Difference between a network hub and a switch?

[Christopher Twigg]

A hub replicates traffic, whereas a switch switches traffic.  The
difference is that the hub is going to broadcast all traffic to every port
on the hub, whereas the switch only sends traffic along to the port that
needs it.  Switches are thus more intelligent, but considerably more
expensive.  A hub architecture requires that all machines on the LAN
segment be using the same speed ethernet, so if you wanted to have some
10mb/s machines and some 100mb/s machines on the same segment you have to
use a switch.  Switching also allows for full duplex ethernet, which
(potentially) doubles your throughput.  Switching also makes it a bit
more difficult to introduce sniffers on a LAN, so some people get them
as a moderate security measure.  For most people, though, using hubs is
quite sufficient; they're cheap and readily obtainable, and a 100mb/s
bridged network is about as fast as you could want (in fact, switches,
esp. cheap switches, add a small amount of overhead to packet movement
because most of them wait for an entire ethernet frame to come in before
resending it, whereas a hub will start sending as soon as they receive
the first bit).  Switches are great for high traffic situations, because
they increase the amount of traffic you can have on a single broadcast
segment by reducing the amount of, well, broadcast traffic.  People use
them a _lot_ in their server rooms, and for aggregating large numbers of
hubs together (a typical topology has a switch in the middle with hubs
hanging off it and machines hanging off the hubs).

I think that hits most of the points.  Questions?

Christopher Twigg
cdtwigg at u.washington.edu

On Mon, 24 Jul 2000, F. Pascual wrote:

> What is the difference between a hub and a switch, or are they the same thing?  When would you use one over the other?
> 
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