Undergraduate
วิศวกรรมศาสตร์
Data Communication
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31
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A lot of things you must know in data communication
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Note Unit 1 CIS KMUTNB -Data communication - ① • Communication means exchanging of data or information The information may be shared among the computers that are present on same network or between the computers that are connected remotely • Data Communication refers to the way of exchanging digital massage between the devices with the help of communication channel. . Communication Model & Source. -Transmitter Transmission. system i). Source: Device that generate data to be transmitted. (sender) Receiver Destination ¡¡1. Transmitter: Data generate by the sounce is not transmitted directly instead encoding is done the source. (sender) ¡¡¡). Transmission system: Can be single or complex network connected between source or destination. iv). Receiver: It accept signal from transmission systern or if data is encoded then here decoding is done. n. Destination: Device to which tha data is sent by the source. (sender) Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB . Transmission modes : The way in which data is transmitted from one device to another device is known as transmission mode cor) Commuunication mode cor direction mode. • 3 Modes of transmission : Configuration depending on specific circuits, type of transmission facilities. 1). Simplex: In a simplex mode the transmission of data is always unidirectional. T0= 28 C Data P Ex. Badio System or Station ¡¡). Half duplex : In a half duplex mode data transmission is possible in both the direction but not at the same time. D1 Data Data S2 Ex. Walkie-Talhie ii). full duplex: In full duplex mode the transmission is possible in both direction and simultaneously. ป ย Database Design and Applications Earn S. (ENS) $1 Database Design and Apply 34 ComSci, KMUTNB
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Note . . Simplex Mode ④ the communication is unidirectiona A device com only send the data but cannot receive it or it can only receive the data but cannot send it. Half duplex Mode •the communication is bidirectiona, but one at a time. · Both the devices can send and receive the data but one at a time. Half duplex mode is better when compared. full duplex mode is better . Ex. Radio, hey board Ex. walkie-talkie • . full duplex Mode CIS KMUTNB the communication is bidirectiona Both the devices can send and receive the data simutaneously. Full duplex mode is the best Ex. telephone network Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB . OSI Model OST stand from Open System Interconnection. It is a reference model that describes how information from a software application in one computer moves software application in another computer. though a physical medium to the • OSI consists of seven layers, and each layers performs a particular network function. Leach layers is collection of protocals) . OSI model was developed by International Organization for Standardization (ISO) in 1984 and now it is an architural model for inter computer communication. . •OSI model divides the whole task into seven smaller and manageable tasks each layer is assigned a particular task. i). Application layer (langer 7): The top most layer of OSI Model • Provide services for Network application. . •Network application are such application which use network Ex. Chrome, Firefox, outlook, Skype Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note -For protocals- File transfer: transfer file between two users. FTP protocol is used - file transfer protocol web surfing: We search many thing everyding. • we use protocol like HTTP/HTTPS_ Maid maid service use. : • SMTP C Simple maid transfer protocol) -Virtual terminals - hyper text transfer protocol secure ii. Presentation longers: It receive data from application layer. CIS KMUTNB : It perform operation like translation, Dator Compression, encryption and Decryption • Translation: Converting original Messenger text to binary or another format. ABCD 101101001 • Compression: Here size of data or the length is reduced so transfer become faster. 101101001 101110 • Protocol: like SSL, secure sochet's layer protocol are used for encryption and decryption Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note encryption and decryption CIS KMUTNB done at sender 101110 done at reciever 10*111* 0 *10*1110101110 Data security can be archived Ex. ABCD J 101101001101110 →10 x 111x0101110 From application Translation Data compression Encryption layer Decryption ¡¡¡). Session layer: Session layer holps in setting up and managing connection enabling sending and recieving of data and followed by termination of session one transfer done. Before we start a session • . Authentication is done •Authentication: To establish connection you will be extorting your wername and password if matched the session starts (connection established • Authorization different permission to access data or download it. : It also how a track of all file you are downloading it help in version management iv). Transport lager: 051 model, provide transparent transfer of data between and systen or hold and is responsible for segmentation, flow control and erior control and recovery. Database Design and Applications Earn S. (ENS) It ensure complete data transfor Database Design and Apply 34 ComSci, KMUTNB
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Note Segmentation S sequence number J order of data unit to arrange P-post number , to which application S P Data unit S Data P S P Data unit Data unit Datal CIS KMUTNB . Service. any data. Flow Control: constant flow control speed between sender and reciever without Error Control: If any data unit did not reached the receiver the we use Automatic Repeat Protocol request is used. TCP Transmission control protocol) •Connection oriented transmission TCP slower than UDP provider feedback lost data can be retracked Ex. maids, FTP UDP (User diagram probool) Connection transmission • faster than Tcp No feedback lost data cannot be retracked Database Design and Applications Earn S. (ENS) Database Design and Apply Ex. online streaming movie, songs 34 ComSci, KMUTNB
