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Data 

Data Communications

 Communications

 

and  

and  NetworkingNetworking

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Overview

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Data Communication

Exchan e of data between two

devices via some form of transmission

Data Representation

Direction of Data Flow

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Data Communication

he effectiveness of the data

communication system depends on

1. Delivery.3. Timeliness

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Five components of  data communication

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ComponentsMessageInformation to be communicated

Sender 

ReceiverDevice that receives the messa e

MediumPhysical path by which a message travels from

sender to receiver.Protocol

.

represents an agreement between the communicatingdevices

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Data Representation

 ASCII 

Unicode

Numbers

Images

 Video

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Direction of Data Flow

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Half ‐duplex 

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Full ‐duplex 

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Networks

 

Network Criteria

Physical Structures

Cate ories of Networks

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Distributed Processing

•  computers. responsible for all aspects of  a process, each 

.

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Advantages

•

• Distributed databases

• Faster pro em so ving

• Security through redundancy• Collaborative processing

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Network Criteria• To be considered effective and efficient, a network must meet the 

 –  Performance• Can be measured in many ways

 –  Transit time

» Amount of  time required for a message to travel from one device to another

» Elapsed time between an inquiry and a response.

 –  Response time

• Depends on the following –    –  Type of  transmission medium

 –  Hardware  –  Software

 –  Reliabilit

• Measured by frequency of  failure• Time taken by the link to recover from a failure

• Catastrophe

 – • Unauthorized access

• Viruses

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Physical structures

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Types of Connection

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Point ‐to‐ point  connection

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Multipoint  connection

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Types of physical topology

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Categories of  topology 

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Fully  connected  mesh topology  (for   five devices)

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Star  topology 

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Bus topology 

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Ring topology 

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Categories of  networks

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LAN

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LAN (Continued)

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MAN

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WAN

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TheThe InternetInternet

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Internet  today 

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ProtocolsProtocols

• Set of  rules that govern data communication

• Defines what is communicated, how it is communicated, and when it is communicated.  – Syntax

• Structure or

 the

 format

 of 

 the

 data

 meaning

 the

 order

 in

 which

  – Semantics 

• Meaning of  each section of  bits

•   – Timing

• When the data should be sent and how fast they can be sent.

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Protocol StandardsProtocol Standards

• Provides a model for development that makes it individual manufacturer

•   – De  jure (By Law)

• That have been legislated by an officially recognized body – De Facto (By Fact)

• Proprietary

 –    – Closed standards

• Non Proprietary

 –    – Open Standards