telecommunications, the internet, and wireless … · less redundancy data integrity ... data...

Lecture 18TIM 50 Autumn 2012Tuesday November 27, 2012

TELECOMMUNICATIONS, THE INTERNET,AND WIRELESS TECHNOLOGY

Announcement

1. The grades for every assignment will be given in eCommons.2. It's important to check webpage to get the latest informationand assignments changes.

Final Exam 1st Choice December 7, Friday2nd Choice December 10, Monday

Format is same as MidtermCovering Up to Midterm 25‐ %

After Midterm 75+ %

Foundation of business Intelligence

Data Base SystemInformation Management

File Management SystemFile Processing Procedure

Data Base SystemsDBMS,SQL

Intelligence from Collection of DataInformation ManagementBusiness Applications

Data Integrity ControlBusiness Data Maintenances

Division OrientedPaper File SystemsManual Processing

System InefficienciesLonger Business CycleNo Firm wise Information or Data AccessNo Data SecurityNo Decision son Integrated Data and informHigh Business Process Expenditure

Data Base SystemsRelational DBObject Oriented DBDBMS

Less RedundancyData IntegrityEfficiencyData Confidentiality

Data redundancy: Data inconsistency: Program‐data dependence:Lack of flexibilityPoor securityLack of data sharing and availability

Data Where house, martData MiningDSS, BI

Data ControlData Integrity

Review

Database – collection of persistent data frombusiness divisions

Database Management System (DBMS) –software system that supports creation,population, and querying of a database

Introduction of Data Processing System

DatabaseServes many business applications by centralizing data and controlling redundant data across division boundaries

Database management system (DBMS)Interfaces between applications and physical data filesSeparates logical and physical views of dataSolves problems of traditional file environment

Controls redundancyEliminates inconsistencyUncouples programs and dataEnables organization to centrally manage data and data security

TheDatabaseApproachtoDataManagement

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Advantages of databases

Less redundancyAvoidance of Inconsistency

Efficiency

Data integrity

Confidentiality

Evolution of Database Technologies

Evolution of database systems

• 2000 and beyond – multi –tier, client‐server,• Distributed environments, • Web‐based, • Content‐addressable storage, data mining

DATA BASE MODEL OVERVIEW

• ER‐Model• Hierarchical Model• Network Model• Relational Model• Object‐Oriented Model(s)

A1 A2 A3 ... An

a1 a2 a3 an

b1 b2 a3 cn

a1 c2 b3 bn...

x1 v2 d3 wn

Relational Data Model: summary

• Set theoretic• Domain — set of values

• like a data type• Cartesian product (or product)

• D1 　　D2 　　... 　 Dn• n‐tuples (V1,V2,...,Vn)• s.t., V1 　　D1, V2 　　D2,...,Vn　　Dn

–Relation=subset of cartesian product of one or more domains

• FINITE only; empty set allowed–Tuples = members of a relation inst.–Arity = number of domains–Components = values in a tuple–Domains — corresp. with attributes–Cardinality = number of tuples

Relation as tableRows = tuplesColumns = componentsNames of columns = attributesRelation name + set of attribute names= schemaREL (A1,A2,...,An)

Arity

Cardinality

Attributes

Component

Tuple

Advantages of OODBS

• Designer can specify the structure of objects and their behavior (methods)

• Multimedia Contents• Better interaction with object‐oriented languages such as Java

and C++• Definition of complex and user‐defined types• Encapsulation of operations and user‐defined methods

• A specific type of software for creating, storing,organizing, and accessing data from a database

• Separates the logical and physical views of the data

• Logical view: how end users view data• Physical view: how data are actually structured and

organized

• Examples of DBMS: Microsoft Access, DB2, OracleDatabase, Microsoft SQL Server, MYSQL

Database management system (DBMS)

Capabilities of Database Management Systems

Data definition capability: Specifies structure of database content, used to create tables and define characteristics of fieldsData dictionary: Automated or manual file storing definitions of data elements and their characteristicsData manipulation language(DML): Used to add, change, delete, retrieve data from database

Data that describes the properties or characteristics of other data

Does not include sample dataAllows database designers and users to understand the meaning of the data

Meta data

Structured Query Language (SQL)

Microsoft Access user tools for generation SQLMany DBMS have report generation capabilities for creating polished reports (Crystal Reports)

Each database will have a set of schemas associated with a catalog.

Schema = the structure that contains descriptions of objects created by a user (base tables, views, constraints)

The design of any database is a lengthy and involved task thatcan only be done through a step-by-step process.

The first step normally involves interviewing potential users ofthe database.

The second step is to build an entity-relationship model (ERM)that defines the entities, the attributes of those entities and therelationship between those entities.

