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									Subj: Cable as Fast Access to the Internet


TCOM 500: Networking--Technology, Protocols, and
Practice                                                     December 9,


                    Cable as a Fast Access to the Internet

                        by Dave Morris & Becky Schonfeld

       "People react to cable modems the way NRA members react to guns.
       You can take it away when you pry it from their cold, dead hands."

       -Marc Andreessen, vice president of technology and co-founder of
       Netscape Communications.


   *   High Speed Internet Access
   *   Cable Internet Access Architecture
   *   Advantages of Cable Internet Access
   *   Disadvantages of Cable Internet Access
   *   Cable Internet Access Trials & Standards
   *   Competing Technologies
   *   Conclusion

High Speed Internet Access

The cable industry has become a leading contender in the competition to
provide high-speed widespread home Internet access. Cable access holds
promise as it is a fast, almost-ready to market and relatively
means of communicating over a network. While the most advanced typical
users of today access the Internet at 28.8 Kbps, or perhaps 33.6 Kbps,
modems offer access at speeds ranging from 500 Kbps to as much as 27 (or
with products under development, 40) Mbps. The significance of this large
increase in network speed can be compared to the effect the automobile
The automobile made it possible to quickly travel distances that were
previously traversed on foot or horseback; in providing this 10-20 fold
increase in speed, it transformed society in ways that only a handful of
inventions have before or since. Similarly, a 15-300 fold increase in
Internet access speeds will transform the way in which people lead their
lives. Until now, web sites have been kept simple, consisting of text and
graphics that are usually under 30K. When the speed that cable (or its
competition) can provide is implemented in most households, web site
designers will have the license to routinely provide large video and
objects on their sites, allowing consumers to see, hear, and in a virtual
reality sense, try, what they are clicking on. The cable industry is
attempting to become a leader in this rapidly expanding service.

An example of the cable industry's commitment to the Internet access
is their effort to install free cable modems and Internet access to
nationally. On July 9th of this year, the National Cable Television
Association pledged to begin installing free cable modems in elementary
secondary schools as well as pay for their Internet access for one year.
They will begin in the 65 communities in which cable operators have
to introduce high speed Internet access, providing roughly 3000 schools
Internet connections. Fifteen of the largest cable companies are
collaborating in the effort to expose children to the Internet and the
with which it can be accessed. One of the companies involved, TCI,
a statement, "Obviously there are relationship benefits but this is not a
campaign of the day. Part of our commitment to the communities we serve
not just providing entertainment services but also providing access to
latest technologies."

Cable Internet Access Architecture

Until a few years ago, the cable television network consisted solely of
coaxial cable from the head end to the consumer's television. The head
is essentially a cable company substation that receives satellite and
terrestrial broadcasts and transmits them to each consumer's house. This
architecture, called tree and branch architecture, was designed for one-
data flow. While this works well for distributing the same signal to
multiple homes, it is not ideal for individulaized, two-way communication
Internet. An all-coax network has the additional disadvantage of signal
degradation over long distances, which requires amplifiers to correct,
adding more equipment that must be maintained to the network. About five
years ago, the cable companies began replacing their coaxial trunks with
fiber. Fiber has the advantage of carrying a larger-bandwidth signal
distances with less degradation than coaxial cable. Currently, the
of cable companies have hybrid fiber-coax (HFC) networks. See figures one
and two below for a comparison.

         [Traditional Coax NetworkDiagram]   [HFC Network Diagram]

                      Figure 1                     Figure 2

The trend has been to lay fiber cables closer and closer to the end user,
such that the last length of fiber (before it splits off into coaxial
to each home) supplies only about 500 to 2000 homes today. Even in the
absence of the Internet, cable companies have a financial incentive to
pursue this Fiber to the Neighborhood (FTTN) approach. It allows them to
offer more channels to their consumers and increase their reliability
because fiber uses fewer amplifiers per kilometer than coaxial cable.
of the original fiber amplifiers, however were designed for one-way
(See disadvantages below.) Estimates range from 10% to 25% for the number
cable systems which have installed two-way amplifiers. However, most
systems expect to have two-way capable networks in the next 12 to 18
After cable enters the home, the Internet setup is illustrated in the

                      [Diagram of Cable Modem hookup]

The original cable networks were analog; as cable companies have
their networks, they have been able to compress more channels into the
bandwidth. Between 4 and 10 digital channels can occupy the same
as an analog channel. The newly created "extra" bandwidth has also
contributed to cable companies offering more channels and the ability to
offer Internet access through cable television.

