What protocol and port does ESP traffic primarily use?

ESP, which stands for Encapsulating Security Payload, is a protocol used in the context of IPsec (Internet Protocol Security) to provide confidentiality, integrity, and authentication to IP packets. It primarily operates on a specific protocol number rather than within the framework of typical transport layer protocols like TCP or UDP.

The correct answer highlights that ESP traffic primarily uses IP protocol number 50. This protocol is part of the IP layer, directly communicating with IP and is not dependent on a port number as seen in TCP and UDP communications. This means ESP traffic is not referenced or routed through ports such as those specified in alternative options, like TCP port 53 or HTTP port 443.

Understanding this distinction is crucial for firewall configurations, network security management, and troubleshooting, where knowing how IPsec operates—including the role of ESP—can significantly impact the effective implementation of secure communications.