Lesson 5
Internet Connectivity
Overview
This unit provides an overview of the common Internet access methods. We will begin
with introducing the services available to Internet users. At the same time we will
compare the services offerings available for Internet users by looking at its advantages
and disadvantages. We will then name the low-speed and high-speed options for Physical
Layer Internet connectivity. At the end of the unit you should be able to identify the right
service for you.
Lessons
1. Common Internet Access Methods
2. Bandwidth Issues
Lesson 1 – Common Internet Access Methods
Objectives:
At the end of this lesson you will be able to:
 Describe the services available to Internet users and compare the service
offerings for Internet access
There are various ways to gain access to the Internet, and access is becoming easier all
the time. Perhaps the easies ways to gain Internet access are through an online
information service such as UUNET or America Online, or a local ISP. These are
companies that are in the business of providing access to the Internet through their own
computer networks.
Individual Internet Access
An individual user normally accesses the Internet by means of modem with a dial-up
connection to an ISP or online information service. The individual uses a software
program that is usually provided by the ISP. The software provides and interfaces for
Internet access and uses the modem to access the Internet. Normally, the dial-up software
calls a number to access the ISP, and the ISP provides access to the backbone of the
Internet.
Multiple User Access
Many organizations provide Internet access to multiple users. This is accomplished with
a configuration different from single-user access. The Multiple-User Access Diagram
illustrates how multiple users connect to the Internet.
In this diagram, many clients can access the Internet simultaneously. The speed at which
users can access the Internet is primarily dependent on the link between routers at the
sending and receiving networks. Most organizations use a dedicated line for this
connection, as opposed to a dial-up (shared) line.
ISPs
Internet service providers (ISPs) are companies that provide Internet access to
individuals, businesses, and other organizations. ISPs typically provide a range of
services necessary to provide corporate networks and other users with full access to the
Internet.
In addition to providing users with dial-up connections to the Internet, ISPs provide
dedicated access to the Internet by means of Integrated Services Digital Network (ISDN),
T1, Digital Subscriber Line (DSL), satellite, cable, and other leased lines. A dedicated
connection generally costs between $40 and $500 per month and up, depending on the
connection speed and type of connection used. Because of this expense, ISPs tend to
provide a high level of service and support needed by corporate clients.
Using an ISP with a dedicated line allows a business to use a domain name and dedicated
IP address. This is typically necessary when dealing with a corporate network or other
large-scale connection, such as Web site.
The fees charged by ISPs vary somewhat, but are becoming much more competitive. The
connect tome allowed for the monthly fee can vary significantly, ranging from 10 hours
to unlimited use. Many providers have a maximum monthly fee for dial-up connections.
When investigating ISPs, keep in mind that the cheapest rate may not be the best deal if
you often get a busy signal when trying to connect. Also, you should be concerned with
the type of connection and bandwidth that your ISP has to the Internet. Certainly in a
business environment where maximum up-time is critical, the reliability of your ISP is of
greater concern, and may be worth the higher fees of a full-time ISP with support staff
and a reliable connection to the Internet.
Network Access Providers (NAPs)
Sell Access to
Internet Service Providers (ISPs)
Sell Access to
Large businesses
and organizations
Smaller ISPs
Sell Access to
Smaller business
and organizations
Individuals
Figure 5-1 The Hierarchy of Internet Service Options
Connection Types
There are two ways to connect to the Internet. The first is dedicated access, where a
permanent connection is made to the Internet solely for the purpose of providing Internet
connectivity. The second is non-dedicated access, where a line or circuit is used for
intermittent access to the Internet, as well as other uses. Some technologies, such as dialup lines and ISDN, can be used for both dedicated and non-dedicated installations. The
difference between the two is the type of equipment used to make the connection. For
example, the Dedicated vs. Non-dedicated Access Diagram illustrates how an ISDN line
might be used for dedicated and non-dedicated applications.
Nondedicated
ISDN
Modem
Digital telephone
signal to telephone
network
Telephone
Digital computer
data to ISP
Figure 5-2
Dedicated
Router with
ISDN Port
Telephone
POTS line to
telephone network
Digital
computer data
to ISP
Figure 5-3
Dedicated Access Methods
The minimum type of dedicated connection is a dedicated dial-up modem connection.
