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What is TCP/IP?

The internet uses a set of protocols called TCP/IP, which stands for Transmission Control Protocol/Internet Protocol. In a TCP/IP network, messages are broken into small components called datagrams that are then transmitted through various interlocking routes and delivered to their destination computers. Once received, the datagrams are reassembled into the original message. Datagrams are also referred to as packets. Sending messages as small components has proved to be far more reliable and faster than sending them as one large bulky transmission. With small components, if one is lost or damaged, only that component needs to be re-sent, whereas if any part of a large transmission is corrupted or lost, the entire message has to be re-sent.

On a TCP/IP network such as the Internet, each computer is given a unique address called an IP address. The IP address is used to identify and locate a particular host-a computer connected to the network. An IP address consists of 4 segments, each pair separated by a period. The segments consist of numbers that range from 0 to 255, with certain values reserved for special use. The IP address is divided into two parts, one that identifies the network and the other that identifies a particular host.

For example, an IP address breaks down in the following way.

192.168.187.4 - IP Address

192.168.187 - Network Identification

4 - Host Identification

An IP address is officially provided by the Network Information Center (NIC) that administers the Internet. You can obtain your own Internet address from the NIC, or if you are on a network already connected to the Internet, your network administrator can assign you one. If you are using an Internet service provider, the ISP may obtain one for you or, each time you connect, may temporarily assign one from a pool they have on hand.

All hosts on the Internet are identified by their IP addresses. When you send a message to a host on the Internet, you must provide its IP address. However, using a sequence of 4 numbers of an IP address can be very difficult. They are hard to remember, and it's easy to make mistakes when typing them. To make it easier to identify a computer on the internet, the Domain Name Service (DNS) was implemented. The DNS establishes a domain name address for each IP address. The domain name address is a series of names separated by periods, eg. www.btinternet.com. Whenever you use a domain name address, it is automatically converted to an IP address that is then used to identify that Internet host. The domain name address is far easier to use than it's corresponding IP address.

A domain name address needs to be registered with the NIC so that each computer on the Internet will have a unique name.

The conversion of domain addresses to IP addresses used to be performed by each indivdual host. And for a few frequently used addresses for which you know this can still be done. However, so many computers are now connected to the internet that domain name conversion has to be done by special servers known as domain name servers. A name server holds a database of domain name addresses and their IP addresses. If a name server does not have the address, then it may call on other name servers to perform the conversion. Aprogram on your computer called a resolver will obtain the IP address from a name server and then use it in the application where you specified the domain name address.

This was plagerised from " Linux The Complete Reference Third Edition" by Richard Petersen. Published by Osborne.

   

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