Subject: Incremental update of Fletcher's checksum

From: Igor Miroshnik <[email-masked]>
Date: Sat, 13 Sep 2003 11:06:10 -0400

Dear All,

Why should one wish to bother with this? Well, I thought not to issue a new
LSA if it differs from the predecessor merely in the sequence number.
(Unless the sequence is promoted on purpose.) The checksum comparison is a
reasonable first measure for decision on identity of two instances. Thus,
one would first compute the checksum for the old instance with the old
sequence number, and then, if needed, do the same with the next sequence
number. Doing the things incrementally would save some effort.

1) May the Fletcher's checksum be updated incrementally?
2) Does anybody know another way to effectively determine the need of
promoting the sequence?

Thanks,
Igor

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From: Fred Baker <[email-masked]>
Date: Mon, 15 Sep 2003 09:03:48 -0700

>1) May the Fletcher's checksum be updated incrementally?

Yes. ISO DIS 8473 (CLNS) actually requires that to be done, and specifies
in Annex C how to go about it. Of course, the copy of DIS 8473 I have
doesn't actually have such a section, although it refers to it...