SPU Information Science Institute of Sripatum University Sripatum University 1 IS516 Computer Communication and Networks การสื่อสารคอมพิวเตอร์และเครือข่าย Asst.Dr.Surasak Mungsing

SPU Information Science Institute of Sripatum University 2 Course description ศึกษาสถาปัตยกรรมของเครือข่ายและพิธีการสื่อสารแบบต่างๆ หลักการของการสื่อสารข้อมูล โปรโตคอลพื้นฐานและชั้นสูงที่ใช้ใน การติดต่อสื่อสาร ศึกษาอุปกรณ์สำหรับเครือข่ายสื่อสาร การเชื่อมโยง เพื่อสร้างเครือข่ายและรองรับข้อมูลในเครือข่าย การสวิตช์และจัด เส้นทาง เครือข่ายบริเวณเฉพาะที่ (Local Area Network) และ บริเวณกว้าง (Wide Area Network) ความมั่นคงของข้อมูล การ ออกแบบระบบเครือข่ายเพื่อใช้งาน การใช้เครื่องมือวัดสมรรถภาพ การปรับแต่งเครือข่ายเพื่อกระจายการใช้งานในเครือข่าย การ เปรียบเทียบสถาปัตยกรรมของเครือข่ายแบบต่างๆ กับระบบดั้งเดิมที่ ใช้เครื่องใหญ่และแบ่งกันใช้เวลา ศึกษาเครือข่ายอินเทอร์เน็ตพร้อม ยกตัวอย่างประกอบการเรียนการสอน มีการจัดกลุ่มนักศึกษาเพื่อสร้าง โครงงานเครือข่ายที่กำหนด

SPU Information Science Institute of Sripatum University 3 Objectives To understand computer network architecture and communication protocols To study network devices and network connections To learn how to analyze and measure network performance and design high performance networks To understand and realize the importance of information and network security To understand and realize the benefits of the Internet To design computer network

SPU Information Science Institute of Sripatum University 4 Lecture schedule (Before Mid-term) WeekTopic 1 Course Overview and Introduction to Data Communication 2Computer Networks and Network Taxonomy 3The theoretical basis for data communication 4Networking Device and Software 5Guided Networks 6Switching and Routing 7Network Design 8Mid-Term Examination

SPU Information Science Institute of Sripatum University 5 Lecture schedule (After Mid-term ) DateTopic 9Network Performance 10Internet and Applications 11Wireless Networks 12Network Security 13Network Systems and Services 14Group Project Presentation 15Term Paper Presentation 16Final Examination

SPU Information Science Institute of Sripatum University 6 Evaluation Collaborative Problem solving35 % Term Paper & presentation 20 % Participation 5 % Final Exam 40 % Total 100 %

SPU Information Science Institute of Sripatum University 7 Text Data Communications and Networking, Behrouz A. Forouzan, Fourth Edition: McGraw Hill, 2007 Business Data Communications, William S. Stallings, Fifth Edition, Pearson Prentice-Hall, 2005 Computer Networks, Andrew S. Tanenbuam, Fourth Edition: Pearson PrenticeHall, 2003

SPU Information Science Institute of Sripatum University 8

SPU Information Science Institute of Sripatum University 9 IS516 Introduction to Computer Communication and Networks

SPU Information Science Institute of Sripatum University 10 Telecommunication Communication based on electromagnetic Light speed vs Sound speed - Sound speed : ~ - Light speed : ~ Bandwidth : related to amount of data and channel not quantity of communication 670 miles per hour 186,000 miles per second

SPU Information Science Institute of Sripatum University 11 Electronic Communication Focus on device operations in such a way that data are buffered before transmitting at high speed (store and forward) Example of communication based on Store-and- forward teechnique: , voice mail, Facsimile, file transfer and WWW

SPU Information Science Institute of Sripatum University 12 Analog Data Continuous signal Change of frequency (oscillation) as sine wave Example of analog data: music from record player, which the record of sine-wave signals from a microphone

SPU Information Science Institute of Sripatum University 13 Analog Signaling Signals in sine-wave form time (sec) amplitude (volts) 1 cycle frequency (hertz) = cycles per second

SPU Information Science Institute of Sripatum University 14 Analog Terms Cycle : change of wave for one cycle in a unit of time Wave frequency: number of cycles of wave per unit time Wave amplitude: height of wave Hertz: number of frequency per second

