Overview of Data Communication
and Computer Networks
01204325: Data Communication
and Computer Networks
Asst. Prof. Chaiporn Jaikaeo, Ph.D.
chaiporn.j@ku.ac.th
http://www.cpe.ku.ac.th/~cpj
Computer Engineering Department
Kasetsart University, Bangkok, Thailand1
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 of data from one device to another via
some form of transmission medium.
4
Data Communication
Hi,
Hi,
how
how
are
are
you?
you?
Hi, how are you?
Hi, how are you?
Computer
01010001
User
01010001
5
Components in Communication
1 Message
Hi, how are you?
5 Protocol
2
Sender
3 Receiver
4 Medium
6
Data Representation

Numbers




2
ASCII, Unicode
Images


150
Text


8/16/32 bit integers
floating point
255
Bit 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 but widely adopted

De jure (in law) standards
 approved by an organization
8
Standards Organizations

Creation Committees



ISO, ITU-T, ANSI, IEEE, EIA
Forums
Regulatory Agencies
9
Direction of Data Flow

Simplex: One direction only
data flow
Monitor
Server
data flow
Keyboard
10
Direction of Data Flow

Half Duplex: Both directions, one at a time
data flow at time 1
data flow at time 2

E.g., walkie-talkies
11
Direction of Data Flow

Full Duplex: Both directions simultaneously
data flow
data flow


E.g., telephone
Can be emulated on a single communication link
using various methods
12
Networks

Network: a set of devices connected by
media links
Laptop
iM ac
Workstation
Media Links
Server
SD
Printer
Scanner
13
Types of Connections


Point-to-point
Multipoint (multidrop)
14
Point-To-Point Connection
15
Multipoint Connection
Wireless
16
Topology

Topology: physical or logical arrangement
of devices






Point-to-point
Mesh
Star
Bus
Ring
Hybrid
17
Point-to-Point Connection
18
Fully Connected Mesh Topology
E
A
D
B
C
19
Fully Connected Mesh Topology
20
Fully Connected Mesh Topology

Pros:





Dedicated links
Robustness
Privacy
Easy to identify fault
Cons:



A lot of cabling
I/O ports
Difficult to move
21
Star Topology
A
D
Hub
B
Drop
C
Drop
22
Star Topology
A
D
Switch
B
C
23
Star Topology
A
D
Hub
B
C
24
Star Topology

Pros:



Hub



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
25
Bus Topology
Drop
line
Tap
Terminator
26
Bus Topology
A
B
C
D
27
Bus Topology
28
Bus Topology

Pros:



Little cabling
Easy to install
Cons:



Difficult to modify
Difficult to isolate fault
Break in the bus cable
stops all transmission
29
Ring Topology
C
D
B
A
30
Ring Topology
31
Ring Topology

Pros:



Easy to install
Easy to identify fault
Cons:


Delay in large ring
Break in the ring stops all
transmission
32
Hybrid Topologies
PWR
10M100M
ACT ACT
1 2 3 4 5 6 7 8 9 101112
COL COL
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
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
UPLINK
13 14 15 16
17 18 19 20
21 22 23 24
33
Network Categories



Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
34
Local Area Networks

Network in a single office, building, or
campus
35
Wide Area Networks

Network providing long-distance communication
over a country, a continent, or the whole world
36
Metropolitan Area Networks

Network extended over an entire city
Bangkhen
Kampangsaen
38
Switching


Dedicated circuits
Circuit switching


Telephone switches
establish circuits
for communication
Packet switching



Data are 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



How to allow devices from different
standards to communicate
Gateways/routers – devices capable of
communicating in several standards
These become "network of networks"
41
Internetworks

Two or more networks connected become
an internetwork, or internet
Network1
Network2
Gateway
Network3

Example: The Internet
42
The Internet


The largest internetwork (network of networks)
in the world
Devices communicating with TCP/IP protocol
suite
Stanford
U. of Utah
UC Santa Barbara
UCLA
43
Summary

Data communication


Computer networks



Protocols and standards
Topologies
LAN/MAN/WAN
Internetworks (networks of networks)
44