OSI Communication protocols meets multiple functionalities as for example error correction, data encryption, changing bit string to physical signal. One of method of construct of such protocols is treat it as a set of separate algorithm with methods of communication with they. OSI is a paradigm of communication protocol, which help to understand a role of such algorithms in communication process.

Communication protocols based on OSI model can by divided into a seven layers. Roughly, algorithm gets a data from higher layer, then make some operation on it (as for example encryption), adds appropriate prefix, and a result gives to algorithm from lower layer.

1. physical layer

algorithms of this layer are used to change the bit string to physical signal, send it to neighboring node, and in opposite direction, receive a physical signal and change it to bit string

2. data link layer

this algorithms are used to monitor a work of the physical layer algorithms. For example They can set parameters of working of lower layer to reduce transmission errors.

3. network layer

algorithms from this layer determine a paths of data transfer in network, and also how many information can be send via given path.

4. transport layer

task of this layer is control of the reliability of a given link through flow control, segmentation/desegmentation, and error control. To transmission data in this layer it is used TCP protocol.

5. session layer

algorithm from this layer manages data from different applications.

6. presentation layer

task of this layer is to change data from application to canonical form, suitable for lower layer.

7. application layer

this algorithm determines interface specification, which is used by applications to send data via network.

In TCP/IP model some layers of OSI are merged. Link layer in TCP/IP model involves first and second layer from OSI, also application layer involves three highest layers of OSI model.