Data communication and network Chapter -1


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Data communication and network
Compile by Zafar Ayub

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Data communication and network Chapter -1

  1. 1. ( Copyright revised for Zafar Ayub DATA COMMUNICATION AND NETWORK CHAPTER - 11 Compile by Zafar Ayub
  2. 2. WHAT IS DATA COMMUNICATION? Electronic transmission of information that has been encoded digitally with some standard from one network (systems) to other network (systems) via certain medium, knows as Data Communication. Elements of Data Communication; ( Copyright revised for Zafar Ayub  Information / Data  Digital encoded  Transfer of data / sender and receiver  Specific medium 2
  3. 3. WHAT IS NETWORK? A computer network often simply referred to as a network, is a collection of hardware components, which are interconnected by communication channels that allow sharing of resources and information with respect to certain set of rules / protocols via OS / software. ( Copyright revised for Zafar Ayub Elements of Network;  Hardware equipments  Network OS / software  Communication channel  Information / Data / Recourse  Protocols 3
  4. 4. TERMINOLOGIES Data transmission process between sender and receiver is refer to data communication, and deployed physical environment (hardware / software / protocols / channel ) is network. ( Copyright revised for Zafar Ayub Data: digital information over computer / network, which may define with certain type of file extension; like .doc, .ppt, .pdf, .exe, and etc. File extension dominate nature of data file 4
  5. 5. Resource: all sharable / accessible items over network, whichmay physical / virtual, knows as resource.physical resource - may be hard drive, printer, servers andetc.virtual resource - may be data files, online application, website, internet and etc. ( Copyright revised for Zafar AyubShare Resource: a shared resource or network share is adevice / piece of information means file / software orapplication, on a computer that can be remotely accessedfrom another computer. 5
  6. 6. Channel: communication channel is a medium on whichresource can be access over network and establishconnectivity between sender and receiver. Channel speed /network speed is depends upon bandwidth.bandwidth - channel capacity known as bandwidth.There are two types of channels; ( Copyright revised for Zafar Ayub physical channel like; network cable, fiber optic, electrical wire, and etc. logical or virtual channel like; wireless, radio frequency, Wi-Fi, Wi-Max, and Bluetooth 6
  7. 7. Protocols: a communications protocol is a system of digitalmessage formats and rules for exchanging those messages inor between computer systems and in network /telecommunications.Protocols regulate the following characteristics of a network:access method, allowed physical topologies, types of cabling,and speed of data transfer. ( Copyright revised for Zafar AyubProtocols may include signaling, authentication, errordetection method, and network policies.A protocol can be implement at hardware or software or both,and with respect to assignment these are implemented like;for web http, for security SSL, for email POP3 / SMTP, for LANnetwork Ethernet, for routing BGP / RIP, etc. 7
  8. 8. Digital Encryption: in encryption is the process of transforminginformation / data using an algorithm to make it unreadable toanyone (except those possessing special knowledge, usuallyreferred to as a key).The result of the process is encrypted information and thereverse process, i.e. to make the encrypted informationreadable again is referred to as decryption. ( Copyright revised for Zafar Ayubalgorithm – set of steps for assembling / reassembling of datawith respect to define network technology.Types of digital encryption;Software Based Encryption – a software program to facilitateencryption process on data / file with respect to 256-bit AES /448-bit Blowfish algorithms. Hardware is only responsible todeliver encrypted file to other end computer where again viasoftware program file may be decrypt for original data / file. 8
  9. 9. Drawbacksall encryption perform on data / file during file / file size is also increase with addition of risk for confidentiality documents.Hardware Based Encryption – all data intensive encryptiontasks are done onboard storage device, rather than on file, by ( Copyright revised for Zafar Ayubthis file size remain standard with maximum speed. Mostimportant factor is hardware security protocols which are onlyconfigure same end deviceHardware encryption is also apply with specialize networkequipment.Drawbackshigher cost of equipments 9
  10. 10. Network Hardware: all equipments / devices which may usedon network and facilitate for resource sharing and dataconnectivity like; router, switch, firewall, and servers etc.Network Software: specialize software / OS which mayestablish logical connectivity, authentication, and managementof network, commonly built-in with operating system. Someare like; teamviewer, skype, etc ( Copyright revised for Zafar Ayub 10
