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From: William Manley <william.manley@youview.com>
To: <linux-kernel@vger.kernel.org>
Cc: <davem@davemloft.net>
Subject: IGMP Unsolicited Report Interval too long for IGMPv3?
Date: Mon, 22 Jul 2013 11:50:09 +0100	[thread overview]
Message-ID: <51ED0E61.30106@youview.com> (raw)

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



             reply	other threads:[~2013-07-22 10:51 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-22 10:50 William Manley [this message]
2013-07-22 20:17 ` IGMP Unsolicited Report Interval too long for IGMPv3? David Miller

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