Subject: Re: bandwidth inadequacy ?

From: [email-masked] (Gary A. Nelson)
Date: Mon, 10 Feb 1997 15:50:40 -0600

Subramaniam Vincent wrote:

>I summarized a comment made at a seminar at USC, LA, last week as follows:
>
>"The telephone network was designed to maximize profits. About 10% (or
>very little) of the available bandwidth in the US telecom infrastructure
>is being used today. Hardware and communications cost is not really the
>problem. In other words, bandwidth was/is never THE problem. The Internet
>is also running on the same  telecommunication infrastructure. (telcos
>basically). There is scarcity because the telcos are  unwilling to use
>up more bandwidth, because they (want to?) would have to use telephone
>economics to price VBR type integrated services.  The bottom line is
>congestion on the internet TODAY, is NOT because of user demands, or poor
>resources. There is plenty of raw bandwidth available today. More
>realistic pricing/management structures have to come, and more
>competition possibly.
>
>The value  of research to resource allocation problems is moot in
>celluar networks, where we do have a technical problem" . End summary.

The speaker did not specify where this 10% utilization might be found. THe
telcos are groaning about the loading of central office switches, and they
are never operated at anything like 10% (more like 90% during peak busy
hour). If one inspects the copper access loops between the customers and
the switches, they are indeed very lightly occupied (how many minutes per
day are you on you phone at home?), but that is accounted for by
engineering the switches to concentrate traffic. There is far less capacity
in the switch than would be required to handle all customers placing a call
simultaneously. I don't think that 10% number is a meaningful claim unless
we look at those access loops.

There is a solution in hand called ADSL, HDSL or xDSL (Asymmetric Digital
Subscriber Line, Highrate, x = A, H, V etc) coupled with what the telco
call Digital Subscriber Line Access Muxes or DSLAMs. With these
technologies, the loops (wires between the customers and a CO) can be
operated at rates from ISDN BRI (128kb/s) to 384 kb/s, 768 or 1.5 Mb/s
symmetric, OR various asymmetrical speed combos like 1.5 downstream/64k up
to 8M down/640k up.

ADSL operates on a wire pair that is already carrying Plain Old Telephone
Service (POTS). The Internet traffic is peeled off by frequency division
muxing to the DSLAM so that it never gets to the CO switch. Only voice
traffic would go there. The protocols running over the wires include ATM,
HDLC encodings of ethernet packets, and HDLC/PPP.

The less ambitious numbers are available now and could be used to offload
*all internet traffic from the CO switches* AND provide lots of access
bandwidth for about the cost of ISDN (my opinion). There are trials going
on in many telcos, but real committments to spend big bucks seems to be in
short supply. Right now all the enthusiasm seems to be to get into the long
distance markets.
Interaccess in Chicago is the first company to offer Internet access over
ADSL  using pairs that they rent from Ameritech AND put their muxes in
Ameritech's COs. Still quite pricey ($200/mo for home, $1000/mo for a LAN),
but it's a start.
Gary

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