Derived from RFC 1122

TCP/IP Four-Layer Model

The four RFC 1122 layers with their protocols and how they map onto the OSI numbering, as one downloadable reference figure.

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TCP/IP four layer model: the RFC 1122 internet protocol stack

The four layers of the TCP/IP model from RFC 1122, stacked from Application at the top to Link at the bottom, each with its core function, canonical protocols and the OSI layers it spans on the right.

TCP/IP four layer model: the RFC 1122 internet protocol stack The four communication layers of the internet host model from RFC 1122, Requirements for Internet Hosts, published by the IETF in 1989. The bands stack from Application at the top through Transport and Internet to Link at the bottom, each listing the layer number, name, core function and example protocols. A quiet right hand column maps each band to the OSI layers it spans: Application to OSI layers 5 to 7, Transport to layer 4, Internet to layer 3 and Link to layers 1 and 2. 4 Application User-facing services and APIs HTTP, SMTP, DNS, TLS 3 Transport End-to-end delivery and reliability TCP, UDP, QUIC 2 Internet Routing across interconnected networks IP, ICMP, OSPF, BGP 1 Link Frame and bit transmission on the medium Ethernet, ARP, Wi-Fi PHY OSI EQUIVALENT Spans OSI layers 5 to 7 Application, Presentation, Session Spans OSI layer 4 Transport Spans OSI layer 3 Network Spans OSI layers 1 to 2 Data Link, Physical Source: RFC 1122, Requirements for Internet Hosts, IETF (1989)

RFC 1122 describes the internet host stack in four layers rather than seven. The quiet column on the right maps each band to the OSI layer numbers it spans, so the two reference models can be read side by side without a separate lookup table.

When the practical Internet stack matters more than the full OSI taxonomy.

What you need and what you get

You'll get

  • The reference model figure, downloadable as PNG or PowerPoint

Derived from RFC 1122, Requirements for Internet Hosts. IETF (1989). All rights reserved by the publisher.