RE: ABC news on Internet Telephony

[jim bell <jimbell@pacifier.com>]

At 12:37 AM 7/21/96 +0200, Remo Pini wrote:

>>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.

Potentially.  However, there has been some mention of a new standard for 
voice compression that puts voice into 2400 bits per second, a factor of 
about 25 lower than the phone company normally uses. (They use 8,000 samples 
per second at 8 bits per sample, companded.)  At that rate, a pair of 
modern, 2.4 Gb/s fibers could handle 1 million simultaneous phone calls.  
Since some of the newer fiber systems put 8 or more separate channels down a 
single fiber, that would work out to 8 million conversations.

I have to conclude that we shouldn't even be close to running out of 
Internet capacity, _IF_ it were driven by state-of-the-art fiber and 
similar-speed switches.  But it probably isn't.  At best, Internet probably 
only gets a fraction of the capacity of a given fiber wherever it flows.  
This will have to change.


>>TANSTAAFL
>>
>>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:

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 Bell
jimbell@pacifier.com