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The Internet IP Security Domain of Interpretation for ISAKMP
RFC 2407

Document type: RFC - Proposed Standard (November 1998; Errata)
Obsoleted by RFC 4306
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
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IESG State: RFC 2407 (Proposed Standard)
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Network Working Group                                           D. Piper
Request for Comments: 2407                               Network Alchemy
Category: Standards Track                                  November 1998

      The Internet IP Security Domain of Interpretation for ISAKMP

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

IESG Note

   Section 4.4.4.2 states, "All implememtations within the IPSEC DOI
   MUST support ESP_DES...".  Recent work in the area of cryptanalysis
   suggests that DES may not be sufficiently strong for many
   applications.  Therefore, it is very likely that the IETF will
   deprecate the use of ESP_DES as a mandatory cipher suite in the near
   future.  It will remain as an optional use protocol.  Although the
   IPsec working group and the IETF in general have not settled on an
   alternative algorithm (taking into account concerns of security and
   performance), implementers may want to heed the recommendations of
   section 4.4.4.3 on the use of ESP_3DES.

1. Abstract

   The Internet Security Association and Key Management Protocol
   (ISAKMP) defines a framework for security association management and
   cryptographic key establishment for the Internet.  This framework
   consists of defined exchanges, payloads, and processing guidelines
   that occur within a given Domain of Interpretation (DOI).  This
   document defines the Internet IP Security DOI (IPSEC DOI), which
   instantiates ISAKMP for use with IP when IP uses ISAKMP to negotiate
   security associations.

   For a list of changes since the previous version of the IPSEC DOI,
   please see Section 7.

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2. Introduction

   Within ISAKMP, a Domain of Interpretation is used to group related
   protocols using ISAKMP to negotiate security associations.  Security
   protocols sharing a DOI choose security protocol and cryptographic
   transforms from a common namespace and share key exchange protocol
   identifiers.  They also share a common interpretation of DOI-specific
   payload data content, including the Security Association and
   Identification payloads.

   Overall, ISAKMP places the following requirements on a DOI
   definition:

     o  define the naming scheme for DOI-specific protocol identifiers
     o  define the interpretation for the Situation field
     o  define the set of applicable security policies
     o  define the syntax for DOI-specific SA Attributes (Phase II)
     o  define the syntax for DOI-specific payload contents
     o  define additional Key Exchange types, if needed
     o  define additional Notification Message types, if needed

   The remainder of this document details the instantiation of these
   requirements for using the IP Security (IPSEC) protocols to provide
   authentication, integrity, and/or confidentiality for IP packets sent
   between cooperating host systems and/or firewalls.

   For a description of the overall IPSEC architecture, see [ARCH],
   [AH], and [ESP].

3. Terms and Definitions

   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].

4.1 IPSEC Naming Scheme

   Within ISAKMP, all DOI's must be registered with the IANA in the
   "Assigned Numbers" RFC [STD-2].  The IANA Assigned Number for the
   Internet IP Security DOI (IPSEC DOI) is one (1).  Within the IPSEC
   DOI, all well-known identifiers MUST be registered with the IANA
   under the IPSEC DOI.  Unless otherwise noted, all tables within this
   document refer to IANA Assigned Numbers for the IPSEC DOI.  See
   Section 6 for further information relating to the IANA registry for
   the IPSEC DOI.

   All multi-octet binary values are stored in network byte order.

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4.2 IPSEC Situation Definition

   Within ISAKMP, the Situation provides information that can be used by
   the responder to make a policy determination about how to process the
   incoming Security Association request.  For the IPSEC DOI, the
   Situation field is a four (4) octet bitmask with the following
   values.

       Situation                   Value
       ---------                   -----
       SIT_IDENTITY_ONLY           0x01
       SIT_SECRECY                 0x02
       SIT_INTEGRITY               0x04

4.2.1 SIT_IDENTITY_ONLY

   The SIT_IDENTITY_ONLY type specifies that the security association
   will be identified by source identity information present in an
   associated Identification Payload.  See Section 4.6.2 for a complete
   description of the various Identification types.  All IPSEC DOI
   implementations MUST support SIT_IDENTITY_ONLY by including an
   Identification Payload in at least one of the Phase I Oakley
   exchanges ([IKE], Section 5) and MUST abort any association setup
   that does not include an Identification Payload.

   If an initiator supports neither SIT_SECRECY nor SIT_INTEGRITY, the
   situation consists only of the 4 octet situation bitmap and does not
   include the Labeled Domain Identifier field (Figure 1, Section 4.6.1)
   or any subsequent label information.  Conversely, if the initiator
   supports either SIT_SECRECY or SIT_INTEGRITY, the Labeled Domain
   Identifier MUST be included in the situation payload.

4.2.2 SIT_SECRECY

   The SIT_SECRECY type specifies that the security association is being
   negotiated in an environment that requires labeled secrecy.  If
   SIT_SECRECY is present in the Situation bitmap, the Situation field
   will be followed by variable-length data that includes a sensitivity
   level and compartment bitmask.  See Section 4.6.1 for a complete
   description of the Security Association Payload format.

   If an initiator does not support SIT_SECRECY, SIT_SECRECY MUST NOT be
   set in the Situation bitmap and no secrecy level or category bitmaps
   shall be included.

   If a responder does not support SIT_SECRECY, a SITUATION-NOT-
   SUPPORTED Notification Payload SHOULD be returned and the security
   association setup MUST be aborted.

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4.2.3 SIT_INTEGRITY

   The SIT_INTEGRITY type specifies that the security association is
   being negotiated in an environment that requires labeled integrity.
   If SIT_INTEGRITY is present in the Situation bitmap, the Situation
   field will be followed by variable-length data that includes an
   integrity level and compartment bitmask.  If SIT_SECRECY is also in
   use for the association, the integrity information immediately
   follows the variable-length secrecy level and categories.  See
   section 4.6.1 for a complete description of the Security Association
   Payload format.

   If an initiator does not support SIT_INTEGRITY, SIT_INTEGRITY MUST
   NOT be set in the Situation bitmap and no integrity level or category
   bitmaps shall be included.

   If a responder does not support SIT_INTEGRITY, a SITUATION-NOT-
   SUPPORTED Notification Payload SHOULD be returned and the security
   association setup MUST be aborted.

4.3 IPSEC Security Policy Requirements

   The IPSEC DOI does not impose specific security policy requirements
   on any implementation.  Host system policy issues are outside of the
   scope of this document.

   However, the following sections touch on some of the issues that must
   be considered when designing an IPSEC DOI host implementation.  This
   section should be considered only informational in nature.

