< draft-tantsura-bgp-ls-segment-routing-msd-00.txt		draft-tantsura-bgp-ls-segment-routing-msd-01.txt >
	IDR Working Group J. Tantsura		IDR Working Group J. Tantsura
	Internet-Draft G. Mirsky		Internet-Draft G. Mirsky
	Intended status: Standards Track Ericsson		Intended status: Standards Track Ericsson
	Expires: January 7, 2016 July 6, 2015		Expires: July 11, 2016 S. Sivabalan
			Cisco
			G. Mirsky
			Ericsson
			January 8, 2016
	Signaling Maximum SID Depth using Border Gateway Protocol Link-State		Signaling Maximum SID Depth using Border Gateway Protocol Link-State
	draft-tantsura-bgp-ls-segment-routing-msd-00		draft-tantsura-bgp-ls-segment-routing-msd-01
	Abstract		Abstract
	This document discusses use of BGP-LS to expose node and/or link on a		This document discusses use of BGP-LS to expose node and/or link on a
	node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN).		node MSD "Maximum SID Depth" to a centralized controller (PCE/SDN).
	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.
	skipping to change at page 1, line 31 ¶		skipping to change at page 1, line 35 ¶
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 January 7, 2016.		This Internet-Draft will expire on July 11, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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
	skipping to change at page 2, line 27 ¶		skipping to change at page 2, line 29 ¶
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
	8.1. Normative References . . . . . . . . . . . . . . . . . . 4		8.1. Normative References . . . . . . . . . . . . . . . . . . 4
	8.2. Informative References . . . . . . . . . . . . . . . . . 5		8.2. Informative References . . . . . . . . . . . . . . . . . 5
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
	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 crucial that the controller knows MSD "Maximum SID		controller, it is crucial that the controller knows MSD "Maximum SID
	Depth" of the node or link SR tunnel exits over, so it doesn't		Depth" of the node or link SR tunnel exits over, so it doesn't
	download a path with SID (label stack) of depth more than the node or		download a path with SID (label stack) of a depth more than the node
	link configured is capable of imposing.This document describes how to		or link configured is capable of imposing.This document describes how
	use BGP-LS to expose the MSD of the node or link configured to a		to use BGP-LS to expose the MSD of the node or link configured to a
	centralized controller.		centralized controller.
	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 22 ¶		skipping to change at page 3, line 22 ¶
	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.		the node/link configured.
	3. MSD supported by a node		3. MSD supported by a node
	Node MSD is a number in the range of 0-254. 0 represents lack of		Node MSD is a number in the range of 0-254. The vaule of 0
	ability to push MSD of any depth, any other value represents that of		represents lack of ability to push MSD of any depth, any other value
	the node.		represents that of the node.
	Node MSD is encoded in the Opaque Node Attribute TLV, as defined in		Node MSD is encoded in the Opaque Node Attribute TLV, as defined in
	[I-D.ietf-idr-ls-distribution]		[I-D.ietf-idr-ls-distribution]
	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 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// Opaque node attributes (variable) //		// Opaque node attributes (variable) //
	skipping to change at page 4, line 34 ¶		skipping to change at page 4, line 34 ¶
	We like to thank Nikos Triantafillis for the valuable comments.		We like to thank Nikos Triantafillis for the valuable comments.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[I-D.ietf-idr-ls-distribution]		[I-D.ietf-idr-ls-distribution]
	Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.		Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
	Ray, "North-Bound Distribution of Link-State and TE		Ray, "North-Bound Distribution of Link-State and TE
	Information using BGP", draft-ietf-idr-ls-distribution-11		Information using BGP", draft-ietf-idr-ls-distribution-13
	(work in progress), June 2015.		(work in progress), October 2015.
	[I-D.ietf-pce-segment-routing]		[I-D.ietf-pce-segment-routing]
	Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,		Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
	Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,		Lopez, V., Tantsura, J., Henderickx, W., and J. Hardwick,
	"PCEP Extensions for Segment Routing", draft-ietf-pce-		"PCEP Extensions for Segment Routing", draft-ietf-pce-
	segment-routing-05 (work in progress), May 2015.		segment-routing-06 (work in progress), August 2015.
	[I-D.ietf-spring-segment-routing-mpls]		[I-D.ietf-spring-segment-routing-mpls]
	Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,		Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
	Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,		Litkowski, S., Horneffer, M., rjs@rob.sh, r., Tantsura,
	and E. Crabbe, "Segment Routing with MPLS data plane",		J., and E. Crabbe, "Segment Routing with MPLS data plane",
	draft-ietf-spring-segment-routing-mpls-01 (work in		draft-ietf-spring-segment-routing-mpls-02 (work in
	progress), May 2015.		progress), October 2015.
	[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, March 1997.		Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<http://www.rfc-editor.org/info/rfc2119>.
	8.2. Informative References		8.2. Informative References
	[I-D.ietf-isis-segment-routing-extensions]		[I-D.ietf-isis-segment-routing-extensions]
	Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,		Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
	Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS		Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
	Extensions for Segment Routing", draft-ietf-isis-segment-		Extensions for Segment Routing", draft-ietf-isis-segment-
	routing-extensions-05 (work in progress), June 2015.		routing-extensions-06 (work in progress), December 2015.
	[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-05 (work in progress), June 2015.		routing-extensions-06 (work in progress), December 2015.
	Authors' Addresses		Authors' Addresses
	Jeff Tantsura		Jeff Tantsura
	Ericsson		Ericsson
	Email: jeff.tantsura@ericsson.com		Email: jeff.tantsura@ericsson.com
	Greg Mirsky		Greg Mirsky
	Ericsson		Ericsson
	Email: gregory.mirsky@ericsson.com		Email: gregory.mirsky@ericsson.com
			Siva Sivabalan
			Cisco
			Email: msiva@cisco.com
			Greg Mirsky
			Ericsson
			Email: gregory.mirsky@ericsson.com
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