The first thing I noticed during the echo test, was that the latency was much lower then the 286’s. That joy was short-lived, though. My outgoing sound path started having lots of jitter. The incoming sound was perfectly clear, but people would tell me my voice was breaking up. I could recreate this in the echo test. After a minute or two, the sound quality was pitiful.
Basically, it was a QOS problem. I tried setting the QOS properties on the 503, but it didn’t help. Even though my router had VOIP QOS settings, they didn’t seem to work. I replaced the stock firmware on my wireless router with dd-wrt, configured QOS, and the problem disappeared! I even performed a bandwidth download/upload test, and there was no loss of quality.
I’ll be porting my home phone number to my SIP trunk provider real soon:)