Switches and Hubs...
Posted on 2004-08-28
I was recently asked what the difference was between a switch and a hib. I wasn't totally sure, but as the informal IT guy in the office no-one else was going to venture a response(!). I came up with the following...
HUB - Connects multiple PCs in a small office. All connections get access to all resources (i.e. bandwidth) all the time, so if two PCs send a packet at the same time then they 'collide' and have to be resent. On small networks this is better than using a switch since collisions are rare and therefore the retransmission is not a problem.
The SWITCH definition I'm a little more unsure on...
SWITCH - Enables connections from multiple sources (usually other hubs, rather than PCs). Switches allocate the available resources via (in effect) time slicing the available bandwidth between connections, i.e. a 100MB switch with 4 connections will give each connection a 100MB link for 1/4 of the time. This eliminates collisions so on busy networks this is better than retransmissions, ie. when the available bandwidth is being used almost all the time to the maximum.
Therefore hubs are used in small offices and switches for connecting multiple offices together (usually over a remote link) or many departments to one server. If a switch was used in an office instead of a hub, althought there would be no 'collisions' overall speed will be slower since the switch is only offering a % of all resources to each user, rather than all of it all the time.
Therefore a good time to use a switch is when network collisions mean that the throughput of the hub is less than if the bandwidth was timesliced between connections.
Am I anywhere near?