Data Communication Software- Role and Functions

National conference on Data Communications

Held in CSIO Chandigarh , April 7-8, 2000

Paper and Seminar presented by

Noor Jahan Haque Associate Lecturer

IETE Institute of Electronics & Telecommunication Engineering, Chandigarh

Prepared by

Raman K. Attri (Sr Scientist, CSIO Chandigarh) Noor Jahan Haque (Associate Lecturer, IETE Chandigarh)

Noor JahanHaqueAssociate Lecturer

IETE Institute of Electronics & Telecommunication Engineering, Chandigarh

Prepared byRaman K. Attri (Sr Scientist, CSIO Chandigarh)

Noor Jahan Haque (Associate Lecturer, IETE Chandigarh)

National conference on Data Communicationsheld in CSIO Chandigarh , April 7-8, 2000

Communication SoftwareAreas to be covered

Overview of Data CommunicationRole of Data Communication SoftwareFunctional Aspects of Data Communication Software

Slide I (Areas to be covered) The shifting of communication systems from analog to digital has introduces a new area of data communication. The core of data communication is Communication software which is the topic of my paper today. In this paper I shall cover following areas Areas to be covered • Overview of Data Communication • Role of Data Communication Software • Functional Aspects of Data Communication Software FFiirrsstt ooff aallll II wwiillll ssttaarrtt wwiitthh oovveerrvviieeww ooff DDaattaa CCoommmmuunniiccaattiioonn bbeeffoorree mmoovviinngg ttoo CCoommmmuunniiccaattiioonn ssooffttwwaarree iissssuueess..

Data Communication OverviewTransportation of Information from one point to another through a communication medium

Inherently linked with computers and transmission of data over the network through the communication media

SSlliiddee 22 ((Data communication Overview) WWhhaatt iiss ddaattaa ccoommmmuunniiccaattiioonn?? IItt iiss bbaassiiccaallllyy Transportation of Information from one point to another through a communication medium. This information may be anything fax, letter, e-mail, file or data Data communication is inherently linked with computers and transmission of data over the network through the communication media. The term Data communication is generally used where PC to PC communication over the networks is involved

Evolution of Data Communication

Huge development in PC

+

Network Technologies

SSlliiddee 33 ((EEvvoolluuttiioonn ooff DDaattaa CCoommmmuunniiccaattiioonn)) NNooww wwee ccoommee ttoo bbaassiicc qquueessttiioonn tthhaatt hhooww DDaattaa ccoommmmuunniiccaattiioonn ccaammee iinnttoo ppiiccttuurree?? IItt ccaammee iinnttoo ppiiccttuurree wwiitthh tthhee HHuuggee development in PC market as a result of which we had high performance workstation. The second factor for data communication evolution was the parallel networking technologies getting the fast popularity. The combination of both resulted into Data Communication field.

Advantages of Data CommunicationEfficient use of large computers

improves the monitoring projects

provides various value added services

SSlliiddee 44 ((aaddvvaannttaaggeess ooff DDaattaa CCoommmmuunniiccaattiioonn)) NNooww wwee ccoommee ttoo aaddvvaannttaaggeess ooff DDaattaa CCoommmmuunniiccaattiioonn.. IItt mmaaddee • Efficient use of large computers and its communication facilities were exploited very much. • Further it improves the monitoring projects by scanning the data coming from remote sites or devices. • It also provided various value added services like e-mail, internet, voice mail, video tex, fax, PC-PC communication etc.

Result of Data Communication Technology

information superhighway for free accessibility and communicability for common utilities and services

SSlliiddee 55 ((RReessuulltt ooff DDaattaa CCoommmmuunniiccaattiioonn TTeecchhnnoollooggyy)) Now what was the result or impact of Data Communication Technology? It resulted in creating an Information superhighway for free accessibility and communicability for common utilities and services. These included Internet, e-mail, web pages, e-commerce, home shopping, and online services. Now the whole world relies on data communication. All business and commercial houses depends upon data communication

Components of Data CommunicationData SourceData SinkCommunication MediaControlling Communication Software

Source SinkCommn Media

Communication Software

SSlliiddee 66 ((CCoommppoonneennttss ooff DDaattaa CCoommmmuunniiccaattiioonn)) NNooww II wwiillll eexxppllaaiinn vvaarriioouuss ccoommppoonneennttss ooff DDaattaa CCoommmmuunniiccaattiioonn sseettuupp.. TThheessee ccoommppoonneennttss aarree • Data Source • Data Sink • Communication Media • Controlling Communication Software The communication software is the blood of data communication which holds the life of data communication setup

