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Routers are physical devices that join multiple wired or
wireless networks together. They are responsible for
routing data packets from source to destination within
the LAN, and for providing connectivity to the WAN.
Technically, a wired or wireless router is a Layer 3
gateway, meaning that the wired/wireless router connects
networks (as gateways do), and that the router operates
at the network layer of the OSI model.
Home net workers often use an Internet Protocol (IP)
wired or wireless router, IP being the most common OSI
network layer protocol. An IP router such as a DSL or
cable modem broadband router joins the home's Local area
network (LAN) to the Wide Area network (WAN) of the
Internet.
By maintaining configuration information in a piece of
storage called the "routing table" or “configuration
table”, wired or wireless routers also have the ability
to filter traffic, either incoming or outgoing, based on
the IP addresses of senders and receivers. 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
A router, then, has two separate but related jobs:
• 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 intended destination.
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. |
