Date: Wed, 15 Nov 2000 12:46:43 -0800 (PST) From: Luigi Rizzo <rizzo@aciri.org> To: louie@TransSys.COM (Louis A. Mamakos) Cc: ru@FreeBSD.ORG, cmott@scientech.com, archie@dellroad.org, net@FreeBSD.ORG, ari@suutari.iki.fi Subject: Re: libalias: Incremental Update of Internet Checksum Message-ID: <200011152046.MAA00949@iguana.aciri.org> In-Reply-To: <200011152043.eAFKhMG68318@whizzo.transsys.com> from "Louis A. Mamakos" at "Nov 15, 2000 3:43:22 pm"
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> > If the above would be true that would mean that almost all implementations > > of computing the checksum are wrong, i.e. they produce the value of 0x0000 > > as a checksum when it should actually be 0xffff. That would also mean all > > three RFCs: 1071, 1141 and 1624 are wrong. I can't believe that! > > But the thing is, both 0xffff and 0x0000 are the same value == 0. (One is hmm... from memory: one of the two 'zero' values is used in UDP to indicate NO CHECKSUM. Not sure if the same applies to TCP and IP headers as well, but this would explain why the error (if there) goes unnoticed. cheers luigi ----------------------------------+----------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . ACIRI/ICSI (on leave from Univ. di Pisa) http://www.iet.unipi.it/~luigi/ . 1947 Center St, Berkeley CA 94704 Phone: (510) 666 2927 ----------------------------------+----------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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