While speeds of 27 to 40 Mbps have been promised on the high end, the
fastest speed feasible within the near future is 10 Mbps through a
Ethernet card in a computer. (Standard serial ports achieve throughputs
no more than a few hundred Kbps and even SCSI ports have a throughput of
only 5 Mbps.) Cable modems currently cost $500 to $600 today, but the
is expected to drop rapidly. Most cable companies indicate that they plan
lease the modem to the consumer Leasing allows cable operators to allay
consumers' fear of committing to a product that is developing so rapidly
that it may soon be out of date.

Advantages of Cable Internet Access
Internet access with a cable modem through cable television lines offers
several significant advantages over Internet access via telephone modems.
The most appealing advantage of cable access is the high speed cable
can deliver. Cable modems have the potential to receive data at
approximately 30 Mbps. Not only is increased speed a welcome development
individuals used to the relatively slow speed of a 28.8 modem but it will
allow real time Internet presentations such as audio, video and other
multi-media applications to reach anyone with this new cable technology.
Even critics, who warn that 30 Mbps is unrealistic due to the limitations
other networks and of PCs themselves, admit that 1.5 Mbps is probable.
Another benefit of the Internet over cable lines is that it is always
accessible, with no dial up process or busy signals at peak times.
television or telephone use will be interrupted. An additional advantage
cable has is proprietary access to cable wiring connecting 95 million
that will serve as a valuable resource. These advantages make the cable
industry an intriguing provider of home Internet access.

Cable modems are faster than telephone modems. Determining how much
is difficult; the speed varies between different cable companies,
modems and depends on whether one is transmitting or receiving
Speeds from a list of trials were as slow as 96 Kbps (transmit) and as
as 30 Mbps (receive). Several various cable companies have tested their
Internet access service. One successful trial was started by Time Warner
Elmira, NY in July of 1995 with 200 homes. Their service has a potential
speed of 25 Mbps and can deliver bits potentially 800 times faster than a
telephone line because of the greater bandwidth of coaxial cable than
wire used for phone lines. According to the six test customers the NY
interviewed, the service was much faster and all were pleased. One
commented that as he was previously paying $200/month between America
On-Line and his phone bill, the $30 installation and $39.95/month price
which Time Warner plans to market the cable access is quite economical.

Critics claim that while 30 Mbps may be possible for a cable modem, the
of the factors involved in Internet access will limit that speed
considerably. These factors include the cable lines which, unlike
lines, are a shared service with all customers using a piece of the same
line. Every time some one sharing a cable line with you begins
you lose bandwidth and your speed slows down. Typical cable systems serve
between 500-2000 homes on one drop line. Also, the speed of the cable
will be limited by the Internet backbone. Even with the limitations of
Internet backbone and the shared cable lines, it seems the cable access
providers could maintain a speed of at least 1.5 Mbps. This is much
than a 28.8 Kbps phone modem and about equivalent to the rate most large
companies, universities and government offices connect to the Internet.

As well as providing throughput up to hundreds of times faster than a
telephone modem, cable modems offer several other conveniences. They do
interrupt either telephone or cable television access and provide an
Internet connection 24 hours a day. Electronic mail, World Wide Web, file
transfers, video and audio objects, as well as information services such
Internet commerce and financial services are available through cable
without interruption. Cable modems use only a small portion of the cable
bandwidth (unlike a phone line which is busy if it is in use) allowing
rest of the bandwidth for cable television viewing. No dial-up or log-in
process is necessary; network resources are not used unless the user
communication. An additional benefit the cable companies intend to
is the installation and maintenance of the cable modem. The customer will
not be responsible for installing or configuring the modem as they often
with a telephone modem.

There are other technologies that are competing with the cable industry
the home Internet access market that approach cables bandwidth. However,
unlike most of their competitors, the cable industry has the wires
to carry bandwidth into 97% of all US homes and already enters 63% of
What is commonly known as the last mile problem-- wiring high-bandwidth
threads all the way to each user's computer-- is not an issue with cable.

