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Versions: 00 01 02 03 04 05 06 07 RFC 4767

Intrusion Detection Exchange                                B. Feinstein
Format                                                    Guardent, Inc.
Internet-Draft                                               G. Matthews
Expires: March 26, 2003                    CSC/NASA Ames Research Center
                                                                J. White
                                                       MITRE Corporation
                                                      September 25, 2002


            The Intrusion Detection Exchange Protocol (IDXP)
                      draft-ietf-idwg-beep-idxp-06

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 26, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This memo describes the Intrusion Detection Exchange Protocol (IDXP),
   an application-level protocol for exchanging data between intrusion
   detection entities.  IDXP supports mutual-authentication, integrity,
   and confidentiality over a connection-oriented protocol.  The
   protocol provides for the exchange of IDMEF messages, unstructured
   text, and binary data.  The IDMEF message elements are described in
   the Intrusion Detection Message Exchange Format (IDMEF) [4], a
   companion document of the Intrusion Detection Exchange Format (IDWG)



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   working group of the IETF.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.1   Purpose  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.2   Profiles . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   1.3   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.    The Model  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   2.1   Connection Provisioning  . . . . . . . . . . . . . . . . . .  6
   2.2   Data Transfer  . . . . . . . . . . . . . . . . . . . . . . .  8
   2.3   Connection Teardown  . . . . . . . . . . . . . . . . . . . .  9
   2.4   Trust Model  . . . . . . . . . . . . . . . . . . . . . . . .  9
   3.    The IDXP Profile . . . . . . . . . . . . . . . . . . . . . . 11
   3.1   IDXP Profile Overview  . . . . . . . . . . . . . . . . . . . 11
   3.2   IDXP Profile Identification and Initialization . . . . . . . 11
   3.3   IDXP Profile Message Syntax  . . . . . . . . . . . . . . . . 12
   3.4   IDXP Profile Semantics . . . . . . . . . . . . . . . . . . . 12
   3.4.1 The IDXP-GREETING Element  . . . . . . . . . . . . . . . . . 12
   3.4.2 The OPTION Element . . . . . . . . . . . . . . . . . . . . . 14
   3.4.3 The IDMEF-MESSAGE Element  . . . . . . . . . . . . . . . . . 14
   4.    IDXP Options . . . . . . . . . . . . . . . . . . . . . . . . 15
   4.1   The channelPriority Option . . . . . . . . . . . . . . . . . 16
   4.2   The streamType Option  . . . . . . . . . . . . . . . . . . . 17
   5.    Fulfillment of IDWG Communications Protocol Requirements . . 20
   6.    IDXP Option Registration Template  . . . . . . . . . . . . . 23
   7.    Initial Registrations  . . . . . . . . . . . . . . . . . . . 24
   7.1   Registration: The IDXP Profile . . . . . . . . . . . . . . . 24
   7.2   Registration: The System (Well-Known) TCP port number
         for IDXP . . . . . . . . . . . . . . . . . . . . . . . . . . 24
   7.3   Registration: The channelPriority Option . . . . . . . . . . 24
   7.4   Registration: The streamType Option  . . . . . . . . . . . . 25
   8.    The DTDs . . . . . . . . . . . . . . . . . . . . . . . . . . 26
   8.1   The IDXP DTD . . . . . . . . . . . . . . . . . . . . . . . . 26
   8.2   The channelPriority Option DTD . . . . . . . . . . . . . . . 27
   8.3   The streamType DTD . . . . . . . . . . . . . . . . . . . . . 28
   9.    Reply Codes  . . . . . . . . . . . . . . . . . . . . . . . . 30
   10.   Security Considerations  . . . . . . . . . . . . . . . . . . 31
   10.1  Use of the TUNNEL Profile  . . . . . . . . . . . . . . . . . 31
   10.2  Use of Underlying Security Profiles  . . . . . . . . . . . . 31
         References . . . . . . . . . . . . . . . . . . . . . . . . . 32
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 32
   A.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . 34
   B.    History of Significant Changes . . . . . . . . . . . . . . . 35
   B.1   Significant Changes Since beep-idxp-05 . . . . . . . . . . . 35
   B.2   Significant Changes Since beep-idxp-04 . . . . . . . . . . . 35
   B.3   Significant Changes Since beep-idxp-03 . . . . . . . . . . . 35
   B.4   Significant Changes Since beep-idxp-02 . . . . . . . . . . . 35



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   B.5   Significant Changes Since beep-idxp-01 . . . . . . . . . . . 36
   B.6   Significant Changes Since beep-idxp-00 . . . . . . . . . . . 36
   C.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 38
         Full Copyright Statement . . . . . . . . . . . . . . . . . . 39















































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1. Introduction

   IDXP is specified, in part, as a Blocks Extensible Exchange Protocol
   (BEEP) [8] "profile".  BEEP is a generic application protocol
   framework for connection-oriented, asynchronous interactions.
   Features such as authentication and confidentiality are provided
   through the use of other BEEP profiles.  Accordingly, many aspects of
   IDXP (e.g., confidentiality) are provided within the BEEP framework.

1.1 Purpose

   IDXP provides for the exchange of IDMEF [4] messages, unstructured
   text, and binary data between intrusion detection entities.
   Addressing the security-sensitive nature of exchanges between
   intrusion detection entities, underlying BEEP security profiles
   should be used to offer IDXP the required set of security properties.
   See Section 5 for a discussion of how IDXP fulfills the IDWG
   communication protocol requirements.  See Section 10 for a discussion
   of security considerations.

   IDXP is primarily intended for the exchange of data created by
   intrusion detection entities.  IDMEF [4] messages should be used for
   the structured representation of this intrusion detection data,
   although IDXP may be used to exchange unstructured text and binary
   data.

