TLS (Transport Layer Security) is a widely accepted protocol designed to facilitate privacy and data security for communications over the Internet. It uses asymmetric cryptography for authentication of the key exchange, symmetric encryption for confidentiality, and message authentication codes for message integrity, making it the most appropriate choice for securing data transmissions with robust authentication mechanisms.

• SSH is designed for secure network services but is more commonly associated with the secure execution of command line interface commands on a remote server, rather than general data transmission security.
• L2TP combined with IPsec could secure data in transit, but the question specifies a preference for protocols that include extensive certificate-based authentication as part of the protocol itself, which aligns directly with TLS's capabilities.
• SRTP is specifically tailored for securing real-time protocols, such as VoIP, and while it does provide encryption, it is not as comprehensive in authentication and session security when compared to TLS.