FWD:: Re: Question on "identification" field of IP header
Mark Allman <mallman@grc.nasa.gov> Wed, 18 December 2002 15:35 UTC
Message-Id: <200212181535.KAA27775@guns.lerc.nasa.gov>
To: tcp-impl@grc.nasa.gov
From: Mark Allman <mallman@grc.nasa.gov>
Reply-To: mallman@grc.nasa.gov
Subject: FWD:: Re: Question on "identification" field of IP header
Organization: BBN Technologies/NASA GRC
Song-of-the-Day: Not Fade Away
Date: Wed, 18 Dec 2002 10:35:40 -0500
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------- Forwarded Message Date: Fri, 13 Dec 2002 15:42:08 -0500 From: Felix Hernandez-Campos <fhernand@cs.unc.edu> To: end2end <end2end-interest@postel.org>, TCP-IMPL <tcp-impl@grc.nasa.gov> Subject: Re: Question on "identification" field of IP header Ramesh Shankar wrote: > 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. You may want to have a look at Steve Bellovin's "A Technique for Counting NATed Hosts", presented at IMW 2002. The paper discusses how the IP header's ID field can be used to infer the number of hosts behind a NAT box. Regards, Felix. - -- Felix Hernandez-Campos http://www.cs.unc.edu/~fhernand ------- End of Forwarded Message