1.2 Profiles

   There are several BEEP profiles discussed, the first of which we
   define in this memo:

      The IDXP Profile

      The TUNNEL Profile [7]

      The Simple Authentication and Security Layer (SASL) Family of
      Profiles (c.f., Section 4.1 of [8])

      The TLS Profile (c.f., Section 3.1 of [8])


1.3 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [2].

   Throughout this memo, the terms "analyzer" and "manager" are used in



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   the context of the Intrusion Detection Message Exchange Requirements
   [9].  In particular, Section 3.2 of [9] defines the meaning of a
   collection of intrusion detection terms.

   The terms "peer", "initiator", "listener", "client", and "server",
   and the characters "I", "L", "C", and "S" are used in the context of
   BEEP [8].  In particular, Section 2.1 of BEEP discusses the roles
   that a BEEP peer may perform.

   The term "Document Type Declaration" is abbreviated as "DTD" and is
   defined in Section 2.8 of the Extensible Markup Language (XML) [3].

   Note that the term "proxy" is specific to IDXP, and does not exist in
   the context of BEEP.  The term "intrusion detection" is abbreviated
   as "ID".




































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2. The Model

2.1 Connection Provisioning

   Intrusion detection entities using IDXP to transfer data are termed
   IDXP peers.  Peers can exist only in pairs, and these pairs
   communicate over a single BEEP session with one or more BEEP channels
   opened for transferring data.  Peers are either managers or
   analyzers, as defined in Section 3.2 of [9].

   The relationship between analyzers and managers is potentially many-
   to-many.  I.e., an analyzer MAY communicate with many managers;
   similarly, a manager MAY communicate with many analyzers.  Likewise,
   the relationship between different managers is potentially many-to-
   many, so that a manager MAY receive the alerts sent by a large number
   of analyzers by receiving them through intermediate managers.
   Analyzers MUST NOT establish IDXP exchanges with other analyzers.

   An IDXP peer wishing to establish IDXP communications with another
   IDXP peer does so by opening a BEEP channel, which may entail
   initiating a BEEP session.  A BEEP security profile offering the
   required security properties SHOULD initially be negotiated (see
   Section 10 for a discussion of security considerations).  Following
   the successful negotiation of the BEEP security profile, IDXP
   greetings are exchanged and connection provisioning proceeds.

   In the following sequence a peer 'Alice' initiates an IDXP exchange
   with the peer 'Bob'.

        Alice                                               Bob
          ---------------- xport connect[1] ------------------>
         <-------------------- greeting ---------------------->
         <-------------start security profile[2] ------------->
         <-------------------- greeting ---------------------->
         <------------------ start IDXP[3] ------------------->

   Notes:

   [1] 'Alice' initiates a transport connection to 'Bob', triggering the
      exchange of BEEP greeting messages.

   [2] both entities negotiate the use of a BEEP security profile.

   [3] both entities negotiate the use of the IDXP profile.

   In between a pair of IDXP peers may be an arbitrary number of
   proxies.  A proxy may be necessary for administrative reasons, such
   as running on a firewall to allow restricted access.  Another use



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   might be one proxy per company department, which forwards data from
   the analyzer peers in the department onto a company-wide manager
   peer.

   A BEEP tuning profile MAY be used to create an application-layer
   tunnel that transparently forwards data over a chain of proxies.  The
   TUNNEL profile [7] SHOULD be used for this purpose; see [7] for more
   detail concerning the options available to setup an application-layer
   tunnel using TUNNEL, and see Section 10.1 for a discussion of TUNNEL
   related security considerations.  TUNNEL MUST be offered as a tuning
   profile for the creation of application-layer tunnels.  The TUNNEL
   profile MUST offer the use of some form of SASL authentication (c.f.,
   Section 4.1 of [8]).  Once a tunnel has been created a BEEP security
   profile offering the required security properties SHOULD be
   negotiated, followed by negotiation of the IDXP profile.

   The following sequence shows how TUNNEL might be used to create an
   application-layer tunnel through which IDXP would operate.  A peer
   'Alice' initiates the creation of a BEEP session using the IDXP
   profile with the entity 'Bob' by first contacting 'proxy1'.  In the
   greeting exchange between 'Alice' and 'proxy1', the TUNNEL profile is
   selected, and subsequently the use of the TUNNEL profile is extended
   to reach through 'proxy2' to 'Bob'.

   Alice              proxy1               proxy2               Bob
     -- xport connect -->
    <---- greeting ----->
     -- start TUNNEL --->
                         - xport connect[1] ->
                        <----- greeting ----->
                         --- start TUNNEL --->
                                              --- xport connect -->
                                             <----- greeting ----->
                                              --- start TUNNEL --->
                                             <----- <ok>[2] ------
                        <------- <ok> -------
    <------ <ok> -------
    <------------------------- greeting -------------------------->
    <------------------ start security profile ------------------->
    <------------------------- greeting -------------------------->
    <------------------------ start IDXP ------------------------->

   Notes:

   [1] Instead of immediately acknowledging the request from 'Alice' to
      start TUNNEL, 'proxy1' attempts to establish use of TUNNEL with
      'proxy2'.  'proxy2' also delays its acknowledgment to 'proxy1'.




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   [2] 'Bob' acknowledges the request from 'proxy2' to start TUNNEL, and
      this acknowledgment propagates back to 'Alice' so that a TUNNEL
      application-layer tunnel is established from 'Alice' to 'Bob'.


2.2 Data Transfer

   Between a pair of ID entities communicating over a BEEP session, one
   or more BEEP channels MAY be opened using the IDXP profile.  If
   desired, additional BEEP sessions MAY be established to offer
   additional channels using the IDXP profile.  However, in most
   situations additional channels using the IDXP profile SHOULD be
   opened within an existing BEEP session, as opposed to provisioning a
   new BEEP session containing the additional channels using the IDXP
   profile.

   Peers assume the role of client or server on a per-channel basis,
   with one acting as the client and the other as the server.  A peer's
   role of client or server is determined independent of whether the
   peer assumed the role of initiator or listener during the BEEP
   session establishment.  Clients and servers act as sources and sinks,
   respectively, for exchanging data.

