Re: Asymmetry or others?
On Thu, 23 Jan 2003 chongz --at-- positioning-research.com wrote:
> Hi all,
> Sorry I asked this before but I still can't figure it out:
>
> I have two linux (2.4) boxes in two universities connecting
> via an Education WAN link. I got different bandwidth output
> if I put client and server on different boxes. One direction
> is about 15Mbps, and the other is 30Mbps. I use simple iperf
> (1.6.3) options:
> a>$./iperf -s -w 100k
> b>$./iperf -c a -w 100k
>
> Because it's education network, I really don't think it's
> asymmtric although I am asking the administrator about this.
> (But it has about 8 hops so it's pretty hard to find out all
> the configuration along the path...)
>
> I am thinking if there are other possibilities making this
> happen? I already setup the same values of the
> sys.core.[r|w]mem_[default|max] and
> sys.net.ipv4.tcp_[r|w|]mem on the two boxes.
>
> Does anyone have other suggestions except the link asymmetric?
>
> Thanks very much for your help,
> -Chong
If you are using 1.6.3 then you need to update. There is a window setting
bug in 1.6.3 that would make your above run subject to the linux 2.4
autotuning which can have an adverse effect on the window sizes being used
and therefore on performance. If this does not change the results then I
would say one of the links is much more utilized than the others or since
it is a educational network they may be doing some fair queuing in one
direction and not the other.
Kevin