< draft-ietf-idr-bgp-ls-segment-routing-msd-01.txt		draft-ietf-idr-bgp-ls-segment-routing-msd-02.txt >
	IDR Working Group J. Tantsura		IDR Working Group J. Tantsura
	Internet-Draft Individual		Internet-Draft Nuage Networks
	Intended status: Standards Track U. Chunduri		Intended status: Standards Track U. Chunduri
	Expires: April 18, 2018 Huawei Technologies		Expires: February 14, 2019 Huawei USA
	G. Mirsky		G. Mirsky
	ZTE Corp.		ZTE Corp.
	S. Sivabalan		S. Sivabalan
	Cisco		Cisco
	October 15, 2017		August 13, 2018
	Signaling Maximum SID Depth using Border Gateway Protocol Link-State		Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link-
	draft-ietf-idr-bgp-ls-segment-routing-msd-01		State
			draft-ietf-idr-bgp-ls-segment-routing-msd-02
	Abstract		Abstract
	This document proposes a way to signal Maximum SID Depth (MSD)		This document defines a way for a Border Gateway Protocol Link-State
	supported by a node at node and/or link granularity by a BGP-LS		(BGP-LS) speaker to advertise multiple types of supported Maximum SID
	speaker. In a Segment Routing (SR) enabled network a centralized		Depths (MSDs) at node and/or link granularity.
	controller that programs SR tunnels needs to know the MSD supported
	by the head-end at node and/or link granularity to push the SID stack		Such advertisements allow logically centralized entities (e.g.,
	of an appropriate depth. MSD is relevant to the head-end of a SR		centralized controllers) to determine whether a particular SID stack
	tunnel or Binding-SID anchor node where Binding-SID expansions might		can be supported in a given network.
	result in 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
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	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 April 18, 2018.		This Internet-Draft will expire on February 14, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 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.
			Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	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
	1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3		1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
	2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3		2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
	3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 4		3. MSD supported by a node . . . . . . . . . . . . . . . . . . . 3
	4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4		4. MSD supported on a link . . . . . . . . . . . . . . . . . . . 4
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 5		6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	8.1. Normative References . . . . . . . . . . . . . . . . . . 5		8.1. Normative References . . . . . . . . . . . . . . . . . . 5
	8.2. Informative References . . . . . . . . . . . . . . . . . 6		8.2. Informative References . . . . . . . . . . . . . . . . . 6
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	When Segment Routing tunnels are computed by a centralized		When Segment Routing tunnels are computed by a centralized
	controller, it is critical that the controller learns the MSD		controller, it is critical that the controller learns the MSD
	"Maximum SID Depth" of the node or link SR tunnel exits over, so the		"Maximum SID Depth" of the node or link SR tunnel exits over, so the
	SID stack depth of a path computed doesn't exceed the number of SIDs		SID stack depth of a path computed doesn't exceed the number of SIDs
	the node is capable of imposing. This document describes how to use		the node is capable of imposing. This document describes how to use
	BGP-LS to signal the MSD of a node or link to a centralized		BGP-LS to signal the MSD of a node or link to a centralized
	controller.		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.		to a centralized controller.
	MSD of sub-type 1, called Base MSD as defined in Section 3 is used to		Other types of MSD are known to be useful. For example,
	signal the number of SID's a node is capable of imposing, to be used		[I-D.ietf-ospf-mpls-elc] and [I-D.ietf-isis-mpls-elc] define Readable
	by a path computation element/controller. In case, there are
	additional labels (e.g. service) that are to be pushed to the stack -		Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	this would be signaled with an another MSD type (TBD), no adjustment
	to the Base MSD should be made. In the future, new MSD types could		Label Depth Capability (RLDC) that is used by a head-end to insert an
	be defined to signal additional capabilities: entropy labels, labels		Entropy Label (EL) at a depth that can be read by transit nodes.
	that can be pushed 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
	MSD: Maximum SID Depth		MSD: Maximum SID Depth
	skipping to change at page 3, line 34 ¶		skipping to change at page 3, line 33 ¶
	PCEP: Path Computation Element Protocol		PCEP: Path Computation Element Protocol
	SID: Segment Identifier		SID: Segment Identifier
	SR: Segment routing		SR: Segment routing
	1.1.2. Requirements Language		1.1.2. 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", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in BCP
	[RFC2119].		14 [RFC2119] [RFC8174] when, and only when, they appear in all
			capitals, as shown here .
