IP and MAC addresses

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IP addresses

IP is short for Internet Protocol.

A 'protocol' is a set of rules for doing something. In this case it is the task of being able to uniquely identify every computer connected to an IP based network.

The way this is done is to assign a long number to each computer made up of 4 bytes. This normally takes the form of four, three digit numbers separated by a dot. Like this

255.168.101.004

Of course behind the scene this is actually a 32 bit binary number (4 bytes).

Each number group in the address sub-divides the network to which the computer is connected with the final number (004 above) being the actual computer.

The Internet is a vast collection of smaller networks each connected to one another through routers.

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MAC addresses

Short for Media Access Control address.

This is the unique identifier assigned to a network card or Wi-Fi adapter.

The code identifies the card and also the maker of that card.

It is a 48 bit binary number stored within the card hardware itself.

To make it a bit more people friendly the MAC address is usually quoted as a set of six hex number like this:

MAC address: 0A-14-FF-32-11-23-97

If you set up a WiFi one of the things you can do to improve security is to only allow devices with certain MAC addresses to connect to the network.

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Protocols

This is the word given to a set of rules that determine how a task is carried out.

In this case it is a set of rules that describe how data is to be transmitted across the network.

A good protocol should handle these features:

- How to set up and stop a connection
- How to start and end a message
- How to deal with corrupted data
- How to format the data

With these rules in place, hardware makers are sure their devices will work on a network using that protocol. Software authors are confident that their networked applications will work.

An extremely popular protocol is called TCP / IP on which the world wide web is based. But it is by no means the only one that people use for their networks.

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Packets

The basic idea behind the TCP / IP networking is that data is broken up into independent small packets containing a certain amounts of bits. It is up to the network designer as to how large of small the packet needs to be, typically they start from 512 bits upwards.

These packets travel through the network and get re-assembled in the right order on the receiving computer.

Each packet contains the IP address of the receiving computer, the data itself along with some control and error codes.

Splitting the data into packets makes data transmission very reliable. If one part of the network is broken, the packets are guided around the problem area by routers within the network. If a packet is missing, then the receiving computer asks for that one to be re-sent.

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