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DATA NETWORKING : : INTRODUCTION NTRODUCTION & P & PHYSICAL HYSICAL LAYER AYER Dr. Nawaporn Wisitpongphan Email: [email protected] 1

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  • DATA NETWORKING : :

    IINTRODUCTIONNTRODUCTION & P& PHYSICALHYSICAL LLAYERAYERDr. Nawaporn Wisitpongphan

    Email: [email protected]

    1

  • 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)

    Research in Data Networking: NS-2

    TOOL CISCO Packet Tracer 2

  • CLASS SCHEDULE

    Week Topics Note

    Wk1 Jun 13 Intro + Physical Layer

    Wk2 Jun 20 Data Link Layer: Error Control/ Flow Control Q: Physical L

    Wk3 Jun 27 Data Link Layer: MAC Protocols NS-2 Project

    Wk4 Jul 4 Network Layer: IP Addressing Q: Data Link L

    Wk5 Jul 11 Survey of MAC Protocols Presentation

    Wk6 Jul 18 IP Addressing + Subnet

    Jul Jul 2929--44 MidtermMidterm

    Wk8 Aug 8 Packet Tracer/LAB: Subnet

    Wk9 Aug 15 Network Layer: Routing Algorithm NS-2 Progress

    Wk10 Aug 22 Network Layer: Routing Protocol Q: Routing Alg.

    Wk11 Aug 29 Packet Tracer/LAB: Router Configuration

    Wk12 Sep 5 Transport Layer: UDP vs. TCP

    Wk13 Sep 12 Application Layer Q: UDP vs. TCP

    Wk14 Sep 19 Packet Tracer: Exam

    Sep 24 Sep 24 Oct Oct 44 FinalFinal NS-2 Report3

  • GRADING:

    Final Exam. 30%

    Mid-term Exam. 30%

    Report/Homework 30%

    Class Participation 10%

    4

  • REFERENCE & OFFICE HOUR

    Computer Networking: A Top-Down Approach Featuring the Internet 3rd

    edition, James F. Kurose & Keith W. Ross, Addison Wesley

    Computer Network 3rd edition, Andrew S. Tanenbaum, Prentice Hall

    Computer Network: A System Approach 2nd edition, Larry L. Peterson and Bruce S. Davie, Morgan Kaufmann

    CISCO online material

    http://cisco.netacad.net/

    Thursday: 5-6 pm

    By Appointment

    [email protected]

    Reference Office Hour

    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

  • 8SSIMPLEXIMPLEX TTRANSMISSIONRANSMISSION

    Dedicated Sender

    Dedicated Receiver

    Example

    AM/FM Radio

    8

  • 9HHALFALF--DDUPLEXUPLEX TRANSMISSIONTRANSMISSION

    Each network entity can send and receive

    One direction at a time Either send or receive

    Example

    Walky-Talky9

  • 10

    FFULLULL--DDUPLEXUPLEX TRANSMISSIONTRANSMISSION

    Network entity can both send/receive simultaneously

    Both direction at a time

    Example Telephone / Cellphone

    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/NetworkWireless/Cellular Network

    Twisted-Pair /Telephone Network

    Both/ Computer Network

    11

  • 12

    CCOMMUNICATIONOMMUNICATION CCOMPONENTSOMPONENTS

    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

  • 13

    COMMUNICATIONCOMMUNICATION CCOMPONENTSOMPONENTS

    Sender Receiver

    Media

    Data

    Protocol

    13

  • LAYERING: THE OSI MODEL

    Session

    Network

    Link

    PhysicalPhysicalPhysical

    Application

    Presentation

    Transport

    Network

    Link Link

    Network

    Transport

    Session

    Presentation

    Application

    Network

    Link

    Physical

    Peer-layer communication

    layer-to-layer communication

    Router Router

    1

    2

    3

    4

    5

    6

    7

    1

    2

    3

    4

    5

    6

    7

    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

    Application Layer

    All functions between transport layer and

    the application program

    Same as in OSI Model

    5 Application

    4. Transport

    3. Network

    2 Data Link

    1. Physical

    17

  • PHYSICAL LAYER : OVERVIEW

    Formatting and transmission of baseband signals

    From: Digital Communicatoins Fundamental and Applications by Bernard Sklar

    18

  • ANALOG TO DIGITAL

    Formatting and transmission of baseband signals

    From: Digital Communicatoins Fundamental and Applications by Bernard Sklar

    19

  • TEXT TO BINARY (TEXTBITS)

    ASCII Code: Seven-bit American standard code for information interchange

    From: Digital Communicatoins Fundamental and Applications by Bernard Sklar

    20

  • GROUP OF BITSSYMBOL

    A group of k bits can be combined to form M

    symbols such that

    M = 2k

    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 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

    Nyquist Sampling Theorem: an analog signal that has beensampled can be perfectly reconstructed from the samples if the samplingrate exceeds 2B samples per second, where B is the highest frequency in theoriginal signal.

    Sampling

    rate?

    Nyquist Capacity: Given a channel with bandwidth B, a signal through this channel can have max symbol Rate Dmax < 2B (symbols/sec)

    Rmax = Dmax* log2M

    Rmax < 2B* log2M

    Rmax is called the channel capacity 1 symbol = log2M bits27

  • QUANTIZE

    28

  • SAMPLING QUANTIZING

    29

  • LETS 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

    106 samples/sec, each encoded 10 bits:

    100 Mbps data stream

    30

  • ENCODE (LINE CODING)

    31

  • 32

    NON-RETURN TO ZERO (NRZ) 1 high signal; 0 low signal

    Or some books say 1 low signal; 0 high signal.