4.3.1 Key Management Issues

   It is expected that many systems choosing to implement ISAKMP will
   strive to provide a protected domain of execution for a combined IKE
   key management daemon.  On protected-mode multiuser operating
   systems, this key management daemon will likely exist as a separate
   privileged process.

   In such an environment, a formalized API to introduce keying material
   into the TCP/IP kernel may be desirable.  The IP Security
   architecture does not place any requirements for structure or flow
   between a host TCP/IP kernel and its key management provider.

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4.3.2 Static Keying Issues

   Host systems that implement static keys, either for use directly by
   IPSEC, or for authentication purposes (see [IKE] Section 5.4), should
   take steps to protect the static keying material when it is not
   residing in a protected memory domain or actively in use by the
   TCP/IP kernel.

   For example, on a laptop, one might choose to store the static keys
   in a configuration store that is, itself, encrypted under a private
   password.

   Depending on the operating system and utility software installed, it
   may not be possible to protect the static keys once they've been
   loaded into the TCP/IP kernel, however they should not be trivially
   recoverable on initial system startup without having to satisfy some
   additional form of authentication.

4.3.3 Host Policy Issues

   It is not realistic to assume that the transition to IPSEC will occur
   overnight.  Host systems must be prepared to implement flexible
   policy lists that describe which systems they desire to speak
   securely with and which systems they require speak securely to them.
   Some notion of proxy firewall addresses may also be required.

   A minimal approach is probably a static list of IP addresses, network
   masks, and a security required flag or flags.

   A more flexible implementation might consist of a list of wildcard
   DNS names (e.g. '*.foo.bar'), an in/out bitmask, and an optional
   firewall address.  The wildcard DNS name would be used to match
   incoming or outgoing IP addresses, the in/out bitmask would be used
   to determine whether or not security was to be applied and in which
   direction, and the optional firewall address would be used to
   indicate whether or not tunnel mode would be needed to talk to the
   target system though an intermediate firewall.

4.3.4 Certificate Management

   Host systems implementing a certificate-based authentication scheme
   will need a mechanism for obtaining and managing a database of
   certificates.

   Secure DNS is to be one certificate distribution mechanism, however
   the pervasive availability of secure DNS zones, in the short term, is
   doubtful for many reasons.  What's far more likely is that hosts will

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   need an ability to import certificates that they acquire through
   secure, out-of-band mechanisms, as well as an ability to export their
   own certificates for use by other systems.

   However, manual certificate management should not be done so as to
   preclude the ability to introduce dynamic certificate discovery
   mechanisms and/or protocols as they become available.

4.4 IPSEC Assigned Numbers

   The following sections list the Assigned Numbers for the IPSEC DOI:
   Situation Identifiers, Protocol Identifiers, Transform Identifiers,
   AH, ESP, and IPCOMP Transform Identifiers, Security Association
   Attribute Type Values, Labeled Domain Identifiers, ID Payload Type
   Values, and Notify Message Type Values.

4.4.1 IPSEC Security Protocol Identifier

   The ISAKMP proposal syntax was specifically designed to allow for the
   simultaneous negotiation of multiple Phase II security protocol
   suites within a single negotiation.  As a result, the protocol suites
   listed below form the set of protocols that can be negotiated at the
   same time.  It is a host policy decision as to what protocol suites
   might be negotiated together.

   The following table lists the values for the Security Protocol
   Identifiers referenced in an ISAKMP Proposal Payload for the IPSEC
   DOI.

       Protocol ID                         Value
       -----------                         -----
       RESERVED                            0
       PROTO_ISAKMP                        1
       PROTO_IPSEC_AH                      2
       PROTO_IPSEC_ESP                     3
       PROTO_IPCOMP                        4

4.4.1.1 PROTO_ISAKMP

   The PROTO_ISAKMP type specifies message protection required during
   Phase I of the ISAKMP protocol.  The specific protection mechanism
   used for the IPSEC DOI is described in [IKE].  All implementations
   within the IPSEC DOI MUST support PROTO_ISAKMP.

   NB: ISAKMP reserves the value one (1) across all DOI definitions.

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4.4.1.2 PROTO_IPSEC_AH

   The PROTO_IPSEC_AH type specifies IP packet authentication.  The
   default AH transform provides data origin authentication, integrity
   protection, and replay detection.  For export control considerations,
   confidentiality MUST NOT be provided by any PROTO_IPSEC_AH transform.

4.4.1.3 PROTO_IPSEC_ESP

   The PROTO_IPSEC_ESP type specifies IP packet confidentiality.
   Authentication, if required, must be provided as part of the ESP
   transform.  The default ESP transform includes data origin
   authentication, integrity protection, replay detection, and
   confidentiality.

4.4.1.4 PROTO_IPCOMP

   The PROTO_IPCOMP type specifies IP payload compression as defined in
   [IPCOMP].

4.4.2 IPSEC ISAKMP Transform Identifiers

   As part of an ISAKMP Phase I negotiation, the initiator's choice of
   Key Exchange offerings is made using some host system policy
   description.  The actual selection of Key Exchange mechanism is made
   using the standard ISAKMP Proposal Payload.  The following table
   lists the defined ISAKMP Phase I Transform Identifiers for the
   Proposal Payload for the IPSEC DOI.

       Transform                           Value
       ---------                           -----
       RESERVED                            0
       KEY_IKE                             1

   Within the ISAKMP and IPSEC DOI framework it is possible to define
   key establishment protocols other than IKE (Oakley).  Previous
   versions of this document defined types both for manual keying and
   for schemes based on use of a generic Key Distribution Center (KDC).
   These identifiers have been removed from the current document.

   The IPSEC DOI can still be extended later to include values for
   additional non-Oakley key establishment protocols for ISAKMP and
   IPSEC, such as Kerberos [RFC-1510] or the Group Key Management
   Protocol (GKMP) [RFC-2093].

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4.4.2.1 KEY_IKE

   The KEY_IKE type specifies the hybrid ISAKMP/Oakley Diffie-Hellman
   key exchange (IKE) as defined in the [IKE] document.  All
   implementations within the IPSEC DOI MUST support KEY_IKE.

4.4.3 IPSEC AH Transform Identifiers

   The Authentication Header Protocol (AH) defines one mandatory and
   several optional transforms used to provide authentication,
   integrity, and replay detection.  The following table lists the
   defined AH Transform Identifiers for the ISAKMP Proposal Payload for
   the IPSEC DOI.

   Note: the Authentication Algorithm attribute MUST be specified to
   identify the appropriate AH protection suite.  For example, AH_MD5
   can best be thought of as a generic AH transform using MD5.  To
   request the HMAC construction with AH, one specifies the AH_MD5
   transform ID along with the Authentication Algorithm attribute set to
   HMAC-MD5.  This is shown using the "Auth(HMAC-MD5)" notation in the
   following sections.

