appropriate depth, so it could be read by transit nodes.
	contrary signals ability to impose SID's stack of a particular depth.
	MSD of type 1 (IANA Registry), called Base MSD, is used to signal the		This document defines an extension to IS-IS used to advertise one or
	total number of SID's a node is capable of imposing, to be used by a		more types of MSD at node and/or link granularity. It also creates
	path computation element/controller. In case, there are additional		an IANA registry for assigning MSD type identifiers. It also defines
	SID's (e.g. service) that are to be imposed to the stack - this would		one MSD type called Base MPLS Imposition MSD. In the future it is
	be signaled with an another MSD type (TBD), no adjustment to the Base		expected that new MSD types will be defined to signal additional
	MSD should be made. In the future, new MSD types could be defined to		capabilities e.g., entropy labels, SIDs that can be imposed through
	signal additional capabilities: entropy labels, SID's that can be		recirculation, or SIDs associated with another dataplane e.g., IPv6.
	imposed thru recirculation, or another dataplane e.g IPv6.
	1.1. Conventions used in this document		1.1. Conventions used in this document
	1.1.1. Terminology		1.1.1. Terminology
	BGP-LS: Distribution of Link-State and TE Information using Border		BGP-LS: Distribution of Link-State and TE Information using Border
	Gateway Protocol		Gateway Protocol
			BMI: Base MPLS Imposition is the number of MPLS labels which can be
			imposed inclusive of any service/transport labels
	IS-IS: Intermediate System to Intermediate System		IS-IS: Intermediate System to Intermediate System
	MSD: Maximum SID Depth - a number of SID's a node or a link on a node		MSD: Maximum SID Depth - the number of SIDs a node or a link on a
	is capable of imposing		node can support
	PCC: Path Computation Client		PCC: Path Computation Client
	PCE: Path Computation Element		PCE: Path Computation Element
	PCEP: Path Computation Element Protocol		PCEP: Path Computation Element Protocol
	SID: Segment Identifier		SID: Segment Identifier
	SR: Segment Routing		SR: Segment Routing
	1.2. Requirements Language		1.2. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	2. Node MSD Advertisement		2. Node MSD Advertisement
	A new sub-TLV "Node MSD sub-TLV" is defined within the body of IS-IS		A new sub-TLV "Node MSD sub-TLV" is defined within the body of the
	Router Capability TLV [RFC7981], to carry the provisioned MSD of the		IS-IS Router Capability TLV [RFC7981], to carry the provisioned
	router originating the Router Capability TLV. Node MSD is the lowest		MSD(s) of the router originating the Router Capability TLV. Node MSD
	MSD supported by the node of any interface and if not known throught		is the lowest MSD supported by the node on any interface. MSD values
	an API, can be provisioned in IS-IS instance.		may be learned via a hardware API or may be provisioned.
	0 1 2 3		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		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length | Sub-Type and Value pair |		| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MSD-Type | MSD Value |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			// ................... //
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MSD-Type | MSD Value |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 1: Node MSD Sub-TLV		Figure 1: Node MSD Sub-TLV
	The Type (1 byte) of this sub-TLV has value of 23.		The Type (1 byte) of this sub-TLV has value of 23.
	Length is variable (minimum of 2, multiple of 2 octets) and		Length is variable (minimum of 2, multiple of 2 octets) and
	represents the total length of value field.		represents the total length of value field.
	Value field consists of a 1 octet Sub-Type (IANA Registry) and 1		Value field consists of one or more pairs of a 1 octet MSD-Type (IANA
	octet Value. There could be one or more of the Sub-Type/Value pairs.		Registry) and 1 octet Value.
	Sub-Type 1 (IANA Section), MSD and the Value field associated with
	the Sub-Type contains maximum MSD of the router originating the
	Router Capability TLV.
	Node MSD value is a number in the range of 0-254. 0 represents lack
	of the ability to impose SID stack of any depth; any other value
	represents that of the node. This value SHOULD represent the lowest
	value supported by node.
	Other Sub-Types other than defined above are reserved for future		Node MSD value is a number in the range of 0-255. 0 represents lack
	extensions.		of the ability to support SID stack of any depth; any other value
			represents that of the node. This value MUST represent the lowest
			value supported by any link associated with the node.
	This sub-TLV is optional. The scope of the advertisement is specific		This sub-TLV is optional. The scope of the advertisement is specific
	to the deployment.		to the deployment.