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Note CIS KMUTNB v). Network Layer: It helps the transfer of data received from transport layer in between 2 or more systems. Data Pachet IP1 IP2 Segment Sender IP reciver IP : : Here the data is divided pachets. Router and switching concept are used to transfer data to it's destination. : IP address play a very important role as they are unique identification for a computer. Logical addressing is done vi). Data linh layer: It receiver data packet from network lager. Data pachet consult of IP coddress MAC 1 MAC2 JP1 IP2 segment Tail Frame of sender and receiver Here address of each system are assigned to data pachet to for frame (Physical addrewing) MAC: Is a 12 digit code which is embeded in Network interface card. : Can help transfer of data through wired connection, copper wire and optical fiber : MAC sublayers helps to avoid collisions. vii). Physical layer: Till now all data converted to bits. Now as per : Form one system to another. medium the data is transferred. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note Copper wire optical Air CIS KMUTNB Hi electrical signal Not Hi 1 lager → light radio magnetic signals TCP/IP Model Application NFS Presentation SMTP FIP TELNET SNMP DNS Session Transport TCP UDP RPC ICMP IGMP Network IP ARP RARP IFTP 7lager ICP/IP means transmission. Control protocol and Internet protocol. It is the network model used in the current Internel architecture as well. Protocols are set of rules. Which describe the movement of data between the source and destination or the internet. Data link layer Physical Layer Application Lager Application -Presentation Session Transport layer Inner layer- -network layer Network aces layer -Data link layer Physical layer Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note i). Network Acers Layer: A network layers is the lowest layer of the TCP/IP model. CIS KMUTNB : A network layers is the combination of physical layers and Data link layer defined in OST model. : It defines how the data should be sent physically through the network : Transmission of data between 2 devices is done here. Protocol like Ethernet, FODI ii). Internet lager: An Internet layer is the second layer of TCP/IP model. : An Internet layer is also called as network layer. : The main responsibility of this layer is to send the pachets from protocol: It is used here to identify the reciever its network. any network. ¡¡¡). Transport layer: The transport layer is responsible for the reliability, flow control and correction of oester, Two protocol are use TCP Chansmission control protocols. • TCP slower than VDP • Feedback is provide • lost data can be retracted Ex. maid, FTP Database Design and Applications Earn S. (ENS) UDP (User Datagram protocol) UDP faster than TCP •No feedback • lost data cannot be retracted Ex. Online Streaming movie, Songs Database Design and Apply 34 ComSci, KMUTNB
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Note iv). Application layer: Is top most layer in TCP/IP model : This layer allows the user to interact with the application. few protocol i). HTTP: stands for hypertext tromsfer protocol. It transfer the data is the form of plain text, audio, video. ii). SNMP: stands for simple network management protocol : It is wed to mange the device connected to internet. iii). SMTP: stands for simple maid transfer protocol. iv). FTP : FTP stands for file fremster protocol, used to transfer file between two am. V). Ted Net Is an abbreviation of terminal network. : It establish connection between local and remote computer. Vi). DNS stands for Domain Name System. : Domain name connected to 1P for easy remember of nebsite instead of IP we remember name. CIS KMUTNB Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note . OJI Model • It has 7 layers cdraw diagram) • less reliable • OSI - Open system Interconnection V8 • User different session and presentation layer - Asynchronous Tromster mode (ATM)- . . . . ICP/IP • It has a layers (draw diagram) • more reliable • TCP - Transmission control protocol • Ure both session and presentation layer itself It is switching technique used by telecommunication notwork Data transfer is done in chart It provider interface between mor and network ATM lagers plan managment Upper layer Upper l ATM Adaption Le ATM lager physical Lager CIS KMUTNB i). Physical layer: Involve specification of transmission medium and signal encoding Scheme : Data role in physical langer ranges from 256 Mbp to 622.08 mbps. ii). ATM layer: Provide pachet transfer iii). AAL longer: AAL maps higher level information into ATM cell, to be transporte over an ATM network. iv). User plane provide user information v). Control plan: perform all control and connection functional. vi). Plan management provide coordination between all planes and layers management. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS - Data Tromsmission: Is a mean of transmitting digital or amalog data over a communication medium to one or more device. KMUTNB Sonder i). point to point Data transmission one device to another one device ii). point to multiple one many parallel transmission - Parallel tromsmission: Here all the 8 bits of data is transferred from sender to receiver in a parlicular movement & bits are sent after other terial transmission 0 Synchronous A Synchronous transmission transmission 0 0 receiver Sonder 01011010 Direction to flow receiver 0 0 Sonder receiver 1 101101 10111010 11001 0 0 8 bits on & different layers Serial Transmission bits or gaps. Sonder receiver 101101 10111010 11001 Database Design and Applications Earn S. (ENS) . synchronous transmission sendind bits one after another without start and stop The reciever counts the bits as they arrive and them in & bit mits. group Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB · A synchronous transmission: sand one start bit cos at the begining and one stop bit (1) at the end of each byte Sonder receiver 10110 1110100110 11110 : cheap and effective end 111010011 01 data start Parallel communication • & data bits can be transferred at a time trafer rate is high • . Serial data communication only data bit can be transferred at a time data transfer rate is low . installation cost more used for smaller distance • a line are needed to armect . A synchronous communication start and stop bits are used • cheap • simple . . installation cost less . used for larger distance • 2 lines are needed to armect Synchronous communication no start and stop bits • Expensive . Complex •les hardware Database Design and Applications Earn S. (ENS) • more hardware Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB -Transmission Media: In data communication terminology, a trommission medium is a Transmission Media physical path between the sender and reciever. It is the channel through which data is sent from one place to another. Covided media Un Govided media 1). Guided Media Radio wave It also referred to a wired and Bounded transmission media. Coaxial fibre Optics Twisted Base Band Boond Bond →unshielded shielded Microwave infrared feature : high speed speed : used for comparatively shorter distance li). Twisted Pare Cables: It