   In a simple case, an analyzer peer sends data to a manager peer.
   E.g.,

           +----------+                          +----------+
           |          |                          |          |
           |          |****** BEEP session ******|          |
           |          |                          |          |
           | Analyzer | ----- IDXP profile ----> | Manager  |
           | (Client) |                          | (Server) |
           |          |                          |          |
           |          |**************************|          |
           |          |                          |          |
           +----------+                          +----------+

   Use of multiple BEEP channels in a BEEP session facilitates
   categorization and prioritization of data sent between IDXP peers.
   For example, a manager 'M1', sending alert data to another manager,
   'M2', may choose to open a separate channel to exchange different
   categories of alerts.  'M1' would act as the client on each of these
   channels, and manager 'M2' can then process and act on the incoming
   alerts based on their respective channel categorizations.  See
   Section 4 for more detail on how to incorporate categorization and/or
   prioritization into channel creation.





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   +----------+                                            +----------+
   |          |                                            |          |
   |          |*************** BEEP session ***************|          |
   |          |                                            |          |
   |          | -- IDXP profile, network-based alerts ---> |          |
   | Manager  |                                            | Manager  |
   |   M1     | ---- IDXP profile, host-based alerts ----> |   M2     |
   | (Client) |                                            | (Server) |
   |          | ------ IDXP profile, other alerts -------> |          |
   |          |                                            |          |
   |          |********************************************|          |
   |          |                                            |          |
   +----------+                                            +----------+


2.3 Connection Teardown

   An IDXP peer may choose to close an IDXP channel under many different
   circumstances (e.g., an error in processing has occurred).  To close
   a channel, the peer sends a "close" element (c.f., Section 2.3.1.3 of
   [8]) on channel zero indicating which channel is being closed.  An
   IDXP peer may also choose to close an entire BEEP session by sending
   a "close" element indicating that channel zero is to be closed.
   Section 2.3.1.3 of [8] offers a more complete discussion of the
   circumstances under which a BEEP peer is permitted to close a channel
   and the mechanisms for doing so.

   It is anticipated that due to the overhead of provisioning an
   application-layer tunnel and/or a BEEP security profile, BEEP
   sessions containing IDXP channels will be long-lived.  Additionally,
   the repeated overhead of IDXP channel provisioning (i.e., the
   exchange of IDXP greetings) may be avoided by keeping IDXP channels
   open even while data is not actively being exchanged on them.  These
   are recommendations and, as such, IDXP peers may choose to close and
   re-provision BEEP sessions and/or IDXP channels as they see fit.

2.4 Trust Model

   In our model, trust is placed exclusively in the IDXP peers.  Proxies
   are always assumed to be untrustworthy.  A BEEP security profile is
   used to establish end-to-end security between pairs of IDXP peers,
   doing away with the need to place trust in any intervening proxies.
   Only after successful negotiation of the underlying security profile
   are IDXP peers to be trusted.  Only BEEP security profiles offering
   at least the protections required by Section 5 of [9] should be used
   to secure a BEEP session containing channels using the IDXP profile.
   See Section 3 of [8] for the registration of the TLS profile, an
   example of a BEEP security profile meeting the requirements of



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   Section 5 of [9].  See Section 5 for a discussion of how IDXP
   fulfills the IDWG communications protocol requirements.

















































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3. The IDXP Profile

3.1 IDXP Profile Overview

   The IDXP profile provides a mechanism for exchanging information
   between intrusion detection entities.  A BEEP tuning profile MAY be
   used to create an application-layer tunnel that transparently
   forwards data over a chain of proxies.  The TUNNEL profile [7] SHOULD
   be used for this purpose; see [7] for more detail concerning the
   options available to setup an application-layer tunnel using TUNNEL,
   and see Section 10.1 for a discussion of TUNNEL related security
   considerations.  TUNNEL MUST be offered as a tuning profile for the
   creation of application-layer tunnels.  The TUNNEL profile MUST offer
   the use of some form of SASL authentication (c.f., Section 4.1 of
   [8]).  The TLS profile SHOULD be used to provide the required
   combination of mutual-authentication, integrity, and confidentiality
   for the IDXP profile.  For further discussion of application-layer
   tunnel and security issues see Section 2.1 and Section 10.

   The IDXP profile supports several elements of interest:

   o  The "IDXP-Greeting" element identifies an analyzer or manager at
      one end of a BEEP channel to the analyzer or manager at the other
      end of the channel.

   o  The "Option" element is used to convey optional channel parameters
      between peers during the exchange of "IDXP-Greeting" elements.
      This element is OPTIONAL.

   o  The "IDMEF-Message" element carries the structured information to
      be exchanged between the peers.


3.2 IDXP Profile Identification and Initialization

   The IDXP profile is identified as

      http://iana.org/beep/transient/idwg/idxp

   in the BEEP "profile" element during channel creation.

   During channel creation, "IDXP-Greeting" elements MUST be mutually
   exchanged between the peers.  An "IDXP-Greeting" element MAY be
   contained within the corresponding "profile" element in the BEEP
   "start" element.  Including an "IDXP-Greeting" element in the initial
   "start" element has exactly the same semantics as passing it as the
   first "MSG" message on the channel.  If channel creation is
   successful, then before sending the corresponding reply, the BEEP



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   peer processes the "IDXP-Greeting" element and includes the resulting
   response in the reply.  This response will be an "ok" element or an
   "error" element.  The choice of which element is returned is
   dependent on local provisioning of the peer.

3.3 IDXP Profile Message Syntax

   BEEP messages in the profile MUST have a MIME Content-Type [5] of
   "text/xml", "text/plain", or "application/octet-stream".  The syntax
   of the individual elements is specified in Section 8.1 and Section 5
   of [4].

