hingston@apple.com (Joe Hingston) (02/24/90)
What is going to be the common (and/or correct) way to interwork ISDN terminals with services that are modem based? I am thinking of personal computers with ISDN as a built in feature, or with an ISDN add-in card. I can think of a couple of obvious ways, but do not know which will be used, or indeed if some totally different means will be used. 1) The ISDN terminal will have a standard modem sitting behind a codec. As far as the network and the service provider are concerned ISDN does not need to exist. 2) The ISDN terminal will use some form of rate adaptation, similar to V.110. But then who converts the rate adapted bit stream to modem tones? The phone company? A third party? 3) Almost the same as 2), but instead of bit rate adaptation data is sent as HDLC frames. This raises the same questions as to who converts the frames to tones. Are the RBOCs allowed to do the rate adaption, or does it fall into the category of protocol conversion? Will there be pools of Rate Adaptors, similar to the modem pools that currently exist? I hope these questions make sense, if not please feel free to suggest new questions. A screaming comes across the sky" T. Pynchon These statements in no way reflect Apple opinions. Joe Hingston (hingston@apple.com)
gnu@toad.com (John Gilmore) (03/01/90)
hingston@apple.com (Joe Hingston) wrote: > 1) The ISDN terminal will have a standard modem sitting behind a > codec. As far as the network and the service provider are concerned > ISDN does not need to exist. Even better -- the ISDN terminal can have a SOFTWARE modem implementation and a SOFTWARE codec. Why add hardware just to talk to old equipment? Certainly a low speed (<= 2400 baud) modem should be doable on today's CPUs. If you have a DSP, the whole ball of wax up through Telebits is no problem. Actually the ISDN end will be aware that ISDN exists. But it will dial into a 'voice' line on the other end that happens to have an old style modem attached to it, in the same way that an ISDN voicemail system might call a voice phone to forward a call to you. The other end will just think it's talking to a standard modem. No phone company politics, 'rate adaptation', etc needed. Of course, anyone with the right computers could offer such a service to the public -- e.g. you phone me with ISDN protocols, I phone somebody else with old-modem protocols and relay the data. It could even be done in its spare time by your IBM PC on a single phone line (since a single ISDN line has two 64kbit data channels that work independently).