[netperf-talk] Question on UDP test

[Andrew Gallatin]

Jay Kim writes:
 > 
 > Hi, I have a simple question on UDP_STREAM test result.
 > I've got the following result, but I wonder why the throughput is measured only at client side.
 > 
 > UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.2.50.1 (10.2.50.1) port 0 AF_INET
 > Socket  Message  Elapsed      Messages                
 > Size    Size     Time         Okay Errors   Throughput
 > bytes   bytes    secs            #      #   10^6bits/sec
 > 
 > 2097152   65507   10.00         960      0      50.29
 > 2097152           10.00           0              0.00

It is measured at both the client and server side.  Your results
show that the server received exactly 0 datagrams.

The message size you are using (65507), when combined with with a 1500
byte MTU will lead to each datagram being fragemented into roughly 45
IP packets.  If just one of those is dropped, the reassembly will
fail.  The first thing I'd do is check netstat -s to look for problems
like this.

You may have better results using a datagram size (like 1472)
which will not require IP fragmentation:

netperf -H10.2.50.1 -tUDP_STREAM -- -m 1472 -S 2097152 -s 2097152

Drew