	3. Link MSD Advertisement		3. Link MSD Advertisement
	A new sub-TLV - Link MSD sub-TLV is defined for TLVs 22, 23, 141,		A new sub-TLV - Link MSD sub-TLV is defined for TLVs 22, 23, 141,
	222, and 223 to carry the provisioned MSD of the interface associated		222, and 223 to carry the MSD of the interface associated with the
	with the link.		link. MSD values may be learned via a hardware API or may be
			provisioned.
	0 1 2 3		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		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length | Sub-Type and Value pair |		| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MSD-Type | MSD Value |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			// ................... //
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MSD-Type | MSD Value |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2: Link MSD Sub-TLV		Figure 2: Link MSD Sub-TLV
	The Type (1 byte) of this sub-TLV has value of 15.		The Type (1 byte) of this sub-TLV has value of 15.
	Length is variable and similar to what is defined in Section 2.		Length is variable (minimum of 2, multiple of 2 octets) and
			represents the total length of value field.
	Value field consists of a 1 octet sub-type (IANA Registry) and 1		Value field consists of one or more pairs of a 1 octet MSD-Type (IANA
	octet value. There could be one or more of the Sub-Type/Value pairs.		Registry) and 1 octet Value.
	Sub-Type 1 (IANA Section), MSD and the Value field associated with		Link MSD value is a number in the range of 0-255. 0 represents lack
	the Sub-Type contains Link MSD of the router originating the		of the ability to support SID stack of any depth; any other value
	corresponding TLV's 22, 23, 141, 222, and 223.		represents that of the link when used as an outgoing link.
	The value of Link MSD represents MSD on the outgoing link. Link MSD		This sub-TLV is optional. The scope of the advertisement is specific
	is a number in the range of 0-254. 0 represents lack of the ability		to the deployment.
	to impose SID stack of any depth; any other value represents that of
	the particular link MSD value.
	4. Node MSD vs Link MSD conflict resolution		4. Using Node and Link MSD Advertisements
	When both Node MSD and Link MSD are present, the value of the Link		When Link MSD is present for a given MSD type, the value of the Link
	MSD MUST be used.		MSD MUST be used in preference to the Node MSD.
	5. IANA Considerations		The meaning of the absence of both Node and Link MSD advertisements
			for a given MSD type is specific to the MSD type. Generally it can
			only be inferred that the advertising node does not support
			advertisement of that MSD type. However, in some cases the lack of
			advertisement might imply that the functionality associated with the
			MSD type is not supported. The correct interpretation MUST be
			specified when an MSD type is defined.
	This document includes a request to IANA to allocate sub-TLV type		5. Base MPLS Imposition MSD
	codes for the new sub TLV proposed in Section 2 of this document from
	IS-IS Router Capability TLV Registry as defined by [RFC7981].
	Following values have been allocated by IANA:		Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS
			labels a node is capable of imposing, including any service/transport
			labels.
			Absence of BMI-MSD advertisements indicates only that the advertising
			node does not support advertisement of this capability.
			6. IANA Considerations
			This document requests IANA to allocate a sub-TLV type code for the
			new sub TLV proposed in Section 2 of this document from IS-IS Router
			Capability TLV Registry as defined by [RFC7981].
			The following value has been allocated by IANA:
	Value Description Reference		Value Description Reference
	----- --------------- -------------		----- --------------- -------------
	23 Node MSD This document		23 Node MSD This document
	Figure 3: Node MSD		Figure 3: Node MSD
	For the Link MSD, we request IANA to allocate new sub-TLV codes as		This document requests IANA to allocate a sub-TLV type code as
	defined in Section 3 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223		defined in Section 3 from Sub-TLVs for TLVs 22, 23, 141, 222 and 223
	registry.		registry.
