Which type of network model describes the functions that must be completed at a particular layer, but does not specify exactly how each protocol should work?

The type of network model that describes the functions that must be completed at a particular layer but does not specify exactly how each protocol should work is known as a layered architecture model. This includes models like the OSI (Open Systems Interconnection) model and the TCP/IP model.

1. The OSI model is composed of seven layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical. Each layer has defined functions and serves a specific purpose in network communications but does not dictate how protocols should be implemented at each layer.

2. The TCP/IP model, which is more widely used, has four layers: Application, Transport, Internet, and Network Interface. Like the OSI model, it focuses on what each layer should do without prescribing the exact protocols to use.

Both models emphasize interoperability and modular design in networking, allowing different protocols to operate within the same framework without being directly tied to specific implementations.