Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site ttidcb.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!cmcl2!philabs!ttidca!ttidcb!jackson From: jackson@ttidcb.UUCP (Dick Jackson) Newsgroups: net.dcom Subject: Experience with 9600 bps on Dialup Message-ID: <266@ttidcb.UUCP> Date: Thu, 7-Feb-85 12:14:31 EST Article-I.D.: ttidcb.266 Posted: Thu Feb 7 12:14:31 1985 Date-Received: Sun, 10-Feb-85 03:52:43 EST Organization: TTI, Santa Monica, CA. Lines: 37 This is a sort of followup to the request for info re dial up modems at 4800 and 9600 bd. (I don't have the patience to figure out how to do a "followup"). We recently tested regular 4-wire 9600 bps modems from three vendors between Santa Monica into Huntington, Long Island. The modems were: General Data Comm 9600 QP (EP has same transmission system and is virtually equivalent), the UDS 9600 A/B (the regular 9600 has similar transmission circuitry) and the Codex 2660 (14.4 kbps with Trellis). Of course we had to make two dial calls using DAAs (sometimes bundled into various dual-dial auto answer units - every vendor has his own version). The one you'd think worked best - did! The worst showed about a 10 times worse block error rate. But! worst worst was good enough so that any self-respecting link protocol could take it in stride, i.e. less than five block errors per minute (511 bit blocks). About every five call attempts the connection was so bad (BLERT counter berserk) that an abort was necessary. Remember that we were dialling two lines, so its really about 1 in 10 switched circuits called. The signal quality light on the modems by the way provides a fairly good indication of go/no go. If it was anything but steady the block error rate was approaching what I considered uncomfortable to unnacceptable ~ 3-10% retries. (BLERT tests were done with the remote modem in loopback.) The path we used is probably not the worst you could pick but is fairly testing. Santa Monica is General Telephone country. The lines probably have to pass through Pactel before hitting ATT&T (anyone know?). Then they have to get around the NYC mess at the eastern end. In a nutshell, our experience says - Go for it, it will probably work.