1 DATA NETWORKING : INTRODUCTION & PHYSICAL LAYER Dr. Nawaporn Wisitpongphan Email: nawapornn@kmutnb.ac.th
WHAT WILL WE STUDY??? Sender/Receiver Components Transmission Media Telephone/Cable Line Wireless link Satellite link Data: Compression/Protection/Transmission Technique Coding FEC (Forward Error Correction) Modulation/Demodulation Protocol: MAC (Medium Access Control) Routing Protocol Transport Protocol (TCP/ UDP) New Technologies: Bluetooth, WiFi, ZigBee, etc. TOOL CISCO Packet Tracer 2
CLASS SCHEDULE Week Topics Note Wk1 Jun 14 Intro + Physical Layer Wk2 Jun 21 Data Link Layer: Error Control/ Flow Control Q: Physical L Wk3 Jun 28 Data Link Layer: MAC Protocols Wk4 Jul 5 Network Layer: IP Addressing Q: Data Link L Wk5 Jul 12 Wk6 Jul 19 Self-Study (Packet Tracer Subnet) LAB: Subnet Jul 23-2828 Midterm Wk8 Aug 9 Network Layer: Routing Algorithm Wk9 Aug 16 Network Layer: Routing Protocol Q: Routing Alg. Wk10 Aug 23 Wk11 Aug 30 Packet Tracer: Router Configuration Transport Layer: UDP vs. TCP Wk12 Sep 6 Application Layer Q: UDP vs. TCP Wk13 Sep 13 Modern Network Technology: Presentation Presentation Wk14 Sep 20 Sep 24 Oct 5 Packet Tracer: Exam Final 3
GRADING: Final Exam. 30% Mid-term Exam. 30% Report/Homework 30% Class Participation 10% 4
REFERENCE & OFFICE HOUR Reference Office Hour Computer Networking: A Top-Down Approach Featuring the Internet 3 rd edition, James F. Kurose & Keith W. Ross, Addison Wesley Computer Network 3 rd edition, Andrew S. Tanenbaum, Prentice Hall Thursday: 5-6 pm By Appointment nawapornn@kmutnb.ac.th Computer Network: A System Approach 2 nd edition, Larry L. Peterson and Bruce S. Davie, Morgan Kaufmann CISCO online material http://cisco.netacad.net/ 5
2-IN-1 LECTURE: ---- THE OUTLINE --- Intro Transmission Techniques Telecommunication Data Networking OSI Layers Physical Layer Sampling Quantization Modulation Transmission Media Supplemental Reading: CCNA 1 Chapter 8 6
WHAT IS TELECOMMUNICATION? Systems used in transmitting messages over a long distance Voice Communication AM/FM Radio WALKY TALKY Telephone/Cell phone Notice any differences? Transmission Direction Simplex Half-Duplex Full-Duplex 7
SIMPLEX TRANSMISSION Dedicated Sender Dedicated Receiver Example AM/FM Radio 8 8
HALF-DUPLEX TRANSMISSION Each network entity can send and receive One direction at a time Either send or receive Example 9 Walky-Talky 9
FULL-DUPLEXUPLEX TRANSMISSION Network entity can both send/receive simultaneously Both direction at a time Example Telephone / Cellphone 10 10
WHAT IS TELECOMMUNICATION? Systems used in transmitting messages over a long distance Voice Communication AM/FM Radio WALKY TALKY TELEPHONE CELLPHONE Data Communication PAGER FAX E-MAIL Multimedia Communication (Voice/Data) TELECONFERENCE Transmission Direction Simplex Half-Duplex Full-Duplex Transmission Media/Network Wireless/Cellular Network Twisted-Pair /Telephone Network Both/ Computer Network 11
COMMUNICATION COMPONENTS Sender: Transmitting Device transmitting data to the destinations Receiver: Receiver Device receives transmitted data Data: Voice, Messages, Image, etc. Media: Means by which a communications signal is carried from one system to another, i.e., twisted pair wires, fiber optic, air, Protocol: Rules determining the format and transmission of data 12 12
COMMUNICATION COMPONENTS Sender Receiver Protocol Media Data 13 13