       Transform ID                        Value
       ------------                        -----
       RESERVED                            0-1
       AH_MD5                              2
       AH_SHA                              3
       AH_DES                              4

   Note: all mandatory-to-implement algorithms are listed as "MUST"
   implement (e.g. AH_MD5) in the following sections.  All other
   algorithms are optional and MAY be implemented in any particular
   implementation.

4.4.3.1 AH_MD5

   The AH_MD5 type specifies a generic AH transform using MD5.  The
   actual protection suite is determined in concert with an associated
   SA attribute list.  A generic MD5 transform is currently undefined.

   All implementations within the IPSEC DOI MUST support AH_MD5 along
   with the Auth(HMAC-MD5) attribute.  This suite is defined as the
   HMAC-MD5-96 transform described in [HMACMD5].

   The AH_MD5 type along with the Auth(KPDK) attribute specifies the AH
   transform (Key/Pad/Data/Key) described in RFC-1826.

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   Use of AH_MD5 with any other Authentication Algorithm attribute value
   is currently undefined.

4.4.3.2 AH_SHA

   The AH_SHA type specifies a generic AH transform using SHA-1.  The
   actual protection suite is determined in concert with an associated
   SA attribute list.  A generic SHA transform is currently undefined.

   All implementations within the IPSEC DOI MUST support AH_SHA along
   with the Auth(HMAC-SHA) attribute.  This suite is defined as the
   HMAC-SHA-1-96 transform described in [HMACSHA].

   Use of AH_SHA with any other Authentication Algorithm attribute value
   is currently undefined.

4.4.3.3 AH_DES

   The AH_DES type specifies a generic AH transform using DES.  The
   actual protection suite is determined in concert with an associated
   SA attribute list.  A generic DES transform is currently undefined.

   The IPSEC DOI defines AH_DES along with the Auth(DES-MAC) attribute
   to be a DES-MAC transform.  Implementations are not required to
   support this mode.

   Use of AH_DES with any other Authentication Algorithm attribute value
   is currently undefined.

4.4.4 IPSEC ESP Transform Identifiers

   The Encapsulating Security Payload (ESP) defines one mandatory and
   many optional transforms used to provide data confidentiality.  The
   following table lists the defined ESP Transform Identifiers for the
   ISAKMP Proposal Payload for the IPSEC DOI.

   Note: when authentication, integrity protection, and replay detection
   are required, the Authentication Algorithm attribute MUST be
   specified to identify the appropriate ESP protection suite.  For
   example, to request HMAC-MD5 authentication with 3DES, one specifies
   the ESP_3DES transform ID with the Authentication Algorithm attribute
   set to HMAC-MD5.  For additional processing requirements, see Section
   4.5 (Authentication Algorithm).

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       Transform ID                        Value
       ------------                        -----
       RESERVED                            0
       ESP_DES_IV64                        1
       ESP_DES                             2
       ESP_3DES                            3
       ESP_RC5                             4
       ESP_IDEA                            5
       ESP_CAST                            6
       ESP_BLOWFISH                        7
       ESP_3IDEA                           8
       ESP_DES_IV32                        9
       ESP_RC4                             10
       ESP_NULL                            11

   Note: all mandatory-to-implement algorithms are listed as "MUST"
   implement (e.g. ESP_DES) in the following sections.  All other
   algorithms are optional and MAY be implemented in any particular
   implementation.

4.4.4.1 ESP_DES_IV64

   The ESP_DES_IV64 type specifies the DES-CBC transform defined in
   RFC-1827 and RFC-1829 using a 64-bit IV.

4.4.4.2 ESP_DES

   The ESP_DES type specifies a generic DES transform using DES-CBC.
   The actual protection suite is determined in concert with an
   associated SA attribute list.  A generic transform is currently
   undefined.

   All implementations within the IPSEC DOI MUST support ESP_DES along
   with the Auth(HMAC-MD5) attribute.  This suite is defined as the
   [DES] transform, with authentication and integrity provided by HMAC
   MD5 [HMACMD5].

4.4.4.3 ESP_3DES

   The ESP_3DES type specifies a generic triple-DES transform.  The
   actual protection suite is determined in concert with an associated
   SA attribute list.  The generic transform is currently undefined.

   All implementations within the IPSEC DOI are strongly encouraged to
   support ESP_3DES along with the Auth(HMAC-MD5) attribute.  This suite
   is defined as the [ESPCBC] transform, with authentication and
   integrity provided by HMAC MD5 [HMACMD5].

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4.4.4.4 ESP_RC5

   The ESP_RC5 type specifies the RC5 transform defined in [ESPCBC].

4.4.4.5 ESP_IDEA

   The ESP_IDEA type specifies the IDEA transform defined in [ESPCBC].

4.4.4.6 ESP_CAST

   The ESP_CAST type specifies the CAST transform defined in [ESPCBC].

4.4.4.7 ESP_BLOWFISH

   The ESP_BLOWFISH type specifies the BLOWFISH transform defined in
   [ESPCBC].

4.4.4.8 ESP_3IDEA

   The ESP_3IDEA type is reserved for triple-IDEA.

4.4.4.9 ESP_DES_IV32

   The ESP_DES_IV32 type specifies the DES-CBC transform defined in
   RFC-1827 and RFC-1829 using a 32-bit IV.

4.4.4.10 ESP_RC4

   The ESP_RC4 type is reserved for RC4.

4.4.4.11 ESP_NULL

   The ESP_NULL type specifies no confidentiality is to be provided by
   ESP.  ESP_NULL is used when ESP is being used to tunnel packets which
   require only authentication, integrity protection, and replay
   detection.

   All implementations within the IPSEC DOI MUST support ESP_NULL.  The
   ESP NULL transform is defined in [ESPNULL].  See the Authentication
   Algorithm attribute description in Section 4.5 for additional
   requirements relating to the use of ESP_NULL.

4.4.5 IPSEC IPCOMP Transform Identifiers

   The IP Compression (IPCOMP) transforms define optional compression
   algorithms that can be negotiated to provide for IP payload
   compression ([IPCOMP]).  The following table lists the defined IPCOMP
   Transform Identifiers for the ISAKMP Proposal Payload within the

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   IPSEC DOI.

       Transform ID                        Value
       ------------                        -----
       RESERVED                            0
       IPCOMP_OUI                          1
       IPCOMP_DEFLATE                      2
       IPCOMP_LZS                          3

4.4.5.1 IPCOMP_OUI

   The IPCOMP_OUI type specifies a proprietary compression transform.
   The IPCOMP_OUI type must be accompanied by an attribute which further
   identifies the specific vendor algorithm.

