Most communication between computers cannot be fully transacted in one packet. For example, sending a megabyte file will require breaking it into many packets, which allows other users to get some time on the wire and which also keeps any errors from causing the one huge packet to be wasted.

There are two main approaches to sending a message that is broken into many packets over a network. The first is called connection-oriented because is based on the idea of a telephone connection. Communication that needs to be totally reliable, such as sending files or remotely logging in, uses connection-oriented protocols, such as TCP.