Data SourceOriginator of InformationIt can be a PC, server, remote terminal, satellite or a machineConvert the data into the format suitable for transmission under the control of communication software

SSlliiddee 77 ((DDaattaa SSoouurrccee)) FFiirrsstt ooff aallll wwee ttaakkee DDaattaa SSoouurrccee.. IItt iiss ssiimmppllyy aann • Originator of Information from where the information is produced. Suppose I have a web server or a machine which

transmit information, it will be called data source. • It can be a PC, server, remote terminal, satellite or a machine • The data source Convert the data into the format suitable for transmission under the control of communication

software. If data is to be transmitted over the telephone lines, it will convert the digital data into analog signal.

Data SinkReceiver of informationIt can be a computer or a terminal connected to sourceReceives the signal, decodes into bits, assembles the group of bits and recreate the originally transmitted information

SSlliiddee 88 ((DDaattaa SSiinnkk)) Sink is the • Receiver of information • It can be a computer or a terminal connected to source The role of sink in the communication is to • Receives the signal, decodes into bits, assembles the group of bits and recreate the originally transmitted information The information generated by source was meant for sink only

Communication MediaGlues the source and sink together for information exchangeIt can be direct cable (in LAN), modem through telephone line (in WAN), satellite,  optical fiber, cellular connection

SSlliiddee 99 ((CCoommmmuunniiccaattiioonn MMeeddiiaa)) TThhee ccoommmmuunniiccaattiioonn mmeeddiiaa • Glues the source and sink together for information exchange • It can be direct cable (in LAN), modem through telephone line (in WAN), satellite, optical fiber, cellular connection The next component of Data communication is the Communication software which controls the overall communication process. It will be discussed in next slides.

Communication InterfaceIn network configuration both source and sink are PC, termed as Data Terminal Equipment  (DTE).Two DTE (Source and Sink ) are connected through an interface termed as Data Communication Equipment DCE can be a modem, Ethernet card or VSAT

SSlliiddee 1100 ((CCoommmmuunniiccaattiioonn IInntteerrffaaccee)) AAnnyy ccoommmmuunniiccaattiioonn ssyysstteemm wwhheenn rreeaalliizzeedd iinn pprraaccttiiccaall ffoorrmm wwiillll rreeqquuiirree aa iinntteerrffaaccee tthhrroouugghh wwhhiicchh ssoouurrccee aanndd ssiinnkk ccaann bbee ccoonnnneecctteedd.. SSoouurrccee aanndd SSiinnkk aarree ggeenneerraallllyy aarree PPCC TThheessee ccoommmmuunniiccaattiinngg PPCC aarree ccaalllleedd DDaattaa tteerrmmiinnaall EEqquuiippmmeenntt ((DDTTEE)) • Two DTE (Source and Sink ) are connected through an interface termed as Data Communication Equipment • DCE can be a modem, Ethernet card or VSAT • DCE Converts Digital Data from DTE into a signal suitable for transmission & vice versa - Conversion from Digital to Analog & vice versa in modem - Parallel to serial & vice versa in LAN Networks) DDCCEE iiss aa mmuusstt ffoorr ccoommmmuunniiccaattiinngg PPCC

DataSourceDTE

Data SinkDTE

DCE DCE

PC

Communication Media

Modem/VSAT/Ethernet Card PC

CommunicationSoftware(Transmitter)

CommunicationSoftware (Receiver)

SSlliiddee 1111 ((PPiiccttuurree)) TThhee sslliiddee sshhoowwss tthhee DDTTEE aanndd DDCCEE.. TThhee ssooffttwwaarree ccoonnttrroollss tthhee iinntteerrffaaccee ooff DDTTEE wwiitthh DDCCEE.. TThheenn DDCCEE ttrraannssmmiitt oorr rreecceeiivvee ddaattaa oovveerr tthhee ccoommmmuunniiccaattiioonn mmeeddiiaa..

