< draft-ietf-isis-segment-routing-msd-14.txt		draft-ietf-isis-segment-routing-msd-15.txt >
	IS-IS Working Group J. Tantsura		IS-IS Working Group J. Tantsura
	Internet-Draft Nuage Networks		Internet-Draft Nuage Networks
	Intended status: Standards Track U. Chunduri		Intended status: Standards Track U. Chunduri
	Expires: February 20, 2019 Huawei Technologies		Expires: March 2, 2019 Huawei Technologies
	S. Aldrin		S. Aldrin
	Google, Inc		Google, Inc
	L. Ginsberg		L. Ginsberg
	Cisco Systems		Cisco Systems
	August 19, 2018		August 29, 2018
	Signaling MSD (Maximum SID Depth) using IS-IS		Signaling MSD (Maximum SID Depth) using IS-IS
	draft-ietf-isis-segment-routing-msd-14		draft-ietf-isis-segment-routing-msd-15
	Abstract		Abstract
	This document defines a way for an Intermediate System to		This document defines a way for an Intermediate System to
	Intermediate System (IS-IS) Router to advertise multiple types of		Intermediate System (IS-IS) Router to advertise multiple types of
	supported Maximum SID Depths (MSDs) at node and/or link granularity.		supported Maximum SID Depths (MSDs) at node and/or link granularity.
	Such advertisements allow entities (e.g., centralized controllers) to		Such advertisements allow entities (e.g., centralized controllers) to
	determine whether a particular SID stack can be supported in a given		determine whether a particular SID stack can be supported in a given
	network. This document only defines one type of MSD maximum label		network. This document only defines one type of MSD maximum label
	imposition, but defines an encoding that can support other MSD types.		imposition, but defines an encoding that can support other MSD types.
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	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 February 20, 2019.		This Internet-Draft will expire on March 2, 2019.
	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 19 ¶		skipping to change at page 2, line 19 ¶
	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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3		1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 3		2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 3
	3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4		3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
	4. Using Node and Link MSD Advertisements . . . . . . . . . . . 5		4. Procedures for using Node and Link MSD Advertisements . . . . 5
	5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6		5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7		8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
	10.1. Normative References . . . . . . . . . . . . . . . . . . 8		10.1. Normative References . . . . . . . . . . . . . . . . . . 8
	10.2. Informative References . . . . . . . . . . . . . . . . . 8		10.2. Informative References . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	skipping to change at page 4, line 42 ¶		skipping to change at page 4, line 42 ¶
	represents lack of the ability to support SID stack of any depth; any		represents lack of the ability to support SID stack of any depth; any
	other value represents that of the node. This value MUST represent		other value represents that of the node. This value MUST represent
	the lowest value supported by any link configured for use by the		the lowest value supported by any link configured for use by the
	advertising IS-IS instance.		advertising IS-IS instance.
	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.
	If there exist multiple Node MSD advertisements for the same MSD-Type		If there exist multiple Node MSD advertisements for the same MSD-Type
	originated by the same router, the procedures defined in [RFC7981]		originated by the same router, the procedures defined in [RFC7981]
	apply.		apply. These procedures may result in different MSD values being
			used by (for example) different controllers - but this does not
			create any interoperability issue.
	3. Link MSD Advertisement		3. Link MSD Advertisement
	The link MSD sub-TLV is defined for TLVs 22, 23, 25, 141, 222, and		The link MSD sub-TLV is defined for TLVs 22, 23, 25, 141, 222, and
	223 to carry the MSD of the interface associated with the link. MSD		223 to carry the MSD of the interface associated with the link. MSD
	values may be learned via a hardware API or may be provisioned.		values may be learned via a hardware API or may be provisioned.
	0 1		0 1
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
	skipping to change at page 5, line 42 ¶		skipping to change at page 5, line 42 ¶
	represents lack of the ability to support SID stack of any depth; any		represents lack of the ability to support SID stack of any depth; any
	other value represents that of the link when used as an outgoing		other value represents that of the link when used as an outgoing
	link.		link.
	This sub-TLV is optional.		This sub-TLV is optional.
	If multiple Link MSD advertisements for the same MSD-Type and the		If multiple Link MSD advertisements for the same MSD-Type and the
	same link are received, the procedure used to select which copy is		same link are received, the procedure used to select which copy is
	used is undefined.		used is undefined.
	4. Using Node and Link MSD Advertisements		4. Procedures for using Node and Link MSD Advertisements
	When Link MSD is present for a given MSD type, the value of the Link		When Link MSD is present for a given MSD type, the value of the Link
	MSD MUST take preference over the Node MSD. When a Link MSD type is		MSD MUST take preference over the Node MSD. When a Link MSD type is
	not signaled but the Node MSD type is, then the Node MSD type value		not signaled but the Node MSD type is, then the Node MSD type value
	MUST be considered as the MSD value for that link.		MUST be considered as the MSD value for that link.
	In order to increase flooding efficiency, it is RECOMMENDED that		In order to increase flooding efficiency, it is RECOMMENDED that
	routers with homogenous link MSD values advertise just the Node MSD		routers with homogenous link MSD values advertise just the Node MSD
	value.		value.
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	for a given MSD type is specific to the MSD type. Generally it can		for a given MSD type is specific to the MSD type. Generally it can
	only be inferred that the advertising node does not support		only be inferred that the advertising node does not support
	advertisement of that MSD type. However, in some cases the lack of		advertisement of that MSD type. However, in some cases the lack of
	advertisement might imply that the functionality associated with the		advertisement might imply that the functionality associated with the
	MSD type is not supported. The correct interpretation MUST be		MSD type is not supported. The correct interpretation MUST be
	specified when an MSD type is defined.		specified when an MSD type is defined.
	5. Base MPLS Imposition MSD		5. Base MPLS Imposition MSD
	Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS		Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS
	labels a node is capable of imposing, including all		labels which can be imposed, including all service/transport/special
	service/transport/special labels.		labels.
	Absence of BMI-MSD advertisements indicates solely that the		Absence of BMI-MSD advertisements indicates solely that the
	advertising node does not support advertisement of this capability.		advertising node does not support advertisement of this capability.
	6. IANA Considerations		6. IANA Considerations
	This document requests IANA to allocate a sub-TLV type for the new		This document requests IANA to allocate a sub-TLV type for the new
	sub TLV proposed in Section 2 of this document from IS-IS Router		sub TLV proposed in Section 2 of this document from IS-IS Router
	Capability TLV Registry as defined by [RFC7981].		Capability TLV Registry as defined by [RFC7981].
	skipping to change at page 7, line 29 ¶		skipping to change at page 7, line 29 ¶
	Value Name Reference		Value Name Reference
	----- --------------------- -------------		----- --------------------- -------------
	0 Reserved This document		0 Reserved This document
	1 Base MPLS Imposition 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 Types Codepoints Registry		Figure 6: MSD Types Codepoints Registry
	Guidance for the Designated Experts is as defined in [RFC7370]		General guidance for the Designated Experts is as defined in
			[RFC7370]
	7. 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.
	Advertisement of the additional information defined in this document		Advertisement of the additional information defined in this document
	that is false, e.g., an MSD that is incorrect, may result in a path		that is false, e.g., an MSD that is incorrect, may result in a path
	computation failing, having a service unavailable, or instantiation		computation failing, having a service unavailable, or instantiation
	of a path that can't be supported by the head-end (the node		of a path that can't be supported by the head-end (the node
End of changes. 9 change blocks.
	10 lines changed or deleted		13 lines changed or added
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