Disadvantages of Cable Internet Access

As exciting as the increased speed is for modem users frustrated with
current slow access, there are several weaknesses the cable industry must
overcome to be successful providers of Internet access. The Internet
backbone, as well as PCs, inhibit potential throughput. To achieve a
throughput closer to the 30 Mbps cable modems are capable of, upgrades
be made to the network structure. These upgrades-- 100% HFC networks and
two-way amplifiers-- are necessary to provide high throughput for
transmitting information as well as receiving. Additionally, the cable
providers must develop both a competent technical staff to install and
configure the cable modems and a strong customer support department to
customers with technical difficulties once their modems are installed and

Three factors will limit the actual speed of cable modems. First many
are linked only by a thin 56 Kbps connection on their end. Second, the
through the Internet backbone that the data follows may be slower than a
cable modem's maximum throughput, due to congestion. And third, if many
users who share a branch of a cable network all connect at the same time,
throughput will suffer as mentioned above. Until the Internet backbone is
improved, cable modems simply move the bottleneck further up the data
A possible solution to the first two problems is caching popular sites at
head end servers so that they can be shared instead of downloading them
time they are requested. Storing frequently accessed sites locally gives
cable companies more control over speed. At least one cable Internet
provider, @Home plans to cache frequently accessed sites a local server
help maintain the cable modem speed. Time Warner's service, LineRunner,
approaching the problem differently, using leased T1 lines at 1.5 Mbps to
feed the head end server. Simba Information published a study emphasizing
the reduced performance the cable modems have due to the Internet
and the individual PCs. Their study showed actual speeds of 3 Mbps for
modems capable of 10 Mbps. However 3 Mbps is significantly better than
be achieved through a telephone modem but not as fast as suggested by the
cable industry. A possible solution to the third logjam is the addition
more routers and channels or bringing fiber even closer to the home.

The problem of the Internet backbone slowing the cable modems is
by the increasing number of sites with audio and video which take up more
space than other traffic. Higher speed alternatives such as cable modems
increase the availability of these real time technologies and make them
popular thus increasing the volume of Internet traffic. New products
allowing graphics, animation, audio and video are growing in popularity
cable modems by allowing access to these developments can change Internet
usage patterns.
The other major technical problem the cable industry faces is the two-way
communication of the Internet. The National Cable Television Association
said in May of 1996 that approximately 25% of the 95 million homes with
cable have two way capability. Typically, home users receive more than
send out so cable companies will choose to allocate most of their
to incoming traffic. Users who transmit large amounts of data will find
model frustrating. Cable companies must continue to upgrade to fiber
which better accommodate two way communication. Until their systems have
two-way capability, some cable operators have tested transmitting
data through telephone lines.

Technical costs are not the only obstacle the cable industry faces.
Typically not known for their customer service standards, cable companies
must provide a well-trained customer support staff to service cable modem
customers. Mical Gerulat, Vice President of Engineering for Cable
said, "It's difficult for some people to program a VCR, let alone a cable
modem." Inexperienced users find accessing the Internet complicated. The
cable companies must provide support to assist customers with these
difficulties. This staff can be costly. Recently, PSI Net, a leading
Internet access provider, stopped providing inexpensive Internet access
to the burden of providing customer service to new users. This training
must be evaluated in addition to the technical costs by the cable

Cable companies must invest a significant amount to make cable modems
practical. They must install two-way amplifiers, routers and servers to
strategically manage Internet traffic. Head ends must be connected to the
Internet. The question the cable industry must analyze is if there is a
enough return to justify the massive upgrades. The initial predictions by
experts in the field say probably not. It could cost as much as $2000 per
user just to install the infrastructure-- the HFC network and two-way
amplifiers-- to the user's doorstep. In addition, the cable modem itself
costs about $500. Finally, there is the large expense of setting up
support divisions much more extensive than what presently exists. Yet the
cable companies suggest they will offer this service for less than $50
month plus an installation fee. It is reasonable to assume that the
will not be profitable for the first 5-8 years. In an industry that is
already more heavily debt-burdened than most, the possibility of its
profits that far down the road from a technology that may well be
by a host of competing ideas may not be so appealing.
Cable Internet Access Trials & Standards

Eleven cable companies are presently conducting 15 trials, involving 70
500 customers each, of cable Internet access. Wide scale deployment is
expected until 1998. Nevertheless, Forrester Research predicts that 6.8
million homes will have cable modems by 2000, at a price of about $150
modem. Forrester also predicts that revenue to the cable companies will
in the $1.3 billion range by 2000. The monthly bill for consumers should
in the $20 - $40 range.

