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Appendix C
Networking
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Appendix C-1
Human Communication
Messages
Human communication involves the sharing of information
between senders and receivers. The information is shared
in the form of a message
Sender
Initiates the message
by formulating the
message content in
the brain and coding
the message in a
form that can be
communicated to the
receiver (e.g. voice)
Information Systems Today
Communication
Pathway
Appendix C-2
Receiver
Uses their receiving
mechanism (e.g.
eyes, ears) to receive
the encoded message
and then attempts to
decode its content or
requests the message
be resent
(©2006 Prentice Hall)
Human Communication Example
Information Systems Today
Appendix C-3
(©2006 Prentice Hall)
Requirements for Communication (Computer)
Senders and Receivers
There must a be a sender and a receiver with something
to share via a message to facilitate communication
Communication Medium
A medium must exist between the sender and receiver
over which the message travels (e.g., a cable)
Protocols
Procedures, rules, or standards must be followed by
computers when sending or receiving data
Information Systems Today
Appendix C-4
(©2006 Prentice Hall)
Communication (Human versus Computer)
Information Systems Today
Appendix C-5
(©2006 Prentice Hall)
Computer Networks
Centralized Computing (1970s)
The centralized computing model utilizes a central
computer (mainframe) connected to terminals with all
processing being done on the central computer
Distributed Computing (1980s)
The use of small computers networked together allowing
users to perform a subset of tasks that in aggregate are
equal to that of a centralized computer while also being
able to share information between those computers
Collaborative Computing (1990s)
A synergistic form of distributed computing in which two
or more networked computers are used to accomplish a
common processing task where they are not only sharing
data but also sharing processing responsibilities
Information Systems Today
Appendix C-6
(©2006 Prentice Hall)
Types of Computing
Distributed Computing
Centralized Computing
Collaborative Computing
Information Systems Today
Appendix C-7
(©2006 Prentice Hall)
Types of Networks
Networks
Most networks utilize a combination of computing
models that have evolved over time and are connected by
one or more of the following network types:
• Private Branch Exchange (PBX)
• Local Area Network (LAN)
• Wide Area Network (WAN)
• Global Networks
• Enterprise Network
• Value-added Network (VAN)
• Metropolitan Network (MAN)
• Personal Area Network (PAN)
Information Systems Today
Appendix C-8
(©2006 Prentice Hall)
Private Branch Exchange
PBX
A telephone system
serving a location by
connecting one
telephone line to
another then to an
outside telephone
network. Can also
connect PCs, fax,
but at low phonecable speeds
Information Systems Today
Appendix C-9
(©2006 Prentice Hall)
Network Types – Local Area Network
Local Area Network
A computer network that spans a relatively small area
allowing all computer users to connect with each other to
share information and peripheral devices (e.g., printers)
Information Systems Today
Appendix C-10
(©2006 Prentice Hall)
Types of Networks – Wide Area Networks (WAN)
Wide Area Networks (WANs)
A computer network that spans a relatively large area and
is typically used to connect two or more LANs using
different kinds of hardware and transmission media to
cover large distances efficiently
Global
A WAN that spans multiple countries and may include
the networks of several organizations (e.g. the Internet)
Value-added Network (VAN)
A medium-speed, third-party-managed network that is
economical as it is shared by multiple customer
organizations that lease lines rather than investing in
dedicated network equipment
Information Systems Today
Appendix C-11
(©2006 Prentice Hall)
Types of Networks – Wide Area Networks (WAN)
Enterprise Network & MAN
Enterprise
A WAN that is the result of
connecting the disparate
networks of a single
organization
Metropolitan Area (MAN)
A WAN network of limited
geographic scope, typically
in a city-wide area that
combines both LAN and
high-speed fiber-optic
technologies
Information Systems Today
Appendix C-12
(©2006 Prentice Hall)
Types of Networks – Personal Area Network (PAN)
Personal Area Network
An emerging technology that uses wireless
communication to exchange data between commuting
devices using short-range radio communication
(Bluetooth), typically within an area of ten meters
Bluetooth
Is the enabling technology of the Personal Area
Network and is a specification for personal networking
of desktop computers, mobile phones, pagers,
portable stereos, and other handheld devices
developed by its founders Ericsson, IBM, Intel, Nokia,
and Toshiba
Information Systems Today
Appendix C-13
(©2006 Prentice Hall)
Networking Fundamentals – Servers and Clients
Network
A network consists of three separate components: servers,
clients and peers
Server
Any computer on a
network that makes
access to files, printing,
communication, and
other services available
to users on the network
Client
Any computer, such as a user’s workstation or a PC on the
network, or software application such as word processing
program that uses services provided by the server. A client
only requests service and usually has only one user
Information Systems Today
Appendix C-14
(©2006 Prentice Hall)
Networking Fundamentals – Peers
Peer
A computer that may both request and provide services
Peer-to-Peer Networks (P2P)
Enables any computer or device on the network to provide
or request services with all peers having equivalent
capabilities and responsibilities (e.g., Napster)
Information Systems Today
Appendix C-15
(©2006 Prentice Hall)
Networking Fundamentals - Network Services
Network Services
The capabilities that networked computers share through
the multiple combinations of hardware and software
File Services (a)
The capabilities that
networked computers
share through the multiple
combinations of hardware
and software
Print Services (b)
The capabilities used to
control and manage
user’s access to network
printers, plotters, fax
equipment, etc.
