RFC 2406 (rfc2406) - Page 2 of 22
IP Encapsulating Security Payload (ESP)
Alternative Format: Original Text Document
RFC 2406 IP Encapsulating Security Payload November 1998 3.4.5 Packet Decryption..................................16 4. Auditing.....................................................17 5. Conformance Requirements.....................................18 6. Security Considerations......................................18 7. Differences from RFC 1827....................................18 Acknowledgements................................................19 References......................................................19 Disclaimer......................................................20 Author Information..............................................21 Full Copyright Statement........................................22 1. Introduction The Encapsulating Security Payload (ESP) header is designed to provide a mix of security services in IPv4 and IPv6. ESP may be applied alone, in combination with the IP Authentication Header (AH) [KA97b], or in a nested fashion, e.g., through the use of tunnel mode (see "Security Architecture for the Internet Protocol" [KA97a], hereafter referred to as the Security Architecture document). Security services can be provided between a pair of communicating hosts, between a pair of communicating security gateways, or between a security gateway and a host. For more details on how to use ESP and AH in various network environments, see the Security Architecture document [KA97a]. The ESP header is inserted after the IP header and before the upper layer protocol header (transport mode) or before an encapsulated IP header (tunnel mode). These modes are described in more detail below. ESP is used to provide confidentiality, data origin authentication, connectionless integrity, an anti-replay service (a form of partial sequence integrity), and limited traffic flow confidentiality. The set of services provided depends on options selected at the time of Security Association establishment and on the placement of the implementation. Confidentiality may be selected independent of all other services. However, use of confidentiality without integrity/authentication (either in ESP or separately in AH) may subject traffic to certain forms of active attacks that could undermine the confidentiality service (see [Bel96]). Data origin authentication and connectionless integrity are joint services (hereafter referred to jointly as "authentication) and are offered as an option in conjunction with (optional) confidentiality. The anti- replay service may be selected only if data origin authentication is selected, and its election is solely at the discretion of the receiver. (Although the default calls for the sender to increment the Sequence Number used for anti-replay, the service is effective only if the receiver checks the Sequence Number.) Traffic flow Kent & Atkinson Standards Track