4.4.5.2 IPCOMP_DEFLATE

   The IPCOMP_DEFLATE type specifies the use of the "zlib" deflate
   algorithm as specified in [DEFLATE].

4.4.5.3 IPCOMP_LZS

   The IPCOMP_LZS type specifies the use of the Stac Electronics LZS
   algorithm as specified in [LZS].

4.5 IPSEC Security Association Attributes

   The following SA attribute definitions are used in Phase II of an IKE
   negotiation.  Attribute types can be either Basic (B) or Variable-
   Length (V).  Encoding of these attributes is defined in the base
   ISAKMP specification.

   Attributes described as basic MUST NOT be encoded as variable.
   Variable length attributes MAY be encoded as basic attributes if
   their value can fit into two octets.  See [IKE] for further
   information on attribute encoding in the IPSEC DOI.  All restrictions
   listed in [IKE] also apply to the IPSEC DOI.

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       Attribute Types

             class               value           type
       -------------------------------------------------
       SA Life Type                1               B
       SA Life Duration            2               V
       Group Description           3               B
       Encapsulation Mode          4               B
       Authentication Algorithm    5               B
       Key Length                  6               B
       Key Rounds                  7               B
       Compress Dictionary Size    8               B
       Compress Private Algorithm  9               V

       Class Values

         SA Life Type
         SA Duration

           Specifies the time-to-live for the overall security
           association.  When the SA expires, all keys negotiated under
           the association (AH or ESP) must be renegotiated.  The life
           type values are:

           RESERVED                0
           seconds                 1
           kilobytes               2

           Values 3-61439 are reserved to IANA.  Values 61440-65535 are
           for private use.  For a given Life Type, the value of the
           Life Duration attribute defines the actual length of the
           component lifetime -- either a number of seconds, or a number
           of Kbytes that can be protected.

           If unspecified, the default value shall be assumed to be
           28800 seconds (8 hours).

           An SA Life Duration attribute MUST always follow an SA Life
           Type which describes the units of duration.

           See Section 4.5.4 for additional information relating to
           lifetime notification.

         Group Description

           Specifies the Oakley Group to be used in a PFS QM
           negotiation.  For a list of supported values, see Appendix A
           of [IKE].

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         Encapsulation Mode
           RESERVED                0
           Tunnel                  1
           Transport               2

           Values 3-61439 are reserved to IANA.  Values 61440-65535 are
           for private use.

           If unspecified, the default value shall be assumed to be
           unspecified (host-dependent).

         Authentication Algorithm
           RESERVED                0
           HMAC-MD5                1
           HMAC-SHA                2
           DES-MAC                 3
           KPDK                    4

           Values 5-61439 are reserved to IANA.  Values 61440-65535 are
           for private use.

           There is no default value for Auth Algorithm, as it must be
           specified to correctly identify the applicable AH or ESP
           transform, except in the following case.

           When negotiating ESP without authentication, the Auth
           Algorithm attribute MUST NOT be included in the proposal.

           When negotiating ESP without confidentiality, the Auth
           Algorithm attribute MUST be included in the proposal and the
           ESP transform ID must be ESP_NULL.

         Key Length
           RESERVED                0

           There is no default value for Key Length, as it must be
           specified for transforms using ciphers with variable key
           lengths.  For fixed length ciphers, the Key Length attribute
           MUST NOT be sent.

         Key Rounds
           RESERVED                0

           There is no default value for Key Rounds, as it must be
           specified for transforms using ciphers with varying numbers
           of rounds.

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         Compression Dictionary Size
           RESERVED                0

           Specifies the log2 maximum size of the dictionary.

           There is no default value for dictionary size.

         Compression Private Algorithm

           Specifies a private vendor compression algorithm.  The first
           three (3) octets must be an IEEE assigned company_id (OUI).
           The next octet may be a vendor specific compression subtype,
           followed by zero or more octets of vendor data.

4.5.1 Required Attribute Support

   To ensure basic interoperability, all implementations MUST be
   prepared to negotiate all of the following attributes.

           SA Life Type
           SA Duration
           Auth Algorithm

4.5.2 Attribute Parsing Requirement (Lifetime)

   To allow for flexible semantics, the IPSEC DOI requires that a
   conforming ISAKMP implementation MUST correctly parse an attribute
   list that contains multiple instances of the same attribute class, so
   long as the different attribute entries do not conflict with one
   another.  Currently, the only attributes which requires this
   treatment are Life Type and Duration.

   To see why this is important, the following example shows the binary
   encoding of a four entry attribute list that specifies an SA Lifetime
   of either 100MB or 24 hours.  (See Section 3.3 of [ISAKMP] for a
   complete description of the attribute encoding format.)

     Attribute #1:
       0x80010001  (AF = 1, type = SA Life Type, value = seconds)

     Attribute #2:
       0x00020004  (AF = 0, type = SA Duration, length = 4 bytes)
       0x00015180  (value = 0x15180 = 86400 seconds = 24 hours)

     Attribute #3:
       0x80010002  (AF = 1, type = SA Life Type, value = KB)

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     Attribute #4:
       0x00020004  (AF = 0, type = SA Duration, length = 4 bytes)
       0x000186A0  (value = 0x186A0 = 100000KB = 100MB)

   If conflicting attributes are detected, an ATTRIBUTES-NOT-SUPPORTED
   Notification Payload SHOULD be returned and the security association
   setup MUST be aborted.

4.5.3 Attribute Negotiation

   If an implementation receives a defined IPSEC DOI attribute (or
   attribute value) which it does not support, an ATTRIBUTES-NOT-SUPPORT
   SHOULD be sent and the security association setup MUST be aborted,
   unless the attribute value is in the reserved range.

   If an implementation receives an attribute value in the reserved
   range, an implementation MAY chose to continue based on local policy.

4.5.4 Lifetime Notification

   When an initiator offers an SA lifetime greater than what the
   responder desires based on their local policy, the responder has
   three choices: 1) fail the negotiation entirely; 2) complete the
   negotiation but use a shorter lifetime than what was offered; 3)
   complete the negotiation and send an advisory notification to the
   initiator indicating the responder's true lifetime.  The choice of
   what the responder actually does is implementation specific and/or
   based on local policy.

   To ensure interoperability in the latter case, the IPSEC DOI requires
   the following only when the responder wishes to notify the initiator:
   if the initiator offers an SA lifetime longer than the responder is
   willing to accept, the responder SHOULD include an ISAKMP
   Notification Payload in the exchange that includes the responder's
   IPSEC SA payload.  Section 4.6.3.1 defines the payload layout for the
   RESPONDER-LIFETIME Notification Message type which MUST be used for
   this purpose.

