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UDP checksums fail with basic inetd services at high rates


I have to prove the bit error rate of a network and wanted to simply
send a couple of Gigs to the echo port of a remote computer and compare
the /proc/net/snmp values for Udp:InErrors and Tcp:InErrs which, according
to my information, count the incorrect tcp/udp checksums.

Sadly while playing around with iperf[1] and sendip, I saw that the error
numbers are raising with even 1/s when using more than say 100kbit in a 
normal switched FastEthernet. 

Does inErrors count something different/additional than header checksums?
I would have expected some dropped packages due to congestion but not
incorrect packages?!

I tried inetd and xinetd on 2.4 kernels and even using the echo service of
a cisco router. (the router reported no problems, just my linux host)



[1]: iperf --interval=10 --port=7 --udp --bandwidth=1M --num=1200M -c host

Christian Hammers    WESTEND GmbH - Aachen und Dueren     Tel 0241/701333-0
ch@westend.com     Internet & Security for Professionals    Fax 0241/911879
          WESTEND ist CISCO Systems Partner - Authorized Reseller

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