What are the different types of network security?

This is kind of broad question......
But generally it can be said as securing computer or any technical equipments (like pritners, smartphones & etc....) which is connected to the organizational networks.
There are different ways in which we can do this

1. Physical Security (by means of deploying security guards and by means of creating some kind of defence like rising up walls or strong fence some kind of things). Additionally we can also do this by using technical equipments like Video Cameras (to monitor. We can also use passwords to protect the system.

2. Perimeter Security - Mostly done by deploying Firewalls (major companies like Cisco does this),different kinds of Scanners (for people to get inside the building...etc.).

3. Securing networks by using Monitoring system - This can be done by using Monitoring tools (there are lots available for example - free tool given by Microsoft  (Network Monitor 3.4) & other tools like wireshark, snort...etc.

4. Also this can be achieved by educating and training end users.... Hope you got your answer.