ndt-users list created

[Jim Cotton <>]

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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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