Date: Wed, 25 Mar 1998 06:55:44 PST From: "pratap singh" <v_pr@hotmail.com> To: v_pr@hotmail.com, dg@root.com Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: ARP REQUEST question Message-ID: <19980325145544.10507.qmail@hotmail.com>
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Hi all, I perfectly know about the CRC carried in the ethernet frames. But if that is the case the higher layer protocols still do the checksum like IP. the reasons that I feel for not having the checksum in the ARP frame are: 1> IP packets get routed and can be seen to ascend and descend protocol stacks till they reach their destination. So even if the layer 2 (ethernet) checksum is right, they may get corrupted during the ascend and descend. And if the checksum is not provided by the IP itself, this error could go unnoticed. 2> However same is not the case with ARP which in the protocol stack sat with the hardware independent part of the Ethernet driver or any other layer 2 driver (historically) and so the traversal of the protocol stack was not necessary. And the local significance made the CRC just enough for detecting errors. But what in case of network stacks of today where the ARP is seen sitting together with IP or at the same level of IP. Someone Please correct me If I am wrong prats >From root@implode.root.com Tue Mar 24 16:15:26 1998 >Received: from implode.root.com (localhost [127.0.0.1]) > by implode.root.com (8.8.5/8.8.5) with ESMTP id OAA27230; > Tue, 24 Mar 1998 14:25:08 -0800 (PST) >Message-Id: <199803242225.OAA27230@implode.root.com> >To: "pratap singh" <v_pr@hotmail.com> >cc: freebsd-hackers@FreeBSD.ORG >Subject: Re: ARP REQUEST question >In-reply-to: Your message of "Tue, 24 Mar 1998 14:04:47 PST." > <19980324220447.14324.qmail@hotmail.com> >From: David Greenman <dg@root.com> >Reply-To: dg@root.com >Date: Tue, 24 Mar 1998 14:25:08 -0800 >Sender: root@implode.root.com > >>Hi all gurus of Networking, >>I have a basic doubt. Every layer has a cehcksum being calculated >>whereas the ARP frame does not have. Can anyone throw light on this >>please. Is it because the ARP packets donot traverse the LAN boundary >>and error rates in LAN environment are very low compared to the WAN >>error rates???? > > All ethernet packets have a 32bit CRC, so the arps are protected by that. > >-DG > >David Greenman >Core-team/Principal Architect, The FreeBSD Project > ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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