  11. 11. Sender: a computer / device from which data / files are sendto specific destination.Receiver a computer / device at which data / files are receivedby source. ( Copyright revised for Zafar Ayub 11
  12. 12. DATA TRANSMISSION Data transmission is the physical transfer of data over a point- to-point or point-to-multipoint channel. Data transmission is a subset of the field of data communications, which also includes computer networking or computer communication applications and networking ( Copyright revised for Zafar Ayub protocols, for example routing and switching. Point – to –point : In telecommunications a point-to-point connection refers to a communications connection between two nodes or endpoints. Point – to –multipoint : refers to communication which is accomplished via a specific and distinct type of one-to-many connection 12
  13. 13. DATA COMMUNICATION TECHNIQUESSerial Transmission - is the process of sending data one bit at atime, in sequentially, over a communication channel / computerbus. A data channel that transfers digital data in a serial mode,one bit after the other over one wire, with start and stop bit. ( Copyright revised for Zafar AyubSerial interfaces may have multiple lines, but only one line isused for data. On earlier PCs, the serial port was a serialinterface for attaching modems and data acquisition terminals,and sometimes mouse. 13
  14. 14. Parallel Transmission - is a method of sending several datasignals simultaneously over several parallel channels.In parallel transmission, multiple bits (usually 8 bits or abyte/character) are sent simultaneously on different channels(wires, frequency channels) within the same cable, or radiopath, and synchronized to a clock. Due to multi channels lines in ( Copyright revised for Zafar Ayubparallel transmission, it may comparatively fast as serialtransmission. 14
  15. 15. Transmission Characteristic - The advantages, limitations andtypical applications of parallel and serial transmissionmethodologies are summarized in chart; Transmission Serial Parallel Characteristic ( Copyright revised for Zafar Ayub Transmission One bit comes after another, one by All bits in a single character and description one transmit simultaneously Comparative Speed Slower Faster Distance Limitation Farther Shorter Application Between two computer, from Within a computer the along computer to external devices, and computer buses, between drive local and wide network controller to hard drive Cable Description All bits travel down in single wire, Each bit travel down its own wire one bit at one time simultaneously with other bits 15
  16. 16. DATA COMMUNICATION CHANNELSThere are three data communication channels like;Simplex communication- refers to communication that occurs inone direction only. Examples radio broadcast, keyboard / mouseinputs to CPU, internet multicast, and one – lane and one sideroad only. ( Copyright revised for Zafar AyubHalf duplex communication - system provides communication inboth directions, but only one direction at a time (notsimultaneously). Typically, once a party begins receiving asignal, it must wait for the transmitter to stop transmitting, beforereplying. Examples walkie-talkie, one-lane road with trafficcontrollers at each end. 16
  17. 17. Full duplex communication- sometimes called double-duplexsystem allows communication in both directions simultaneously.Virtually no collisions take place on a full-duplex transmission.Perhaps a bigger benefit is the increase in overall throughput-since we are sending and receiving on two differentchannels, we just theoretically doubled our data transfer rate.Examples landline / mobile phone, two way double side road. ( Copyright revised for Zafar Ayub 17
  18. 18. DATA COMMUNICATION MODESData communication modes define behavior of data flow duringcommunication which is based on interval of time.When devices are communicating, they must be know whenever data has to send or receive (in period of time). The two ( Copyright revised for Zafar Ayubdevices must establish and maintain some type of timingbetween them so that signals are produced, transmitted, anddetected accurately.There are two main alternatives to establishing and maintainingthe timing for the sampling of the signals. These two timingalternatives are known as asynchronous and synchronous, alsoknown as data communication modes.Data Link Layer : all synchronization occurs on the data linklayer (2nd layer of TCP/IP), where the data in form of frame. 18
  19. 19. Asynchronous communication- The transmission of data inwhich each character is a self-contained unit with its own startand stop bits. Intervals between characters may be irregular. ( Copyright revised for Zafar Ayub 19
