[e2e] Re: Question on "identification" field of IP header

David Borman dab at BSDI.COM
Fri Dec 13 09:14:11 PST 2002

Just a minor nit that I feel should be clarified:

> From: der Mouse <mouse at Rodents.Montreal.QC.CA>
> Date: Fri, 13 Dec 2002 16:41:51 +0100 (CET)
> Subject: Re: Question on "identification" field of IP header
> Note that the portion of a packet returned in an ICMP does not include
> even the IP source and destination addresses; the identification value
> is almost the only value that can be relied upon to identify the
> original packet upon getting an ICMP....

Actually, ICMP packets are supposed to return the entire IP header
(including options) plus 64 bits of the IP data.  So, you should get
up to the TCP and UDP port numbers.  (RFC 792 explicitly states
that it assumes that higher level protocols have their port numbers
in the first 64 bits).

			-David Borman

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