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					Gateways to the Internet
Connecting all the users and individual networks together are Internet Service Providers
(ISPs). ISPs are companies that provide the technical gateway to the Internet.

                              What's the Address?
                              These companies own blocks of registered access addresses
                              that they assign to their customers, to give them an identity on
                              the network. These addresses are called the Internet protocol
                              addresses, or IP addresses.

                              Having a registered IP address makes each site a valid
                              member of the Internet. This is how individual users are
                              identified to receive file transfers, e-mail, and file requests.

IP Addresses
IP addresses exist in the numeric format of XXX.YYY.ZZZ.AAA. Each address consists of
four 8-bit fields separated by dots. This format of specifying addresses is referred to as dotted
decimal notation. The decimal numbers are derived from the binary address that the
hardware understands. For example, the following network address:

10000111.10001011.01001001.00110110 (binary) corresponds to

ISDN Links
Other users, who require quicker data transfers, contract with the telephone company to use
special, high-speed Integrated Service Digital Network (ISDN) lines. These types of links
require a digital modem to conduct data transfers. Because the modem is digital, no analog
conversion is required.
T1 and T3 Dedicated Connections
Users who require very high volumes will lease dedicated T1 and T3 lines from the telephone
company. These applications generally serve businesses who put several of their computers
or networks online
Metropolitan Area Networks
In some areas, high-speed intermediate-sized networks, referred to as Metropolitan Area
Networks (MANs), are popping up. These networks typically cover areas up to 50 kilometers
in diameter and are operated to provide access to regional resources. They are similar to
LANs in speed and operation but use special high-speed connections and protocols to
increase the geographical span of the network — more similar to WANs

The language of the Internet is Transmission Control Protocol/Internet Protocol, or TCP/IP for
short. No matter what type of computer platform or software is being used, the information
must move across the Internet in this format. TCP/IP is now supported on virtually every
brand of computing equipment.
                                                    The TCP/IP Packet
                                                    TCP/IP calls for data to be grouped
                                                    together in bundles called network

                                                    The TCP/IP packet is designed primarily
                                                    to allow for message fragmentation and
                                                    reassembly. Packet information is
                                                    conveyed through two header fields: the
                                                    IP header, and the TCP header, followed
                                                    by the data field, as shown.

Domain Name System
The IP addresses of all the computers connected to the Internet are tracked using a listing
system called the domain name system (DNS). This system evolved as a method of
organizing the members of the Internet into a hierarchical management structure. The DNS
structure consists of various levels of computer groups called domains. Each computer on
the Internet is assigned a domain name, such as Each domain
name corresponds to an additional domain level.

Names and Addresses
In addition to its domain name tracking function, the DNS system links the individual domain
names to their current IP address listings

Site Identifiers
In the example, the .com notation at the end of the address is a
major domain code that identifies the user as a commercial site. The following list identifies
the Internet's major domain codes:
    .com = Commercial businesses
    .edu = Educational institutions
    .gov = Government agencies
    .int = International organizations
    .mil = Military establishments
    .net = Networking organizations
    .org = Nonprofit organizations

Subdomain Names
The .owt identifies the organization that is a domain listed under the major domain heading.
Likewise, the .oneworld entry is a subdomain of the .owt domain. It is very likely one of
multiple networks supported by .owt. The Marcarft entry is the address location of the end
user. If the end user location is an e-mail address, it is usually denoted by an ampersand (@)
between its name and the name of its host domain (that is,

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