Check the event view for message Event ID
4226 (Event Viewer, under System - look for TCP/IP Warnings saying:
"TCP/IP has reached the security limit imposed on the number of
concurrent TCP connect attempts) message. If found, the
problem is due to windows limiting the number of incomplete socket
connections made from a single system that can be created. This is
a capped at to 10 per second.
This problem seems to manifest itself where there are a large
amount of connections on a system (i.e. 20 or more IO devices using
TCPIP for a transport protocol). Once all connections are made then
it should be possible for your system to perform at a normal level
as the problem only affect incomplete connections.
The reason for this limitation is to reduce the risk of an attack
by worms and spamers by reducing the amount of random connection
that a single computer can attempt to open. A patch is available
from the web site
http://www.speedguide.net/read_articles.php?id=1497, it should be
noted that this is not supported by Citect and Microsoft as it
involves making a change to one of the core networking files. The
problem does not effect the Windows 2003 server or windows XP
sp1.
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