B.3.4 Per Socket Maintenance of PMTU Data........................57
     B.3.5 Delivery of PMTU Data to the Transport Layer...............57
     B.3.6 Aging of PMTU Data.........................................57
Appendix C -- Sequence Space Window Code Example......................58
Appendix D -- Categorization of ICMP messages.........................60
References............................................................63
Disclaimer............................................................64
Author Information....................................................65
Full Copyright Statement..............................................66





 
RFC 2401              Security Architecture for IP         November 1998


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








 
RFC 2401              Security Architecture for IP         November 1998


   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].

2. Design Objectives