A protocol in IPsec that performs packet encryption and authentication.
Short for Encapsulating Security Payload. A protocol in IPsec responsible for payload encryption and integrity verification. Unlike AH, which provides authentication only, it also encrypts the actual data payload. Because its header structure doesn't survive an IP address rewrite, it can't pass through NAT unmodified, so NAT traversal (NAT-T), which encapsulates it in UDP, is used alongside it.
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