From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Subject: Re: igmp: Staggered igmp report intervals for unsolicited igmp reports Date: Thu, 23 Sep 2010 10:37:48 -0500 (CDT) Message-ID: References: <4C9A6D87.2000103@rincon.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "David S. Miller" , "linux-rdma@vger.kernel.org" , "netdev@vger.kernel.org" , Bob Arendt To: David Stevens Return-path: Received: from smtp108.prem.mail.ac4.yahoo.com ([76.13.13.47]:43596 "HELO smtp108.prem.mail.ac4.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752760Ab0IWPhw (ORCPT ); Thu, 23 Sep 2010 11:37:52 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 22 Sep 2010, David Stevens wrote: > > > > Also increment the frequency so that we get a 10 reports send over a > > few seconds. > > Except you want to conform and not conform at the same time. :-) > IGMPv2 should be: default count 2, interval 10secs > IGMPv3 should be: default count 2, interval 1sec This is during the period of unsolicited igmp reports. We do not know if this group is managed using V3 or V2 since no igmp query/report has been received yet. > ...and no way is it a good idea to send 10 unsolicited reports on an > Ethernet. Why would that be an issue? The IGMPv2 RFC has no strict limit and RFC3376 mentions that the retransmission occurs "Robustness Variable" times minus one. Choosing 10 for the "Robustness Variable" is certainly ok. If we do not increase the number of reports but just limit the interval then the chance of outages of a second or so during mc group creation causing routers missing igmp reports is significantly increased.