What does a
router do? - It provides you with your network, Internet, and security
Two Types of Routers
There are 2 types of routers:
- the network engineering type of router
- the broadband router common in home and small
Network Engineering Type of Router
The job of the router is to connect networks and
route Internet data to the right place and make sure it gets there.
The Internet works by breaking data into small
packets which contain data and the address of the destination of the
packet. A computer on the Internet sends out a stream of packets
targeted to an address indicated by a set of 4 numbers between 0 and
255, for example, 220.127.116.11. It uses a router to send the information
to the right place.
How does a router work? It looks at the
destination address and checks if it is for the network that it is
connected to. If it is not, it send the data to the most appropriate
router that it is connected to. It has a table inside its memory that
identifies the range of ip addresses that belong to its own network so
that if, for example, the range of its network was 18.104.22.168 to
22.214.171.124. the ip address of the packet 126.96.36.199 would fit in
and belong to one of the computers on its network. If not, the router
has tables of other routers that it is connected to in different parts
of the world so that if the 23.32 part of the address was pointing to
California, it would send the packet to the router closest to
California. This would get the packet a step closer to its destination.
The second router would do the same type of logic. The number of jumps
between routers involved is called hops. The less hops, the faster that
the data gets where it needs to go.
The router expects confirmation that the packet
made it to the next hop. If it doesn't get it, it has alternate routes
that it can use to send the packet again. This prevents a breakdown of
a portion of the Internet from stopping delivery of data.
For detailed information about this type of router
see How Routers Work.
Home Network Broadband Router
The typical home or small office router also does
the same function as the network engineering router and it connects 2
networks, your network and the Internet.
However it also does a number of other things that
are are not all standard router functions.
It has the following features:
- ip sharing
- NAT translation
- The switch connects the computer network components in an efficient
manner and only sends the data where it is intended to go unlike a hub.
It knows the MAC address (i.e. hardware address) of each item and so
when the desktop computer wants to talk to the laptop, it only sends
the message to the laptop and nothing else. The typical broadband
router acts as a router and a switch.
- Your ISP (Internet service provider) has provided you with an
official address on the Internet. You only get one and that's the one
that any system on the Internet sends to and receives from. However,
the router can fake out the world and allow multiple computers within
your network to use the same ip address. This allows all the computers
to share the internet. The router remembers which computer on the
outside a member of your network was talking to, and when data comes in
from that computer, it knows which internal computer is expecting it
and sends it there.
- In order to support IP sharing, the router must assign IP addresses
to the devices on the network to be able to identify them separately. A
non routable (something like an unlisted address) ip address is
assigned to each device which the router keeps track of. The router
converts the the internal ip address of the device to the single
outward facing IP address so that it looks to the outside world like
the communication is coming from this ip address. This is called NAT
(Network Address Translation).
The router keeps track of all activities of each
device so it knows which one is expecting input and sends appropriate
information to it.
Dynamic Host Configuration
Protocol (DHCP) - Assigning an internal ip address
to all the devices on the network can be tedious to do manually and can
also lead to mistakes if one assigns the same ip address to 2 devices.
DHCP allows a user to define a range of ip addresses that the router
will use to assign a free ip a<li><a
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ddress automatically to any new device connected to the network. This
makes the process of ip assignment easy and error free.
Wireless routers broadcast their messages and anyone within range can
tune in. To prevent unauthorized use and stealing of proprietary
information it is necessary to send the information in code via
encryption. Routers provide various types of encryption including WEP,
WPA and WPA2. For more information about network security see computer
network security advice
Since the external ip address of your network is assigned to the router
when you install it, any malicious program or user will not be able to
get to any programs or data on your system because all they will see
will be the router. Additionally, the router is set up to reject and
information requests coming from the outside that weren't initiated by
something inside. This hides your network from those that you don't
want to see it.
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