3.4 IDXP Profile Semantics

   Each BEEP peer issues the "IDXP-Greeting" element using "MSG"
   messages.  The "IDXP-Greeting" element MAY contain one or more
   "Option" sub-elements, conveying optional channel parameters.  Each
   BEEP peer then issues "ok" in "RPY" messages or "error" in "ERR"
   messages.  (See Section 2.3.1 of [8] for the definitions of the
   "error" and "ok" elements.) An "error" element MAY be issued within a
   "RPY" message when piggy-backed within a BEEP "profile" element.  See
   section 3.4.1 for an example of an "error" element being issued
   within a "RPY" message.  Based on the respective client/server roles
   negotiated during the exchange of "IDXP-Greeting" elements, the
   client sends data using "MSG" messages.  Depending on the MIME
   Content-Type, this data may be an "IDMEF-Message" element, plain
   text, or binary.  The server then issues "ok" in "RPY" messages or
   "error" in "ERR" messages.

3.4.1 The IDXP-GREETING Element

   The "IDXP-Greeting" element serves to identify the analyzer or
   manager at one end of the BEEP channel to the analyzer or manager at
   the other end of the channel.  The "IDXP-Greeting" element MUST
   include the role of the peer on the channel (client or server) and
   the Uniform Resource Identifier (URI) [1] of the peer.  Additionally,
   the "IDXP-Greeting" element MAY include the fully qualified domain
   name (c.f., [6]) of the peer.  One or more "Option" sub-elements MAY
   be present.

   An "IDXP-Greeting" element MAY be sent by either peer at any time.
   The peer receiving the "IDXP-Greeting" MUST respond with an "ok"
   (indicating acceptance), or an "error" (indicating rejection).  A
   peer's identity and role on a channel and any optional channel
   parameters are, in effect, specified by the most recent "IDXP-
   Greeting" it sent that was answered with an "ok".

   An "IDXP-Greeting" may be rejected (with an "error" element) under



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   many circumstances.  These include, but are not limited to,
   authentication failure, lack of authorization to connect under the
   specified role, the negotiation of an inadequate ciphersuite, or the
   presence of a channel option that must be understood but was
   unrecognized.

   For example, a successful creation with an embedded "IDXP-Greeting"
   might look like this:

   I: MSG 0 10 . 1592 187
   I: Content-Type: text/xml
   I:
   I: <start number='1'>
   I:   <profile uri='http://iana.org/beep/transient/idwg/idxp'>
   I:     <![CDATA[ <IDXP-Greeting uri='http://example.com/alice'
   I:       role='client' /> ]]>
   I:   </profile>
   I: </start>
   I: END
   L: RPY 0 10 . 1865 91
   L: Content-Type: text/xml
   L:
   L: <profile uri='http://iana.org/beep/transient/idwg/idxp'>
   L:   <![CDATA[ <ok /> ]]>
   L: </profile>
   L: END
   L: MSG 0 11 . 1956 61
   L: Content-Type: text/xml
   L:
   L: <IDXP-Greeting uri='http://example.com/bob' role='server' />
   L: END
   I: RPY 0 11 . 1779 7
   I: Content-Type: text/xml
   I:
   I: <ok />
   I: END















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   A creation with an embedded "IDXP-Greeting" that fails might look
   like this:

   I: MSG 0 10 . 1776 185
   I: Content-Type: text/xml
   I:
   I: <start number='1'>
   I:   <profile uri='http://iana.org/beep/transient/idwg/idxp'>
   I:     <![CDATA[ <IDXP-Greeting uri='http://example.com/eve'
   I:       role='client' /> ]]>
   I:   </profile>
   I: </start>
   I: END
   L: RPY 0 10 . 1592 182
   L: Content-Type: text/xml
   L:
   L: <profile uri='http://iana.org/beep/transient/idwg/idxp'>
   L:   <![CDATA[
   L:     <error code='530'>'http://example.com/eve' must first
   L:       negotiate the TLS profile</error> ]]>
   L: </profile>
   L: END


3.4.2 The OPTION Element

   If present, the "Option" element MUST be contained within an "IDXP-
   Greeting" element.  An individual "IDXP-Greeting" element MAY contain
   one or more "Option" sub-elements.  Each "Option" element within an
   "IDXP-Greeting" element represents a request to enable an IDXP option
   on the channel being negotiated.  See Section 4 for a complete
   description of IDXP options and the "Option" element.

3.4.3 The IDMEF-MESSAGE Element

   The "IDMEF-Message" element carries the information to be exchanged
   between the peers.  See Section 5 of [4] for the definition of this
   element.













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4. IDXP Options

   IDXP provides a service for the reliable exchange of data between
   intrusion detection entities.  Options are used to alter the
   semantics of the service.

   The specification of an IDXP option MUST define:

   o  the identity of the option;

   o  what content, if any, is contained within the option; and,

   o  the processing rules for the option.

   An option registration template (c.f.  Section 6) organizes this
   information.

   An "Option" element is contained within an "IDXP-Greeting" element.
   The "IDXP-Greeting" element itself MAY contain one or more "Option"
   elements.  The "Option" element has several attributes and contains
   arbitrary content:

   o  the "internal" and the "external" attributes, exactly one of which
      MUST be present, uniquely identify the option;

   o  the "mustUnderstand" attribute, whose presence is OPTIONAL and
      whose default value is "false", specifies whether the option, if
      unrecognized, MUST cause an error in processing to occur; and,

   o  the "localize" attribute, whose presence is OPTIONAL, specifies
      one or more language tokens, each identifying a desirable language
      tag to be used if textual diagnostics are returned to the
      originator.

   The value of the "internal" attribute is the IANA-registered name for
   the option.  If the "internal" attribute is not present, then the
   value of the "external" attribute is a URI or URI with a fragment-
   identifier.  Note that a relative-URI value is not allowed.

