There are two basic types of networking models: protocol models and reference models.
A protocol model closely matches the structure of a particular protocol suite. The hierarchical set of related protocols in a suite t represents all the functionality required to interface the human network with the data network. The 4-layer TCP/IP model is a protocol model because it describes the functions that occur at each layer of protocols within the TCP/IP suite.
A reference model provides a common reference for maintaining consistency within all types of network protocols and services. A reference model is not intended to be an implementation specification or to provide a sufficient level of detail to define precisely the services of the network architecture. The primary purpose of a reference model is to aid in clearer understanding of the functions and process involved. The 7-layer Open Systems Interconnection (OSI) model is the most widely known internetwork reference model. It is used for data network design, operation specifications, and troubleshooting.