ndt-users list created

[Bill Abbott <>]

I don't think it's this; the same two servers could transfer at much 
higher speeds several months ago, when I did the original tuning.

Jim Cotton wrote:
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> I have seen several Dell servers on campus that exhibited such a problem
> with their on-board chipset.
>
> There is a problem with the Broadcom chip set below a certain
> revision...  If you get the right driver it will work around it.
>
> Jim Cotton
>
> Bill Abbott wrote:
> > I've tried tcp send and receive (max) buffers from 64k up to 8 MB, no
> > improvement.
> >
> > Smaller buffers are more consistent, larger buffers tend to go up then
> > hit zero, then climb again.
> >
> > The current settings are:
> >
> > $ cat /proc/sys/net/ipv4/tcp_rmem
> > 4096    87380   8174760
> > $ cat /proc/sys/net/ipv4/tcp_wmem
> > 4096    16384   8131072
> >
> > I've also modified a bunch of other stuff, but it didn't make a
> > difference so I set it back.  ECN, /proc/sys/net/core/rmem_max and
> > wmem_max, netdev_max_backlog, etc.
> >
> >
> >
> >
> > Matthew J Zekauskas wrote:
> > > To follow up to myself...
> > >
> > > * The Internet2 servers are all gigE, and all 9000-byte MTU capable.
> > >
> > > * Another thing you could do is tune for the bottleneck instead of
> > > gigabit..
> > >
> > >    150 Mbps = 150*1000*1000 bits * 0.07 ms RTT = 10500000 bits
> > >      /8 = 1312500 bytes /(1024*1024) = 1.26 megabytes.
> > >
> > > or
> > >
> > >    100 Mbps is 850K
> > >
> > > and see if that improves things.  It may be that something can't
> > > handle even that much back-to-back when they are sent at 1000Mbps.
> > >
> > > There are also bwctl (<http://e2epi.internet2.edu/bwctl/>) servers at
> > > Internet2 router nodes, for a different way to split the problem
> > > (essentially run iperf to the core).
> > >
> > > --Matt
>
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