What does a circuit gateway primarily utilize according to its operational procedure?

A circuit gateway primarily utilizes proxy connections for data transmission, which serves to facilitate communication between different networks or devices. This is particularly relevant as circuit gateways operate at the transport layer of the OSI model, providing a connection-oriented service. By acting as intermediaries, they establish and maintain sessions between clients and servers, ensuring that all data transfers can happen smoothly and securely.

The use of proxy connections is vital as it helps to manage and direct network traffic, allowing for control over the data flow and potentially offering benefits like load balancing and security measures. Circuit gateways also enhance privacy by masking the original source of network packets, making it harder for external entities to trace connections back to their origin.

In contrast, other options are not the primary focus of a circuit gateway. Direct IP address filtering pertains more to security appliances such as firewalls that specifically manage which IP addresses are allowed or denied at the network perimeter. Multiple-level packet scrutiny is more aligned with intrusion detection systems, as they analyze packets for malicious content or policy violations. Encryption at transport layers typically relates to protocols like TLS/SSL used to secure data during transmission but is not the main operational function of a circuit gateway. Thus, the emphasis on proxy connections highlights the core functionality of facilitating and managing data transmission effectively