What reference model describes computer communication services and protocols in a layered approach?

IETF is an organization responsible for developing Internet standards, not a communication model.

ISO is the organization that developed the OSI model, but ISO itself is a standards body, not the communication model.

IANA is responsible for global coordination of IP addressing, DNS root zone, and other Internet protocol resources, not a communication model.

The OSI (Open System Interconnection) model is a conceptual framework created by the International Organization for Standardization (ISO) that standardizes the functions of a communication system into seven distinct layers. This layered approach describes how data is transmitted from one computer to another, with each layer performing specific functions and interacting with the layers above and below it.