1. An Introduction

2. The 7 layers at a glance
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer

3. Application Layer
The layer that lets you view the applications and do
things.
Eg: Web Browser, Email browser

4. Presentation Layer
Presents the data in the standard format.
Eg: Things likely to be seen on a website-
• Formats
• Written Text HTML
• Pictures JPEG
• Video Clip MPEG
• Sound Clip MP3
This layer presents the data in its appropriate format.

5. Session Layer
Creates a new session for each application and keeps each separate.
Stuff being done at an instance:-
• Checking emails.
• Playing an online game.
• Listening to an online radio.
• Chatting on IM.
For each of these activities a session is created, and maintained so that your
emails do not come on the gaming screen and the radio start playing in the
IM screen.

6. Transport Layer
Determines whether to send the data “RELIABLY”
or “UNRELIABLY”.
• Reliable means used when data integrity is of prime
importance. Eg: Emails
• Unreliable means used for real time applications when a small
corruption in the data can be ignored rather than redelivery of
the data packets.
Defines the port numbers for each session.

7. Network Layer
Assigns IP address of the source and destination PC.
Searches and finds the best route to take the data from the
source to the destination.

8. DataLink Layer
Checks for the MAC address of the PCs trying to
communicate.
Checks that the data being sent is error free.

9. Physical Layer
Generates electrical pulses (0 and 1) of all the
data to be sent through the cable.

10. Conclusion
 The source PC goes through these 7 layers to reach the
destination PC.
 The destination PC receives the data via the same 7
layers beginning from Physical layer.
Source PC Destination PC
Application Layer Application Layer
Presentation Layer Presentation Layer
Session Layer Session Layer
Transport Layer Transport Layer
Network Layer Network Layer
Data Link Layer Data Link Layer
Physical Layer Physical Layer