4.6 IPSEC Payload Content

   The following sections describe those ISAKMP payloads whose data
   representations are dependent on the applicable DOI.

4.6.1 Security Association Payload

   The following diagram illustrates the content of the Security
   Association Payload for the IPSEC DOI.  See Section 4.2 for a
   description of the Situation bitmap.

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    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !  Next Payload !   RESERVED    !        Payload Length         !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !                Domain of Interpretation (IPSEC)               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !                       Situation (bitmap)                      !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !                    Labeled Domain Identifier                  !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !  Secrecy Length (in octets)   !           RESERVED            !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Secrecy Level                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Secrecy Cat. Length (in bits) !           RESERVED            !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                    Secrecy Category Bitmap                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Integrity Length (in octets)  !           RESERVED            !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                       Integrity Level                         ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ! Integ. Cat. Length (in bits)  !           RESERVED            !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                  Integrity Category Bitmap                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 1: Security Association Payload Format

   The Security Association Payload is defined as follows:

     o  Next Payload (1 octet) - Identifier for the payload type of
        the next payload in the message.  If the current payload is the
        last in the message, this field will be zero (0).

     o  RESERVED (1 octet) - Unused, must be zero (0).

     o  Payload Length (2 octets) - Length, in octets, of the current
        payload, including the generic header.

     o  Domain of Interpretation (4 octets) - Specifies the IPSEC DOI,
        which has been assigned the value one (1).

     o  Situation (4 octets) - Bitmask used to interpret the remainder
        of the Security Association Payload.  See Section 4.2 for a
        complete list of values.

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     o  Labeled Domain Identifier (4 octets) - IANA Assigned Number used
        to interpret the Secrecy and Integrity information.

     o  Secrecy Length (2 octets) - Specifies the length, in octets, of
        the secrecy level identifier, excluding pad bits.

     o  RESERVED (2 octets) - Unused, must be zero (0).

     o  Secrecy Level (variable length) - Specifies the mandatory
        secrecy level required.  The secrecy level MUST be padded with
        zero (0) to align on the next 32-bit boundary.

     o  Secrecy Category Length (2 octets) - Specifies the length, in
        bits, of the secrecy category (compartment) bitmap, excluding
        pad bits.

     o  RESERVED (2 octets) - Unused, must be zero (0).

     o  Secrecy Category Bitmap (variable length) - A bitmap used to
        designate secrecy categories (compartments) that are required.
        The bitmap MUST be padded with zero (0) to align on the next
        32-bit boundary.

     o  Integrity Length (2 octets) - Specifies the length, in octets,
        of the integrity level identifier, excluding pad bits.

     o  RESERVED (2 octets) - Unused, must be zero (0).

     o  Integrity Level (variable length) - Specifies the mandatory
        integrity level required.  The integrity level MUST be padded
        with zero (0) to align on the next 32-bit boundary.

     o  Integrity Category Length (2 octets) - Specifies the length, in
        bits, of the integrity category (compartment) bitmap, excluding
        pad bits.

     o  RESERVED (2 octets) - Unused, must be zero (0).

     o  Integrity Category Bitmap (variable length) - A bitmap used to
        designate integrity categories (compartments) that are required.
        The bitmap MUST be padded with zero (0) to align on the next
        32-bit boundary.

4.6.1.1 IPSEC Labeled Domain Identifiers

   The following table lists the assigned values for the Labeled Domain
   Identifier field contained in the Situation field of the Security
   Association Payload.

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       Domain                              Value
       -------                             -----
       RESERVED                            0

4.6.2 Identification Payload Content

   The Identification Payload is used to identify the initiator of the
   Security Association.  The identity of the initiator SHOULD be used
   by the responder to determine the correct host system security policy
   requirement for the association.  For example, a host might choose to
   require authentication and integrity without confidentiality (AH)
   from a certain set of IP addresses and full authentication with
   confidentiality (ESP) from another range of IP addresses.  The
   Identification Payload provides information that can be used by the
   responder to make this decision.

   During Phase I negotiations, the ID port and protocol fields MUST be
   set to zero or to UDP port 500.  If an implementation receives any
   other values, this MUST be treated as an error and the security
   association setup MUST be aborted.  This event SHOULD be auditable.

   The following diagram illustrates the content of the Identification
   Payload.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !  Next Payload !   RESERVED    !        Payload Length         !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   !   ID Type     !  Protocol ID  !             Port              !
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                     Identification Data                       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 2: Identification Payload Format

   The Identification Payload fields are defined as follows:

     o  Next Payload (1 octet) - Identifier for the payload type of
        the next payload in the message.  If the current payload is the
        last in the message, this field will be zero (0).

     o  RESERVED (1 octet) - Unused, must be zero (0).

     o  Payload Length (2 octets) - Length, in octets, of the
        identification data, including the generic header.

     o  Identification Type (1 octet) - Value describing the identity
        information found in the Identification Data field.

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     o  Protocol ID (1 octet) - Value specifying an associated IP
        protocol ID (e.g. UDP/TCP).  A value of zero means that the
        Protocol ID field should be ignored.

     o  Port (2 octets) - Value specifying an associated port.  A value
        of zero means that the Port field should be ignored.

     o  Identification Data (variable length) - Value, as indicated by
        the Identification Type.

4.6.2.1 Identification Type Values

   The following table lists the assigned values for the Identification
   Type field found in the Identification Payload.

       ID Type                   Value
       -------                   -----
       RESERVED                            0
       ID_IPV4_ADDR                        1
       ID_FQDN                             2
       ID_USER_FQDN                        3
       ID_IPV4_ADDR_SUBNET                 4
       ID_IPV6_ADDR                        5
       ID_IPV6_ADDR_SUBNET                 6
       ID_IPV4_ADDR_RANGE                  7
       ID_IPV6_ADDR_RANGE                  8
       ID_DER_ASN1_DN                      9
       ID_DER_ASN1_GN                      10
       ID_KEY_ID                           11

   For types where the ID entity is variable length, the size of the ID
   entity is computed from size in the ID payload header.

   When an IKE exchange is authenticated using certificates (of any
   format), any ID's used for input to local policy decisions SHOULD be
   contained in the certificate used in the authentication of the
   exchange.

4.6.2.2 ID_IPV4_ADDR

   The ID_IPV4_ADDR type specifies a single four (4) octet IPv4 address.

4.6.2.3 ID_FQDN

   The ID_FQDN type specifies a fully-qualified domain name string.  An
   example of a ID_FQDN is, "foo.bar.com".  The string should not
   contain any terminators.

