From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932216Ab3GVKvn (ORCPT ); Mon, 22 Jul 2013 06:51:43 -0400 Received: from [65.55.88.12] ([65.55.88.12]:45279 "EHLO tx2outboundpool.messaging.microsoft.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753078Ab3GVKvm (ORCPT ); Mon, 22 Jul 2013 06:51:42 -0400 X-Forefront-Antispam-Report: CIP:157.56.250.85;KIP:(null);UIP:(null);IPV:NLI;H:AMXPRD0511HT003.eurprd05.prod.outlook.com;RD:none;EFVD:NLI X-SpamScore: 0 X-BigFish: PS0(zzzz208ch1ee6h1de0h1fdah2073h1202h1e76h1d1ah1d2ah1fc6hzz1de098h17326ah1de097h1de096h8275bh8275dhz2fh2a8h668h839h93fhd25he5bhf0ah1288h12a5h12a9h12bdh137ah13b6h1441h1504h1537h153bh162dh1631h1758h18e1h190ch1946h19ceh1ad9h1b0ah1d0ch1d2eh1d3fh1dc1h1dfeh1dffh1155h) Message-ID: <51ED0E61.30106@youview.com> Date: Mon, 22 Jul 2013 11:50:09 +0100 From: William Manley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130116 Icedove/10.0.12 MIME-Version: 1.0 To: CC: Subject: IGMP Unsolicited Report Interval too long for IGMPv3? Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [31.221.37.8] X-OriginatorOrg: youview.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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". In the kernel this seems to be hard coded to be chosen randomly between 0-10s. In our use-case (IPTV) this is too long as it can cause channel change to be slow in the presence of packet loss. I would guess that this 10s has come from IGMPv2 RFC2236, which was reduced to 1s in IGMPv3 RFC3376. There was a thread about this on linux-rdma in 2010 in the context of IP over Infiniband but it seems no patches got applied as a result of the discussion: http://www.mail-archive.com/linux-rdma@vger.kernel.org/msg05740.html Would the right patch reducing the unsolicited report interval for IGMPv3 be acceptable now? Thanks Will