Conversion of Data into Signal

DCE Converts Digital Data from DTE into a signal suitable for transmission & vice versa ‐ conversion from Digital to Analog & 

vice versa in modem‐ Parallel to serial & vice versa in LAN 

Networks)

SSlliiddee 1122 ((CCoonnvveerrssiioonn)) MMaaiinn ffuunnccttiioonn ooff DDCCEE iiss ddaattaa ccoonnvveerrssiioonn ssuuiittaabbllee ffoorr ttrraannssmmiissssiioonn

DCE and Communication SoftwareDCE works in close association with Communication Software at DTE to perform the sophisticated functions:‐efficient data flow between the two endsEstablishment of the physical connection between the two end pointsTransmission and receipt of all digital information through the physical circuitConversion form Digital to analog and vice versaError Detection and correctionMonitoring and Diagnosing of equipment faults

SSlliiddee 1133 ((DDCCEE aanndd CCoommmmuunniiccaattiioonn SSooffttwwaarree)) As I have told before that DCE is must for communicating PCs.

DCE works in close association with Communication Software at DTE to perform the sophisticated functions:- • efficient data flow between the two ends (PC to PC) • Establishment of the physical connection between the two end points • Transmission and receipt of all digital information through the physical circuit • Conversion form Digital to analog and vice versa (in case of modem) • Error Detection and correction (The errors may get introduced in communication media) • Monitoring and Diagnosing of equipment faults

Data Communication SoftwareIt is a computer program required on DTE (PC) to bridge the gap and interpret the bits/bytes that are transmitted via the communication media through the interfaceCore of Data Communication is Communication SoftwareResponsible for controlling data formatting, data transmission, and total communication controlMay completely resides on central PC or part of it may be located on the front end communication PC, a concentrator, remote concentrator or in intelligent terminals

SSlliiddee 1144 ((DDaattaa CCoommmmuunniiccaattiioonn SSooffttwwaarree)) Now we come to understanding what the Data communication Software is and what are its various features. We will also discuss other issues related with the Data Communication Software. Data communication Software is basically a computer program • It is a computer program required on DTE (PC) to bridge the gap and interpret the bits/bytes that are transmitted via

the communication media through the interface It is • Core of Data Communication is Communication Software Without software, Data communication is incomplete. Further Communication Software is • Responsible for controlling data formatting, data transmission, and total communication control Now where this communication software is located? It • May completely resides on central PC or part of it may be located on the front end communication PC, a concentrator,

remote concentrator or in intelligent terminals

Significance of Data Communication Software

Defines the communication parameters

Controls the user accessibility to information

optimal configuration of communication hardware

effective utilization of network resources

SSlliiddee 1155 ((SSiiggnniiffiiccaannccee ooff DDaattaa CCoommmmuunniiccaattiioonn SSooffttwwaarree)) NNooww yyoouu wwiillll aasskk wwhhaatt tthhee ssiiggnniiffiiccaannccee ooff tthhiiss CCoommmmuunniiccaattiioonn SSooffttwwaarree iiss.. IItt bbaassiiccaallllyy • Defines the communication parameters like communication speed, error rate, bandwidth, protocols, etc. • Controls the user accessibility to information. It means how a user can access the information and how information shall

be presented to user. It controls the • optimal configuration of communication hardware and make the • effective utilization of network resources

Functions of Communication SoftwareTransmission initiation and terminationEstablishment of logical connections over physical lineMessage Assembly and De‐assemblyData Transmission & receiptCode conversionError DetectionData EditingControl Character RecognitionData Delivery and outputTransmission monitoring and maintenance

SSlliiddee 1166 ((FFuunnccttiioonnss ooff CCoommmmuunniiccaattiioonn SSooffttwwaarree)) IInn aannyy ddaattaa ccoommmmuunniiccaattiioonn ssyysstteemm,, ccoommmmuunniiccaattiioonn ssooffttwwaarree hhaass vveerryy iimmppoorrttaanntt ttaasskkss ttoo ddoo.. TThheessee ttaasskkss iinncclluuddee:: • Transmission initiation and termination is done by communication software when user prompts it. In case of modem,

modem initialization and making it ready function come under this category • Establishment of logical connections over physical line like dialing the number on phone lines • Message Assembly and De-assembly • Data Transmission & receipt. It means Modulation of digital data into analog and vice versa by modem) • Code conversion is done by communication software where it format the data • Error Detection is also done by it. It checks for lost bits and other error introduced while transmitting • Data Editing • Control Character Recognition • Data Delivery and output. Communication software control the output and delivery of data at the destination) • Transmission monitoring and maintenance

Multi‐dimensional study is involved in the design of communication softwareThe design depends upon equipment DTE     ( terminal controller, concentrator, switch  or host PC) that would be connected.Characteristics of communication media with respect to probability of error and its remedy measuresComplexity of Software depends upon the complexity of networks

