Chapter

2

Internet Basics

i-NET+ OBJECTIVES COVERED IN THIS
CHAPTER:


Describe a URL, its functions and components, different types
of URLs, and use of the appropriate type of URL to access a
given type of server. Content may include the following:


Protocol


Address


Port


Describe the core components of the current Internet
infrastructure and how they relate to each other. Content may
include the following:


Network access points



Top level or original domains—edu, com, mil, net, gov, org


Country level domains—UK
Copyright © 2000 SYBEX Inc., Alameda, CA. www.sybex.com

T

he Internet is a very complex entity. To understand the topics found
in later chapters in this book, you must first understand the underlying lay-
out and technologies of the Internet so that you have a common reference
point for those discussions. In this chapter, you will learn the following:


What the Internet is


Internet layout


Domain Name Services (DNS)


Uniform Resource Locators (URLs)


Internet communications process
Throughout this chapter, you will also learn the terminology of the

ISPs. Backbone ISPs are ISPs with very high-speed connections between them
(several hundred megabits per second). You will learn about ISPs in the sec-
tions to follow.

FIGURE 2.1

A graphical representation of the Internet

History of the Internet

The Internet started out as a project of the U.S. government’s Defense
Advanced Research Projects Agency (DARPA) in 1973. They wanted to
design a network that could reconfigure itself around breaks and faults in
case one of its nodes were taken out during a war. The architects of this net-
work, called ARPAnet, took this into consideration and developed a suite of
protocols (called TCP/IP) and a network that could do just that.

For more detailed information on TCP/IP, see Chapter 3.

Another network was developed in 1980 to connect IBM mainframes in
university data centers. This network was called BITnet, and it allowed uni-
versities to communicate with one another, thus facilitating collaboration
among professors at those universities with the first, primitive e-mail system.
ISP
ISP
ISP ISPISP
ISP
ISP
ISP
ISP

www.ietf.org

on the Internet.

In 1986, the National Science Foundation (NSF) developed NSFnet as a
backbone for the now-emerging Internet. It would connect the old ARPA-
net, BITnet, and a bunch of other networks together to form the Internet. At
this point, the Internet became very far reaching and very powerful as thou-
sands of people who were now connected to it could all communicate and
collaborate.

The Internet Today

Since the days of the NSFnet, ARPAnet, BITnet, and all the others, Internet
use has grown exponentially. No longer do only geeks and professors know
about it; it has become a part of popular culture. Every television commercial
ends with the company name and the address of the company’s Web site so
you can visit it and get even more information. One measure of a company’s
success is how many hits the company’s Web site gets per day.
It is estimated that in September 1999, there were more than 201 million
people worldwide on the Internet, and that number is estimated to double by
2001. Currently, more than 75 percent of all metropolitan areas in the United
States have Internet access. Basically, any household that has a phone line can
get access to the Internet (with either a local or a long distance phone call).
With each passing year, Internet access technologies allow faster access to the
Internet. Home access speeds are available from 33.6Kbps (modems) to
512Kbps (ISDN and DSL access). At these speeds, Internet content can
include streaming audio and video.
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Access Points (ISPs)

As previously mentioned, anyone can get access to the information found on
the Internet, but first they must be connected to the Internet. The Internet has
often been called the “Information Superhighway.” I’d actually describe it as
an “Internet Tollway.” To get the benefits of the “highway,” you have to pay
to get on. Thus, in order to get on the Internet, you have to pay the people
WAN
connection
WAN
connection
WAN
connection
WAN
connection
WAN
connection
High-speed
WAN connection
ISP
ISP
ISP
ISP
Backbone
ISP
Backbone
ISP
Backbone
ISP

A typical ISP setup
ISP backbone router
Internet or other ISP
E-mail
server
Web (HTTP)
server
Customer Web server
Leased-line
router(s)
Dial-up
router(s)
Router
Leased line
CSU/DSU
CSU/DSU
Multiple WAN
connections
ISP backbone
Customer LAN
POTS
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The Layout of the Internet

61

ISPs can be found in every major city in the U.S. and in almost every rural
area. In Europe and the Asian countries, ISPs can be found in the larger cities.
However, the Internet’s reach is expanding more and more every day. Very

T1 1.544Kbps
T3 44.736Mbps
ISDN 128Kbps–2Mbps
ATM 155Mbps
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62

Chapter 2


Internet Basics

For more information on WAN technologies and their speeds, refer to

The

Network Press Encyclopedia of Networking

by Werner Feibel (Sybex, 2000).

