Internet Engineering Task Force                             F. Brockners
Internet-Draft                                               S. Bhandari
Intended status: Standards Track                                   Cisco
Expires: August 20, 2011 January 1, 2012                                        V. Singh

                                                              V. Fajardo
                                                  Telcordia Technologies
                                                       February 16,
                                                           June 30, 2011

   Diameter Network Address and Port Translation Control Application
                     draft-ietf-dime-nat-control-07
                     draft-ietf-dime-nat-control-08

Abstract

   This document describes the framework, messages, and procedures for
   the Diameter Network address and port translation Control
   Application.  This Diameter application allows per endpoint control
   of Network Address Translators and Network Address and Port
   Translators, which are added to networks to cope with IPv4-address
   space completion.  This Diameter application allows external devices
   to configure and manage a Network Address Translator device -
   expanding the existing Diameter-based AAA and policy control
   capabilities with a Network Address Translators and Network Address
   and Port Translators control component.  These external devices can
   be network elements in the data plane such as a Network Access
   Server, or can be more centralized control plane devices such as AAA-servers. AAA-
   servers.  This Diameter application establishes a context to commonly
   identify and manage endpoints on a gateway or server, and a Network
   Address Translator and Network Address and Port Translator device.
   This includes, for example, the control of the total number of
   Network Address Translator bindings allowed or the allocation of a
   specific Network Address Translator binding for a particular
   endpoint.  In addition, it allows Network Address Translator devices
   to provide information relevant to accounting purposes.

Status of this Memo

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   This Internet-Draft will expire on August 20, 2011. January 1, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Deployment Framework . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  Deployment Scenario  . . . . . . . . . . . . . . . . . . .  7
     3.2.  Diameter NAPT Control Application Overview . . . . . . . .  8
     3.3.  Deployment Scenarios For DNCA  . . . . . . . . . . . . . .  9
   4.  DNCA Session Establishment and Management  . . . . . . . . . . 11
     4.1.  Parties Involved . . .  Session Establishment  . . . . . . . . . . . . . . . . . . 11
     4.2.  Session Establishment  . Re-Authorization . . . . . . . . . . . . . . . . . 11 14
     4.3.  Session Re-Authorization . and Binding Query  . . . . . . . . . . . . . . . . 13 16
     4.4.  Session and Binding Query Termination  . . . . . . . . . . . . . . . . . . 15 . 18
     4.5.  Session Termination  . Abort  . . . . . . . . . . . . . . . . . . 17
     4.6.  DNCA Manager and Agent Failures . . . . 19
     4.6.  Failure cases of the DNCA Diameter peers . . . . . . . . . 18 20
   5.  Use Of The Diameter Base Protocol  . . . . . . . . . . . . . . 18 21
     5.1.  Securing Diameter Messages . . . . . . . . . . . . . . . . 19 21
     5.2.  Accounting Functionality . . . . . . . . . . . . . . . . . 19 22
     5.3.  Use Of Sessions  . . . . . . . . . . . . . . . . . . . . . 19 22
     5.4.  Routing Considerations . . . . . . . . . . . . . . . . . . 19 22
     5.5.  Advertising Application Support  . . . . . . . . . . . . . 19 22
   6.  DNCA Commands  . . . . . . . . . . . . . . . . . . . . . . . . 20 22
     6.1.  NAT-Control Request (NCR) Command  . . . . . . . . . . . . 20 22
     6.2.  NAT-Control Answer (NCA) Command . . . . . . . . . . . . . 21 23
   7.  NAT Control Application Session State Machine  . . . . . . . . 21 24
   8.  DNCA AVPs  . . . . . . . . . . . . . . . . . . . . . . . . . . 24 27
     8.1.  Reused Base Protocol AVPs  . . . . . . . . . . . . . . . . 24 27
     8.2.  Additional Result-Code AVP Values  . . . . . . . . . . . . 25 28
       8.2.1.  Success  . . . . . . . . . . . . . . . . . . . . . . . 25 28
       8.2.2.  Transient Failures . . . . . . . . . . . . . . . . . . 25 28
       8.2.3.  Permanent Failures . . . . . . . . . . . . . . . . . . 26 29
     8.3.  Reused NASREQ Diameter Application AVPs  . . . . . . . . . 27 30
     8.4.  Reused AVPs from RFC 4675  . . . . . . . . . . . . . . . . . . . 27 30
     8.5.  Reused AVPs from Diameter QoS Application  . . . . . . . . . . . 27 31
     8.6.  Reused AVPs from ETSI ES 283 034, e4 Diameter
           Application  . . . 28 . . . . . . . . . . . . . . . . . . . . 31
     8.7.  DNCA Defined AVPs  . . . . . . . . . . . . . . . . . . . . 29 32
       8.7.1.  NC-Request-Type AVP  . . . . . . . . . . . . . . . . . 29 32
       8.7.2.  NAT-Control-Install AVP  . . . . . . . . . . . . . . . 30 33
       8.7.3.  NAT-Control-Remove AVP . . . . . . . . . . . . . . . . 30 33
       8.7.4.  NAT-Control-Definition AVP . . . . . . . . . . . . . . 30 33
       8.7.5.  NAT-Internal-Address AVP . . . . . . . . . . . . . . . 31 34
       8.7.6.  NAT-External-Address AVP . . . . . . . . . . . . . . . 31 34
       8.7.7.  Max-NAT-Bindings . . . . . . . . . . . . . . . . . . . 32 35
       8.7.8.  NAT-Control-Binding-Rule AVP . . . . . . . . . . . . . 32 35
       8.7.9.  Duplicate-Session-Id AVP . . . . . . . . . . . . . . . 32 35
   9.  Accounting Commands  . . . . . . . . . . . . . . . . . . . . . 32 35
     9.1.  NAT Control Accounting Messages  . . . . . . . . . . . . . 33 36
     9.2.  NAT Control Accounting AVPs  . . . . . . . . . . . . . . . 33 36
       9.2.1.  NAT-Control-Record . . . . . . . . . . . . . . . . . . 33 36
       9.2.2.  NAT-Control-Binding-Status . . . . . . . . . . . . . . 33 36
       9.2.3.  Current-NAT-Bindings . . . . . . . . . . . . . . . . . 34 37
   10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . . 34 37
     10.1. DNCA AVP Table for NAT Control Initial and Update
           Requests . . . . . . . . . . . . . . . . . . . . . . . . . 34 37
     10.2. DNCA AVP Table for Session Query request . . . . . . . . . 35 38
     10.3. DNCA AVP Table for Accounting Message  . . . . . . . . . . 35 38
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 35 38
     11.1. Command Codes  . . . . Application Identifier . . . . . . . . . . . . . . . . . . 36 39
     11.2. AVP Command Codes  . . . . . . . . . . . . . . . . . . . . . . . . 36 39
     11.3. AVP Values Codes  . . . . . . . . . . . . . . . . . . . . . . . . 36
       11.3.1. 39
     11.4. Result-Code AVP Values . . . . . . . . . . . . . . . . 37
     11.4. Application IDs . . 39
     11.5. NC-Request-Type AVP  . . . . . . . . . . . . . . . . . . . 37 39
     11.6. NAT-Control-Binding-Status AVP . . . . . . . . . . . . . . 39
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 38 40
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38 41
   14. Change History (to be removed prior to publication as an
       RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 41
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 40
     15.2. Informative References . . . . . . . . . . . . . . . . . . 40 43
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40 43