			The following value has been allocated by IANA:
	Value Description Reference		Value Description Reference
	----- --------------- -------------		----- --------------- -------------
	15 Link MSD This document		15 Link MSD This document
	Figure 4: Link MSD		Figure 4: Link MSD
	Per TLV information where Link MSD sub-TLV can be part of:		Per TLV information where Link MSD sub-TLV can be part of:
	TLV 22 23 25 141 222 223		TLV 22 23 25 141 222 223
	--- --------------------		--- --------------------
	y y y y y y		y y y y y y
	Figure 5: TLVs where LINK MSD Sub-TLV can be present		Figure 5: TLVs where LINK MSD Sub-TLV can be present
	This document requests creation of a new IANA managed registry under		This document requests creation of a new IANA managed registry under
	a new category of "Interior Gateway Protocol (IGP) Parameters" IANA		a new category of "Interior Gateway Protocol (IGP) Parameters" IANA
	registries to identify MSD types as proposed in Section 2, Section 3.		registries to identify MSD types as proposed in Section 2 and
	The registration procedure is "Expert Review" as defined in		Section 3. The registration procedure is "Expert Review" as defined
	[RFC8126]. Suggested registry name is "MSD Sub-types". Types are an		in [RFC8126]. Suggested registry name is "MSD types". Types are an
	unsigned 8 bit number. The following values are defined by this		unsigned 8 bit number. The following values are defined by this
	document		document
	Value Name Reference		Value Name Reference
	----- --------------------- -------------		----- --------------------- -------------
	0 Reserved This document		0 Reserved This document
	1 Base MSD This document		1 Base MPLS Imposition MSD This document
	2-250 Unassigned This document		2-250 Unassigned This document
	251-254 Experimental This document		251-254 Experimental This document
	255 Reserved This document		255 Reserved This document
	Figure 6: MSD Sub-type Codepoints Registry		Figure 6: MSD Types Codepoints Registry
	6. Security Considerations		7. Security Considerations
	Security considerations, as specified by [RFC7981] are applicable to		Security considerations, as specified by [RFC7981] are applicable to
	this document		this document
	7. Contributors		8. Contributors
	The following people contributed to this document:		The following people contributed to this document:
	Peter Psenak		Peter Psenak
	Email: ppsenak@cisco.com		Email: ppsenak@cisco.com
	8. Acknowledgements		9. Acknowledgements
	The authors would like to thank Stephane Litkowski and Bruno Decraene		The authors would like to thank Stephane Litkowski and Bruno Decraene
	for their reviews and valuable comments.		for their reviews and valuable comments.
	9. References		10. References
	9.1. Normative References		10.1. Normative References
	[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>.
	[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
	Engineering", RFC 5305, DOI 10.17487/RFC5305, October
	2008, <https://www.rfc-editor.org/info/rfc5305>.
	[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>.
	9.2. Informative References		10.2. Informative References
	[I-D.ietf-idr-bgp-ls-segment-routing-msd]		[I-D.ietf-idr-bgp-ls-segment-routing-msd]
	Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,		Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
	"Signaling Maximum SID Depth using Border Gateway Protocol		"Signaling Maximum SID Depth using Border Gateway Protocol
	Link-State", draft-ietf-idr-bgp-ls-segment-routing-msd-01		Link-State", draft-ietf-idr-bgp-ls-segment-routing-msd-01
	(work in progress), October 2017.		(work in progress), October 2017.
	[I-D.ietf-isis-mpls-elc]		[I-D.ietf-isis-mpls-elc]
	Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.		Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
	Litkowski, "Signaling Entropy Label Capability and		Litkowski, "Signaling Entropy Label Capability and
	Readable Label-stack Depth Using IS-IS", draft-ietf-isis-		Readable Label-stack Depth Using IS-IS", draft-ietf-isis-
	mpls-elc-03 (work in progress), January 2018.		mpls-elc-03 (work in progress), January 2018.
	[I-D.ietf-pce-segment-routing]		[I-D.ietf-pce-segment-routing]
	Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,		Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
	and J. Hardwick, "PCEP Extensions for Segment Routing",		and J. Hardwick, "PCEP Extensions for Segment Routing",
	draft-ietf-pce-segment-routing-11 (work in progress),		draft-ietf-pce-segment-routing-11 (work in progress),
	November 2017.		November 2017.
	[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
	dual environments", RFC 1195, DOI 10.17487/RFC1195,
	December 1990, <https://www.rfc-editor.org/info/rfc1195>.
	[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
	Topology (MT) Routing in Intermediate System to
	Intermediate Systems (IS-ISs)", RFC 5120,
	DOI 10.17487/RFC5120, February 2008,
	<https://www.rfc-editor.org/info/rfc5120>.
	[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and		[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
	S. Ray, "North-Bound Distribution of Link-State and		S. Ray, "North-Bound Distribution of Link-State and
	Traffic Engineering (TE) Information Using BGP", RFC 7752,		Traffic Engineering (TE) Information Using BGP", RFC 7752,
	DOI 10.17487/RFC7752, March 2016,		DOI 10.17487/RFC7752, March 2016,
	<https://www.rfc-editor.org/info/rfc7752>.		<https://www.rfc-editor.org/info/rfc7752>.
	[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for		[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
	Writing an IANA Considerations Section in RFCs", BCP 26,		Writing an IANA Considerations Section in RFCs", BCP 26,
	RFC 8126, DOI 10.17487/RFC8126, June 2017,		RFC 8126, DOI 10.17487/RFC8126, June 2017,
	<https://www.rfc-editor.org/info/rfc8126>.		<https://www.rfc-editor.org/info/rfc8126>.
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