consists of 2 seperately insulalator, conductor wires would about each other generally several such pairs are bounded together condutor Insulator Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note a). Unshielded Twisted Pair: This type of cable has the ability to no shield block interface and does not depend on a physical shield for this propose used for telephonic application. advantage: It's cheap : Installation of the andhielded twisted pair is easy. I can be used for high speed lan disadvantage: must be used only for shot distance CIS KMUTNB b). shielded Twisted Pair: This type of cable consist of a special jacket to block external interference. It is used as ethernet and telephone line. shield advantage: easy to install : high quality : faster transfer disadvantage : more expensive Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note ¡¡). Coaxial Cable: It has an outer plastic covering containing 2 parallel conductor each having a seperate insulator protection cover. Conductor Tacket shield Insulator . . 2 mode CIS KMUTNB Broad band: It is defined as the process of tromsmitting multiple signals Simultaneous. Base band: It is defined as the process of tromsmitting single signals advantage: high speed : high bandwidth at a time. : better than twisted pair disadvantage more expensive ¡¡¡). Opital fiber Cable: It use the concept of reflection of light through a core made Cor Tach cladding glass or plastic. It is used for transmission of large volume of data advantage: faster speed greater bandwidth : longer distance of Database Design and Applications disadvantage: Copen give Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note - Unguided Media: It's also referred to as niveles or unbounded transmission feature less secure : : Use for longer distance : Signal is broadcasted through air is. Radio worker: These are easy to generate and can penetrate through building. range advantage ii). Microwave 3 kHz to 16H₂ Ex. FM Radio cover lavage are and ponstrate through wall. It provider high transmission rate cis KMUTNB : It is a line of signal transmission that is the sending and receiving need to be property aligned with each other. range 1GHz to 300 GHz Ex. TV, salellight advantage: cheaper than cable : large area disadvantage: Bandwidth limited Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note iii). Infared Infared ware are used for (cannot petrate through walls) vary short distance communication Ex. 6PS CIS KMUTNB range 300 GHz - 400 TH₂ advantage: high band width : data rate high : more secure disadvantage cannot petrate through roch and wall : - Digital data to Digital digital: It is a process of converting binary data, sequence of bit, 001011 sequence of bits digital data to a digital signal [line coding] 0 Digital signal Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB Classification of line codes 1 - Rt return to zero Unipolar POLAR BIPOLAR Rz NR2 AMI RZ NR2 Manchester properties of line codes: bandwidth used is reduced : power is efficiently used : probability of error is reduced WP non return to zero Unipolar: Only one voltage level other than Polar: Two voltage level other than zero Bipolar There voltage level +ve, -ve, o 1). Unipolar R2 formal: cache zero (+A) or O (+ 1/2) or (- A½ 2 ) or 0 • off pulse : each 1 " on pulse and duration of Tn/e follared by Ex. 1 0 1 1 A : error detection and correction is possible. : cross talk between channels will be reduced ¡¡¡). Polar RZ formal : A/2 • logic 1 con +ve) A/2 · logic o coff -ve) Ex. 1 0 +A/- bit-duration To/2 0 i). Unipolar NR2 formal: each off pulse : each 1 • on pulse and duration is Tb -4/2 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note iv). Polar NR2 formal (NR2-2): A/2 Ex. +A12 -4/2 CIS KMUTNB ▸ logic I con +ve) A/2 logic o coff-ve) bit-duration 0 To 1 V). Bipolar NRZ formal (NBZ-2): All +A logic 1 (for 1*, 050 Ex. +A even-A logic 1 c for 2nd, bit-duration To 0 1 Vi). Split Phase Manchester format: Symbol | = positive pulse of +A/2 amplitude for one half of symbol duration followed by negative pulse of -A/2 for remaining half duration : Symbol "0" Ex. +A/2 1 0 1 1 • reverse order -A/2 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB vii). Polar NRZ formal (NRZ-I): if encountered then it will fix and reduce when another o is formal if 1 encountered then it will fix and reduce when another 。 is formal Ex. +A/2 1 -4/2 - Analog data to digital signal conversion: representing analog data by digital signal : We use decoder und encoder Ex. to record a song/voice 2 methods is. Pulse Amplitude Modulation 1. Pulse code Modulation i). Pulse Amplitude Modulation (PAM): take analog signal sampler it and generate series of pulser based on the result of the sampling Database Design and Applications Earn S. (ENS) : sampling means measuring the amplitude of a signal to equal interredds : PAM uses a technique called sample and hold Database Design and Apply 34 ComSci, KMUTNB
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Note i). Pulse Code modulation: To overcome disadvancetage of PAM PCM is used : PAM is 1st step in PCM CIS KMUTNB : PCM modified the pulse created by PAM to create a completely digital signal I sampling - quantization line-coding - A). Sampling: No. of sample of the signal are taken at regular intervals of a higher frequency of b). Quantization hritten in binary formal : C). line- coding: conversion to digital signal signal. PAM Quantization ง Binary encoding. 0 0 1 0 11 0 0... + line coding # Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note CIS KMUTNB — Digital data to Analog signal conversation: When data from one computer is sent to another via some analog Courier, it is first converted into analog signal. : An analoy signal is characterized by its amplitude, frequency and phase shift keying is Amplitude Shift Keying: when binary data represent digital 1, the amplitude is held chigh). 0 1 mi when binary data represent digital 0, the amplitude is 0 (0). i). frequency shift Leying: chighers for one frequmay fo 1 (lower) for o another frequency f₂ 0 1 iii). Phase shift keying: when a new binary symbol encountered the phone of the sight shift 0 alterately. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB -Analog data to Analog signal A to A Analog signal are modified to represent analog data i). Amplitude Modulation: In this modulation, the complitude of the carrier signal is modified to reflect the analog data ¡¡). frequency modulation Amplitude modulation is implemented by measure of a multiple : It can be achieved by making changes in the voltage ¡¡¡). Transport layer: The transport layer is responsible for the reliability, flow control and correction of data. TCP (Transmission control protocol) : TCP slower than UDP Database Design and Applications Earn S. (ENS) UDP CUser Dalogram protocols : UDP faster than TCP Database Design and Apply 34 ComSci, KMUTNB T