DATABASE DESIGN

Designing Databases

Conceptual (logical) design: Abstract model from businessperspective

Physical design: How database is arranged on direct‐access storage devices

Design process identifiesRelationships among data elements, redundant database elementsMost efficient way to group data elements to meet business requirements, needs of application programs

NormalizationStreamlining complex groupings of data to minimize redundant data elements and awkward many‐to‐many relationships

An unnormalized relation contains repeating groups. For example, there can be many parts and suppliers for each order. There is only a one‐to‐one correspondence between Order_Number and Order_Date.

AN UNNORMALIZED RELATION FOR ORDERExample

NORMALIZED TABLES CREATED FROM ORDER

An unnormalized relation contains repeating groups. For example, there can be many parts and suppliers for each order. There is only a one‐to‐one correspondence between Order_Number and Order_Date.

Entity‐relationship diagramUsed by database designers to document the data modelIllustrates relationships between entities

1:1, 1:N, N:M Relation Diagram

Very large databases and systems require special capabilities, tools To analyze large quantities of data To access data from multiple systems

Three key techniques1.Data warehousing 2.Data mining3.Tools for accessing internal databases through the Web

UsingDatabasestoImproveBusinessPerformanceandDecisionMaking

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DATA WAREHOUSES AND DATA MINING

• Data warehouses support OLAP and decision making

• Data warehouses do not support OLTP• Data‐mining tools are the tools you use to work with a data warehouse– DBMS software = database– Data‐mining tools = data warehouse

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What Is a Data Warehouse?

• Data warehouse – logical collection of information – gathered from operational databases – used to create business intelligence that supports business analysis activities and decision‐making tasks

The view that is showing is product versus region. If you rotate the cube 90 degrees, the face that will show is product versus actual and projected sales. If you rotate the cube 90 degrees again, you will see region versus actual and projected sales. Other views are possible.

MULTIDIMENSIONAL DATA MODEL

TheDatabaseApproachtoDataManagement

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Functions

• Online transaction processing (OLTP) – the gathering of input information, processing that information, and updating existing information to reflect the gathered and processed information– Databases support OLTP– Operational database – databases that support OLTP

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Functions

• Online analytical processing (OLAP) – the manipulation of information to support decision making– Databases can support some OLAP– Data warehouses only support OLAP, not OLTP– Why?– Data warehouses are special forms of databases that support decision making

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Data Marts• Data warehouses can support all of an organization’s information

• Data marts have subsets of an organizationwide data warehouse

• Data mart – subset of a data warehouse in which only a focused portion of the data warehouse information is kept

Business Intelligence(BI):

Tools for consolidating, analyzing, and providing access to vast amounts of data to help users make better business decisions

E.g., Harrah’s Entertainment analyzes customers to develop gambling profiles and identify most profitable customersPrinciple tools include:

Software for database query and reportingOnline analytical processing (OLAP)Data mining

Object in Business Information Systems

More definition

Predictive analysis in Data Mining;

Uses data mining techniques, historical data, and assumptions about future conditions to predict outcomes of events

E.g., Probability a customer will respond to an offer

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Information Vs. IntelligenceAnalysis, Prediction, Decision Data

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What Are Data‐Mining Tools?

• Data‐mining tools – software tools that you use to query information in a data warehouse– Query‐and‐reporting tools– Intelligence agents– Multidimensional analysis tools– Statistical tools

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What Are Data‐Mining Tools?

Converging Disciplines

9‐38 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall

© Gabriele Piccoli

The EAI Approach

ERP

Legacy Application

Database 1

Middlew

are

Database 2

Legacy Application

SCM

SCM: Supply Chain ManagementERP: Enterprise Resource Planning

Enterprise application integration (EAI) is the use of software and computer systems architectural principles to integrate a set of enterprise computer applications

© Gabriele Piccoli

CRM Infrastructure

DSS ComponentsData Management Subsystem

• DSS database • DBMS • Data directory • Query facility

A Web‐Based DSS Architecture

Expert Systems vs. DSS

Expert System• Inject expert knowledge in

to a computer system.• Automate decision making.• The decision environments

have structure• The alternatives and goals

are often established in advance.

• The expert system can eventually replace the human decision maker.

Decision Support System• Extract or gain knowledge

from a computer system• Facilitates decision making• Unstructured environment• Alternatives may not be

fully realized yet• Use goals and the system

data to establish alternatives and outcomes, so a good decision can be made

Webs, Documents areData Where House Too

What challenges does the increase in unstructured data present for businesses?How does text‐mining improve decision‐making?What kinds of companies are most likely to benefit from text mining software?

In what ways could text mining potentially lead to the erosion of personal information privacy?

WHAT CAN BUSINESSES LEARN FROM TEXT MINING? Text mining

Extracts key elements from large unstructured data sets (e.g., stored e‐mails)

Web miningDiscovery and analysis of useful patterns and information from WWW

E.g., to understand customer behavior, evaluate effectiveness of Web site, etc.

