What does a router do? - It provides you with your network, Internet, and security



Two Types of Routers

There are 2 types of routers:

  1. the network engineering type of router
  2. the broadband router common in home and small office networks

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, 23.32.123.4. 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 23.32.0.0 to 23.32.200.255. the ip address of the packet 23.32.123.4 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.

Network Engineering Router

However it also does a number of other things that are are not all standard router functions.

It has the following features:

  • switch
  • ip sharing
  • NAT translation
  • dhcp
  • encryption
  • firewall

Network Switch - 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.

router switchIP Sharing - 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.

NAT Translation - 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 href="voip-communications.html">Voip
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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.

Encryption - 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

Firewall - 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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5/22/2009

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