	2. Problem Statement		2. Problem Statement
	In existing technology only PCEP has extension to signal the MSD (SR		In existing technology only PCEP has extension to signal the MSD (SR
	PCE Capability TLV/ METRIC Object as defined in		PCE Capability TLV/ METRIC Object as defined in
	[I-D.ietf-pce-segment-routing],If PCEP is not supported by the node		[I-D.ietf-pce-segment-routing],If PCEP is not supported by the node
	(head-end of the SR tunnel) controller has no way to learn the MSD of		(head-end of the SR tunnel) controller has no way to learn the MSD of
	the node/link configured. OSPF and IS-IS extensions are defined in:		the node/link configured. OSPF and IS-IS extensions are defined in:
	[I-D.ietf-ospf-segment-routing-msd]		[I-D.ietf-ospf-segment-routing-msd]
	[I-D.ietf-isis-segment-routing-msd]		[I-D.ietf-isis-segment-routing-msd]
	3. MSD supported by a node		3. MSD supported by a node
	Node MSD is encoded in a new Node Attribute TLV, as defined in		Node MSD is encoded in a new Node Attribute TLV, as defined in
	[RFC7752]		[RFC7752]
			Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length |		| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sub-Type and Value ...		| Sub-Type and Value ...
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
	Figure 1: Node attribute format		Figure 1: Node attribute format
	Type : A 2-octet field specifiying code-point of the new TLV type.		Type : A 2-octet field specifying code-point of the new TLV type.
	Code-point:(TBD1) from BGP-LS Node Descriptor, Link Descriptor,		Code-point:(TBD1) from BGP-LS Node Descriptor, Link Descriptor,
	Prefix Descriptor, and Attribute TLVs registry		Prefix Descriptor, and Attribute TLVs registry
	Length: A 2-octet field that indicates the length of the value		Length: A 2-octet field that indicates the length of the value
	portion		portion
	Sub-Type and value fields are as defined in corresponding OSPF		Sub-Type and value fields are as defined in corresponding OSPF
	[I-D.ietf-ospf-segment-routing-msd] and IS-IS		[I-D.ietf-ospf-segment-routing-msd] and IS-IS
	[I-D.ietf-isis-segment-routing-msd] extensions.		[I-D.ietf-isis-segment-routing-msd] extensions.
	skipping to change at page 4, line 46 ¶		skipping to change at page 4, line 43 ¶
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length |		| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sub-Type and Value ...		| Sub-Type and Value ...
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
	Figure 2: Link attribute format		Figure 2: Link attribute format
	Type : A 2-octet field specifiying code-point of the new TLV type.		Type : A 2-octet field specifying code-point of the new TLV type.
	Code-point:(TBD2) from BGP-LS Node Descriptor, Link Descriptor,		Code-point:(TBD2) from BGP-LS Node Descriptor, Link Descriptor,
	Prefix Descriptor, and Attribute TLVs registry		Prefix Descriptor, and Attribute TLVs registry
	Length: A 2-octet field that indicates the length of the value		Length: A 2-octet field that indicates the length of the value
	portion		portion
	Sub-Type and value fields are as defined in corresponding OSPF		Sub-Type and value fields are as defined in corresponding OSPF
	[I-D.ietf-ospf-segment-routing-msd] and IS-IS		[I-D.ietf-ospf-segment-routing-msd] and IS-IS
	[I-D.ietf-isis-segment-routing-msd] extensions.		[I-D.ietf-isis-segment-routing-msd] extensions.
			Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	5. IANA Considerations		5. IANA Considerations
	We request IANA assign code points from the registry BGP-LS Node		We request IANA assign code points from the registry BGP-LS Node
	Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs,		Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs,
	as follows: TLV Code Point Description IS-IS TLV/Sub-TLV Reference		as follows: TLV Code Point Description IS-IS TLV/Sub-TLV Reference
	TBD1 Node MSD 242/23 (this document) TBD2 Link MSD		TBD1 Node MSD 242/23 (this document) TBD2 Link MSD
	(22,23,25,141,222,223)/15 (this document)		(22,23,25,141,222,223)/15 (this document)
	6. Security Considerations		6. Security Considerations
			Advertisement of the additional information defined in this document
			that is false, e.g., an MSD that is incorrect, may result in a path
			computation failing, having a service unavailable, or instantiation
			of a path that can't be supported by the head-end (the node
			performing the imposition).
