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Introduction

Introduction. Data Communication. Communication Sharing information : Local & Remote Local Face to face, between individuals Remote Over distance Requires “telecommunication” media/method Telephony Telegraphy Television

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Introduction

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  1. Introduction

  2. Data Communication • Communication • Sharing information : Local & Remote • Local • Face to face, between individuals • Remote • Over distance • Requires “telecommunication” media/method • Telephony • Telegraphy • Television • Telecommunication = communication at distance (tele = far (Greek))

  3. Data Communication • Data refers to • Facts • Concepts • Instructions • Presented in any form agreed upon by the parties creating and using the data • In computer information system • Data are represented by 0/1

  4. Data Communication In summary • Data communication = the exchange of data (0s/1s) between two devices via some form of transmission media (i.e. cable) • Local communication • Devices are in the same building • Remote communication • Devices are far apart

  5. Data Communication • Data communication process  to occur • hardware  communication devices • Software  communication software

  6. Data Communication • Three fundamental characteristics (provide data communication system effectiveness) • Delivery (to the right party) • Accuracy (0  0 / 1  1 NOT 0  1 ) • Timeliness

  7. Components Step1 : Step2: Step3: …… t Step1 : Step2: Step3: …… Protocol Protocol message medium sender receiver

  8. Components • Messages • Data to be communicated • Any form (text, pictures, sound, video, etc.) • Sender/Receiver • Device that sends/receives the data message • It can be : computer, telephone, etc. • Medium • Twisted pair wire, coaxial cable, etc. • Protocol : Rules.

  9. Networks • A set of devices (node) connected by media links • A node can be • Computer • Printer • Any other devices capable of sending and receiving data • The link is often called “communication channel” • Uses “Distributed Processing”

  10. Networks • Network Criteria Data communication network criteria Performance Reliability Security

  11. Networks • Network Criteria Data communication network criteria Performance Reliability Security

  12. Network Criteria • Performance measures • Transit time • Traveling time from one device to another • Response time • Time between an inquiry and a response

  13. Network Criteria : Performance • Important Factors (for performance) • Number of users • Type of transmission medium • Hardware • Software

  14. Networks • Network Criteria Data communication network criteria Performance Reliability Security

  15. Network Criteria • Reliability : measured by • Frequency of failures • Recovery time of a network after failure • Protected from unforeseen damage • Fire • Flood • etc.

  16. Networks • Network Criteria Data communication network criteria Performance Reliability Security

  17. Network Criteria • Security : Protecting data from unauthorised access and viruses • Unauthorised access • Password • Encryption • Viruses • A good network must be protected from viruses by hardware and software

  18. Applications • Marketing and sales • Financial services • Manufacturing • Electronic messaging • Directory services • Information services • Electronic data interchange (EDI) • Teleconferencing • Cellular telephone • Cable television

  19. Protocols and Standards • Protocols • A set of rules that govern data communication • Defines • What is communicated • How it is communicated • When it is communicated • Key elements of a protocol • Syntax • Semantics • timing

  20. Protocols and Standards • Syntax • Format of data : i.e. the first 8 bits = sender address the second 8 bits = receiver address the rest = data or message • Semantic • Meaning of each section of bits • How is a pattern to be interpreted • What action is to be taken • i.e.  does the address identify the route to be taken or the final destination of the message

  21. Protocols and Standards • Timing • When data should be sent • How fast they can be sent • For example : • Sender produces 100 Mbps  sender can receive 1 Mbps • Overload the receiver • Data lost

  22. Standards • Facts: • Devices from different manufacturers • Different signal/methods/data • Standards are necessary • Data communication standards • de facto (by fact or by convention) • de jure (by law or by regulation)

  23. Standards organisations • Standards creation committee • ISO • CCITT • ANSI • IEEE • EIA • Forums • Frame Relay Forum • ATM Forum and ATM Consortium • ISOC and IETF

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