Re: Question about proxy implemenation in RFC 4605

Hi Kunal,

      When a box run IGMP proxy, it has router interfaces (interfaces that runs router part of IGMP) to collect membership information and host interface (interfaces that runs host part of IGMP) to report the membership to upstream router. Before reporting membership on host interface, it aggregates the membership collected from router interfaces. Now aggregating membership information in the box is done similar to how it is defined in RFC 3376 for hosts when multiple sockets are bound. So similar rules apply when any of these membership change (It will be similar to the case when one of the sockets are closed).

     In your case below, when join comes one by one, the next state is determined as explained in RFC 3376 ( as if a new socket is opened every time) and that is how you reach a particular state of EXC( G, NULL ). Similarly when one of the interface send a leave (on host interface side, this will be treated as if that socket is closed), it re-calculates the new state and use that.

     Let me know if this clears up things.

Thanks,
Bharat
________________________________________
From: [email protected] [[email protected]] On Behalf Of Kunal Shah [[email protected]]
Sent: Saturday, October 30, 2010 6:16 AM
To: [email protected]
Subject: [magma] Question about proxy implemenation in RFC 4605

Hi all,

According to RFC 4605, a router creates a membership database after merging the subscriptions on individual interfaces. Lets say that 3 IGMPv3 capable interfaces are as follows:

Interface 1 has host reporting Include S1 -> I(S1)
Interface 2 has host reporting Exclude S2 -> E(0,S2)
Interface 3 has host reporting Exclude nothing -> E(0,0)

For a device doing IGMPv3 proxy, the final membership record for group G is (G, EXCLUDE, NULL). Now lets say the host on interface 3 goes away, because of which the subscription on interface 3 would expire and there wont be any IGMPv3 state on interface 3.  How would the new membership record for PROXY be calculated?? The RFC does not suggest any way to do this. Would IGMP process have to go through each interface again and then recompute the new membership record?? This would be very inefficient especially if there are multiple interfaces.
Is there a better way to recompute the new membership record??


Thanks
Kunal



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