1. Three-Layer Model
Distributed data communications involves three primary components:
Networks
Computers
Applications
Three corresponding layers
Network access layer
Transport layer
Application layer

2. Data Transmission Application layer creates data block
Transport layer appends header to create PDU (protocol data unit)
Destination SAP, Sequence #, Error-Detection Code
Network layer appends another header
Destination computer, facilities (e.g. “priority”)

3. Protocols in a Simplified Architecture

4. Operation of TCP/IP

5. TCP & UDP

6. IP Headers

7. Operation of TCP/IP: Action at the Sender

8. Operation of TCP/IP: Action at the Router

9. Operation of TCP/IP: Action at the Receiver

10. OSI Open Systems Interconnection Developed by ISO
Contains seven layers

11. The OSI Environment

12. TCP/IP - OSI Comparison