Discussion list for thrulay, a network testing tool

[stanislav shalunov <>]

Yee-Ting Li 
<>
 writes:

> #(ID) begin, s   end, s  Mb/s    RTT, ms: min  avg     max
>   ( 0)    0.000    5.001   31.334   82.304 3405.275 4934.103
>   ( 0)    5.001   10.001   93.968 5015.022 7633.145 9678.344
>   ( 0)   10.001   15.001  146.852 10035.642 12392.504 14508.290
>   ( 0)   15.001   20.001  175.368 14858.923 17195.312 19471.865
>   ( 0)   20.001   25.000  199.296 15123.740 17989.805 20905.669
>   ( 0)   25.000   30.001  218.963 13345.205 14168.544 15325.002

Yee,

It looks like you're seeing the dreaded Linux internal buffering.
(There's no good reason Linux should buffer 10-15 seconds worth of
stuff, but sometimes it does.  When this happens, TCP also becomes
more sluggish---perhaps there's a queue scan somewhere inside the
kernel, but that's just a guess.)  Thrulay reveals it, but doesn't
cause it.  Can you try running a single stream with window sizes of
10-25-50-100MB (so that the window size is more in line with
throughput*delay)?  If it does better, it might help to reduce
IP-level queuing and/or driver buffers.

-- 
Stanislav Shalunov              http://www.internet2.edu/~shalunov/

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