From: talon57@well.com
Date: Tue, 23 Jul 1996 16:06:47 +0800
To: cypherpunks@toad.com
Subject: Re: ABC news on Internet Telephony
Message-ID: <199607222103.OAA08425@well.com>
MIME-Version: 1.0
Content-Type: text/plain



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Since this thread has continued I would like to start my comments
by making a public apology to David Sternlight for my bad manners
the other day. He had done nothing to give me cause for my bad
attitude. I was rude and expressed myself poorly. I apologize to
him in particular and to the list in general.

Brian D Williams

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Digitally signed apology ^^^^^^^ pretty neat eh!

Remo Pini wrote:

>--- all the following points are based on swiss circumstances, >
>they may not apply to US ---

A good point, my views are based/biased by being a Chicago based
Ameritech (RBOC) employee.

DISCLAIMER: all opinions are my own, I do not speak for Ameritech
or it's alliance partners. 


>>point to point circuits are more efficiently handled by circuit
>>switching rather than packet switching networks. Nicholas
>>Negroponte wrote an interesting piece about asynchronous vs
>>synchronous, I believe it is in his book "Being Digital." 

>Well, from a users point of view, sending packet data over a
>packet mode bearer service is more efficient (and cheaper). An
>interesting developement in this direction is the PMBS-A/B modes
>of ISDN (packet switching to the public switch). The existance of
>this service suggests its usability.

 I agree 100%, I expressed this poorly. I meant to say that
asynchronous packet data was more efficent over a packet network,
and synchronous data (like voice) was more efficient over a circuit
switched network. I share your admiration of ISDN.

>>ADSL is an interesting attempt at digital telephony but expensive
>>and basically would mean replacing existing central office
>>switches. (backbone bandwidth) 

>We have a well developed DQDB-MAN and ATM net around, and
>bandwidth is available (and getting cheaper by the minute).
>Currently, a onetime investment of around $2500 per client is
>necessary to provide 5MBit/s transfer volume (via the cable TV
>networks or the existing broadband networks)

One of the problems with a conversion to ADSL here would be that
most point to point copper has been replaced with "slick 96" muxes
which use 4 framed T-1's (1.536 mbs) to provide 96 voice channels.
It is difficult to run 6mbs over a 56kbs channel. ;) Of course this
equipment could be replaced. (maybe just new line cards!) The good
news is that it is fiber based. 

>>In a packet network you have to either dedicate a portion of the
>>bandwidth for a synchronous circuit, or you have to have a very
>>fast network and use very small packets (ATM), expensive either
>>way.

>Not if you have a dedicated packet switching network for
>asynchronous packet transfer only. If you use it for both you
>don't have to have a very fast network, you have to have a network
>with predictable and constant packet delay. (that's not the same
>as fast!)

You are correct, actually fast is always the wrong term to use
since we are always refering to a portion of the speed of light.
Because of different technologies and bandwidth some devices have
faster data throughput.

>>A single central office has many times the bandwidth of the
>>widest part of the internet, and the average state has hundreds
>>of CO's. If even a small portion of the Internets current users
>>tried placing a call things would grind to a halt. A huge
>>increase in the number of backbones and their bandwidth would
>>solve this, but who will pay the bill? 

>I guess Internet-telephony is one of the bandwidth killers.

Yes, this is the point I was trying to express.

>>Sometime ago the discussion was on the cost of laying new fiber,
>>may I suggest  the realworld heuristic of "a million dollars a
>>mile."

>There are of course a lot of alternatives:
>- Existing wiring (5 MBit/s over 6 copper wires is possible)
>- Usage of the cable networks
>- Radio transmissions (RITL - radio in the loop)
>- Satellite transmissions

Yes, we should always check the alternatives, but lets face it if
we have to redo the infrastructure, and redig 250 million trenches,
I feel 100% fiber is the way to go.

jim bell <jimbell@pacifier.com> writes

>>Sometime ago the discussion was on the cost of laying new fiber,
>>may I suggest  the realworld heuristic of "a million dollars a
>>mile."

>In most cases, "new fiber" isn't needed, and will probably only be
>rarely needed on long-distance links.  As I understand it, most
>cableways are laid with extra tubes, into which new fiber cables
>can be blown in (using compressed air) long after the trench is
>filled.  The specific example I saw, there were three 2" diameter
>tubes in a larger tube, and according to the contractor (I
>asked...) only one of the tubes would be filled at that time.  In
>addition, while he wasn't sure, he thought that at least some of 
>the 36-fiber cable in that one tube would remain "dark," or unused
>until it was later needed.

>I don't know how expensive it is to add that extra fiber cable
>into an existing tube, but it would be VASTLY cheaper than the
>original trenching operation.  Further, much of the improved
>transmission technology can be used on the older fibers to
>increase their capacity:  A fiber now used to transmit a single
>2.4 gigabit signal can be upgraded, simply using new channelized
>transmitters and receivers to increase the data rate to 8 or 16
>times the previous rate.

Jim, the above quote was by me not Remo Pini. I was giving a rough
figure for new underground fiber, and yes when we have to install
new we always lay extra tubes. The information your contractor
friend gave you was very accurate.

There is still a great need for new fiber, we are still installing
it at a rate of a billion dollars a year.

Brian
Sacred cows make the best hamburgers.