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IST 220-002: Networking and Telecommunications

Chapter 1: Introduction to Computer Networks & Data Communication

Dr. Lee Giles

001 Thomas Building, School of IST

Phone 865 7884

Email: [email protected]

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Information Technology (IT)Information Technology (IT)

Communication Communication TechnologyTechnology

Computer Computer TechnologyTechnology

To collect, store, process, search, retrieve, and present electronic information to meet the needs of various kinds of users, e.g., computer hardware & software, PDAs, printers, groupware, smart cards….

What is Information Technology (IT)?

To deliver, disseminate, exchange, transmit, and receive electronic information in local, regional or global contexts, e.g., networks, fax machines, cell phones, email, satellites, GPS, Internet, telephony, ….

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Computer Systems Redefined

Computer systems used to be defined as:

Computer systems are now redefined as:

hardwarehardware

networksnetworkssoftwaresoftwarehardwarehardware

softwaresoftware+

+ +

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Information & Communication

Generation and transfer of information is critical to today’s businesses

Flow of information both mirror and shape organizational structures

Networks are the enabling technology for this process

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The “Manager’s Dilemma”

Technology is necessary for competitiveness

Cost of technology has decreased Reliance on technology has increased Number of choices have increased Choices are both more difficult and

more important

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What is Data Communication?

Communication of data between sources Data formats – analog or digital or both Data travels by a medium

Wires Space

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Essentials of Data Communication

Message Sender Receiver Medium Understandability Error detection Security

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Types of Messages

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Protocols

Enables communication – how we communicate (convention used for establishing transmission rules) When Where How What with How much

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Protocols

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Important Dates in the History of Data Communications (1)

1837 – Invention of the telegraph 1876 – Invention of the telephone 1947 – Invention of the transistor (replaced vacuum tubes) 1948 – First commercial computer installed, the UNIVAC I 1958 – First U.S. Communications satellite sent into orbit 1959 – FCC approves private microwave communications

networks 1964 – Packet switching network concept proposed by the

Rand Corporation 1966 – IBM's binary synchronous (BISYNC or BSC)

protocol announced 1969 – ARPANET, first packet switching network (later to

become the Internet), begins operation

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Important Dates in the History of Data Communications (2)

1972 – Ethernet local area network specifications formulated 1972 – IBM's Synchronous Data Link Control (SDLC) protocol

announced 1974 – IBM announces its Systems Network Architecture (SNA) 1975 – Personal computers introduced, the Altaire 8800 replaced

terminals in many cases 1981 – IBM PC introduced 1985 – Cellular radio telephones are introduced 1990 – World Wide Web is introduced 1993 – Web search engines introduced 1995 – The Internet grows to over four million host computers 1999 – The Internet grows to over ten million host computers

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Data Communication Applications (1)

Batch - bi-directional transfers of large amounts of data in concentrated groups

Data Entry - Lengthy inputs with short responses

Distributed - data and/or processing is handled by more than one processing unit

Inquiry/Response - Small inputs of data that may result in large responses

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Data Communication Applications (2)

Interactive - Short inputs and outputs. Real-time response with direct user interaction

Sensor-Based - Input derived from sensors instead of human operators

Combined - More than one of the above applications running at the same time

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What is a Computer Network?Two or more computers or communications devices connected by transmission media and channels and guided by a set of rules for communication purposes that allow users to communicate with each other and share applications and data.

Hardware:Computer

Network card Routers

Modem …

Hardware:Computer

Network card Routers

Modem …

Media:Cable Wire

Microwave …

Media:Cable Wire

Microwave …

Software:Network OSUtilities …

Software:Network OSUtilities …

Network Design:Logical layout

Physical layout …

Network Design:Logical layout

Physical layout …

Components of a Computer Network

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Applications of a Computer Network

Mass transit Interstate highways 24-hour bankers, grocery stores Cable television Pagers Mobile telephones Most businesses and schools Retail outlets …

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Technologies

•Ethernet•Token Ring•Transmission Control

Protocol/Internet

Protocol (TCP/IP)•Wireless Application

Protocol (WAP)

Network OS

•Bus Topology

•Ring Topology

•Star Topology

•Local Area Network (LAN)

•Metropolitan Area Network (MAN)

•Wide Area Network (WAN)

•Client/Server

•Peer-to-Peer

Models

Topologies

Types

Network Essentials

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Network Technologies

Based on bus topology; but can be used in star topology; Higher speed: first Fast Ethernet, then Gigabit Ethernet; Most popular: inexpensive, easy to install and maintain.

