Subject: RE: [Isis-wg] Last Call: Three-Way Handshake for IS-IS Point-to-P oint Adjacencies to Informational

From: Jeff Parker <[email-masked]>
Date: Mon, 13 May 2002 12:25:19 -0400

> Am I missing something here ?
> 
> In my opinion the 3 problems described in this draft
> (draft-ietf-isis-3way-06.txt) hardly exist.
> 
> Problem 1
> ---------
> I do not know what exactly is meant with "a cut set of one 
> through the link",
> but anyway, if a link comes back up a CSNP will be sent *AND* the
> SRM flag for all LSPs will be set for this link. This means 
> all LSPs will be
> sent (and the SRM flag won't be reset until explicit acknowledgement).

"Cut set" is a graph theory term for a set whose removal
splits a connected graph into parts.

> 
> Problem 2
> ---------
> A unidirectional link failure will not be detected by only one system.
> If a node stops receiving p2p IIHs the adjacency will be down 
> *AND* the
> node should stop sending IIHs and continue (or restart) sending ISHs.
> This causes the adjacency to be down at the remote node also.
> ISO10589 may not be very clear about this, but IS-IS 
> implementations are
> supposed to work this way.

Not all link layers are created equal.  Some point to point
links don't have the smarts to reset.   Note that the authors
refer to this in their introduction (below).  

- jeff parker

1.0  Introduction

   The IS-IS protocol [1] assumes certain requirements stated in ISO
   10589 (section 6.7.2) for the operation of IS-IS over point-to-point
   links and hence provides only a two-way handshake when establishing
   adjacencies on point-to-point links. The protocol does not operate
   correctly if these subnetwork requirements for point-to-point links
   are not met. The basic mechanism defined in the standard is that each
   
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