Business Data Communications and Networking
9th Edition

Jerry Fitzgerald and Alan Dennis
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Introduction to Data Communications

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Outline
• Brief history of Data Communications
– Communications, Information Systems and the Internet

• Data Communications Networks
– Network components, network types

• Network Models
– OSI model, Internet model, transmission via “layers”

• Network Standards
– Standards making, common standards

• Future Trends
– Pervasive networking, integration of voice, video, and data, new information services
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Information Age
• First Industrial Revolution
– Introduction of machinery – New organizational methods – Changed the way people worked

• Second Industrial Revolution – Information Age
– Introduction of computers – Introduction of networking and data communication – Changed the way people worked again • Faster communication  Collapsing Information lag • Brought people together  Globalization
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The Collapsing Information Lag
Historical developments in electronic communications telegraph sped up the rate and volume of transmission of information

1850
Information took days or weeks to be transmitted

1900
Information transmitted in minutes or hours

1950

2007 large quantities of information transmitted in a fraction of a second

growth of telecommunications and especially computer networks

Globalization of networks
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Advances in Phone Technology
Phone invented
1876

first transcontinental and transatlantic phone connections

1915 1919

Packet-switched Telstar data (Telecommunications communications via satellite), Fax services, digital transmission (Tcarriers) 1962 1976 1948
1969 1984

Strowger (stepper) switch, rotary dial phones (enabling automatic connections)

Microwave trunk lines (Canada)

Picturefone (failed commercially)

Cellular telephone
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Regulation of Inventions
FCC established
A time for technological change Regulation began in the USA (ICC) Carterfone court decision allowing non-Bell CPE

Deregulation period
1996

1876

1885
AT&T

1900

1910

1934

1968 1970 1984

Phone invented (rapid acceptance)

Bell System: de facto monopoly

Consent decree by US federal court 1996 US Telecom Act
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millions of phones in use in the US

MCI wins court case; begins providing some long distance services

1984 Consent Decree
Divestiture of 1/1/84: RBOC’s
• AT&T broken up into one long distance company (AT&T) and 7 Regional Bell Operating Companies (RBOC’s)
South Western Bell US West AT&T Bell Atlantic

Pacific Bell

NYNEX Ameritech Bell South

AT&T

Deregulation: IXC’s and LEC’s
• Competitive long distance (IXC) market; MCI & Sprint enter long distance telephone market (among others) • Local Exchange Carrier (LEC) service markets remained under RBOC monopoly
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US Telecom Act of 1996
• Replaced all current laws, FCC regulations, 1984 consent decree, and overrules state laws • Main goal: open local markets to competition • To date, though, local and long distance competition slow to take hold
– Large IXCs expected to move into the local markets, happening only recently – Likewise, RBOCs expected to move into long distance markets, happening only recently
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Worldwide Competitive Markets
• Internet market
– Extremely competitive with more than 5000 Internet Service Providers (ISPs) in the US alone. – Heavy competition in this area may lead to a shake out in the near future.

• World Trade Organization (WTO) agreement (1997)
– commitments by 68 countries to open, deregulate or lessen regulation in their telecom markets

• Multi-national telecom companies
– US companies offering services in Europe, South America – European companies offering services in USA

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History of Information Systems
Batch processing mainframes Online real-time, transaction oriented systems (replaced batch processing. DBMSs become common) PC LANs become common

1950

1960

1970

1980

1990

2000

Data communications over phone lines (became common and mainframes became multiuser systems)

PC revolution
Networking everywhere

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Internet Milestones
Originally called ARPANET, the Internet began as a military-academic network NSFNet created as US Internet backbone commercial access to the Internet begins

1969

1983

1986

1990

1994

2007

ARPANET splits: • Milnet - for military • Internet - academic, education and research purposes only

Government funding of the backbone ends

Worldwide: Over 1 billion Internet users

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Datacom Basics
Telecommunications =
Transmission of voice, video, and/or data - Implies longer distances - Broad term

Data Communications =
Movement of computer information by means of electrical or optical transmission systems

convergence

Broadband Communications
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Three Parts to Understanding Networking
1. Concepts of networking
– – How data moves from one computer to another over a network Theories of how networks operate

2. Technologies in use today
– –
– – –

How theories are implemented, specific products How do they work, their use, applications
Security Network Design Managing the network
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3. Management of networking technologies

Components of a Local Area Network
To other networks (e.g., Internet)

Servers
File Server

Router

HUB

Web Server

Client
Computers

Circuits
Print Server Printer
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Network Types (based on Scale)
• Local Area Networks (LAN) - room, building
– a group of PCs that share a circuit.

• Backbone Networks (BN) -

less than few kms

– a high speed backbone linking together organizational LANs at various locations.

• Metropolitan Area Networks (MAN) - (more than a few kms) – connects LANs and BNs across different locations – Often uses leased lines or other services used to transmit data.

• Wide Area Networks (WANs) - (far greater than 10 kms)
– Same as MAN except wider scale

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LANs and Backbones, Wide Area and Metropolitan Area Networks

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Intranet vs. Extranet
• Intranet
– A LAN that uses the Internet technologies within an organization – Open only those inside the organization – Example: insurance related information provided to employees over an intranet

• Extranet
– A LAN that uses the Internet technologies across an organization including some external constituents – Open only those invited users outside the organization – Accessible through the Internet – Example: Suppliers and customers accessing inventory information in a company over an extranet

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Layered Implementation of Communications Functions
Applications Applications

Single layer implementation
-Networking with large components is complex to understand and implement

OS

OS

Applications

Applications

Multi layer implementation
-Breaking down into smaller components -Easier to implement
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OS

OS

Multi-layer Network Models
• The two most important such network models: OSI and Internet • Open Systems Interconnection Model
– Created by International Standards Organization (ISO) as a framework for computer network standards in 1984 – Based on 7 layers

