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Message-ID: <20130729213440.GB24355@order.stressinduktion.org>
Date: Mon, 29 Jul 2013 23:34:40 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: William Manley <william.manley@...view.com>
Cc: netdev@...r.kernel.org, bcrl@...ck.org, luky-37@...mail.com,
sergei.shtylyov@...entembedded.com, bhutchings@...arflare.com,
davem@...emloft.net
Subject: Re: [PATCH v3 1/2] net: igmp: Reduce Unsolicited report interval to 1s when using IGMPv3
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 <william.manley@...view.com>
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Thanks,
Hannes
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