What is Computer Network ?

The purpose is that devices can share data
Connect various homogeneous and heterogeneous devices
Sender sends some data / information to the receiver by the help of some connection
Technically the data sent should be understandable by the receiver, for this there must be some protocol involved
Protocol are set of instructions (sender sends data but follows some set of instructions)
Connection can be made sender-receiver or vice-versa
Protocols produce proper communication

Network Criteria

Can be measured in many ways, including transit time (amount of time required for a message to travel from one device to another) and response time (it is the elapsed time between an enquiry and a response)
Depends on number of users, type of transmission medium, capabilities of the connected hardware, and software efficiency
2. Reliability
Measured by frequency of failure, time it takes to recover from failure, and network robustness
3. Security
Includes protecting data from unauthorised access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data loss