From: deej@cbnewsf.cb.att.com (david.g.lewis)
Subject: Re: ISDN international tariffs
Organization: AT&T
Date: Tue, 22 Dec 1992 13:51:19 GMT

In article <BzMw6A.Jzr@jshark.inet-uk.co.uk> joe@jshark.inet-uk.co.uk (Joe Sharkey) writes:
>In article <1992Dec21.143921.20121@cbfsb.cb.att.com> deej@cbnewsf.cb.att.com (david.g.lewis) writes:
>>In article <BzKv7n.G82@jshark.inet-uk.co.uk> joe@jshark.inet-uk.co.uk (Joe Sharkey) writes:

>>2.  The original poster was referring to a 64kb/s B-channel.  I am guessing
>>Al assumed 64kb/s end-to-end, since the original poster made no reference to
>>rate adaption to 56kb/s, and current standards state that a call with bearer
>>capability/user service information of 64kb/s UDI, no rate adaption, can be
>>cleared by the network if no 64kb/s clear channel facilities are available.
>
>Want to translate that to American?  ``If I can get an end-end 64k circuit,
>then I've got an end-end 64k circuit''??

Sorry; I tend to lapse into Standardese sometimes... The original poster
talked about comparing 64k Unrestricted Digital Information (UDI) on a
B-channel with speech or 3.1kHz audio information (a modem) on a B-channel,
analog loop, trunk, what have you.  Later, however, he used a figure (7500
cps) which seemed to be more appropriate to 56kb/s data, instead of 64kb/s
data.  However, if user equipment attempts to setup a call with a bearer
capability of 64kb/s UDI, and the only facilities available are 56kb/s,
current standards state that the network can clear the call.  So if a user
is talking about comparing a 64kb/s connection to a modem connection, he's
talking about a 64kb/s connection, not a 56kb/s connection.

>>>>>Are there other costs to the telephone company involved that
>>>>>already has ISDN capable equipment that can in any way justify
>>>>>the extra cost of ISDN?
>>>No. In the UK, ISDN comes in after the codecs, so there is *no* difference.
>>>Q: Why should I pay more to use *less* of your equipment?  ;)
>>
>>Because you're not using less of my equipment.  Even looking solely at the
>>line interface - where your "codecs" are - there's more "equipment"
>>(hardware and software) for an ISDN interface than an analog loop.  An
>>analog loop doesn't require a three-layer protocol stack to terminate the
>>loop...
>
>You're being silly!  Well, maybe AT&T don't know how to design switches!

We could talk about how the 4ESS implements PRI, but that's not really
relevant to BRIs...  The point is, the amount or complexity of the equipment
is something of a red herring.  Everything's going to be on a board (or
less), and a large amount of that is going to be LSI/VLSI, so the only real
issue is how many of the things you make across which you can allocate the
development cost.  If a switch vendor makes 50 million analog line cards and
500,000 ISDN line cards, it doesn't matter that the analog line cards have a
codec built in -- the volume difference is going to drive costs far more
than the difference in functions.

>>Disclaimer: It's not really my equipment, since my part of AT&T has nothing
>>to do with ISDN BRI...
>
>Claimer: I worked on these 15 years ago...

Further disclaimer: I often discuss things of which I have very limited
knowledge.  I don't know why I do it; maybe I just like to get into
trouble... :-)

David G Lewis                              AT&T Bell Laboratories
david.g.lewis@att.com or !att!goofy!deej     Switching & ISDN Implementation
Newsgroups: comp.dcom.isdn