                             Cable Modem Trials

                   Source: Cable Modem Trials in the U.S.

     Company      Location  Modem Vendor       Speed     Description of
Start/End Expected Cost/Month
 Adelphia       Penn, Toms LANcity           10Mb/s,     I-Net Access
Early 96 30         N/A
                Rvr, NJ                      both ways
                Yonkers,                     500 kbs/bi
 Cablevision    Long Island Zenith &         & 10Mbps/bi AOL, Prody,
Early 96 500 or     N/A
                NY          LANcity          (LANCity)   I-Net

                 5 cities                    27mbs down, 100K Motos
 Comcast         incl PA &   Intel/ Hybrid   96K or      /150K HPs;
late '94, 70, 10k by N/A
                 Baltimore   Networks/HP's   3Mbs(HP) up AOL, Prodigy,
has 70    '97
 Cont.                                                   Boston College
 Cablevision    Boston MA    LANCity         10 Mbs/bi   Net
Early 96 200        N/A
 Cont.                                                   Limited tech
 Cablevision    Exeter NH    Zenith          500 kbs     trial; I-Net
Early 95 N/A        N/A
 Cox                                                     tech
 Communications San Diego    Zenith          500 kbs     trial/Prodigy
Early 95 170 homes N/A

 Cox            Phoenix &                                Trial,
Lan test in
 Communications Spokane     LANCity         10Mbps       Internet
Feb 96    100 homes Spokane
 Jones           Alexandria                              will turnkey
 Intercable      VA           LANCity       10Mkbs/bi    for MSOs
Jan 96    30 or more $40/mo
                                            500 kbs/
 Media General   Fairfax VA   Zenith        both         I-net access,    3Q
96     several    N/A
                                            directions   schools

 Rogers                       Zenith &      500 kbs/     WAVE: AOL,
400 paying
 Cablesystems     Toronto     others        both         Prodigy, I-Net
mid 95     customers $40/mo

 TCI East                                                Going
 Lansing         Lansing MI   LANCity       10 Mbs/bi    commercial/
mid 95    N/A        $40/mo
                                                         see above
 Time/Warner     Akron &      Motorola      down,        Commercial
Sept 96   2000 to    $40/mo
                 Canton, OH
                                            768Kb/s up
                                                         Commercial in
 Time/Warner     Elmira NY    Zenith        500 kbs/bi   5 markets 96,
Early 96 200         $15
                                                         ordered 50K

 Time/Warner     San Diego CAToshiba        10Mbps       N/A
Dec 95    N/A        N/A
                                                         ISP access &
 US West          Omaha, NB   N/A           N/A          Personal WEB
late 96    300 in     $50-$60/mo

The industry has not yet developed a technical standard (though one is
planned by 1997; see The IEEE 802.14 Cable TV Protocol Working Group. The
standard will be developed in three phases, as follows:

   * Phase 1: connection between the cable television modem and the
     subscriber's computer and link between cable plant and the next
     of wider area networks.
   * Phase 2: interface to operational support systems, e.g., billing
   * Phase 3: connection between the cable modem and the cable
     plant security management interface.

Competing Technologies

Cable modems are not alone in the race to provide broad band Internet
to home users. Four other technologies promise fast incoming data. These
are: ISDN, leased lines, satellites and ADSL/xDSL.

