OSI & TCP/IP Models Cheat Diagram: PDU

Mnemonic for PDUsThink of it as “Some People Fear Bad Data” going bottom-up:

• Segment (Transport)
• Packet (Network)
• Frame (Data Link)
• Bits (Physical)
• Data (top three layers)

 📝 Quick Exam Hack

• Top 3 layers (App/Presentation/Session) → always Data
• Transport → Segment
• Network → Packet
• Data Link → Frame
• Physical → Bits