There is a strong need to protect our own network from intrusions. To protect from attacks from the Internet, firewall systems are installed that implement a strict boundary between the internal and external. But defending your territory in not only about placing good firewalls. You need to address the full length of your perimeter. The perimeter is the boundary between your network and the outside world.
Any external link has to be considered part of the perimeter.
This will be the basis for distinguishing between what's inside and what's outside. Internet An Internet connection is a prime candidate for a perimeter boundary. It is a link to an uncontrolled environment that can contain many threats to your infrastructure. If you neglect to put in any protection at all, you are at an extremely high risk. Anyone in the world will be able to connect to your internal network.