Web content miningKnowledge extracted from content of Web pages

Web structure miningE.g., links to and from Web page

Web usage miningUser interaction data recorded by Web server

Databases and the WebMany companies use Web to make some internal databases available to customers or partnersTypical configuration includes:

Web serverApplication server/middleware/CGI scriptsDatabase server (hosting DBM)

Advantages of using Web for database access:Ease of use of browser softwareWeb interface requires few or no changes to databaseInexpensive to add Web interface to system

Firms use the Web to make information from theirinternal databases available to customers and partners

• Middleware and other software make this possible

• Database servers• CGI(Computer Gateway Interface)• Web interfaces provide familiarity to users andsavings over redesigning and rebuilding legacysystems

Users access an organization’s internal database through the Web using their desktop PCs and Web browser software.

LINKING INTERNAL DATABASES TO THE WEB

Establishing an information policyFirm’s rules, procedures, roles for sharing, managing, standardizing dataData administration:

Firm function responsible for specific policies and procedures to manage data

Data governance: Policies and processes for managing availability, usability, integrity, and security of enterprise data, especially as it relates to government regulations

Database administration:Defining, organizing, implementing, maintaining database; performed by database design and management group

ManagingDataResources

Basic : True Data

Good: Many(File, Record)

Better : Organized(Database, Data Where house)

Best : Analysis, Intelligence( Data mining, Intelligence)

Nature and Quality of Data

TELECOMMUNICATIONS, THE INTERNET,AND WIRELESS TECHNOLOGY

Chapter

EAI with IT

Computer Systems+ Network Architecture + Communications+ Business Resource Applications

Summary of Previous Network Architecture

Internet, Web + Mobile Applications

Competitive Advantages in the Business

General Review

• Fundamentals of Telecommunications• Networking Media, Devices, and Software• Wireless Telecommunications Technologies• Networks and Distributed Computing

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Main topics

• Telecommunications– Refers to the electronic transmission of signals for communication

– Networking media, devices, software

• Types of cables used in telecommunications– Twisted pair cables, coaxial cable, and fiber optic cable

• Networking devices include – Modems, network adapters, network control devices, RFID devices, and pagers

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Main Topics

• Cellular network– Radio network – Geographic area is divided into cells with a transceiver antenna (tower) and station at the center of each cell

• Networks are classified by size– PAN, MAN, WAN, GAN

• Server computers – Used to distribute data, files, and programs to users, or clients, on the network

• Home networks – Used to share hardware, files, and a common Internet connection

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Fundamentals of Telecommunications

• Communications– Transmission of a signal by way of a medium

• Signal – Contains message comprised of data and information

• Communication medium – Anything that carries a signal between a sender and a receiver

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Telecommunications and Data Communications

• Telecommunications – Electronic transmission of signals for communications

• Data communications– Electronic transmission and reception of digital data

• Telecommunications network – Connects communications and computing devices

• Networking media– Anything that carries an electronic signal

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Telecommunicationsand Data Communications

• Networking media– Anything that carries a signal and creates an interface between a sender and receiver

• Networking hardware devices and networking software work together to enable and control communications signals

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Characteristics of Telecommunications

• Analog signal– Fluctuates continuously

• Digital signal– Discrete voltage– State is either high or low– The speed at which a signal can change from high to low is called the signal frequency

• Bandwidth– Data transmission rate– Measured in bits per second (bps)

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• Broadband or high‐speed Internet– Connection that is always on or active– Faster than dial‐up

• Narrowband– Any medium with a speed less than 200 Kbps

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Networking Media – Physical Cables

• Twisted pair cable– Consists of pairs of twisted wires covered with an insulating layer

• Coaxial cable– Consists of an inner conductor wire surrounded by insulation, a conductive shield, and a cover

• Fiber‐optic cable– Consists of thousands of extremely thin strands of glass or plastic bound together in a sheathing

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• Fiber‐optic cable has several advantages over traditional copper cable– Speed– Size– Clarity– Security

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Radio Signals and Light

• Radio wave– Electromagnetic wave transmitted through an antenna at different frequencies

– FCC assigns different frequencies for different devices

• Microwaves– Sent at the high end of the spectrum (1‐300 GHz)

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Networking Devices

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Networking Devices

• Modems– Modulates and demodulates signals – Cable modem

• Provides Internet access over a cable television network – DSL modem

• Provides high‐speed Internet service over telephone lines

• Network adapter– Computer circuit board, PC Card, or USB device

• Network interface card (NIC)• Wireless adapters

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Network Control Devices

• Hubs– Used as a central point for connecting a series of computers

• Switches– Fundamental part of most networks– Allow several users to send information at the same time

without slowing the network

• Repeaters– Connect multiple network segments

• Bridges– Connect two or more network segments

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Network Control Devices

• Gateways– Network points that act as an entrance to another network

• Routers – Can divide a single network into two logically separate networks

• Wireless access point– Receives and transmits data to wireless adapters

• Firewall – Device or software that filters the information coming onto a network, generally to increase security and remove unwanted traffic

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A modem is a device that translates digital signals into analog form (and vice versa) so that computers can transmit data over analog networks such as telephone and cable networks.

