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From: KVC@ENGVAX.SCG.HAC.COM (Kevin Carosso)
Newsgroups: comp.protocols.tcp-ip
Subject: question about berkeley TCP/IP
Message-ID: <8706270349.AA26555@ucbvax.Berkeley.EDU>
Date: Fri, 26-Jun-87 22:06:00 EDT
Article-I.D.: ucbvax.8706270349.AA26555
Posted: Fri Jun 26 22:06:00 1987
Date-Received: Sat, 27-Jun-87 19:37:26 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
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When a SYN is sent to a Berkeley UNIX TCP/IP implementation (4.3 or 4.2)
it appears that UNIX can send the SYN-ACK without having to ARP for the
host it's ACKing.  Does it indeed add an entry to the ARP table when an
ethernet IP packet comes in?  I'll buy that anything to cut down
on ethernet broadcasts is a good thing...

This may seem like a dumb question, but the code is a little opaque and
I'm not a UNIX kernel hack.  I have a hypothesis which explains some behaviour
I'm seeing with the TCP I maintain (CMU/Tek for VAX/VMS) and UNIX must be
doing this if my theory's any good.

Thanks,

        /Kevin Carosso                     kvc@engvax.scg.hac.com
         Hughes Aircraft Co.               kvc%engvax@oberon.usc.edu