1. Computer Networks
Introduction to computer networks

2. Objectives
• Define computer networks
• Classify computer networks
• Protocols & Standardization

3. Computer Networks ?
• A large number of separate but
interconnected computers do the specific job.
• A collection of autonomous computers
interconnected by a single technology.

4. Interconnected ?
Two computers are said to be
interconnected if they are able
to exchange information.

5. Types of Networks
Classification based on transmission
technology
Broadcast
links.
Point-to-
point links.

6. Broadcast networks
• Have a single communication channel that is
shared by all the machines on the network.
Host
H1
H2 H3 H4
H5H6
Communication channel

7. Broadcast networks
• Short messages (also called packets) sent by
any machine are received by all the others.
• An address field within the packet specifies for
whom it is intended.
• Upon receiving a packet, a machine checks the
address field.
• If the packet is intended for the receiving
machine, it processes the packet; otherwise it is
just ignored.
• This mode of operation is called broadcasting

8. Bus Topology Ring Topology

9. point-to-point networks
• Many connections between individual pairs of
machines.
• To go from the source to the destination, a
packet on this type of network may have to
first visit one or more intermediate machines.

10. Note:
• As a general rule, smaller, geographically
localized networks tend to use
broadcasting, whereas larger networks usually
are point-to-point

11. Types of Networks
Classification
based on
Scale
(physical size)
•LAN
• MAN
•WAN

12. Local Area Networks
• Within a single building or campus of up to a
few kilometers in size.
• They are widely used to connect personal
computers and workstations in company
offices and factories to share resources
(e.g., printers) and exchange information.

13. Three characteristics of LANs
size,
transmission
technology,
topology.
few kilometers
in size
single cable ,
speeds of 10 Mbps
to 100 Mbps
Bus, Ring

14. Metropolitan Area Networks
• A MAN covers a city.
• Ex:- cable television network

15. Wide Area Networks
• WAN, spans a large geographical area, often a
country or continent.
• The hosts are connected by a communication
subnet, or just subnet for short.
• The hosts are owned by the
customers, whereas the communication
subnet is typically owned and operated by a
telephone company or Internet service
provider.

17. Subnet
• The job of the subnet is to carry messages from
host to host, just as the telephone system
carries words from speaker to listener.
• The subnet consists of two distinct
components:
–transmission lines and
–switching elements.

18. Transmission lines move bits between
machines. They can be made of copper
wire, optical fiber, or even radio links.
Switching elements are specialized
computers used to connect two or more
transmission lines.

19. Principle of Subnet
• When a packet is sent from one router to
another via one or more intermediate
routers, the packet is received at each
intermediate router in its entirety, stored
there until the required output line is
free, and then forwarded.
• A subnet using this principle is called a store-
and-forward or packet-switched subnet.

20. • Routing algorithms are used to choose the
path between source and destination.

21. Wireless Networks
• wireless networks can be divided into three
main categories:
1. System
interconnecti
on
2. Wireless
LANs
3. Wireless
WANs.

22. System interconnection
• Connecting the components of a computer
together using short-range radio.
• Bluetooth to connect the components
without wires.
• Bluetooth also allows digital
cameras, camcorders, scanners, and other
devices to connect to a computer by merely
bringing them within range.

23. System interconnection using
Bluetooth Configuration

24. Wireless LANs
• These are
systems in which
every computer
has a radio
modem and
antenna with
which it can
communicate
with other
systems.

25. Wireless WAN
• Example:- cellular networks
• cellular wireless networks are like wireless
LANs, except that the distances involved are
much greater and the bit rates much lower.

26. Protocols & Standardization
• Human
analogy

28. What is a protocol?
• The formal specifications and conventions
that govern and control the communications
and data exchange.
• Protocols are the standards for
communications, networking, and
internetworking.

29. Standards
• Traditional standards
–Ex: TCP/IP
• Judicial Standard
o ISO/OSI