[e2e] Question on "identification" field of IP header
RShankar at Novell.com
Fri Dec 13 06:49:36 PST 2002
If the "Don't fragment bit" is set in the IP header, what purpose does
the "identification" field serve? Why can't I simply put 0 for this
field in such a case? I remember coming across some e-mail chain in one
of the mailing lists (TCP-IMPL, e2e, TSVWG) about this issue and the
interaction with NAT. But I am not sure what came out of that discussion.
Also, some of the "OS fingerprinting" techniques in the networking world
apparently use the IP ID field to identify various operating systems.
Apparently some operating systems (or protocol stacks, if you prefer)
don't increment this by 1. Why would anyone want to do this? Wouldn't
this cause possibles issues wrt to wrap around in the possible case of
fragmentation? One could always argue that with high speed Ethernet,
that anyway would be a possibility, but I would like to understand the
reason behind such a case.
Thanks for your time,
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