< draft-ietf-isis-ipv6-05.txt		draft-ietf-isis-ipv6-06.txt >
	Internet Engineering Task Force Christian E. Hopps
	INTERNET-DRAFT Allegro Networks
	Expires June 2003 8 January 2003
	Routing IPv6 with IS-IS
	<draft-ietf-isis-ipv6-05.txt>
	Status of this Memo
	This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.
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	Copyright Notice
	Copyright (C) The Internet Society 2003. All Rights Reserved.
	Draft Routing IPv6 with IS-IS January 2003
	Abstract
	This draft specifies a method for exchanging IPv6 routing information		This Internet-Draft, draft-ietf-isis-ipv6-05.txt, has expired, and has been deleted
	using the IS-IS routing protocol. The described method utilizes 2		from the Internet-Drafts directory. An Internet-Draft expires 185 days from
	new TLVs, a reachability TLV and an interface address TLV to		the date that it is posted unless it is replaced by an updated version or is
	distribute the necessary IPv6 information throughout a routing		under official review by the IESG for publication as an RFC. This Internet-Draft
	domain. Using this method one can route IPv6 along with IPv4 and OSI		was not published as an RFC.
	using a single intra-domain routing protocol.
	1. Terms
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119.
	2. Overview
	IS-IS [0] is an extendible intra-domain routing protocol. Each
	router in the routing domain issues an LSP that contains information
	pertaining to that router. The LSP contains typed variable length
	data often referred to as TLVs (type-length-values). We extend the
	protocol with 2 new TLVs to carry information required to perform
	IPv6 routing.
	In [1] a method is described to route both OSI and IPv4. We utilize
	this same method with some minor changes to allow for IPv6. To do so
	we must define 2 new TLVs, namely "IPv6 Reachability" and "IPv6
	Interface Address" and a new IPv6 protocol identifier. In our new
	TLVs we utilize the extended metrics and up/down semantics of [2].
	3. IPv6 Reachability TLV
	The "IPv6 Reachability" TLV is TLV type 236 (0xEC).
	[1] defines 2 Reachability TLVs, "IP Internal Reachability
	Information" and "IP External Reachability Information". We provide
	the equivalent IPv6 data with the "IPv6 Reachability" TLV and an
	"external" bit.
	The "IPv6 Reachability" TLV describes network reachability through
	the specification of a routing prefix, metric information, a bit to
	indicate if the prefix is being advertised down from a higher level,
	Draft Routing IPv6 with IS-IS January 2003
	a bit to indicate if the prefix is being distributed from another
	routing protocol and OPTIONALLY the existence of sub-TLVs to allow
	for later extension. This data is represented by the following
	structure:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type = 236 | Length | Metric .. |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| .. Metric |U|X|S| Reserve | Prefix Len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Prefix ...
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|Sub-TLV Len(*) | Sub-TLVs(*) ...
	* - if present
	U - up/down bit
	X - external original bit
	S - subtlv present bit
	This structure MAY appear any number of times (including none) within
	the TLV.
	As is described in [2], "the up/down bit is set to 0 when a prefix is
	first injected into IS-IS. If a prefix is redistributed from a
	higher level to a lower level (e.g., level two to level one), the bit
	SHALL be set to 1 to indicate that the prefix has travelled down the
	hierarchy. If a prefix is redistributed from an area to another area
	at the same level then the up/down bit SHALL be set to 1."
	If the prefix was distributed into IS-IS from another routing
	protocol the external bit SHALL be set to 1. This information is
	useful when distributing prefixes from IS-IS to other protocols.
	If the sub-TLV bit is set to 0 then the octets of sub-TLVs are not
	present. Otherwise the bit is 1 and the octet following the prefix
	will contain the length of the sub-TLV portion of the structure.
	The prefix is "packed" in the data structure. That is, only the
	required number of octets of prefix are present. This number can be
	computed from the prefix length octet as follows:
	prefix octets = integer of ((prefix length + 7) / 8)
	Draft Routing IPv6 with IS-IS January 2003
	Just as in [2], if a prefix is advertised with a metric larger than
	MAX_V6_PATH_METRIC (0xFE000000), this prefix MUST not be considered
	during the normal SPF computation. This will allow advertisement of
	a prefix for purposes other than building the normal IPv6 routing
	table.
	If sub-TLVs are present they have the same form as normal TLVs as
	shown below.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length | Value(*) ..
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* - if present
	Length indicates how many octets of value are present and can be 0.
	4. IPv6 Interface Address TLV
	The "IPv6 Interface Address" TLV is TLV type 232 (0xE8).
	This TLV maps directly to [1]'s "IP Interface Address" TLV. We
	necessarily modify the contents to be 0-15 16 octet IPv6 interface
	addresses instead of 0-63 4 octet IPv4 interface address.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type = 232 | Length | Interface Address 1(*) .. |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| .. Interface Address 1(*) .. |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| .. Interface Address 1(*) .. |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| .. Interface Address 1(*) .. |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Interface Address 1(*) .. | Interface Address 2(*) ..
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	* - if present
	We further restrict the semantics of this TLV depending on where it
	is advertised. For Hello PDUs the "Interfaces Address" TLV MUST
	contain only the link-local IPv6 addresses assigned to the interface
	Draft Routing IPv6 with IS-IS January 2003
	which is sending the Hello. For LSPs the "Interfaces Address" TLVs
	MUST contain only the non-link-local IPv6 addresses assigned to the
	IS.
	5. IPv6 NLPID
	The value of the IPv6 NLPID is 142 (0x8E).
	As with [1] and IPv4, if the IS supports IPv6 routing using IS-IS, it
	MUST advertise this in the "NLPID" TLV by adding the IPv6 NLPID.
	6. Operation
	We utilize the same changes to [1] as made in [2] for the processing
	of prefix information. These changes are both related to the SPF
	calculation.
	Since the metric space has been extended we need to redefine the
	MAX_PATH_METRIC (1023) from the original specification in [1]. This
	new value MAX_V6_PATH_METRIC is the same as in [2] (0xFE000000). If
	during the SPF a path metric would exceed MAX_V6_PATH_METRIC it SHALL
	be considered to be MAX_V6_PATH_METRIC.
	The order of preference between paths for a given prefix MUST be
	modified to consider the up/down bit. The new order of preference is
	as follows (from best to worst).
	1. Level 1 up prefix
	2. Level 2 up prefix
	3. Level 2 down prefix
	4. Level 1 down prefix
	If multiple paths have the same best preference then selection occurs
	based on metric. Any remaining multiple paths SHOULD be considered
	for equal-cost multi-path routing if the router supports this, otherwise
	the router can select any one of the multiple paths.
	7. Security Considerations
	This document raises no new security considerations.
	Draft Routing IPv6 with IS-IS January 2003
	8. References
	[0] "Intermediate System to Intermediate System Intra-Domain Routeing
	Exchange Protocol for use in Conjunction with the Protocol for
	Providing the Connectionless-mode Network Service (ISO 8473)", ISO
	10589, 1992.
	[1] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
	Environments", RFC 1195, December 1990.
	[2] Smit, H., and T. Li, "IS-IS extensions for Traffic Engineering",
	Work in Progress, August 2001.
	9. Author's Address
	Christian E. Hopps
	Allagro Networks
	6399 San Ignacio Ave.
	San Jose, CA 95119
	U.S.A.
	Phone: +1 408 281 5500
	Email: chopps@allegronetworks.com
	10. Full Copyright Statement
	Copyright (C) The Internet Society 2003. All Rights Reserved.
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	"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING		Chris Hopps <chopps@rawdofmt.org>
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