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Re: [Linux-cluster] Choose between broadcast and multicast for cman



On Thu, 2006-06-01 at 09:43 +0100, Patrick Caulfield wrote:
> Riaan van Niekerk wrote:
> > Is there any reason or advantage to use multicast over broadcast, which
> > offsets the complexity of multicast (relative to broadcast), e.g more
> > control, less traffic, others?
> 
> Generally multicast behaves the same as broadcast. The only time you would
> need multicast is if your nodes are on different subnets - in which case you
> would also have to make sure the router had sufficiently low latencies to
> support clustering over it.
> 
> 
> 

To add to Patrick's comments, some multicast switches (managed) support
IGMP which allows multicasted packets to only be sent to ports which are
subscribed to a specific multicast address.  This can increase
throughput on those nodes that are not part of the cluster and hence
shouldn't be receiving those broadcasts.

Keep in mind that some switches IGMP implementation is broken.

Regards
-steve


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