Subject: [Isis-wg] unauthenticated LSP purges

From: Nick Amato <[email-masked]>
Date: Fri, 24 Aug 2001 15:12:15 -0400

I have searched the archive and found nothing that relates to
this, in any case, sorry if this is an old topic.

It seems that ISO 10589 contradicts itself in the area of LSP
purges.  7.3.16.4 indicates that when the Remaining Lifetime of
an LSP in memory becomes zero:

	a) set all SRMflags for that LSP, and

	b) retain only the LSP header

Yet in 7.3.15.1, 'Action on receipt of an LSP', the authentication
checks in (5) and (6) are performed _before_ the zero lifetime check
in (b).

A popular vendor seems to check and originate simple authentication
on zero lifetime LSPs.  draft-ietf-isis-hmac-03.txt indicates that
an IS implementing MD5 should never accept unauthenticated purges.
This seems like the correct thing to do if either simple or MD5 is
in use.

Nick Amato
[email-masked]
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