< draft-ietf-ospf-segment-routing-msd-05.txt		draft-ietf-ospf-segment-routing-msd-06.txt >
	OSPF Working Group J. Tantsura		OSPF Working Group J. Tantsura
	Internet-Draft Individual		Internet-Draft Individual
	Intended status: Standards Track U. Chunduri		Intended status: Standards Track U. Chunduri
	Expires: December 6, 2017 Huawei Technologies		Expires: June 4, 2018 Huawei Technologies
	S. Aldrin		S. Aldrin
	Google, Inc		Google, Inc
	P. Psenak		P. Psenak
	Cisco Systems		Cisco Systems
	June 04, 2017		December 01, 2017
	Signaling MSD (Maximum SID Depth) using OSPF		Signaling MSD (Maximum SID Depth) using OSPF
	draft-ietf-ospf-segment-routing-msd-05		draft-ietf-ospf-segment-routing-msd-06
	Abstract		Abstract
	This document proposes a way to signal Maximum SID Depth (MSD)		This document proposes a way to signal Maximum SID Depth (MSD)
	supported by a node at node and/or link granularity by an OSPF		supported by a node at node and/or link granularity by an OSPF
	Router. In a Segment Routing (SR) enabled network a centralized		Router. In a Segment Routing (SR) enabled network a centralized
	controller that programs SR tunnels needs to know the MSD supported		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		by the head-end at node and/or link granularity to impose the SID
	of an appropriate depth. MSD is relevant to the head-end of a SR		stack of an appropriate depth. MSD is relevant to the head-end of a
	tunnel or Binding-SID anchor node where Binding-SID expansions might		SR tunnel or Binding-SID anchor node where Binding-SID expansions
	result in creation of a new SID stack. Here the term OSPF means both		might result in creation of a new SID stack. Here the term OSPF
	OSPFv2 and OSPFv3.		means both OSPFv2 and OSPFv3.
	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 http://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 6, 2017.		This Internet-Draft will expire on June 4, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 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		(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
	1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3		1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Node MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 4		3. Node MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 4
	4. LINK MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5		4. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5
	5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5		5. Node MSD vs Link MSD conflict resolution . . . . . . . . . . 5
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 6		7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6		8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6		9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
	10.1. Normative References . . . . . . . . . . . . . . . . . . 7		10.1. Normative References . . . . . . . . . . . . . . . . . . 7
	10.2. Informative References . . . . . . . . . . . . . . . . . 7		10.2. Informative References . . . . . . . . . . . . . . . . . 7
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	skipping to change at page 2, line 51 ¶		skipping to change at page 2, line 51 ¶
	OSPF to signal the MSD of a node or link to a centralized controller.		OSPF 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.tantsura-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
	the all nodes and links in the network MSD is relevant, MSD		the all nodes and links in the network MSD is relevant, MSD
	capabilites SHOULD be distributed to every OSPF router in the		capabilites SHOULD be distributed to every OSPF router in the
	network.		network.
	[I-D.ietf-ospf-mpls-elc] defines Readable Label Depth Capability		[I-D.ietf-ospf-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. MSD in
	contrary signals ability to push SID's stack of a particular depth.		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		MSD of type 1 (IANA Registry), called Base MSD is used to signal the
	total number of SIDs a node is capable of imposing, to be used by a		total number of SIDs a node is capable of imposing, to be used by a
	path computation element/controller. In case, there are additional		path computation element/controller. In case, there are additional
	labels (e.g. service) that are to be pushed to the stack - this would		SIDs (e.g. service) that are to be imposed to the stack - this would
	be signaled with an another MSD type (TBD), no adjustment to the Base		be signaled with an another MSD type (TBD), no adjustment to the Base
	MSD should be made. In the future, new MSD types could be defined to		MSD should be made. In the future, new MSD types could be defined to
	signal additional capabilities: entropy labels, labels that can be		signal additional capabilities: entropy labels, SIDs that can be
	pushed thru recirculation, or 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
	OSPF: Open Shortest Path First		OSPF: Open Shortest Path First
	skipping to change at page 4, line 27 ¶		skipping to change at page 4, line 27 ¶
	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 MSD TLV		Figure 1: Node MSD TLV
	The Type (2 bytes) of this TLV is 12 (Suggested value - to be		The Type (2 bytes) of this TLV has value of 12.
	assigned by IANA).
	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 a 1 octet sub-type (IANA Registry) and 1
	octet value.		octet value.
	Sub-Type 1 (IANA Section), MSD and the Value field contains maximum		Sub-Type 1 (IANA Section), MSD and the Value field contains maximum
	MSD of the router originating the RI LSA. Node Maximum MSD is a		MSD of the router originating the RI LSA. Node Maximum MSD is a
	number in the range of 0-254. 0 represents lack of the ability to		number in the range of 0-254. 0 represents lack of the ability to
	push MSD of any depth; any other value represents that of the node.		impose MSD stack of any depth; any other value represents that of the
	This value SHOULD represent the lowest value supported by node.		node. This value SHOULD represent the lowest value supported by
			node.
	Other Sub-types other than defined above are reserved for future		Other Sub-types other than defined above are reserved for future
	extensions.		extensions.
	This TLV is applicable to OSPFv2 and to OSPFv3 [RFC5838] and is		This TLV is applicable to OSPFv2 and to OSPFv3 [RFC5838] and is
	optional. The scope of the advertisement is specific to the		optional. The scope of the advertisement is specific to the
	deployment.		deployment.
