Introduction

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

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

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

Data Communication Data communication process  to occur Data communication process  to occur hardware  communication devices hardware  communication devices Software  communication software Software  communication software

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

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

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

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

Networks Network Criteria Network Criteria Data communication network criteria ReliabilitySecurityPerformance

Networks Network Criteria Network Criteria Data communication network criteria ReliabilitySecurityPerformance

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

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

Networks Network Criteria Network Criteria Data communication network criteria ReliabilitySecurityPerformance

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

Networks Network Criteria Network Criteria Data communication network criteria ReliabilitySecurityPerformance

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

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

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

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

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

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

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