This connection is similar to the non-dedicated access connection, but requires a
permanent analog telephone number for the modem connection. The connection speed is
primarily controlled by the modem connection speed.
ISDN is a popular connection method for dedicated digital Internet access. ISDN is also
used for non-dedicated access and can be shared with telephony services. An ISDN
connection requires an ISDN telephone line from the local telephone company, ISDN
modem, and ISDN-capable ISP. Depending on the configuration used, ISDN can achieve
a bandwidth if 64 or 128 Kbps. There is usually an initial setup fee for an ISDN
connection, plus the ISDN modem cost and telephone line setup fees.
Many connection methods require a private line connection from the local telephone
company. Private line connections generally have the following basic components:
 Common carrier connection
 Data service unit/channel service unit (DSU/CSU)
 Router
 Access from an Internet service provider
Non-dedicated Access Methods
Non-dedicated access is access that is not continuous. The connection is established when
required and released when no longer needed. The connection is usually made through a
switched network – typically the telephone system.
Access by means of the Telephone System – the most common method of Internet access
is through an existing telephone line. The telephone line runs from the customer, either a
residential location or business location, to the central office. (CO). The telephone line’s
construction is pairs of copper wires twisted together (twisted pairs). The CO contains
switching equipment to connect the pairs of wires to the public telephone system. The
telephone system was originally designed to carry voice signals using analog (as opposed
to digital) technology. This type of service is often referred to as plain old telephone
service (POTS).
 Modems
Because the telephone system was designed for analog voice transmission, it was not
able to carry binary (digital) data. Modems were designed to convert digital data
signals to analog signals (or to modulate them) for transmission over voice-grade
services. (The term “modem” is the shortened version of Modulator-DE-Modulator).
The first modems were originally developed for military use with radio teletype, and
ran at 75 baud (roughly equivalent to 75 bits per second [bps]).
Later, modems were designed to be used with the telephone system. Originally these
were “acoustically coupled.” The modems used a cradle to hold the headset so the
tones representing the data could be sent into the headset. Later, direct connections
were made using the RJ-11 snap-in connector we are currently familiar with.
 Connection Rates
Modem gradually evolved to run at faster and faster speeds – 110 baud, then 300,
1,200, 2,400, 4,800 and 9,600 baud. They also included “automatic dialing,” which
allowed the computer to dial the number. Using data compression and improved
modulation techniques, data rates improved further to the current data rates of 14,400
bps (14.4 Kbps), 28,800 bps (28 Kbps), 33,600 bps (33 Kbps), and 56,000 bps (56
Kbps).
These higher data rates are very close to the limit of sending data over voice analog
telephone wires. However, these high data rates are dependent on the quality of the
telephone line connection. Even if you have a 56 Kbps modem, you may have to connect
at a lower data rate. Keep these concepts in mind when using 56 Kbps modems:
 56 Kbps modem technology depends on the ISP’s digital phone lines that convert to
your analog phone line.
 The connection is asymmetric, meaning that download speeds can be as high as 56
Kbps, but upload speeds may be only 28.8 to 33.6 Kbps.
 Because of FCC limitations, the V.90 56 Kbps standard is limited to 53 Kbps in the
U.S.
The Local Loop
The “local loop” or “last mile” of the communications network is the “user’s driveway”
at the end of the information superhighway. Communications providers (cable
companies, telephone companies, and satellite transmission companies) are currently
investing billions of dollars to create a broadband infrastructure in the local loop. This
section provides an overview of these developments.
Why High-Speed Local Loop is “Hot”
There are four reasons for the current brisk pace of development and deployment of highspeed Internet local access solutions as follows:
 Increasing popularity of the Internet – Connecting to the Internet is now the number
one reason that people buy a computer. Given a “taste” of bandwidth, both businesses
and consumers are increasing demand for advanced Web technologies, such a fullmotion video and enhanced interactivity, which required more bandwidth.