Communication Software Design Consideration

SSlliiddee 1177 ((CCoommmmuunniiccaattiioonn SSooffttwwaarree DDeessiiggnn CCoonnssiiddeerraattiioonn)) NNooww wwee ccoommee ttoo ddeessiiggnn ccoonnssiiddeerraattiioonn ooff CCoommmmuunniiccaattiioonn ssooffttwwaarree.. LLiikkee ootthheerr ssooffttwwaarree ddeevveellooppmmeenntt iitt hhaass ttoo uunnddeerrggoo ssoommee sseett ooff rruulleess.. BBeessiiddee ggeenneerraall rruulleess ssoommee ssppeecciiaall rreeqquuiirreemmeennttss ooff ccoommmmuunniiccaattiioonn ssooffttwwaarree aallssoo ttoo bbee oobbsseerrvveedd.. • Software Design to be based on principles of modularity, hierarchy and generality • Design of communication software is done in form of layers, each layer having different functions

Communication Software design follows a standard approach having set of procedures or rules called protocols

Multi‐dimensional study is involved in the design of communication softwareThe design depends upon equipment DTE     ( terminal controller, concentrator, switch  or host PC) that would be connected.Characteristics of communication media with respect to probability of error and its remedy measuresComplexity of Software depends upon the complexity of networks

Communication Software Design Consideration

SSlliiddee 1188 ((DDeessiiggnn CCoonnssiiddeerraattiioonnss ccoonnttdd……..)) • Multi-dimensional study is involved in the design of communication software • The design depends upon equipment DTE (terminal controller, concentrator, switch or host PC) that would be

connected. In case of modem software design will be different and in case of Ethernet card the design will be different.

Further the design of communication software is also dependent upon the • Characteristics of communication media with respect to probability of error and its remedy measures • Complexity of Software depends upon the complexity of networks

Data Communication ProtocolsProtocols are the set of rules or the procedure which are followed by communicating devices while exchanging the data (example telephone conversation)Protocols provide the standardization and flexible interconnection of communication among different platforms and different kinds of PCs

SSlliiddee 1199 ((DDaattaa CCoommmmuunniiccaattiioonn PPrroottooccoollss)) TThhee ccoorree ooff aannyy ddaattaa ccoommmmuunniiccaattiioonn ssooffttwwaarree iiss tthhee tteerrmm pprroottooccooll.. • Protocols are the set of rules or the procedure which is followed by communicating devices while exchanging the data

(example telephone conversation).Just as in telephone when one dials a number ring is tuned on. If operator is available he will pick the receiver and acknowledge by saying hello. After conversation, call is terminated by putting down the receiver. Similar thing happens when two PC communicate together

• Protocols provide the standardization and flexible interconnection of communication among different platforms and different kinds of PCs. This is how we can now communicate worldwide over the PC of any brand or vendor. It is due to standardization of protocols

Data Communication Protocols InternalsData Communication Protocols can be either Bit Oriented  or Byte oriented‐ Bit oriented protocol transmit data in 

batches of any length upto specified number

‐ Byte oriented protocol transmit data in 8  bit blocks

SSlliiddee 2200 ((DDaattaa CCoommmmuunniiccaattiioonn PPrroottooccoollss IInntteerrnnaallss)) Data Communication Protocols can be either Bit Oriented or Byte oriented - Bit oriented protocol transmit data in batches of any length upto specified number - Byte oriented protocol transmit data in 8 bit blocks

Role of Layering in Protocol Design Protocol is a Collection of Rules for physical establishment of calls, identification, transmission of data, acknowledge‐ment & termination Protocol is meant For universal standardization of information exchange over the PC from different vendors, platforms and network configurationProtocol is designed in forms of layer. Each layer is a specific piece of software following some pre‐defined rules of functioning.

SSlliiddee 2211 ((RRoollee ooff llaayyeerriinngg iinn CCoommmmuunniiccaattiioonn PPrroottooccoollss)) LLaayyeerriinngg iiss vveerryy iimmppoorrttaanntt ppaarrtt ooff CCoommmmuunniiccaattiioonn ssooffttwwaarree.. • Protocol is a Collection of Rules for physical establishment of calls, identification, transmission of data,

acknowledgement & termination • Protocol is meant For universal standardization of information exchange over the PC from different vendors, platforms

and network configuration • Protocol is designed in forms of layer. Each layer is a specific piece of software following some pre-defined rules of

functioning.

