draft-ietf-lsr-isis-area-proxy-04.txt		draft-ietf-lsr-isis-area-proxy-05.txt
	Internet Engineering Task Force T. Li		Internet Engineering Task Force T. Li
	Internet-Draft S. Chen		Internet-Draft S. Chen
	Intended status: Experimental V. Ilangovan		Intended status: Experimental V. Ilangovan
	Expires: March 6, 2021 Arista Networks		Expires: May 22, 2021 Arista Networks
	G. Mishra		G. Mishra
	Verizon Inc.		Verizon Inc.
	September 2, 2020		November 18, 2020
	Area Proxy for IS-IS		Area Proxy for IS-IS
	draft-ietf-lsr-isis-area-proxy-04		draft-ietf-lsr-isis-area-proxy-05
	Abstract		Abstract
	Link state routing protocols have hierarchical abstraction already		Link state routing protocols have hierarchical abstraction already
	built into them. However, when lower levels are used for transit,		built into them. However, when lower levels are used for transit,
	they must expose their internal topologies to each other, leading to		they must expose their internal topologies to each other, leading to
	scale issues.		scale issues.
	To avoid this, this document discusses extensions to the IS-IS		To avoid this, this document discusses extensions to the IS-IS
	routing protocol that would allow level 1 areas to provide transit,		routing protocol that would allow level 1 areas to provide transit,
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	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 March 6, 2021.		This Internet-Draft will expire on May 22, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 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 5, line 5 ¶		skipping to change at page 5, line 5 ¶
	There are four classes of routers that we need to be concerned with		There are four classes of routers that we need to be concerned with
	in this discussion:		in this discussion:
	Inside Router A router within the Inside Area that runs Level 1 and		Inside Router A router within the Inside Area that runs Level 1 and
	Level 2 IS-IS. A router is recognized as an Inside Router by the		Level 2 IS-IS. A router is recognized as an Inside Router by the
	existence of its LSP in the Level 1 LSDB.		existence of its LSP in the Level 1 LSDB.
	Area Leader The Area Leader is an Inside Router that is elected to		Area Leader The Area Leader is an Inside Router that is elected to
	represent the Level 1 area by injecting the Proxy LSP into the		represent the Level 1 area by injecting the Proxy LSP into the
	Level 2 LSDB. There may be multiple candidates for Area Leader,		Level 2 LSDB. There may be multiple candidates for Area Leader,
	but only one is elected at a given time. Any Inisde Router can be		but only one is elected at a given time. Any Inside Router can be
	Area Leader.		Area Leader.
	Inside Edge Router An Inside Edge Router is an Inside Area Router		Inside Edge Router An Inside Edge Router is an Inside Area Router
	that has at least one Level 2 interface outside of the Inside		that has at least one Level 2 interface outside of the Inside
	Area. An interface on an Inside Edge Router that is connected to		Area. An interface on an Inside Edge Router that is connected to
	an Outside Edge Router is an Area Proxy Boundary.		an Outside Edge Router is an Area Proxy Boundary.
	Outside Edge Router An Outside Edge Router is a Level 2 router that		Outside Edge Router An Outside Edge Router is a Level 2 router that
	is outside of the Inside Area that has an adjacency with an Inside		is outside of the Inside Area that has an adjacency with an Inside
	Edge Router.		Edge Router.
	skipping to change at page 5, line 38 ¶		skipping to change at page 5, line 38 ¶
	+--------+ || | Outside |		+--------+ || | Outside |
	|| | Edge |		|| | Edge |
	|| | Router |		|| | Router |
	|| +---------+		|| +---------+
	Outside Area		Outside Area
	An example of router classes		An example of router classes
	All Inside Edge Routers learn the Area Proxy System Identifier from		All Inside Edge Routers learn the Area Proxy System Identifier from
	the Level 1 LSDB and use that as the system identifier in their Level		the Area Proxy TLV advertised by the Area Leader and use that as the
	2 IS-IS Hello PDUs (IIHs) on all Outside interfaces. Outside Edge		system identifier in their Level 2 IS-IS Hello PDUs (IIHs) on all
	Routers should then advertise an adjacency to the Area Proxy System		Outside interfaces. Outside Edge Routers should then advertise an
	Identifier. This allows all Outside Routers to use the Proxy LSP in		adjacency to the Area Proxy System Identifier. This allows all
	their SPF computations without seeing the full topology of the Inside		Outside Routers to use the Proxy LSP in their SPF computations
	Area.		without seeing the full topology of the Inside Area.
	Area Proxy functionality assumes that all circuits on Inside Routers		Area Proxy functionality assumes that all circuits on Inside Routers
	are either Level 1-2 circuits within the Inside Area, or Level 2		are either Level 1-2 circuits within the Inside Area, or Level 2
	circuits between Outside Edge Routers and Inside Edge Routers.		circuits between Outside Edge Routers and Inside Edge Routers.
