ESP (Encapsulating Security Payload)
Encapsulating Security Payload (ESP) provides confidentiality, in addition to authentication, integrity, and anti-replay. ESP can be used alone, or in combination with AH.
ESP does not normally sign the entire packet unless it is being tunneled—ordinarily, just the IP data payload is protected, not the IP header.
For example, Alice on Computer A sends data to Bob on Computer B. The data payload is encrypted and signed for integrity. Upon receipt, after the integrity verification process is complete, the data payload in the packet is decrypted. Bob can be certain it was really Alice who sent the data, that the data is unmodified, and that no one else was able to read it.
FONTE: https://technet.microsoft.com/en-us/library/cc959510.aspx?f=255&MSPPError=-2147217396
AH (Authetication Header): é um protocolo de autenticação designado pelo cabeçalho do protocolo, e a autenticação do cabeçalho. Fornece autenticação e integridade, mas não garante confidencialidade.
ESP (Encapsulation Security Payload): é um protocolo combinado de criptografia/autenticação, designado pelo formato do pacote para esse protocolo, encapsulamento de segurança do payload. Fornece autenticação, integridade e confidencialidade.
Alternativa: C