Subject: [Isis-wg] Update to Multi-instance Multi-Topology Draft available

From: "Les Ginsberg \(ginsberg\)" <[email-masked]>
Date: Sun, 18 Jun 2006 13:57:04 -0700

Folks -

An update to the IS-IS Multi-instance Multi-topology draft is now
available. Here's the URL and the Abstract.

http://www.ietf.org/internet-drafts/draft-previdi-isis-mi-mt-01.txt

Abstract 

   This draft describes a mechanism that allows a single router to   
   share one or more links among multiple IS-IS routing protocol 
   instances. 

   Multiple instances allow the deployment of multiple address-families 
   as well as multiple instances of the same address-family and it is 
   an alternative to Multi-Topology IS-IS. Routers will form instance 
   specific adjacencies, exchange instance specific routing updates and 
   compute paths utilizing instance specific LSDB information. Each PDU 
   will contain a new TLV identifying the instance to which the PDU 
   belongs. This allows a network operator to deploy multiple IS-IS 
   topologies in parallel, using the same set of links when required 
   and still have the capability of computing topology specific paths. 
   This draft does not address the forwarding paradigm that needs to be 
   used in order to ensure data PDUs are forwarded according to the 
   topology to which they belong.

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From: Hannes Gredler <[email-masked]>
Date: Fri, 23 Jun 2006 23:06:14 +0200

> http://www.ietf.org/internet-drafts/draft-previdi-isis-mi-mt-01.txt

stefano & les,

some comments and a question from my side:

comment ad 3.1 Instance Identifier TLV

   it would be in the good tradition of the isis-wg to
   make a suggestion of a codepoint for the TLV.

general comment &
comment ad 3.4.1 MI-ISIS Layer 2 multicast address and
comment ad 3.4.2 Interoperability using p2p networks

   this draft is a non-downwards compatible change, from the moment you
   add support for multi-instance all nodes in your network need to support it.

   we should not use subnet dependend fields (like MAC adresses)
   to control the versioning. since this is a essentially a redefinition of
   all known TLVs [which are from now on now keyed by the instance-id]
   have you thought about using a different PDU version in the IS-IS common header ?

   suggestion:
      pdu-version 1 would be used for topology 0 [fully downwards compatible] and
      pdu-version 2 would be used for the per-instance-keyed topologies.

   all PDU type and TLV allocations stay as-is.

   that way you rule out any subnet specific dependencies and any node that
   does not understand pdu-version 2 will ignore it anyway, which is IMO
   a cleaner transition tool.

finally a question: how would i link nodes between different topologies if
   i wanted to do so ?

/hannes