   The "mustUnderstand" attribute specifies whether the peer may ignore
   the option if it is unrecognized.  If the value of the
   "mustUnderstand" attribute is "true", and if the peer does not
   recognize the option, then an error in processing has occurred.  When
   absent, the value of the "mustUnderstand" attribute is defined to be
   "false".






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4.1 The channelPriority Option

   Section 7.3 contains the IDXP option registration for the
   "channelPriority" option.  This option contains a "channelPriority"
   element (c.f., Section 8.2).

   By default, IDXP does not place any requirements on how peers should
   manage multiple IDXP channels.  The "channelPriority" option provides
   a way for peers using multiple IDXP channels to request relative
   priorities for each channel.  When sending an "IDXP-Greeting" element
   during the provisioning of an IDXP channel, the originating peer MAY
   request that the remote peer assign a priority to the channel by
   including an "Option" element containing a "channelPriority" element.

   The "channelPriority" element has one attribute named "priority", of
   range 0..2147483647.  This attribute is REQUIRED.  Not
   coincidentally, this is the maximum range of possible BEEP channel
   numbers.  0 is defined to represent the highest priority, with
   relative priority decreasing as the "priority" value ascends.

   For example, during the exchange of "IDXP-Greeting" elements during
   channel provisioning, an analyzer successfully requests that a
   manager assign a priority to the channel:


       analyzer                                           manager
          --------------- greeting w/ option ----------------->
         <---------------------- <ok> ------------------------

   C: MSG 1 17 . 1984 165
   C: Content-Type: text/xml
   C:
   C: <IDXP-Greeting uri='http://example.com/alice' role='client'>
   C:   <Option internal='channelPriority'>
   C:     <channelPriority priority='0' />
   C:   </Option>
   C: </IDXP-Greeting>
   C: END
   S: RPY 1 17 . 2001 7
   S: Content-Type: text/xml
   S:
   S: <ok />
   S: END








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   For example, during the exchange of "IDXP-Greeting" elements during
   channel provisioning, a manager unsuccessfully requests that an
   analyzer assign a priority to the channel:


       analyzer                                           manager
         <---------------- greeting w/ option ----------------
          --------------------- <error> ---------------------->

   S: MSG 1 17 . 1312 194
   S: Content-Type: text/xml
   S:
   S: <IDXP-Greeting uri='http://example.com/bob' role='server'>
   S:   <Option internal='channelPriority' mustUnderstand='true'>
   S:     <channelPriority priority='2147483647' />
   S:   </Option>
   S: </IDXP-Greeting>
   S: END
   C: ERR 1 17 . 451 68
   C: Content-Type: text/xml
   C:
   C: <error code='504'>'channelPriority' option was unrecognized</error>
   C: END


4.2 The streamType Option

   Section 7.4 contains the IDXP option registration for the
   "streamType" option.  This option contains a "streamType" element
   (c.f., Section 8.3).

   By default, IDXP provides no explicit method for categorizing
   channels.  The "streamType" option provides a way for peers to
   request that a channel be categorized as a particular stream type.
   When sending an "IDXP-Greeting" element during the provisioning of an
   IDXP channel, the originating peer MAY request that the remote peer
   assign a stream type to the channel by including an "Option" element
   containing a "streamType" element.

   The "streamType" element has one attribute named "type", with the
   possible values of "alert", "heartbeat", or "config".  This attribute
   is REQUIRED.  A value of "alert" indicates that the channel should be
   categorized as being used for the exchange of ID alerts.  A value of
   "heartbeat" indicates that the channel should be categorized as being
   used for the exchange of heartbeat messages such as the "Heartbeat"
   element (c.f., Section 5 of [4]).  A value of "config" indicates that
   the channel should be categorized as being used for the exchange of
   configuration messages.



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   For example, during the exchange of "IDXP-Greeting" elements during
   channel provisioning, an analyzer successfully requests that a
   manager assign a stream type to the channel:


       analyzer                                           manager
          --------------- greeting w/ option ----------------->
         <---------------------- <ok> ------------------------

   C: MSG 1 21 . 1963 155
   C: Content-Type: text/xml
   C:
   C: <IDXP-Greeting uri='http://example.com/alice' role='client'>
   C:   <Option internal='streamType'>
   C:     <streamType type='alert' />
   C:   </Option>
   C: </IDXP-Greeting>
   C: END
   S: RPY 1 21 . 1117 7
   S: Content-Type: text/xml
   S:
   S: <ok />
   S: END




























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   For example, during the exchange of "IDXP-Greeting" elements during
   channel provisioning, a manager unsuccessfully requests that an
   analyzer assign a stream type to the channel:



       analyzer                                           manager
         <---------------- greeting w/ option ----------------
          --------------------- <error> ---------------------->

   S: MSG 1 21 . 1969 176
   S: Content-Type: text/xml
   S:
   S: <IDXP-Greeting uri='http://example.com/bob' role='server'>
   S:   <Option internal='streamType' mustUnderstand='true'>
   S:     <streamType type='config' />
   S:   </Option>
   S: </IDXP-Greeting>
   S: END
   C: ERR 1 21 . 1292 63
   C: Content-Type: text/xml
   C:
   C: <error code='504'>'streamType' option was unrecognized</error>
   C: END



























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5. Fulfillment of IDWG Communications Protocol Requirements

   The following lists the communications protocol requirements
   established in Section 5 of [9] and, for each requirement, describes
   the manner in which it is fulfilled by IDXP.

   The [protocol] MUST support reliable transmission of messages.

      IDXP operates over BEEP, which operates only over reliable
      connection-oriented transport protocols (e.g., TCP).  In addition,
      BEEP peers communicate using a simple request-response protocol,
      which provides end-to-end reliability between peers.

   The [protocol] MUST support transmission of messages between ID
   components across firewall boundaries without compromising security.

