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Overview of Data Communication
and Computer Networks
01204325: Data Communication and Computer Networks
Asst. Prof. Chaiporn Jaikaeo, [email protected]
http://www.cpe.ku.ac.th/~cpjComputer Engineering Department
Kasetsart University, Bangkok, Thailand
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Outline Data Communication Overview
Definition Components Protocols and standards
Network Overview Connectivity Categories Internetworks
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Motivations Efficient way to share resources
Cost – less expensive Accessibility – easier
Efficient way to exchange information Time – faster Size – bigger Correctness – more accurate
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Data Communication: Definition
Data Communication:
Transfer of data from one device to another via some form of transmission medium.
Transfer of data from one device to another via some form of transmission medium.
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Data Communication
Hi, how are you?
01010001
Hi, how are you?
UserComputer
you?
how
are
Hi,
you?
how
are
Hi,
01010001
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Components in Communication
Hi, how are you?
5 Protocol
4 Medium
3 Receiver2 Sender
1 Message
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Data Representation Numbers
8/16/32 bit integers floating point
Text ASCII, Unicode
Images Bit patterns, Graphics formats
JPG/GIF/etc Audio Samples of continuous signal Video Sequence of bitmap images
150
2
255
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Protocols and Standards Protocol
A set of rules governing data communications
Syntax: format of data block Semantics: meaning of each section Timing: speed and sequencing
Standards De facto (in practice) standards
not approved but widely adopted De jure (in law) standards
approved by an organization
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Standards Organizations Creation Committees
ISO, ITU-T, ANSI, IEEE, EIA Forums Regulatory Agencies
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Direction of Data Flow Simplex: One direction only
Server Monitor
data flow
Keyboard
data flow
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Direction of Data Flow Half Duplex: Both directions, one at a
time
E.g., walkie-talkies
data flow at time 1
data flow at time 2
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Direction of Data Flow Full Duplex: Both directions
simultaneously
E.g., telephone
Can be emulated on a single communication link using various methods
data flow
data flow
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Networks Network: a set of devices connected
by media links
Media Links
Printer
Workstation
Laptop
Scanner
Server
SD
iMac
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Types of Connections Point-to-point Multipoint (multidrop)
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Point-To-Point Connection
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Multipoint Connection
Wireless
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Topology Topology: physical or logical
arrangement of devices Point-to-point Mesh Star Bus Ring Hybrid
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Point-to-Point Connection
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Fully Connected Mesh Topology
A
CB
D
E
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Fully Connected Mesh Topology
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Fully Connected Mesh Topology
Pros: Dedicated links Robustness Privacy Easy to identify
fault Cons:
A lot of cabling I/O ports Difficult to move
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Star Topology
Hub
A D
B CDrop
Drop
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Star Topology
Switch
A D
B C
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Star Topology
Hub
A D
B C
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Star Topology Pros:
One I/O port per device
Little cabling Easy to install Robustness Easy to identify
fault
Cons: Single point of
failure More cabling still
required
Hub
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Bus Topology
Dropline
Tap
Terminator
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Bus Topology
A B C D
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Bus Topology Pros:
Little cabling Easy to install
Cons: Difficult to modify Difficult to isolate fault Break in the bus cable stops all
transmission
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Ring Topology
A
B
C
D
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Ring Topology
Pros: Easy to install Easy to identify fault
Cons: Delay in large ring Break in the ring stops
all transmission
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Hybrid Topologies
ACTACT10M100M
1 2 3 4
13 14 15 16
5 6 7 8
17 18 19 20
9 10 11 12
21 22 23 24
UPLINK
1 2 3 4 5 6 7 8 9 101112
131415161718192021222324COLCOL
PWR
SWITCH
ACTACT10M100M
1 2 3 4
13 14 15 16
5 6 7 8
17 18 19 20
9 10 11 12
21 22 23 24
UPLINK
1 2 3 4 5 6 7 8 9 101112
131415161718192021222324COLCOL
PWR
SWITCH
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Network Categories Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN)
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Local Area Networks Network in a single office, building,
or campus
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Wide Area Networks Network providing long-distance
communication over a country, a continent, or the whole world
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Metropolitan Area Networks Network extended over an entire city
Bangkhen Kampangsaen
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Switching Dedicated circuits Circuit switching
Telephone switchesestablish circuitsfor communication
Packet switching Data are put into
packets Each stamped with
source and destinationaddresses
Routers know where toforward packets
telephone
switch
Router
Packet
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Network of Networks
Company A
Company D
Network Interface Card (NIC)
Company B
Company C
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Internetworking How to allow devices from different
standards to communicate Gateways/routers – devices
capable of communicating in several standards
These become "network of networks"
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Internetworks Two or more networks connected
become an internetwork, or internet
Example: The Internet
Network1 Network2
Gateway
Network3
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The Internet The largest internetwork (network of
networks) in the world Devices communicating with TCP/IP
protocol suite
UCLA
Stanford
UC Santa Barbara
U. of Utah
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Summary Data communication
Protocols and standards Computer networks
Topologies LAN/MAN/WAN
Internetworks (networks of networks)