switch

Switch is a networking hardware that connects devices on a network by using packet switching to receive and forward data to the destination device. Image

Why do we need switches?

If we connect two computers using only cables it there are some big limitations:

  1. distance (signal will degrade with more distance)
  2. cable can connect only two devices

These problems can be solved with other more simple devices. Distance - use twisted cables - which will provide much more stable distance - active device - amplifier/repeater which can amplify the signal

Cable can connect only two devices We introduce multiport repreater - hub - this device does not understand data going through them and it is basically just a signal amplifier

This seems much easier. The problem is collision. In a system of hubs - only one device is allowed to transmit data. If more device attemt to pass data it will result in a collision.

Collision domain - network segment where transmitted data can collide with one another

This means we can not use hubs for the internet. We need to split the collision domains.

Main job

So the main job of a switch is to divide the network into multiple smaller segments, each of which is a seperate collision domain. This means that devices in one collision domain cannot interfere with the traffic in another.

Data passing

To pass data between computer in a network we need to be able to identify each end device.

We will use MAC addresses for that. If we want to send data from PC1 to PC3, we will use frame (simple container for data)