 Pressure from software and hardware providers – providers see high-speed local
access to the Internet as crucial to their continued growth. Microsoft in particular
believes that faster access will make it possible to enhance the Internet with more
television-like graphics and video, which would increase the market for PCs loaded
with Microsoft software. Even of all the issues of high-level Internet congestion and
server overload were resolved, the speed over the last mile would remain the limiting
factor. Microsoft’s recent $1 billion investment in cable companies has served as a
“wake-up-call” to telephone companies.
 Accelerated application development – Advances in browser interfaces and
“universal” programming languages, such as Java, are speeding Internet applications
development. Advanced software products for home/work integration (e.g.,
telecommuting and extranets) are gaining more attention. The media and advertising
industries are pushing applications involving two-way communication with
consumers to collect marketing data and facilitate impulse shopping.
 Intensifying competition – competition to provide broadband connection to the home
has become intense. Telephone and cable companies are squaring off against each
other to snatch up and growing number of “netizens”.
Options for Local High-Speed Internet Access
The option for High-Speed Internet Access Table summarizes mass-market solutions for
Internet access currently deployed or being tested in some areas of the United States.
Options for Local High-Speed Internet Access
Speeds
Speed to
56 Kbps
Frame
modem
Relay
56 Kbps
56-64
128
Kbps
Kbps
user
ISDN
ADSL
ADSL
Lite
1.5 Mbps
7 Mbps
8 Mbps
Cable
DirecPC
modem
Satellite
30 Mbps
400
Kbps
Speed
33.6
64 Kbps-
128
128
from
Kbps
1.544
Kbps
Kbps
user
RADSL
1 Mbps
1 Mbps
3 Mbps
56 Kbps
Mbps
56 Kbps Modem
The 56 Kbps modem is the fastest dial-up solution available to consumers today. It is an
inconvenient “narrow band” solution, provided here for comparison with the broadband
solutions.
Frame Relay
Frame relay is one of the most common methods of dedicated Internet connectivity.
Frame relay service is typically available at speeds of 56 Kbps, 64 Kbps, and increments
of 64 Kbps to 1.544 Mbps.
ISDN
Integrated Service Digital Network (ISDN) is an end-to-end switched digital network that
integrates enhanced audio and video features with high-speed data and text transfer. Built
on top of standard, unshielded twisted pair telephone wire, ISDN provides two rates of
service: basic and primary. The relevant version for the mass market is basic-rate ISDN,
which provides three channels over one pair of twisted copper wires: two “bearere
channels” at 64 Kbps each and one control channel at 16 Kbps for signaling or pacjetized
data. The two bearer channels can be bonded to provide a total speed of 128 Kbps.
Despite being available since the early 1990s, ISDN has not caught on because of its
limited availability and price. (LECs have been reluctant to decrease their T1 business.)
Estimated 1997 penetration was only about 5 percent of total telephone lines.
(Asymmetrical Digital Subscriber Line [ADSL] and Rate-Adaptive Digital Subscriber
Line [RADSL] can deliver ISDN, although they take away from the bandwidth for data.)
Cable Modem
Cable modem is a technology for providing broadband Internet access over a cable
television provider’s hybrid fiber coaxial (HFC) network. It is a broadcast technology
analogous to an Ethernet LAN. Bandwidth is shared, and packets move around in a storeand-forward scheme. The cable modem located in each subscriber’s home filetes out the
information not addressed to that particular subscribers. The remainder is delivered to the
subscriber’s computer by means of a virtual point-to-point connection. Cable modem
downstream speeds have the potential to reach 36 Mbps, although the cable provider
limits the speed that is available.
Advantage of Cable Modem
The main advantage of a cable television connection to the Internet is its high bandwidth.
A cable connection can provide very fast downloads to your computer from the Internet
as much as 170 times faster than a telephone line connection. Although upload speeds are
not as fast, there are still about 14 times faster than a telephone line connection. The cost
usually is higher than and often more than doubles what competing ISPs charge.
However if you consider that the cable connection might save you the cost of a second
telephone line, then the benefit can be significant.
Disadvantage of Cable Modem
The greatest disadvantage for most people right now is that the cable connection is
simply not available in their area yet. This is because cable companies must invest in
expensive upgrades to offer this service.
