Telecommunications

Chapter 5

InformationSystems

Software

Hardware Telecommunications

Data People

The Components of an Information System

Importance of Telecommunications

• Work Group Communication– E-mail– Video conferencing

• Emerging Business Applications– Electronic Commerce– Electronic Data Interchange (EDI)

• Rapid rate of change in technology

Data Communication

• All communications require three things:– Senders and receivers that have

something to share• Coded by sender• Decoded by receiver

– A pathway or transmission media to send the message

– Rules or protocols of communication

Human vs Computer Communication

Computer Networks• Computers and other devices connected by

a communications channel – Share files and other resources between users

• Channel: the transmission media

• Bandwidth: carrying capacity of the media

• Protocols: the physical and logical rules for transmission

Remaining Topics

• Computing Network Models

• Classes of Computer Networks

• Building Blocks of Computer Networks

Computing Network Models

• Centralized computing – Uses mainframes and “dumb” terminals

• Distributed computing – Uses separate computers

• Collaborative computing– Uses two or more networked computers

• Networks today include all three models

Centralized Computing Model

Distributed Computing Model

Collaborative Computing Model

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks

• Building Blocks of Computer Networks

Classes of Computer Networks

• Private Branch Exchange (PBX)– A privately owned telephone switch

• Local Area Network (LAN)– Usually confined to a single building or site

• Wide Area Network (WAN)– Enterprise network - one organization– Global network

Private Branch Exchange

Local Area Network

Enterprise Network

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks

Building Blocks of Computer Networks

• Servers, Clients, and Peers

• Network Services

• Transmission Media

• Network Topologies

• Network Access Control Methods

• Major Standards

Servers, Clients, and Peers

• Server-centric networks– Server

• A network computer that makes services available to users

– Client• Uses services provided by a server

• Peer-to-peer networks – Allow any computer or device to provide and

request services

Servers, Clients, and Peers

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services– Transmission Media– Network Topologies– Network Access Control Methods– Major Standards

Network Services• Offered by the network operating

system – File services

• Store, retrieve, and move data

– Print services• Control access to printers and fax machines

– Message services• Deal with communication between network

users

– Application services• Run software for network clients

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services– Transmission Media– Network Topologies– Network Access Control Methods– Major Standards

Transmission Media• The physical pathway that carries

signals

• Media characteristics– Bandwidth - transmission capacity stated in

megabits per second (Mbps) – Attenuation - weakening of signal over

distance– EMI - electromagnetic interference

• Two forms– Cable media– Wireless media

Cable Media• Twisted Pair

– Two or more pairs of insulated copper wires

• Coaxial– Inner copper conductor surrounded by plastic

insulation with outer braided foil shield

• Fiber Optic– Uses pulses of light to send data– Glass or plastic core surrounded by cladding with

a tough outer sheath

Wireless Media• Infrared Line of Sight

– Light waves transmit data on unobstructed path

• High-Frequency Radio– Radio signals up to 39.6 meters

• Microwave Line of Sight– Terrestrial uses earth-based antennas – Satellite sends signals between antennas on

earth and orbiting satellites

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services– Transmission Media (Cable, Wireless)– Network Topologies– Network Access Control Methods– Major Standards

Network Topologies• Star Network

– All nodes attached to center a hub– Messages must pass through the hub

• Ring Network– A closed loop– Messages move in one direction

• Bus Network– An open-ended line– Nodes receive message at the same time

Star Network

Ring Network

Bus Network

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services– Transmission Media (Cable, Wireless)– Network Topologies (Star, Ring, Bus)– Network Access Control Methods– Major Standards

Network Access Control Methods

• Distributed Access Control– Token passing

• Circulating electronic token prevents collisions• Must possess the token to transmit a message

• Random Access Control– CSMA/CD

• “Listen” for quiet line; then send message• Collision occurs with simultaneous messages• Must wait and resend

Token Ring Operation

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services– Transmission Media (Cable, Wireless)– Network Topologies (Star, Ring, Bus)– Network Access Control Methods (Distributed—Token

passing, Random)– Major Standards

The OSI Model

The OSI Model andMessage Passing

Network Operating Systems

• Client/server architecture LANs– The system software runs on the file server– Part of the NOS runs on each workstation

• Peer-to-peer networks– NOS is installed on each attached

workstation– Runs on top of the local operating system

• Computing Network Models– Centralized, distributed, collaborative

• Classes of Computer Networks– PBX, LAN, WAN (enterprise & global)

• Building Blocks of Computer Networks– Server-centric/peer-to-peer– Network Services (File, print, message, application)– Transmission Media (Cable, Wireless)– Network Topologies (Star, Ring, Bus)– Network Access Control Methods (Distributed -Token

passing, Random)– Major Standards (The OSI Model)