OSI Model

OSI Model

Open Systems Interconnection model

OSI Layer 7

Application – user-facing network services (HTTP, FTP, SMTP)

OSI Layer 6

Presentation – formatting, encryption, compression

OSI Layer 5

Session – session management and connection control

OSI Layer 4

Transport – end-to-end communication, ports, reliability (TCP/UDP)

OSI Layer 3

Network – logical addressing and routing (IP)

OSI Layer 2

Data Link – frames, MAC addresses, local delivery

OSI Layer 1

Physical – bits on the wire, signals, cables, voltages

OSI mnemonic (top to bottom)

All People Seem To Need Data Processing

TCP/IP Model

A practical 4-layer networking model used on the Internet

Number of TCP/IP layers

4

TCP/IP Application layer

High-level protocols and user services (HTTP, FTP, SMTP, DNS)

TCP/IP Transport layer

End-to-end communication (TCP, UDP)

TCP/IP Internet layer

Logical addressing and routing (IP)

TCP/IP Network Access layer

Physical transmission and framing (Ethernet, Wi-Fi)

OSI layers mapped to TCP/IP Application

OSI Layers 7 (Application), 6 (Presentation), 5 (Session)

OSI layer mapped to TCP/IP Transport

OSI Layer 4 (Transport)

OSI layer mapped to TCP/IP Internet

OSI Layer 3 (Network)

OSI layers mapped to TCP/IP Network Access

OSI Layers 2 (Data Link) and 1 (Physical)

Which model is theoretical?

OSI model

Which model is used in practice?

TCP/IP model

OSI layer where encryption occurs

Presentation layer (Layer 6)

OSI layer where routing occurs

Network layer (Layer 3)

OSI layer where ports exist

Transport layer (Layer 4)