Another problem arises from the shared nature of the cable connection. As more people
in your neighborhood subscribe to cable modem service, they share the bandwidth of
your connection. This can slow down your access speeds significantly. The cable
company should monitor the traffic and when needed add more equipment to handle the
increased load. Not all cable companies have been diligent in doing this. You should
remember that other than the nature of the connection, a cable company is the same as
any other ISP.
DSL Technology
xDigital Subsriber Line (xDSL) is the modem technology that converts existing twisted
pair telephone lines into access paths for multimedia and high-speed data
communications, while simultaneously providing POTS. Developed in the 1980s to
deliver video-on-demand (VOD) over telephone limes, xDSL has the potential to deliver
data at 160 times the speed of a 56 Kbps modem. The speed of a particular xDSL
installation depends on the variant of the xDSL protocol (ADSL, RADSL, or ADSL
Lite), the thickness if the copper wire, and the distance from the telephone company’s
CO. The various types of xDSL include the following:
Advantages of DSL Technology
DSL providers often claim that their service is better than that offered by cable
companies because the part of the DSL service that runs from the customer to the
telephone company is not shared. The traffic loading problems that occir with cable
modem access cannot occur with DSL service. Of course once the packets enter the DSL
provider’s network the bandwidth is then shared and heavy traffic loads can slow down
access for everyone using the service. DSL’s speeds are similar to cable modems and the
subscription rates are similar.
Disadvantages of DSL Technology
The biggest drawback for most DSL users is that they are buying the service from either
their local telephone company or a third-party provider that must work with the telephone
company. Many people have experienced long delays in getting DSL service installed or
in having repairs completed. Telephone companies have not done a very good job in
training their employees to sell, install, and maintain DSL services. The third-party
providers must depend on the telephone companies to install the service because it uses
the telephone company’s lines. A number of large DSL providers have gone out of
business recently because they were unable to deliver the services they promised and
make a profit. In many cases, their subscribers were left without an Internet connection
for months before another company entered the market.
 ADSL
ADSL provides downstream transmission rates of 1.544 Mbps for up to 18,000 feet
of twisted pair wire, 6.312 Mbps for up to 12,000 feet of wire, and 8.448 Mbps for up
to 9,000 feet of wire (all 24-gauge wire). ADSL is asymmetric in that downstream
data rates (to the user’s desktop) are faster than upstream data rates (from the user’s
desktop). Asymmetric solutions are attractive because they match Internet user
patterns. A typical Internet surfing scenario involves 10 keystrokes (sent upstream) to
download a 100 Kbps Graphics Interchange Format (GIF) file.
 RADSL
RADSL is a variant of ADSL that overcomes varying conditions and length of copper
cable. RADSL has the same maximum data rates as ADSL, but both downstream and
upstream rates are adjusted to the line conditions (which depend on line length and
interference ([crosstalk]) at the time of transmission.
 ADSL Lite
In early 1998, Compaq, Microsoft, and several regional Bell operating companies
(RBOCs) formalized their support for ADSL and announced a plan to develop ADSL
Lite, a slightly slower version of ADSL, that does not require installation of a splitter
to separate off POTS signals. Initiation of ADSL Lite only requires plugging in an
ADSL modem and contacting an ISP.
 Very high bit rate DSL (VDSL)
Although currently not commercially available, VDSL promises downstream rates of
approximately 13 Mbps for up to 4,500 feet of wire, 26 Mbps up for up to 3,000 feet
of wire, and 52 Mbps for up to 1,000 feet of wire (all 24-gauge wire).
Asymmetrical DSL in Practice
The ADSL Configuration Diagram provides an overview of an ADSL network. An
ADSL circuit connects an ADSL modem on each end of a twisted pair telephone line. It
creates three information channels:
 High-speed downstream channel that connects to an asynchronous transfer mode
(ATM) network
 Medium-speed duplex channel
 POTS channel, which is split off from the digital system by filters, thus guaranteeing
uninterrupted POTS, even if ADSL fails
Because it works over long distances, ADSL is considered the most viable version of
xDSL. Downstream data rates depend on several factors: length of the copper line, wire
gauge, presence of bridged taps, and cross-coupled interference. Line attenuation
increases with line length and frequency and decreases with larger wire diameter.