	Area Proxy Boundary multi-access circuits (i.e. Ethernets in LAN		Area Proxy Boundary multi-access circuits (i.e. Ethernets in LAN
	mode) with multiple Inside Edge Routers on them are not supported.		mode) with multiple Inside Edge Routers on them are not supported.
	The Inside Edge Router on any boundary LAN MUST NOT flood Inside		The Inside Edge Router on any boundary LAN MUST NOT flood Inside
	Router LSPs on this link. Boundary LANs SHOULD NOT be enabled for		Router LSPs on this link. Boundary LANs SHOULD NOT be enabled for
	skipping to change at page 6, line 46 ¶		skipping to change at page 6, line 46 ¶
	Area Proxy TLV (Section 4.3.2). The Inside Edge Nodes MUST establish		Area Proxy TLV (Section 4.3.2). The Inside Edge Nodes MUST establish
	forwarding based on this SID. The Area Leader SHALL also include the		forwarding based on this SID. The Area Leader SHALL also include the
	Area SID in the Proxy LSP so that the remainder of L2 can use it for		Area SID in the Proxy LSP so that the remainder of L2 can use it for
	path construction. (Section 4.4.13).		path construction. (Section 4.4.13).
	3. Inside Router Functions		3. Inside Router Functions
	All Inside Routers run Level 1-2 IS-IS and must be explicitly		All Inside Routers run Level 1-2 IS-IS and must be explicitly
	instructed to enable the Area Proxy functionality. To signal their		instructed to enable the Area Proxy functionality. To signal their
	readiness to participate in Area Proxy functionality, they will		readiness to participate in Area Proxy functionality, they will
	advertise the Area Proxy TLV.		advertise the Area Proxy TLV in their L2 LSP.
	3.1. The Area Proxy TLV		3.1. The Area Proxy TLV
	The Area Proxy TLV serves multiple functions:		The Area Proxy TLV serves multiple functions:
	The presence of the Area Proxy TLV in a node's LSP indicates that		The presence of the Area Proxy TLV in a node's LSP indicates that
	the node is enabled for Area Proxy.		the node is enabled for Area Proxy.
	An LSP containing the Area Proxy TLV is also an Inside Node. All		An LSP containing the Area Proxy TLV is also an Inside Node. All
	Inside Nodes, including pseudonodes, MUST advertise the Area Proxy		Inside Nodes, including pseudonodes, MUST advertise the Area Proxy
	TLV.		TLV.
	It is a container for sub-TLVs with Area Proxy information.		It is a container for sub-TLVs with Area Proxy information.
	A node advertises the Area Proxy TLV in its L2 LSP. The Area Proxy		A node advertises the Area Proxy TLV in fragment 0 of its L2 LSP.
			Nodes MUST NOT advertise the Area Proxy TLV in a L1 LSP. Nodes MUST
			ignore the Area Proxy TLV if it is found in a L1 LSP. The Area Proxy
	TLV is not used in the Proxy LSP. The format of the Area Proxy TLV		TLV is not used in the Proxy LSP. The format of the Area Proxy TLV
	is:		is:
	0 1 2		0 1 2
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| TLV Type | TLV Length | Sub-TLVs ...		| TLV Type | TLV Length | Sub-TLVs ...
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	TLV Type: 20		TLV Type: 20
	skipping to change at page 8, line 11 ¶		skipping to change at page 8, line 11 ¶
	any intra-area metrics involved. However, if two paths have equal		any intra-area metrics involved. However, if two paths have equal
	inter-area metrics, then the intra-area metrics would be used to		inter-area metrics, then the intra-area metrics would be used to
	compare the paths.		compare the paths.
	Point-to-Point links between two Inside Routers are considered to be		Point-to-Point links between two Inside Routers are considered to be
	Inside Area links. LAN links which have a pseudonode LSP in the		Inside Area links. LAN links which have a pseudonode LSP in the
	Level 1 LSDB are considered to be Inside Area links.		Level 1 LSDB are considered to be Inside Area links.
	3.3. Responsibilities with respect to the Proxy LSP		3.3. Responsibilities with respect to the Proxy LSP
	The Area Leader will generate a Proxy LSP that must be flooded across		The Area Leader will generate a Proxy LSP that will be flooded across
	the Inside Area. Inside Routers MUST ignore the contents of the		the Inside Area. Inside Routers MUST ignore the contents of the
	Proxy LSP other than for flooding.		Proxy LSP other than for flooding. The Proxy LSP uses the Area Proxy
			System Identifier as its Source ID.
