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CPE 426 Computer Networks

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Title: CPE 426 Computer Networks


1
CPE 426 Computer Networks
  • Week 1 Introduction
  • Review 1
  • Data Communications

2
Course Outlines
  • ???? Sheet
  • ?????? Download ???
  • http//cpe.rsu.ac.th/ut

3
TOPICS
  • 1. Communication/NW Model
  • Ch.5.1-5.5
  • 2. Communication Protocols OSI and TCP/IP
  • Ch.1.1-1.10
  • 3. Communication/NW Topology
  • Ch. 13.8

4
TOPICS
  • 4. Signal/Power/Loss
  • Ch.6.1-6.10
  • 5. Data Coding(Line Coding)
  • Ch.6.11-6.20
  • 6. Trasmission Media/Noise/Channel Capacity
  • Ch.7.1-7.10 7.20-7.22

5
TOPICS
  • 7. Multiplexing DSL
  • Ch.11.1-11.3 12.1-12.7
  • 8. Asynchronous Communication
  • Ch.9.1-9.8
  • 9. Synchronous Communication
  • Ch.9.9-9.13

6
TOPICS
  • 10. Flow Control/Error Control/ARQ
  • Ch. 8.12-8.15
  • 11. Circuit vs Packet Switching NW
  • Ch. 3.1-3.5 13.1-13.5
  • ALSO Reference From CPE 326 (Stalling Book)

7
?????????? ?????????? 2 Entity
Destination ?????? ???? ?????????????
Sender Source ?????? ?????????????????????
Transmitter
Receiver
Signal ??????
DATA
DATA
Transmission Medium
8
Data comm.Model ?? 5 ????
Destination ?????? ???? ?????????????
Sender Source ?????? ?????????????????????
Transmitter
Receiver
Signal ??????
DATA
DATA
ABC
ABC
01011
01011
ADC
Transmission Medium
Plus Error
File ABCD ? Data Coding/Compression (ASCII,
EBCDIC/ZIP) 010110001101.
Wire/Wireless
Loss and Noise
Decodine/Demodulation Demultiplexing
Line Coding/Modulation Plus Multiplexing
9
ASCII Code
  • American Standard Code for Information
    Interchange
  • ASCII includes definitions for 128 characters 33
    are non-printing control characters (now mostly
    obsolete) that affect how text and space is
    processed 94 are printable characters, and the
    space is considered an invisible graphic. The
    most commonly used character encoding on the
    World Wide Web was US-ASCII until December 2007,
    when it was surpassed by UTF-8

10
Mode ?????????????
  • Data Communication Model ?????????????????????????
    ??????????
  • ??????????????????????????? ?????? Transmission
    Medium ???????
  • Simplex
  • ?????? Transmission ???????????
  • Duplex
  • ???????????????????????????
  • Full-Duplex
  • ???????????????????????????
  • Half-Duplex

11
Simplex ????????????? 4-wire Duplex
Destination
Source
Rx
Tx
Transmission Medium
Source
Destination
Tx
Rx
Transmission Medium
12
Duplex
Destination
Source
Rx
Tx
Source
Destination
Tx
Rx
Transmission Medium
Half-Duplex
Destination
Source
Tx/Rx
Tx/Rx
Source
Destination
Transmission Medium
Full-Duplex
13
??????????????????????????? 2 ??
  • ???????(Duplex)????????????????????????????????
    Full Mesh Topology

B
C
????????? n(n-1)/2 O(n2)
A
D
????????????? n ???????? O(n2)
F
E
Topology ?????? Network ??????????????????????????
?????????????????????
14
?????????? Share Medium ????? Multiple Access
Control
  • ?? LAN ????? Topology 3 ???????????
  • Bus (??? Tree), Ring, Star

hub
15
?????????? Share Medium ????? Multiple Access
Control
  • ?? WAN ????????? Partial Mesh
  • Medium ????????????? Statistical Time Division
    Multiplexing ????????

