IST 220-002: Networking and Telecommunications Chapter 1: Introduction to Computer Networks

1
IST 220-002 Networking and TelecommunicationsCh
apter 1 Introduction to Computer Networks
Data Communication

• Dr. Lee Giles
• 001 Thomas Building, School of IST
• Phone [phone]
• Email giles_at_ist.psu.edu

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What is Information Technology (IT)?
Information Technology (IT)
Communication Technology
Computer Technology
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.
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
hardware
software

Computer systems are now redefined as
networks
software
hardware


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Information Communication

• Generation and transfer of information is
  critical to todays businesses
• Flow of information both mirror and shape
  organizational structures
• Networks are the enabling technology for this
  process

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The Managers 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

• Media
• Cable
• Wire
• Microwave

Components of a Computer Network

• Software
• Network OS
• Utilities

• Network Design
• Logical layout
• Physical layout

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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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Network Essentials
Models

• Client/Server
• Peer-to-Peer

Technologies
Types

• Ethernet
• Token Ring
• Transmission Control Protocol/Internet Protocol
  (TCP/IP)
• Wireless Application Protocol (WAP)

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

Network OS
Topologies

• Bus Topology
• Ring Topology
• Star Topology

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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.

Ethernet

• 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.

Token Ring

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

TCP/IP

• Uses client/server model of network computing
• Allows wireless devices to access the Internet
  and WWW
• Meets increasing demands for wireless Internet
  access.

WAP
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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 ConfigurationsConnections
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 ConfigurationsMicrocomputer to
Internet

• Very popular with home users.
• Typically a modem is used to connect users
  microcomputer to an Internet Service Provider.
• Newer technologies such as DSL and cable modems
  are replacing modems.

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Computer Network ConfigurationsLAN 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 ConfigurationsLAN 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 ConfigurationsSensor 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 ConfigurationsSatellite 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.

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Why Are Networks Important?

• Enterprise
• Organization
• Department
• Individual

Users

• LANs
• Mans
• WANs

BUSINESS ENTERPRISE
Applications
Network
Internet

• Functions
• Organizational
• Processes
• Personal

• Wired
• Wireless

Information

• Traditional Data
• Text
• Images

• Graphics
• Voice
• Video
• Multi-media

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Networks Pros and Cons
Pros
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

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Key Issues of Networks

• Access 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 companys 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
Client/Server Model
Microcomputer users, or clients, share services
of a centralized computer called a server.
Peer-to-Peer Model
Computers share equally with one another without
having to rely on a central server.
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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
Peer-to-Peer Model
Client/Server Model

• Advantages
• Very secure OS.
• Better performance.
• Centralized servers, easy to manage.
• Centralized backups.
• High reliability.

• 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.

• Disadvantages
• Expensive administration.
• More hardware intensive.

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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
Source The McGraw-Hill Companies, Inc., 1999
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Network Typologies Star
This arrangement connects all the networks
devices to a central host computer, through
which all communications must pass.
Source The McGraw-Hill Companies, Inc., 1999
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Network Typologies Ring
This arrangement connects the networks devices
in a closed loop.
Source The McGraw-Hill Companies, Inc., 1999
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Network Typologies Bus
A single channel connects all communications
devices.
Source The McGraw-Hill Companies, Inc., 1999
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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 distances
• Telecommunications - study of telephones and the
  systems that transmit telephone signals
• Network 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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Requirements of a Network System (2)

• 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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Requirements of a Network System (3)

• Consistency
• Same thing all the time
• Response time

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Requirements of a Network System (4)

• Flexibility
• Growth and change available with minimum impact
  on users
• Legacy systems
• Standards help

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Requirements of a Network System (5)

• Availability
• When needed
• Where available
• How available

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Requirements of a Network System (6)

• Reliability
• Measure of system failure
• MTBF mean time between failure
• Fault-tolerance solution
• Design
• Duplication

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Requirements of a Network System (7)

• Recovery
• All systems fail
• How long before startup?
• What do we get when the system starts up again
• Saved information

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Requirements of a Network System (8)

• 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 vendors
• Standards allow hardware and software from
  different vendors to work together
• Competition 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 IEEE
• OSI - 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 OSIs
  physical and data link layers.
• Network layer - roughly equivalent to the OSIs
  network layer.
• Transport layer - performs same function as OSI
  transport layer.
• Application layer - equivalent to the OSIs
  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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The Internet Model in Action

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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?

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Joining Professional Associations

• Benefits can include
• Connecting with people who have similar interests
• Providing new opportunities for learning
• Allowing access to specialized information
• Giving tangible assets such as free goods

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Professional Association Sites
TABLE 1-2 Web sites of networking
organizations Circa 2000. Some do not exist today!