LAYERING: THE OSI MODEL 7 6 5 4 3 2 1 Application Presentation Session Transport Network Link Physical layer-to-layer communication Peer-layer communication Router Router Network Network Link Link Physical Physical Application Presentation Session Transport Network Link Physical 7 6 5 4 3 2 1 14
OSI 7- LAYER MODEL I Physical Layer The physical devices Media Representation of Data (Bits) Data Link Layer Message Framing Error Control Media Access Control Flow Control Network Layer Addressing and Routing decision Transport Layer End-to-End flow and congestion control 7 Application 6 Presentation 5 Session 4. Transport 3. Network 2 Data Link 1. Physical 15
OSI 7-LAYER MODEL II Session Layer Initiate, maintain, and terminate logical session between sender/receiver Presentation Layer Format data from user for transmission Format data received for user Provide data interfaces, compression, translation between different data formats Application Layer Application Programming Interface (API) 7 Application 6 Presentation 5 Session 4. Transport 3. Network 2 Data Link 1. Physical 16
INTERNET 5-LAYER MODEL Physical Layer Data Link Layer Network Layer Transport Layer Same as in OSI Model 5 Application 4. Transport 3. Network 2 Data Link Application Layer All functions between transport layer and the application program 1. Physical 17
PHYSICAL LAYER : OVERVIEW Formatting and transmission of baseband signals 18 From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
ANALOG TO DIGITAL Formatting and transmission of baseband signals 19 From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
TEXT TO BINARY (TEXT BITS) ASCII Code: Seven-bit American standard code for information interchange 20 From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
GROUP OF BITS SYMBOL A group of k bits can be combined to form M symbols such that M = 2 k The symbol set of size M is called M-ary system Example: k = 1 2-ary system or binary system 21
THINK IN A BINARY FORM Message bit Symbol Waveform 22
SAMPLING & QUANTIZING Amplitude and time coordinates of source data. (a) Original analog waveform. (b) Natural-sampled data. (c) Quantized samples. (d) Sample and hold. 23
SAMPLE 24
SAMPLING THEOREM Undersampling More samples allow for better signal recovery 25
SAMPLING THEOREM: EXAMPLE Audio (MP3) 32 kbps AM Quality 96 kbps FM Quality 128 kbps Standard Quality 224 320 kbps Near CD quality Audio ประเภทอ นๆ 800 bps Recognizable speech 8 kbps Telephone quality Video 16 kbps videophone quality (General) 128 384 kbps vdo conferencing (Business) 1.25 Mbps VCD quality 5 Mbps DVD quality 8 15 Mbps HDTV quality 29.4 Mbps HD DVD 40 Mbps Blu-ray Disc 26
NYQUIST THEOREM Sampling rate? Nyquist Sampling Theorem: an analog signal that has been sampled can be perfectly reconstructed from the samples if the sampling rate exceeds 2B samples per second, where B is the highest frequency in the original signal. Nyquist Capacity: Given a channel with bandwidth B, a signal through this channel can have max symbol Rate D max < 2B (symbols/sec) R max = D max * log 2 M R max < 2B* log 2 M R max is called the channel capacity 1 symbol = log 2 M bits 27
QUANTIZE 28
SAMPLING QUANTIZING 29
LET S PUT THINGS TO THE PERSPECTIVE Voice: 4 KHz requires 8000 sample per second Quantization: Sample encoded by 7 bit number 8000 samples/sec of 7 bits each 56kbps data stream Color TV channel: about 5 MHz analog data 10 6 samples/sec, each encoded 10 bits: 100 Mbps data stream 30
