What device is commonly useful to have on the perimeter between two networks?

A firewall is an essential component commonly used on the perimeter between two networks. Its primary function is to monitor and control incoming and outgoing network traffic based on predetermined security rules. By doing so, it acts as a barrier between a trusted internal network and untrusted external networks, such as the internet.

Firewalls can provide various types of protection, including the filtering of harmful data packets, the enforcement of security policies, and the prevention of unauthorized access. This makes them crucial for safeguarding sensitive information and ensuring that only legitimate traffic can pass between the networks.

In contrast, a user laptop serves primarily as an endpoint device rather than a protective barrier; IoT devices are often vulnerable to attacks due to their numerous entry points; and cameras, while useful for physical security, do not provide network security and protection like a firewall does. Thus, the firewall's role in controlling and safeguarding network traffic solidifies its importance at the network perimeter.