• Internet Model
– – – – Created by DARPA originally in early 70’s Developed to solve to the problem of internetworking Based on 5 layers Based on Transmission Control Protocol/ Internet Protocol (TCP/IP) suite
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7-Layer Model of OSI
Physical DataLink Network Transport Session Presentation Application “Please Do Not Touch Steve’s Pet Alligators”

• Application Layer
– set of utilities used by application programs

• Presentation Layer
– formats data for presentation to the user – provides data interfaces, data compression and translation between different data formats

• Session Layer
– initiates, maintains and terminates each logical session between sender and receiver 1 - 21

7-Layer Model of OSI
• Transport Layer
– deals with end-to-end issues such as segmenting the message for network transport, and maintaining the logical connections between sender and receiver

• Network Layer
– responsible for making routing decisions

• Data Link Layer
– deals with message delineation, error control and network medium access control

• Physical Layer
– defines how individual bits are formatted to be transmitted through the network

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Internet’s 5-Layer Model
Physical DataLink Network Transport Application “Please Do Not Touch Alligators”

• Application Layer
– used by application program

• Transport Layer
– responsible for establishing end-to-end connections, translates domain names into numeric addresses and segments messages

• Network Layer - same as in OSI model • Data Link Layer - same as in OSI model • Physical Layer - same as in OSI model
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Comparison of Network Models

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Message Transmission Using Layers sender receiver
Applications Applications

A receiving layer wraps incoming message with an envelope • Adds layer related addressing information

A receiving layer removes the layer related envelope and forwards the message up
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Protocols
• Used by Network model layers • Sets of standardized rules to define how to communicate at each layer and how to interface with adjacent layers
Layer N+1
Layer N Layer N-1 sender receiver
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Layer N+1

Layer N
Layer N-1

Message Transmission Example

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Points about Network Layer View
• Layers allow simplicity of networking in some ways
– Easy to develop new software that fits each layer – Relatively simple to change the software at any level

• Matching layers communicate between different computers and computer platforms

• Somewhat inefficient

– Accomplished by standards that we all agree on – e.g., Physical layer at the sending computer must match up with the same layer in the receiving computer – Involves many software packages and packets – Packet overhead (slower transmission, processing time) – Interoperability achieved at the expense of perfectly streamlined communication

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Standards
• Importance
– Provide a “fixed” way for hardware and/or software systems (different companies) to communicate – Help promote competition and decrease the price

• Types of Standards
– Formal standards (de jure) • Developed by an industry or government standards-making body – De-facto standards • Emerge in the marketplace and widely used • Lack official backing by a standards-making body

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Standardization Processes
• Specification
– Developing the nomenclature and identifying the problems to be addressed

• Identification of choices
– Identifying solutions to the problems and choose the “optimum” solution

• Acceptance
– Defining the solution, getting it recognized by industry so that a uniform solution is accepted
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Major Standards Bodies
• ISO (International Organization for Standardization)
– Technical recommendations for data communication interfaces – Composed of each country’s national standards orgs. – Based in Geneva, Switzerland (www.iso.ch)

• ITU-T (International Telecommunications Union –Telecom Group
– Technical recommendations about telephone, telegraph and data communications interfaces – Composed of representatives from each country in UN – Based in Geneva, Switzerland (www.itu.int)
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Major Standards Bodies (Cont.)
• ANSI (American National Standards Institute)
– Coordinating organization for US (not a standards- making body) – www.ansi.org

• IEEE (Institute of Electrical and Electronic Engineers)
– Professional society; also develops mostly LAN standards – standards.ieee.org

• IETF (Internet Engineering Task Force)
– Develops Internet standards – No official membership (anyone welcome) – www.ietf.org

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Some Data Comm. Standards
Layer
5. Application layer

Common Standards
HTTP, HTML (Web) MPEG, H.323 (audio/video) IMAP, POP (e-mail) TCP (Internet) SPX (Novell LANs) IP (Internet) IPX (Novell LANs) Ethernet (LAN) Frame Relay (WAN) PPP (dial-up via modem for MAN) RS-232c cable (LAN) Category 5 twisted pair (LAN) V.92 (56 kbps modem)

4. Transport layer 3. Network layer

2. Data link layer

1. Physical layer

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Emerging Trends in Networking
• Pervasive Networking • Integration of Voice, Video and Data • New Information Services

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Pervasive Networking
• Means “Networks will be everywhere” • Exponential growth of Network use • Many new types of devices will have network capability • Exponential growth of data rates for all kinds of networking • Broadband communications
– Use circuits with 1 Mbps or higher (e.g., DSL)
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Relative Capacities of Telephone, LAN, BN, WAN, and Internet Circuits.

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Integration of Voice, Video & Data
• Also called “Convergence”
– Networks that were previously transmitted using separate networks will merge into a single, high speed, multimedia network in the near future

• First step largely complete
– Integration of voice and data

• Next step
– Video merging with voice and data – Will take longer partly due to the high data rates required for video
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New Information Services
• World Wide Web based
– Many new types of information services becoming available • Services that help ensure quality of information received over www

• Application Service Providers (ASPs)
– Develop specific systems for companies such as providing and operating a payroll system for a company that does not have one of its own

• Information Utilities (Future of ASPs)
– Providing a wide range of info services (email, web, payroll, etc.) (similar to electric or water utilities)
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Implications for Management
• Embrace change and actively seek to use new aspects of networks toward improving your organization
– Information moved quickly and easily anywhere and anytime – Information accessed by customers and competitors globally

• Use a set of industry standard technologies
– Can easily mix and match equipment from different vendors – Easier to migrate from older technologies to newer technologies – Smaller cost by using a few well known standards

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