Which of the following is NOT a protocol of the session layer?

In the context of the OSI model, the session layer is responsible for establishing, managing, and terminating sessions between applications. It facilitates communication and coordination between different systems or processes. The protocols typically associated with the session layer focus on session management rather than the transport or application aspects of communication.

Hypertext Transfer Protocol (HTTP) operates at the application layer, managing how messages are formatted and transmitted over the internet but not managing the sessions specifically. It enables web browsers to communicate with web servers, focusing more on the transfer of data rather than session establishment or control.

In contrast, Secure Shell (SSH), Remote Procedure Call (RPC), and Session Initiation Protocol (SIP) are all associated with session layer functionalities. SSH provides secure access and management of session data, RPC facilitates communication between software components in a network, and SIP is used for initiating, maintaining, and terminating real-time sessions in multimedia applications.

Thus, identifying HTTP as not belonging to the session layer is accurate, as it is primarily engaged in data transfer and not the management of sessions per se.