SPU Information Science Institute of Sripatum University 15 Analog Signaling

SPU Information Science Institute of Sripatum University 16 Digital Data Represent data with symbols such as 1 or 0 when there is a change in electrical signal Transmission rate of communication channel in bit per second, e.g a modem has transmission rate at 56 Kbit / sec. (56 * 1000 bps) Data represented by binary digit (0, 1) data 0, 1 represented by the level of electrical voltage in a period of time

SPU Information Science Institute of Sripatum University 17 Digital Terms Bit: came from Binary Digit 1 is 1 in decimal system 10 is 2 decimal system is 153 decimal system Byte consists of 8 bits

SPU Information Science Institute of Sripatum University Number of bits and the value they represent Number of bitsNumber of outcomes Typical use 12Basic unit of information 416Hexadecimal digit 7128IRA character without parity 8256Byte: character with parity Number of bytes in a kilobyte of storage Number of bits in a kilobyte of storage Address size in older computer Number of bytes in a megabyte of storage Number of bits in a megabyte of storag x 10 9 Modern address size 2 63 = 9,223,372,036,854,775,808  ล้าน ล้าน ล้าน

SPU Information Science Institute of Sripatum University 19 Unit of data Storage Term Number of bytes Kilobyte Megabyte Gigabyte Terabyte Petabyte KB MB TB GB PB 1 thousand 1 million 1 billion 1 trillion 1 quadrillion Abbreviation

SPU Information Science Institute of Sripatum University 20 audio VIViD Voice Image Video Data text Graphics video

SPU Information Science Institute of Sripatum University 21 Character representation in digital system Represents electrical pulse with 1 and 0 Represents any character in binary, e.g. Morse code : dots and dashes Represents character with ASCII code

SPU Information Science Institute of Sripatum University 22 ASCII Character Codes A character is represented by 8 bits 8 bits of 0 and1 can represent 256 characters (0-255) Special characters has values between 128 – 255 Table of ASCII code

SPU Information Science Institute of Sripatum University 23 Example Assume that a page of paper has 27 line of text and each line contains up to 65 characters. Each character is represented by an ASCII code (8 bits). How long will it take to send a page of message via a modem at the speed of 56,000 bps and 256Kbps? 27*65*8/56000 = 14040/56000  0.25 seconds 27*65*8/ =  seconds

SPU Information Science Institute of Sripatum University 24 Analog audio transmission Transmits into receiving devices such as a microphone Microphone receives wave signals and transform to electrical signal according to the strength of the signals (amplitude of the signal wave) or changes o signal frequency (low/high frequencies) Examples of frequency generated from audio signal  Telephone: 3000Hz  Hi-Fi system: 15,000 Hz;  Compact Disc system: 20,000 Hz

SPU Information Science Institute of Sripatum University 25 Digital audio transsmission Good quality sound: transmits sample amplitude at double speed of highest frequency (Nyquist Theorem) Measurement is samples per second (smp/sec) Quality of telephone sound is at 8000 smp/sec each sample is 8 bits 8 bits * 8000smp/sec = 64kbps to transmit Quality of CD audio is at smp/sec, each sample is 16 bits 16 bits * *2 smp/sec = 1.41 Mbps to transmit

SPU Information Science Institute of Sripatum University 26 Converting Images Image is a collection of pixels  more pixels -> high resolution Digital image created by assigning value to each piixel, which represented by a group of 0 and 1 ( 0 for light and 1 for dark)

SPU Information Science Institute of Sripatum University 27 Quality of image more pixels more quality (sharper image) more data compression  the less quality Compression ratio 10:1 to 20:1 e.g. replacing 10 pixels with same value of 1 pixel reduces sharpness of the image less compression  more time to transmit than high compression user must trade off between quality of image and time for transmission

SPU Information Science Institute of Sripatum University 28 Example of a 100-pixel black and white image

SPU Information Science Institute of Sripatum University 29 Eight-Level Gray Scale 1 pixel is represented by 8 bits

SPU Information Science Institute of Sripatum University 30 Transmission time for sending an image

SPU Information Science Institute of Sripatum University 31 Video Communication Composed of a series of continuous images during a period of time Same principle as image but requires more transmission time for series of images Requires high channel capacity to satisfy specific application May need compression to respond to required transmission rate of image (frame/sec)

SPU Information Science Institute of Sripatum University 32 Next Lecture: Computer network and network taxonomy