Re: multicast: same port, different IP address?

From: Jeremy Jackson
Date: Wed Apr 08 2009 - 13:55:48 EST

On Wed, 2009-04-08 at 12:41 -0500, Matt Garman wrote:
> On Wed, Apr 8, 2009 at 11:52 AM, Lawrence MacIntyre
> <macintyrelp@xxxxxxxx> wrote:
> > If all nodes need all of those messages, then you should probably use one
> > multicast address and multiple ports. This will reduce the routing
> > overhead. However, if different nodes need different messages, then you
> > would increase the network overhead by sending all messages to all nodes.
> The latter case is what we need. We are basically already using the
> former, but since all messages aren't required at all sites, we're
> trying to reduce network load. (We have lots of message types and
> very high message volume.)

To conserve resources, you should consider the choice of multicast
addresses you use. You will want to choose them so that all your
hardware, switches, routers, NICs, can use hardware filtering. Various
NICs have different hardware multicast filter types/sizes, so I guess
you'd have to consult the driver sources, but hardware filtering avoids
interrupts for packets a machine isn't interested in, so it's worth

Jeremy Jackson
Coplanar Networks

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