Introduction to TCP/IP

TCP/IP and protocol definitions

Anyone who is in anyway familiar with modern computer networks will have inevitably heard of the infamous TCP/IP. TCP/IP is an acronym for Transmission Control Protocol / Internet Protocol. However, this is misleading, because the term TCP/IP actually refers to a group of protocols. So, put simply, TCP/IP can be defined as a group of protocols used in TCP/IP networks, and it is this suite of protocols which allows the Internet to exist. (Yes, I realise I've just created a somewhat circular statement.)

Fine, so it's a group of protocols. But what is a protocol? A protocol is to a computer network much like a spoken language is to you or I. It's a set of rules that allows networked devices to be able to coherently communicate with each other.

Other protocols?

Note that I stated above that TCP/IP is actually a suite of protocols. This is true, because TCP/IP also gives us protocols like FTP - File Transfer Protocol (allows us to send and receive files), SMTP - Simple Mail Transfer Protocol (which allows us to email), and HTTP - Hypertext Transfer Protocol (which allows us to access the World Wide Web). There are others, but these are some of the more well-known 'application' protocols.

What's so great about it

Perhaps the most important point to note is that TCP/IP is a routed protocol. This means that you need only specify source and destination addresses. Those addresses can be in the same room or on opposite sides of the world; it doesn't matter. The message you send doesn't need to know what route to take to reach the destination, and neither do you. The message is simply sent, one hop at a time, from node to node. At each stop, the current node determines which node is the next in the chain and forwards it that far. For a full discussion of how routing is achieved, make sure you check out the section on bridges, switches and routers.

What's next

The next topic looks at IP addresses and subnetting.