Overview of Data Communication
and Computer Networks
Data Communications
Asst. Prof. Mahdi Abbasi,
Abbasi, Ph.D.
[email protected]
bb i@B
i
Computer Engineering Department
Bu--Ali Sina University
Bu
1
Outline

Data Communication Overview




Definition
Components
Protocols and standards
Network Overview



Connectivity
Categories
Internetworks
2
Motivations

Efficient way to share resources



Cost – less expensive
Accessibility – easier
Efficient way to exchange information



Time – faster
Size – bigger
Correctness – more accurate
3
Data Communication: Definition

Data Communication:
Transfer
T
f off data
d
ffrom one d
device
i to another
h via
i
some form of transmission medium.
4
Data Communication
Hi,
how
are
you?
Hi,, how are yyou?
Hi,
how
are
you?
Hi,, how are yyou?
Computer
01010001
User
01010001
5
Components in Communication
1 Message
Hi, how are you?
5 Protocol
P t l
2
Sender
3 Receiver
4 Medium
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Data Representation
p

Numbers




2
ASCII, Unicode
Images


150
Text


8/16/32 bit integers
floating point
255
Bit patterns
patterns, Graphics formats JPG/GIF/etc
Audio  Samples of continuous signal
Video  Sequence of bitmap images
7
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
pp
but widelyy adopted
p

De jure (in law) standards
 approved by an organization
8
Standards Organizations
g

Creation Committees



ISO, ITU
ITU--T, ANSI, IEEE, EIA
Forums
Regulatory Agencies
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Direction of Data Flow

Simplex:: One direction only
Simplex
data flow
Monitor
Server
data flow
Keyboard
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Direction of Data Flow

Half Duplex: Both directions, one at a time
data flow at time 1
data flow at time 2

E.g., walkiewalkie-talkies
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Direction of Data Flow

Full Duplex:
Duplex: Both directions simultaneously
data flow
data flow


E.g., telephone
Can be emulated on a single communication link
using various methods
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Networks

Network: a set of devices connected by
media links
Laptop
iMac
Workstation
Media Links
Server
SD
Printer
Scanner
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Types
yp of Connections


Point-to
Pointto--point
Multipoint (multidrop)
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Point--To
Point
To--Point Connection
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Multipoint
p
Connection
Wireless
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Topology
p gy

Topology: physical or logical arrangement
of devices






Point-to
Pointto--point
Mesh
Star
Bus
Ring
g
Hybrid
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Point--to
Point
to--Point Connection
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Fullyy Connected Mesh Topology
p gy
E
A
D
B
C
19
Fullyy Connected Mesh Topology
p gy
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Fullyy Connected Mesh Topology
p gy

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
p gy
A
D
Hub
B
Drop
C
Drop
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Star Topology
p gy
A
D
Switch
B
C
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Star Topology
p gy
A
D
Hub
B
C
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Star Topology
p gy

Pros:



Hub



One I/O portt per
O
device
Little cabling
Easy to install
Robustness
Easy to identify fault
Cons:


Single point of failure
More cabling
g still
required
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Bus Topology
p gy
Drop
line
Tap
Terminator
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Bus Topology
p gy
A
B
C
D
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Bus Topology
p gy
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Bus Topology
p gy

Pros:



Little cabling
Easy to install
Cons:



Difficult
Diffi
lt to
t modify
dif
Difficult to isolate fault
Break in the bus cable
stops all transmission
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Ring
g Topology
p gy
C
D
B
A
30
Ring
g Topology
p gy
31
Ring
g Topology
p gy

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
y
Topologies
p g
PWR
10M100M
ACT ACT
1 2 3 4 5 6 7 8 9 101112
COLCOL
SWITCH
131415161718192021222324
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
UPLINK
PWR
1 2345 6 789101112
10M100M
ACTACT
COLCOL
SWITCH
131415161718192021222324
1
2
3
4
5
6
7
8
9
10 11 12
UPLINK
13 14 15 16
17 18 19 20
21 22 23 24
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Network Categories
g



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
35
Wide Area Networks

Network providing longlong-distance communication
over a country,
t a continent,
ti
t or th
the whole
h l world
ld
36
WAN Technologies
g

Circuit Switching


Packet Switching


Physical links are dedicated between two points
Data are put in packets which are stored and
forwarded at each node
Virtual Circuit Switching
Virtual links are established between two points
 Frame Relay and ATM (Asynchronous Transfer Mode)

37
Metropolitan
p
Area Networks

Network extended over an entire city
Bangkhen
Kampangsaen
a pa gsae
38
Switching
g


Dedicated circuits
Circuit switching


Telephone switches
establish circuits
for communication
Packet switching



aaa
o
Data
are pu
put into
packets
Each stamped with
source and destination
addresses
Routers know where to
forward packets
telephone
switch
Packet
Router
39
Network of Networks
Company B
Company A
Network Interface Card (NIC)
Company C
Company D
40
Internetworking
g



How to allow devices from different
standards to communicate
Gateways/routers – devices capable of
communicating in several standards
These become "network
"network of networks"
networks"
41
Internetworks

Two or more networks connected become
an internetwork, or internet
Network1
Network2
Gateway
N t
Network3
k3

Example:
p The Internet
42
The Internet


The largest internetwork (network of networks)
i the
in
th world
ld
Devices communicating with TCP/IP protocol
suite
ite
Stanford
U. of Utah
UC Santa Barbara
UCLA
43
Summaryy

Data communication


Computer
p
networks



Protocols and standards
Topologies
LAN/MAN/WAN
Internetworks (networks of networks)
44