copyright © 2009 pearson education, inc. publishing as prentice hall 1 managing information...

Copyright © 2009 Pearson Education, Inc. Publishing as Prentice Hall 1

Managing Information Technology

CHAPTER 4

TELECOMMUNICATIONS AND NETWORKING


Building Blocks of Information Technology

Hardware Software Network Data


Overview of Telecommunications and Networking

• The electronic linking of geographically dispersed devices required to accomplish telecommunications

Networking

• Communication at a distance. Also synonymous with data communications, datacom, teleprocessing, telecom, and sometimes networking.

Telecommunications


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

“ The short answer is that networks will change everything"

- Paul Saffo


Reasons for Networking

• Five primary reasons for networking1. 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


Reasons for Networking

• Five primary reasons for networking1. 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


Reasons for Networking• Five primary reasons for networking

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

• A signal in which some physical property continuously varies across time

Analog Signals

• A signal that is not a continuous function of time, but rather a series of discrete values that represent ones and zeros

Digital Signals



• Representation of digital and analog signals

Figure 4.2



• 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

• The difference between the highest and lowest frequencies that can be transmitted on a single medium; a measurement of capacity

Bandwidth

• Cycles per second

Hertz

• Signals per second

Baud


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

• Data can only travel in one direction

Simplex

• Data can travel in both directions, but not simultaneously

Half-duplex

• Data can travel in both directions at once

Full-duplex


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


Transmission Media

• Wireless– Wireless LANs

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


Transmission Media

• Wireless– 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


Transmission Media

• Wireless– Satellite

• Geostationary Earth Orbit (GEO)– Remains stationary relative to earth– Inmarsat service of 11 GEO

satellites

• Low Earth Orbit (LEO)

Figure 4.4


Transmission Media• Wireless

– 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


Transmission Media

• Wireless– 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


Transmission Media

• Wireless– 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


Transmission Media

• Wireless– 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

• Simple devices that forwards all messages to every device attached to it

Hub

• Central device that connects wireless LAN to other networks

Wireless Access Point

• Connects two LAN segments and only forwards messages that need to go to other segment

Bridge

• A multiport bridge; connects two or more LAN segments

Switch

• Connects two ore more LANs and only forwards messages that go to the other LAN

Router


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 Types

2. 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


Network Types

2. Local Area Networks (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 collisions

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


Network Types2. Local Area Networks (LANs)

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)

• A token bus protocol that was developed by General Motors for factory automation

Manufacturing Automation Protocol


Network Types

2. Local Area Networks (LANs)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)


Network Types

2. Local Area Networks (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)

• 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

• LANs1. 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 Networks3. Backbone Networks

• Connect LANs• Key to internetworking

Figure 4.10


Network Types

4. 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


Network Types

4. Wide Area Networks (WANs)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


Network Types4. Wide Area Networks (WANs)

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


Network Types4. Wide Area Networks (WANs)

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 network Figure 4.11• Advantages• Efficient use of network• Can be high capacity

• Disadvantages• Packets may arrive in

different order or with delay


Network Types

5. 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 Types

6. 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

copyright © 2009 pearson education, inc. publishing as prentice hall 1 managing information...

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