OK, please see the attached drawing.
Basically we have a DS3 and are switching to Metro Optical Ethernet, AKA Ethernet over Sonet, for performance, cost and multiple access.
Problem is that traffic from Denver to Colorado Springs is working perfectly, while traffic from Colorado Springs to Denver is very slow, 3-4mbps.
I am doing my testing with iperf and ttcp, testing all possible combonations of the servers listed there. All of the COS servers test to eachother (locally) at 90+mbps, all of the Denver servers test to each other at 90+mbps. This indicates that the machines -can- put out 100mbps reliably.
I have verified that all switchports involved are 100/full. I am taking no errors on any switchports or server interfaces.
Our LEC came out with a sweet tberd-like device and was able to put 100mbps across the link and receive the same (tried loopback + head-to-head) without issue, at MTUs ranging from 1400 to 1522. It all comes back 100% and clean.
I have tried everything, from adjusting TCP recv windows, tweaking MTUs. I have tried bypassing the switch on both sides, one at a time and simultaneously. I am totally at wits end, and have no idea where to go from here. Any suggestions would be very appreciated.
