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

This section provides information on the following components:

1. File Servers
2. Workstations
3. Network Interface Cards
4. Switches
5. Repeaters
6. Bridges
7. Routers

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.)


1. Ethernet card.

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)

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. Inthis 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:

* Direct signal traffic efficiently
* Route messages between any two protocols
* Route messages between linear bus, star, and star-wired ring topologies
* Route messages across fiber optic, coaxial, and twisted-pair cabling