From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932192AbWDFQxK (ORCPT ); Thu, 6 Apr 2006 12:53:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932194AbWDFQxJ (ORCPT ); Thu, 6 Apr 2006 12:53:09 -0400 Received: from zproxy.gmail.com ([64.233.162.195]:43342 "EHLO zproxy.gmail.com") by vger.kernel.org with ESMTP id S932192AbWDFQxI convert rfc822-to-8bit (ORCPT ); Thu, 6 Apr 2006 12:53:08 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=fOVjoEtjw5fqAJSwtgkWegsAI4P5KhCPs1VAVs+BnXo0HWz+ICX9AkzIbn2lQT5emNVFhWOItZDAXolz12seVyPZDq3jszzSTvG1+xIf+giFiMC1AHU7Oz9LD3PVdKynKKHUygLEtrc1ZSmPATVbLN86sXTUJnclVer4a0VD+ww= Message-ID: <493eee610604060953jcfdd2b6wdf773f4fb828aafa@mail.gmail.com> Date: Thu, 6 Apr 2006 18:53:07 +0200 From: "Janos Farkas" To: "David Daney" Subject: Re: Broadcast ARP packets on link local addresses (Version2). Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, pgf@foxharp.boston.ma.us, freek@macfreek.nl In-Reply-To: <44353F36.9070404@avtrex.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: <17460.13568.175877.44476@dl2.hq2.avtrex.com> <44353F36.9070404@avtrex.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 4/6/06, David Daney wrote: > Janos Farkas wrote: > > Shouldn't it > > be more correct to not depend on the ip address of the used network, > > but to use the "scope" parameter of the given address? > RFC 3927 specifies the Ethernet arp broadcast behavior for only > 169.254.0.0/16. Presumably you could set the scope parameter to local > for addresses outside of that range or even for protocols other than > Ethernet. Since broadcasting ARP packets usually adversely effects > usable network bandwidth, we should probably only do it where it is > absolutely required. The overhead of testing the value required by the > RFC is quite low (3 machine instructions on i686 is the size of the > entire patch), so using some proxy like the scope parameter would not > even be a performance win. Indeed, I just have a bad feeling about hardwiring IP addresses this deep. The problems with "my" idea would be, summarily, after a day: Q: Is there are reason to use broadcast ARP semantics for other IP address ranges? A: Maybe, but no RFC defines that. Q: Is there are reason to NOT use broadcast ARP semantics for the defined IP address ranges? A: Maybe, but the RFC is against it. Q: Is there a reason to expect people (and tools) to use/define scopes? A: Probably, but it's still uncommon practice :) I mean, how many of us have 192.168.x.x addresses with "global" scope? I know I do. I'm still in a losing position :) Janos