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Old 08-07-2008, 03:18 PM
"Emmett Hogan"
Default Debian server NOT responding to SYN packets (randomly)

Hi Folks,

I am seeing some extremely strange behavior between my
front end webserver (Sun Java Web Server V7.0U1) on Solaris 10 and a
JBoss Server (JBoss 4.2.2) on a Debian box).* Every once in a while,
the web server will have a connection time out with the jboss server
(which is part of a 3 machine pool) and the webserver will rightfully
shunt that server's load over to one of the other jboss servers,
however...this session switching forces our users to have to
reauthenticate, as the session data is not shared between jboss
machines.* The web server will then continue to redirect all traffic
for the "down" web server until the health check thread runs again on
the web server and it sees that the jboss server is not really down.

Well, after much searching, we have discovered that on those
connections that time out, there is no response from the jboss server
to the SYN packet sent from the web server!!!* We see it leave the
webserver (via snoop) and see it arrive on the jboss server (via
tcpdump), but no SYNC/ACK is ever returned!* During a "good"
conversation we see all the appropriate handshaking and data transfer
just as we'd suspect.

Has anyone else here ever run into this situation?* I did look at
the individual SYN packets, and there is no difference between a "good"
SYN and a "bad" SYN...they look the same.

In a word....I need "HELP"!

Thanks in advance!


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