OT: Advice needed on dialup problems - TCP corruption? (windows users)

        I am seeing a strange problem on my network lately after adding a new terminal server, a Lucent MAX TNT with madd modems in it. The symptoms are that users can connect, they can ping and traceroute without any trouble. Anything that is TCP based however is failing. In some cases, disabling software compression fixes the problem for a short period of time. I am not experienced enough with the MAX TNT units to know how to debug the TCP packets as they come from the user. I am running 10.0.0 TAOS on the unit. Can anyone please offer some advice or suggestions? I am too young to go bald :slight_smile:

It sounds like Van-Jacobsen TCP header compression is broken in the TAOS software release you're running. That would explain why UDP traffic works just fine, but TCP does not, since VJ compression only compresses the TCP header. VJ header compression is a PPP negotiated option. Almost all dial-up clients try to negotiate it by default, but turning it off is problematic on the client (as you have discovered), and not feasible when you have thousands of clients.


1) Find a version of TAOS where VJ compression is not broken
2) Although I have never done it on a TNT, you can usually configure a terminal server to refuse to negotiate VJ header compression. This would be a reasonable work-around until you can do (1).
3) Replace the TNT with a Cisco RAS. At the very least you get excellent debugging facilities for situations like these and a better connect success rate.