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4.6.2.4 ID_USER_FQDN

   The ID_USER_FQDN type specifies a fully-qualified username string, An
   example of a ID_USER_FQDN is, "piper@foo.bar.com".  The string should
   not contain any terminators.

4.6.2.5 ID_IPV4_ADDR_SUBNET

   The ID_IPV4_ADDR_SUBNET type specifies a range of IPv4 addresses,
   represented by two four (4) octet values.  The first value is an IPv4
   address.  The second is an IPv4 network mask.  Note that ones (1s) in
   the network mask indicate that the corresponding bit in the address
   is fixed, while zeros (0s) indicate a "wildcard" bit.

4.6.2.6 ID_IPV6_ADDR

   The ID_IPV6_ADDR type specifies a single sixteen (16) octet IPv6
   address.

4.6.2.7 ID_IPV6_ADDR_SUBNET

   The ID_IPV6_ADDR_SUBNET type specifies a range of IPv6 addresses,
   represented by two sixteen (16) octet values.  The first value is an
   IPv6 address.  The second is an IPv6 network mask.  Note that ones
   (1s) in the network mask indicate that the corresponding bit in the
   address is fixed, while zeros (0s) indicate a "wildcard" bit.

4.6.2.8 ID_IPV4_ADDR_RANGE

   The ID_IPV4_ADDR_RANGE type specifies a range of IPv4 addresses,
   represented by two four (4) octet values.  The first value is the
   beginning IPv4 address (inclusive) and the second value is the ending
   IPv4 address (inclusive).  All addresses falling between the two
   specified addresses are considered to be within the list.

4.6.2.9 ID_IPV6_ADDR_RANGE

   The ID_IPV6_ADDR_RANGE type specifies a range of IPv6 addresses,
   represented by two sixteen (16) octet values.  The first value is the
   beginning IPv6 address (inclusive) and the second value is the ending
   IPv6 address (inclusive).  All addresses falling between the two
   specified addresses are considered to be within the list.

4.6.2.10 ID_DER_ASN1_DN

   The ID_DER_ASN1_DN type specifies the binary DER encoding of an ASN.1
   X.500 Distinguished Name [X.501] of the principal whose certificates
   are being exchanged to establish the SA.

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4.6.2.11 ID_DER_ASN1_GN

   The ID_DER_ASN1_GN type specifies the binary DER encoding of an ASN.1
   X.500 GeneralName [X.509] of the principal whose certificates are
   being exchanged to establish the SA.

4.6.2.12 ID_KEY_ID

   The ID_KEY_ID type specifies an opaque byte stream which may be used
   to pass vendor-specific information necessary to identify which pre-
   shared key should be used to authenticate Aggressive mode
   negotiations.

4.6.3 IPSEC Notify Message Types

   ISAKMP defines two blocks of Notify Message codes, one for errors and
   one for status messages.  ISAKMP also allocates a portion of each
   block for private use within a DOI.  The IPSEC DOI defines the
   following private message types for its own use.

       Notify Messages - Error Types       Value
       -----------------------------       -----
       RESERVED                            8192

       Notify Messages - Status Types      Value
       ------------------------------      -----
       RESPONDER-LIFETIME                  24576
       REPLAY-STATUS                       24577
       INITIAL-CONTACT                     24578

   Notification Status Messages MUST be sent under the protection of an
   ISAKMP SA: either as a payload in the last Main Mode exchange; in a
   separate Informational Exchange after Main Mode or Aggressive Mode
   processing is complete; or as a payload in any Quick Mode exchange.
   These messages MUST NOT be sent in Aggressive Mode exchange, since
   Aggressive Mode does not provide the necessary protection to bind the
   Notify Status Message to the exchange.

   Nota Bene: a Notify payload is fully protected only in Quick Mode,
   where the entire payload is included in the HASH(n) digest.  In Main
   Mode, while the notify payload is encrypted, it is not currently
   included in the HASH(n) digests.  As a result, an active substitution
   attack on the Main Mode ciphertext could cause the notify status
   message type to be corrupted.  (This is true, in general, for the
   last message of any Main Mode exchange.)  While the risk is small, a
   corrupt notify message might cause the receiver to abort the entire
   negotiation thinking that the sender encountered a fatal error.

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   Implementation Note: the ISAKMP protocol does not guarantee delivery
   of Notification Status messages when sent in an ISAKMP Informational
   Exchange.  To ensure receipt of any particular message, the sender
   SHOULD include a Notification Payload in a defined Main Mode or Quick
   Mode exchange which is protected by a retransmission timer.

4.6.3.1 RESPONDER-LIFETIME

   The RESPONDER-LIFETIME status message may be used to communicate the
   IPSEC SA lifetime chosen by the responder.

   When present, the Notification Payload MUST have the following
   format:

     o  Payload Length - set to length of payload + size of data (var)
     o  DOI - set to IPSEC DOI (1)
     o  Protocol ID - set to selected Protocol ID from chosen SA
     o  SPI Size - set to either sixteen (16) (two eight-octet ISAKMP
        cookies) or four (4) (one IPSEC SPI)
     o  Notify Message Type - set to RESPONDER-LIFETIME (Section 4.6.3)
     o  SPI - set to the two ISAKMP cookies or to the sender's inbound
        IPSEC SPI
     o  Notification Data - contains an ISAKMP attribute list with the
        responder's actual SA lifetime(s)

   Implementation Note: saying that the Notification Data field contains
   an attribute list is equivalent to saying that the Notification Data
   field has zero length and the Notification Payload has an associated
   attribute list.

4.6.3.2 REPLAY-STATUS

   The REPLAY-STATUS status message may be used for positive
   confirmation of the responder's election on whether or not he is to
   perform anti-replay detection.

   When present, the Notification Payload MUST have the following
   format:

     o  Payload Length - set to length of payload + size of data (4)
     o  DOI - set to IPSEC DOI (1)
     o  Protocol ID - set to selected Protocol ID from chosen SA
     o  SPI Size - set to either sixteen (16) (two eight-octet ISAKMP
        cookies) or four (4) (one IPSEC SPI)
     o  Notify Message Type - set to REPLAY-STATUS
     o  SPI - set to the two ISAKMP cookies or to the sender's inbound
        IPSEC SPI
     o  Notification Data - a 4 octet value:

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          0 = replay detection disabled
          1 = replay detection enabled

4.6.3.3 INITIAL-CONTACT

   The INITIAL-CONTACT status message may be used when one side wishes
   to inform the other that this is the first SA being established with
   the remote system.  The receiver of this Notification Message might
   then elect to delete any existing SA's it has for the sending system
   under the assumption that the sending system has rebooted and no
   longer has access to the original SA's and their associated keying
   material.  When used, the content of the Notification Data field
   SHOULD be null (i.e. the Payload Length should be set to the fixed
   length of Notification Payload).

