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Network Packets

Files are never sent across a network in one piece. They are broken into "bite sized" chunks of data and sent individually. Each "chunk" is a packet. Packets (sometimes called 'frames' or 'datagrams') usually contain:

• the address (identity) of the computer sending the data
• the address of the computer that is to receive the data
• the data itself
• some way, such as a 'checksum' for the receiving computer to determine if the data contents of the packet has been damaged in transit.

Why break files into packets? The first reason is that if any single bit of a large file is damaged during communication, the entire file can be wrecked. If you sent a file in one piece and the slightest damage occurred, you'd need to send the entire file again. By breaking it into packets, and if any damage happened to one of them, then only that small packet would need to be sent again. Another reason is that when sending files over the Internet, you can send many packets in a very fast sequence, and each one will take the most efficient route to the destination simultaneously. This can speed up communications.

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