This document provides an introduction to network layer models and protocol data units. It discusses how layered models help visualize protocol interactions by breaking down network functions into standardized areas. The key reference models covered are the OSI 7-layer model, the TCP/IP 4-layer model, and the 5-layer model used in this course. Each layer in the models performs a specific task, such as determining the best packet path or sending bits as signals. Protocol data units are the messages passed between layers, with each layer encapsulating the PDU from the previous layer.

1. Lecture 2: Introduction
Dr. Ameer Gouda

2. Contents
1. Layering and Reference Models
2. Encapsulation and PDU

3. Why Using Layer Models
 To visualize the interaction between various protocols,
it is common to use a layered model.
 Benefits of doing so:
Helps break down network function.
Create standard for equipment manufacturing.
Allows vendors to focus in specialized areas of the network.

4. Reference Models
Reference models describe the layers in a network
architecture as follows:
 OSI reference model (7 layer model)»
 TCP/IP reference model (Protocol model 4/5)»
 Model used for this text »

5. OSI Reference Model
 A principled, international standard, seven layer
model to connect different systems
– Provides functions needed by users
– Converts different representations
– Manages task dialogs
– Provides end-to-end delivery
– Determine the best path for packet
– Sends frames of information
– Sends bits as signals

6. TCP/IP Reference Model
 A four layer model derived from experimentation;
omits some OSI layers and uses the IP as the network
layer.

7. Model used in this course
It is based on the TCP/IP (5 layer) model

8. Protocol Data Units (PDU) and Encapsulation

9. Protocol Data Units (PDU) and Encapsulation