From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH 1/2] net: igmp: Reduce Unsolicited report interval to 1s when using IGMPv3 Date: Fri, 26 Jul 2013 18:39:13 +0200 Message-ID: <20130726163913.GG3890@order.stressinduktion.org> References: <1374527349.1635.55.camel@bwh-desktop.uk.level5networks.com> <1374754445-5608-1-git-send-email-william.manley@youview.com> <20130726163239.GE3890@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 To: William Manley , netdev@vger.kernel.org, bcrl@kvack.org, luky-37@hotmail.com, sergei.shtylyov@cogentembedded.com, bhutchings@solarflare.com, davem@davemloft.net Return-path: Received: from s15338416.onlinehome-server.info ([87.106.68.36]:41543 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756941Ab3GZQjO (ORCPT ); Fri, 26 Jul 2013 12:39:14 -0400 Content-Disposition: inline In-Reply-To: <20130726163239.GE3890@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Jul 26, 2013 at 06:32:39PM +0200, Hannes Frederic Sowa wrote: > On Thu, Jul 25, 2013 at 01:14:04PM +0100, William Manley wrote: > > If an IGMP join packet is lost you will not receive data sent to the > > multicast group so if no data arrives from that multicast group in a > > period of time after the IGMP join a second IGMP join will be sent. The > > delay between joins is the "IGMP Unsolicited Report Interval". > > > > Previously this value was hard coded to be chosen randomly between 0-10s. > > This can be too long for some use-cases, such as IPTV as it can cause > > channel change to be slow in the presence of packet loss. > > > > The value 10s has come from IGMPv2 RFC2236, which was reduced to 1s in > > IGMPv3 RFC3376. This patch makes the kernel use the 1s value from the > > later RFC if we are operating in IGMPv3 mode. IGMPv2 behaviour is > > unaffected. > > > > Tested with Wireshark and a simple program to join a (non-existent) > > multicast group. The distribution of timings for the second join differ > > based upon setting /proc/sys/net/ipv4/conf/eth0/force_igmp_version. > > > > [...] > > > > [...] > > Otherwise I am fine with it. Also, could you have a look at IPv6, too? We currently use a hardcoded IGMP6_UNSOLICITED_IVAL = 10*HZ there. Thanks, Hannes