The IP over ATM Mailing List Archive by date

[jhalpern@newbridge.com (Joel Halpern)]

The TCP checksum is provided for end-to-end protection.
In general, running TCP over IP, one should not omit the TCP checksum just
because the media in the current communication path are deemed to be
"sufficiently reliable".

Now, there is another case.  If one is establishing a VC (over ATM or 
anything else) between two TCP entities, one may invoke a form of
header compression, header implication if you will, in which only a
very few fields in the IP and TCP header are actually shipped as data
over the VC.  In that case, one of the omitted fields might be the
TCP checksum.  Signficiant care should be taken before doing that,
as some of the checks for "are the correct two parties talking" are
done implicitly by that checksum.

Yours,
Joel M. Halpern				jhalpern@newbridge.com
Newbridge Networks Inc.