The TCP/IP Guide - IPSec Overview, History and Standards

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Since IPSec is actually a collection of techniques and protocols, it is not defined in a single Internet standard. Instead, a collection of RFCs defines the architecture, services and specific protocols used in IPSec. Some of the most important of these are shown in Table 78, all of which were published in November 1998:

**Table 78: Important IP Security (IPSec) Standards**
RFC Number	Name	Description
2401	Security Architecture for the Internet Protocol	The main IPSec document, describing the architecture and general operation of the technology, and showing how the different components fit together.
2402	IP Authentication Header	Defines the IPSec Authentication Header (AH) protocol used for ensuring data integrity and origin verification.
2403	The Use of HMAC-MD5-96 within ESP and AH	Describes a particular encryption algorithm for use by AH and ESP called Message Digest 5 (MD5), HMAC variant. (Obviously. J)
2404	The Use of HMAC-SHA-1-96 within ESP and AH	Describes a particular encryption algorithm for use by AH and ESP called Secure Hash Algorithm 1 (SHA-1), HMAC variant. (Naturally. J)
2406	IP Encapsulating Security Payload (ESP)	Describes the IPSec Encapsulation Security Payload (ESP) protocol that provides data encryption for confidentiality.
2408	Internet Security Association and Key Management Protocol (ISAKMP)	Defines methods for exchanging keys and negotiating security associations.
2409	The Internet Key Exchange (IKE)	Describes the Internet Key Exchange (IKE) protocol used to negotiate security associations and exchange keys between devices for secure communications. Based on ISAKMP and OAKLEY.
2412	The OAKLEY Key Determination Protocol	Describes a generic protocol for key exchange.

Deployment of IPSec has only really started to take off in the last few years; a major use of the technology is in implementing virtual private networks (VPNs). It appears that the future IPSec is bright, as more and more individuals and companies decide that they need to take advantage of the power of the Internet, while also protecting the security of the data they transport over it.