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The protocol that is proprietary and operates over TCP port 49 is TACACS+, which stands for Terminal Access Controller Access-Control System Plus. TACACS+ is primarily used for authentication, authorization, and accounting (AAA) services in network environments. It is distinct from other protocols in the way that it provides a more granular level of control over the authorization process compared to RADIUS, which is not proprietary and operates over different ports.

TACACS+ encrypts the entire payload of the packets it sends, providing increased security for sensitive information, unlike RADIUS, which only encrypts the password. This can make TACACS+ a preferred choice for environments that require robust security measures. Additionally, being a proprietary protocol developed by Cisco, it integrates well with Cisco hardware and software, making it a common choice in Cisco-centric networks.

Understanding the operational context of these protocols helps to highlight TACACS+ unique position as proprietary and its specification for utilizing TCP port 49, differentiating it from the other options that operate on different ports or are not proprietary.