Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 (Tek) 9/26/83; site hammer.UUCP Path: utzoo!linus!decvax!tektronix!orca!hammer!steveg From: steveg@hammer.UUCP (Steve Glaser) Newsgroups: net.lan Subject: Re: (DoD) InterNet Header Checksum Message-ID: <937@hammer.UUCP> Date: Sun, 30-Sep-84 18:23:50 EDT Article-I.D.: hammer.937 Posted: Sun Sep 30 18:23:50 1984 Date-Received: Tue, 2-Oct-84 03:54:50 EDT References: <624@ttds.UUCP> <52@redwood.UUCP> Organization: Tektronix, Wilsonville OR Lines: 8 Berkeley uses a "cute trick" to speed up doing the ones complement addition on a twos complement machine (like the VAX). They do the end around carries at then end of the buffer letting them accumulate in the high half of a 32 bit register for a while (TCP/IP checksums are 16 bits). They use the inline assembler for speed and so that they can get to the vax adwc instruction (add with carry). Steve Glaser