EthernetEthernet

Token RingToken Ring

TCP/IPTCP/IP

WAPWAP

Based on a ring topology; but can use a star topology; Token-passing scheme to prevent collision of data; The second most widely-used protocol after Ethernet.

Based on client/server model of network computing; Uses packet switching technique for data transmission; Commonly used for Internet applications.

Uses client/server model of network computing; Allows wireless devices to access the Internet and

WWW; Meets increasing demands for wireless Internet access.

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The World of Connectivity

Wired or wireless communications links offer several options for information and communications.

Source: The McGraw-Hill Companies, Inc., 1999

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Computer Network Configurations:Connections between Networks

Computer terminal to mainframe computer

Microcomputer to mainframe computer

Microcomputer to local area network

Microcomputer to Internet

Local area network to local area network

Local area network to wide area network

Sensor to local area network

Satellite and microwave

Wireless telephone

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Computer Network Configurations: Computer Terminal to Mainframe Computer

Used in many types of businesses for data entry and data retrieval.

Usually involves a low-speed connection.

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Computer Network Configurations: Microcomputer to Local Area Network

Very common throughout business and academic environments.

Typically a medium- to high-speed connection.

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Computer Network Configurations:Microcomputer to Internet

Very popular with home users.

Typically a modem is used to connect user’s microcomputer to an Internet Service Provider.

Newer technologies such as DSL and cable modems are replacing modems.

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Computer Network Configurations:LAN to LAN Connections

Found in businesses and schools that have two or more LANs and a need for them to intercommunicate.

The bridge is a typical device used to interconnect LANs.

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Data Communications and Computer Networks Chapter 1

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Computer Network Configurations:LAN to WAN Connections

One of the best ways to interconnect a user on a workstation to the Internet (a wide area network).

A router is the typical device that performs LAN to WAN connections.

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Computer Network Configurations:Sensor to LAN Connections

Often found in industrial environments.

Assembly lines and robotic controls depend heavily on sensor-based local area networks.

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Computer Network Configurations:Satellite and Microwave

Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services.

Typically expensive services but many companies offer competitive services and rates.

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Computer Network Configurations: Wireless Telephone

Quickly expanding market across the U.S. and world.

First generation analog services and second generation PCS services available in most areas and under many types of plans.

Third generation services beginning to appear in Europe and Asia.

Why Are Networks Important?

BUSINESSENTERPRISE

•Traditional Data•Text•Images

Information•Graphics•Voice•Video•Multi-media

Applications•Functions•Organizational Processes•Personal

Users

•Enterprise•Organization•Department•Individual

Network

•LANs•Mans•WANs

Internet

•Wired•Wireless

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Networks: Pros and Cons

Resource sharing Printers, CD-ROMs, computers

Data and information sharing

Communications

Reduced Cost

On-line services

Groupware Software that supports group efforts

over a network

Electronic data interchange

Security risks increase with networks

Complexity is associated with networks

Investment is high and return on it may not happen

Pros Cons

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Key Issues of NetworksAccess to the Internet

Network Access Wired access

Cable modem DSL

Wireless access Wireless LAN

RosettaNet – XML based

Network security Goals and Measures Firewalls

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Why Use a Network?

Sharing of Data, messages, graphics … Applications … Devices, e.g., hard drives, backups, printers,

modems, fax machines …

Centralized administration Installing and upgrading application software

Communication and collaboration Teleconferences, group decision support systems

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Class Discussion

If you could design your own home, what kinds of computer network or data communications labor-saving devices would you incorporate?

Using a laptop computer with a wireless connection into the company’s local area network, you download a Web page from the Internet. List all the different network configurations involved in this operation.

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Language of Computer Networks

Important terms and concepts.

