[AccessD] OT: Hubs attached to Routers

My understanding of things network is minimal although I do understand
Electronics.  However...

My understanding of a Router is that it is a cross point switch matrix.  It
literally connects one input to one output.  Thus traffic between two jacks
is not imposing on any other jacks (physical connectors), i.e. port 1 can
talk with port 2 (or any other port) at 100 mbps, at the same instant in
time that port 3 is talking to port 4 at 100 mbps.  There is no traffic
collisions since there is no connection between the circuits supporting the
two conversations.  IOW any port can hold a private conversation with any
other port.  Since this is the case, any remaining port can hold another
separate conversation with any remaining port.  Etc. Etc. until all ports
are busy.  It appears then that a 4 port router can create two separate
private conversations, an 8 port router can create 4 separate circuits etc.

How it does this I never understood, but that was the way it was explained
to me.

A Hub on the other hand simply connects all of the ports together all of the
time.  Therefore while Port 1 is talking to Port 2, no other ports can talk
without traffic collisions.

Before I go on, I need to ask if this is truly the case?

I would also appreciate a simple explanation of how the router knows that
data coming in on port 1 is "going to" the machine on port X.  I have to
assume that (using TCP/IP) each machine has a 192.168.x.x address (or
something similar) and that address is part of the packet.  The router knows
which machine is associated with each of those addresses, and therefore
simply closes a switch to "route" the packet to the right place?

Next, what happens when I connect a hub to port 1 (for example)?

My understanding is that all machines on the hub can only talk to one
machine at a time, but that if you take that into account, any machine on
the hub could still talk to port 2, while port 3 was talking to port 4.

My question really is, am I slowing down the network for ALL other devices
on the router?  My understanding is no.  However all machines on the HUB
share a connection to the router.  Kind of like a party line (in telephone
terminology).  The hub is a party line, the router is a private line?



John W. Colby
Colby Consulting
www.ColbyConsulting.com