loosing packets

Rick Jones rick.jones2 at hp.com
Wed Apr 19 23:20:05 UTC 2006

Tom Schmitt <TomSchmitt at gmx.de> wrote:
> Most times a DNS-request is answered properly, but sometimes you'll
> get a timeout instead. I looked into the problem and found that I'm
> loosing UDP-Packets (UDP-Buffer-Overflow). Looking at "kstat -p
> ip:0:ip:udpInOverflows 10" showed me, that I'm loosing about one
> packet out of 100.

> Increasing the Buffersize from 2 MB to 4 MB didn't change anything.

Are you certain that named isn't making a setsockopt() call of its own
to set the SO_RCVBUF size?  Might want to fire-up truss and trace the
system calls being made at startup.  Unless there is another way to
see the SO_RCVBUF size of a given socket.

> Googeling for this problem brought the suspicion, that the load is
> too much for the server so it cannot handle all the requests. So I
> tried to confirm this suspicion: I did a load-test with queryperf
> and put ten times of the normal load on the server, doing more than
> 100 thousend queries in about 25 seconds. But what did I see? There
> was no increase of packet-loss. Instead, in this short period of
> time, there was not one single packet lost. So it seems to me that
> this is not a simple load-problem.

How many queries did queryperf have outstanding at one time?  While it
may indeed be something else, one has to make a distinction between
servicing a steady-state load and the size of a burst that can be dealt

Was your queryperf load from one system or many?  From how many
different systems does your production system receive load?

rick jones
oxymoron n, Hummer H2 with California Save Our Coasts and Oceans plates
these opinions are mine, all mine; HP might not want them anyway... :)
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