      The TUNNEL profile [7] MUST be offered as an option for creation
      of application-layer tunnels to allow operation across firewalls.
      The TUNNEL profile SHOULD be used to provide an application-layer
      tunnel.  The ability to authenticate hosts during the creation of
      an application-layer tunnel MUST be provided by the mechanism
      chosen to create such tunnels.  A firewall may therefore be
      configured to authenticate all hosts attempting to tunnel into the
      protected network.  If the TUNNEL profile is used, SASL (c.f.,
      Section 4.1 of [8]) MUST be offered as a mechanism by which hosts
      can be authenticated.

   The [protocol] MUST support mutual authentication of the analyzer and
   the manager to each other.

      IDXP supports mutual authentication of the peers through the use
      of an appropriate underlying BEEP security profile.  The TLS
      profile and members of the SASL family of profiles (c.f., Section
      4.1 of [8]) are examples of security profiles that may be used to
      authenticate the identity of communicating ID components.  TLS
      MUST be offered as a mechanism to provide mutual authentication,
      and TLS SHOULD be used to provide mutual authentication.

   The [protocol] MUST support confidentiality of the message content
   during message exchange.  The selected design MUST be capable of
   supporting a variety of encryption algorithms and MUST be adaptable
   to a wide variety of environments.

      IDXP supports confidentiality through the use of an appropriate
      underlying BEEP security profile.  The TLS profile is an example a
      security profile that offers confidentiality.  The TLS profile
      with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite MUST be
      offered as a mechanism to provide confidentiality, and TLS with



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      this cipher suite SHOULD be used to provide confidentiality.  The
      TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses ephemeral
      Diffie-Hellman (DHE) with DSS signatures for key exchange and
      triple DES (3DES) and cipher-block chaining (CBC) for encryption.
      Stronger cipher suites are optional.

   The [protocol] MUST ensure the integrity of the message content.  The
   selected design MUST be capable of supporting a variety of integrity
   mechanisms and MUST be adaptable to a wide variety of environments.

      IDXP supports message integrity through the use of an appropriate
      underlying BEEP security profile.  The TLS profile and members of
      the SASL family of profiles (c.f., Section 4.1 of [8]) are
      examples of security profiles that offer message integrity.  The
      TLS profile with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher
      suite MUST be offered as a mechanism to provide integrity, and TLS
      with this cipher suite SHOULD be used to provide integrity.  The
      TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses the Secure
      Hash Algorithm (SHA) for integrity protection using a keyed
      message authentication code.  Stronger cipher suites are optional.

   The [protocol] MUST support separate authentication keys for each
   sender.

      IDXP supports separate authentication keys for each sender (i.e.,
      per-source authentication) through the use of an appropriate
      underlying BEEP security profile.  The TLS profile is an example
      of a security profile that supports per-source authentication
      through the mutual authentication of public-key certificates.  TLS
      MUST be offered as a mechanism to provide per-source
      authentication, and TLS SHOULD be used to provide per-source
      authentication.

   The [protocol] SHOULD resist protocol denial of service attacks.

      IDXP supports resistance to denial of service (DoS) attacks
      through the use of an appropriate underlying BEEP security
      profile.  BEEP peers offering the IDXP profile MUST offer the use
      of TLS with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite,
      and SHOULD use TLS with that cipher suite.  To resist DoS attacks
      it is helpful to discard traffic arising from a non-authenticated
      source.  BEEP peers MUST support the use of authentication in
      conjunction with any mechanism used to create application-layer
      tunnels.  In particular, the use of some form of SASL
      authentication (c.f., Section 4.1 of [8]) MUST be offered to
      provide authentication in the use of the TUNNEL profile.  See
      Section 7 of [7] for a discussion of security considerations in
      the use of the TUNNEL profile.



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   The [protocol] SHOULD resist malicious duplication of messages.

      IDXP supports resistance to malicious duplication of messages
      (i.e., replay attacks) through the use of an appropriate
      underlying BEEP security profile.  The TLS profile is an example
      of a security profile offering resistance to replay attacks.  The
      TLS profile with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher
      suite MUST be offered as a mechanism to provide resistance against
      replay attacks, and TLS with this cipher suite SHOULD be used to
      provide resistance against replay attacks.  The
      TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses cipher-block
      chaining (CBC) to ensure that even if a message is duplicated the
      cipher-text duplicate will produce a very different plain-text
      result.  Stronger cipher suites are optional.





































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6. IDXP Option Registration Template

   When an IDXP option is registered, the following information is
   supplied:

   Option Identification: specify the NMTOKEN or the URI that
   authoritatively identifies this option.

   Contains: specify the XML content that is contained within the
   "Option" element.

   Processing Rules: specify the processing rules associated with the
   option.

   Contact Information: specify the postal and electronic contact
   information for the author(s) of the option.



































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7. Initial Registrations

7.1 Registration: The IDXP Profile

   Profile identification: http://iana.org/beep/transient/idwg/idxp

   Messages exchanged during channel creation: "IDXP-Greeting"

   Messages starting one-to-one exchanges: "IDXP-Greeting", "IDMEF-
   Message"

   Messages in positive replies: "ok"

   Messages in negative replies: "error"

   Messages in one-to-many exchanges: none

   Message syntax: c.f., Section 3.3

   Message semantics: c.f., Section 3.4

   Contact information: c.f., the "Authors' Addresses" section of this
   memo

7.2 Registration: The System (Well-Known) TCP port number for IDXP

   Protocol Number: TCP

   Message Formats, Types, Opcodes, and Sequences: c.f., Section 3.3

   Functions: c.f., Section 3.4

   Use of Broadcast/Multicast: none

   Proposed Name: Intrusion Detection Exchange Protocol

   Short name: idxp

   Contact Information: c.f., the "Authors' Addresses" section of this
   memo

7.3 Registration: The channelPriority Option

   Option Identification: channelPriority

   Contains: channelPriority (c.f., Section 8.2)

   Processing Rules: c.f., Section 4.1



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   Contact Information: c.f., the "Authors' Addresses" section of this
   memo