FUNCTIONS OF THE MODEM

MODEMS

An illustration of data sent using a modem and a regular telephone line.

A modem is a device that converts digital data originating from a terminal or computer, to analog signals used by voice communication networks such as the telephone system. At one end, modems convert the digital pulses to audible tones and convert audio tones back to digital pulses at the other.

The word "Modem" stands for "MOdulator‐DEModulator".

Networks for Beginners: http://compnetworking.about.com/

MODEMS

• Transmission speed

Modems are available in different transmission speeds, which are measured in BPS (bits per second) also called BAUD rate. Standard modems speeds: 9600 baud, 14400 baud, 28800 baud, 33600 baud, 56800 baud.

• Internal/External

Internal modems are electronic cards. An internal modem is installed in one of the computer's expansion slot. External modems are fully functioning external devices. The external modem is connected to a computer using a serialcable to one of the computer's serial ports, and draws power from an external power source.


HUBS

The original Ethernet LANs relied on certain physical characteristics of the cable carrying the network data (usually coaxial cable). New Ethernet technologies introduced new cable types that we unable to fulfill the original physical requirements.

New devices ‐ hubs ‐ were introduced to simulate those characteristics. Simply put, the hub's major function is to replicate data it receives from one device attached to it to all others.


REPEATERS

An illustration of a repeater at workThe electrical signal entering the repeater at one end is weakened.The repeater amplifies the electrical signals and resends the data.

A repeater is connected to two cable segments. Any electrical signal reaching the repeater from one segment, will be amplified and retransmitted to the other segment. A common problem in the networking world is that of weakening electrical signals. Electrical signals traveling through wires (such as copper wires used in most networks), weaken due to the wire's electrical resistance. This effect limits the lengths of the cable that can be used. A repeater will overcome this limit, when there is a need to connect two computers at a larger distance.


ROUTERS

• Routers connect two or more networks and forward data packets between them. When data arrives from one of the segments, the router decides, according to it's routing table, to which segment to forward that data.


GATEWAY

• "Gateway" is a term that was once used to refer to a routing device. Today, in the TCP/IP world, the term "router" is used to describe such a device.

The term gateway now refers to special‐purpose devices, that perform protocol conversions. Gateways implement application layer conversions of information received from various protocols.

• Examples of gateways found on today's markets are: – VocalTec Gateway: A gateway that converts human speech traveling on

analog phone lines into local area network protocol data, and visa‐versa.

– RadVision Gateway: Converts video from digital phone lines into local area network protocol data, and visa‐versa.


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Firewalls

• Firewall A machine and its software that serve as a special gateway to a network, protecting it from inappropriate access

– Filters the network traffic that comes in, checking the validity of the messages as much as possible and perhaps denying some messages altogether

– Enforces an organization’s access control policy

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Firewalls

Figure 15.8 A firewall protecting a LAN

EXAMPLE OF FIREWALL

• Firewalls are systems that establish access control policies among networks. They can block information from entering a network or from getting out of that network, they can permit different users to perform different kinds of operations, according to the user's authorizations.


Industrial TelecommunicationsMedia and Devices

• Microwave transmission– Also called terrestrial microwave– Line‐of‐sight medium

• Communications satellite– Basically a microwave station placed in outer space

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Networking Software

• Networking software– Monitors the load, or amount of traffic, on the network

– Provides error checking and can often indicate problems and possible solutions

– Can provide data security and privacy

• Network administrator or systems administrator– Person responsible for setting up and maintaining the network

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Wireless Fidelity and WiMAX

• Wireless fidelity (Wi‐Fi)– Makes use of access points to wirelessly connect users to networks within a range of 250–1000 feet (75‐300 meters)

• WiMAX– Known as IEEE 802.16– Faster and longer range than Wi‐Fi– WiMAX antenna has 31‐mile range

• Perfect for city‐wide Internet access

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Bluetooth

• Enables digital devices to communicate directly with each other wirelessly over short distances

• Communicates at speeds of up to 1 Mbps within a range of up to 33 feet (10 meters)

• Can connect devices to a computer network using access points like Wi‐Fi

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Radio Frequency Identification (RFID)

• Uses tiny transponders in tags that can be– Attached to merchandise or other objects – Read using an RFID transceiver or reader for the purpose of identification

– Primarily used to track merchandise from supplier to retailer to customer

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Computer Networking Concepts

• Nodes– Devices attached to a network

• Workstations– Computers attached to a network

• Local resources – Files, drives, or other peripheral devices connected to the workstation and accessible via the network

• Network or remote resources– Workstation accesses over the network– Transparency provides user‐friendly environment

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Distributed Computing

• Distributed Computing– Multiple remote computers working together

• Database servers– Store databases and respond to queries

• File servers– Store files and deliver them to users upon request

• Application servers– Store programs and deliver them to desktops when users click the icon

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• Blade computing– Cheaper alternative– Takes advantage of the fact that at any one time, 30% of system PCs are not being used

• PCs are replaced with thin clients– Keyboard, mouse, display, unit to connect the device to the server

– Thin clients cost less than half the cost of a PC

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A blade server is a stripped‐down server computer with a modular design optimized to minimize the use of physical space and energy.