Intermediate Node Switching/Routing Node
C
A
D
B
End Node
E
H
F
G
16
??? Share Medium
  • ??????????????? Medium Access Control
  • End Node ???????????????????????? Address
    ????????????? ????????? Circuit Number
  • Intermediate Node ????????????????????????????????
    ?????????????????????????(Forwarding)
  • ???????
  • 1. Data ?????????????????????? (Header)
    ?????????????????? Address ?????? Control
    ???????????????????? Encapsulation
    ????????????????????? Frame
  • 2. ?????????????? Frame ??????????????????????????
    ???????????????? (Error Detection) ????????? CRC
    Code ????? Frame Check Sequence(FCS)
  • 3. ???????????? Header ??????? FCS
    ???????????????????????????????????????????????
    Frame (Frame Delimiter Pre-amble/Post-amble)
  • 4. ???????????????????????????????????????????????
    ???????????? ???????????? Protocol ?????????????

17
LAN vs WAN Technologies
  • LAN ??????????? Share Medium ??? Contention
    ????????????????????????????????? Multiple Access
  • Topology ????????????? Bus, Ring, Star
  • WAN ?? Share Medium ??????? ??????????????????
    Synchronous Multiplexing (TDM) ?? Circuit
    Switching Network???? Statistical Multiplexing
    (????? Packet Switching Network)
  • Topology ????????????? Mesh Network ????????????
    Partial Mesh
  • Internetworking Technologies ?????????????????????
    ??????????? LAN ???? WAN Network
  • ?????????? Internet (IP Network)

18
Protocol and Protocol Architecture
  • Protocol ???????????????????????????????????
  • ??????????????????? ???? Standard
    ?????????????????????????????????????????????
  • ??????????
  • Syntax
  • Data formats ???????????????, ????, ???????????
  • Signal levels???????????????????????????
  • Semantics
  • Control information???????????????????
  • Error handling???????????? Error
  • Timing
  • Speed matching????????????????
  • Sequencing???????????????????

19
Protocol Architecture (Protocol Stack)
  • ???????????????????????????????????????????
    ??????????????????????????????? Module
  • ????? Module ????????????????????
  • ????? Module ????????????????????? Module ????
  • ????? Module ?? Protocol ?????
  • ??????????????????????? ????? Protocol Stack ????
    Protocol Architecture

20
Protocol Architecture (Protocol Stack)
  • Protocol Architecture ??????????????????????
  • 7 Layer OSI Reference Model ??? ISO
  • ???????????????????????? ?????????? Reference
  • TCP/IP Protocol Suite (?? 5 ????)
  • ????????????????????????
  • ?????????? Internet

21
7 Layer OSI Reference Model
22
7 Layer
  • Layer 1 Physical Layer
  • ?????????????????????? Physical Medium
    ?????????????????????????? ????????????
    Interface, ??????????? ,????????????????????? Bit
    Stream
  • Layer 2 Data Link Layer
  • ???????????????? Frame, ?????????????????????????
    ????? Link ?? Error Control, Flow Control ????
    Link
  • Layer 3 Network Layer
  • ??????????????????????????? Network,
    ??????????????, ???????????? Layer ?????????
    Network ???????? ????????????????????? Packet

23
7 Layer
  • Layer 4 Transport Layer
  • ??????????????????????????????????????????????????
    (End-to-End), ?????????????? Error ??? Flow
    Control ???????????????????????
    ????????????????????????? Segment
  • Layer 5 Session Layer
  • ???????????????? ???? ????????????(Connection)
    ??????? Application????????????????
    ?????????????????????????????? Session

24
7 Layer
  • Layer 6 Presentation Layer
  • ?????????????????????????? Format ????????? ?????
    Encryption ??????????? Data Compression
    ????????????????????????????
  • Layer 7 Application Layer
  • ????????????????????? Application ?????????

25
OSI Environment
26
???????????????? Router
27
TCP/IP Protocol Architecture
  • Developed by the US Defense Advanced Research
    Project Agency (DARPA) for its packet switched
    network (ARPANET)
  • Used by the global Internet
  • No official model but a working one.
  • Application layer
  • Host to host or transport layer
  • Internet layer
  • Network access layer
  • Physical layer

28
TCP/IP Protocol Architecture
Application
INTERNET
Transport Layer
Internet Layer
Network Access
Physical
29
Physical Layer
  • Physical interface between data transmission
    device (e.g. computer) and transmission medium or
    network
  • Characteristics of transmission medium
  • Signal levels
  • Data rates
  • etc.

