netdev - Re: igmp: Staggered igmp report intervals for unsolicited igmp reports

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Date:	Wed, 22 Sep 2010 16:33:14 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Bob Arendt <rda@...con.com>
cc:	David Stevens <dlstevens@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: igmp: Staggered igmp report intervals for unsolicited igmp
 reports

On Wed, 22 Sep 2010, Bob Arendt wrote:

> multicast traffic is received. While IGMPv2 defines an "Unsolicited Report
> Interval" default of 10 seconds, it appears that this is a significant enough
> issue that the later IGMPv3 document calls out a default of 1 second, and
> goes on to define a "Robustness Variable" and talks about the same case that
> Christoph is trying to mitigate.

Actually that suggests a different way to reach the same goal:


Subject: igmp: Make unsolicited report interval conform to RFC3376

RFC3376 specifies a shorter time interval for sending igmp joins.
This can address issues where joins are slow because the initial join is
frequently lost.

Also increment the frequency so that we get a 10 reports send over a
few seconds.

Signed-off-by: Christoph Lameter <cl@...ux.com>


---
 net/ipv4/igmp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6/net/ipv4/igmp.c
===================================================================
--- linux-2.6.orig/net/ipv4/igmp.c	2010-09-22 16:28:17.000000000 -0500
+++ linux-2.6/net/ipv4/igmp.c	2010-09-22 16:28:54.000000000 -0500
@@ -114,9 +114,9 @@

 #define IGMP_V1_Router_Present_Timeout		(400*HZ)
 #define IGMP_V2_Router_Present_Timeout		(400*HZ)
-#define IGMP_Unsolicited_Report_Interval	(10*HZ)
+#define IGMP_Unsolicited_Report_Interval	(HZ)
 #define IGMP_Query_Response_Interval		(10*HZ)
-#define IGMP_Unsolicited_Report_Count		2
+#define IGMP_Unsolicited_Report_Count		10


 #define IGMP_Initial_Report_Delay		(1)
--
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