About 20% of our connections at 2400. 1200 connections are less common, about about 3% of calls. We do support down to 300 in case you want to fire up that old CP/M machine, but I've not seen a 300 baud connection.
Looking at the 19,200 connections, these apply equally to 28.8, 33.6 and 56K modems; there is no advantage or disadvantage to any of these speeds if your phone line won't connect faster. The modems could have been programmed to connect faster, but that would substantially reduce performance.
See (Modem Init. Strings) - Max Speed for more details.
The Microcom modems have an adjustment for throttling them back. This will increase throughput, but lower connect speeds by about 2400. We intend to do so but only after testing. I have a pretty clean phone line and will use file transfer speeds to measure this.
Commercial ISPs and manufacturers of modems for consumers have an incentive for seeking a higher speed. They are selling speed and the higher numbers look nice. Since we are trying to transfer data more efficiently, we can allow the modems to seek a more optimum connect speed.
56K lines require a digital line at one end, which is at the ISP. Most of these use 56K modems, but the system works equally well with 33.6 modems. The user of course has an analog POTS line. While connect speeds in excess of 33.6 are often seen, it is likely that 33.6 or lower is optimal, so there is no advantage to using a 56K modem for such connecitons. (SCN does not have these digital lines.)
Stan Protigal bk269_DELETE_THIS_TEXT@scn.org http://www.scn.org/~bk269/