IBM HS20 blade server


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Network Types

• Personal area network (PAN)– Interconnecting personal information technology devices– Typically wireless

• Local Area Network (LAN)– Connects computer systems within same building – Can use various designs or topologies

• Intranet– Uses protocols of the Internet and the Web within the confines

of a private network• Virtual Private Network (VPN)

– Enables private Internet communications

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Network Types

• Metropolitan area network (MAN)– Connects networks within a city or metropolitan‐size area into a larger high‐speed network

• Wide area network (WAN)– Connects LANs and MANs between cities, across country, and around the world

• Global Networks– A WAN that crosses an international border (transborder data flow)

– Data havens have few restrictions on telecommunications or databases

• Electronic Data Interchange (EDI)– Connects corporate computer systems

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Network Types

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Network Types

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Problem: Shipbuilding space is too large (4.2 sq mi) and complex to track inventory in real‐time, limiting efficiencySolution: High‐speed wireless network built by KT Corp, using radio sensors, notebooks, mobiles, Web camsIllustrates:

Powerful capabilities and solutions offered by contemporary networking technologyUse of radio sensor technologies to track inventory

HyundaiHeavyIndustriesCreatesAWirelessShipyard

Networking and communication TrendsConvergence:

Telephone networks and computer networks converging into single digital network using Internet standardsE.g. cable companies providing voice service

Broadband:More than 60% U.S. Internet users have broadband access

Broadband wireless: Voice and data communication as well as Internet access are increasingly taking place over broadband wireless platforms

TelecommunicationsandNetworkinginToday’sBusinessWorld

What is a computer network?

Two or more connected computers

Major components in simple networkClient computer Server computerNetwork interfaces (NICs)Connection mediumNetwork operating systemHub or switch

RoutersDevice used to route packets of data through different networks, ensuring that data sent gets to the correct address

Illustrated here is a very simple computer network, consisting of computers, a network operating system residing on a dedicated server computer, cable (wiring) connecting the devices, network interface cards (NICs), switches, and a router.

COMPONENTS OF A SIMPLE COMPUTER NETWORK

Components of networks in large companies

Hundreds of local area networks (LANs) linked to firmwide corporate networkVarious powerful servers

Web siteCorporate intranet, extranetBackend systems

Mobile wireless LANs (Wi‐Fi networks)Videoconferencing systemTelephone networkWireless cell phones

Today’s corporate network infrastructure is a collection of many different networks from the public switched telephone network, to the Internet, to corporate local area networks linking workgroups, departments, or office floors.

CORPORATE NETWORK INFRASTRUCTURE

Key networking technologies

Client/server computingDistributed computing modelClients linked through network controlled by network server computerServer sets rules of communication for network and provides every client with an address so others can find it on the networkHas largely replaced centralized mainframe computingThe Internet: Largest implementation of client/server computing

Management Information Systems, Sixth Edition 103

Protocols

• Protocol: set of rules governing communication between computers

• Some protocols are designed for WANs, LANs, and wireless communications

• Most important set of protocols for telecommunications and networks is called TCP/IP

Key networking technologies (cont.)

TCP/IP and connectivityConnectivity between computers enabled by protocolsProtocols: Rules that govern transmission of information between two pointsTransmission Control Protocol/Internet Protocol (TCP/IP)

Common worldwide standard that is basis for InternetDepartment of Defense reference model for TCP/IP

Four layers1. Application layer2. Transport layer3. Internet layer4. Network interface layer


TCP/IP

• TCP/IP (Transmission Control Protocol/ Internet Protocol): a set of related protocols– TCP ensures packets arrive accurately and in proper order

– IP ensures efficient delivery of packets from node to node

• Internet backbone: highest speed channels• Host: a computer connected directly to a backbone

• IP number: unique numerical identification for a network device


TCP/IP (continued)

• DNS (Domain Name Service): associates a character‐based name with an IP address

• Static IP address: a permanent address assigned to a device

• Dynamic IP address: temporary IP number assigned to a device for the duration of the connection– Provides flexibility when the number of IP addresses is limited


Ethernet

• Ethernet: LAN protocol using coaxial or Cat 5 or 6 twisted pair cable

• Gigabit Ethernet: faster Ethernet connection of one Gbps or greater

• Devices on network contend with other devices for transmission time

• CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol ensures there are no collisions in transmission


Wireless Protocols

• IEEE 802.11: a family of wireless protocols known as Wi‐Fi (Wireless Fidelity)– Supports wireless communication within 100 meters of router

– 802.11 subtypes support various distances and speeds up to 248 Mbps

• Access point (hotspot): connection between wireless device and a wired network– Allows Internet access within range of equipment

Wireless Protocols (continued)

• Encryption: ability to scramble and encode messages– Uses encryption keys shared only between sender and receiver

• Bluetooth: allows devices to communicate within 10 meters– Transmits voice and data– Considered a PAN technology


Key networking technologies (cont.)