Information Systems Today
Appendix C-16
(©2006 Prentice Hall)
Networking Fundamentals - Network Services
Message Services (c)
The capabilities that
include storing, accessing,
and delivering of text,
binary, graphic, digitized
video and audio data
Application Services (d)
The capabilities that run
software for network
clients and enable
computers to share
processing power
Network Operating System (NOS)
Is software that controls the network enabling computers to
communicate by enabling network services
Information Systems Today
Appendix C-17
(©2006 Prentice Hall)
Networking Fundamentals – Transmission Media
Transmission Media
The physical pathway to send data and information
between two or more entities on the network.
Characteristics of the media include the following:
Bandwidth
Is the transmission capacity of a communications
channel or computer, measured in megabits per second
(Mbps) (amount of binary data transmitted per second)
Attenuation
This results when the power of an electrical signal
weakens as it is sent over increasing distance
Electro Magnetic Interference (EMI)
Interference commonly caused by fluorescent lights,
weather, or other electronic signals that affects the
distance a signal can travel (increased attenuation)
Information Systems Today
Appendix C-18
(©2006 Prentice Hall)
Networking Fundamentals – Media (Cable)
Twisted Pair
Two or more pairs of insulated copper wires
twisted together and may be shielded (STP)
or unshielded (STP). It is the lowest
capacity of the cable options
Coaxial
Contains a solid inner copper conductor
surrounded by insulation and outer braided
copper or foil shield. It comes in UTP and
STP and is higher capacity than twisted pair
Fiber-Optic
Made of light-conducting glass or plastic
core, surrounded by more glass, called
cladding, and a tough outer sheath. It is high
capacity and used in high speed backbones
Information Systems Today
Appendix C-19
(©2006 Prentice Hall)
Networking Fundamentals – Media (Cable)
Information Systems Today
Appendix C-20
(©2006 Prentice Hall)
Networking Fundamentals – Media (Wireless)
Wireless
A communication mechanism that has no physical
transmission media, hence the name wireless, that
works by transmitting electromagnetic signals through
the air. Types of wireless media include:
• Infrared line of sight
• High-frequency radio
• Microwave methods
Infrared Line of Sight
Uses high-frequency light waves to transmit data on
an unobstructed path between nodes – computers or
some other device such as a printer – on a network up to
24.4 meters (i.e. most electronics remotes use this
infrared light) and are susceptible to attenuation, EMI,
eavesdropping, high-intensity light, and smoke
Information Systems Today
Appendix C-21
(©2006 Prentice Hall)
Networking Fundamentals – Media (Wireless)
High-Frequency Radio
A fast transmission medium for distances up to 40 kilometers,
depending on obstructions. Attenuation is very low but is
susceptible to EMI and eavesdropping. Applications of this
technology include pagers, cellular phones, and Wi-Fi
Pagers
A one way, wireless messaging system in multiple types
Information Systems Today
Appendix C-22
(©2006 Prentice Hall)
Networking Fundamentals – Media (Wireless)
Cellular Phone
A two-way wireless communication that assigns unique
frequencies to calls and can transmit in analog or digital
Information Systems Today
Appendix C-23
(©2006 Prentice Hall)
Networking Fundamentals – Media (Wireless)
Wireless LANs or
Wireless Fidelity (Wi-Fi)
Based on a standard
called 802.11, this
technology enables
multiple computers to
share Internet access,
files, and peripheral
devices
Information Systems Today
Appendix C-24
(©2006 Prentice Hall)
Networking Fundamentals – Media (Microwave)
Microwave
A high frequency radio signal that is sent through the air
using either terrestrial (earth-based) or satellite systems
Terrestrial Microwave
A line-of-site technology
(unobstructed) used to cross
inaccessible terrain or to
connect buildings where cable
installation would be
expensive. Attenuation is
low over short distance but
higher over longer distances,
and high winds, heavy rain,
EMI and eavesdropping are
also problems
Information Systems Today
Appendix C-25
(©2006 Prentice Hall)
Networking Fundamentals – Media (Microwave)
Satellite Microwave
A line-of-site technology
that uses relay stations to
transfer signals between
antennae located on earth
and a satellite orbiting
the earth. It can be used
to access the very remote
locations and like a
terrestrial microwave,
attenuation, EMI and
eavesdropping are also
problems
Information Systems Today
Appendix C-26
(©2006 Prentice Hall)
Networking Fundamentals – Media (Wireless)
Wireless Media Benefits and Drawbacks
Comparisons of Wireless Media
Information Systems Today
Appendix C-27
(©2006 Prentice Hall)
Network Hardware and Software (Media Access Control)
Media Access Control
The set of rules that govern how a given node or
workstation gains access to the network to send or
receive information.