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Components of a Network Server

A computer that provides services to other networked computers

Client A computer in a client/server relationship, e.g., a Web browser

Hardware/Software Network card, router, modem, hub/NT operating systems, utilities

…

Media The way to connect computers on a network

Data Files o be shared by network computers

Resources Peripherals, e.g., printers, to be used by network computers

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Media of Networking

Coax cable Twisted pair cable Fiber optic cable Microwave Communications satellite Cellular phones

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Networking Hardware

Workstations

Servers

Bridges

Routers

Hubs and switches

Nodes

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Network Models

Microcomputer users, or clients, share services of a centralized computer called a server.

Computers share equally with one another without having to rely on a central server.

Client/Server Model

Peer-to-Peer Model

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Client/Server

A distinction exists between computers that make available network resources (servers) and those computers that use the resources (clients or workstations).

Pros: Very secure

Centralized servers easy to manage Physically centralized Secure OS

Better performance Centralized backups Reliability

Simple job to do plus built in redundancy

Cons: Require professional administration More hardware intensive

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Peer-to-Peer (p2p)Computers on the network communicate with each others as equals and each

computer is responsible for making its own resources available to other computers on the network.

Pros: Uses less expensive computer networks Easy to administer No NOS (network operating system) required More built-in redundancy

Shared resources – some machine will have what you need

Cons: Individual user performance easily affected Not very secure

Tragedy of the commons – no guarantee others will administer their resources properly (almost guaranteed with over 10 machines)

Hard to back up.

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Client/Server vs. Peer-to-Peer: Advantages and Disadvantages

Advantages: Very secure OS. Better performance. Centralized servers, easy

to manage. Centralized backups. High reliability.

Peer-to-Peer ModelClient/Server Model

Disadvantages: Expensive administration. More hardware intensive.

Advantages: Uses less expensive networks. Easy to administer. Contain both network operating

system and application software. Ideal for small business and home

users.

Disadvantages: Individual user performance easily

affected. Not very secure. Hard to back up.

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Networking Essentials

Computer Networks A host computer connected with communication circuits

and equipment to terminals Two or more computers connected via a communication

medium

Intranet A private version of the Internet

Enterprise Network Two or more LANs connected to each other, or one or

more LANs connected to a WAN

File Server A computer that contains files shared by PCs on a network

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Categorization of Networks

By size: Wide Area Network (WAN) Metropolitan Area Network (MAN) Local Area Networks (LAN)

By capability: Client/server Peer-to-peer

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Three Major Types of Networks

Local Area Network (LAN) Serves users within a confined geographical area

(usually within a mile).

Metropolitan Area Network (MAN) Covers a geographic area the size of a city or

suburb. The purpose of a MAN is often to bypass local telephone companies when accessing long-distance service.

Wide Area Network (WAN) Covers a wide geographical area, such as a state or

a country. Examples: Tyment, Telenet, Uninet, and Accunet.

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Interconnection between LANs and WANs

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Characteristics Differentiate One Network from Another

Topology : The geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a bus or in a star topology. Protocols : The rules and encoding specifications for sending data. The protocols also determine whether the network uses a peer-to-peer or client/server model. Media : Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables. Wireless networks are connected via radio waves.

Medium Access Control: Scheme to allow sharing of the media.

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Components of a Typical LAN


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Network Typologies: StarThis arrangement connects all the network’s devices to a central host computer, through which all communications must pass.


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Network Typologies: RingThis arrangement connects the network’s devices in a closed loop.


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Network Typologies: BusA single channel connects all communications devices.


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Networking and Telecommunications

Networking - an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic distancesTelecommunications - study of telephones and the systems that transmit telephone signalsNetwork management - design, installation, and support of a network and its hardware and software

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Networking Aspects Computer Networks

A host computer connected with communication circuits and equipment to terminals

Two or more computers connected via a communication medium

Intranet A private version of the Internet

Enterprise Network Two or more LANs connected to each other, or one or more

LANs connected to a WAN

File Server A computer that contains files shared by PCs on a network

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Network Selection Criteria

Size of the organization Level of required security Level of available administrative support Amount of network traffic Needs of the network users Budget for building the network

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Requirements of a Network System (1)

Ideal system Does what we want instantly when we want it

with no errors or problems and only we know about it. Performance Consistency Flexibility Availability Reliability Recovery Security

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Performance Response time

Time for transmission Time for data processing

Transaction Rate (throughput) The amount of work performed by a system per unit

of time

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Consistency Same thing all the time Response time

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Flexibility Growth and change available with

minimum impact on users Legacy systems Standards help

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Availability When needed Where available How available

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Reliability Measure of system failure

MTBF – mean time between failure Fault-tolerance solution

DesignDuplication

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Recovery All systems fail

How long before startup?

