Re: Asymmetrical bandwidth

Les Klassen Hamm wrote:

> Running two instances of iperf, one in each direction, simultaneously,
> the linux box sends to XP at 90 Mb/s, and the XP box sends to linux at
> 22 Mb/s.
>
> So then I tried from a third computer, a laptop running XP, in dual mode.
> From the notebook to the original XP: Out 61 Mb/s, In 86 Mb/s
> From the notebook to the linux box: Out 20 Mb/s, In 92 Mb/s
> So between the XP's, only a slight difference.
> But when talking to the linux box, same results as before.
>
>> What does a udp test show? Is the cpu being maxed out?

> UDP to the linux box is about 25, when it's just a simple test, and the
> same if I run a UDP test from both machines simultaneously. The UDP from
> the linux box to the XP box is about 86. In UDP dual mode, same results
> (86 and 25)
>
> No, cpu load is low, about 5%, so I think it shouldn't be relevant.

I suspect for TCP it may have something to do with window sizes and or
congestion control algorithms. The Windows boxes play nicely together,
but linux doesn't react as expected.

For udp, I'm a bit at a loss. What do you get for UDP speeds between
two windows machines?

Chris
Received on Mon Jun 2 11:55:41 2008