From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH v3 1/2] net: igmp: Reduce Unsolicited report interval to 1s when using IGMPv3 Date: Mon, 29 Jul 2013 23:34:40 +0200 Message-ID: <20130729213440.GB24355@order.stressinduktion.org> References: <20130726163610.GF3890@order.stressinduktion.org> <1375107711-9029-1-git-send-email-william.manley@youview.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: netdev@vger.kernel.org, bcrl@kvack.org, luky-37@hotmail.com, sergei.shtylyov@cogentembedded.com, bhutchings@solarflare.com, davem@davemloft.net To: William Manley Return-path: Received: from s15338416.onlinehome-server.info ([87.106.68.36]:47128 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752633Ab3G2Vem (ORCPT ); Mon, 29 Jul 2013 17:34:42 -0400 Content-Disposition: inline In-Reply-To: <1375107711-9029-1-git-send-email-william.manley@youview.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Jul 29, 2013 at 03:21:50PM +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. > > Signed-off-by: William Manley Acked-by: Hannes Frederic Sowa Thanks, Hannes