7.4 Registration: The streamType Option

   Option Identification: streamType

   Contains: streamType (c.f., Section 8.3)

   Processing Rules: c.f., Section 4.2

   Contact Information: c.f., the "Authors' Addresses" section of this
   memo






































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8. The DTDs

8.1 The IDXP DTD

   The following is the DTD defining the valid elements for the IDXP
   profile

     <!--
     DTD for the IDXP Profile, as of 2002-01-08

     Refer to this DTD as:

       <!ENTITY % IDXP PUBLIC "-//IETF//DTD RFC XXXX IDXP v1.0//EN">

       %IDXP;
     -->

     <!-- Includes -->

       <!ENTITY % BEEP PUBLIC "-//IETF//DTD BEEP//EN">

       %BEEP;


       <!ENTITY % IDMEF-Message PUBLIC "-//IETF//DTD RFC XXXX IDMEF v1.0//EN">

       %IDMEF;

     <!--
       Profile Summary

         BEEP profile http://iana.org/beep/transient/idwg/idxp

         role       MSG               RPY      ERR
         ====       ===               ===      ===
         I or L     IDXP-Greeting     ok       error
         C          IDMEF-Message     ok       error
     -->

     <!--
       Entity Definitions

             entity        syntax/reference     example
             ======        ================     =======
         an authoritative identification
             URI           c.f., [RFC-2396]       http://example.com

         a fully qualified domain name



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             FQDN          c.f., [RFC-1034]       www.example.com
     -->

     <!ENTITY % URI      "CDATA">
     <!ENTITY % FQDN     "CDATA">

     <!--
       The IDXP-Greeting element declares the role and identity of
       the peer issuing it, on a per channel basis. The
       IDXP-Greeting element may contain one or more Option
       sub-elements.
     -->

   <!ELEMENT IDXP-Greeting  (Option*)>
   <!ATTLIST IDXP-Greeting
             uri            %URI;                #REQUIRED
             role           (client|server)      #REQUIRED
             fqdn           %FQDN;               #IMPLIED>

     <!--
       The Option element conveys an IDXP channel option.
       Note that the %LOCS entity is imported from the BEEP Channel
       Management DTD.
     -->

   <!ELEMENT Option (ANY)>
   <!ATTLIST Option
             internal       NMTOKEN              ""
             external       %URI;                ""
             mustUnderstand (true|false)         "false"
             localize       %LOCS;               "i-default">

     <!--
       The IDMEF-Message element conveys the intrusion detection
       information that is exchanged.  This element is defined in the
       idmef-message.dtd
     -->

   <!-- End of DTD -->


8.2 The channelPriority Option DTD

   The following is the DTD defining the valid elements for the
   channelPriority option






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     <!--
     DTD for the channelPriority IDXP option, as of 2002-01-08

     Refer to this DTD as:

       <!ENTITY % IDXP-channelPriority PUBLIC
         "-//IETF//DTD RFC XXXX IDXP-channelPriority v1.0//EN">

       %IDXP-channelPriority;
     -->

     <!--
       Entity Definitions

             entity        syntax/reference     example
             ======        ================     =======
       a priority number
             PRIORITY      0..2147483647        1
     -->

   <!ENTITY % PRIORITY          "CDATA">

   <!ELEMENT channelPriority    EMPTY>
   <!ATTLIST channelPriority
             priority           %PRIORITY    #REQUIRED>

   <!-- End of DTD -->


8.3 The streamType DTD

   The following is the DTD defining the valid elements for the
   streamType option


















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     <!--
     DTD for the streamType IDXP option, as of 2002-01-08

     Refer to this DTD as:

       <!ENTITY % IDXP-streamType PUBLIC
         "-//IETF//DTD RFC XXXX IDXP-streamType v1.0//EN">

       %IDXP-streamType;
     -->

     <!--
       Entity Definitions

             entity        syntax/reference                example
             ======        ================                =======
        a stream type
             STYPE         (alert | heartbeat | config)    "alert"
     -->

   <!ENTITY % STYPE        (alert|heartbeat|config)>

   <!ELEMENT streamType    EMPTY>
   <!ATTLIST streamType
             type          %STYPE    #REQUIRED>

   <!-- End of DTD -->
























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9. Reply Codes

   This section lists the three-digit error codes the IDXP profile may
   generate.

   code    meaning
   ====    =======
   421     Service not available
           (E.g., the peer does not have sufficient resources.)

   450     Requested action not taken
           (E.g., DNS lookup failed or connection could not
            be established. See also 550.)

   454     Temporary authentication failure

   500     General syntax error
           (E.g., poorly-formed XML)

   501     Syntax error in parameters
           (E.g., non-valid XML)

   504     Parameter not implemented

   530     Authentication required

   534     Authentication mechanism insufficient
           (E.g., cipher suite too weak, sequence exhausted, etc.)

   535     Authentication failure

   537     Action not authorized for user

   550     Requested action not taken
           (E.g., peer could be contacted, but
            malformed greeting or no IDXP profile advertised.)

   553     Parameter invalid

   554     Transaction failed
           (E.g., policy violation)










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10. Security Considerations

   The IDXP profile is a profile of BEEP.  In BEEP, transport security,
   user authentication, and data exchange are orthogonal.  Refer to
   Section 8 of [8] for a discussion of this.  It is strongly
   recommended that those wanting to use the IDXP profile initially
   negotiate a BEEP security profile between the peers that offers the
   required security properties.  The TLS profile SHOULD be used to
   provide for transport security.  See Section 5 for a discussion of
   how IDXP fulfills the IDWG communications protocol requirements.

   See Section 2.4 for a discussion of the trust model.

10.1 Use of the TUNNEL Profile

   See Section 5 for IDXP's requirements on application-layer tunneling
   and the TUNNEL profile specifically.  See Section 7 of [7] for a
   discussion of the security considerations inherent in the use of the
   TUNNEL profile.

