Friday, October 14, 2011

Routers - How They Work

If you've been brought up in the 21st century then you probably take a lot of things for granted that 30 years ago people just didn't have. One of those things is the Internet and its ability to be able to connect people from all over the world and allow them to interact with each other in a variety of ways including sending email, visiting web sites, joining forums, attending online chats and countless other things. But none of this would be possible if it weren't for a device that most people have never seen and probably don't even know exist, called a router.

Routers are pieces of equipment that send messages from everyone connected to the network along thousands of different pathways. We're going to take a behind the scenes look at exactly how these routers work.

Let's say you're sending an email to a friend of yours who is living across country or even in another part of the world. How does the email know to end up on your friend's computer instead of all the other millions of computers all over the world? A good part of the work to get these messages from one computer to another is handled by routers. Rather than pass messages within networks, routers pass messages from one network to another.

To get an idea of how this works, let's take a very simple example.

Let's say you have two departments. Department A with 5 employees and Department B with 5 employees. Let's say that Employee 1 from Department A wants to send an email to Employee 3 at Department B. Each department is part of its own network of computers. A router links the two networks together so that they can communicate with each other. It is the only piece of equipment that sees both networks. Many people ask, why not just make one network? The simple answer is that if the two departments do two completely different jobs for the company and send massive amounts of info within the department, you don't want to slow down the other department with the one department's info. To ease what they call the "traffic burden" the two departments are separated into two networks with a router put between them to connect them just in case they do want to communicate for some reason.

The way the router knows what to send where is with what is called a configuration table. These configuration table consists of info on which connections lead to which addresses, priorities for each connection, and rules for how to handle the passing of info between networks. The router then has two basic jobs. The main task is to make sure that information doesn't go where it's not needed so that the volume of data doesn't clog up the network and the next task is to make sure the information goes to where it's supposed to go.

To simplify how this happens, the router looks at the destination address of each packet sent from the source location. It checks its table to see where this address is and sends each packet to that address, bypassing all the other addresses in the network so as not to slow the network down.

In future articles we'll take a more in depth and technical look at how packets are actually routed. Get on your thinking gear for this one.

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