1. Introduction

1.1. Summary of Contents of Document

This memo specifies the base architecture for IPsec compliant systems. The goal of the architecture is to provide various security services for traffic at the IP layer, in both the IPv4 and IPv6 environments. This document describes the goals of such systems, their components and how they fit together with each other and into the IP environment. It also describes the security services offered by the IPsec protocols, and how these services can be employed in the IP environment. This document does not address all aspects of IPsec architecture. Subsequent documents will address additional architectural details of a more advanced nature, e.g., use of IPsec in NAT environments and more complete support for IP multicast. The following fundamental components of the IPsec security architecture are discussed in terms of their underlying, required functionality. Additional RFCs (see Section 1.3 for pointers to other documents) define the protocols in (a), (c), and (d).

        a. Security Protocols -- Authentication Header (AH) and
           Encapsulating Security Payload (ESP)
        b. Security Associations -- what they are and how they work,
           how they are managed, associated processing
        c. Key Management -- manual and automatic (The Internet Key
           Exchange (IKE))
        d. Algorithms for authentication and encryption

This document is not an overall Security Architecture for the Internet; it addresses security only at the IP layer, provided through the use of a combination of cryptographic and protocol security mechanisms.

The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in RFC 2119 [Bra97].

1.2. Audience

The target audience for this document includes implementers of this IP security technology and others interested in gaining a general background understanding of this system. In particular, prospective users of this technology (end users or system administrators) are part of the target audience. A glossary is provided as an appendix to help fill in gaps in background/vocabulary. This document assumes that the reader is familiar with the Internet Protocol, related networking technology, and general security terms and concepts.

1.3. Related Documents

As mentioned above, other documents provide detailed definitions of some of the components of IPsec and of their inter-relationship. They include RFCs on the following topics:

        a. "IP Security Document Roadmap" [TDG97] -- a document
           providing guidelines for specifications describing encryption
           and authentication algorithms used in this system.
        b. security protocols -- RFCs describing the Authentication
           Header (AH) [KA98a] and Encapsulating Security Payload (ESP)
           [KA98b] protocols.
        c. algorithms for authentication and encryption -- a separate
           RFC for each algorithm.
        d. automatic key management -- RFCs on "The Internet Key
           Exchange (IKE)" [HC98], "Internet Security Association and
           Key Management Protocol (ISAKMP)" [MSST97],"The OAKLEY Key
           Determination Protocol" [Orm97], and "The Internet IP
           Security Domain of Interpretation for ISAKMP" [Pip98].