ADSL uses analog signals, but spreads them out over a range of frequencies 100 or more
times greater than dial-up modems. The spectrum is sliced into dozens of narrow bands,
as if 100 modems were sending signals over one wire simultaneously.
To create transparent multiple channels at various data rates, ADSL modems divide the
available bandwidth by means of either frequency division multiplexing (FDM) or echo
cancellation:
 FDM assigns one band for upstream data and another band for
downstream data. Time division multiplexing (TDM) futher divides the
downstream path into one or more high-speed channels and one more or
more low-speed channels. The upstream path is also multiplexed.
 Echo cancellation, on the other hand, assigns the upstream band to overlap
the downstream band, and it separates the two means of local echo
cancellation.
Error Correction
Because many applications planned for ADSL involve a real-time signal, datalink-level
and network-level error control protocols cannot be used. Therefore, ADSL modems
incorporate forward error correction (FEC).
An ADSL modem multiplexes downstream channels, upstream channels, and
maintenance channels together in blocks, attaching an error code to each block. The
receiver corrects errors occurring in the transmission, up to the limits of the code and
block length.
Physical Considerations
Local loops have significant numbers of antiquated loading coils, originally installed to
mute high-frequency noise during voice calls. The coils act as low-pass filters that cut off
all frequencies above 4 kilohertz (kHz). Therefore, any loading coil on the loop between
the local distribution node and a subscriber’s home must be removed before ADSL can
be connected.
In addition, there are problems throughout the telephone system, including overlong
loops that attenuate signals, unterminated wire pairs, and crosstalk between wires.
Bellcore estimates that the typical U.S. telephone line crosses 22 splices, allowing line
noise and crosstalk to reduce effective data rates.
Other High-Speed Access Methods
In addition the high-speed options for accessing the Internet described above, there are
several other methods, including those listed below:
 Web TV
Web TV uses a television to display video of Web pages generated by a box that sits
on top of the television. You navigate the Web using a device similar to a remote
control. WebTV (the corporation) was founded in 1995 and purchased by Microsoft
in 1997. Microsoft has funneled millions of dollars into system upgrades and
redesigning the set-top box. Upgraded set-top systems are now available called
WebTV Plus. WebTV Plus sets have 16 megabytes (MB) of random access memory
(RAM), a 1.1 gigabyte (GB) hard drive, a 56 Kbps modem, a smart card slot, and a
printer adapter. The sets also contain a faster (167 megahertz [Mhz] reduced
instruction set computer (RISC) processor and an integrated stereo television tuner.
The Web site at http://webtv.com provides more information.
 Wireless
The cost of installing wires or cable to provide high-speed access has led to
proposals, designs, and construction of radio wireless systems. Examples are Wireless
LANs (WLANs), wireless bridges, and wireless-connected portable computers.
 Pagers
Alphanumeric pagers can be used to send and receive short e-mail messages.
Companies that offer paging services sometimes offer an optional e-mail service.
Other companies offer e-mail service regardless of which paging service you use.
There are even free services supported by advertising.
 Cellular Phone
Modems that use the cellular phone system are available for portable computers. The
modems connect to a cellular telephone by means of a cord; the telephone itself needs
to support cellular modems. The service is generally available in areas that have
cellular access. This type of Internet access tends to be expensive because it is based
on connect time similar to a regular voice, cellular telephone call. Performance is
mixed when the user is in motion, but it can be satisfactory when the user is
stationary. Costs can be reduced if the technology is only used for retrieving and
sending e-mail messages.
 Satellite-Based Access
There are two types of satellite systems used or being planned for Internet access:
geostationary earth orbit (GEO) systems and low earth orbit (LEO) systems.

