Information about http://www.glennf.com/pdfs/bump.pdf
By Glenn Fleishman …
Tags: acceleration, cable line, demodulators, digital information, ditch, early adopters, full speed, future ways, future years, glenn fleishman, high bandwidth, infobahn, information superhighway, internet feed, prognosticators, pulses, speed bump, term limitations, voice telephone, webspy,Pages: 11
Language: english
Created: Fri Jun 28 14:39:37 1996
Display cached document
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
Page 8
Page 9
Page 10
Page 11
By Glenn Fleishman WebSpy
Speed bump
Acceleration-ramp blues on the information
superhighway
The signs on the Infobahn say, "Full Speed Ahead" . . . but some bumps in the
road might send unlucky travelers hurtling off the edge and into the ditch.
While digital prognosticators see a future in which bandwidth is abundant
and cheap, more practical short-term limitations may put this vision five or
more years away.
So here's the real scoop on current and
future ways of getting bits over the pipe and
what we can expect from them--use these
details wisely, and you can be ahead of the rest of
the crowd of early adopters. It's important to
Issue #7 July 1, 1996 P A G E 1 / 11
SPEED BUMP By Glenn Fleishman WebSpy
remember, by the way, that for all the technologies I'm talking about here,
you're going to be paying one bill for your phone line (or cable line, or what-
ever it might be)--which is your physical connection to the Internet--and
another bill for the Internet feed you're running over that line--the ability to
send data. It's easy to lose sight of that when you're considering what high-
bandwidth Net access may cost in future years.
Modems
The end is here--already! Modems (modulator/demodulators) are devices
that turn digital information into analog pulses for transmission over the
existing voice telephone system. They started life at the 110-bits-per-second
(bps) level (also called baud back in those days), crept gradually to 1,200, and
then skyrocketed to the present top rate of 33.6 kilobits (kbps) per second.
But 33.6 kbps is faster than the carrying capacity of most voice phone
lines in the United States--that is, most lines can't accurately convey informa-
tion at that speed, and the modems have to "step down" to a lower-speed rate.
Issue #7 July 1, 1996 P A G E 2 / 11
SPEED BUMP By Glenn Fleishman WebSpy
A good chunk of American lines can't even handle data traveling at speeds
above 20 kbps.
The massive deployment of modems and fax machines and the subse-
quent increase in numbers of installed phone lines has also meant that local
phone companies are squeezed for actual wire back to the phone switches
that route the traffic where it needs to go. Telephone companies often install
devices that stack multiple voice signals on a single pair of wires. If 33.6 kbps is
the maximum that a full voice line can handle, obviously two modem
signals compressed over the same wire will handle half or less. The
quality of voice calls doesn't degrade much by this technique, how-
ever, which is how the phone companies can get away with it.
The fastest modems can talk at a lot of intermediate speeds, so
many people buy the top of the line so that they can always be com-
municating at the highest possible rate. But we'll never see faster
modems than today's over voice lines. Okay, you can never say
"never" in today's technological climate--but it's true anyway.
Issue #7 July 1, 1996 P A G E 3 / 11
SPEED BUMP By Glenn Fleishman WebSpy
ISDN
The great promise of the last several years for fast data access has been ISDN
(Integrated Services Digital Network). While you can read way too much about
this, the salient facts are: ISDN carries data at a speed of 128 kbps in two
separate 64-kbps channels, fully digital, for fees ranging from the cost of
regular phone service to hundreds of dollars a month, depending on your
part of the world and your usage (some ISDN is metered by the minute; peak
rates in other cases run from $25 to $180 per month for full-time usage).
ISDN is still hindered by the difficulty of configuring the lines, by regional
phone companies' lack of experienced field personnel to install and test lines,
and by a lack of service providers willing to give a user the full 128 kbps. It's
possible to set up a "virtual" 128-kbps link, but not many providers are yet
configured for that, and some ISDN devices' drivers don't yet support it (a
variant on the Internet's Point to Point Protocol allows the two channels that
comprise a regular ISDN line--which normally function almost as two sepa-
rate modems--to be "bonded" into a single virtual channel capable of using
Issue #7 July 1, 1996 P A G E 4 / 11
SPEED BUMP By Glenn Fleishman WebSpy
the full bandwidth for a single task, like transferring a file).
ISDN can also cost a bundle for an Internet feed that matches it--from $1
per hour for single-channel usage, to $500 a month for full-time 128 kbps. Not
really in the ordinary user's range, in other words.
Cable modems
Cable modems are supposed to take the sting out of the phone company's
limitations and costs. These devices would be plugged into coaxial lines
installed by cable companies, and could achieve speeds of hundreds
to thousands of kilobits per second.
The great problem here is that most cable companies'
systems are simply not up to the job of delivering data at that
speed. The difficulty generally starts at the distribution
points ("head ends") where the cable companies split
their signals into hundreds of separate lines that run
into individual homes. Everything might be fine up to
Issue #7 July 1, 1996 P A G E 5 / 11
SPEED BUMP By Glenn Fleishman WebSpy
these distribution points--though it often isn't--but from there to an actual
home, there's no guarantee of a decent, "noise-free" signal. So for all practical
purposes, most cable systems in the country don't have enough quality
wiring to use cable modems. If you want proof, walk outside and look up at
the pole where a bunch of coaxial cables are plugged into splitters; in many
neighborhoods, installations meant for three or four houses now serve many
more.