	4. Area Leader Functions		4. Area Leader Functions
	The Area Leader has several responsibilities. First, it MUST inject		The Area Leader has several responsibilities. First, it MUST inject
	the Area Proxy System Identifier into the Level 1 LSDB. Second, the		the Area Proxy System Identifier into the Level 2 LSDB. Second, the
	Area Leader MUST generate the Proxy LSP for the Inside Area.		Area Leader MUST generate the Proxy LSP for the Inside Area.
	4.1. Area Leader Election		4.1. Area Leader Election
	The Area Leader is selected using the election mechanisms and TLVs		The Area Leader is selected using the election mechanisms and TLVs
	described in Dynamic Flooding for IS-IS		described in Dynamic Flooding for IS-IS
	[I-D.ietf-lsr-dynamic-flooding].		[I-D.ietf-lsr-dynamic-flooding].
	4.2. Redundancy		4.2. Redundancy
	skipping to change at page 14, line 42 ¶		skipping to change at page 14, line 42 ¶
	4.4.13. The Area SID		4.4.13. The Area SID
	When SR is enabled, it may be useful to advertise an Area SID which		When SR is enabled, it may be useful to advertise an Area SID which
	will direct traffic to any of the Inside Edge Routers. The		will direct traffic to any of the Inside Edge Routers. The
	information for the Area SID is distributed to all Inside Edge		information for the Area SID is distributed to all Inside Edge
	Routers using the Area SID sub-TLV (Section 4.3.2) by the Area		Routers using the Area SID sub-TLV (Section 4.3.2) by the Area
	Leader.		Leader.
	The Area Leader SHOULD advertise the Area SID information in the		The Area Leader SHOULD advertise the Area SID information in the
	Proxy LSP as a Node SID as defined in [RFC8667] Section 2.1. The		Proxy LSP as a Node SID as defined in [RFC8667] Section 2.1. The
	advertisement in the Proxy LSP informs the remainder of the network		advertisement in the Proxy LSP informs the Outside Area that packets
	that packets directed to the SID will be forwarded by one of the		directed to the SID will be forwarded to one of the Inside Edge Nodes
	Inside Edge Nodes and the Area SID will be consumed.		and the Area SID will be consumed.
	Other uses of the Area SID and area SID prefix are outside the scope		Other uses of the Area SID and area SID prefix are outside the scope
	of this document. Documents which define other use cases for the		of this document. Documents which define other use cases for the
	Area SID MUST specify whether the SID value should be the same or		Area SID MUST specify whether the SID value should be the same or
	different from that used in support of Area Proxy.		different from that used in support of Area Proxy.
	5. Inside Edge Router Functions		5. Inside Edge Router Functions
	The Inside Edge Router has two additional and important functions.		The Inside Edge Router has two additional and important functions.
	First, it MUST generate IIHs that appear to have come from the Area		First, it MUST generate IIHs that appear to have come from the Area
	skipping to change at page 17, line 25 ¶		skipping to change at page 17, line 25 ¶
	[I-D.ietf-lsr-dynamic-flooding]		[I-D.ietf-lsr-dynamic-flooding]
	Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda,		Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda,
	T., Cooper, D., Jalil, L., Dontula, S., and G. Mishra,		T., Cooper, D., Jalil, L., Dontula, S., and G. Mishra,
	"Dynamic Flooding on Dense Graphs", draft-ietf-lsr-		"Dynamic Flooding on Dense Graphs", draft-ietf-lsr-
	dynamic-flooding-07 (work in progress), June 2020.		dynamic-flooding-07 (work in progress), June 2020.
	[I-D.ietf-lsr-isis-srv6-extensions]		[I-D.ietf-lsr-isis-srv6-extensions]
	Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and		Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
	Z. Hu, "IS-IS Extension to Support Segment Routing over		Z. Hu, "IS-IS Extension to Support Segment Routing over
	IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-08		IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-11
	(work in progress), April 2020.		(work in progress), October 2020.
	[ISO10589]		[ISO10589]
	International Organization for Standardization,		International Organization for Standardization,
	"Intermediate System to Intermediate System Intra-Domain		"Intermediate System to Intermediate System Intra-Domain
	Routing Exchange Protocol for use in Conjunction with the		Routing Exchange Protocol for use in Conjunction with the
	Protocol for Providing the Connectionless-mode Network		Protocol for Providing the Connectionless-mode Network
	Service (ISO 8473)", ISO/IEC 10589:2002, Nov. 2002.		Service (ISO 8473)", ISO/IEC 10589:2002, Nov. 2002.
	[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and		[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
	dual environments", RFC 1195, DOI 10.17487/RFC1195,		dual environments", RFC 1195, DOI 10.17487/RFC1195,
End of changes. 13 change blocks.
	21 lines changed or deleted		24 lines changed or added
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