At 5:35 PM +0000 6/21/03, The Road Goes Ever On wrote:
>""John Neiberger"" wrote in message
>news:200306202054.h5KKsG2Z005168@xxxxxxxxxxxxxxxxx
>> We use ISDN for dial backup where DSL is not available and we need more
>> bandwidth than a standard modem connection would provide, which is a lot
>of
>> locations. It seems that there is a lot of ISDN out there and plenty of
>it
>> being ordered, but I might be mistaken. I'd love to get rid of it
because
>> it has too many quirks. :-)
>
>
>just my two cents, but ISDN is one of the old and arguably obsolete
>technologies that still is quite relevant today. I prefer to sell RLAN ( ATM
>host and DSL spokes ) but when the customer requires relaibale backup, ISDN
>is always the choice. Happens a lot because although DSL is generally very
>reliable, when a link develops troube it still can take a long time for a
>telco to get around to fixing it. Sometimes over a week, in my experience.
>
Another two cents, but I strongly recommend studying X.25 and ISDN
simply for the background they give for other protocols. I don't
think, for example, you really understand FR until you understand why
and how that it was stripped down from X.25, and was also designed as
a low-speed access protocol to ATM. Understanding Q.931 leads to
better understanding of Q.931, and, especially if you also look at
Q.932, helps you understand motivations for IP telephony protocols.
I was developing some AVVID courseware and found it extremely useful
to present the ISDN reference model that the students _thought_ they
knew, and then started filling in the blanks that are usually skipped
in pure data instruction -- such as an NT2 being the prototype for a
PBX. Also usually skipped are anything going beyond (toward the
carrier) the NT1.
It turns out that the ISDN conceptual architecture has quite a number
of interworking abstractions of what goes on in the "cloud", which
again can help in understanding what IP telephony has to do.
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