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

Christoph Lameter [off-list ref] wrote on 09/23/2010 10:37:28 AM:

If all unsolicited igmp reports are lost then the router will
only start forwarding the mc group after the reporting intervals
(which could be in the range of minutes) when it triggers igmp reports
through a general igmp query. Until that time the MC group looks dead. 

And

people and software may conclude that the **** network is broken.

        You can, of course, add a querier (or configure it, assuming
an attached switch supports it) and set the query interval and robustness
count as appropriate for that network.

This is a general issue for any network where configurations for MC
forwarding is needed and where initial igmp reports may get lost.

Meaning "IB-only", right? :-) Maybe other NBMA networks too, but
certainly not a typical problem for typical networks (i.e., Ethernet).

A staggering of time intervals would be a general solution to that 

issue.

As would be having those networks queue packets for hardware addresses 
they
know require a delay before a transmit can complete. But that approach 
can't
adversely affect already-working solutions for typical networks, or
depart unnecessarily from established standard protocols.

 +-DLS

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