  20. 20.  Start bit inform that transmission has to start with binary valueof “0”. Stop bit inform to equipment that transmission has been stopwith binary value of “1”. When no character is being transmitted, the line betweentransmitter and receiver is in an idle state (binary 1 level). A minimum length for the stop element is specified, and this is ( Copyright revised for Zafar Ayubusually 1, 1.5, or 2 times the duration of an ordinary bit. Data contain may be 5 -8 character bits.Parity bit : Character bit may include parity bit, set by thetransmitter such that the total number of ones in thecharacter, including the parity bit, is even (even parity) or odd(odd parity). The receiver uses this bit for error detection. 20
  21. 21.  There are two types of parity bit even parity bit odd parity bitEven parity bit - when using even parity, the parity bit is set to 1 ifthe number of ones in a given set of bits (not including the paritybit) is odd, making the number of ones in the entire set of bits(including the parity bit) even. If the number of ones in a given ( Copyright revised for Zafar Ayubset of bits is already even, it is set to a 0. an even parity bit will be set to "1" if the number of 1s + 1 is evenOdd parity bit - when using odd parity, the parity bit is set to 1 ifthe number of ones in a given set of bits (not including the paritybit) is even, keeping the number of ones in the entire set of bits(including the parity bit) odd. And when the number of set bits isalready odd, the odd parity bit is set to 0. an odd parity bit will be set to "1" if the number of 1s +1 is odd 21
  22. 22.  at end of transmission no maximum value isspecified, because the stop element is the same as the idlestate, the transmitter will continue to transmit the stop elementuntil it is ready to send the next character.Synchronous communication- The transmission of data in blockset and time intervals between characters may be regular. ( Copyright revised for Zafar Ayub each block of data is formatted as a frame that includes astarting and an ending flag, and is transmitted in a steady streamwithout start and stop codes.Clock speed : time interval (clock speed) must besynchronized, to prevent timing drift between transmitter andreceiver; can use separate clock line embed clock signal in data 22
  23. 23. By adding clock line – add specific time of break between senderand receiver.By adding clock signal – add clock information in frame. In synchronous transmission, there is another level ofsynchronization required, to allow the receiver to determine thebeginning and end of a block of data. ( Copyright revised for Zafar Ayub each block begins with a preamble bit pattern (opening flag)and generally ends with a post-amble bit pattern (closing flag). 23
  24. 24. preamble bit – The preamble is a 64-bit (8 byte) field thatcontains a synchronization pattern consisting of alternating onesand zeros and ending with two consecutive ones. Aftersynchronization is established, the preamble is used to locatethe first bit of the packet. The preamble is generated by the LANinterface card. ( Copyright revised for Zafar Ayubpost-amble bit – commonly used end of synchronoustransmission.Control bit : start control bit contain destination MAC, sourceMAC, and protocol; and similar stop control bit contain CRCinformation. 24
  25. 25. Comparison - some comparison between asynchronouscommunication and Synchronous communication as follow; Characteristic Asynchronous Synchronous ( Copyright revised for Zafar Ayub Transmission techniques Used serial communication Used parallel communication Comparative capacity Data transmit one character at Data transmit block (bunch of one time character) at one time Distance limitation Farther (long) Shorter Sync method Start and stop bit Clock speed Comparative speed Low speed due to serial More efficient due to parallel transmission transmission Costing Simple and cheap Much cost due to mechanism Bandwidth loss 20% to 30% over capacity 5% over capacity 25
  26. 26. DATA COMMUNICATION PORTSFor interconnection with other device every data communicationdevice have specific port / interface, by data communicationmechanism two types of ports are available;Serial port- a serial port is a serial communication physical ( Copyright revised for Zafar Ayubinterface through which information transfers in or out one bit ata time.Serial port available in DB-9, DB-25 and Mini Din-8 (appleformat);DB-9 DB-25 Mini Din-8male male malefemale female female 26
  27. 27. DB- 9 – DB-9 also known as RS-422, pin configuration asfollows; ( Copyright revised for Zafar AyubDB- 25 – DB -25 also know as RS-232, pin configuration asfollows; 27
  28. 28. Mini Din -8 – Din-8 also known as RS-422, pin configuration asfollows; ( Copyright revised for Zafar AyubNote : serial port commonly used in old mouse port, game controller,modem port and some old printers. 28
