Re: [SLUG] Hub, Switch, & Router

From: Paul M Foster (paulf@quillandmouse.com)
Date: Wed Jan 12 2005 - 22:10:43 EST


On Wed, Jan 12, 2005 at 08:07:20PM -0500, SOTL wrote:

> Hi All
>
> Laying on the couch thinking about this I believe that the following is
> correct:
>
> Lets assume a device with one what we shall call a line connection and 5
> output connection. This device will be a:
>

I'm going to stick my foot in my mouth and showcase my ignorance. Others
may correct me as needed.

> Hub
> Non configurable
> If all packages into any one port go to all other ports.

A hub is just a device that connects other devices. Used to be, with
10Base2 (coax) networking, wiring would go to each device in a sort of
ring. There was really no central point to which all the devices were
connected. Which meant that if you cut or disconnected a cable in one of
these networks, the whole network would go down.

With 10BaseT (and 100BaseT-- cat 5 cabling), computers are connected in
a "star" arrangement to a central point. Each computer has a line that
runs to the central point. At that central point sits a "hub". It serves
to connect everything together. That's all it does. It's sort of like a
power strip into which you plug everything. It has nothing to do with
routing the way we've been talking about it.

>
> Switch
> Non configurable
> If an input package only goes to the port that contains the device that the
> package is directed to. Can not figure this one out how the switch knows to
> sent a package inputed to A to output B instead of C and what happens if you
> need it to also go to D?
>

A switch is just like a router, with this exception: a hub can only
listen to one device at a time. So if computer A is talking, the hub
won't listen to computer B. A switch, on the other hand, can listen to
all other devices at once. Switches used to be much more expensive, but
they are replacing hubs these days. (I'm sure there is more to it than
this, but practically speaking, this is my understanding of the real
differences.)

> Router
> If you configure the device such that that a package in A go to which ever
> combination of ports you choose for outputs. By this one could configure all
> e-mail to go to ports A & B AFN to no other port, all html to port C and
> reject all other packages. You can configure this as you want.

(Frank, these are "packets", not "packages". Very confusing when you
refer to them with the wrong terminology. Since everything that goes on
a network wire is digital (as opposed to analog), and since routing and
such are a big part of network traffic, the bits on the wire are
"packaged" into "packets" of a certain number of bits in a certain
arrangement. There is a "payload" in each packet that's the actual
important data it carries. Around this payload is arranged a variety of
other groups of bits that indicate who originated the communication, to
where it's supposed to go, and a variety of other bits of information.
Altogether, the group of bits is a "packet".)

What you're talking about here is something a router can do, but is
really more like a firewall function.

A bridge is really something that is designed to connect two physical
pieces of a network. It tends to isolate "noise" that increases as
network size increases. It acts as a conduit into network part A from
network part B, and vice versa. The computers in network part A don't
have to listen to all the garbage from the computers in network part B,
and vice versa.

A router pretty much covers everything else. It routes data packets
according to whatever rules you've set up.

To get beyond this level, you'd have to study the OSI network model, the
various layers, etc. etc.

Paul
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