Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755420AbZFET3u (ORCPT ); Fri, 5 Jun 2009 15:29:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753391AbZFET3e (ORCPT ); Fri, 5 Jun 2009 15:29:34 -0400 Received: from woodchuck.wormnet.eu ([77.75.105.223]:42281 "EHLO woodchuck.wormnet.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753288AbZFET3d (ORCPT ); Fri, 5 Jun 2009 15:29:33 -0400 Date: Fri, 5 Jun 2009 20:29:34 +0100 From: Alexander Clouter To: david@lang.hm Cc: linux-kernel@vger.kernel.org, sefi@s-e-f-i.de Subject: Re: When does Linux drop UDP packets? Message-ID: <20090605192933.GH2014@woodchuck> References: <20090604145347.GA27692@miyuki> <20090605191025.GG2014@woodchuck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: diGriz X-URL: http://www.digriz.org.uk/ X-JabberID: alex@digriz.org.uk User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1837 Lines: 49 Hi, * david@lang.hm [2009-06-05 12:15:27-0700]: > > On Fri, 5 Jun 2009, Alexander Clouter wrote: > > > * david@lang.hm [2009-06-04 16:19:56-0700]: > > > > > > On Thu, 4 Jun 2009, Alexander Clouter wrote: > > > > > > > > It's dead easy to transmit and receive multicast traffic, broadcasting > > > > network traffic is so 1980's :) > > > > > > there is only a difference between multicast and broadcast traffic if you > > > are spanning subnets. > > > > > Well yes and no. Broadcast traffic is *always* handled by the kernel as > > only the kernel can tell if it is interested in it or not. With > > multicast the NIC is configured to only pass particular > > Ethernet multicast packets up to the kernel. > > > > By using broadcast traffic the load (okay, hardly a big problem > > now-a-days) hits *all* the workstations on the subnet, with multicast, > > only those interested in the traffic receive it. > > true, but only for some NICs, and even those tend to have a fairly small > number of slots for the filters. past these limits the OS handles it all > just like broadcasts. > I *think* only the early ones have a naff non-hashing based to filter multicast flows, could be wrong though. Either way, as a packet pusher by day, I dream of the venduh's discovering that multicast can be used for device discovery rather than expecting everything to be on the same subnet :-/ In this day and age, using broadcast to do a job is just plain lazy and braindead. Cheers -- Alexander Clouter .sigmonster says: Misuse may cause suffocation. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/