Terminal Session Question!

Hello!

I have a terminal server in a site which is not in my LAN...and when from my LAN computers i work in a session to the terminal server....without any reason the session is cutting off.when I sniffered the port of the server i saw this:

"TCP DUP ACK 8785#...."
"TCP Previous segment lost"
"TCP retransmission"

who can help me with it?

thanks

The source - destination addresses, ports and times match those of your connection, right?

If so, then it I guess that this TCP DUP ACK message might refer to the reason of the problem. Still, TCP DUP messages are not something critical, they are just notifications that one of the packets sent lost it's way and should be sent again with the TCP sequence specified on the message -packets get lost and retransmited all the time. Of course too many of these in a short time would betray a problem -i.e. that some router(s) in-between can not handle the traffic well. It would help if you provided some more information.

PS. Are you sure there is no other reason for the disconnection, like leaving your terminal idle for some time?

well....the terminal server and the terminal clients are in a different LANs, cisco routers (1700 and SOHO) are connecting the LANs!
the problem is that i reacieve the TCP DUP ACK many times like this:


"TCP DUP ACK #1"
"TCP DUP ACK #2"
"TCP DUP ACK #3"
......

and all this for the same packet!
I guess that that is why the sessions cutting off!
if so...what should i do?

thanks again

I have no personal experience for that exact thing, but I think some reasonable suggestions would be to first check whether there is a pattern for those DUPS, if they occur randomly all the time or they only occur in specific cases -like connections to your terminal server-, to see whether there is technical problem at some part of your networks (i.e. bad cabling) or it is a problem caused by bad router configuration. If you can exclude the first possibility, then you should check thoroughly any configuration rules that match the connections where the problem occurs, i.e. to see whether one of the routers silently drops the specific packets for filtering reasons. I also don't know what logging capabilities your routers have, but that could shed some light by telling you whether the questionable packet arived at each router and what happend with it.

First I want to thank you for your quick answers!
I almost convinced that the problem is one of the routers or both of them... do you know some commands (of cisco router) that can help me to find the problem? because i don't familiar with commands. thanks

Sorry, personally I can't help with cisco-specific information as I have never used cisco's IOS. Still you should find enough documentation about this on the web (i.e. tutorial 1 , tutorial 2 , tutorial 3 )