30
Network Access Layer
  • Exchange of data between end system and network
  • Destination address provision
  • Invoking services like priority
  • ?????????????? TCP/IP ???????????????? Layer 1-2
  • ??????????? TCP/IP ???? WAN ???????? LAN ???
    Ethernet

31
Internet Layer (IP)
  • Systems may be attached to different networks
  • Routing functions across multiple networks
  • Implemented in end systems and routers
  • ??? IP Protocol
  • ????????????? Datagram

32
Transport Layer (TCP)
  • Reliable delivery of data
  • Ordering of delivery
  • ?????????? 2 Protocol
  • TCP Transport Control Protocol
  • Connection Oriented
  • Guarantee Delivery
  • UDP User Datagram Protocol
  • Connectionless
  • Best Effort

33
Application Layer
  • Support for user applications
  • e.g. http, SMPT

34
TCP/IP VS OSI
Application Software
NOS Window
NIC Driver
Physical Link
35
?????????????????????? TCP/IP
36
Addressing ?? TCP/IP
  • TCP Port ???? UDP Port 16 Bit
  • IP Address, IPv4 32 Bit ??????????????
    ?????????? Network
  • Physical Hardware Address
  • ?????? TCP/IP ?? Ethernet LAN ????????? Address
    ??? NIC ???? MAC Address 48 Bit

37
PDU Protocol Data Unit
TCP Segment
IP Packet / IP Datagram
Frame
38
Protocol ??????????? TCP/IP
39
Standard
  • LAN
  • IEEE 802
  • Ethernet IEEE 802.3 ????????????????
  • WLAN IEEE 802.11, 802.11b, 802.11g,
    802.11n,802.11i
  • PAN-Bluetooth IEEE 802.15
  • www.ieee.org
  • WAN
  • ????????? ??????????????????????? OSI (ITU)
  • TCP/IP
  • RFC Request for Comments
  • ???????? 4000 RFCs
  • www.faqs.org/rfcs

40
Physical Layer Basics
  • Signal, Power, Noise
  • Bandwidth ??????????????????
  • Channel Capacity
  • NyQuist
  • Shannon
  • SNR, Eb/No
  • BER

41
Signal, Power ??? Loss
  • ??????????????????????????????????????????????????
    ?????????? Medium ???
  • Medium Copper Wire Electrical Signal
  • Medium Air/Vacuum Radio Signal or Microwave or
    LASER
  • Medium Fiber Optic Light or LASER
  • ???????????????????????????????????????????????(dB
    W, dBm)
  • ????????????????????????????? SNR(dB) ???????
    Eb/No(dB)

42
???????????????? Decibel
????? (W)
???????? Power ??????????? ???
0
???????
????? (dBW)
???????????????????? ?????????????????????
0
???????
43
????????
  • ???? dB
  • P(dBW) 10log(P(W))
  • P(dBm) 10log(P(mW))
  • ????? Power ????????? ??????????? Loss(dB) ???
    Medium ???????? Power ??????????? Medium ??????
  • Power (dB) Power ??????(dB)- Loss ?? Medium
    (dB)
  • ???? dB ??????????? Power(Absolute) ??????
    Inverse Log
  • ????? dB ??? Power ???? dBW ??? dBm
  • ????? dB ??? Loss/Gain ?????? dB ????????
  • ???????????? ???? Gain ??????? Gain (dB)
    ??????????? Power (dB)

44
????????
  • ?????? 5 W ?????????????????? Loss 4 dB ??? 100
    ???? ???????????????????????? 750 ????
  • Power ?????? 10log5 6.9897 dBW
  • Loss ???????????? 4x750/100 30 dB
  • ???????????? 750 ???? 6.9897-30
  • -23.0103 dBW
  • ????????????????? Watt
  • P(W) 10(-23.0103/10) 5x10-3 W 5mW

45
Exercise ????????
  • ??????? Power ??????????

Gain 45 dB
Gain 50 dB
1.5 km
620 m
480 m
P?W
6W
Loss 4 dB/100 m
Loss 3 dB/100 m
Loss 3 dB/100 m
46
Transmission Impairment
  • ??????????????????????????
  • Attenuation (Loss)
  • Distortion
  • Delay Distortion
  • Noise
  • Crosstalk
  • Thermal Noise
  • Shot Noise
  • Noise from Environment

