< draft-ietf-ospf-segment-routing-msd-03.txt		draft-ietf-ospf-segment-routing-msd-04.txt >
	skipping to change at page 1, line 14 ¶		skipping to change at page 1, line 14 ¶
	Internet-Draft Individual		Internet-Draft Individual
	Intended status: Standards Track U. Chunduri		Intended status: Standards Track U. Chunduri
	Expires: September 29, 2017 Huawei Technologies		Expires: September 29, 2017 Huawei Technologies
	S. Aldrin		S. Aldrin
	Google, Inc		Google, Inc
	P. Psenak		P. Psenak
	Cisco Systems		Cisco Systems
	March 28, 2017		March 28, 2017
	Signaling MSD (Maximum SID Depth) using OSPF		Signaling MSD (Maximum SID Depth) using OSPF
	draft-ietf-ospf-segment-routing-msd-03		draft-ietf-ospf-segment-routing-msd-04
	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 push the SID stack
	of an appropriate depth. MSD is relevant to the head-end of a SR		of an appropriate depth. MSD is relevant to the head-end of a SR
	tunnel or Binding-SID anchor node where Binding-SID expansions might		tunnel or Binding-SID anchor node where Binding-SID expansions might
	skipping to change at page 3, line 14 ¶		skipping to change at page 3, line 14 ¶
	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 push SID's stack of a particular depth.
	MSD of type 1 (IANA Registry) is used to signal the total number of		MSD of type 1 (IANA Registry), called Base MSD is used to signal the
	SIDs a node is capable of imposing, to be used by a path computation		total number of SIDs a node is capable of imposing, to be used by a
	element/controller. In case, there are additional labels (e.g.		path computation element/controller. In case, there are additional
	service) that are to be pushed to the stack - this would be signaled		labels (e.g. service) that are to be pushed to the stack - this would
	with an another MSD type (TBD), MSD SHOULD be adjusted to reflect		be signaled with an another MSD type (TBD), MSD SHOULD be adjusted to
	that. In the future, new MSD types could be defined to signal		reflect that. In the future, new MSD types could be defined to
	additional capabilities: entropy labels, labels that can be pushed		signal additional capabilities: entropy labels, labels that can be
	thru recirculation, or another dataplane e.g IPv6.		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
	OSPF: Open Shortest Path First		OSPF: Open Shortest Path First
	skipping to change at page 6, line 21 ¶		skipping to change at page 6, line 21 ¶
	proposed in Section 4 from OSPFv2 Extended Link Opaque LSAs Extended		proposed in Section 4 from OSPFv2 Extended Link Opaque LSAs Extended
	Link TLV registry and from Router-Link TLV defined in OSPFv3 Extend-		Link TLV registry and from Router-Link TLV defined in OSPFv3 Extend-
	LSA Sub-TLV registry.		LSA Sub-TLV registry.
	This document also request IANA to create a new Sub-type registry as		This document also request IANA to create a new Sub-type registry as
	proposed in Section 3, Section 4.		proposed in Section 3, Section 4.
	Value Name Reference		Value Name Reference
	----- --------------------- -------------		----- --------------------- -------------
	0 Reserved This document		0 Reserved This document
	1 MSD This document		1 Base 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 3: MSD Sub-type Codepoints Registry		Figure 3: MSD Sub-type Codepoints Registry
	7. Security Considerations		7. Security Considerations
	This document describes a mechanism to signal Segment Routing MSD		This document describes a mechanism to signal Segment Routing MSD
	supported at node and/or link granularity through OSPF LSA's and does		supported at node and/or link granularity through OSPF LSA's and does
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