	This document does not introduce security issues beyond those		This document does not introduce security issues beyond those
	discussed in [RFC7752]		discussed in [RFC7752], [I-D.ietf-ospf-segment-routing-msd] and
			[I-D.ietf-isis-segment-routing-msd]
	7. Acknowledgements		7. Acknowledgements
	We like to thank Nikos Triantafillis, Stephane Litkowski and Bruno		We like to thank Nikos Triantafillis, Acee Lindem, Ketan Talaulikar,
	Decraene for their reviews and valuable comments.		Stephane Litkowski and Bruno Decraene for their reviews and valuable
			comments.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[I-D.ietf-isis-segment-routing-msd]		[I-D.ietf-isis-segment-routing-msd]
	Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,		Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
	"Signaling MSD (Maximum SID Depth) using IS-IS", draft-		"Signaling MSD (Maximum SID Depth) using IS-IS", draft-
	ietf-isis-segment-routing-msd-04 (work in progress), June		ietf-isis-segment-routing-msd-13 (work in progress), July
	2017.		2018.
	[I-D.ietf-ospf-segment-routing-msd]		[I-D.ietf-ospf-segment-routing-msd]
	Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,		Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
	"Signaling MSD (Maximum SID Depth) using OSPF", draft-		"Signaling MSD (Maximum SID Depth) using OSPF", draft-
	ietf-ospf-segment-routing-msd-05 (work in progress), June		ietf-ospf-segment-routing-msd-15 (work in progress), July
	2017.		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-10 (work in progress),		draft-ietf-pce-segment-routing-12 (work in progress), June
	October 2017.		2018.
			Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	[I-D.ietf-spring-segment-routing-mpls]		[I-D.ietf-spring-segment-routing-mpls]
	Filsfils, C., Previdi, S., Bashandy, A., 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-10		data plane", draft-ietf-spring-segment-routing-mpls-14
	(work in progress), June 2017.		(work in progress), June 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>.
	[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>.
			[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	8.2. Informative References		8.2. Informative References
			[I-D.ietf-isis-mpls-elc]
			Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
			Litkowski, "Signaling Entropy Label Capability and Entropy
			Readable Label Depth Using IS-IS", draft-ietf-isis-mpls-
			elc-05 (work in progress), July 2018.
	[I-D.ietf-isis-segment-routing-extensions]		[I-D.ietf-isis-segment-routing-extensions]
	Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,		Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
	Litkowski, S., Decraene, B., and j. jefftant@gmail.com,		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-13 (work in progress), June		segment-routing-extensions-19 (work in progress), July
	2017.		2018.
			[I-D.ietf-ospf-mpls-elc]
			Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
			Litkowski, "Signaling Entropy Label Capability and Entropy
			Readable Label-stack Depth Using OSPF", draft-ietf-ospf-
			mpls-elc-06 (work in progress), August 2018.
	[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-19 (work in progress), August 2017.		routing-extensions-25 (work in progress), April 2018.
			Internet-DrafSignaling MSD (Maximum SID Depth) using BGP-LS August 2018
	Authors' Addresses		Authors' Addresses
	Jeff Tantsura		Jeff Tantsura
	Individual		Nuage Networks
	Email: jefftant.ietf@gmail.com		Email: jefftant.ietf@gmail.com
	Uma Chunduri		Uma Chunduri
	Huawei Technologies		Huawei USA
	Email: uma.chunduri@huawei.com		Email: uma.chunduri@huawei.com
	Greg Mirsky		Greg Mirsky
	ZTE Corp.		ZTE Corp.
	Email: gregimirsky@gmail.com		Email: gregimirsky@gmail.com
	Siva Sivabalan		Siva Sivabalan
	Cisco		Cisco
	Email: msiva@cisco.com		Email: msiva@cisco.com
End of changes. 33 change blocks.
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