The document explains the concept of protocol layering in data communication, highlighting the need for multiple protocols in complex communication scenarios. It describes the principles of protocol layering and provides an overview of the OSI model, detailing functions of various layers such as physical, data link, network, transport, session, presentation, and application layers. Each layer plays a crucial role in ensuring efficient and reliable communication between devices.

1. Communication
Networks
- Protocol
Layering

2. Introduction / Need for Protocol
Layering
• In data communication and networking, a
protocol defines the rules that both the
sender and receiver and all intermediate
devices need to follow for effective
communication.
• When communication is simple, we may
need only one simple protocol.
• when the communication is complex, we
may need to divide the task between
different layers.
• In this case we need a protocol at each
layer, or protocol layering.
Scenario 1: Simple Communication
Scenario 2: Complex Communication

3. Does layering actually satisfies the
needs?
Lets assume that you own a shop where you sell Jam breads, Few people gets satisfied
with what you serve. Now a Foodie walks in and asks for customization. Can you really
satisfy him with what you have?

4. Principles of Protocol Layering
The first principle dictates that if we
want bidirectional communication, we
need to make each layer so that it is
able to perform two opposite tasks,
one in each direction.
The second principle that we need to
follow in protocol layering is that the
two objects under each layer at both
sites should be identical.

5. The Entire internet operates on a Globally
Accepted Standard / Model to
communicate effectively
•
•
•
•
User Support layers
 Deals with the
interoperability among
unrelated software systems
Transport Layer
 Ensures the reliable data
transmission
Network Support
layers
 Deals with physical aspects
of moving data from one
device to another device
Physical
Layer
Data Link Layer
Network Layer
Transport Layer
Session
Layer
Presentation Layer
Application Layer

6. OSI Model – Open System Interconnect
Alligator
Pet
Steve’s
Touch
Not
Do
Please

7. 1. Physical
Layer
Transmission Rate Bit
Synchronization
Physical Topology

8. 2.Data Link
Layer
 Framing
 Physical Addressing
 Flow Control
 Error Control
 Access Control

9. 3. Network
Layer
Logical Addressing Routing

10. 4. Transport
Layer
• Functions:
• Service port addressing
• Segmentation and reassembly
• Connection control
• Connection oriented services
• Connection less services
• Flow control and error control

11. Segmentation and reassembly

12. Service Port addressing

13. 5. Session
layer
• Functions
• Dialogue control
• This function decides which application send / receive data and
connection type (Simplex or Duplex)
• Synchronization
• Maintains the same data rates at both sender and receiver
nodes.

14. 6. Presentation layer
• Functions:
• Translation
• Encryption and
decryption
• Compression

15. Presentation layer

16. 7. Application
Layer
Email Services
Browsers
Online
Shopping
Services

17. References:
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