Network Information and Concepts
Computer Network Hardware
A computer network is a collection of computers that are connected to each other via communication media such as copper wire, fiber optic cable, microwave transceivers, satellite transponders and dishes, etc. These communication media make it possible for the computers in a network to transmit information to each other. Since it is impossible to connect every computer in a network directly to every other computer, special network hardware enable data transmissions to be sent to special central locations and be distributed from there. These special locations serve the same function as a telephone switching station. In fact, telephone switching stations are used for precisely this purpose for most home computers that communicate via standard telephone connections. Many different types of hardware devices perform similar functions related to the distribution of computer transmissions. These include routers, switches and hubs.
The Internet
The Internet is a computer network that extends around the world. Computers and distribution hardware such as routers on different continents may be connected via transoceanic cables or satellite transponders. Individuals, organizations and businesses that wish to connect to the internet ordinarily must puchase access via a provider of internet services. The provider allows the customer to physically connect to the part of the Internet managed by the provider via a communications medium.
Web Pages
Web pages are simply computer files that adhere to a certain format. This format enables them to display text, graphics, sound and video in the manner we have become accustomed to seeing them through our web browsers. Anyone with a connection to the Internet may create and make available web pages. Larger organizations normally have the means to make their pages somewhat more accessible than the average user can from home. However, services exist for the average user at reasonable cost to make his/her web pages available on the service provider's computer.
The World-Wide-Web
The collection of computers that hold web pages and make them available to computers throughout the world is referred to as the World-Wide-Web (WWW). The World-Wide-Web may now consist of, possibly, more than a million such computers.
Search Engine
A search engine is a computer or collection of computers that run software (programs) that search the World-Wide-Web for information and make their findings available to web browsers across the world. Generic search engines generally seek any and all information almost indescriminately. Some computers specialize in certain types of information and do not consider themselves search engines in the strictest sense but provide a very similar service. For example, Infospace.com advertises itself as the best site in which to locate people. Some of the most popular generic search engines include Yahoo.com and Altavista.com.
Protocols
Protocols are conventions that are agreed upon to facilitate communication. For example, the common phone system that we are all accustomed to uses an agreed upon protocol. When a person wishes to initiate a communication the first person enters the number associated with the phone of the second person. This causes the phone of the second person to "ring". This is how the second person knows that someone desires to communicate. The second person then picks up the receiver and says 'Hello' to indicate that the first person may now begin to speak. The termination of the connection is initiated by one person saying the word 'Goodbye' and is confirmed via a like sign from the other person.
Computer protocols work in much the same way. (Almost) every computer on the Internet is identified by a number called an IP address (IP stands for Internet Protocol). In order for two computers to communicate with each other using the programs that we are most familiar with (Web browser, Ftp, Chat, etc.) each computer must use the other's IP address much the same way we must know the phone number of the person we wish to communicate with via the telephone. The difference is that in the phone system, once a phone connection is established we no longer need to use the phone number during the conversation. The Internet uses a connectionless protocol called IP and so the IP address must be specified in every message; much the way we must specify the address on an envelope whenever we send a letter to another person. Probably the most frequently used protocol, TCP, uses the IP protocol but is itself a connection-oriented protocol.
Domain Name Server
In addition to its IP address every computer on the Internet may have a name called a host name. Host names are mostly for the convenience of human beings. They are easier to remember than IP addresses and provide a means of better organizing computers within an organization. Unfortunately, even though a computer may have a host name the IP address is still required to communicate. The translation between host names and IP addresses is done by computers called Domain Name Servers. They act as Internet phone books. When a person wishes to connect his/her computer to another computer to, say, retrieve a web page he or she may specify the host name rather than the IP address of the other computer. The host name is then automatically forwarded to a domain name server which looks up the IP address for that name and sends it back to the computer that requested it. The computer now has the IP address it needs to connect to the computer with the web page.
ISP (Internet Service Provider)
Individuals desiring to connect to the Internet from home normally must request and purchase a connection to the Internet. ISPs are businesses that provide such a service. Ordinarily the ISP has purchased a high-speed connection to the Internet and sells slower speed connections to its many customers. Individuals normally connect to the ISP's high-speed data transmission lines via ordinary telephone lines although other faster connections are available at higher cost. The faster the connection to the Intenet the more costly it is.
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