11 August 2008

Switches for Newbies

If you want to connect more than one computer in your network, you'll need switch. Yea, everyone knows that, but how exactly does switch better than other devices such as hub or bridge?

By the way, the picture on the left is a symbol used for depicting a switch, you will usually use this picture to design your network.

Back again on switches, first you need to know about collision in a network. In a network using hub, every data that your computer send is forwarded to all ports in the hub.
For example if computer A sends a data and at the same time computer B also sends a data, the data will collide and cause the hub to stop all transmissions from every device connected to it. This condition not only make the network slower but also pose a security problem.
If one computer send a data then every other computers can "listen" to that packet.

Switches are not the same as Hubs, they remember every computer that plug into their ports. So they will send packets only to the destination computer.
What the switches remember are the MAC addresses of the computers connected to them.
MAC address is a unique value given by the vendors, each vendor has a unique value and unique serials for their products.
There are rarely any two similar MAC address unless because of manufacture defect.

The switches are able to segment collision, meaning that every collision is limited only to the ports that computers are connected.
How the switches do that? well hubs can't do this because they use 1 pair (2 cables) of UTP cable for transmitting and receiving data.
While switches use 1 pair of cable to transmit data and 1 pair to receive data, so there shouldn't be any collision.

Get this, if you buy a 100mbps per port switches, you by no charge will get 200mbps per port, sweet.
How come? because they use full 100mbps for transmitting and 100mbps for receiving data.

Now what is the different between switches and bridges? basically bridges do the same thing as switches, they segment collision.
But switches have much more ports than bridges, that's why switches are often called multiport bridge.