Tim:
Since you're making this public
Jatin K:
entire network is not connected to the Internet .... it's only on LAN only 60 to 65 computers on it
That could be public or private... Whether you want to be more secure against eavesdropping on traffic, and against malcontented people, is more of an issue about who can access it, and what they might do, regardless of whether they're on the internet or the same LAN.