Integrated Services Digital Network (ISDN) is an idea that telephone
companies have researched for many years. It is the slowest competing
technology as well as the most mature and is commercially available in
areas of the U.S. It offers a digital connection through ordinary phone
lines directly to your PC. For residential users, ISDN typically offers
channels that are 56 Kbps or 64 Kbps each. (This is called Basic Rate
Interface Service.) If the local phone company and Internet Service
(ISP) will allow, the two channels can be combined to give users two-way
throughput of as much as 128 Kbps. (A commercial version of ISDN, called
Primary Rate Interface, offers 23 combinable 56 or 64 Kbps channels.)
are three ways to connect your PC to an ISDN line: through an ISDN
card installed directly in the PC, through an external ISDN modem, or
through a network router. Only the network router lets one to connect
multiple PCs to a single line. A modem's throughput is limited to the
port's speed while an internal adapter is limited to the computer's bus
speed and is typically much faster. ISDN has several drawbacks. First is
difficulty of compatibility. ISDN has to pass two compatibility tests:
with the local phone company and another with the ISP. In addition, ISDN
fairly costly. The equipment can range between $300 and $1500, while
service (basic rate) can be $50 to $300. Also, phone companies typically
charge by the minute for ISDN calls.

Leased lines provide a fast Internet connection 24 hours a day for a flat
monthly fee (usually) at a price that can range from $500-$7500 per
Leased lines are similar to ISDN in that they offer a direct digital
connection from ISP to the user's PC (or more typically, LAN). Leased
come in five varieties: Switched 56 KBPS; Frame Relay; Fractional T1,
T1; or T3. These are listed in order of both speed and cost, from
approximately $300 per month for 56 Kbps to $7500 per month for 45 Mbps.
Leased lines connect to a PC through a DSU/CSU (Data Service Unit/
Service Unit) which allows the phone company to diagnose problems and
data from the telephone wires to cables compatible with a PC, such as
net or UTP. Leased line users pay more for longer distances. Leased lines
are typically used by universities and corporations as they are too
expensive for an individual user but are very reliable.

Southern exposure is necessary for satellite-base Internet access.
Currently, only one company, Hughes Electronics, is offering a satellite
service, DirectPC, but Bill Gates and Craig McCaw have teamed up to
Teledesic by 2002. A few other systems are being explored as well.
is a one-way system. Though Hughes promises a 400 Kbps download bit rate,
tests have shown that Direct PC is less than 200 Kbps. Users receive data
from a single geostationary satellite and send replies back to their ISP
through analog telephone lines. Installation is difficult as you not only
have to find the exact position of the Galaxy 4 satellite in the sky, but
you also have to configure the software to send only outgoing data to
ISP over the telephone. The cost of setup is about $100 and monthly
range from $16 to $40 plus ISP charges. Teledesic plans to launch 840
low-earth orbit satellites that will provide two-way Internet access.
Pricing has not yet been determined.

As we have stated, one of cable's biggest advantages is that the wires
already in almost every home in America. However, a new technology on the
horizon, Asymmetric Digital Subscriber Line (ADSL) (and its sequel, VDSL:
Very-high-data-rate Digital Subscriber Line) may be able to take
of previously installed telephone wiring and offers incoming data at
of 1.5 to 9 Mbps and outgoing data rates of 16 to 640 Kbps. While it is
as fast as cable it is much faster than what is presently available. ADSL
works by electronically isolating certain unused frequencies from
voice calls, and using digital compression algorithms to allow data to
through the same wires as telephone calls at very high rates. (VDSL can
provide speeds of 13 to 55 Mbps.) ADSL has two competing standards: CAP
Carrierless Amplitude Modulation, and DMT or Discrete Multitone. DMT is
newer and faster but is probably more expensive. ADSL customers can be no
more than 9,000 feet from a telephone company's central office as
to 18,000 feet for ISDN and 80 Km for cable head-end to customer maximum
distance. Only slightly more than half of American phone customers are in
the 9,000 foot range. ADSL is years behind cable in development; GTE
the first trial only last spring. ADSL modems will cost $500 to $2000,
because the tests are just getting underway, a pricing scheme for
and access has not been determined. Equipment incompatibilities are not
much of a problem as with ISDN; an ADSL modem connects directly to a PC's
Ethernet port.


