Program starts over WAN faster than it starts over LAN

[mcconmw]

In order to test the impact of running a specific application over our WAN, we put together a basic test. We connected two Win2000 machines together via their serial ports and set the speed to 115Kbs and then connected one of the machines to our network via a 100 Mb HD. We then started the application on the machine with the 100 Mb connection and it took 13s to start. We then went to the machine that was connected to the network via the serial port on the machine with the 100 Mb connection and started the application and it only took 6s to start. Obviously, this was not the results we had expected.

I disabled the serial connection and enabled fast ethernet on the machine that had previously only connected to the network through the other machine and tried to run the app again and got 13s again. I put a sniffer on the hub and ran through the original test again. The LAN connection stayed at 13s and the WAN connection stayed around 6s. I found in the sniff that packet exchange stayed slow but steady, fully using each second, from the WAN connection. When ran from the PC with the LAN connection, there would be a flurry of activity for a couple hundred ms and then there would be an extended period of inactivity for as long as 500-600 ms effectively wasting most of the second. I have checked for duplex and collision problems, but they look fine.
I am completely stumped at this point as to what could be causing this issue. Any suggestions\thoughts\solutions would be appreciated. Thanks.

Mike

 

[mcconmw]

Come on, I need theories even if they're notcorrect. I am very interested in any theories. Thanks.

Mike

 

[butchrecon]

This is only a guess but do you think it would have anything to do with the protocals used with the NIC? Are you using direct serial connection for the serial ports? In this case I think the protocals used for the NIC LAN could take a few seconds longer. Again I am sorta guessing.

 

[mcconmw]

We are only using the TCP/IP protocol. We used a wizard in 2000 to setup the serial connection as a modem connection. Going over this modem connection we expected slower or the same results not the faster results we have. One of our earlier assumptions was that the slower link was creating smaller packets or something similar, but our sniffer showed packet size to be very similar. Thanks.

 

[butchrecon]

With the serial connection going from port to port could have less overhead than TCP/IP protocal. Also does the TCP/IP connection have to be routed theough HUBS or SWITCHES?

 

[mcconmw]

The setup is PC A connects to PC B via the serial connection. PC B connects to the LAN via 100 MB HD connection to switch 1. This switch 1 connects to switch 2 at 1 GB. Switch 2 connects to the server at 1 GB. When the program is ran from PC A it is faster than when the same program is started on PC B. We have swapped hardware to ensure it wasn't CPU, RAM, etc. differences. I have monitored both switches for collisions and found them acting normal. The sniffs looked the same except for the long pauses inbetween packet groups when started on PC B. Basically, PC A takes the exact same path to the server except for the extra jump through PC B. Thanks, again.