Working Outside the Box. MIS 300, Chapter 42 Basic Concepts Telecommunications Basics The...

Working Outside the Box

MIS 300, Chapter 4 2

Basic Concepts

• Telecommunications Basics • The Internet, a network of networks • The World-wide-web, an Internet implementation • Serious Issues


Principles and Learning Objectives -1

• Effective communications are essential to organizational success. – Define the term telecommunications and describe the

function of the components of a telecommunications system.

– Identify the three types of telecommunications carriers and discuss the services they provide.

– Name three distributed processing alternatives and outline their basic features.



• The Internet is like many other technologies—it provides a wide range of services, some of which are effective and practical for use today, others are still evolving, and still others will fade away from lack of use. – Briefly describe how the Internet works, including

alternatives for connecting to it and the role of Internet service providers.



• Originally developed as a document-management system, the World Wide Web is a menu-based system that is easy to use for personal and business applications. – Describe the World Wide Web and the way it works,

including the use of Web browsers, search engines, and other Web tools.



• Because the Internet and the World Wide Web are becoming more universally used and accepted for business, management, service, and speed, privacy and security issues must continually be addressed and resolved. – Identify and briefly describe the applications

associated with the Internet and the Web.– Define the terms intranet and extranet and discuss

how organizations are using them.– Identify several issues associated with the use of

networks.


An Overview of Telecommunications and Networks

• Telecommunications: the electronic transmission of signals for communications

• Telecommunications medium: anything that carries an electronic signal and interfaces between a sending device and a receiving device

• Telecommunications carrier: any business that provides (leases, services) telecommunications media.

• Telecommunications service: any service to customers at least partially facilitated by telecommunications


Communication Model

Sender Channel ReceiverEncoding Decoding

M e s s a g e

Meaning-1

Meaning-2

Challenges:

1. Various processes2. Will meanings match?3. Why encode?4. Purpose? Intention?

Expression Interpretation


Characteristics of Communication

• Encoding/decoding scheme• Speed of transmission (baud)• Directionality (one-way, bidirectional, switchable)• Noise• Equivocation (loss of signal)• Ambiguity (loss of meaning)• Turntaking (protocol)


The Telecommunications Problem


Distance: Sender and Receiver are not in direct contactEquivocation: Message loses power over distanceNoise: Channel introduces unwanted messageCoordination: It’s not clear what a message event is


Solutions to the problems


Distance: Long “wires” of various typesEquivocation: Boosting of power (introduces noise)Noise: Special encoding schemesCoordination: Coordination messages (protocols)

Notice: Nothing about meaning, intention


Basic Economics

• Sources aren’t “on” all the time• Sources make mistakes; repetition is dangerous and costly• Channels are usually relatively expensive• Sharing channels is a good use of an expensive resource;

sharing is costly• All channels are error-prone; the way to compensate is

redundancy• The more complex the scheme, the higher the cost and the

more likely is failure or error.


ANALOG signal: strength

is proportional to “content”

1

What Is a Signal?

• A communication event

• Has a definite start and stop

• Carries information (which is NOT the signal)

0

DIGITAL signal: strength is fixed at either 0 or a

constant

1 1 11 0 0 0


Inside a Digital Signal

Beginning of byte has special “bit” called a start bit

Ending of byte has special “bit” called a

stop bit

The bits that form part of the byte may be ones (at or above a certain level) or zero (below this level). This byte is 1011 0110 (1’s in color)


What Is the Advantage of Digital Signalling?

• First, simplicity, only two signal levels

• Second, resistance to noise

• Third, amplification can work without amplifying noise

• Fourth, potential to add check bits to reconstruct byte in the event of errors (for example, parity checking).


Amplification

Original 0-1Over distance, signal weakens

“On” threashold

Noise intrudes

Signal is “clipped” at threashold level

…and then amplified

…and sent on its way again


The Equipment is Connected

Figure 4.1: Elements of a (Physical) Telecommunications System

This is only what you see!


