This topic is extremely important for the flow of data in a network, and it can be quite frustrating when people try to say that a network switch and a network hub are one and the same. That couldn’t be further from the truth; there is SO MUCH difference between the two devices.
This basic overview hopes to explain the main differences between hubs and switches, and to give you a better understanding of the two.
First of all, lets say hubs are ok in a small network. An office with around 10-15 network devices can work reasonably well with a hub.
A Hub
Hubs basically work by regenerating signals. So if one computer wants to send data to another computer, EVERYONE on the network gets the data – it is then only accepted by the intended recipient. Unicast, Multicast, and Broadcast traffic are all treated the same – data just goes out to everybody connected to the hub.
A hub has only 1 “Collision Domain”. In a nutshell, this means that only 1 device can Send or Recieve data at the same time. It also has only 1 “Broadcast Domain”; i.e. 1 broadcast travels to every computer on the hub network.
Devices connected to the hub LISTEN for data on the line, to make sure it is clear before they transmit. If 2 devices then try and transmit at the same time then you get a COLLISION.
As you add more and more devices, somewhere between 20 and 30 computers will start to cause real problems in a hub network. This is because more than one device is listening at the same time, meaning increased chances of more than one device sending at the same time, and you get collisions. The “collision” light on the hub will will start to flash at this point.
When a collision is detected, all data transmission is “Jammed”. Once it’s restarted, data is retransmitted until a collision happens again. And on it goes….
You can start to see now how data transmission is really slowed down in a hub-network.
A Switch
Each port on a network switch is its own Collision Domain (remember that from earlier?). Every single device that’s plugged into a switch can send data at exactly the same time, and you won’t get any collisions.
Since each port is its own collision domain, each device can send AND recieve at the same time. This is known as FULL DUPLEX – hubs only work at HALF DUPLEX (send OR recieve at same time).
A switch also uses a MAC address table to learn and store MAC addresses of devices on the network. Using this, it sends data to the intended recipient device rather than broadcasting to all devices like a hub would do.
There are lots of other benefits of a switched-network, such as splitting it up further via subnetting, but I guess there’s more than needed in there for you to see the point hopefully.
Hubs and Switches – they’re simply not the same.