by Drew Dunn
Home networking is a booming
business these days, driven by the very low cost of almost
anything relating to computers. You can head down to your local
computer store and buy a box with everything that you need to
set up your own local area network (LAN) and share files and
play games to your heart's content.
There are plenty of choices to
be made, and one of the most confusing is whether to use a
switch or a hub to connect your computers.
A little background will
probably help. In the old days of computer networking, there
used to be very few choices for connecting computers. You could
use coaxial cable, also called "ThinNet". All of the
computers connected in a line, one computer to the next, sort of
like a long cable with computers attached to it. Network
architects called this sort of thing a bus topology.
Another choice was to connect
the computers together using twisted pair cables, almost like
telephone wire, with a central hub or concentrator, to connect
everything together. This kind of assembly was called a star
topology, or sometimes "hub and spoke".
There were also variations on
the two themes that combined both bus and star topologies,
sometimes with dizzying levels of confusion.
Each method had its strengths
and weaknesses, trading price for performance and vice versa.
Ultimately, the star topology won out because it became the
lowest cost, high performance method on the market. It's what we
The early concentrators were
all hubs. A hub is a fairly simple device that effectively
connects all of the ports together, adds some logic for
detecting errors and moves data in from one system and out to
every other system. They're cheap and a virtual no-brainer to
configure. But they aren't the best of performers because a hub
can't establish a direct connection from one computer to
another. When a data packet is transmitted from one computer, it
actually goes to all of the computers, although only the
destination computer receives the data. When large numbers of
data packets are moved, the network slows down because in the
process of moving data from one computer to another, every
computer sees it, tying up bandwidth. Also, if two packets enter
the network at the same time, the packets collide with each
other, which means that they must be retransmitted, wasting more
As time passed, smarter hubs
entered the networking scene. These were called switches because
they were capable of actually switching data from one port
directly to another. That meant faster network performance and
fewer errors. Packets could be sent directly from one computer
to another without wasting the bandwidth of the entire network
attached to that switch.
The switch accomplishes its
task by using a little bit of intelligence. Many switches on the
market today actually hold an entire packet in a buffer, then
"look" inside the packet for its destination address,
then route the packet directly to the destination. That saves
precious network bandwidth, since only two computers are
involved with the data exchange, instead of all of them. And
once the packet is exchanged, the switch "knows" how
to route future packets to their destinations, since it has now
associated an IP address to a MAC (Media Access Control)
address, a unique identifier to each network card.
Switches also tend to reduce
network collisions by monitoring the network as specified by
IEEE 802.3. Without delving into technological gobbledygook, the
switch examines the network lines and holds any packets that
would result in a collision until the lines are clear. That
specification also allows switches to detect packets with errors
and direct the computer to resend them.
Most switches are capable of
full duplex. Many times this is advertised as something like
"200Mb/s bandwidth", but that's just marketing spin.
Full duplex means that data can simultaneously travel to and
from a system on the network. No matter what the box says, the
fastest you can go on a 100Mb network is 100Mb each way. Of
course, your network card must also support full duplex
So, this probably makes
switches look like a very tasty option in your network. And
you're right. Four or five port switches are in the US$100.00
range, with similar hubs going for less than half of that. But
as nice as switches seem, there is still a market for hubs.
If you only have two or three
computers on your network, a switch may be overkill, unless
you're transferring a lot of data between all three systems.
You'll probably find that you just don't move enough data to
generate any packet collisions.
On the other hand, if you've
got four or more systems, you'll probably want to take a close
look at a switch. Data transfers and online games can quickly
clog up your network if you're using all of the computers at
once. While you won't be able to increase your bandwidth, a
switch will more effectively use what you have. Also, if you
have just a couple of computers now, but you're going to expand
in the future, get a switch so that you'll be ready.
Other situations may call for
combinations of switches and hubs. When switches were new and
very expensive, they were usually used to connect different hubs
together to form larger networks of hubs. Although traffic could
potentially become bogged down within a particular hub's
network, that slowdown wouldn't affect systems outside of the
In a home network, you
probably won't come across that sort of situation, but if you've
got more than one hub in your network, you may want to consider
connecting the hubs to a switch instead of to each other.
The bottom line comes down to
the number of computers in your network and the size of your
wallet. Even though hubs are very cheap, switches aren't too
much more expensive. If you've got more than a few computers to
network and your wallet isn't too thin, it's probably worth your
while to consider a switch.