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  1. VPN Introduction
  2. IPSEC Introduction
  3. IPSEC Security Associations
  4. Authentication Header
  5. IPSEC Encapsulating Security Payloads
  6. Key Management
  7. Terms
  8. Credits

IPSEC Encapsulating Security Payloads (ESP)

ESP Format

Organized in 32 bit words the format is as follows:

  • Security Parameters Index (SPI) - Word 0
  • Sequence Number Field - Word 1
  • A variable amount of payload data.
  • 0-255 bytes of padding
  • 8 bits of pad length
  • 8 bits of next header
  • A variable amount of authentication data.