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Networking Fundamentals · Foundational

TCP/IP Model

The four-layer model of the Internet protocol suite: Link (Network Access), Internet, Transport and Application.

Definition

The TCP/IP model, defined by the IETF in RFC 1122, describes the architecture actually used on the Internet. Its layers are Link or Network Access (OSI 1-2), Internet (OSI 3), Transport (OSI 4) and Application (OSI 5-7). Some textbooks, including Cisco materials, show a five-layer variant that splits the Link layer into Physical and Data Link.

Example

IP operates at the Internet layer, while TCP and UDP operate at the Transport layer.

Exam tip

Know the mapping to OSI layers; a common trap is the four- versus five-layer variant, so read which model the question uses.

Don't confuse it with

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