Ch5

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24 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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Telecommunications

Chapter 5

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 and

Message 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)