47
Delay Distortion
  • Only in guided media
  • Propagation velocity varies with frequency

48
Noise (1)
  • Additional signals inserted between transmitter
    and receiver
  • Thermal
  • Due to thermal agitation of electrons
  • Uniformly distributed
  • White noise
  • Intermodulation
  • Signals that are the sum and difference of
    original frequencies sharing a medium

49
Noise (2)
  • Crosstalk
  • A signal from one line is picked up by another
  • Impulse
  • Irregular pulses or spikes
  • e.g. External electromagnetic interference
  • Short duration
  • High amplitude

50
Thermal Noise, Thermal Equivalent, Effective
Noise Temperature
  • ????????????????? Molecule(Electron, Proton)
    ???????????????????????????
  • ?????????????????????? ????????????????(0 degree
    Kelvin -273.16 degree Celcius), ????????????
  • ???? White Noise, Gaussian Noise
  • ??????? Noise Power Density,
  • ????????????? White Noise, ???? Density
    ?????????????????
  • ??? Noise ????????????? Bandwidth ??????????????
  • ??????? Noise Power,
  • Ex. ??? Room Temp.(25 C)

51
Channel Capacity
  • Data rate
  • In bits per second
  • Rate at which data can be communicated
  • Bandwidth
  • In cycles per second of Hertz
  • Constrained by transmitter and medium
  • NyQuist Bandwidth and Shannon Channel Capacity

52
NyQuist Bandwidth
  • If rate of signal transmission is 2B then signal
    with frequencies no greater than B is sufficient
    to carry signal rate
  • Given bandwidth B, highest signal rate is 2B
  • Given binary signal, data rate supported by B Hz
    is 2B bps
  • Can be increased by using M signal levels
  • C 2B for Binary Signal(M2), Baud RateBit Rate
  • C 2B log2M ( M-ary Signal ), Baud Rate R/log2M
  • In case of No Noise C can be increased by
    increasing M

53
Shannon Capacity Formula
  • Consider data rate, noise and error rate
  • Faster data rate shortens each bit so burst of
    noise affects more bits
  • At given noise level, high data rate means higher
    error rate
  • Signal to noise ratio (in decibels, dB)
  • SNRdb10 log10 (signal power/noise power)
  • Capacity CB log2(1SNR), Shannon channel
    capacity, SNR is not in dB
  • This is error free capacity

54
Digital data rate and error rate
  • ?????? Analog Communication ????????????? SNR
    ???????????????????????????
  • ?????? Digital Communication ??????? Data Rate
    ????????? ??? Error Rate ???????????
    ??????????????????????????????
  • ??????? SNR ????????????????? Digital System
    ??????????????????????
  • ????????? Energy Per Bit/ Noise Energy(Eb/No)
  • ?????? ??????????? BER(Bit Error Rate)
    ???????????
  • B ???????? ???????? R ???????? Bandwidth
    Efficiency ??????? Eb/No ????? BER ?????????

55
BER and Eb/No
56
????????????????
  • Power in dBw
  • Power in dBm
  • Signal-to-Noise Ratio power of signal/power of
    noise
  • SNR(dB)
  • NyQuist Rate,
  • Shannon Channel Capacity,
  • Thermal Noise(Thermal Equivalent)
  • Noise Energy,
  • Noise Power,

57
Examples (??????????)
  • 1. ??????????????? Effective Noise Temperature
    ??????? 100 ?????????? ????? Bandwidth 10 MHz
    ???????????? Thermal Noise ???? dBW
  • 2. ?????????????????????? Spectrum ??????? 3 MHz
    ??? 4 MHz ???????? SNR 24 dB ?????????????????????
    ?? Data ?????????????????????????
    ?????????????????????????????????????
  • 3. ?????? BPSK(Binary Phase Shift Keying)
    ?????????? Eb/No ?????????? 8.4 dB ???????????
    BER ??????????? 1/10000 ?????? Effective Noise
    Temperature ?????????????? 290 K ??? Data Rate
    ????????????? 2400 bps ???????????????????????????
    ???????????????????

