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:
- 166 megahertz or faster microprocessor (Pentium,
PowerPC)
- A fast hard drive with at least nine 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 32 MB of RAM
Workstations
All of the computers connected to the file
server on 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 or hard 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).
1- 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
2- 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 |
|
3- 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:
I.T.
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