With a DS3 serial interface (45mbps) I've never gotten a clear understanding if in reality there is 90mbps of actual available throughput since this is a duplex type connection. I guess the question also relates to T1. If one were to jam full T1, or DS3 traffic down both directions is the total through put a T1/DS3 or twice a T1/DS3. IOW, can you send 45mbps at the same time receive 45mbps?
I have this problem too.