From: varney@cbnewsd.cb.att.com (Al Varney)
Newsgroups: comp.dcom.isdn
Subject: Re: ISDN international tariffs
Date: 31 Dec 92 17:57:56 GMT
Organization: AT&T Network Systems, Lisle, IL

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:
>>>In article <1992Dec19.214534.3982@cbnewsd.cb.att.com> varney@cbnewsd.cb.att.com (Al Varney) writes:
>>>>   Where is 7500 cps from???  You should get 64000 bps / 8-bits/c
>>>From the USA'a 56kb "digital" services - look at the rest of what you write.
>>1.  The quotation marks on the word "digital" are somewhat inflammatory -
>>56k switched digital services are just as digital as 64k switched digital
>>services.  They're not ISDN, but then, they don't claim to be.
>
>Then why mention them?  (Sigh) *You* brought them in...

   Actually, *I* brought it up -- sort of.  But then I thought you
were asking non-rhetorical questions, and really wanted technical answers.
I guess I was wrong (Sigh).

>>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''??

   The point is that you don't have an end-to-end 64k circuit, do you?
David was (I think) attempting to indicate that a request for 64k data
will fail if such facilities are not available at each point in the
switching path -- pretty obvious, I guess.  And (I think) your point
was that everything was digital (64k) end-to-end for a voice call, so
why should data cost more.  And (I know) my point was that every possible
circuit on an arbitrary voice call might NOT BE 64k, and that it costs
time, labor and software to insure that 64k data calls are ONLY ROUTED
over facilities that can carry such traffic.  The alternative is to
use time, labor and hardware to upgrade ALL facilities to 64k "clear
channel" operation, so that all calls (voice or data) would traverse
such paths.  For international traffic, where end-point compression
and other methods can place 2N or more voice calls on N expensive
64k-equivalent circuits, it is clearly reasonable to charge more for use
of a full, 64k-tested channel.

>>>>>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!

   So "your" switch has the hardware/software to support ISDN on every
line, even if you only want to service (say) 100,000 simple analog lines?
Aren't your customers upset at paying for all that extra power/hardware
or is it a captive market...?  Has this wonderful interface been documented
in a technical journal, or at some conference?  I'd really be interested
in some detail, and I'm sure others would also.

>>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...

   Gee, I guess I'll just say the above comments are just MY opinion,
and leave it at that.  But I am confused -- I thought your original
questions had to do with the facilities required BETWEEN switches, after
the ISDN-to-CO interface.  If you really want some answers, maybe you
should re-state the questions in light of the comments to-date.  If you
just want to argue, how about e-mail?  And if you just want to posture
in public, I'll help by getting off the stage.

Al Varney
Newsgroups: comp.dcom.isdn