58
Example 1
  • 1. ??????????????? Effective Noise Temperature
    ??????? 100 ?????????? ????? Bandwidth 10 MHz
    ???????????? Thermal Noise ???? dBW

59
Example 2
  • 2. ?????????????????????? Spectrum ??????? 3 MHz
    ??? 4 MHz ???????? SNR 24 dB ?????????????????????
    ?? Data ?????????????????????????
    ?????????????????????????????????????
  • Shannon Channel Capacity,
  • B1 MHz,
  • a) ???????
  • ???
  • ??????
  • b)

60
Examples
  • 3. ?????? BPSK(Binary Phase Shift Keying)
    ?????????? Eb/No ?????????? 8.4 dB ???????????
    BER ??????????? 1/10000 ?????? Effective Noise
    Temperature ?????????????? 290 K ??? Data Rate
    ????????????? 2400 bps ???????????????????????????
    ???????????????????

61
Line Coding
  • ?????? Pulse ????????????? Data ????????
  • Pulse 2 ????? Binary Signal
  • M-ary Signal ????? M ?????
  • ???????????
  • Average DC ????????????????
  • Signal Transition ??????????

62
NRZ
63
Biphase
64
Biphase
  • Manchester
  • Transition in middle of each bit period
  • Transition serves as clock and data
  • Low to high represents one (??????????? Bit)
  • High to low represents zero (??????????? Bit)
  • Used by IEEE 802.3(Ethernet 10 Mbps)
  • Differential Manchester
  • Midbit transition is clocking only
  • Transition at start of a bit period represents
    zero
  • No transition at start of a bit period represents
    one
  • Note this is a differential encoding scheme
  • Used by IEEE 802.5(Token Ring)

65
Bipolar-AMIScrambling
66
Scrambling B8ZS vs HDB3
  • Bipolar With 8 Zeros Substitution
  • Based on bipolar-AMI
  • If octet of all zeros and last voltage pulse
    preceding was positive, encode as 000-0-
  • If octet of all zeros and last voltage pulse
    preceding was negative, encode as 000-0-
  • Causes two violations of AMI code
  • Unlikely to occur as a result of noise
  • Receiver detects and interprets as octet of all
    zeros
  • High Density Bipolar 3 Zeros
  • Based on bipolar-AMI
  • String of four zeros replaced with one or two
    pulses

Voltage ???????? ????? 1 ??? ????? 1 ???
- 000- 00
000 -00-
67
Multiplexing
  • ???????????????????????????????????????????
    Transmission Medium ????????
  • FDM Frequency Division Multiplexing
  • ???????????????? Bandwidth (???????????) ???????
  • TDM Time Division Multiplexing
  • ???????????????????????????????
  • ????????
  • Synchronous TDM ???????????? Channel ???????????
    ????????????? Channel ?????????????????????
  • Statistical TDM ???????? Channel ???????
    ??????????? ??????????????????????????? Channel
    ???????? ????????????????????????????????
    ???????? Channel ??????????

68
FDM vs TDM
69
Statistical TDM Frame Formats
70
Asymmetrical Digital Subscriber Line
  • ADSL
  • Link between subscriber and network
  • Local loop
  • Uses currently installed twisted pair cable
  • Can carry broader spectrum
  • 1 MHz or more

71
ADSL Design
  • Asymmetric
  • Greater capacity downstream than upstream
  • Frequency division multiplexing
  • Lowest 25kHz for voice
  • Plain old telephone service (POTS)
  • Use echo cancellation or FDM to give two bands
  • Use FDM within bands
  • Range 5.5km

72
ADSL Channel Configuration
73
Discrete Multitone
  • DMT
  • Multiple carrier signals at different frequencies
  • Some bits on each channel
  • 4kHz subchannels
  • Send test signal and use subchannels with better
    signal to noise ratio
  • 256 downstream subchannels at 4kHz (60kbps)
  • 15.36MHz
  • Impairments bring this down to 1.5Mbps to 9Mbps

74
DTM Bits Per Channel Allocation
75
Mode ??????????????? Digital
  • Timing problems require a mechanism to
    synchronize the transmitter and receiver
  • Two solutions
  • Asynchronous
  • Synchronous

