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Tuesday, June 30, 2009

Quick description - How does a Router work?

Here is a technical description of how a router works. This would make sense if you have already an understanding of the network protocols.
The layers 2 and 3 of the OSI model i.e. Data Link layer, is where the Ethernet protocol, MAC addresses and switches fit in.
Layer 3, the Network layer, is where the IP protocol, IP addresses and routers fit in. All traffic is sent from your computer, starting with Layer 7 (your network application) and going down to Layer 1 (physical). With the physical layer, the traffic is going across your network medium.
Traffic goes to a router only if it is not on your local LAN. Routers work primarily at Layer 3 but must understand Layers 1-3, at a minimum. Many routers understand traffic all the way up to Layers 4-7 in varying ways.
One of the tools a router uses to decide where a packet should go is a configuration table. A configuration table is a collection of information, including:
• Information on which connections lead to particular groups of addresses
• Priorities for connections to be used
• Rules for handling both routine and special cases of traffic
Internet data, whether in the form of a Web page, a downloaded file or an e-mail message, travels over a system known as a packet-switching network. In this system, the data in a message or file is broken up into packages about 1,500 bytes long which includes information on the sender's address, the receiver's address, the package's place in the entire message, and how the receiving computer can be sure that the package arrived intact. Each data package, called a packet, is then sent off to its destination via the best available route -- a route that might be taken by all the other packets in the message or by none of the other packets in the message.

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