1. Introduction to Computer Networks
Computer Networks
Computer network
connects two or more
autonomous computers.
The computers can be
geographically located
anywhere.

2. Introduction to Computer Networks
LAN, MAN & WAN
Network in small geographical Area (Room, Building
or a Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area
Network)
Network spread geographically (Country or across
Globe) is called WAN (Wide Area Network)

3. Introduction to Computer Networks
Applications of Networks
Resource Sharing
Hardware (computing resources, disks, printers)
i Software (application software)
Information Sharing
i Easy accessibility from anywhere (files, databases)
t Search Capability (WWW)
Communication
I Email
y Message broadcast
Remote computing
Distributed processing (GRID Computing)

4. LAN

5. Local Area Networks (LANs)
Local Area Networks are privately-owned networks within a small area,
usually a single building or campus of up to a few kilometers.
Since it is restricted in size, that means their data transmission time can
be known in advance, and the network management would be easier.
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6. Motivations for
Local Area Networking
The growing demand for local area networks is due to technical,
economic and organizational factors:
 Cost reductions through sharing of information and databases,
resources and network services.
 Increased information exchange between different departments in an
organization, or between individuals.
 The trend to automate communication and manufacturing process.
 Improve the community security.
 Increasing number and variety of intelligent data terminals, PCs and
workstations.
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7. Local Area Networks (LANS) …

8. LANS: Hardware Devices …
• Network Interface Cards
(NICs)
• Repeaters
• Bridges
• Routers
• Switches

9. Introduction to Computer Networks
Network Topology
The network topology
defines the way in
which computers,
printers, and other
devices are connected.
A network topology
describes the layout of
the wire and devices as
well as the paths used
by data transmissions.

10. MAN

11. Metropolitan area network
• A Metropolitan Area Network (MAN) is a network that
is utilized across multiple buildings
• Commonly used in school campuses or large
companies with multiple buildings
• Is larger than a LAN, but smaller than a WAN
• Is also used to mean the interconnection of several
LANs by bridging them together. This sort of network
is also referred to as a campus network
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12. Metropolitan Area Networks
(MANs)
• A Metropolitan Area Network is a system of
LANs connected throughout a city or
metropolitan area. MANs have the requirement
of using telecommunication media such as voice
channels or data channels.
• Branch offices are connected to head offices
through MANs. Examples of organizations that
use MANs are universities and colleges, grocery
chains, and banks.

13. Metropolitan Area Networks
(MANs)…

14. WAN

15. Wide Area Networks
(WANS)
WANs connect LANs together between cities

16. Wide Area Networks
(WANS) …
The main difference between a MAN
and a WAN is that the WAN uses Long
Distance Carriers. Otherwise the same
protocols and equipment are used as a
MAN.

17. Wide area network
• A Wide Area Network is a network spanning a large
geographical area of around several hundred miles to across
the globe
• May be privately owned or leased
• Also called “enterprise networks” if they are privately owned by
a large company
• It can be leased through one or several carriers (ISPs-Internet
Service Providers) such as AT&T, Sprint, Cable and Wireless
• Can be connected through cable, fiber or satellite
• Is typically slower and less reliable than a LAN
• Services include internet, frame relay, ATM (Asynchronous
Transfer Mode)
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18. Network Interconnection Components
• Networks can be connected to each other
through several components
– Repeater
– Bridge
– Router
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19. Repeater
• Regenerates and propagates all electrical transmissions
between 2 or more LAN segments
• Allows extension of a network beyond physical length limitations
• Layer 1 of the “OSI model”
Network A Network B
Higher Higher
Layers Layers
Repeater
Physical Physical Physical
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20. Bridge
• Connects 2 or more LAN segments and uses data link layer
addresses (e.g.MAC addresses) to make data forwarding
decisions
• Copies frames from one network to the other
• Layer 2 of the “OSI model”
Node in Network A Node in Network B
Higher Higher
Layers Bridge Layers
Data Link Data Link
23-01-88-A8-77-45 Data Link Data Link 53-F1-A4-AB-67-4F
Physical Physical 1 Physical 2 Physical
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21. Router
• Connects 2 or more networks and uses network layer
addresses (like IP address) to make data forwarding decisions
• Layer 3 of the “OSI model”
A node in Network A A node in Network B
Higher Higher
Layers Router Layers
Network Network
137.22.144.6 145.65.23.102
Network Network
Data Link Data Link Data Link
Data Link
Physical Physical 1 Physical 2 Physical
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