76
Asynchronous Communicaton
  • Data transmitted on character at a time
  • 5 to 8 bits
  • Timing only needs maintaining within each
    character
  • Resynchronize with each character

77
Asynchronous (diagram)
78
Asynchronous - Behavior
  • In a steady stream, interval between characters
    is uniform (length of stop element)
  • In idle state, receiver looks for transition 1 to
    0
  • Then samples next seven intervals (char length)
  • Then looks for next 1 to 0 for next char
  • Simple
  • Cheap
  • Overhead of 2 or 3 bits per char (20)
  • Good for data with large gaps (keyboard)

79
Data Communications Interfacing
80
Characteristics of Interface
  • Mechanical
  • Connection plugs
  • Electrical
  • Voltage, timing, encoding
  • Functional
  • Data, control, timing, grounding
  • Procedural
  • Sequence of events

81
V.24/EIA-232-F
  • ITU-T v.24
  • Only specifies functional and procedural
  • References other standards for electrical and
    mechanical
  • EIA-232-F (USA)
  • RS-232
  • Mechanical ISO 2110
  • Electrical v.28
  • Functional v.24
  • Procedural v.24

82
Mechanical Specification
83
Electrical Specification
  • Digital signals
  • Values interpreted as data or control, depending
    on circuit
  • Less than -3v is binary 1, more than 3v is
    binary 0 (NRZ-L)
  • Signal rate lt 20kbps
  • Distance lt15m
  • For control, Less than-3v is off, 3v is on

84
3-wire and 5-wire RS-232
  • A minimal "3-wire" RS-232 connection consisting
    only of transmit data, receive data, and ground,
    is commonly used when the full facilities of
    RS-232 are not required. Even a two-wire
    connection (data and ground) can be used if the
    data flow is one way (for example, a digital
    postal scale that periodically sends a weight
    reading, or a GPS receiver that periodically
    sends position, if no configuration via RS-232 is
    necessary).
  • When only hardware flow control is required in
    addition to two-way data, the RTS and CTS lines
    are added in a 5-wire version.

85
Null Modem DTE to DTE
  • RS-232-C Null Modem Cable (for Terminal/PC with
    25-pin Connector)
  • RS-232-C Null Modem Cable (for Terminal/PC with
    9-pin Connector)

86
Null Modem
87
Summary Null Modem
Simple Null Modem without Handshaking
Null Modem With Loop-Back Handshaking
Null Modem With Partial Handshaking
Null Modem With Full Handshaking
88
Synchronous - Bit Level
  • Block of data transmitted without start or stop
    bits
  • Clocks must be synchronized
  • Can use separate clock line
  • Good over short distances
  • Subject to impairments
  • Embed clock signal in data
  • Manchester encoding
  • Carrier frequency (analog)

89
Synchronous - Block Level
  • Need to indicate start and end of block
  • Use preamble and postamble
  • e.g. series of SYN (hex 16) characters
  • e.g. block of 11111111 patterns ending in
    11111110
  • More efficient (lower overhead) than async

90
Synchronous (diagram)
91
Flow Control/Error Control
  • ??????????????????????????????????????
    ???????????????????????????????
  • ?????????????????? ???????????????????????????????
    ????????????????
  • ???? Mechanism ??????????????? Error Control
    ?????????? Error ???????????? Retransmission
  • ?????????????? ARQ Automatic Repeat Request

92
Model of Frame Transmission
93
Stop and Wait Flow Control
d
T
Efficiency d/T x 100
94
Sliding Window Diagram
95
Example Sliding Window
96
Stop and Wait - Diagram
  • ????? Frame ?????? ????? Timer
  • Frame Sequence ??? 1 Bit ?????????? Frame ???

???????????? ??? Acknowledge ?????
Piggyback ???????? Microprocessor ??????????? Ack
??????????
97
Go Back N - Diagram
  • ????? Frame ?????? ????? Timer
  • ???? Window ????????????? 2n-1
  • ??????? Error ?????????????????????? Frame ????

