Module 5: The Internet 
Overview of the Internet

Introduction

The Internet evolved from an earlier United States government computer network known as the Defense Data Network (DDN). It was designed to provide a way to share information between different types of computers and provided a link between most of the major universities in the United States.

The Internet is a collection of widely varied services. The introduction of the World Wide Web with its user-friendly graphical nature helped to establish mainstream acceptance of the Internet as an information source. Both corporate and individual Web sites are commonplace.

A common practice is the implementation of Internet technologies on local, private networks. These networks are often referred to as intranets to describe their more private nature.

Internet Services

World Wide Web

Other than the Hypertext Markup Language (HTML), today's Web pages have little in common with those
in the early days of the WWW.

FTP (File Transfer Protocols)

FTP sites used to be the primary way files were transferred over the web, but now HTTP is the most common method.

In most cases, FTP is a more efficient way of transferring large files than either HTTP or electronic mail. FTP was designed specifically for file transfer. Many organizations maintain an FTP site in addition to their Web site.

You need an FTP utility, known as an FTP client, to use FTP for file transfers. An FTP utility will let you connect to an FTP server, navigate through server directories (depending on your access permissions), and upload and download files.

Windows 9x and Windows 2000 both include a simple FTP client. The client is not installed automatically, but can be installed through the Control Panel Add/Remove programs utility.

Electronic mail (e-mail) service

E-mail is probably the most widely used and relied on of all Internet services.

E-mail provides rapid, worldwide communication. In addition to text messages, most e-mail clients also support file attachments and HTML-formatted messages. Most also support embedded documents, such as audio or video files.

E-mail service is provided through:

• Corporate or Organizational Mail Servers
• ISPs
• Public Mail Services, such as hotmail.com

• Jdoe@mycompany.com
• j.doe@organization.org
• mailguy220@publicmail.com

DNS servers

DNS servers are used to provide name resolution for URLs and other host names on the Internet. They are also commonly used on private LANs and WANs for the same purpose, to provide IP addresses for requested host names.

DNS servers work in the background. As long as they are working properly, users may never realize they are there. Despite this, they provide a key service for network and Internet navigation.

Symbolic names, like cannot be used for Internet navigation.They must first be resolved to IP addresses. When you enter a URL in a Web browser, the host name is forwarded to a DNS server for resolution. Actually, the name may be forwarded through multiple DNS servers before it is finally resolved.

The IP address is then returned to your browser, and the IP address is used to locate and connect to the requested host.You can also connect to an Internet location through its IP address instead of its URL.

Internet Protocol

The TCP/IP suite is the underlying Internet protocol. TCP/IP was originally designed specifically for use with the Internet. FTP and HTTP, are implemented as part of the TCP/IP suite.

Internet Browser

An Internet browser is the software that navigates the Internet. More, specifically, an Internet browser is designed to navigate and display World Wide Web pages, but most Internet browsers offer at least Internet newsgroup and FTP transfer support.

Several Internet browsers are available, but the two you will probably see the most often are Microsoft Internet Explorer (IE) and Netscape Navigator.

When you launch a browser, it will attempt to connect to its home page, which is simply a default first page. Both IE and Navigator will configure themselves with a home page

Many Web sites have default pages that are designed specifically for use as home pages. They can be customized to meet a user's needs and preferences.

Searching the Internet

You will not always know the URLs of Web sites you want to visit. Search engines give you a way to search the Internet for the information you need without the need to know URLs. Many search engines are available, and new ones appear regularly.

Some of the more commonly used search engines include:

• Yahoo
• Excite
• AltaVista
• GoTo
• MSN Search

TCP/IP

The TCP/IP suite is the current de facto standard for both local and wide area networking.

Most operating systems include TCP/IP support as a default selection when installing and configuring network support, including current Windows family operating systems.

In addition to being used as a communication protocol on private networks, TCP/IP is required for Internet access.

TCP/IP is used as the primary or sole communication protocol on nearly all new PC network installations. In addition, most existing PC networks either have converted or are converting to TCP/IP.

TCP/IP is a routable protocol that can be used in nearly any LAN or WAN networking configuration.

TCP/IP suite

TCP/IP is a protocol suite, meaning that it includes several specialized protocols, network services and network support utilities.

Two terms that need additional explanation are "connectionless protocol" and "connection-oriented protocol."

A connectionless protocol does not provide a guaranteed delivery. In other words, there is no guarantee that a packet will be received by the destination system.

A connection-oriented protocol provides packet acknowledgment and sequencing.

Acknowledgement means that the receiving system will respond to the sending system when the packet is received.

Packet sequencing means that if packets are received out of order, the receiving system will place them in the proper order and reconstruct the data.

TCP/IP configuration fundamentals

At minimum, each system in a TCP/IP network must be configured with an IP address and a subnet mask.

The IP address is expressed in a four-part dotted decimal format, such as: 192.162.102.221

The subnet mask determines which part of the address is used as the network address and which is used to identify a specific host on the network.

For example, your subnet mask might resemble the following:
255.255.255.0

The network address identifies a general location in the network and the host address identifies a specific system.

You can compare these elements to the address on a letter. The network address works like the city and state address, identifying a general location.

The host address is analogous to the street address and house number, identifying a specific location.

When configuring a system for use on a TCP/IP network, you may be required to enter the IP address for one or more DNS servers, one or more WINS servers or both.

You do not have to provide the IP address for a DHCP server, but you must identify any systems that will be receiving their IP addresses and other configuration information through DHCP.

Term	Description
Domain name system (DNS) service
Windows internet name service (WINS)
Dynamic host configuration protocol (DHCP) service

Test and troubleshooting utilities

The Ping utility is used to test communication with another TCP/IP host, either on your private network or somewhere on the Internet.

The basic syntax for using Ping is:

Two additional protocols, Data Link Control (DLC) and Appletalk, deserve brief mention. These protocols will be used in some network configurations, but are usually not required.

DLC is a non-routable protocol that has traditionally been used for connecting to network printers that are directly connected to the network. Most network printers now support TCP/IP, making DLC unnecessary.

The AppleTalk protocol is required only when supporting Apple Macintosh systems that are configured for an AppleShare or AppleTalk network.

Multiple protocols are suggested only in network configurations where their support is required.

For example, if a system is part of a Windows TCP/IP network and also needs to access a legacy NetWare server, you would need to install both TCP/IP and NWLink on that system.

When multiple protocols are installed on a system, you can specify binding. Binding refers to how protocol support is associated with a network adapter. It gives you a way of limiting protocol support if a protocol is not needed on one of the adapters.

One of the problems with supporting multiple protocols is increased background traffic on a network. This is not a serious concern on most networks, but could affect network performance on a very active network.

More details on protocol properties

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