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DATA NETWORKING : :
IINTRODUCTIONNTRODUCTION & P& PHYSICALHYSICAL LLAYERAYER
Dr. 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
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
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SSIMPLEXIMPLEX TTRANSMISSIONRANSMISSION
Dedicated Sender
Dedicated Receiver
Example
AM/FM Radio
8
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HHALFALF--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
Multimedia Communication (Voice/Data) TELECONFERENCE
Transmission Direction
Simplex
Half-Duplex
Full-Duplex
Transmission Media/NetworkWireless/Cellular Network
Twisted-Pair /Telephone Network
Both/ Computer Network
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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
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COMMUNICATIONCOMMUNICATION CCOMPONENTSOMPONENTS
Sender Receiver
Media
Data
Protocol
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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
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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
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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
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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
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PHYSICAL LAYER : OVERVIEW
Formatting and transmission of baseband signals
From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
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ANALOG TO DIGITAL
Formatting and transmission of baseband signals
From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
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TEXT TO BINARY (TEXTBITS)
ASCII Code: Seven-bit American standard code for information interchange
From: Digital Communicatoins Fundamental and Applications by Bernard Sklar
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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.
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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 ประเภทอ่ืนๆ
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 Disc26
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
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
106 samples/sec, each encoded 10 bits:
100 Mbps data stream
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ENCODE (LINE CODING)
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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)
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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
Clock
NRZI
(non-return to zero
inverted)
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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
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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%
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
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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
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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 Cable
•Coaxial Cable
•Fiber Optic Cable
AIR50
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ELECTROMAGNETIC SPECTRUM
52
GUIDED TRANSMISSION MEDIA
Twisted Pair
Coaxial cable
Optical fiber
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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
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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
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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
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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
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60
COAXIAL CABLE
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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
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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
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COAXIAL CABLE CONNECTORS:
BNC BAREL Connector : extends the cable
BNC Terminator :
BNC T-Connector : connects the cable to the LAN card
63
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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.
65
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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
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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
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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