   When present, the Notification Payload MUST have the following
   format:

     o  Payload Length - set to length of payload + size of data (0)
     o  DOI - set to IPSEC DOI (1)
     o  Protocol ID - set to selected Protocol ID from chosen SA
     o  SPI Size - set to sixteen (16) (two eight-octet ISAKMP cookies)
     o  Notify Message Type - set to INITIAL-CONTACT
     o  SPI - set to the two ISAKMP cookies
     o  Notification Data - <not included>

4.7 IPSEC Key Exchange Requirements

   The IPSEC DOI introduces no additional Key Exchange types.

5. Security Considerations

   This entire memo pertains to the Internet Key Exchange protocol
   ([IKE]), which combines ISAKMP ([ISAKMP]) and Oakley ([OAKLEY]) to
   provide for the derivation of cryptographic keying material in a
   secure and authenticated manner.  Specific discussion of the various
   security protocols and transforms identified in this document can be
   found in the associated base documents and in the cipher references.

6. IANA Considerations

   This document contains many "magic" numbers to be maintained by the
   IANA.  This section explains the criteria to be used by the IANA to
   assign additional numbers in each of these lists.  All values not
   explicitly defined in previous sections are reserved to IANA.

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6.1 IPSEC Situation Definition

   The Situation Definition is a 32-bit bitmask which represents the
   environment under which the IPSEC SA proposal and negotiation is
   carried out.  Requests for assignments of new situations must be
   accompanied by an RFC which describes the interpretation for the
   associated bit.

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The upper two bits are reserved for private use amongst cooperating
   systems.

6.2 IPSEC Security Protocol Identifiers

   The Security Protocol Identifier is an 8-bit value which identifies a
   security protocol suite being negotiated.  Requests for assignments
   of new security protocol identifiers must be accompanied by an RFC
   which describes the requested security protocol.  [AH] and [ESP] are
   examples of security protocol documents.

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The values 249-255 are reserved for private use amongst cooperating
   systems.

6.3 IPSEC ISAKMP Transform Identifiers

   The IPSEC ISAKMP Transform Identifier is an 8-bit value which
   identifies a key exchange protocol to be used for the negotiation.
   Requests for assignments of new ISAKMP transform identifiers must be
   accompanied by an RFC which describes the requested key exchange
   protocol.  [IKE] is an example of one such document.

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The values 249-255 are reserved for private use amongst cooperating
   systems.

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6.4 IPSEC AH Transform Identifiers

   The IPSEC AH Transform Identifier is an 8-bit value which identifies
   a particular algorithm to be used to provide integrity protection for
   AH.  Requests for assignments of new AH transform identifiers must be
   accompanied by an RFC which describes how to use the algorithm within
   the AH framework ([AH]).

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The values 249-255 are reserved for private use amongst cooperating
   systems.

6.5 IPSEC ESP Transform Identifiers

   The IPSEC ESP Transform Identifier is an 8-bit value which identifies
   a particular algorithm to be used to provide secrecy protection for
   ESP.  Requests for assignments of new ESP transform identifiers must
   be accompanied by an RFC which describes how to use the algorithm
   within the ESP framework ([ESP]).

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The values 249-255 are reserved for private use amongst cooperating
   systems.

6.6 IPSEC IPCOMP Transform Identifiers

   The IPSEC IPCOMP Transform Identifier is an 8-bit value which
   identifier a particular algorithm to be used to provide IP-level
   compression before ESP.  Requests for assignments of new IPCOMP
   transform identifiers must be accompanied by an RFC which describes
   how to use the algorithm within the IPCOMP framework ([IPCOMP]).  In
   addition, the requested algorithm must be published and in the public
   domain.

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

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   The values 1-47 are reserved for algorithms for which an RFC has been
   approved for publication.  The values 48-63 are reserved for private
   use amongst cooperating systems.  The values 64-255 are reserved for
   future expansion.

6.7 IPSEC Security Association Attributes

   The IPSEC Security Association Attribute consists of a 16-bit type
   and its associated value.  IPSEC SA attributes are used to pass
   miscellaneous values between ISAKMP peers.  Requests for assignments
   of new IPSEC SA attributes must be accompanied by an Internet Draft
   which describes the attribute encoding (Basic/Variable-Length) and
   its legal values.  Section 4.5 of this document provides an example
   of such a description.

   The values 32001-32767 are reserved for private use amongst
   cooperating systems.

6.8 IPSEC Labeled Domain Identifiers

   The IPSEC Labeled Domain Identifier is a 32-bit value which
   identifies a namespace in which the Secrecy and Integrity levels and
   categories values are said to exist.  Requests for assignments of new
   IPSEC Labeled Domain Identifiers should be granted on demand.  No
   accompanying documentation is required, though Internet Drafts are
   encouraged when appropriate.

   The values 0x80000000-0xffffffff are reserved for private use amongst
   cooperating systems.

6.9 IPSEC Identification Type

   The IPSEC Identification Type is an 8-bit value which is used as a
   discriminant for interpretation of the variable-length Identification
   Payload.  Requests for assignments of new IPSEC Identification Types
   must be accompanied by an RFC which describes how to use the
   identification type within IPSEC.

   If the RFC is not on the standards-track (i.e., it is an
   informational or experimental RFC), it must be explicitly reviewed
   and approved by the IESG before the RFC is published and the
   transform identifier is assigned.

   The values 249-255 are reserved for private use amongst cooperating
   systems.

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6.10 IPSEC Notify Message Types

   The IPSEC Notify Message Type is a 16-bit value taken from the range
   of values reserved by ISAKMP for each DOI.  There is one range for
   error messages (8192-16383) and a different range for status messages
   (24576-32767).  Requests for assignments of new Notify Message Types
   must be accompanied by an Internet Draft which describes how to use
   the identification type within IPSEC.

   The values 16001-16383 and the values 32001-32767 are reserved for
   private use amongst cooperating systems.

