dgc@LOCUS.UCLA.EDU.UUCP (12/24/86)
The articles about ISDN (Integrated Service Data Network) are appearing
fast and furious. Yet I have seen little discussion of its potential
impact.
It appears that the service will appear, to the small user, as two
64 kilobit-per-second (kbps) full-duplex channels and one 16 kbps
full-duplex channel on each ordinary telephone line. One of the 64 kbps
channels would normally be used for voice, although it could be used for
data. The 16 kbps channel would be used for both signaling (presumably
replacing touch tone, etc.) and data while the other 64 kbps channel
would be entirely for data.
For large users, many more channels would be provided on one pair,
but these would be compatible with the above. Though the exact
configuration has yet to be determined (part of the standards-setting
still taking place -- the delay is apparently due to the differences
between the North American and European networks).
The telephone companies (BOC's and long distance services in the USA,
PTT's in Europe, etc.) would provide the switching for these services.
It seems that if this service were provided at a reasonable price and
if some reasonable sort of device that would permit RS232 to connect to
these channels were provided, then the current "audio-frequency" modems
would soon be obsolete. More than that, if the interface chips were
widely available and reasonably priced, the standard ISDN interface
could easily come to replace RS232 as the standard terminal interface.
Advantages would be the higher speed that could be used and a more
modern protocol (though I have yet to see the detailed specs).
However, judging by past experience, one might expect the telephone
companies to "kill the golden goose", most likely by so overpricing the
service that modem users won't want to switch. For example, one might
expect that there would not be a flat-rate service (given the opposition
to such services by BOC's), such as that which is currently provided to
many modem users. Even a "small" charge (5 cents/minutes) could mount
up quite rapidly. There are many other potential pitfalls. With any
of them, the service could die and we could be stuck with the present
system for another 25 years.
How should such a service be priced? What kind of performance
guarantees can we expect in terms of error rate, reliability, and
delays? What kind of protocols will it use? Will control be as easy as
the present system, which can be handled by simple intelligent modems
(Hayes compatible, etc.)? Will there be a wide availability of the
interface chips and will these be useful for direct terminal to computer
connection (without going through the telephone system)? Will services
such as TRW credit (which use automatic dialers and modems to validate
credit cards) quickly switch to the new service? Will it replace
slow-speed networks such as arpanet (why share the 64kbps arpanet when
you can have your own direct line just as fast)? Wil there be "airline"
style pricing where, highly-competitive, heavily travelled routes, e.g.,
Los Angeles-New York have much lower prices than much shorter, lightly
travelled routes? (This hasn't happened yet on long-distance services,
though I don't know why.)
dgc
David G. Cantor
Internet: dgc@cs.ucla.edu
UUCP: ...!{ihnp4, randvax, sdcrdcf, ucbvax}!ucla-cs!dgc