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IP packets

On the massive network known as the Internet, computing devices send all kinds of messages to other computing devices. A message might be a tiny ping to check if another device is online or a message could be an entire webpage.
But there's a limit to how large a message can be, since there's a limit to how much data can be reasonably transmitted at once by the physical network connections between devices.
That's why many networking protocols split each message into multiple small packets. The Internet Protocol (IP) describes the structure of the packets that whizz around the Internet.
Each IP packet contains both a header (20 or 24 bytes long) and data (variable length). The header includes the IP addresses of the source and destination, plus other fields that help to route the packet. The data is the actual content, such as a string of letters or part of a webpage.
You can think of IP packets like postal letters: the header is the envelope with all the routing information that's needed by the post office, and the payload is the letter that's read only by the recipient.
Just like the postal system routes postal letters around the world, the Internet Protocol routes IP packets around the Internet.
In the next article, we'll learn much more about routing on the Internet.
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