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Unit 2 Note CIS KMUTNB Multiplexing: A techique use to combine and send the multiple data stream over a single medium. combining the data streams is known as multiplexing. The process of : Multiplexing is archived by using a device called multiplexing (MUX) that combine input line to generate a single output line. : De multiplexing is archived by using a device called Dermultiplexer CDMUX) available at reciver side. ilp lines ..... XC3 M ...... alp ะะ lines i/p - imput mux- multiplexer DMWx-demultiplener advantage: more than one signal can be sent over a single medium Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note Multiplexing types CIS KMUTNB Frequency division multiplexing Canalog) Have length division multiplexing (analog) i). Frequency division multiplexing : It is on aralog technique Database Design and Applications Earn S. (ENS) Time division multiplexing (digital) Synchronous TDM A synchronow TDM In FOM all wers are the same common channel at the users use the same common channel at the same time (for full times but they are allocated different recurrences to present my signal interface : So the bandwidth is divided among usew not time. and Apply hind of Diss Bossibility & brew state in FDM since all signal over 34 transmitted simultaneowly ComSci, KMUTNB
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Note Frequency User: 1 User: 2 CIS KMUTNB advantage: FDM is used for conaby signal. : FDM is very simple and for full time. disadvantage: It suffer from cross talk Ex. radio FM ii). Howe length Division Multiplexing (WDM): It is on amaloy technique In Iq 11+1₂+13 1 -12 I3 multiplexer Demultiplexer In by U₁ In by Uz U-User Iz by U₂ : WDM is same as FOM except that the optical signals are transmitted through the fiber optic cable. : Frequency are very high. : high desta tromster rato : at sender multiplexer and at reciever demultiplexer is used. : digit can be sent by different amount based on the angle of incident and wavelength of digit. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note ●Circuit Switching ¡¡). Time Division Multiplexing (TDM): It is a digital technique •space division switching Frequencies User: 1 Uver: 2 Switching Techique Time CIS KMUTNB : It TOM computer channel band width is allowed to one user for a fixed time slot. : It means each wer can use the full bund width available but for a fixed (it's own time slot) So the division is in time not in band width. Here no crow tall issue. disadvantage : capacity of user is not fully utilized Message switching Packet Switch TOM Datagram Virtral time division switching appach Circuitt Approach advantage Synchronous TDM A Synchronous TOM Switched best when Permamant company with virtual virtual Circuit Circuit Synchronou Time slot's are Dynamical time slot pre assigned to allocation is don Database Design and Applications Database Design and Apply Earn S. (ENS) 34 ComSci, KMUTNB
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Note Switching CIS KMUTNB : The technigm of transforming the information from on computer networh to another computer network is known as switching : Switching in a computer network is achieved by wing switches. [process of forwarding pocket from sender to reciever] : A switch is a small hardware device which is wed to join multiple computers together with one local ore het worth. : Switcher operate at layer (2) in as I model. : pachet collision is minimum. Switching techniques: In large networks, there can be multiple parths from sonder to receivers. The switching technique will decide the best route for desta transmission. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS i). Circuit Switching: It is a transmission mode that involves setting up a dedicated end to end connection : commonly we in telephone system : connection oriented : no delay in data flow KMUTNB : link of the connection cannot be use by any other data when it free. : More band width required. : Connection time is more. 3 Phase 1). Circuit establishment ii). Data transfer ii. Circuit disconnected advantage: the communication channel is fixed : no delay in data flow : fixed band width disadvantage connection time is more : when path is free other cannot are it Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note 1). Message owitching: There is no dedicated path between two communicating devices M₁ UC SF M₂ M₂ ·S,F SF M₁ B C CIS Each message is treated as an independent unit and included its own destination and source address. : Also called as store and forward network : efficient traffic management : some dolay due to staring and forwarding 4: large storing capacity is required. Advantage efficient traffic manag management DisAdvantage: some delay due to storing and forwarding Ex. digraph network : store and forward lat every switch data stored and forward when next switch have enough space. KMUTNB Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note iii). Pachet Switching: In this message are broken up into packet : Individual pachet talk different routes to reach the destination. Advantage: Bandwidth reduces, efficient, cost efficient In link failure different route can be chosen for remaining packets Pachel Switching CIS KMUTNB dis Advantage: a bit complex ex. Parhet switch : high usage of ram 4321 A 24 31 Data gram packet switching (pachets can follow different path) Virtual Circuit pachet switching (a fixed circuit path is follow) 43-> Digital subscriber line: (DSL) It is a communication medium which is used to transfer internet through copper wire telecommunication line : When we get broadband from popular company like BSNL then we take a plan with landline and internet then the connection they provide nos is Digital Subscriber line Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note DSL CIS KMUTNB : In previous years they use to give Daid-Up ammection which faced a problem (Network disconnected when : It's removed in DSL Advantage: No additional wiring Symmetric Asymmetric : Cost efficient your in call) Phone line Internet line 30 70 : User can use both telephone and internet at the same time. Symmetric DSL Here slipping of upstream and downstream frequencies : Provides equal speeds to both uploading and downloading data transfor : This connection may provide 2 Mbps upstream and downstream. Advantage: equal up stream and down stream speed DisAdvantage: mostly up stream speed is noeles : not so efficient Phone 30 Uputron Constresum 35 Database Design and Applications Database Design and Apply Earn S. (ENS) 34 ComSci, KMUTNB