About a year ago, The Economist published a special section called "The
Death of Distance," commenting on the telecom revolution that is
Similar to the transportation revolution that occurred over the first
two-thirds of the twentieth century, the telecom revolution does not make
possible previously impossible feats; it "merely" allows one to do what
been done in the past at a much faster rate. The car made it possible to
to the suburbs much faster, allowing people to live in the suburbs and
in the city; the jet made it possible for people to commute round-trip
between cities in a single day, allowing face-to-face business meetings
occur more easily. In today's Internet world, netizens can download large
video and audio objects, sign on to the Internet at will, and do all of
things that cable modems will make "possible." Yet the winner(s) of the
high-bandwidth race to the home will allow users to send and receive this
type of multi-megabit information at an appealing speed. Of all the
high-bandwidth technologies, cable modems show the greatest promise. Much
the necessary infrastructure is already in place and access does not
interupt other cable services. On the negative side, cable operators must
undertake expensive technical upgrades and establish, hire, and train
technical support departments to make their offerings successful. In
addition, no one really knows which technology will dominate. If
decide that they prefer satellite or ADSL access to the Internet over
modems, a multi-billion dollar investment by the cable industry-- an
industry already on shaky financial turf-- will be an economic failure.



   * "Will The Race For Faster Access Have Legs?," Carol Wilson & Paula
     Bernier, Inter@ctive Week article (8/5/96) about Internet
     including cable modems.
   * "From Couch Potato to Cybersurfer," The Economist. Article (7/6/96)
     cable modems. Each of the next three issues has a similar article on
     different high-bandwidth technology.
   * "Cable Modem: Not a Near-Term Solution," Jupiter Communications
     Newsletter (6/96)
   * "Best-Kept Secrets: Cable Scam Endangers Vendors, Users," Jesse
     PC Week article (7/1/96)
   * "Breaking the Internet Speed Barrier," David Strom, Windows Sources
     (6/17/96) Series of articles on fast Internet access including cable
   * "Depite Obstacles, Hopes Still High on Net Over Cable," Web Week
     article (6/3/96)
   * "(IN) Frequently Asked Questions About Cable Modems," Video
     Provider Newsletter article (6/96).
   * "Internet over Cable TV Network," Matjaz Debevc, paper from the
     University of Maribor in Slovenia (5/16/96).
   * "More on Modems," Jennifer Pendleton, Cable World article (5/13/96).
   * "Speed, Speed, Speed - Cable Modems are Here!" Neal Schnog,
     Magazine article (5/96).
   * "Ops Still Face Hurdles on Modems," Leslie Ellis, Multichannel News
     article (4/29/96).
   * "When Cable Modems Are Not All That Fast," Leslie Ellis,
     News Article (4/22/96)
   * "Cable Industry Seeking Standard for Net-Capable Modems," Web Week
     article (2/96).
   * "Cable Modems and ISDN for Faster Internet Access,"WHDH Channel 7
     (Boston) news story (1/31/96).
   * "Cable Modems Draw Glances at High-Tech Beauty Pageant," Peter
     New York Times article (1/31/96).
   * "Internet Offers Business Frontier for Cable TV Companies," Mark
     Landler, New York Times article (1/31/96).
   * "Cable Modems: The Big Daddy of Data Haulers?" Peter Coy, Business
     article (1/29/96).
   * "Will Cable Modems Replace ISDN?" Paul Bernier, Inter@ctive Week
     article (12/29/95).
   * "Cable Modems to Mend Multimedia," press release from Forrester
     Research (12/28/95) about their "On-line Needs Speed" report.
   * "Tuning in to Cable Modems", John Zyskowski, Computer Shopper
   * "2020: The Fiber-Coax Legacy," Nicholas Negroponte, Wired Magazine
     article (10/95)
   * "Despite trials, Internet cable access years off," Anne Knowles, PC
     Week article (8/7/95).
   * "TW Jumps On High-Speed Info Bandwagon," Carol Wilson, Inter@ctive
     article (5/22/95).
   * "Cybercable Is Coming. Who You Gonna Call?" Gary A. Bolles,
     Week article (5/22/95).
   * Videotron's Internet over Cable Technology Primer
   * "Cable Data Modems: A Primer for Non-Technical Readers," CableLabs
     publication with their picture of the world.
   * The Cox Cable cable modem FAQ


 [Quill pen & parchment picture] Please send comments to: Becky Schonfeld
                                 and Dave Morris


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