Thanks, John. I'm quite familiar with the cobweb situation. _smile_ Actually, you painted a picture that I could relate to. At about the same time (back in 1991) we did some colocation designs for some Japanese telehouses in Jersey City. Their engineers and architects set up shop on site to work with us. I do not recall a single computer in their area at the time, with the possible exception of the receptionist's unit.
But getting back to ISDN...
"However the access layer of ISDN even then seemed temporary."
Yes, but I think it's notable that ISDN and its remnants will be with us for quite some time. It's the standard unit of trade in PBX trunks these days (PRIs). Even where overflows to the PSTN from VoIP gateways are concerned.
And video conferencing, even over IP applications (VoIP, for example), continue to use H.323 in gateways. And H.32x protocols were originally used to support multimedia over ISDN to the desktop or room-sized conference terminal. As they still are, even in the IP mode.
Actually, traces of ISDN primitives can be found in a large number of applications and have become engrained in networking in many inconspicuous ways, if you think about it. Where it is waning is in its original Basic Rate Interface form, to end users of Internet Access, but it continues to thrive and multiply, elsewhere.
ISDN received an unexpected boost about eight years ago as a backup for Frame Relay Loops, and then as backups for Internet Access services. ISPs use it to recover downed dedicated links and as auxiliary spare capacity on demand.
The latter types of apps [for Frame Relay backup, especially] are not very glamorous, so no one ever speaks of them, but there are hundreds of thousands of BRIs out there (millions?) that don't do anything except backup corporate Frame Relay loops in out-of-the way applications. On that note, there are hundreds of thousands of ATM (Teller Machine) sites that employ ISDN that no one ever speaks about, either.
There are probably more ISDN lines in these and similarly obscure applications, alone, than all of the Cable Modem and DSL lines to date.
Notably, even where HDSL and SDSL are being installed in the latter teller machine applications to replace Frame Relay, due to the enhanced bandwidth of HDSL that make it possible to support additional banking and other applications, the ISDN backups remain to support basic services at a critical level of operation.
Didn't mean to go on about this, but typing these items out served as a sort of review for me, as well. Thanks for being an excellent sounding board for this review. _g_
FAC |