    0 0 1 0 1 0 1 1 0

    Clock

    Does not posses any clocking component for ease of synchronization. Is not Transparent. Long string of zeros causes loss of synchronization.

    NRZ

    (non-return to zero)

    32

  • 33

    NON-RETURN TO ZERO INVERTED (NRZI)

    1 make transition; 0 stay at the same level

    Can recover from the long string of 1s but not long string of 0s

    0 0 1 0 1 0 1 1 0

    Clock

    NRZI

    (non-return to zero

    inverted)

    33

  • 34

    MANCHESTER

    1 high-to-low transition; 0 low-to-high transitionbOr 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

    Clock

    Manchester

    34

  • 35

    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 0s

    Use NRZI to encode the 5 bit codes

    Efficiency is 80%

    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

    4-bit 5-bit 4-bit 5-bit

    35

  • 36

    OOTHERTHER WWAYSAYS OFOF EENCODINGNCODING

    36

  • HOMEWORK!!!

    1. Convert 100100011 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

  • HOMEWORK

    3. Consider the BMC code in the figure:

    a) Explain how BMC code work?

    b) Is the BMC code given in Figure 2 a good or bad code? Why?

    c) Convert string 100100011 using BMC code. 38

  • WORKSHEET PROBLEM 1

    1 0 0 1 0 0 0 1 1

    Clock

    NRZ 0

    NRZI 0

    Bipolar 0

    39

    Pseudoternary0

  • Clock

    WORKSHEET PROBLEM 2

    1 0 0 1 0 0 0 1 1

    Differential

    Manchester 0

    Manchester 0

    BMC 0

    40

  • MODULATING

    41

  • 42

    ANALOG ENCODING OF DIGITAL DATA: MODULATION

    modulates a carrier signal A*sin(2pfct +f ) =

    ASK change A

    FSK changes f

    PSK change f

  • BPSK BINARY PHASE SHIFT KEYING

    Constellation Diagram43

  • QPSK- QUADRATURE PHASE-SHIFT

    KEYING

    44

  • QPSK SYSTEMS: SENDER/ RECEIVER

    45

  • 8-PSK

    46

  • 16 QAM

    47

  • 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

    48

  • DATA CARRYING CAPACITY

    THROUGHPUT VS. GOODPUT

    49

  • TRANSMISSION MEDIA

    Transmission Media

    Guided

    (wired)

    Unguided

    (wireless)

    Twisted Pair Cable

    Twisted Pair CableCoaxial CableFiber Optic Cable

    AIR50

  • 51

    ELECTROMAGNETIC SPECTRUM

  • 52

    GUIDED TRANSMISSION MEDIA

    Twisted Pair

    Coaxial cable

    Optical fiber

    52

  • 53

    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

    53

  • 54

    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 (250MHz)

    Limited data rate (1000Mbps)

    Susceptible to interference and noise

    54

  • 55

    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

    55

  • 56

    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)

    56

  • 57

    UTP CATEGORIES

    Cat 3 up to 16MHz Data Rate up to 10 Mbps Voice grade found in most offices Twist length of 7.5 cm to 10 cm

    Cat 4 up to 20 MHz Used for 10BaseT, 100BaseT networks

    Cat 5 up to 100MHz Used for 10BaseT, 100BaseT, and 1000BaseT networks Commonly pre-installed in new office buildings Twist length 0.6 cm to 0.85 cm

    Cat 6 Bandwidth = 250MHz

    Distance ~ 100 m and use in 10BaseT-1000BaseT networks

    Bandwidth = 500 MHz Distance ~ 55 m and normally use for10GBaseT networks

    57

  • STRAIGHT-THROUGH, CROSSOVER,

    ROLLOVER

    58

  • 59

  • 60

    COAXIAL CABLE

    60

  • 61

    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

    61

  • 62

    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

    62

  • 63

    COAXIAL CABLE CONNECTORS:

    BNC BAREL Connector : extends the cable

    BNC Terminator :

    BNC T-Connector : connects the cable to the LAN card

    63

  • 64

  • 65

    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.

    65

  • 66

    OPTICAL FIBER - TRANSMISSION

    CHARACTERISTICS

    66

  • OPTICAL FIBER BENEFITS & APPLICATIONS

    67

    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

    Benefits Applications

  • WHAT TYPE OF CABLE IS THIS?

    Twisted Pair Cable

    10BaseT (10 Mbps)

    100 BaseT (100 Mbps)

    Cannot be connect for more than 100 meters

    RJ4568

  • WHICH ONE IS 10BASE2 ?

    WHICH ONE IS 10BASE5 ?

    Coaxial Cable used in Bus Network 10 = 10Mbps

    2 = 200 meters

    5 = 500 meters

    Thinnet

    Thicknet

    69

  • 70

    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)

    70

  • 71

    LINE OF SIGHT PROPAGATION

    71

  • 72

    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)72

  • 73

    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

    Height of 35,784km (22,300 mi)

    Usage

    Television

    Long distance telephone

    Private business networks 73

  • 74

    SATELLITE POINT TO POINT LINK

    74

  • 75

    SATELLITE BROADCAST LINK

  • 76

    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) 76

  • 77

    INFRARED

    Characteristics:

    Modulate noncoherent infrared light

    Line of sight (or reflection)

    Can be blocked by walls

    Usages:

    TV remote control, IRD port