Packet switching

Method of slicing digital messages into parcels (packets), sending packets along different communication paths as they become available, and then reassembling packets at destination

Previous circuit‐switched networks required assembly of complete point‐to‐point circuit

Packet switching more efficient use of network’s communications capacity

Packet Switching

• To improve the efficiency of transferring information over a shared communication line, messages are divided into fixed‐sized, numbered packets

• Network devices called routers are used to direct packets between networks

Figure 15.4 Messages sent by packet switching

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PACKED‐SWITCHED NETWORKS AND PACKET COMMUNICATIONS

Data are grouped into small packets, which are transmitted independently over various communications channels and reassembled at their final destination.

THE TRANSMISSION CONTROL PROTOCOL/ INTERNET PROTOCOL(TCP/IP) REFERENCE MODEL

This figure illustrates the four layers of the TCP/IP reference model for communications

Signals: digital vs. analogModem: Translates digital signals into analog form

Types of networksLocal‐area networks (LANs)

Campus‐area networks (CANs)Peer‐to‐peerTopologies: star, bus, ring

Metropolitan and wide‐area networksWide‐area networks (WANs)Metropolitan‐area networks (MANs)

The three basic network topologies are the star, bus, and ring.

NETWORK TOPOLOGIES

NETWORK TOPOLOGIES

Physical transmission media

Twisted wire (modems) Coaxial cableFiber optics and optical networks

Dense wavelength division multiplexing (DWDM)

Wireless transmission media and devicesMicrowaveSatellitesCellular telephones

Transmission speed (hertz, bandwidth)

BP’S SATELLITE TRANSMISSION SYSTEM

Communication satellites help BP transfer seismic data between oil exploration ships and research centers in the United States.

What is the Internet?

Internet Addressing and ArchitectureThe Domain Name System

Hierarchical structureTop‐level domains

Internet Architecture and GovernanceNo formal management: IAB, ICANN, W3C

The Future Internet: IPv6 and Internet2

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Network Addresses

• Hostname A unique identification that specifies a particular computer on the InternetFor example

matisse.csc.villanova.educondor.develocorp.com

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Network Addresses

• Network software translates a hostname into its corresponding IP addressFor example

205.39.145.18

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Network Addresses

• An IP address can be split into– network address, which specifies a specific network– host number, which specifies a particular machine in that network

Figure 15.9 An IP address is stored in four bytes

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Domain Name System

• A hostname consists of the computer name followed by the domain name

• csc.villanova.edu is the domain name– A domain name is separated into two or more sections that specify the organization, and possibly a subset of an organization, of which the computer is a part

– Two organizations can have a computer named the same thing because the domain name makes it clear which one is being referred to

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Domain Name System

• The very last section of the domain is called its top‐level domain (TLD) name

Figure 15.10 Top-level domains, including some relatively new ones

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Domain Name System

• Organizations based in countries other than the United States use a top‐level domain that corresponds to their two‐letter country codes

Some of the top-level domain names based on country codes

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Domain Name System

• The domain name system (DNS) is chiefly used to translate hostnames into numeric IP addresses

– DNS is an example of a distributed database

– If that server can resolve the hostname, it does so

– If not, that server asks another domain name server

Domain Name System is a hierarchical system with a root domain, top‐level domains, second‐level domains, and host computers at the third level.

THE DOMAIN NAME SYSTEM

TheGlobalInternet

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Internet Connections

• Internet backbone A set of high‐speed networks that carry Internet trafficThese networks are provided by companies such as AT&T, GTE, and IBM

• Internet service provider (ISP) A company that provides other companies or individuals with access to the Internet

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• There are various technologies available that you can use to connect a home computer to the Internet

– A phone modem converts computer data into an analog audio signal for transfer over a telephone line, and then a modem at the destination converts it back again into data

– A digital subscriber line (DSL) uses regular copper phone lines to transfer digital data to and from the phone company’s central office

– A cable modem uses the same line that your cable TV signals come in on to transfer the data back and forth

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• Broadband A connection in which transfer speeds are faster than 128 bits per second– DSL connections and cable modems are broadband connections

– The speed for downloads (getting data from the Internet to your home computer) may not be the same as uploads(sending data from your home computer to the Internet)

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Open Systems• Proprietary system A system that uses technologies kept private by a particular commercial vendor

One system couldn’t communicate with another, leading to the need for

• Interoperability The ability of software and hardware on multiple machines and from multiple commercial vendors to communicate