Backbone Providers

Although the Internet is essentially a network of ISPs, there are a few select
ISPs that connect to each other with high-speed WAN connections to pro-
vide the Internet with a “backbone.” These ISPs are known as

backbone
providers


benefit higher education (as did the technologies of the current Internet).
For this reason, a consortium of higher education institutions have gotten
together and formed the University Corporation for Advanced Internet
Development (UCAID). One of UCAID’s projects is

Internet2

(

I2

), the collec-
tion of next-generation Internet applications and technologies being devel-
oped for use with the Internet infrastructure in use today. Internet2 is not its
own network, as some people incorrectly assume. It is only the name given
to the ongoing research of these technologies and their possible applica-
tions. Just as the current Internet technologies have their roots in the col-
laboration efforts of education, it is the hope of the UCAID that the work
done with Internet2 will increase the Internet’s usability. For more informa-
tion, visit UCAID at

www.ucaid.edu

.
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Domain Name Services (DNS)

63


the Social Security numbers of as many as 10 friends and relatives, but after
that things would get a bit difficult. Likewise, it’s easier to remember

www
.microsoft.com

than it is to remember 198.105.232.6.
The process of finding the host name for any given IP address is known as

name resolution,

which can be performed in several ways, and we’ll look at
all of them in the next few sections. But first you need to understand Internet
domains and how they are organized.

Internet Domain Organization

On the Internet, domains are arranged in a hierarchical tree structure. There
are seven top-level domains currently in use:

com

A commercial organization. Most companies will end up as part of
this domain.

edu

An educational establishment, such as a university.

gov

domains to further segment the U.S. Internet DNS space, for example:
firm Designed for naming businesses or firms
shop Domain for online shopping centers
web Domain for Web sites relating to information about the WWW
info Domain used for Web sites that provide some useful information to a
community (like a community billboard)
arts Domain for cultural and entertainment organizations
rec Domain for completely recreational Web sites
nom Domain for an individual person’s name
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Domain Name Services (DNS) 65
International Domains
In other parts of the world, the final part of a domain name represents the
country in which the server is located: ca for Canada, jp for Japan, uk for
Great Britain, and ru for Russia, for example. Figure 2.4 shows an example
of the layout of the Internet DNS hierarchy. Notice how the com, edu, and
international domains are all at the same level.
FIGURE 2.4 Internet DNS domain hierarchy
If you want to contact someone within one of these domains by e-mail,
you just add that person’s e-mail name to his domain name, separated by an
at sign (@). For example, if you want to e-mail the president of the United
States, send your e-mail to this address:

InterNIC assigns all Internet domain names and makes sure no names are
duplicated. Names are assigned on a first-come, first-served basis, but if you
try to register a name that infringes on someone else’s registered trademark,
your use of that name will be rescinded if the trademark holder objects.
Now that we have detailed how Internet domain names work and where
they came from, we can return to our discussion of name-resolution methods.
NET GOV COM MIL EDU ORG DE AU

changers for one host. This feature provides a higher probability that e-mail
will actually arrive at its intended destination. The mail exchangers are listed
in order in the record, with a priority code that indicates the order in which the
mail exchangers should be accessed by other mail delivery systems.
If the first priority doesn’t respond in a given amount of time, the mail
delivery system tries the second one, and so on. Here are some sample mail
exchange records:
host.company.com. IN MX 10 mail.company.com.
host.company.com. IN MX 20 mail2.company.com.
host.company.com. IN MX 30 mail3.company.com.
In this example, if the first mail exchanger, mail.company.com, does not
respond, the second one, mail2.company.com, is tried, and so on.
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