Re: RE: RFC 4541 Data forwarding in snooping switches

There are several examples why this may be needed:

* A network  wishes to deploy several upstream routers to be robust to 
link/router failure. Both routers need to track the state - but your 
assumption of bandwidth is wrong - they will figure out that the traffic 
is already present and won't forward another copy.

* You have a topology with two routers with connectivity to different 
places - so one is the best path to some sources, the other to other 
sources. They exchange PIM over the switch to discover these optimised 
paths.

IMHO, flooding to the set of router ports was a fundamental part of the 
design, and must not be changed without serious working group review.

Gorry

On Tue, 12 Jun 2007, Alvaro Fernandez wrote:

> Hi everybody:
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> Section 2.1.2. of RFC 4541 says that the snooping switch must forward the data on router ports.
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> I  think this is a limitation to the bandwidth: it has no sense to connect more than one multicast router or more than one router interface to a switch because the limit of the traffic is the bandwidth of one interface because all the data must be forwarded to all routers.
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> It is so impossible to connect 5 multicast routers with 1 GBit interface to a switch and allow hosts connected to the switch to receive 5GBits of multicast because the limit is 1 GBit.
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> I know that the routers must forward the data coming from senders and to do it they must receive some information about the senders but it is not necessary to send all the data to all routers to inform routers that there is a new sender.
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> Is there any error in this conclusion?
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> Regards
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> Alvaro
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