Another twist here is that although the devices might
have "throughput" of megabits per second, you would be
sharing the available bandwidth on that particular spur with
everyone else in the neighborhood. So prime-time Internet
usage might still only yield you modem-like speeds. No one
knows yet what the final cost per month might be for indi-
vidual users, but it will almost certainly be more than basic
cable.
And, since large-scale tests with cable modems are just
Issue #7 July 1, 1996 P A G E 6 / 11
SPEED BUMP By Glenn Fleishman WebSpy
beginning, this is all purely theoretical anyway. Cable modems are years away
from wide deployment--if they work.
ADSL
When ADSL was announced, Wired and several other computer publications
went berserk about the bandwidth--without noting that Asymmetric Digital
Subscriber Line technology required that phone companies install the equip-
ment on their switches, or that equivalent technology exists today at a cost
too high for consumers. (It is true, however, that ADSL requires phone compa-
nies to buy and install a lot less equipment than, say, ISDN.)
ADSL is asymmetric; that means that more data can go in one direction
than the other. The technology appears to support a data speed of about 6
megabits (Mbps) per second one-way and as much as 250 kbps in the other
direction. For home users, this would be perfect: you'd be retrieving huge
amounts of data, but not sending very much.
The biggest advantage of ADSL is that it runs over two wires, or a single
Issue #7 July 1, 1996 P A G E 7 / 11
SPEED BUMP By Glenn Fleishman WebSpy
"twisted pair," as it's called in the telephone biz. The vast majority of busi-
nesses and residences in the United States have wiring already installed that
would support ADSL. But, just as modem manufacturers had to forge agree-
ments on specifications before modems could be made that all "talked" to
each other, phone companies have to agree to standardize on ADSL technol-
ogy before it gets widely deployed.
Moreover, it hasn't been widely mentioned that, for two reasons, both
cost-related, ADSL is not really an appropriate consumer technology. First, you
can buy something very much like ADSL today, called HDSL (high data rate
DSL), which is what a T1 line runs on. T1 speed is symmetrical--1.544 Mbps in
both directions--and it requires two twisted pairs of wires, or four wires in all.
However, a T1 line costs anywhere from hundreds of dollars per month to
thousands, depending on both its distance from telephone company equip-
ment and the region it's in. That's a big bite, and there's no indication that
ADSL--which, remember, is similar in many ways--will be cheaper.
The other price issue is that what you pay for your feed to the Net is
Issue #7 July 1, 1996 P A G E 8 / 11
SPEED BUMP By Glenn Fleishman WebSpy
separate from the bite the phone company gets for carrying the data. A Net
feed at T1 speeds costs from $1,000 to $3,000 per month, depending, again,
on location.
ADSL may bring the cost of high-speed transmission down for busi-
nesses, but it's probably not a consumer technology for some years to come. It
will simply cost too much.
Where do we go but up?
The expense of getting a signal from consumers to services (and vice versa)
shouldn't be confused with a limitation on getting it from one service to
another. Bandwidth is ever-increasing and ever-cheaper (at least to some
degree) for the high-speed lines that buzz around the world. And technolo-
gies like ADSL will push the price down further.
A few exotic transmitters like satellites and wireless modems aside, the
real battle for the hearts and minds of consumers is going to be waged
between cable and telephone companies. Both have technologies that can
Issue #7 July 1, 1996 P A G E 9 / 11
SPEED BUMP By Glenn Fleishman WebSpy
bring the bandwidth home, but neither can deploy fully at the moment. (Of
course, dozens of independent telcos and cable companies are involved, each
with its own agenda; some are allied with media companies, which have their
own, separate, plans of attack.)
The ultimate arbiter will probably be price: the rush onto the Net either
caused or was abetted by the drop in modem prices and the rise in speed,
and the same may be true of the next wave of bandwidth technology. The
cheaper the service to start with, the more users at the outset, and--usu-
ally--the lower the price during the next phase, with competition and pur-
chases by all the early adopters pushing prices down even further for more
widespread sales. So whatever technology can drop in price fast enough to
be affordable by the average consumer could win the whole shmeggegeh.
Me, I've got a T1 line in my office. And an ISDN link into the house is
starting to sound, well, almost reasonable.
Continued
Issue #7 July 1, 1996 P A G E 10 / 11
SPEED BUMP By Glenn Fleishman WebSpy
URLS
An excellent resource for materials on bandwidth technology, with articles,
links to companies, and background information:
http://plainfield.bypass.com/~gzaret/hiband.html
A URL with great definitions of the terms used in this column:
http://www.sbexpos.com/sbexpos/associations/adsl/adsl_glossary.html
Issue #7 July 1, 1996 ©1996 Adobe Systems Incorporated P A G E 11 / 11