[Isis-wg] ISIS std question.

[Christian E. Hopps]

I'm trying to figure out checksum failures in the isis std..

When I receive an LSP with a bad checksum the std in 7.3.14.2 says I
should generate an event, overwrite the cksum and lifetime fields with
zero and

        c) treat the link state pdu as though its remaining lifetime had
        expired (see 7.3.16.4).

It seems to me that there are some problems with this.  Since 7.3.16.4
has two cases: lifetime on a LSP _in_memory_ becoming zero (i.e., what I 
would consider `expiring') and receipt of an LSP with a zero lifetime.

If it means the former should I just treat my in DB copy of the LSP as
if it has expired?

If it means the latter it could cause problems.  What if the bogus LSP
I just received had a really large sequence number (close to `wrapping').
This would seem to allow corrupted pdus to effect the operation of the
protocol too greatly.

I looked at the proposed new text for the standard and it says to just
drop the LSP.  Is this what other vendors currently do?  It makes a lot
of sense to me :)

Chris.