Here's something that most of us probably haven't thought about in years.
Some Ethernet basics...
We all know that when deploying a hub, even though the physical topology may be a hub and spoke (just like a switch), the logical topology is still a bus. Therefore, end stations must run in half-duplex mode to be able to leverage CSMA/CD - you know, listen and send if all clear. If not, start a randomized backoff timer and resend when timer expires.
What I have never seen explained is what it is about a hub that presents a bus topology? If coaxial cable is deployed, it is easy to visualize the fact that it leads to a bus topology and that collsions will occur because there is one wire upon which each station receives data from others and sends data to others. But if UTP cable is deployed (Cat 5, etc), there are separate Rx and Tx pairs, so what is it about the hub that creates a bus topology?
Note, a hub does indeed use flooding, but so does a switch sometimes (unknown unicast, for example), yet even when a switch floods, there is still a hub and spoke topology - physically, of course, and logically - hence, no collisions.
Thoughts?
Thank you
