Digital certificates can be divided into local certificates, CA certificates, root certificates and self- signed certificates according to different usage scenarios.

Evidence appraisal needs to address the integrity verification of evidence and determine whether it meets the admissible standards. Regarding the standards for evidence appraisal, which of the following descriptions is correct?

Which of the following does not belong to Layer 2 VPN?

Convert the public IP address to a private IP address so that public network users can use the public network address to access the internal server.
Which of the following types of NATs fit the above description?

Under normal circumstances, the email protocols we often talk about include (), POP3, and SMTP.