GEO Systems
GEO systems are high-altitute satellites (22,300 miles) whose orbital speed
matches the rotations of the earth. As a result the satellites appear to be
stationary in the sky. GEO satellites use proven technology and are currently
available. However, dishes are usually necessary to receive transmissions. An
example of GEO satellite technology is found in DirectPC available
nationwide from Hughes Network Systems. It is a GEO system using satellites
for high-speed downloads and uploads (up to 400 Kbps) and a standard POTS
modem for uploads. The service requires the user to buy a 21-inch dish,
receiver, interface card, modem (if you do not have one), and installation.
Equipment costs range from $350 to $550 depending on installation fees,
activation fees, and modem costs. Monthly rates are approximately $5 per
month and $4 per hour for 200 Kbps service, to $130 per month (flat) for 400
Kbps service. DirectPC offers a two way-system that handles high-speed
uploads and downloads or a one-way system that uses the satellite connection
for uploads and telephone lines for downloads.
DirectPC is currently supported only on Windows systems with protocol
control information (PCI) interfaces. It is the fastest, most generally available
Internet access method if you have the money. In some places, the cost is
almost the same as ISDN (at only 128 Kbps). For more information, visit
http://www.directpc.com.

LEO Systems
LEO satellites operate at much lower orbits (400 to 1,000 miles). As a result,
they appear to move across the sky relatively quickly. LEO systems are
“constellations” of many satellites. A constellation moves around the earth
with the satellites staying in fixed positions relative to each other. LEO
systems use smaller and less expensive satellites, offer faster round-trip
transmission times, and provide global coverage. However, many satellites are
needed for each constellation (over 40), and construction costs are high ($3 to
$9 billion per constellation). These systems are currently being constructed
because the demand for satellite service justifies the cost.
Teledesic is the “Internet in the sky” envisioned and started by Bill Gates and
Craig McCaw. Boeing Aerospace also has an interest in the company. When
finished, Teledesic will consist of 288 LEO satellites and provide worldwide
two-way broadband voice, data
and teleconferencing along with Internet
access. Service is expected to start in 2005. Visit http://www.teledesic.com for
more information.
Lesson 2 – Bandwidth Issues
Objectives:
At the end of this lesson you will be able to:
 Name the low-speed and high-speed options for Physical Layer Internet
connectivity
 Determine which technology is most appropriate for a given business
application
This lesson summarizes the most popular Internet connection technologies and their
associated speeds. We begin by looking at low-speed options such as dial-up and lease
lines, and we progress to higher-speed technologies such as T3 and OC-3. we look at
applications that might use each of these options and the associated performance that
each application may require.
Bandwidth
Bandwidth is the difference between the highest and lowest frequencies that can be
transmitted across a transmission through a network. This concludes that bandwidth is the
amount of data that can travel through a communications circuit in one second.
Bandwidth is measured in hertz (Hz) for analog networks and bits per second (bps) for
digital networks.
Different types of applications require different bandwidths for effective use. Some
typical applications are listed below:
PC communications
28.8 to 56 Kbps
Digital audio
1 to 2 Mbps
Compressed video
2 to 10 Mbps
Full-motion video
1 to 2 Gbps
Just as radio stations each use a narrow slice of the overall broadcast radio spectrum,
some data transmission protocols can divide the total available bandwidth into many
narrow virtual channels. In effect, they turn one big channel into a bundle of many small
ones, each able to carry part of the overall communications traffic. Therefore the greater
the range of frequencies a medium can handle (the greater its bandwidth), the greater its
information-carrying capacity. Most modems transmit data within a 300-Hz to 3,000-Hz
frequency range.
Point-To-Point Links
Point-to-point links establish a physical connection, either permanent or temporary
between local and remote stations. These links come in a variety of data rates and as
speed and capability increase, cost increases as well. Because a point-to-point link
provides dedicated bandwidth for the duration of the connection, the cost of moving data
this way is usually much higher than with switched services. In addition, when
constructing a network using point-to-point links, we must lease these dedicated facilities
for each line of communication we want to establish. This means that the number of links
increases rapidly with the number of nodes: 3 links for three nodes, 10 links for five
nodes, and so on. An example of a leased line is a T1 line.
Switched services reduce costs by establishing the necessary number of dedicated links as
virtual circuits over a shared communications service. Packet-switched services such as
ATM and frame relay will continue to be a primary alternative when connecting remote
networks.
