netdev - Re: IGMP Unsolicited Report Interval too long for IGMPv3?

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Message-ID: <1374527349.1635.55.camel@bwh-desktop.uk.level5networks.com>
Date:	Mon, 22 Jul 2013 22:09:09 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	William Manley <william.manley@...view.com>
CC:	<netdev@...r.kernel.org>
Subject: Re: IGMP Unsolicited Report Interval too long for IGMPv3?

On Mon, 2013-07-22 at 21:43 +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".
> 
> 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?

I suggest you post a patch and find out what people think of it.  That
usually gets more response than asking in the abstract.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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