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Note CIS KMUTNB Asymmetric DSL Provides a wide frequencies range for downstream tramsfor, which offers several timer faster than ODSL Phone Upstream Donnstresom 20 → Multiplexing, by p FOM wom 50 TOM* ~Circuit, →Switching technigry switching Packet Switching message Digital Subscriber di * Switching Symma Asymmetric Digital Dala Communication Techniques (Data transmission in Unit I). • Upstreum 20 Mbps and 1.5 Mbps Upstream As most users download most data than upload Hence, ANSL is widely Advantage: Both telephone and internet can be at any point of time. : Better than all correction Disadvantage: quantity of the wire should be high. Indepond on external factor distance 3km. Characteristic of ADSL : He can upload the data at a lower data speed rate : we can download the data at a higher data speed rate : Both telephone and internet usage can be at any point of time. Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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RAINBOWDASH Note Unit 3 CIS KMUTNB Eror Detection Techniques: Is the detection of errors caused by noise or other impairment during transmission from the transmitter to the reciever. : Error detection and correction are implemented at the data link layers or the transports layer of the open system interconnection mode (OSI) Few error detection technique: Simple parity check Two dimensional parity chech · Check sum Cyclic redundancy chech Error Due to noise or any external face change in binary bit. O to 1 or 1 to 0 is called error Types of error Single-Bit ervar : In this only 1 bit in the data unit has changed 1 0 1 1 0 0 10 [sender] Jh I 1 0 1 1 0 0 0 0 [reciever] Database Design and Applications Earn S. (ENS) Burst error : In this 2 or more bits in the data unit change Database Design and Apply 1 0 1 1 0 0 1 0 1 0 1 1 1 0 0 1 10 34 ComSci, KMUTNB
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Note CIS KMUTNB Error detection i). Simple parity check : In this an extra bit (parity bit) is added to each word before transmitting ex. Data Even parity Even parity: No of is in given word including parity should be even. Odd pornity: No of is in given word including parity should be odd. * 1 0 0 1 0 1 1 =>Parity Data data already how even is Hence PO 01001011 assume due to noice data changed to 00001011 Odd parity data already has even is Hence P1 to make it odd 11001011 11101011 limitation: not suitable for detection of multiple error : can only identify wheather their is a enor but not correction now odd no of is hance error occured Database Design and Applications Earn S. (ENS) now odd no of is home error occured Database Design and Apply 34 ComSci, KMUTNB
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Note ii). Two Dimensional CIS KMUTNB Parity check: In this, the data word is organized in table or matrix (row and column) Nate: It checks and detect up 3 emors. Errors affecting a bits. Ex. assume for even parity not be detected may Row panty 1 1 0 0 1 1 1 1 Row parity 1 1 0 0 11 1 1 1 1 0 0 1 1 0 1 10 1 0 1 1 1 0 1 1 0 1 1 100 1 0 chany 1 bit 0 1 1 1 o 0 1 0 0 0 1 0 1001 1 1 0 1 0 10 0 1 1 01 0 10 10 0 10 10 10 column parity 0 1 1 1 0 10 column parity 1). Chech Sum In this each word is added to the previous word and total sum [chech sum] is calculated. Then chech sum is transmitted along with the dater. Ex. 7, 11, 12, 0, 6) sender Data CS if (CS-CS₁) then +WS - chech sum Data CS Jender [reciever no error 7+ 11+ 12+ 0 + 6 - 36 Calculate check sum again else error CS compare cs, and as Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note 7, 11, 12, 0, 6-36 Chesh sum 7+19+12+0+6 instead of is send computed of co ex. using one's complement 7, 11, 12, 0, 6-36 ✓ recieve check sum 36 sonder + *0, (no enor) - 36 + binary 100100-as the no of (36) bit are 74 hal mapping in. Cyclic Redundancy Chech (CRC): It's based on the concept of Binary Division. CRC Generator 17. Append string of no's to the data unit 11). Divide newly generated data unit in by the divisor i). Remainder after (ii) is a bit CRAC iv). The CRC will replace n is to get cod word to be transmitted CRC Chech is. Here the reciver reciver the data and CRC (code word) ii). Divide is by divisor iii. if remainder 0 (Accept) remainder (reject) or cerror) 0 1 0 0 10 CIS 9110 (6) (invers) 1001(9) KMUTNB Data verse CS/ 7, 11, 12, 0, 6 9 PTO at reciever 7+9+12+0+6+9 -45 binary 101101 th (AS) all zero no error apping 1101 10 111 1 Imene 0000 Database Design and Applications Database Design and Apply Earn S. (ENS) ComSci, KMUTNB 34
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Note n bit CIS KMUTNB Cx. Dataset • 1001, Divisor 2011 (n+1 bit) = Data 00...0 Data CRC Data 1001 1001 110 - sender Divisor (n+1)) J CRC (remainder) Data CRC transmitted 0000 Divisor (n+1)] 101 101101001000 10 1 1 1 00100 at reciver 1001110 10111001110 (1010 10 1 1 | 0010 1 remainder 1000 00000 1011 1011 1011 0110 CRC 0000 (no error) (error) 0000 Code word) 0000 110 reminder 0000 reminder Hence, no error Error correction: Error correction codes are the sender to the receiver. All above 4 methods help in error detection use to detect and correct the error when data is transmitted from Two ways: i). Backward error correction: Once the error is discovered the receiver requests the sender to retransmit the entire data unit. ii). Forward error correction: In this case the receiver use the error correct the error. Database Design and Applications Database Design and Apply conecting code which cartomatic 34 Earn S. (ENS) ComSci, KMUTNB
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Note CIS KMUTNB Hamming - Hamming code is one of the most popular and used for error correction and detection Hamming Codes: It can be applied to date unit of It is wed to be detect and correct my length single bit enor code structure: All bit position that are power of 2 are marked as parity bit (32,9,8) other bit ove for data For P₁ check bit skip 1 bit... D7 Db Os Pq Os Pe Pv 05 P1 i Pa : Commonly we use 7 bit hamming code PqPqP 3 Og Dy · P₂ → P₂ D₂O₂ Dy P₁ 101 P₂ 1111 Pq 011 Pa Pa D50, D (1,3,5,7,9,...) For P2 check 2 bit skip 1 bit... (2,3,6,7,10,11,...) For Pa check 4 bit skip 1 bit... Database Design and Applications Earn S. (ENS) (4,5,7,12,16,14,15,...) Pq Dz Os Oy Pq Dz Og Oy Pq Ds O, Oy 07 06 05 Pa Ds P₂ P₁ 1100110 Sender sent Detecting error consider 7 bit code 07 06 05 Pa Ds P₂ P₁ : At reciever end, bit (1,3,5,7) (2,3,6,7) and (9,5,6,7) are cheched for even parity then to error then Database Design and Apply error 34 ComSci, KMUTNB