	4. LINK MSD sub-TLV		4. Link MSD sub-TLV
	A new sub-TLV called Link MSD sub-TLV is defined to carry the		A new sub-TLV called Link MSD sub-TLV is defined to carry the
	provisioned SID depth of the interface associated with the link.		provisioned SID depth of the interface associated with the link.
	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 MSD Sub-TLV		Figure 2: Link MSD Sub-TLV
	The Type (2 bytes) of this TLV:		The Type (2 bytes) of this TLV:
	For OSPFv2, the Link level MSD value is advertised as an optional		For OSPFv2, the Link level MSD value is advertised as an optional
	Sub-TLV of OSPFv2 Extended Link TLV as defined in [RFC7684], and the		Sub-TLV of OSPFv2 Extended Link TLV as defined in [RFC7684], and has
	value is 5 (Suggested value - to be assigned by IANA)		value of 6.
	For OSPFv3, the Link level MSD value is advertised as an optional		For OSPFv3, the Link level MSD value is advertised as an optional
	Sub-TLV of the Router-Link TLV as defined in		Sub-TLV of the Router-Link TLV as defined in
	[I-D.ietf-ospf-ospfv3-lsa-extend], and the value is 3 (Suggested		[I-D.ietf-ospf-ospfv3-lsa-extend], and has value of 3 (Suggested
	value - to be assigned by IANA).		value - to be assigned by IANA).
	Length is variable and similar to what is defined in Section 3.		Length is variable and similar to what is defined in Section 3.
	Value field consists of a 1 octet sub-type (IANA Registry) and 1		Value field consists of a 1 octet sub-type (IANA Registry) and 1
	octet value.		octet value.
	Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD		Sub-Type 1 (IANA Section), MSD and the Value field contains Link MSD
	of the router originating the corresponding LSA as specified for		of the router originating the corresponding LSA as specified for
	OSPFv2 and OSPFv3. Link MSD is a number in the range of 0-254. 0		OSPFv2 and OSPFv3. Link MSD is a number in the range of 0-254. 0
	represents lack of the ability to push MSD of any depth; any other		represents lack of the ability to impose MSD stack of any depth; any
	value represents that of the particular link MSD value.		other value represents that of the particular link MSD value.
	Other Sub-types other than defined above are reserved for future		Other Sub-types other than defined above are reserved for future
	extensions.		extensions.
	5. Node MSD vs Link MSD conflict resolution		5. Node MSD vs Link MSD conflict resolution
	When both Node MSD and Link MSD are present, the value in the Link		When both Node MSD and Link MSD are present, the value in the Link
	MSD MUST be used.		MSD MUST be used.
	6. IANA Considerations		6. IANA Considerations
	skipping to change at page 7, line 9 ¶		skipping to change at page 7, line 9 ¶
	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.
	10. References		10. References
	10.1. 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,
	<http://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and		[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
	S. Shaffer, "Extensions to OSPF for Advertising Optional		S. Shaffer, "Extensions to OSPF for Advertising Optional
	Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July		Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
	2007, <http://www.rfc-editor.org/info/rfc4970>.		2007, <https://www.rfc-editor.org/info/rfc4970>.
	10.2. Informative References		10.2. Informative References
			[I-D.ietf-idr-bgp-ls-segment-routing-msd]
			Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
			"Signaling Maximum SID Depth using Border Gateway Protocol
			Link-State", draft-ietf-idr-bgp-ls-segment-routing-msd-01
			(work in progress), October 2017.
	[I-D.ietf-ospf-mpls-elc]		[I-D.ietf-ospf-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 Using		Litkowski, "Signaling Entropy Label Capability Using
	OSPF", draft-ietf-ospf-mpls-elc-04 (work in progress),		OSPF", draft-ietf-ospf-mpls-elc-04 (work in progress),
	November 2016.		November 2016.
	[I-D.ietf-ospf-ospfv3-lsa-extend]		[I-D.ietf-ospf-ospfv3-lsa-extend]
	Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.		Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
	Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-		Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
	lsa-extend-14 (work in progress), April 2017.		lsa-extend-18 (work in progress), November 2017.
	[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-09 (work in progress),		draft-ietf-pce-segment-routing-11 (work in progress),
	April 2017.		November 2017.
	[I-D.tantsura-idr-bgp-ls-segment-routing-msd]
	Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
	"Signaling Maximum SID Depth using Border Gateway Protocol
	Link-State", draft-tantsura-idr-bgp-ls-segment-routing-
	msd-04 (work in progress), March 2017.
	[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and		[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
	R. Aggarwal, "Support of Address Families in OSPFv3",		R. Aggarwal, "Support of Address Families in OSPFv3",
	RFC 5838, DOI 10.17487/RFC5838, April 2010,		RFC 5838, DOI 10.17487/RFC5838, April 2010,
	<http://www.rfc-editor.org/info/rfc5838>.		<https://www.rfc-editor.org/info/rfc5838>.
	[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, <http://www.rfc-editor.org/info/rfc7684>.		2015, <https://www.rfc-editor.org/info/rfc7684>.
	[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,
	<http://www.rfc-editor.org/info/rfc7752>.		<https://www.rfc-editor.org/info/rfc7752>.
	Authors' Addresses		Authors' Addresses
	Jeff Tantsura		Jeff Tantsura
	Individual		Individual
	Email: jefftant.ietf@gmail.com		Email: jefftant.ietf@gmail.com
	Uma Chunduri		Uma Chunduri
	Huawei Technologies		Huawei Technologies
End of changes. 26 change blocks.
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