The document discusses the OSI model and TCP/IP model, which are conceptual frameworks for networking systems. The OSI model splits communication functions into 7 abstraction layers: physical, data link, network, transport, session, presentation, and application. It describes the responsibilities of each layer. The TCP/IP model has 4 layers: application, transport, internet, and network access. It describes how data is sent between connected devices and networks.

1. Class Note
OSI Model
The OSI Model (Open Systems Interconnection Model) is a conceptual
framework used to describe the functions of a networking system.
In the OSI reference model, the communications between a computing
system are split into seven different abstraction layers: Physical, Data
Link, Network, Transport, Session, Presentation, and Application.

3. Physical layers: The lowest layer of the OSI Model is concerned with
electrically or optically transmitting raw unstructured data bits across
the network from the physical layer of the sending device to the
physical layer of the receiving device.
Data Link layers: At the data link layer, directly connected nodes are
used to perform node-to-node data transfer where data is packaged
into frames. The data link layer also corrects errors that may have
occurred at the physical layer.
Network layers: The network layer is responsible for receiving frames
from the data link layer, and delivering them to their intended
destinations among based on the addresses contained inside the
frame. The network layer finds the destination by using logical
addresses, such as IP.

4. Transport layers: The transport layer manages the delivery and error
checking of data packets. It regulates the size, sequencing, and ultimately the
transfer of data between systems and hosts.
Session layers: The session layer controls the conversations between
different computers.Session layer services also include authentication and
reconnections.
Presentation layers: The presentation layer formats or translates data for the
application layer based on the syntax or semantics that the application
accepts.
Application layers: At this layer, both the end user and the application layer
interact directly with the software application.

5. Class Note
TCP/IP Model
TCP IP Model encourages you to decide how a particular PC ought to be
connected with the web and how the data ought to be sent between them.
It encourages you to make a virtual network when numerous PC networks
are conjunctive.
TCP/IP layers are:
• Application Layer
• Transport Layer
• Internet Layer
• Network Access Layer

7. Application layers: The application layer is the Open System Interconnection
layer, which is nearest to the end-user. It implies the Open System
Interconnection application layer permits clients to associates with another
software application.
Transport layers: The transport layer in the TCP IP model breaks the message
into little units to take care of all the more proficiently by the network layer.
Internet Layer: The Internet layer TCP IP model offers the procedural and
functional technique for moving variable-length data successions starting
with one hub then onto the next with different networks’ assistance.
Network layers: A network layer is a mix of the data line and described in
the article of the Open System Interconnection reference model.

8. Difference between TCP/IP and OSI Model

9. Digital Modulation
Digital Modulation provides more information capacity, high data
security, quicker system availability with great quality communication.
There are many types of digital modulation techniques and also their
combinations, depending upon the need.
ASK – Amplitude Shift Keying
FSK – Frequency Shift Keying
PSK – Phase Shift Keying

10. ASK – Amplitude Shift Keying
The amplitude of the resultant output depends upon the input data
whether it should be a zero level or a variation of positive and negative,
depending upon the carrier frequency.
FSK – Frequency Shift Keying
The frequency of the output signal will be either high or low, depending
upon the input data applied.
PSK – Phase Shift Keying
The phase of the output signal gets shifted depending upon the input. These
are mainly of two types, namely Binary Phase Shift Keying BPSK and
Quadrature Phase Shift Keying QPSK, according to the number of phase
shifts.

12. Cables
Fiber optic cable, twisted pair cable, and coaxial cable are the three
main types of network cables used in communication systems.
Fiber Optic Cable
Twisted Pair Cable
Coaxial Cable

13. Fiber Optic Cable: Fiber optic cable consists of
a bundle of glass threads, each of which is
capable of transmitting messages modulated
onto light waves.
Twisted Pair Cable: Twisted pair cable is a type
of ordinary wiring which connects home and
many business computers to the telephone
company.
Coaxial Cable: Coaxial cable is another type of
copper cable which has an inner conductor
surrounded by foam insulation, symmetrically
wrapped by a woven braided metal shield, then
covered by in a plastic jacket.

14. Transmission Impairment
In communication system, analog signals travel through transmission
media, which tends to deteriorate the quality of analog signal, which
means that the signal at the beginning of the medium is not the same
as the signal at the end of the medium.
Causes of impairment:

15. Attenuation – It means loss of energy. The strength of signal decreases
with increasing distance which causes loss of energy in overcoming
resistance of medium.

16. Distortion – It means changes in the form or shape of the signal. This is
generally seen in composite signals made up with different frequencies.
Each frequency component has its own propagation speed travelling
through a medium.

17. Noise – The random or unwanted signal that mixes up with the original
signal is called noise. There are several types of noise such as induced
noise, crosstalk noise, thermal noise and impulse noise which may
corrupt the signal.

18. Data Encapsulation and DE capsulation
Encapsulation: Encapsulation refers to the process of putting headers
(and sometimes trailers) around some data.
DE capsulation: DE capsulation is the inverse of the encapsulation
process.

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