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Note Ex. i). 7 bit hamming code received 10110 11 arume even parity recieved HC 07 06 05 Pa Ds P₂ P₁ 1 | 0 11011 Detecting error analyze P, 1,3,5,7 »>> - 1,000 (1,0,1,1) odd parity Correcting Error CIS KMUTNB : An error is located by farming a 3 bit no. of out of 3 parity check (P₁, P₂, Pa) Find P1 he check (P₁, D8, Ds,D,) if P₁.0 no error P₁-1 ervoy similarly and Pa Pa P After we found the error word we find the decimal valow. we complement the incorrect bit to obtain the correct word. Put P₁1 error exist Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB Data link Control: The service provided by the Data link layer to provide reliable data transfer over the physical medium ex. In the half duplex transmission mode, one device can only transmit the data at a time. If both the device transmit the data simulataneously, they will collide and load to the less of the information. The data link lager provide the coordination among the device so that no collision or occurs. The data link layer provides & function i). line discipline Data link control J line Discipline Flow control Eror control lij. Flow control ii). Error control He should send How much data Hoy we can occur the data should be send be detected i). Line Discipline : The functionality of the data link layer that provide the coordination among the link system (among systems It determine which device can send, and when it can send the cate Line Discipline ENQ/ACK Poll/ Select JENG/ACK: stand fore Enquirel Acknowledgement : It takes care that which device will start the transmission and whether the recipient (receivers) Database Design and Applications Earn S. (ENS) is ready or not Database Design and Apply 34 ComSci, KMUTNB
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Note 20 working: Initially transmitter transmits the from called an receiver is available to recieve the data or not Establishment Data transter ACK ENQ Ach ACK Data Data CIS KMUTNB Enquiry (ENQ) ashing whether the : The reciever responds either with acknowledgement (ACK) or with negative acknowledgement (NACK) Where positive acknowledgement means that the receiver is ready to receive the transmission and negative acknowledgement means that the receiver is not ready to receive to accept data : If the respond to the ENQ is positive, the sender will transmit its data and one all its data has been sent the device finishe it's transmission with on EOT LEnd-Of-Transmission] : If the respond is negative nor positive for ENQ then 3 citterupts will be made. Termination :) EQT Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB poll /select: The method of line discipline works within those topologies where on device is designed as a primal station cmd other devices are secondary (1 to many types The primary device and multiple secondary devices consists of a single transmission line and all the exchange are made Himayh primary device even though the destination is a scondary device. selecting: If the primary device want to send some clata to the secondary device then it tells the tingut secondary device to get ready to receive the date, this process is know as selecting. working of poll Use when the primary device wants to receive some data from the secondary device. : When a primary device want to receive the date, then it astw each device whether it has omything to rend. : Initially, the primary device asks (poll) the first secondary device, if it responds with NACK meam that it how nothing to send. : Now it approaches 2 nd Secondary device, if it responds with NACK means that data is sent. : If that device is ready it will Ack and from then denta will be sending Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note primary device secondary device 80 Primary device secondary device CIS KMUTNB 20 poll NACK Data poll Ack poll SEL ACK DATA Ack working of select: The select mod is used when the primary device has something to send. When primary device wants to rend it select a device and send SEL to that device. NACK Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note ii). flow Control flow CIS KMUTNB control: It is a set of procedure that tell the sender how much data it can transmit stop and wait sliding window render before the data overflow at receiver. : The receiver has limited speed and limited memory to store the data. : The receiving device must be able to inform the sending device to shop the tvaromission temporarily before the limits are reached. i). stop and wait from the name we can say it stop and waits Data ACK ACK EQT Data receiver : Initially, the data is sent from the sender sids to the receiver side and now sender wait's for Achnarladgement and one Acknowledgement is received then it again send data. : It continue lill whole is transmitted at the end of the data after receiving Ack sonder sends EQT CEnd of transmission) ii), Sliding Window flow control protocol: Is a dynamic window which allow the Sender to transmit a specified number of a data unit before an Acharladgement is received. : This is used to overcome the problem of stop-and-wait protocol and one frame at a time. R receiver 3 | 0 | 1 | 2 sender F-fram 0 1 2 3 0 12 3 0 1 Fo 3 | 0 1 2 0 1 2 3 0 | 1 | 2 | 3 0 1 M 0 1 2 3 0 1 2 3 0 | 1 2 Database Design and Applications 0 1 2 2 0 1.1. 3 ACK2 0 1 2 0 1 Earn S. (ENS) Database Design and Apply 3 3 3 | 0 1 2 3 3 | 0 | 1 | 2 | 3 123 34 ComSci, KMUTNB
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Note 0 1 2 3 0 12 3 0 1 2 3 0 12 3 AckQ 0 1 2 3 | 0 1 2 3 0 | 1 2 3 | 0 1 2 3 CIS KMUTNB receiver sender 0 1 2. 3 | 0 1 2 3 This wall more right when Ack recieve This wall moves to the right when a frame is sent 0 1 2 3 0123 • This wall move right when Ack Sent This wall moves to the right when a frame is recieve Error Control: A technique of error detection and retransmission. 11. stop and wait ARQ: The problem faced by stop and wait will be rectified using stop and ARQ Engr Control shop and wait sliding window ARQ ARQ Problem faced by shop and wait Go back N Selective 11. last data 21. lost Ack 31. delayed ACK stop and wait AAQ S R S R dala *x sender nail for Ack and receiver wait for Ack for infinite amount of time data ACK sender wait for Ack for infinite amount of time after timeout on sonder side a long delayed Ack might be wrongly considered as act of some other packet to rectify above problems we we both error control and flow control am wait + time out + Seg No data) + Jeg No (ACK) + last dala last ACK delayed ACK Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note
W. time out
Here in their situation the sender
will wait for a pasticular amount of
time and then he will resend data
b). Sequence no data)
tim
Here also the sender waits for some time
and be resend the data again nou receiver
receives again and this data will be distorted
a halved hasit
c). delayed ACK
Oct
This is resolved by introducing seg no for ach also.
