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From: louie@trantor.UMD.EDU (Louis A. Mamakos)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: question about berkeley TCP/IP
Message-ID: <8706291931.AA17632@trantor.UMD.EDU>
Date: Mon, 29-Jun-87 15:31:09 EDT
Article-I.D.: trantor.8706291931.AA17632
Posted: Mon Jun 29 15:31:09 1987
Date-Received: Wed, 1-Jul-87 05:47:31 EDT
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What probably happens is that who every sent the original packet with
a SYN segment first had to ARP for your address.  The 4.x BSD ARP
module caches the address of the host requesting your address; thus
when you want to reply, the ARP mapping is already present.

Louis A. Mamakos  WA3YMH    Internet: louie@TRANTOR.UMD.EDU
University of Maryland, Computer Science Center - Systems Programming