10.2 Use of Underlying Security Profiles

   At present, the TLS profile is the only BEEP security profile known
   to meet all of the requirements set forth in Section 5 of [9].  When
   securing a BEEP session with the TLS profile, the
   TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite offers an acceptable
   level of security.  See Section 5 for a discussion of how IDXP
   fulfills the IDWG communications requirements through the use of an
   underlying security profile.






















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References

   [1]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
        Identifiers (URI): Generic Syntax", RFC 2396, August 1998.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [3]  Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
        "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-xml,
        October 2000, <http://www.w3.org/TR/REC-xml>.

   [4]  Curry, D. and H. Debar, "Intrusion Detection Message Exchange
        Format Data Model and Extensible Markup Language (XML) Document
        Type Definition", RFC XXXX, Month YYYY.

   [5]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part Two: Media Types", RFC 2046, November
        1996.

   [6]  Mockapetris, P., "Domain names - concepts and facilities", STD
        13, RFC 1034, November 1987.

   [7]  New, D., "The TUNNEL Profile Registration", RFC XXXX, Month
        YYYY.

   [8]  Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC
        3080, March 2001.

   [9]  Wood, M. and M. Erlinger, "Intrusion Detection Message Exchange
        Requirements", RFC XXXX, Month YYYY.


Authors' Addresses

   Benjamin S. Feinstein
   Guardent, Inc.

   EMail: Ben.Feinstein@guardent.com
   URI:   http://www.guardent.com/


   Gregory A. Matthews
   CSC/NASA Ames Research Center

   EMail: gmatthew@nas.nasa.gov
   URI:   http://www.nas.nasa.gov/




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   John C. C. White
   MITRE Corporation

   EMail: jccw@mitre.org
   URI:   http://www.mitre.org/














































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Appendix A. IANA Considerations

   The IANA registers "IDXP" as a standards-track BEEP profile, as
   specified in Section 7.1.  The IANA changes the IDXP profile
   identification to "http://iana.org/beep/IDXP".

   The IANA registers "idxp" as a TCP port number, as specified in
   Section 7.2

   The IANA maintains a list of:

      IDXP options, c.f., Section 6.

   For this list, the IESG is responsible for assigning a designated
   expert to review the specification prior to the IANA making the
   assignment.  As a courtesy to developers of non-standards track IDXP
   options, the mailing list idxp-java-users@lists.sourceforge.net may
   be used to solicit commentary.

   The IANA makes the registrations specified in Section 7.3 and Section
   7.4.






























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Appendix B. History of Significant Changes

   The RFC Editor should remove this section and its corresponding TOC
   references prior to publication.

B.1 Significant Changes Since beep-idxp-05

   Modified the part of Section 5 regarding non-repudiation to instead
   refer to per-source authentication, per draft-ietf-idwg-requirements-
   09.

B.2 Significant Changes Since beep-idxp-04

   Added sentence to Section 3.4 explaining the situation in which an
   "error" element may be issued within an "RPY" message.

   Modified examples in Section 4.1 and 4.2, changing the message types
   from "RPY" to "ERR" for the negative response sent by the client.

   Fixed two locations where we were referencing the wrong section of
   the requirements document.

   Removed references to IP and the %IP attribute.

   Modified part of Section 5 dealing with non-repudiation of message
   origin.

   Modified Section 1.3 to further refine terminology.

   Replaced all remaining references to "entities" with references to
   "peers".

B.3 Significant Changes Since beep-idxp-03

   Modified references to Internet-Drafts to contain placeholders for
   their forthcoming RFC numbers.

   Modified IDMEF formal public identifier (FPI) in the IDXP DTD to
   reflect the changes in draft-ietf-idwg-idmef-xml-06.

   Modified IDXP FPI for the IDXP DTD to be more in line with the IDMEF
   FPI.

B.4 Significant Changes Since beep-idxp-02

   Added IDXP option registration template and registered two initial
   options.




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   Indicated that the IANA should change the profile identification to
   "http://iana.org/beep/IDXP" upon adoption of IDXP as a standards-
   track BEEP profile.

   Renamed the "Options" element to "Option" and allowed multiple
   "Option" sub-elements within an "IDXP-Greeting" element.  Also added
   attributes to "Option" element.

   Modified IANA profile registration and added TCP port number IANA
   registration.

   Reordered some sections to improve the flow of the document.

   Changed IDXP DTD identifier to be more IETF-like and removed URLs
   from ENTITY declarations.

   Changed IDXP profile URI to fall under the "http://iana.org/beep/
   transient" namespace.

   Modified Section 1.3 to reference the requirements language specified
   by [2].

   Eliminated the use of the "endpoint" terminology, in favor of "peer".

   Modified figures to make them more understandable.

   Modified Sections 2, 3, and 4 to use the requirements language
   specified by [2].

   Indicated that the RFC Editor should remove Appendix B and its
   corresponding TOC reference prior to publication.

   Fixed several typos.

B.5 Significant Changes Since beep-idxp-01

   Added new MUST and SHOULD language for use of TLS and TUNNEL
   profiles.

   Modified the "IDXP-Greeting" element to include an "Options" sub-
   element.

   Changed IDXP profile URI.

B.6 Significant Changes Since beep-idxp-00

   Added Section 5, describing how IDXP fulfills the communication
   protocol requirements of the IDWG.



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   Moved IDXP profile registration to Appendix A.

   Clarified the role that underlying BEEP security profiles must play.

   Clarified how IDMEF messages fit into IDXP.

   Clarified how the IDXP profile channels and BEEP sessions interact.

   Made terminology clarifications and changes for overall consistency.










































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Internet-Draft                  The IDXP                  September 2002


Appendix C. Acknowledgements

   The authors gratefully acknowledge the contributions of Darren New,
   Marshall T.  Rose, Roy Pollock, Tim Buchheim, Mike Erlinger, and Paul
   Osterwald.














































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Internet-Draft                  The IDXP                  September 2002


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