Introduction Data Communication n n Sharing information Local

Introduction

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

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

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

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

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

Components Step 1 : Step 2: Step 3: …… Protocol Step 1 : Step 2: t Step 3: …… Protocol message medium sender receiver

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

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

Networks n Network Criteria Data communication network criteria Performance Reliability Security

Networks n Network Criteria Data communication network criteria Performance Reliability Security

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

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

Networks n Network Criteria Data communication network criteria Performance Reliability Security

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

Networks n Network Criteria Data communication network criteria Performance Reliability Security

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

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

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

Protocols and Standards n Syntax n n Format of data : i. e. the first 8 bits = sender address the second 8 bits = receiver address the rest = data or message Semantic n n 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

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

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

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