TCP/IP
TCP/IP is the software used on the Internet to pass information from machine to machine and from network to network. It contains two components, Internet Protocol (IP) and Transmission Control Protocol (TCP).
IP breaks up information and puts it into software packets that can move across networks. As long as machines on each end of the connection understand IP, they can accept packets from other computers and they can send packets along. A computer that wants to send information on the Internet uses IP to divide the information into packets. A computer that receives information reassembles it from the packets it receives.
TCP works with the IP protocol to guarantee that information is transmitted correctly across the Internet. The TCP software makes sure that the packets of information get properly reassembled when they reach their Internet destination. TCP also requests that lost or damaged packets be resent to the destination computer.
IP Addressing
Each computer on the Internet is assigned a unique numerical address, called its IP address. Each packet moving around the Internet contains the IP addresses of the sender computer and the destination computer. Using the IP addresses, the routers move the packets across the Internet until they reach their destination machines.
Where does your IP address come from? When an organization connects to the Internet, it gets a set of IP addresses from the Internet authority. Your Internet service provider or system administrator will assign your machine an IP address. If you are using a PPP/SLIP account, your PPP/SLIP provider will assign your computer an IP address.
Servers and Clients
Every computer program that communicates on the Internet is either a server or a client.
A server offers a service to other machines on the network. For example, a file server contains files of interest to users around the network — the service it offers is the storage and retrieval of the files. There are thousands of file servers on the Internet, some offering files of a particular type, such as artwork (a file can contain an image), weather maps, or tourism information.
A client requests a service from a server. Most services are designed so that specialized client software must be running to interact with the server. For example, to get a file from a file server, a client program on your machine must format and send the request to a program running on the server. The server program locates the file on the server machine and sends a copy of it back to the client program which saves it or opens it for immediate use. The client and the server use a common method for communicating and for passing the file from one machine to another, called a protocol.
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