Leading to• Open systems Systems based on a common model of network architecture and a suite of protocols used in its implementation

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Open Systems

• The International Organization for Standardization (ISO) established the Open Systems Interconnection (OSI) Reference Model

• Each layer deals with a particular aspect of network communication

Figure 15.5 The layers of the OSI Reference Model

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Network Protocols

• Network protocols are layered such that each one relies on the protocols that underlie it

• Sometimes referred to as a protocol stack

Layering of key network protocols

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TCP/IP

• TCP stands for Transmission Control ProtocolTCP software breaks messages into packets, hands them off to the IP software for delivery, and then orders and reassembles the packets at their destination

• IP stands for Internet ProtocolIP software deals with the routing of packets through the maze of interconnected networks to their final destination

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TCP/IP (cont.)

• UDP stands for User Datagram Protocol

– It is an alternative to TCP

– The main difference is that TCP is highly reliable, at the cost of decreased performance, while UDP is less reliable, but generally faster

15‐135

High‐Level Protocols

• Other protocols build on the foundation established by the TCP/IP protocol suite

– Simple Mail Transfer Protocol (SMTP)

– File Transfer Protocol (FTP)

– Telnet

– Hyper Text Transfer Protocol (http)

The Internet backbone connects to regional networks, which in turn provide access to Internet service providers, large firms, and government institutions. Network access points (NAPs) and metropolitan area exchanges (MAEs) are hubs where the backbone intersects regional and local networks and where backbone owners connect with one another.

INTERNET NETWORKARCHITECTURE

TheGlobalInternet

THE BATTLE OVER NET NEUTRALITY

What is network neutrality? Why has the Internet operated under net neutrality up to this point in time?Who’s in favor of net neutrality? Who’s opposed? Why?What would be the impact on individual users, businesses, and government if Internet providers switched to a tiered service model?Are you in favor of legislation enforcing network neutrality? Why or why not?

Internet services

E‐mailChatting and instant messagingNewsgroupsTelnetFile Transfer Protocol (FTP)World Wide WebVoIPVirtual private network (VPN)

Client computers running Web browser and other software can access an array of services on servers over the Internet. These services may all run on a single server or on multiple specialized servers.

CLIENT/SERVER COMPUTING ON THE INTERNET

An VoIP phone call digitizes and breaks up a voice message into data packets that may

An VoIP phone call digitizes and breaks up a voice message into data packets that may travel along different routes before being reassembled at the final destination. A processor nearest the call’s destination, called a gateway, arranges the packets in the proper order and directs them to the telephone number of the receiver or the IP address of the receiving computer.

HOW VOICE OVER IP WORKS

This VPN is a private network of computers linked using a secure “tunnel” connection over the Internet. It protects data transmitted over the public Internet by encoding the data and “wrapping” them within the Internet Protocol (IP). By adding a wrapper around a network message to hide its content, organizations can create a private connection that travels through the public Internet.

A VIRTUAL PRIVATE NETWORK USING THE INTERNET

Should managers monitor employee e‐mail and Internet usage? Why or why not?Describe an effective e‐mail and Web use policy for a company.Should managers inform employees that their Web behavior is being monitored? Or should managers monitor secretly? Why or why not?

MONITORING EMPLOYEES ON NETWORKS: UNETHICAL OR GOOD BUSINESS?

The World Wide Web

HTML (Hypertext Markup Language): Formats documents for display on Web

Hypertext Transfer Protocol (HTTP):Communications standard used for transferring Web pages

Uniform resource locators (URLs): Addresses of Web pages

E.g. http://www.megacorp.com/content/features/082602.html

Web serversSoftware for locating and managing Web pages

The World Wide Web (cont.)

Search engines

Started in early 1990s as relatively simple software programs using keyword indexes

Today, major source of Internet advertising revenue via search engine marketing, using complex algorithms and page ranking techniques to locate results

Shopping bots

Use intelligent agent software for searching Internet for shopping information

The Google search engine is continuously crawling the Web, indexing the content of each page, calculating its popularity, and storing the pages so that it can respond quickly to user requests to see a page. The entire process takes about one‐half second.

HOW GOOGLE WORKS

TOP U.S. WEB SEARCH ENGINES

Google is the most popular search engine on the Web, handling 72 percent of all Web searches

Web 2.0Four defining features

1. Interactivity2. Real‐time user control3. Social participation4. User‐generated content

Technologies and services behind these featuresCloud computingBlogs/RSSMashups & widgetsWikisSocial networks

Web 3.0 − the Seman c Web

Effort of W3C to add meaning to existing WebMake searching more relevant to user

Other visionsMore “intelligent” computing3D WebPervasive WebIncrease in cloud computing, SaaSUbiquitous connectivity between mobile and

other access devicesMake Web a more seamless experience

Cellular systems

Competing standards for cellular serviceCDMA: United StatesGSM: Rest of world, plus AT&T and T‐Mobile

