Introduction
Given
the low cost of computers in today's market and their increasing popularity,
it is not uncommon for users to have multiple systems in the home. This has
given rise to many home networking setups. Until recently, most people have
simply been using 10 or 100 Base hubs to tie the network together. However,
switches are quickly becoming very affordable and offer a reliable and more
efficient means of data transfer. Today, we take a look at the Compex PS2208A
Pocket Switch, an 8-port full-duplex 10/100 switch that can be had for a mere
$49.
For those of you who are not already aware of the differences
between a switch and a hub, I will offer a quick explanation. Hubs operate
on Layer-1 of the OSI model. They are "dumb" devices and can be compared to
a simple splitter. When data is sent from one computer to the port of a hub,
it is rebroadcast to all ports. The header is not stripped, no data is changed,
it simply sends the signal to all of the ports. It is really just a multi-port
repeater. If Computer-A transfers a file to Computer-D, it also sends the
signal to Computers B&C. Those computers read the signal, see that the data
is not intended for them, and ignore the following transfer. This constant
bombarding of information occasionally causes collisions. A collision occurs
when two packets crash into each other during transmission. Collisions are
a part of ethernet networks and are a normal occurrence. However, it makes
the network inefficient because both of the colliding packets are destroyed
and must be retransmitted.
A switch operates at Layer-2 of the OSI model. They are "smart"
devices and actually process the data coming in. When a switch is first powered
on, it will send a request to all of the connected computers and read the
MAC address of each network card. It writes this information to memory along
with which port each of the MAC addresses is assigned to. The MAC address
is a unique hexadecimal number which is hardcoded into every NIC that is produced.
When information is sent from one computer to another, the switch only sends
it to computer that is intended. This makes the switch virtually collision
free and is often referred to as "non-blocking". In turn, it provides a much
more efficient network than a hub. :)
Features
