Encapsulating Security Payload (ESP) is one of the core protocols of the IPsec framework and is widely used in Huawei campus and SD-WAN network solutions to provide secure data transmission. ESP operates directly over IP and is identified by a uniqueIP protocol number, which allows network devices to recognize and process ESP packets correctly.

According to HCIP Datacom Campus Network documentation and standard IP protocol definitions,ESP uses protocol number 50. ESP provides essential security services such as data confidentiality through encryption, data integrity verification, authentication, and anti-replay protection. It can operate in bothtransport modeandtunnel mode, making it suitable for scenarios such as site-to-site VPNs and remote access VPNs.

The other options listed are incorrect.Protocol number 47is used by GRE (Generic Routing Encapsulation), which is a tunneling protocol and does not provide encryption.Protocol number 51is assigned to AH (Authentication Header), another IPsec protocol that provides integrity and authentication but does not support encryption.Protocol number 102is not associated with ESP or commonly used IPsec-related protocols.

Correct identification of ESP traffic using protocol number 50 is critical for firewall configuration, security policy enforcement, and proper forwarding of encrypted traffic in campus and WAN environments. Therefore, the correct answer is50, which corresponds to optionB.