What is Networking Hardware?
Networking hardware includes all
computers, peripherals, interface cards and
other equipment needed to perform
data-processing and communications within the
network. CLICK on the terms below to learn more
about those pieces of networking hardware.
This section provides
information on the following components:
File Servers
A file server stands at the
heart of most networks. It is a very fast
computer with a large amount of
RAM and storage
space, along with a fast network interface card.
The network operating system software resides on
this computer, along with any software
applications and data files that need to be
shared.
The file server controls the
communication of information between the nodes
on a network. For example, it may be asked to
send a word processor program to one
workstation, receive a database file from
another workstation, and store an e-mail message
during the same time period. This requires a
computer that can store a lot of information and
share it very quickly. File servers should have
at least the following characteristics:
- 800 megahertz or faster
microprocessor (Pentium 3 or 4, G4 or
G5)
- A fast hard drive with at least 120
gigabytes of storage
- A RAID (Redundant Array of
Inexpensive Disks) to preserve data
after a disk casualty
- A tape back-up unit (i.e. DAT, JAZ,
Zip, or CD-RW drive)
- Numerous expansion slots
- Fast network interface card
- At least of 512 MB of RAM
Workstations
All of the user computers
connected to a network are called workstations.
A typical workstation is a computer that is
configured with a network interface card,
networking software, and the appropriate cables.
Workstations do not necessarily need floppy disk
drives because files can be saved on the file
server. Almost any computer can serve as a
network workstation.
Network Interface Cards
The network interface card (NIC)
provides the physical connection between the
network and the computer workstation. Most NICs
are internal, with the card fitting into an
expansion slot inside the computer. Some
computers, such as Mac Classics, use external
boxes which are attached to a serial port or a
SCSI port. Laptop computers can now be purchased
with a network interface card built-in or with
network cards that slip into a
PCMCIA slot.
Network interface cards are a
major factor in determining the speed and
performance of a network. It is a good idea to
use the fastest network card available for the
type of workstation you are using.
The three most common network
interface connections are Ethernet cards,
LocalTalk connectors, and Token Ring cards.
According to a International Data Corporation
study, Ethernet is the most popular, followed by
Token Ring and LocalTalk (Sant'Angelo, R.
(1995). NetWare Unleashed, Indianapolis,
IN: Sams Publishing).
Ethernet Cards
Ethernet cards are usually
purchased separately from a computer, although
many computers (such as the Macintosh) now
include an option for a pre-installed Ethernet
card. Ethernet cards contain connections for
either coaxial or twisted pair cables (or both)
(See fig. 1). If it is designed for coaxial
cable, the connection will be BNC. If it is
designed for twisted pair, it will have a RJ-45
connection. Some Ethernet cards also contain an
AUI connector.
This can be used to attach coaxial, twisted
pair, or fiber optics cable to an Ethernet card.
When this method is used there is always an
external transceiver attached to the
workstation. (See the
Cabling
section for more information on connectors.)
Fig. 1. Ethernet card.
From top to bottom:
RJ-45, AUI, and BNC connectors
LocalTalk Connectors
LocalTalk is Apple's built-in
solution for networking Macintosh computers. It
utilizes a special adapter box and a cable that
plugs into the printer port of a Macintosh (See
fig. 2). A major disadvantage of LocalTalk is
that it is slow in comparison to Ethernet. Most
Ethernet connections operate at 10 Mbps
(Megabits per second). In contrast, LocalTalk
operates at only 230 Kbps (or .23 Mbps).
Fig.2. LocalTalk connectors
| Ethernet
Cards vs. LocalTalk
Connections |
| Ethernet
|
LocalTalk
|
| Fast data
transfer (10 to 100 Mbps)
|
Slow data
transfer (.23 Mbps) |
| Expensive -
purchased separately |
Built into
Macintosh computers |
| Requires
computer slot |
No computer
slot necessary |
| Available
for most computers |
Works only
on Macintosh computers
|
|
Token Ring Cards
Token Ring network cards look
similar to Ethernet cards. One visible
difference is the type of connector on the back
end of the card. Token Ring cards generally have
a nine pin DIN type connector to attach the card
to the network cable.
Switch
A concentrator is a device that
provides a central connection point for cables
from workstations, servers, and peripherals. In
a star topology, twisted-pair wire is run from
each workstation to a central switch/hub. Most
switches are active, that is they electrically
amplify the signal as it moves from one device
to another. Switches no longer broadcast network
packets as hubs did in the past, they memorize
addressing of computers and send the information
to the correct location directly. Switches are:
- Usually configured with 8, 12, or 24
RJ-45 ports
- Often used in a star or star-wired
ring topology
- Sold with specialized software for
port management
- Also called hubs
- Usually installed in a standardized
metal rack that also may store
netmodems,
bridges, or
routers
Repeaters
Since a signal loses strength as
it passes along a cable, it is often necessary
to boost the signal with a device called a
repeater. The repeater electrically amplifies
the signal it receives and rebroadcasts it.
Repeaters can be separate devices or they can be
incorporated into a concentrator. They are used
when the total length of your network cable
exceeds the standards set for the type of cable
being used.
A good example of the use of
repeaters would be in a local area network using
a star topology with unshielded twisted-pair
cabling. The length limit for unshielded
twisted-pair cable is 100 meters. The most
common configuration is for each workstation to
be connected by twisted-pair cable to a
multi-port active concentrator. The concentrator
amplifies all the signals that pass through it
allowing for the total length of cable on the
network to exceed the 100 meter limit.
Bridges
A bridge is a device that allows
you to segment a large network into two smaller,
more efficient networks. If you are adding to an
older wiring scheme and want the new network to
be up-to-date, a bridge can connect the two.
A bridge monitors the
information traffic on both sides of the network
so that it can pass packets of information to
the correct location. Most bridges can "listen"
to the network and automatically figure out the
address of each computer on both sides of the
bridge. The bridge can inspect each message and,
if necessary, broadcast it on the other side of
the network.
The bridge manages the traffic
to maintain optimum performance on both sides of
the network. You might say that the bridge is
like a traffic cop at a busy intersection during
rush hour. It keeps information flowing on both
sides of the network, but it does not allow
unnecessary traffic through. Bridges can be used
to connect different types of cabling, or
physical topologies. They must, however, be
used between networks with the same
protocol.
Routers
A router translates information
from one network to another; it is similar to a
superintelligent bridge. Routers select the best
path to route a message, based on the
destination address and origin. The router can
direct traffic to prevent head-on collisions,
and is smart enough to know when to direct
traffic along back roads and shortcuts.
While bridges know the addresses
of all computers on each side of the network,
routers know the addresses of computers,
bridges, and other routers on the network.
Routers can even "listen" to the entire network
to determine which sections are busiest -- they
can then redirect data around those sections
until they clear up.
If you have a school LAN that
you want to connect to the
Internet, you will need to purchase a
router. In this case, the router serves as the
translator between the information on your LAN
and the Internet. It also determines the best
route to send the data over the Internet.
Routers can:
