topic 2- network computing

MBA program, Open University Malaysia, Information Technology for Managers, Lecturer: Dr. Pham Van Tai 1

Managing Information Technology6th Edition

TELECOMMUNICATIONS AND NETWORKING


IT Building Blocks


Overview of Telecommunications and Networking


The Telecommunications Industry Three major segments

Carriers who sell the service of communication transmission

Equipment vendors who manufacture and sell telecommunications hardware and software

Service Providers who provide access to or services via the Internet


Telecommunications Industry AT&T

Largest corporation in industry In 1984, AT&T split into several companies as a result

of a US Department of Justice antitrust lawsuit Breakup of AT&T has led to innovation through

competition Recent trend towards consolidation in the industry



Telecommunications and networking are becoming increasingly important to businesses because of decentralization and globalization


Reasons for Networking Five primary reasons for networking

1. Sharing of technology resources Prior to networking capabilities, computers could not even

share printers!!2. Sharing of data

Enables virtual teams who can share data Allows efficient transactions between businesses, their

suppliers, their and customers Some businesses share many terabytes of data per day

3. Distributed data processing and client/server systems4. Enhanced communications5. Marketing outreach



1. Sharing of technology resources2. Sharing of data3. Distributed data processing and client/server systems

Distributed data processing Information processing that uses multiple computers at multiple sites

that are tied together through telecommunication lines Client/Server Systems

A type of distributed systems in which the processing power is distributed between a central server and a number of client computers

4. Enhanced communications5. Marketing outreach

Client ServerTransfer of Data



1. Sharing of technology resources2. Sharing of data3. Distributed data processing and client/server systems4. Enhanced communications

Telecommunication networks provide the ability to communication through Email, Bulletin Boards, Blogs, Instant Messaging, Wikis, and Videoconferencing

Links between organizations can lead to strategic advantages in terms of business transactions

SABRE airline reservation system EDI

5. Marketing outreach Businesses may share data with consumers to advertise or sell their

products through a corporate web presence



A telecommunications network is more than a series of wires or radio waves

Functions of a Telecommunications Network

Table 4.1


Analog and Digital Signals


Analog and Digital Signals Representation of digital and analog signals

Figure 4.2


Analog and Digital Signals Digital computer data does not naturally mesh

with analog transmission; it must be converted from ones and zeros to analog signals

Solutions Modem (Modulator/Demodulator)

Digital networks Advantages of lower error rates and higher speeds

Figure 4.1


Transmission Speed Transmission speeds can be measured in

several ways


Telecommunication Lines Types of Transmission Lines

Private (dedicated) Advantages

Ensures quality of transmission Disadvantages

Costly Switched

Advantages Less costly

Disadvantages Message may take many different routes Quality of transmission may degrade


Telecommunication Lines Types of Transmission Lines


Transmission Media Twisted Pair

Literally wires that are twisted to reduce interference

Can be shielded (STP) or unshielded (UTP), but the most commonly used is UTP

Commonly used in telephones and LANs


Transmission Media Coaxial (Coax) Cable

Baseband Inexpensive, designed for digital transmission

Broadband Originally for analog, now used for digital Commonly used in television cable

Figure 4.3


Transmission Media Wireless

Not strictly a transmission media, but rather a technology in which radio signals are sent through the air

There are many different wireless technologies such as cordless telephones and cellular telephones which are widely used in personal and business communications

We will consider the following wireless technologies in more detail: Wireless LANs Microwave

Line of sight Satellite

Long distances Line of sight

RFID Bluetooth



Wireless LANs Growing in popularity Useful when wiring is not possible Slower than some wired solutions Allow mobile devices to connect to network



Microwave Widespread use for several decades Line of sight transmission Limited to 25-50 mile distances because of curvature of

the earth Expensive, but less costly than fiber optic cables



Satellite Geostationary Earth Orbit (GEO)

Remains stationary relative to earth

Inmarsat service of 11 GEO satellites

Low Earth Orbit (LEO)

Figure 4.4



Satellite Geostationary Earth Orbit (GEO) Low Earth Orbit (LEO)

Iridium First major LEO project with 66 satellites Faced high operating costs and which

resulted in a bankruptcy Mostly military subscribers Tell us more about these 3

Globalstar LEO project with 40 satellites that does not

provide global coverage Teledesic

Ambitious project with original plans to launch 840 satellites

This was later cut to 288 satellites, then 30, and then the program was cancelled

