Data communication to be understood properly needs a common frame of reference. If you want to know how the architectural data model is developed, its by the International Standards Organization (ISO) who develop this architectural model. They develop this model explain about the structure and core functions of a data communications protocols. This model is known as  Open Systems  Interconnect Reference Model.(OSI), this  models helps in providing common reference  for analyzing or discussing about  communications.

OSI reference Model layers

There are 7 layers in OSI reference model, starting from the bottom Physical Layer, Data Link layer, Network Layer, Transport Layer, Session Layer, Presentation layer and Application layer. These are the following layers in OSI reference model, each layer does not define one protocol osi defines any number of protocol therefore each layer consists of multiple protocols each provides a unique service in aligning with the function of that layer.

Role of OSI in data communications model

Basically OSI has 7 layers clearly states the functions of data communication protocols very accurately and clearly.  Whenever the data is transferred between co-operating applications across a Intervening network each layer of OSI represents a function and identifies each by its name and provides a short snippet of information for it.

What are Addressing, Routing and Multiplexing?

To transfer the data from two different hosts, you need to shift the data across the network to the exact host and from there you need to navigate to the exact user or process. This can be achieved by Addressing, Routing and Multiplexing.

Addressing

These are IP addresses, which help to identify each and every host across the network. Helping the data to reach the correct host.

Routing

It is a process of moving the data packets from source to the end point.

Multiplexing.

Multiplexing plays an important role in delivering data to the correct source, or module within the host. These three functions are addressing between hosts, routing between networks, and multiplexing.

Protocol and port numbers deliver data to the correct software module within the host.

Each of these functions - addressing between hosts, routing between networks, and multiplexing.