data
x
data
ACK
data
data cono and Ac
time
out
ACK
dat check and distored
data
ACK
B
ex.
data o
ACK 1
data 1
time cul {
ACK O
data o
datao
time J
ACKA
out
data 1
AKO
data o
Database Design and Applications
Database Design and Apply
ACKO
Earn S. (ENS)
CIS
KMUTNB
34
ComSci, KMUTNB
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Note
CIS
KMUTNB
Data o
Data
Data 2
Data 3
11). Go Bach n ARQ: If one frame is lost or damaged, then it
retransmit all the frame after which it due not receive the positive ACK
: In the some a cave the retransmission is done
i). Damaged frame
ii). lost Data frame
wwent
ACK 2
Data 2
revent
Data 3
data 4
{
time
timm
int
ACKO
Data 4
Data 4
Ack O
Database Design and Applications
Earn S. (ENS)
Error, Qucard
Discarded
ii). Lost Acknowledgement
1. Seductive reject ABQ more efficient than do.
Resend
WAK
Data o
Data
Data 2
Datas
Data 4
R
:
-
Back-n ARR
only those frame are retransmitted for which negative
acknowledgement (NACK) has been received
error in fram
: The receiver storage buffer heeps all the damaged frame an
holding until the frame in error is correctly received
The receiver must have an appropriate logic for reinserting
the frames in a correct order
: The sender must consistt of a search mechanism that selects
the requested for for retransmission
only
Data 2
ACK
Database Design and Apply
34
ComSci, KMUTNB
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Note CIS KMUTNB High level data link control: The high level data link protocol (HDLC) developed by ISO HDLC is a bit - oriented data link protocol, and it is designed to satisfy many of dat a control requirement) : HDLC protocol has three station 1). Primary station (endor) ii). Secondary station creceiver) ii). Combined station (Both) mode of operation are is. Normal Response model (NPM): This mode is suitable for point to point as well as point to multipoint configuration ii). Asynchronous Response modol (ABM): This mode is used for communication between Primary and Jecondary station ¡¡). Asynchronous balance modol (ABM): This mode is applicable to point to point communication between Combined station Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note i). Normal Response Model One primary station can send command : Multiple secondary station can sent response. Point to point and point to multipoint Point to point CNRM) -command P.S 8.S response Point to Multipoint (NAM) -command P.S response 8.6 response ¡¡). Asynchronous Balance mode (ABM) Only point to point : each station can function as : Point to point (ABM) primary command respond ← command respond station1 station 2 und Secondary From structures: There are there type of frame supported CRC checked by HPLC S.S i). Here the receiver receive the data and CRG (codeword) ii). Divide (i) by divisor iii). if remainder 0 (Accepts remainder rejects or cerror) Database Design and Applications Earn S. (ENS) i). Information (1) frame Flag Addrer Control CIS userdata KMUTNB Transport Control information Ver inte FCS Flag i). Unnumbered (U) Function Flag Address Control Transport only control inf FCS Flag iii). Unnumbered (U) frame Reserved for system manage Mange Flag Addvar Control FCS Flag inte a). Flag: to identify begining and end of the frame b). Address: Contains the address of the secondary station c). Control: used for error and flow control d. Information users dala or management info es. FCES: frame check Sequence error detection field iv). Cyclic Redundancy check (CRC) It is based on the concept of Binary → CRC Generator Division i). Append string of no's to the data unit ii). Divide newly generated data unit in ci) by the divisor . Remainder after (ii) is n bit CBC Iyir). The CRC will replace no's, to get code word to Database Design and Apply be transmitted 34 ComSci, KMUTNB
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Note bit Data 00...0 binary Data CRC ex. i). Dataset 1001, Divisor *1011 $ Data 1001 Divisor 1011 Cn+ybit) n°3 101 10111001000 CIS 1001110 KMUTNB Jender at receiver 10011110 Divisor (n+1) bit Divisor (n+1) bit 10111001110 (1010 XOR CRC Cremainder) remainder 1 0 1 1 1 00100 XOR 1 0 1 1 1 0101 0000. 0000 Onta Clode word) CAC 0 1000 101 1 (No Way) (erver) Error comection : Error correction code are used to detect and urrect the error when data is transmitted from the sender to the receiver. 0000 110 All the above a method help in error detecting 10 1 1 0011 0 101 1 000 0 CBC CBC 0000 remainder 000 remainder o Hence, no Ewor Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note Unit 4 CIS KMUTNB Type of networks i) local Area Network (LAN): It is also called as LAN and designed for small physical area such as am office, group of buildings or factory : LAN's ave wed widely as it is easy to design and troubleshoot. : We can use different type of topologies through lan, there one star, ring, bw, tree, etc. 80 Bus Network Brider → private network → high speed Ring- -network Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS KMUTNB ¡¡) Metropolitan Area Network (MAN): It was developed in 1980's : It's basically a biggest version of LAN : It is also called MAN and user the similar technology as LAN : It is designed to extend over the entire city. : Both private or public company ex. different branch of company Router 80 Bus Network Database Design and Applications Earn S. (ENS) LTE local Telephone exchance • 50 km range Router . optical filter ove used Ping-network Database Design and Apply 34 ComSci, KMUTNB