Figure 4.4



RFID Acronym for Radio Frequency Identification An old technology that became popular in business

when Wal-Mart required the use of RFID by some of its suppliers to improve inventory and supply chain management



RFID Two Broad Types of RFID

Active these tags have their own power supply and can transmit messages continuously, on request, or on a schedule

Cost over $1.00 Passive these tags only send a response the RFID reader

sends a small radio signal which induces a current Cost in the $0.08 - $0.20 range

Many analysts believe that passive tags must cost only $0.05 for RFID to be widely adopted



Bluetooth Named after Danish King who united Denmark

The technology is intended to unify telecom and computing Short-range wireless technology Designed to consume very little electrical power and be

produced at a low cost Found in a growing number of devices such as cell phones,

laptops, headsets, keyboards, mice, and home appliances Over 318 million devices in 2005 used Bluetooth for

communication between devices


Transmission Media Fiber Optics

Thin fiber of glass Faster, lighter, and more secure than other media Large diameter fiber is multimode (multiple light

rays at the same time) while smaller diameter is single mode

Smaller diameter fiber has larger capacity due to less light bounces


Individual Network Access Internet Service Providers (ISPs) sell access to the Internet Early, the only way to access the Internet was through a dial-in modem

connection Consumers now have more options including faster broadband

connections Digital Subscriber Line (DSL) is a connection through a telephone company Cable modem is a connection through a cable television company Satellite

With one-way service, individuals must obtain uplink service from another provider Wireless access may be through a municipal carrier or a private company

There are several pricing methods for personal Internet access Fixed price (usually monthly)

Hotels and airports often offer Internet access for a shorter period (e.g., 24 hours) Cost based on usage (data transferred) Free to consumers, but supported by taxes or advertising


Network Topology Network topology refers to the configuration or

arrangement of the devicesFigure 4.5 Bus

All devices are attached to one cable Single-point failure

Ring Similar to bus, but ends are attached Not susceptible to single-point failure

Star All nodes are attached to central device Susceptible to failure of central device, but easy to

identify cable failure Tree

Similar to the star, but with a hierarchical structure Mesh

Devices are to multiple other devices A failure has little impact on the network Costly


Networking Devices Devices used to implement network topologies


Network Types There are several types of networks We will consider six types

1. Computer Telecommunications Networks2. Local Area Networks (LANs)3. Backbone Networks4. Wide Area Networks (WANs)5. The Internet6. Internet2


Network Types1. Computer Telecommunications Networks

This was the only type of network until the 1980s

Commonly used in mainframe architectures

Figure 4.7


Network Types2. Local Area Networks (LANs)

Standards developed by the Institute for Electrical and Electronic Engineering (IEEE)

IEEE 802 is a family of standards for LANs and metropolitan area networks

Five types of LANs in common use today1.Contention Bus (IEEE 802.3)2.Token Bus (IEEE 802.4)3.Token Ring (IEEE 802.5)4.Wi-Fi (IEEE 802.11)5.WiMAX (802.16e)

We will discuss each of the five types of LANs



1. Contention Bus (IEEE 802.3) Developed by Xerox Usually called Ethernet after the original Xerox version Half-duplex All devices must contend to use

CSMA/CD protocol for collisions2. Token Bus (IEEE 802.4)3. Token Ring (IEEE 802.5)4. Wi-Fi (IEEE 802.11)5. WiMAX (802.16e)



1. Contention Bus (IEEE 802.3)2. Token Bus (IEEE 802.4)

A token (special message) is passed among devices Only the device with the token can transmit a message Important for Manufacturing Automation Protocol (MAP)

3. Token Ring (IEEE 802.5)4. Wi-Fi (IEEE 802.11)5. WiMAX (802.16e)



1. Contention Bus (IEEE 802.3)2. Token Bus (IEEE 802.4)3. Token Ring (IEEE 802.5)

Developed by IBM Combination of ring topology with use of tokens (used

the same way as in token bus)4. Wi-Fi (IEEE 802.11)5. WiMAX (802.16e)



1. Contention Bus (IEEE 802.3)2. Token Bus (IEEE 802.4)3. Token Ring (IEEE 802.5)4. Wi-Fi (IEEE 802.11)

Short for Wireless Fidelity Most common wireless LAN type Uses a shared Ethernet design Use CSMA/CA Protocol