  29. 29. Parallel port- a parallel port is a parallel communication physicalinterface. It is also known as a printer port or centronics port.Parallel port is standard of IBM known as (DB-25) 25-pincombinations. Some available speed of parallel ports;oBi-directional – 150 KbpsoEPP – 1.5 Mbps ( Copyright revised for Zafar AyuboECP – 2.5 MbpsoEPP PCI – 4.5 MbpsBefore the advent of USB, the parallel interface was adapted toaccess a number of peripheral devices other than printers. Listare bellow here;Hardware dongles, Zip drives, Scanners, Webcam, Externalmodem, Sound card, External HDD and CD Rom 29
  30. 30. DB- 25 – DB-25 standard of IEEE 1284 as printer port; ( Copyright revised for Zafar AyubCentronics – port with 36-pins interface; 30
  31. 31. USB - Universal Serial Bus is also serial port with high speeddata flow.USB 1.0 with speed of 1.5 MbpsUSB 1.1 with speed of 12 MbpsUSB 2.0 with speed of 480 MbpsUSB 3.0 with speed of 5 Gbps (Super Speed) ( Copyright revised for Zafar Ayub USB 1 USB 2 USB 3 31
  32. 32. USB - Data Transfer Rate Comparison USB Revision USB1.0 USB2.0 USB3.0Media (Data Size) Transfer Time ( Copyright revised for Zafar AyubSong / Pic (4 MB) 5.3 sec 0.1 sec 0.01 sec256 Flash (256 MB) 5.7 min 8.5 sec 0.8 secUSB Flash (1 GB) 22 min 33 sec 3.3 sec SD-Movie (6 GB) 2.2 hr 3.3 min 20 secUSB Flash (16 GB) 5.9 hr 8.9 min 53.3 secHD-Movie (25GB) 9.3 hr 13.9 min 70 sec 32
  33. 33. SIGNALS AND SYSTEMA signal is an electric current or electromagnetic field used toconvey data from one place to another.The simplest form of signal is a direct current (DC) that isswitched on and off; this is the principle by which the early ( Copyright revised for Zafar Ayubtelegraph worked. More complex signals consist of analternating-current (AC) or electromagnetic carrier that containsone or more data streams.Data is superimposed on a carrier current or wave by means ofa process called modulation. Signal modulation can be done ineither of two main ways: analog and digital.Note : In recent years, digital modulation has been getting morecommon, while analog modulation methods have been used lessand less. There are still plenty of analog signals 33around, however, and they will probably never become totallyextinct.
  34. 34. There are three data transmissions core aspect;Data – Actual information being sent / received, possibly Analog(continuous) or digital (discrete).Analog Data – Takes on continuous values. Ex. Voice or videoDigital Data – Takes on discrete values. Ex. Text and integers ( Copyright revised for Zafar AyubSignal - Electronic or electromagnetic representation ofdata, possibly Analog or digital.Analog Signal – Continuously varying electromagnetic waverepresenting data carried over a variety of medium.Digital Signal – Sequence of voltage pulses representing datatransmitted over a wire mediumTransmission – Communication of data by sending /receiving, and processing data.Analog Transmission – Communication of analog signalsDigital Transmission – Communication of digital signals 34
  35. 35. Analog Signals - An analog signal is any continuous signals forwhich the time is variable of the signal. ( Copyright revised for Zafar AyubDigital Signals - A digital signal is a physical signal that is arepresentation of a sequence of discrete values. 35
  36. 36. Comparison - some comparison between analog and digitalsignals as follow; Characteristic Analog Digital Number of range Analog signals can have an Digital signals can have only a infinite number of values in a limited number of values (1 / 0) ( Copyright revised for Zafar Ayub range Type of data Continuous Discrete Value of data More exact values, but more Not as exact as analog, but difficult to work with easier to work with Wave types Sing waves Square waves Type of value Negative / positive Positive Medium Wire / un-wire Wire Device Amplifier for signals boosting Repeater for signals regenerating (noise also be amplify) (noise isn’t boost) Security Non-encryption Encryption Capacity / Bandwidth Low High Examples Voice, video, file format on Text, integers, images, computer 36 tape, Radio / TV transmission format files (CD, HDD) waves
  37. 37. Analog Signal Example - Telephones take sound vibrations andturn them into electrical vibrations of the same shape before theyare transmitted over traditional telephone lines. Radio wavetransmissions work in the same way. Computers, which handledata in digital form, require modems to turn signals from digitalto analog before transmitting those signals over communicationlines such as telephone lines that carry only analog signals. The ( Copyright revised for Zafar Ayubsignals are turned back into digital form (demodulated) at thereceiving end so that the computer can process the data in itsdigital format.Digital Signal Example - This is the principle behind compactdiscs (CDs). The music itself exists in an analog form, as wavesin the air, but these sounds are then translated into a digital formthat is encoded onto the disk. When you play a compact disc,the CD player reads the digital data, translates it back into itsoriginal analog form, and sends it to the amplifier and eventuallythe speakers. 37