8
Introduction to Broadband
Router Technology
A router is a device that forwards data packets from a source to a destination.
Routers can work on Open System Interconnection (OSI) layer 3, which for-
wards data packets using an IP address and not a MAC address. A router will
forward data from the Internet to a particular computer on your LAN.
The information that makes up the Internet gets moved around using routers.
When you click on a link on a web page, you send a request to a server to show
you the next page. The request sent and the information received by your com-
puter is moved from your computer to the server using routers. A router also
determines the best route that your information should follow to ensure that the
information is delivered properly.
A router controls the amount of data that is sent through your network by elimi-
nating information that should not be there. This provides security for the com-
puters behind your router because computers from the outside cannot access
or send information directly to any computer on your network. The router deter-
mines which computer the information should be forwarded to and sends it. If
the information is not intended for any computer on your network, the data is
discarded. This keeps any unwanted or harmful information from accessing or
damaging your network.
Introduction to Firewalls
A firewall is a device that sits between your computer and the Internet that pre-
vents unauthorized access to or from your network. A firewall can be a com-
puter using firewall software or a special piece of hardware built specifically to
act as a firewall. In most circumstances, a firewall is used to prevent unautho-
rized Internet users from accessing private networks such as corporate LANs
and Intranets.
A firewall watches all of the information moving to and from your network and
analyzes each piece of data. Each piece of data is checked against a set of
criteria that the administrator configures. If any data does not meet the criteria,
that data is blocked and discarded. If the data meets the criteria, the data is
passed through. This method is called packet filtering.
A firewall can also run specific security functions based on the type of applica-
tion or type of port that is being used. For example, a firewall can be configured
to work with an FTP or Telnet server. Or a firewall can be configured to work
with specific UDP or TCP ports to allow certain applications or games to work
properly over the Internet.
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