Similar to CSMA/CD, but with less collisions Commonly used in offices to supplement wired Ethernet networks

or in areas where adding wiring is problematic Many cities are offering Wi-Fi networks

5. WiMAX (802.16e)


Network Types LANs

1. Contention Bus (IEEE 802.3)2. Token Bus (IEEE 802.4)3. Token Ring (IEEE 802.5)4. Wi-Fi (IEEE 802.11)5. WiMAX (802.16e)

Newest of the network types Similar to Wi-Fi, but operates over longer distances and at

higher speeds Can use both licensed and non-licensed frequencies Sprint Nextel are planning to offer their Xohm WiMAX

service across the US in the 2.5GHz radio spectrum In November 2007, Sprint Nextel abandoned talks of a joint

venture with Clearwire, a WiMAX provider


Network Types Local Area Networks (LANs)

Problems with wireless networks (WiFi and WiMAX)

More difficult to secure that other network types Organizations that offer wireless access to entice

customers have problems with noncustomers or unprofitable customers overusing the network

Unauthorized wireless use is also problematic in condos and apartments


Network Types Types of Networks

3. Backbone Networks Connect LANs Key to internetworking

Figure 4.10


Network Types4. Wide Area Networks (WANs)

Similar to LANs, but cover greater distances We will consider the following three general types

of WANs because they each have advantages and disadvantages

1. Switched Circuit2. Dedicated Circuit3. Packet-switched



1. Switched Circuit (or circuit-switched) A single physical path is temporarily created between two nodes

for their exclusive communication There are most widely available means of implementing a WAN

using a switched circuit connection is to use the ordinary telephone network

Advantages Easy to set up

Disadvantages Low speed High error rates

There are two different pricing schemes available for this service Direct Distance Dialing (DDD) - pay for usage Wide Area Telephone Service (WATS) - fixed rate



2. Dedicated Circuit These are permanent channels

exclusive to the business Advantages

High capacity Low error rates

Disadvantages Expensive

There are two different types of dedicated circuits Leased lines are cable, microwave, or

fiber connections Satellite circuits are popular for

organizations with many global locations

Table 4.3



3. Packet-switched Multiple connections exist simultaneously over the same physical

circuit Messages are broken up into packets Businesses use PADs (Packet assembly/disassembly devices) to

connect their networks to a common carrier networkFigure 4.11Advantages

Efficient use of networkCan be high capacity

DisadvantagesPackets may arrive in different order or with delay


Network Types5. The Internet

Network of networks that use the TCP/IP protocol Similar to an enormous WAN 433 million hosts as of January 2007 Roots in ARPANET and NSFNET

ARPANET (Advanced Research Projects Agency Network) was created by the US Department of Defense

NSFNET (National Science Foundation Network) was created to link supercomputers for research

Each of these were wide scale, packet-switching networks that lead to the creation of the Internet


Network Types5. The Internet

Internet Applications


Network Types6. Internet2

Not-for-profit consortium made up of over 200 universities as well as industry and government partners that develops and deploys advanced network applications and technologies for research and commercial purposes

Goals Create a leading-edge network capability for the national

research community Enable revolutionary Internet applications based on a much

higher-performance Internet than we have today Ensure the rapid transfer of new network services and

applications to the broader Internet community


Networking Protocols Network Protocols

An agreed-upon set of rules or conventions governing communication among elements of a network

Open Systems Interconnection (OSI) Reference Model

Skeleton for standards Movement toward this model

stopped with the growth of the Internet

Figure 4.13


Networking Protocols OSI Model

Developed by the International Organization for Standardization (ISO)to outline a standard set of protocols for telecommunications

Figure 4.14


Networking Protocols Transmission Control Protocol/Internet Protocol

(TCP/IP) Created to link different types of networks (e.g.,

satellite and ground packet networks) together into a network of networks

Has become de facto standard protocol for networking

TCP is responsible for the reliable and ordered transmission of messages

IP is responsible for routing individual packets based on their individual addresses (IP addresses)

Roughly corresponds to network and transport layers of OSI model


Networking Crucial to Organizations Networking and Telecommunications have

become necessary for businesses to function Problems with undersea Internet cables cut in

Middle East

topic 2- network computing

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