Strange slow networking - unidirectional
Posted on 2001-08-21
I have two machines:
NT Server 4.0 SP6a
DLink DFE-538TX 10/100 NIC
NT Workstation 4.0 SP6a
Realtek RTL-8139 10/100 NIC
The machines were connected via a 250 foot long cable with a non-switching hub in between. Apparently communications were so slow that they were unusable. The hub was removed and the cable was changed to a cross-over cable, with no effect. The cable was ripped out and re-run. After it was re-run, a professional analysis was done on it, showing perfect available bandwidth, impedance, etc. So the cable is not the problem. This is when the problem was dumped in my lap.
Upon further investigation, I discovered that the problem only existed in one direction. Transferring data from Machine B to Machine A worked fine. A 6 megabyte file, transferred from Machine B to Machine A (either from command prompt via a network share, Explorer, or FTP session logging into IIS on Machine A) completes in a couple of seconds. However, transferring the same file from Machine A to Machine B takes upwards of 45 seconds.
The only network installed is TCP/IP. Bindings are Windows default bindings.
Pinging either machine from the opposite machine works perfectly. However, if the packet size is increased:
ping -l 4096 machineb
...it begins to drop packets. If the packet size is increased to 10240 bytes, approximately 95% of the ping packets are dropped.
Running a network analysis tool shows that there are no problems with the network packets themselves - no runt packets, no CRC errors, nothing - everything looks just perfect.
Changing the NICs from AUTO to 100 mB Full duplex/100 mB Half duplex/10 mB Full duplex/10 mB Half duplex has no effect.
All NIC drivers are the most recent versions available, and I did attempt to uninstall and reinstall them as well as re-applying SP6a on both machines. Nothing had any effect.
DLink tech support doesn't think it has anything to do with them or their drivers. Unfortunately, the machines are off-site (out of the country) and the only access I have to them is via PCAnywhere, so swapping NICs or plugging a laptop in to one of them is not an option.
Anyone have any suggestions?