How does router protocol work?

Could you elaborate on the functioning of the router protocol? I'm particularly interested in understanding how it enables the seamless transmission of data packets across various networks. How does it determine the most efficient path for data to travel, and how does it handle any potential roadblocks or delays that may arise during the process? Additionally, I'm curious about the security measures in place to ensure that data remains secure and private as it travels through the router protocol. Could you provide some insights into these aspects?