ENCODE (LINE CODING) 31
NON-RETURN TO ZERO (NRZ) 1 high signal; 0 low signal Or some books say 1 low signal; 0 high signal. Does not posses any clocking component for ease of synchronization. Is not Transparent. Long string of zeros causes loss of synchronization. 0 0 1 0 1 0 1 1 0 NRZ (non-return to zero) Clock 32 32
NON-RETURN TO ZERO INVERTED (NRZI) 1 make transition; 0 stay at the same level Can recover from the long string of 1 s but not long string of 0 s 0 0 1 0 1 0 1 1 0 NRZI (non-return to zero inverted) Clock 33 33
MANCHESTER 1 high-to-low transition; 0 low-to-high transition bor some books say 1 low-to-high transition; 0 high-to-low transition Solve Clock skew problem Disadvantages signal transition rate doubled Because of the greater number of transitions it occupies a significantly large bandwidth. Efficiency = 50% 0 0 1 0 1 0 1 1 0 Manchester Clock 34 34
4-BIT/5-BIT (100MB/S ETHERNET) Goal: address inefficiency of Manchester encoding, while avoiding long periods of low signals Solution: Use 5 bits to encode every sequence of four bits such that no 5 bit code has more than one leading 0 and two trailing 0 s Use NRZI to encode the 5 bit codes Efficiency is 80% 4-bit 5-bit 4-bit 5-bit 0000 11110 0001 01001 0010 10100 0011 10101 0100 01010 0101 01011 0110 01110 0111 01111 1000 10010 1001 10011 1010 10110 1011 10111 1100 11010 1101 11011 1110 11100 1111 11101 35 35
OTHER WAYS OF ENCODING 36 36
HOMEWORK!!! 1. Convert 10010011100010101 using the following codes: a) NRZ b) NRZI c) Manchester 2. Explain how each of these codes work and convert the bit stream in problem 1 a) Bipolar or AMI b) Pseudoternary c) Differential Manchester 37
WORKSHEET PROBLEM 1 1 0 0 1 0 0 1 1 1 0 0 0 1 0 1 0 1 Manchester 0 NRZI 0 NRZ 0 Clock 38
WORKSHEET PROBLEM 2 1 0 0 1 0 0 1 1 1 0 0 0 1 0 1 0 1 Bipolar 0 Pseudoternary 0 Differential Manchester 0 Clock 39
MODULATING 40
ANALOG ENCODING OF DIGITAL DATA: MODULATION modulates a carrier signal A*sin(2pf c t +f ) = ASK change A FSK changes f PSK change f 41
BPSK BINARY PHASE SHIFT KEYING Constellation Diagram 42
QPSK- QUADRATURE PHASE-SHIFT KEYING 43
QPSK SYSTEMS: SENDER/ RECEIVER 44
8-PSK 45
16 QAM 46
DATA CARRYING CAPACITY: BANDWIDTH Measure the amount of information that can flow from one place to another in a given amount of time Depend on Properties of the physical media Technology chosen for signaling and detecting network signals 47
DATA CARRYING CAPACITY THROUGHPUT VS. GOODPUT 48
TRANSMISSION MEDIA Transmission Media Guided (wired) Unguided (wireless) Twisted Pair Cable Coaxial Cable Fiber Optic Cable AIR 49
ELECTROMAGNETIC SPECTRUM 50
GUIDED TRANSMISSION MEDIA Twisted Pair Coaxial cable Optical fiber 51 51
TWISTED PAIR - APPLICATIONS Most common medium Telephone network Between house and local exchange (subscriber loop) Within buildings To private branch exchange (PBX) For local area networks (LAN) 10Mbps or 100Mbps 52 52
TWISTED PAIR - TRANSMISSION CHARACTERISTICS Analog Amplifiers every 5km to 6km Digital Use either analog or digital signals repeater every 2km or 3km Limited distance Limited bandwidth (1MHz) Limited data rate (100Mbps) Susceptible to interference and noise 53 53
NOISES & NEAR END CROSSTALK Coupling of signal from one pair to another Coupling takes place when transmit signal entering the link couples back to receiving pair, i.e. near transmitted signal is picked up by near receiving pair 54 54