LECs offer traditional telecommunications services that use existing telephone company
voice network facilities and the copper local loop between customer and CO. The bottom
rung of the point-to-point ladder is the analog connection, which uses modems to carry
data over leased or switched lines. Leased lines are full-time physical connections
between two specified locations; switched lines are regular telephone lines.
Dataphone Digital Service (DDS), also called Digital Data Service, provides speeds
ranging from 2.4 to 56 Kbps. DDS lines are fulltime leased connections between two
specified locations, and they support a fixed bandwidth. DDS lines are usually used to
construct private digital networks. We connect to DDS using a special box referred to as
a DSU/CSU, which replaces the functions of a modem in the analog scenario.
Faster than DDS is Switched-56 (SW56) service, which allows us to make dial-up digital
connections to any other SW56 subscriber anywhere in the country. It uses the same
DSU/CSU as a leased-line DDS, but it includes a dialing pad for entering the telephone
number of the remote SW56 system.
And finally, at the top end of the point-to-point ladder are high-speed digital services
including:
 Fractional T1 (FT1)
 T1
 T3
 Synchronous Optical Network (SONET)
Various Data Rates and Associated Applications
The Data Rates and Applications Table presents key Physical Layer technologies most
often used for connection to a WAN or the Internet. Technologies, data rates, physical
media, and associated applications are shown in the table. Technology choices are based
on need and economics.
Data Rates and Applications
Technology
Dialup
Data Rate
14.4 to 56 Kbps
Physical Media
Low-Grade Twisted Pair
Application
Home Office Connectivity to
Office and Internet
Leased Line
56 Kbps
Low-Grade Twisted Pair
Small Business Low-Speed
Access
Office-to-Office Connectivity
Internet Connectivity
Swithced-56
56 Kbps
Low-Grade Twisted Pair
Small Business Low-Speed
Access
Office-to-Office Connectivity
Internet Connectivity
Line Backup
Fractional T1
64 to 768 Kbps
Low-Grade Twisted Pair
Small to Medium-Size Business
Moderate Speed
Internet Access
Satellite
400 Kbps
DirecPC
Satellite Dish: Radio
Small Business with Moderate
Waves or Microwaves
Speed
Internet Access
T1
64 Kbps to 1.544 Mbps
Low-Grade Twisted Pair
Medium-Size Business
Optical Fiber
Internet Access
Microwave
Point-to-Point LAN
Connectivity
Technology
E1 (European)
Data Rate
64 Kbps to 2.048 Mbps
Physical Media
Application
Low-Grade Twisted Pair
Medium-Size Business
Optical Fiber
Internet Access
Microwave
Point-to-Point LAN
Connectivity
ADSL
1.544 to 8 Mbps
Low-Grade Twisted Pair
Medium-Size Business
High-Speed Home Internet
Access
Cable Modem
512 Kbps to 52 Mbps
Coaxial Cable
Medium-Size Business
High-Speed Home Internet
Access
E3 (European)
34.368 Mbps
Twisted Pair
Large Business Internet Access
Fiber Optic Cable
ISP Backbone Access
Microwave
T3
45 Mbps
Twisted Pair
Large Business Internet Access
Fiber Optic Cable
ISP Backbone Access
Microwave
OC-1
51.48 Mbps
Fiber Optic Cable
Internet Backbone Connectivity
Campus Internet to ISP
OC-3
155.53 Mbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
OC-24
1.24 Gbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
OC-48
2.4 Gbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
OC-96
4.9 Gbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
OC-192
10 Gbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
OC-255
13.2 Gbps
Fiber Optic Cable
Large Company Backbone
Internet Backbone Connectivity
References:
1. Westnet Learning Technologies (2002).Internet Technologies. Singapore:
Thomson Course Technology
2. Gary P.Schneider and Jessica Evans (2002). The Internet (3rd Ed) United States:
Thomson Course Technology.
3. Gary B.Shelly, Thomas J.Cashman & Misty E.Vermaat (2007) Discovering
Computers 2007: A Gateway to Information, Web Enhanced Complete. USA:
Thomson Course Technology