Working of ISO-OSI Model
The ISO-OSI (International organization of Standardization – Open System Interconnection) says to group together the functions which are related to each other.
The Functions in OSI Model that are needed for proper communication can be divided into 2 types :-
1. Mandatory Functions:
Here the implementation of the functions is not optional, i.e., it means these functions must be implemented for proper communication.
(i) Error Control (ii) Flow Control (iii) Access Control (iv) Multiplexing and De-Multiplexing (v) Addressing, etc.
2. Optional Functions:
Here the implementation of the functions is optional, i.e., it means the implementation of these functions is not must.
(i) Encryption/ Decryption (ii) Check Pointing. (iii) Routing, etc.
Routing is optional we can sustain in Computer networks even by using Flooding.