Transmission Media -1

Table 4.1: Telecommunications Transmission Media Types


Transmission Media - 2

Table 4.1: Telecommunications Transmission Media Types


Telecommunications Devices

Table 4.2: Common Telecommunications Devices


Carriers and Services

• Local exchange carrier (LEC): a public telephone company in the United States that provides service to homes and businesses within its defined geographical area

• Competitive local exchange carrier (CLEC): a company that is allowed to compete with the LECs, such as a wireless, satellite, or cable service provider

• Long-distance carrier: a traditional long-distance phone provider, such as AT&T, Sprint, or MCI


Carriers and Services (continued)

Figure 4.3: Local Exchange Carriers


Networks

• Computer network: the communications media, devices, and software needed to connect two or more computer systems or devices

• Network nodes: the computers and devices on the networks

Node


What Are Networks For?

• At an electrical level, networks move electrons along paths between nodes

• At a signal level, networks move coded characters along links connecting nodes

• At a transportation level, networks move packages or packets of characters between source and destination along paths within the network

• At a session level, networks move messages from sender to receiver.

• At the application level, networks move information from a server to a client.

Businesses can select various ways for this to happen.


Basic Processing Strategies

• Centralized processing: all processing occurs in a single location or facility

• Decentralized processing: processing devices are placed at various remote locations

• Distributed processing: computers are placed at remote locations but connected to each other via a network


Terminal-to-Host, File Server, and Client/Server Systems

• Connecting computers in distributed information processing: – Terminal-to-host: the application and database

reside on one host computer, and the user interacts with the application and data using a “dumb” terminal

– File server: the application and database reside on the one host computer, called the file server

– Client/server: multiple computer platforms are dedicated to special functions, such as database management, printing, communications, and program execution


Terminal-to-Host, File Server, and Client/Server Systems -2

Figure 4.6: Client/Server Connection


Network Types

• Personal area network (PAN)

• Local area network (LAN)

• Metropolitan area network (MAN)

• Wide area network (WAN)

• International network• Corrupt local area network (CLAN)


Network Types -2

Figure 4.7: A Typical LAN


Network Types - 3

Figure 4.8: A Wide Area Network


Communications Software and Protocols

• Communications software: software that provides a number of important functions in a network, such as error checking and data security

• Network operating system (NOS)

• Network management software

• Communications protocol: a standard set of rules that controls a telecommunications connection


Packet Switching

• Sender’s message is broken into (generally short, fixed-length) packets

• Each packet is numbered and sent “into” the network

• The network transmits the packets• The node assembles the packets in order (not an

easy task)• The receiver gets the message from the node.


Example of Packet Switching

Message

FROM: Node 223

TO: Node 456

Count: 4

This is packet 1

This is packet 2

This is packet 3

This is packet 4

223

456

P4

P3P2

P1

P3

P2P4

P1

Packet creation

Packet reassembly

Costs Benefits

Packet creation Better use of networkPacket handling Smaller unitsChance of error More even use of n/wRetransmissions Higher traffic

Transmission: each packet has its own path through the network


Use and Functioning of the Internet

• Internet: a collection of interconnected networks, all freely exchanging information

• ARPANET– The ancestor of the Internet– A project started by the U.S. Department of Defense

(DoD) in 1969

• Internet Protocol (IP): communication standard that enables traffic to be routed from one network to another as needed


How the Internet Works

• The Internet transmits data from one computer (called a host) to another

• If the receiving computer is on a network to which the first computer is directly connected, it can send the message directly

• If the receiving computer is not on a network to which the sending computer is connected, the sending computer relays the message to another computer that can forward it


How the Internet Works (continued)

Figure 4.9: Routing Messages over the Internet


How the Internet Works (continued)

• Data is passed in chunks called packets

• Internet Protocol (IP): communications standard that enables traffic to be routed from one network to another as needed

• Transmission Control Protocol (TCP): widely used transport-layer protocol that is used in combination with IP by most Internet applications

• Uniform Resource Locator (URL): an assigned address on the Internet for each computer


Accessing the Internet

• Connect via a LAN server

• Connect via Serial Line Internet Protocol (SLIP)/Point-to-Point Protocol (PPP)

• Connect via an online service

• Other ways to connect


Accessing the Internet (continued)

Figure 4.10: Several Ways to Access the Internet


Internet Service Providers

• Internet service provider (ISP): any company that provides individuals or organizations with access to the Internet

• Most charge a monthly fee

• Many ISPs and online services offer broadband Internet access through digital subscriber lines (DSLs), cable, or satellite transmission


The World Wide Web

• The Web, WWW or W3

• A menu-based system that uses the client/server model

• Organizes Internet resources throughout the world into a series of menu pages, or screens, that appear on your computer

