The document discusses the seven layers of the OSI model: Physical, Data Link, Network, Transport, Session, Presentation, and Application layers. It provides a brief overview of the key functions and responsibilities of each layer, such as the Physical layer being responsible for the actual physical connection and converting signals to bits, the Data Link layer handling error control and flow control between nodes, and the Transport layer providing process to process delivery and error checking of data transmission.

1. OSI Model
Khaled Md. Saifullah April,2021
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Computer
Networking
101

2. Contents //02
What is OSI Model
Layers of OSI Model
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
03
05
06
07
11
04
09
08
10
Computer
Networking
101

3. Computer
Networking
101
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What is OSI Model?
OSI Stands for Open System Interconnection. It is basically 7 layers model that help
us to communicate over the internet. It is the first standard of computer networking
system.

4. Computer
Networking
101
Layers of OSI Model //04
PLEASE
PLEASE DO
DO NOT
NOT TELL
TELL SECRECT
SECRECT PASSWORD
PASSWORD ANYONE
ANYONE
Physical
Layer
Data Link
Layer
Network
Layer
Transport
Layer
Session
Layer
Presentation
Layer
Application
Layer
1 2 3 4 5 6 7

5. Application Layer
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Networking
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Application or software which are directly connected with internet or internal
network by using this layer. These application produce the data, which has to be
transferred over the network. Here in this layer we give the command or input it will
prepare the output for us.
Networking service for user
Work by Port No.
User support totally
Works to Do
Service Port No.
--------------------------------
http 80
FTP 21
SMTP 25
Telnet 23
Example: http, FTP,
DNS,SNMP,Telnet

6. Presentation Layer
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Networking
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Presentation layer also called as translation layer. The data from the application
layer is extracted here and manipulated as per the required format to transmit over
the network.
Transmission
Encryption/Decryption
Compression
Works to Do Example: SSL, TLS
Transmission: ASCII to EBCDIC
Encrypted data--> cipher and
Decrypted data---> plain text
Compression: Reduce file size to
100MB to 80MB
1.
2.
3.

7. Session Layer
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Networking
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This layer is responsible for establishment of connection, maintenance of sessions,
authentication and also ensures security.
Session establishment and
terminate session
Synchronization
Dialog Controller
Works to Do Session: Session build up and terminate
the session
Synchronization: Add checkpoints that
are helping to find out error.
Dialog Controller: Start communication
with each other in half-duplex or full-
duplex.
Example: NetBIOS,PPTP

8. Transport Layer
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Networking
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This is the heart of OSI model. It provides service to the application layer and takers
service from Network layer. The data in this layer refereed as segments. This layer
also provides the acknowledgement of the successful data transmission and re
transmit if the data find any error.
Process to process delivery
(identify service)
Segmentation
Connection Controlling
Error Control
Flow Control
Works to Do Identify Service:
TCP UDP
---------------------------
http,FTP DNS,TFTP
(Slower) (Faster)
Segmentation: data will bread
down into small segment
Error Control: Doing by
the help of cheksum
algorithm.

9. Network Layer
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Networking
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Network layer works for transmission of data from one to other located in different
networks. It also takes care of packet routing i.e. selection of the shortest path to
transmit the packet.
Routing
Logical Addressing
Works to Do Routing: Providing the best
path for data transmission.
Logical Address: Provide IP
address to the devices.
Example: IP,ARP,ICMP

10. Data Link Layer
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The data link layer is responsible for the node to node delivery of the message. The
main function of this layer is to make sure data transfer is error free from one node to
another node over the physical layer.
Physical Addressing
Error Control
Access Control
Flow Control
Framing
Works to Do
Framing: Send a set of bits that are
meaningful to the receiver.
Physical Addressing: MAC Address
(ARP Protocol).
Flow Control: Data transmission
rate must be same at the sending
and receiving end.
Example: PPP,Ethernet

11. Physical Layer
Computer
Networking
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The lowest layer of OSI model is physical layer. It is responsible for the actual
physical connection between the devices. It contains the data in the form of bits.
When receiving the data this layer will get the electrical signal received and convert
it into 0's and 1's.
Represents of Bits
Data converts in frame
Data send by electrical
signal.
Works to Do
Example: USB, Bluetooth