Quiz Entry - updated: 2026.07.14
How does the Internet reference model map to the OSI 7-layer model, and what is encapsulation?
The Internet model collapses OSI's top three layers (Application / Presentation / Session) into one "Application" layer. Encapsulation means each layer wraps the previous layer's data as its own payload.
| OSI | Internet Model | Example protocols |
|---|---|---|
| Application + Presentation + Session | Application | HTTP, DNS, SMTP, FTP, IMAP, LDAP |
| Transport | Transport | TCP, UDP |
| Network | Internet | IP |
| Data Link + Physical | Link | ARP, Ethernet, 802.11, 4G |
Encapsulation in flight: an HTTP message is wrapped in TCP, which is wrapped in IP, which is wrapped in 802.11 (or Ethernet) — giving you nested headers like [802.11 [ IP [ TCP [ HTTP ] ] ] ].
Tip: Threats live at every layer, and the defenses are different. ARP spoofing (Link), SYN flood (Transport), Heartbleed (TLS), SQLi (Application) — they all need their own mitigations because each layer has its own protocols and assumptions.