What do we get when the system starts up again Saved information

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Security Who has access? How good is the protection?

Privacy

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Network Architecture Models

A reference model that describes the layers of hardware and software necessary to transmit data between two points.

Reference models are necessary to increase the likelihood that different components from different manufacturers will converse.

There are two standard models that are important: The OSI Model, and the Internet Model.

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Standards

Standards are rules of operation that are followed by most or all vendorsStandards allow hardware and software from different vendors to work togetherCompetition among vendors brings lower prices and feature-rich products

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Standards

ISO - International Standards Organization: An organization that sets communication standards, also IEEEOSI - Open Systems Interconnection: A seven layer reference model for developing data communication systems Open Architecture - in which the network specifications are available to any company

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OSI Layers of Communication

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Application Layer

Where the application using the network resides. Common network applications include remote login, file transfer, e-mail, and web page browsing.

Functionality defined by user Application dependent

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Presentation Layer

Performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver

Format of the data Encryption Compression Screen formatting

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Session Layer

Establishes connection between applications

Enforces rules Order Pacing

Reestablish connection

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Transport Layer

Provides an end-to-end, error-free network connection.

Makes sure the data arrives at the destination exactly as it left the source.

Makes sure all information is accounted for: Missing information Duplicated information

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Network Layer

Responsible for creating maintaining and ending network connections.

Transfers a data packet from node to node within the network.

Message routing Billing Accounting

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Data Link Layer

Responsible for taking the data and transforming it into a frame with header, control and address information.

Physical path communication Error detection Error correction Resolve competing requests

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Physical Layer

Handles the transmission of bits over a communications channel.

Includes: Voltage levels Electrical connections Media choices Adapters Connectors Modulation techniques

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Layers in Internet Model vs. OSI Model

Interface layer - equivalent to the OSI’s physical and data link layers.

Network layer - roughly equivalent to the OSI’s network layer.

Transport layer - performs same function as OSI transport layer.

Application layer - equivalent to the OSI’s presentation and application layers.

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The Internet Model vs. the OSI Model

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Internet Model in Action

Note the flow of data from user to web browser and back.

At each layer, information is either added or removed, depending on whether the data is leaving or arriving at a workstation.

The adding of information over pre-existing information is termed encapsulation.

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Logical and Physical Connections

A logical connection is one that exists only in the software

A physical connection is one that exists in the hardware.

In a network architecture model, only the lowest layer contains a physical connection, while all higher layers contain logical connections.

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OSI Layers of Communication

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Software Environment Application Programs

Word, Excel, Access, Lotus 123, etc.

Operating System Manages the resources of the computer. (E.G. Windows 98/NT, Linux)

Data Communication Responsible for handling communication with remote devices Transaction Control Process

Receives input and routes it to the proper application processes

Database Management System Interface between the application programs and the data they need to use.

Transaction Processing Responding to requests for processing activities. The requests are usually

user initiated but may be made by other systems

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IT Infrastructure

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Class Discussion

How have you used a network today. Discuss an example of a business that incorporates

layers of management and show how the work progresses through the layers.

Are there any network configurations that have not been addressed in the chapter? What are their applications?

Are there any other examples in business where one particular technology or method has won out over the competition? What were the reasons that lead to this particular technology winning?

Joining Professional Associations

Benefits can include:Connecting with people who have similar interestsProviding new opportunities for learningAllowing access to specialized informationGiving tangible assets such as free goods

Professional Association Sites

TABLE 1-2

Web sites of networking organizations

Circa 2000. Some do not exist today!

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