1. Network Applications and Layered Architectures Protocols OSI Reference Model

2. 7-Layer OSI Reference Model Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Network Layer Application Data Link Layer Physical Layer Network Layer Data Link Layer Physical Layer Communicating End Systems One or More Network Nodes End-to-End Protocols

3. Headers & Trailers Each protocol uses a header that carries addresses, sequence numbers, flag bits, length indicators, etc… CRC check bits may be appended for error detection Application Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Transport Layer Network Layer Data Link Layer Physical Layer Application APP DATA AHAPP DATA TH AHAPP DATA NHTH AHAPP DATA DHNHTH AHAPP DATA CRC bits

4. Classification of interconnected processors by scale.