MODULE 1: BASIC NETWORKING CONCEPTS

Unit 3: Networking hardware

Page

1.0 Introduction 1

2.0 Objectives 2

3.0 Networking hardware 3

4.0 Conclusion 4

5.0 Summary 5

6.0 Tutor Marked Assignment 6

7.0 Further Readings 7

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1.0 INTRODUCTION

This unit describes the various components of networking hardware.

2.0 OBJECTIVES

At the end of this unit you should able to :

• Recognize and explain the individual components of the big picture of computer
networks
• Outline the basic network configuration

3.0 NETWORKING HARDWARE

Networking hardware includes all computers, peripherals, interface cards and other
equipment needed to perform data-processing and communications within the network.

Fig. 1.3.1 Networking Hardware

Source : Florida Center for Instructional Technology College of Education, University of

South Florida ©1997-2005.

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This section provides information on the following components:

• File Servers
• Workstations
• Network Interface Cards
• Switches
• Repeaters
• Bridges
• 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 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

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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.

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. 1.3.2).
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.

Fig. 1.3.2 Ethernet card.(From top to bottom: RJ-45, AUI, and BNC connectors )

Source: http://blue.utb.edu/libertad/clipart/pi_wireless_pc_card_b.jpg

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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. 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 us ed 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 net-modem,
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

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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 super-

intelligent 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. Routers can:

• Direct signal traffic efficiently

• Route messages between any two protocols
• Route messages between linear bus, star, star-wired ring topologies
• Route messages across fiber optic, coaxial and twisted-pair cabling

Exercise 1.3.1 Describe circuit switching.

Answer: Circuit switching entails a dedicated (non-shared) path between a sender

and a receiver. Circuit switching requires circuit establishment, data transfer, and
disconnect.

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Exercise 1.3.2 In the context of circuit switching, what is “blocking”?

Answer: A blocking switching may deny connections due to resource limitation.

That is, two idle connected stations may not be able to communicate due to lack of
resources in a switch caused by other connections.

4.0 CONCLUSION

Networking hardware includes all computers, peripherals, interface cards and other
equipment needed to perform data-processing and communications within the network.

5.0 SUMMARY
This unit provides information on the following networking components:
• File Servers
• Workstations
• Network Interface Cards
• Switches
• Repeaters
• Bridges
• Routers

6.0 TUTOR MARKED ASSIGNMENT

1. What are the major components of networking hardware?
2. Briefly discuss the following hardware components:
• File Servers
• Workstations
• Network Interface Cards
• Switches
• Repeaters
• Bridges
• Routers

7.0 FURTHER READINGS

1. Communication Networks: A First Course, 2nd edition, Jean Walrand,

McGraw Hill, 1998.
2. Computer Networks, Andrew Tanenbaum, Prentice-Hall, 4th Edition,
2002.
3. Computer Networks: A Systems Approach, Larry Peterson & Bruce Davie,
Morgan Kaufman

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