7. Change Log

7.1 Changes from V9

     o  add explicit reference to [IPCOMP], [DEFLATE], and [LZS]
     o  allow RESPONDER-LIFETIME and REPLAY-STATUS to be directed
        at an IPSEC SPI in addition to the ISAKMP "SPI"
     o  added padding exclusion to Secrecy and Integrity Length text
     o  added forward reference to Section 4.5 in Section 4.4.4
     o  update document references

7.2 Changes from V8

     o  update IPCOMP identifier range to better reflect IPCOMP draft
     o  update IANA considerations per Jeff/Ted's suggested text
     o  eliminate references to DES-MAC ID ([DESMAC])
     o  correct bug in Notify section; ISAKMP Notify values are 16-bits

7.3 Changes from V7

     o  corrected name of IPCOMP (IP Payload Compression)
     o  corrected references to [ESPCBC]
     o  added missing Secrecy Level and Integrity Level to Figure 1
     o  removed ID references to PF_KEY and ARCFOUR
     o  updated Basic/Variable text to align with [IKE]
     o  updated document references and add intro pointer to [ARCH]
     o  updated Notification requirements; remove aggressive reference
     o  added clarification about protection for Notify payloads
     o  restored RESERVED to ESP transform ID namespace; moved ESP_NULL
     o  added requirement for ESP_NULL support and [ESPNULL] reference
     o  added clarification on Auth Alg use with AH/ESP
     o  added restriction against using conflicting AH/Auth combinations

7.4 Changes from V6

   The following changes were made relative to the IPSEC DOI V6:

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     o  added IANA Considerations section
     o  moved most IANA numbers to IANA Considerations section
     o  added prohibition on sending (V) encoding for (B) attributes
     o  added prohibition on sending Key Length attribute for fixed
        length ciphers (e.g. DES)
     o  replaced references to ISAKMP/Oakley with IKE
     o  renamed ESP_ARCFOUR to ESP_RC4
     o  updated Security Considerations section
     o  updated document references

7.5 Changes from V5

   The following changes were made relative to the IPSEC DOI V5:

     o  changed SPI size in Lifetime Notification text
     o  changed REPLAY-ENABLED to REPLAY-STATUS
     o  moved RESPONDER-LIFETIME payload definition from Section 4.5.4
        to Section 4.6.3.1
     o  added explicit payload layout for 4.6.3.3
     o  added Implementation Note to Section 4.6.3 introduction
     o  changed AH_SHA text to require SHA-1 in addition to MD5
     o  updated document references

7.6 Changes from V4

   The following changes were made relative to the IPSEC DOI V4:

     o  moved compatibility AH KPDK authentication method from AH
        transform ID to Authentication Algorithm identifier
     o  added REPLAY-ENABLED notification message type per Architecture
     o  added INITIAL-CONTACT notification message type per list
     o  added text to ensure protection for Notify Status messages
     o  added Lifetime qualification to attribute parsing section
     o  added clarification that Lifetime notification is optional
     o  removed private Group Description list (now points at [IKE])
     o  replaced Terminology with pointer to RFC-2119
     o  updated HMAC MD5 and SHA-1 ID references
     o  updated Section 1 (Abstract)
     o  updated Section 4.4 (IPSEC Assigned Numbers)
     o  added restriction for ID port/protocol values for Phase I

7.7 Changes from V3 to V4

   The following changes were made relative to the IPSEC DOI V3, that
   was posted to the IPSEC mailing list prior to the Munich IETF:

     o  added ESP transform identifiers for NULL and ARCFOUR

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     o  renamed HMAC Algorithm to Auth Algorithm to accommodate
        DES-MAC and optional authentication/integrity for ESP
     o  added AH and ESP DES-MAC algorithm identifiers
     o  removed KEY_MANUAL and KEY_KDC identifier definitions
     o  added lifetime duration MUST follow lifetype attribute to
        SA Life Type and SA Life Duration attribute definition
     o  added lifetime notification and IPSEC DOI message type table
     o  added optional authentication and confidentiality
        restrictions to MAC Algorithm attribute definition
     o  corrected attribute parsing example (used obsolete attribute)
     o  corrected several Internet Draft document references
     o  added ID_KEY_ID per ipsec list discussion (18-Mar-97)
     o  removed Group Description default for PFS QM ([IKE] MUST)

Acknowledgments

   This document is derived, in part, from previous works by Douglas
   Maughan, Mark Schertler, Mark Schneider, Jeff Turner, Dan Harkins,
   and Dave Carrel.  Matt Thomas, Roy Pereira, Greg Carter, and Ran
   Atkinson also contributed suggestions and, in many cases, text.

References

   [AH]      Kent, S., and R. Atkinson, "IP Authentication Header", RFC
             2402, November 1998.

   [ARCH]    Kent, S., and R. Atkinson, "Security Architecture for the
             Internet Protocol", RFC 2401, November 1998.

   [DEFLATE] Pereira, R., "IP Payload Compression Using DEFLATE", RFC
             2394, August 1998.

   [ESP]     Kent, S., and R. Atkinson, "IP Encapsulating Security
             Payload (ESP)", RFC 2406, November 1998.

   [ESPCBC]  Pereira, R., and R. Adams, "The ESP CBC-Mode Cipher
             Algorithms", RFC 2451, November 1998.

   [ESPNULL] Glenn, R., and S. Kent, "The NULL Encryption Algorithm and
             Its Use With IPsec", RFC 2410, November 1998.

   [DES]     Madson, C., and N. Doraswamy, "The ESP DES-CBC Cipher
             Algorithm With Explicit IV", RFC 2405, November 1998.

   [HMACMD5] Madson, C., and R. Glenn, "The Use of HMAC-MD5 within ESP
             and AH", RFC 2403, November 1998.

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RFC 2407          IP Security Domain of Interpretation     November 1998

   [HMACSHA] Madson, C., and R. Glenn, "The Use of HMAC-SHA-1-96 within
             ESP and AH", RFC 2404, November 1998.

   [IKE]     Harkins, D., and D. Carrel, D., "The Internet Key Exchange
             (IKE)", RFC 2409, November 1998.

   [IPCOMP]  Shacham, A., Monsour, R., Pereira, R., and M. Thomas, "IP
             Payload Compression Protocol (IPComp)", RFC 2393, August
             1998.

   [ISAKMP]  Maughan, D., Schertler, M., Schneider, M., and J. Turner,
             "Internet Security Association and Key Management Protocol
             (ISAKMP)", RFC 2408, November 1998.

   [LZS]     Friend, R., and R. Monsour, "IP Payload Compression Using
             LZS", RFC 2395, August 1998.

   [OAKLEY]  Orman, H., "The OAKLEY Key Determination Protocol", RFC
             2412, November 1998.

   [X.501]   ISO/IEC 9594-2, "Information Technology - Open Systems
             Interconnection - The Directory:  Models", CCITT/ITU
             Recommendation X.501, 1993.

   [X.509]   ISO/IEC 9594-8, "Information Technology - Open Systems
             Interconnection - The Directory:  Authentication
             Framework", CCITT/ITU Recommendation X.509, 1993.

Author's Address

   Derrell Piper
   Network Alchemy
   1521.5 Pacific Ave
   Santa Cruz, California, 95060
   United States of America

   Phone: +1 408 460-3822
   EMail: ddp@network-alchemy.com

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Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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