???????????? ??? Acknowledge ????? Piggyback
98
Selective Reject - Diagram
  • ????? Frame ?????? ????? Timer
  • ???? Window ????????????? 2n-1
  • ??????? Error ???????????? Error Frame

???????????? ??? Acknowledge ????? Piggyback
99
WAN
  • WAN
  • Public Network
  • ?????????????????????? Network ???????????????
    ???? Service Provider ????????????????????
  • ????????????????? ??????????????????
    ????/???????????
  • ??????????????
  • Technologies ???????????????????? ??????????
  • Network
  • Circuit Switching Network
  • Packet Switching Network

100
Circuit Switching Network
  • ???????????????????????
  • ????????????????????????? Real-Time
  • ???????? Error ???????
  • ??? Delay ??? Delay Variation ????????????????????
    ???????????
  • ??????????????? NW ??????????????????????????
    ????????????????????????????????????????
    (Circuit) ?????????????? ??????????????????
    Dedicate Circuit
  • ???????????? ???????????? Resource
    ??????????????????????????? ??????????????????????
    ????????????? ?????????????????????

101
Circuit Switching Network
  • ???????????? ???????????? Resource
    ??????????????????????????? ??????????????????????
    ????????????? ?????????????????????
  • ?????????????????????????? 3 Phase
  • 1. Connection ??????? Circuit ????????????????????
    ????????? ??? Network ?????????? ??????????? Link
    ??? ??????? Node Switch ???????? ?????????????
    ???????????????????? ???????????????????
  • 2. Data Transfer ??????????????????????
  • 3. Disconnection ??????????????? ???? Resource
    ???????????????????????????? ??? Network
    ??????????????????????????

102
Simple Switched Network
103
Simple Switched Network
104
Simple Switched Network
105
Simple Switched Network
106
Simple Switched Network
107
Simple Switched Network
BLOCKING
108
Simple Switched Network
B ?? D Finish
BLOCKING
109
Simple Switched Network
B ?? D Finish
BLOCKING
110
Simple Switched Network
B ?? D Finish
111
Public Circuit Switched Network
???????????????????? Switching ?? Circuit
Switching Network
112
Circuit Switch
  • ???????????? Data
  • ??????????? MODEM Modulator/Demodulator
  • ?????????????????????????????? Burst ????????????
    ??????????????????????????????
  • ????? WEB Page ??? Load Web ??????????????? ???
    Page ?????????? ??????????????????????????????????
    ???
  • ??????? Web Page ???????????? Network Bandwidth
    ?????????????????????????????? Load
  • Circuit ????????? ????????????????????
    ???????????? ??????????????????
  • ????????????????

113
Circuit Switch
  • ???????????????????????????? Site
    ????????????????????????? Real-Time ??? Off Line
  • ??????????????????????????? ??????????????????????
    ??????????????? ????? 1 ?????
  • ?????????? ??? Modem ???????????????
  • ?????????
  • ?????????????
  • ??????? ????????????????????? ???????????
  • ???????? Internet ?????????? ?????? Online ???
    ???????????????????????????

114
Example
Modem
Modem
Huahin
Chiang Mai
?????????????????
Modem
Modem
Bangkok
Koraj
115
Packet Switching Network
  • Circuit Switching ????????????????????????????
  • ?????? Packet Switching
  • ?????????????????? Packet ????????
  • ??????? Circuit ??????????????????????
    ???????????????????????
  • Online ?????????????????????? ?????? Block
  • ?????????????????? ?????? Share ???????? Circuit
    ????? ???????????????? ????????????
  • ??????????????????????????? ??????????????????????
    ????????? ???????????? Delay
  • ?????????? ???????????? Circuit ?????
  • ?????????????????????????????? Circuit ???????
    Transparency
  • ??????????????????????? ?????????? Circuit
    ???????? ????????????????
  • Address ??????????????? ?????????? Header
    ?????????
  • ???? ??? Virtual Circuit Number ?????????????
    ??????????????????????

