[Udpcast] multi computer cast problem

Alain Knaff alain at knaff.lu
Thu Sep 25 12:13:51 CEST 2008


PaweĊ‚ Ufnalewski // BSS wrote:
> But why when there's one client it goes full speed and when there are >=
> 2 it drops to 0.29? It's problem with unicast not the mulitcast.

Indeed, in one case, it's unicast, and in the other it is multicast. If
there is only one client, the sender falls back on unicast, which is
handled much better by most switches.

[...]
> Tried that - only 1gb nics connected to 100Mb/s backbone.
                                       ^^^^^^^^^^^^^^^^^^^
Please do try it with only 3 PC's (1 sender, 2 receivers) connected to the
switch. Nothing else. And I do mean, nothing else (well, except the power,
of course...). And from there work your way upwards until it becomes slow.
Indeed, as soon as a switch is connected to another switch (uplink,
backbone, ...), it also becomes vulnerable to whatever else is connected to
that other switch (flow control propagates, unfortunately). I know, it does
take some patience, but AFAIK, this is the only way to find out what is
triggering the slowdown.

Regards,

Alain



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