Router is a term that a lot of us hear but few people outside of computer science have a true understanding of. Sure, it is that box that we plug into our modem that gives us wireless Internet. Of course, that definition is simplistic at best and kind of like saying that a car can be summed up as a box on four wheels. If you want a more basic understanding of what a network router is, then this piece can help you. We’ll take a look at a more detailed definition of a router and a look at some of the common types you might encounter, as well as some that few will ever see but that are still worth knowing about.
A More Detailed Definition of a Router
A router is a networking device that has specific software and hardware which has been designed for the routing and forwarding of information. What this means is that routers are specialized devices for transmitting data. As a general rule, routers operate on two different planes: the control plane and the forwarding plane, both of which deal with interfaces and outbound data. A router's primary job is to provide connectivity, a function which you may be most familiar with in your own home from your wireless network setup. Routers, of course, are also used by larger systems including your original Internet service provider.
The Types of Routers
For the most part, there are four basic types of routers that you may encounter on a computer network.
The Edge Router
The edge router is, as you may have guessed, one that sits on the edge of an ISP's network. It is the edge router's job to route data externally to either another service provider or a large enterprise's autonomous system. These are most common in the world of business.
Subscriber Edge Router
The subscriber edge router is similar in function to standard edge router except in its function on the edge of the subscriber’s network and that it is used to transmit data into the subscribers network.
Inter-Provider Border Router
Figure provider border routers are used to interconnect ISPs. These routers maintain what is known as the BPG which allows two routers, such as an edge router and the subscriber edge router, to talk to each other and transmit data.
A core router is used inside an ISP and transmits internally. They may be used to connect as your border routers or simply to pass signals within the network. While traditionally the core has been in the backbone of the system, as the design of modern networks changes, finding the core can be more and more challenging. Generally where the drivers are now is consider the core.
It is important to know that there are two main sizes of routers. The first are small office and home office (SOHO) connectivity routers. These are the routers that most people are familiar with. They allow you to connect to your cable or DSL on a small scale. Enterprise routers, on the other hand, are usually confined to large companies and universities as well as research facilities and ISPs. While these allow for basically the same function, they are infinitely more powerful.