Third‐generation (3G) networksSuitable for broadband Internet access 144 Kbps – 2Mbps

4G networksEntirely packet‐switched100 Mbps – 1Gbps

Wireless computer networks and Internet access

Bluetooth (802.15) Links up to 8 devices in 10‐m areaUseful for personal networking (PANs) and in business to transmit data from handheld devices to other transmitters

Wi‐Fi (802.11)Set of standards: 802.11a, 802.11b, 802.11g, 802.11nUsed for wireless LAN and wireless Internet accessUse access points: Device with radio receiver/transmitter for connecting wireless devices to a wired LAN

Bluetooth enables a variety of devices, including cell phones, PDAs, wireless keyboards and mice, PCs, and printers, to interact wirelessly with each other within a small 30‐foot (10‐meter) area. In addition to the links shown, Bluetooth can be used to network similar devices to send data from one PC to another, for example.

A BLUETOOTH NETWORK (PAN)

TheWirelessRevolution

Mobile laptop computers equipped with network interface cards link to the wired LAN by communicating with the access point. The access point uses radio waves to transmit network signals from the wired network to the client adapters, which convert them into data that the mobile device can understand. The client adapter then transmits the data from the mobile device back to the access point, which forwards the data to the wired network.

AN 802.11 WIRELESS LANTheWirelessRevolution

Wireless computer networks and Internet access

Wi‐Fi (cont.)Hotspots: Access points in public place to provide maximum wireless coverage for a specific areaWeak security features

WiMax (802.16)Wireless access range of 31 milesRequire WiMax antennasSprint Nextel building WiMax network as foundation for 4G networks

Radio frequency identification (RFID)

Use tiny tags with embedded microchips containing data about an item and location, and antenna

Tags transmit radio signals over short distances to special RFID readers, which send data over network to computer for processing

Active RFID: Tags have batteries, data can be rewritten, range is hundreds of feet, more expensive

Passive RFID: Range is shorter, also smaller, less expensive, powered by radio frequency energy

Radio frequency identification (RFID) (cont.)

Common uses:

Automated toll‐collection

Tracking goods in a supply chain

Requires companies to have special hardware and software

Reduction in cost of tags making RFID viable for many firms

RFID uses low‐powered radio transmitters to read data stored in a tag at distances ranging from 1 inch to 100 feet. The reader captures the data from the tag and sends them over a network to a host computer for processing.

HOW RFID WORKS

Wireless sensor networks (WSNs)

Networks of hundreds or thousands of interconnected wireless devices embedded into physical environment to provide measurements of many points over large spaces

Devices have built‐in processing, storage, and radio frequency sensors and antennasRequire low‐power, long‐lasting batteries and ability to endure in the field without maintenance

Used to monitor building security, detect hazardous substances in air, monitor environmental changes, traffic, or military activity

The small circles represent lower‐level nodes and the larger circles represent high‐end nodes. Lower level nodes forward data to each other or to higher‐level nodes, which transmit data more rapidly and speed up network performance.

A WIRELESS SENSOR NETWORK


Radio Frequency Identification

• RFID tags are tiny and need little power• Objects are embedded with tags that contain a transponder (a radio transceiver activated by a signal transmitted to it)

• Tags are encoded with electronic product code• Readers decode data stored in tag’s memory and pass the data to a host computer

• Efficient for large companies, but expensive for smaller companies


Converging Technologies• Convergence occurs in networking technology• Cell phones can act as Web phones using VoIP• Television sets will connect to Internet, cable, and satellites concurrently

• PDAs function as televisions sets and phones• Portable music/video players will communicate with PCs to download files and transmit to wireless earphones

• Cell phones will read RFID on products to compare prices and make purchases


Summary

• Telecommunications is communication over distance

• Telecommunications technology has changed the business environment

• Different media have different bandwidths• Networks are classified according to reach and complexity

• Public network can be turned into a virtual private network (VPN)


Summary (continued)

• Two ways to switch a communication line: packet switching and circuit switching

• Network protocols are sets of rules to which all devices on a network must adhere– The Internet adheres to the TCP/IP protocol

• Wireless technologies make it easy and affordable to create wireless LANs and hotspots

• Organizations and individuals have variety of choices when subscribing to networking services


Summary (continued)

• As Internet links become faster, Internet telephony (VoIP) is gaining in popularity

• Wireless technologies support the increasingly popular RFID technologies

• Much like hardware, telecommunications technologies are merging

• Increasing numbers of employees now telecommute

•Telecommunications and Networking in today’s Business WorldNetworking and Communication TrendsWhat is a Computer Network?Key Digital Networking Technologies

•Communications NetworksSignals Digital VS. AnalogTypes of NetworksPhysical Transmission Media

•The Global InternetWhat is the Internet?Internet Addressing and ArchitectureInternet Services and Communication Tools

•The Wireless RevolutionCellular SystemsWireless computer Networks and internet AccessRIFID and Wireless Sensor Networks