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Note ¡¡¡) Wide Area Networth (WAN): long distance such as country/state. : It can be public or private network. : Design and maintane is complex. Router CIS KMUTNB 80 Bus Network . over Einternet Router Communication medium used are satellite, public telephone network which are connected by . Expensive router. Security is real issue here. Database Design and Applications Ping-network • Every one on the network can use the same data 0 Setting up a network com be expensive. Database Design and Apply Earn S. (ENS) 34 ComSci, KMUTNB
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Note Types of connections i) Point to Point connection: Dedicated link between two divine PC1 PC2 CIS KMUTNB link ¡¡) Multiport connection : More than two devices shares a single links Server PC1 link ร PC2 PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note Network Topology แบ่งออกเป็น 2 ประเภทหลักๆ คือ: CIS KMUTNB Physical Topology (โทโพโลยีทางกายภาพ): หมายถึง การจัดวางตำแหน่งและเชื่อมต่อสาย สัญญาณของอุปกรณ์ต่างๆ ในเครือข่ายจริงๆ เช่น การเชื่อมต่อแบบดาว (Star Topology), แบบบัส (Bus Topology), แบบวงแหวน (Ring Topology), แบบเมช (Mesh Topology), แบบ ต้นไม้ (Tree Topology) และแบบผสม (Hybrid Topology) Logical Topology (โทโพโลยีเชิงตรรกะ): หมายถึง วิธีการที่ข้อมูลไหลเวียนและถูกจัดการบน เครือข่าย โดยไม่จำเป็นต้องสอดคล้องกับการเชื่อมต่อทางกายภาพเสมอไป ตัวอย่างของ Network Topology ที่พบบ่อย: Bus Topology: อุปกรณ์ทั้งหมดเชื่อมต่อกับสายสื่อสารหลักเพียงเส้นเดียว (backbone) Star Topology: อุปกรณ์ทั้งหมดเชื่อมต่อกับอุปกรณ์ส่วนกลาง (เช่น Hub หรือ Switch) Ring Topology: อุปกรณ์ทั้งหมดเชื่อมต่อกันเป็นวงกลม Mesh Topology: อุปกรณ์ทุกตัวเชื่อมต่อกันโดยตรงกับทุกอุปกรณ์ ทำให้มีเส้นทางสำรองใน การส่งข้อมูลหลายเส้นทาง Tree Topology: เป็นการผสมผสานระหว่าง Bus และ Star โดยมีโครงสร้างคล้ายต้นไม้ Database Design and Applications Database Design and Apply Earn S. (ENS) 34 ComSci, KMUTNB
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Note Types of Network Topology: describe appearance of network i). Bu topology (Multipoint type) Easy to install, use for small retrorh Cheap CIS KMUTNB PC1 Easy to expand Slow speed as only one system can transmit at a time. failure in cable bring down whole network. PC2 PC4 80 link single link ร C PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note CIS 11). Ring topology: In this each computer is connected to the next computer with the last one Connected to the first Multipoint data connection Taken passing is wed : fault in any link bring down entire network Difficult to troubleshoot the ring. PC1 PC2 KMUTNE PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note ¡¡¡) Star topology: All hives from the comperter go to a central location howing a device called HUB All communication gow through HUB : If central HUB fail, whole network fail : Cabling cost is more PC1 PC2 CIS KMUTNB PCA HUB link broken PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note PC1 " iv) Mesh topology: In this each device has a dedicated point-to-point link to : due to dedicated link, there is no traffic problem • failure of one link doesn't offect entire network. : Expensive due to higher cabling cost : If we have n device cn (n-1)/2) linh are needed PC2 I More secure and private : Easy fault diagnoses (Paint to point) Expensive due to higher cabling cost every ncn-1) 2 CIS KMUTNB other device PCA PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply 34 ComSci, KMUTNB
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Note V) Tree topology: Variation of star topology : Nodes in a tree are linked to a central hub : Cabling coat is more : On failure of central HUB, entire network breaks down PC1 80 HUB PC2 HUB 80 HUB PC4 PC3 Database Design and Applications Earn S. (ENS) Database Design and Apply CIS KMUTNB 34 ComSci, KMUTNB
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Note nd Data link layer: It is the 2' layer from the bottom : It is responsible for nodo to node delivery of message taken care by Dota link layer 80 take 1 come by network lager CIS KMUTNB Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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Note CIS KMUTNB Database Design and Applications Database Design and Apply 34 Earn S. (ENS) ComSci, KMUTNB
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