UNSHIELDED AND SHIELDED TP Unshielded Twisted Pair (UTP) Ordinary telephone wire Cheapest Easiest to install Suffers from external EM interference Shielded Twisted Pair (STP) Metal braid or sheathing that reduces interference More expensive Harder to handle (thick, heavy) 55 55
UTP CATEGORIES Cat 3 up to 16MHz Voice grade found in most offices Twist length of 7.5 cm to 10 cm Cat 4 up to 20 MHz Cat 5 up to 100MHz Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm 56 56
STRAIGHT-THROUGH, CROSSOVER, ROLLOVER 57
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COAXIAL CABLE 59 59
COAXIAL CABLE APPLICATIONS Most versatile medium Television distribution Ariel to TV Cable TV Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic Short distance computer systems links Local area networks 60 60
COAXIAL CABLE - TRANSMISSION CHARACTERISTICS Analog Amplifiers every few km Closer if higher frequency Up to 500MHz Digital Repeater every 1km Closer for higher data rates 61 61
COAXIAL CABLE CONNECTORS: BNC BAREL Connector : extends the cable BNC Terminator : BNC T-Connector : connects the cable to the LAN card 62 62
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OPTICAL FIBER Made up of The core: carries the light pulses The cladding: reflects the light pulses back into the core) The buffer coating: protects the core and cladding from moisture, damage, etc. 64 64
OPTICAL FIBER - TRANSMISSION CHARACTERISTICS 65 65
OPTICAL FIBER BENEFITS & APPLICATIONS Benefits Applications Greater capacity Data rates of hundreds of Gbps Smaller size & weight Lower attenuation Electromagnetic isolation Greater repeater spacing 10s of km at least Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops LANs 66
WHAT TYPE OF CABLE IS THIS? 67 Twisted Pair Cable 10BaseT (10 Mbps) 100 BaseT (100 Mbps) Cannot be connect for more than 100 meters RJ45
WHICH ONE IS 10BASE2? WHICH ONE IS 10BASE5? Thinnet Thicknet 68 Coaxial Cable used in Bus Network 10 = 10Mbps 2 = 200 meters 5 = 500 meters
WIRELESS PROPAGATION Signal travels along three routes Ground wave Follows contour of earth Up to 2MHz AM radio Sky wave Amateur radio, BBC world service, Voice of America Signal reflected from ionosphere layer of upper atmosphere (Actually refracted) 69 69
LINE OF SIGHT PROPAGATION 70 70
UNGUIDED MEDIA: TERRESTRIAL MICROWAVE Characteristics Parabolic dish as transmitting/receiving devices Operate at low GHz band (4-6 GHz and 21-23 GHz) Focused beam (narrow and highly directional) Line of sight (Transmitter and Receivers must be adjusted carefully so that they are aligned) Susceptible to atmospheric interference Vulnerable to eavesdropping so often the signal is encrypted. Usage: Long haul telecommunications (Telephone Relay Tower) 71 71
SATELLITE MICROWAVE Characteristics: Satellite is relay station Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency Requires geo-stationary orbit Usage Height of 35,784km (22,300 mi) Television Long distance telephone Private business networks 72 72
SATELLITE POINT TO POINT LINK 73 73
SATELLITE BROADCAST LINK 74
BROADCAST RADIO Characteristics: Omnidirectional Line of sight Transmission Suffers from multipath interference Reflections Usages: AM/FM radio UHF and VHF television UHF (300 MHz and 3 GHz ) VHF (30 MHz to 300 MHz) 75 75
INFRARED Characteristics: Modulate noncoherent infrared light Line of sight (or reflection) Can be blocked by walls Usages: TV remote control, IRD port 76