A simple set of ideas makes it possible for computers and networks all over the world to share information and messages on the Internet:
Break up every piece of information and message into pieces called packets, deliver those packets to the proper destinations, and then reassemble the packets into their original form after they ve been delivered so the receiving computer can view and use them. That s the job of the two most important communications protocols on the Internet: the Transmission Control Protocol (TCP) and the Internet Protocol (IP). They are frequently referred to as TCP/IP.
TCP breaks down and reassembles the packets, whereas IP is responsible for ensuring the packets are sent to the right destination.
TCP/IP is used because the Internet is what is known as a packet-switched network.
In a packet-switched network, there is no single, unbroken connection between sender and receiver. Instead, when information is sent, it is broken into small packets, sent over many different routes at the same time, and then reassembled at the receiving end.
By contrast, the telephone system is a circuit-switched network. In a circuit-switched network, after a connection is made (as with a telephone call, for example), that part of the network is dedicated only to that single connection.
By contrast, the telephone system is a circuit-switched network. In a circuit-switched network, after a connection is made (as with a telephone call, for example), that part of the network is dedicated only to that single connection.
For personal computers to take full advantage of the Internet, they need to use special software that understands and interprets the Internet s TCP/IP protocols. This software is referred to as a socket or a TCP/IP stack, and it is built in to any computer that you buy, so you don t need to do anything special to access it. For PCs, the software is called Winsock. For Macintoshes, the software is called MacTCP. In both cases, this software serves as an intermediary between the Internet and the personal computer.
There are two primary ways that a computer can connect to the Internet and then use TCP/IP protocols through a direct connection via a local area network (LAN), cable modem, or DSL line; or by dialing in using a modem. To connect via LAN, cable modem, or DSL line, a computer needs a network card. To communicate with the network and the Internet s TCP/IP protocols, the network card requires a hardware driver software that mediates between the network and the network card. When the computer instead dials in to the Internet using a modem, the computer must use one of two software protocols: either Serial Line Internet Protocol (SLIP) or Point-to-Point Protocol (PPP). These protocols do the job of communicating with the Internet s TCP/IP protocols.
How the Internet s Basic TCP/IP Protocols Work
The Internet is a packet-switched network, which means that when you send information across the Internet from your computer to another computer, the data is broken into small packets. A series of switches called routers sends each packet across the Net individually. After all the packets arrive at the receiving computer, they are recombined into their original, unified form.
Two protocols do the work of breaking the data into packets, routing the packets across the Internet, and then recombining them on the other end:
The Internet Protocol (IP), which routes the data, and
the Transmission Control Protocol (TCP), which breaks the data into packets and recombines them on the computer that receives the information.
Because IPv4 uses only 32 bits for its IP addresses (called its address space), the number of total unique IP addresses is limited. IPv4 addresses are four numbers, separated by dots. Each number can only be up to 256. One example of an IPv4 address is 69.37.119.8. When the Internet was first designed, its creators never imagined that the address space would ever fill up, which is why they designed it the way they did.