116
Packet Switching Network
  • ????????????? Share ??????? ??????????????????????
    ???????????????????????? ?????????????????????????
    ????????? ?????????????????? MTU, Maximum
    Transfer Unit
  • ????????????????????? ???????? ?????????????????
    Packet ????? ????? Packet ????????? ???????????
    Address/VC ???? ???????? Sequence Number
    ????????????????????
  • ???????? Protocol ?????? (Application) ?????????
  • ?????? Packet Switching Network

117
Packet Switched Network
118
Packet Switched Network
119
Packet Switched Network
120
Packet Switched Network
121
Advantages
  • Line efficiency
  • ????? Link ???????? Share ??????
  • Packets ?????????????? Node ????????? Queue
    ?????????????
  • Data rate conversion
  • Each station ???????????? Local Node
    ??????????????????????????
  • Packets are accepted even when network is busy
    ???????????? Queue
  • Delivery may slow down Delay
  • Priorities can be used

122
Packet Switching Network
  • 2 Concepts ??????????????? Network (Switching
    Technique)
  • Datagram
  • Virtual Circuit
  • 2 Concepts ???????????????????????????????? (User
    Interface, Network Service)
  • Connection Oriented
  • Connectionless

123
Switching Technique
  • Station breaks long message into packets
  • Packets sent one at a time to the network
  • Network ???????? Packet ?????? (???????????
    Network L3)
  • Datagram
  • Network ???????????????????????????
    ??????????????????? Address ??????????????????????
    ???? ???????????????????????? ????????????????
    Packet ???????????? Node
  • ????? Packet ??????????????????????????
    (Flexibility)
  • Virtual circuit
  • Network ???????? Connection ????????????????
    ???????? Address ??????? ??????????????
    Connection ???? Virtual Circuit Number,
    ???????????????????????? Address ????????
    ?????????????????? Virtual Circuit Number ????
  • ??? Packet ??????????????????? ????????? Flexible
    ???? Datagram ????????????????????????????
    ???????????????????????????? ??????? Connection

124
Different Services of Network (Mostly Layer 4)
?????????????????
  • Connection Oriented
  • Must perform connection to the network before
    sending data
  • the result is a connection number to reference,
    reliable communication from end-to-end
  • Connection Oriented on Virtual Circuit is used in
    packet switching network
  • Connection Oriented on datagram is used in IP
    network (TCP/IP)
  • Connectionless
  • Do not guarantee delivery but fast and efficient
    for small data transmission
  • Connectionless on VC ??????????????
  • Connectionless on datagram is used in IP network
    (UDP/IP)

125
???? Packet Switching Network
  • 2 Concepts ??????????????? Network(L3)
  • Datagram
  • Virtual Circuit
  • 2 Concepts ????????????????????????????????
    (???????????? L4)
  • Connection Oriented
  • Connectionless

126
??????????? Datagram
  • Each packet treated independently
  • Packets can take any practical route
  • Packets may arrive out of order
  • Packets may go missing
  • Up to receiver(???????) to re-order packets and
    recover from missing packets
  • ???????? ??????????? Network ??????????????
    Guarantee ????????????

127
Datagram Diagram
128
Virtual Circuit
  • Preplanned route established before any packets
    sent ?????????????????????????? Connection
  • Call request and call accept packets establish
    connection (handshake) ????? Connection
    ?????????? ??? VC Number
  • Each packet contains a virtual circuit identifier
    instead of destination address
  • No routing decisions required for each packet
    ????? VC ?????????
  • Clear request to drop circuit ???????
  • Not a dedicated path ?????????????????????
    Circuit Switching

129
Virtual Circuit Diagram
130
Virtual Circuits vs Datagram
  • Virtual circuits
  • Network can provide sequencing and error control
  • Packets are forwarded more quickly
  • No routing decisions to make
  • Less reliable
  • Loss of a node looses all circuits through that
    node
  • Datagram
  • No call setup phase
  • Better if few packets
  • More flexible
  • Routing can be used to avoid congested parts of
    the network

131
Circuit vs Packet Switching
  • Performance
  • Propagation delay
  • Transmission time
  • Node delay

132
Event Timing ??????????? 3 NW
133
HW1 Due Next Week
??????????? Download HW 1, Week 1
??????????????????????? A4 ???????????????????
?????????????????? ????????????????????(?????????
) ???????????????? ???????????? ??????????????
???? ??? Section ?????????
134
End of Week 1
  • End of Review Part I
  • Next Week Review Part II
  • LAN and LAN Technologies
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