• Hypermedia: tools that connect the data on Web pages, allowing users to access topics in whatever order they want


The World Wide Web (continued)

• Hypertext Markup Language (HTML): the standard page description language for Web pages

• HTML tags: codes that let the browser know how to format the text on a Web page and whether images, sound, and other elements should be inserted


The World Wide Web (continued)

Figure 4.11: Sample Hypertext Markup Language


Web Browsers

• Web browser: software that creates a unique, hypermedia-based menu on a computer screen, providing a graphical interface to the Web

• The menu consists of graphics, titles, and text with hypertext links

• Ubiquitous and non-proprietary web browsers make it possible for the Internet to be a business platform.


Search Engines

• Search engine: a Web search tool

• Examples: Yahoo.com, Google.com

• Most search engines are free

• Searches can use words, such as AND and OR, to refine the search


Web Programming Languages

• Java– An object-oriented programming language from Sun

Microsystems based on C++– Allows small programs (applets) to be embedded

within an HTML document


Web Services

• Standards and tools that streamline and simplify communication among Web sites for business and personal purposes

• Can also be used to develop new systems to send and receive secure messages between healthcare facilities, doctors, and patients, while maintaining patient privacy


Internet and Telecommunications Services

• E-mail and instant messaging– Instant messaging: a method that allows two or

more individuals to communicate online, using the Internet

• Internet cell phones and handheld computers

• Career information and job searching

• Web log (blog): a Web site that people can create and use to write about their observations, experiences, and feelings on a wide range of topics


Internet and Telecommunications Services (continued)

• Chat rooms: enable two or more people to engage in interactive “conversations” over the Internet

• Internet phone and videoconferencing services

• Content streaming: a method for transferring multimedia files over the Internet so that the data stream of voice and pictures plays more or less continuously without a break, or very few of them

• Shopping on the Web


Internet and Telecommunications Services (continued)

• Web auctions

• Music, radio, and video on the Internet

• Other Internet services and applications


Intranets and Extranets

• Intranet– Internal corporate network built using Internet and

World Wide Web standards and products– Used by employees to gain access to corporate

information– Slashes the need for paper


Intranets and Extranets (continued)

• Extranet– A network based on Web technologies that links

selected resources of a company’s intranet with its customers, suppliers, or other business partners

• Virtual private network (VPN): a secure connection between two points across the Internet

• Tunneling: the process by which VPNs transfer information by encapsulating traffic in IP packets over the Internet


Intranets and Extranets (continued)

Figure 4.12: Virtual Private Network


Net Issues

• Management issues– No centralized governing body controls the

Internet

• Service and speed issues– Web server computers can be overwhelmed by

the amount of “hits” (requests for pages) – More and more Web sites have video, audio clips,

or other features that require faster Internet speeds


Net Issues (continued)

• Privacy– Spyware: hidden files and information trackers that

install themselves secretly when you visit some Internet sites

– Cookie: a text file that an Internet company can place on the hard disk of a computer system

• Fraud– Phishing



• Security with encryption and firewalls– Cryptography: converting a message into a secret

code and changing the encoded message back to regular text

– Digital signature: encryption technique used to verify the identity of a message sender for processing online financial transactions

– Firewall: a device that sits between an internal network and the Internet, limiting access into and out of a network based on access policies



Figure 4.13: Cryptography is the process of converting a message into a secret code and changing the encoded message back into regular text.


Summary

• Telecommunications is the electronic transmission of signals for communications

• A computer network consists of the communications media, devices, and software needed to connect two or more computer systems or devices

• Ways of connecting computers in distributed information processing: terminal-to-host, file server, and client/server


Summary (continued)

• Network types: personal area network (PAN), local area network (LAN), metropolitan area network (MAN), wide area network (WAN), and international network

• The Internet is a collection of interconnected networks, all freely exchanging information

• Internet Protocol (IP) is a communication standard that enables traffic to be routed from one network to another as needed


Summary (continued)

• Uniform Resource Locator (URL) is an assigned address on the Internet for each computer

• An intranet is an internal corporate network built using Internet and World Wide Web standards and protocols

• An extranet is a network based on Web technologies that links selected resources of a company’s intranet with its customers, suppliers, or other business partners

Working Outside the Box. MIS 300, Chapter 42 Basic Concepts Telecommunications Basics The...

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