Routers - by Curt Franklin
Routers are specialized computers that send your messages and those of
every other Internet user speeding to their destinations along thousands
of pathways. In this article, we'll look at how these behind-the-scenes
machines make the Internet work.
A Routers Job
The router ensures that information doesn't go where it's not
needed. This is crucial for keeping large volumes of data from clogging
the connections of "innocent bystanders."
The router makes sure that information does make it to the
In performing these two jobs, a router is extremely useful in dealing with
two separate computer networks. It joins the two networks, passing
information from one to the other and, in some cases, performing
translations of various protocols between the two networks. It also
protects the networks from one another, preventing the traffic on one from
unnecessarily spilling over to the other. As the number of networks
attached to one another grows, the configuration table for handling
traffic among them grows, and the processing power of the router is
increased. Regardless of how many networks are attached, though, the basic
operation and function of the router remains the same. Since the Internet
is one huge network made up of tens of thousands of smaller networks, its
use of routers is an absolute necessity.
How does the Routers Work?
The router is the only device that sees every message sent by any computer
on either of the company's networks. When the animator in our example
sends a huge file to another animator, the router looks at the recipient's
address and keeps the traffic on the animator's network. When an animator,
on the other hand, sends a message to the bookkeeper asking about an
expense-account check, then the router sees the recipient's address and
forwards the message between the two networks.
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,
Information on which connections lead to particular groups of
Priorities for connections to be used
Rules for handling both routine and special cases of traffic
Let's look at what a very simple router might do. Imagine a small company
that makes animated 3-D graphics for local television stations. There are
10 employees of the company, each with a computer. Four of the employees
are animators, while the rest are in sales, accounting and management. The
animators will need to send lots of very large files back and forth to one
another as they work on projects. To do this, they'll use a network.
When one animator sends a file to another, the very large file will use up
most of the network's capacity, making the network run very slowly for
other users. One of the reasons that a single intensive user can affect
the entire network stems from the way that Ethernet works. Each
information packet sent from a computer is seen by all the other computers
on the local network. Each computer then examines the packet and decides
whether it was meant for its address. This keeps the basic plan of the
network simple, but has performance consequences as the size of the
network or level of network activity increases. To keep the animators'
work from interfering with that of the folks in the front office, the
company sets up two separate networks, one for the animators and one for
the rest of the company. A router links the two networks and connects both
networks to the Internet.