[toast0]

T1 time slots are 8-bits, samples are sent individually, with no packetization delay. There may be some delay between sampling and the time slot, and in a buffer when calls are connected between T1s and the time slots don't need to be matched up.

If you were calling into an x2/kflex/v.90/v.92 modem bank, that was hosted on a T1 (or larger), and v.92 could get 33.6 up, 56k (or so) down. It should be possible to recreate that with VoIP, but I don't know that anyone is that dedicated... anyway for end user modem to end user modem, 33.6 is the limit.

[bwann]

I recently tried this for making a YT video using an ATA with a USR Courier dialing into a ISP's POP in San Jose. V.92 flat out didn't work for me, but V.90 did. Surprisingly I was able get 50-53k downstream carrier rates, upstream was pretty lousy at 14.4-16.8k. The calls only lasted a couple of minutes before they were unable to renegotiate. 28.8k was much more reliable.