Unique  functions or process are designated to different layers in a communication protocol and layers in conjunction provide the efficient communication.Layers of Data communication software ensure that the data is physically transmitted & user receives it with no errorsOSI model based on seven layers enable development of a standard that would facilitate a flexible interconnection of systems using data communication facilities

Role of Layering in Protocol Design 

SSlliiddee 2222 ((RRoollee ooff llaayyeerriinngg ccoonnttdd……)) • Unique functions or process are designated to different layers in a communication protocol and layers in conjunction

provide the efficient communication. Now what are the advantages of layers? • Layers of Data communication software ensure that the data is physically transmitted & user receives it with no errors We have many models for communication software. OSI model is very famous • OSI model based on seven layers enable development of a standard that would facilitate a flexible interconnection of

systems using data communication facilities

OSI layers of Communication ProtocolPhysical layer (interconnection through physical media)Data link layer (control error free transmission over physical 

layer)Network layer (control efficient routing and paths in the 

network)Transport layer (control data transportability from system to 

system)Session layer (control dialog communication session) Presentation layer (control representation &manipulation of 

data)Application layer (control user interface )

SSlliiddee 2233 ((OOSSII llaayyeerrss ooff CCoommmmuunniiccaattiioonn SSooffttwwaarree)) Here I will discuss just the overview of functional aspect of OSI layers. The communication software pieces are developed and designed around these functionality. The seven layers in OSI perform different control functions. This feature provide the modularity in the software and debugging and diagnosis of communication systems

• Physical layer (interconnection through physical media)

• Data link layer (control error free transmission over physical layer)

• Network layer (control efficient routing and paths in the network)

• Transport layer (control data transportability from system to system)

• Session layer (control dialog communication session)

• Presentation layer (control representation &manipulation of data)

• Application layer (control user interface )

Data Transmission ErrorData while being transmitted may suffer damage, error due to the characteristics of the transmission medium or due to external disturbancesAlmost all the Communication channels are very error prone to less or more extentEven if a bit is erroneous, the whole of the character is lostQuality of communication channel is measured by percentage of characters transmitted correctly

SSlliiddee 2244 ((DDaattaa TTrraannssmmiissssiioonn EErrrroorr)) NNooww wwee ccoommee ttoo vveerryy iimmppoorrttaanntt aassppeecctt ooff DDaattaa ccoommmmuunniiccaattiioonn ssooffttwwaarree wwhhiicchh iiss DDaattaa ttrraannssmmiissssiioonn eerrrroorr aanndd hhooww ccoommmmuunniiccaattiioonn ssooffttwwaarree hheellppss ttoo rreedduuccee tthhiiss eerrrroorr • Data while being transmitted may suffer damage, error due to the characteristics of the transmission medium or due to

external disturbances • Almost all the Communication channels are very error prone to less or more extent What kind of error is introduced? It is generally reception of '1' bit which was transmitted as'0'. Now the question arises, how severe this small error can be. • Even if a bit is erroneous, the whole of the character is lost • Quality of communication channel is measured by percentage of characters transmitted correctly

Data Error Recovery through DCSRecovery methods are must for efficient data communication Protocol technique ensure that information is transmitted only and only when communication channel is free and the appropriate terminal devices are ready to receiveCommunication software include the method of capturing the error at initial level and request transmitter to retransmit the lost bitCommunication Software include the error detection and correction algorithms

SSlliiddee 2255 ((DDaattaa EErrrroorr RReeccoovveerryy tthhrroouugghh DDCCSS)) NNooww iitt iiss tthhee rreessppoonnssiibbiilliittyy ooff ccoommmmuunniiccaattiioonn ssooffttwwaarree ttoo pprreevveenntt oorr ddeetteecctt tthhiiss eerrrroorr.. • Recovery methods are must for efficient data communication The error is prevented by the proper use of protocols. How protocol help to prevent errors • Protocol technique ensure that information is transmitted only and only when communication channel is free and the

appropriate terminal devices are ready to receive Inspite of much careful design of protocols, error gets introduced due to communication media as well. This introduced error is detected before assembling the transmitted bits • Communication software include the method of capturing the error at initial level and request transmitter to retransmit

the lost bit •• Communication Software include the error detection and correction algorithms. Wide variety of algorithm are available

in theory as well practice

About the author

Noor Jahan Haque earned her Masters in Information technology in 1999. She served at IETE as associate faculty from 2000‐2001. She is also Director of JAAN Netlink Inc India since 2000. neeruhaque2000@yahoo.com

Raman K. Attri, Masters in Technology (Applied Electronics) served as senior scientist at CSIO Chandigarh from 1995‐2005. His specialization is in Instrumentation systems. rkattri@rediffmail.com