Media Access Control Types
• Distributed Access Control – the most common method of
distributed access control is token passing. This method
uses a constantly circulating electronic token (a small packet
of data) to prevent collisions and give workstations equal
access to the network
• Random Access Control – the most common method of
random access control is called carrier sense multiple
access/collision detect (CSMA/CD). In CSMA/CDCD each
workstation listens to the network to determine whether a
message is being transmitted. If quiet, the workstation
transmits its message; otherwise it waits
Information Systems Today
Appendix C-28
(©2006 Prentice Hall)
Network Hardware and Software (Media Access Control)
Token
Distributed
Media
Access
Control
Information Systems Today
Appendix C-29
(©2006 Prentice Hall)
Network Hardware and Software (Network Topologies)
Network Topologies
Refers to the shape of a network and comes in three types:
Star Network
The network is configured in the shape of a star with all nodes
or workstations connected to a central hub, or concentrator,
through which all messages pass
Ring Network
The network is configured in the shape of a circle with each
node connecting to the next node. Messages travel around
the circle in one direction. Each node examines the message
and uses it or regenerates it and passes it to the next node
Bus Network
The network is configured in the shape of an open-ended line
with all nodes or workstations connected to the bus
individually.
Information Systems Today
Appendix C-30
(©2006 Prentice Hall)
Network Hardware and Software (Network Topologies)
Star Network
Bus Network
Ring Network
Information Systems Today
Appendix C-31
(©2006 Prentice Hall)
Network Hardware and Software (Protocols)
Protocols
Agreed-upon formats for transmitting data between
connected computers
Open Systems Interconnection (OSI)
Is a protocol that represents a group of tasks (below) as
seven successive layers that allow computers to communicate
Information Systems Today
Appendix C-32
(©2006 Prentice Hall)
Network Hardware and Software (Protocols)
Information Systems Today
Appendix C-33
(©2006 Prentice Hall)
Network Hardware and Software (Protocols)
Information Systems Today
Appendix C-34
(©2006 Prentice Hall)
Network Hardware and Software (Hardware)
Connectivity Hardware
The hardware that allows computers to be physically
connected to different types of networks
Common Connectivity Hardware
• Connectors
• Network Interface Cards (NICs)
• Modems
• Repeaters
• Hubs
• Bridges
• Multiplexers
• Routers
• Brouters
• Channel Service Units
• Gateways
Information Systems Today
Appendix C-35
(©2006 Prentice Hall)
Network Hardware and Software (Hardware)
Connectors
Used to terminate cables in order to be plugged into a
network interface card or another network component
Network Interface Card
A PC expansion board with its own unique identifier that
plugs into a computer allowing it to be connected to a
network
Information Systems Today
Appendix C-36
(©2006 Prentice Hall)
Network Hardware and Software (Hardware)
Modem (Modulator/Demodulator)
Enables computers to connect and transmit data over
phone lines by converting the sending computer’s digital
signals to analog and back again for the receiving computer
Information Systems Today
Appendix C-37
(©2006 Prentice Hall)
Network Hardware and Software (Hardware)
Repeater
A network device used to regenerate or replicate a signal
as it weakens when traveling across a network
Hubs
A central point of connection between media segments
enabling network extension to accommodate more PCs
Bridges
Used to connect two different LANs or two segments of the
same LAN by forwarding traffic between segments
Multiplexer
Used to share a communications line among a number of
users by converting and combining signals from multiple
users for simultaneous transmission over a single line
Information Systems Today
Appendix C-38
(©2006 Prentice Hall)
Network Hardware and Software (Hardware)
Router
An intelligent device used to connect two or more
individual networks. When it receives a signal, it looks up
the address and passes it to the appropriate network
Brouter
Short for bridge router and provides the functions of both
Channel Service Unit
A device that acts as a buffer between a LAN and a public
carriers WAN to ensure signals placed on the public lines
are appropriately timed and formed for the network
Gateways
This device performs a protocol conversion so that
different networks can communicate even though they
speak different languages
Information Systems Today
Appendix C-39
(©2006 Prentice Hall)