1.  Introduction

   Internet service providers have started to deploy Network Address
   Translators (NATs) and Network Address and Port Translators (NAPTs)
   at the edge of
   in their networks to deal with the depletion of available public IPv4
   addresses.  This document defines a Diameter application
   for allowing
   providers deploying such to control the behavior of these NAT and NAPT devices.  The
   use of a Diameter application allows for simple integration into the
   existing Authentication, Authorization and Accounting (AAA)
   environment of a provider.

   The Diameter Network address and port translation Control Application
   (DNCA) offers the following capabilities:

   1.  Limits or defines the number of NAPT/NAT bindings made available
       to an individual subscriber or end point.

   2.  Supports the allocation of specific NAPT/NAT bindings.  Two types
       of specific bindings can be distinguished:

       *  Allocation of a pre-defined NAT binding: Both the internal and
          external IP address and port pair are specified within the
          request.  In some  Some deployment cases, such as access to a web-
          server within a user's home network with IP address and port,
          benefit from statically configured bindings.

       *  Allocation of an external IP address for a given internal IP
          address: The allocated external IP address is reported back to
          the requestor.  In some deployment scenarios, the application
          requires immediate knowledge of the allocated binding for a
          given internal IP address but does not control the allocation
          of the external IP address; for example, SIP-proxy server
          deployments.

   3.  Defines the external address pool(s) to be used for allocating an
       external IP address: External address pools can either be pre-
       assigned at the NAPT/NAT, NAPT/NAT device, or specified within a request.
       If pre-
       assigned pre-assigned address pools are used, a request needs to
       include a reference to identify the pool.  Otherwise, the request
       contains a description of the IP address pool(s) to be used; for
       example, a list of IP-subnets.  Such External external address pools can
       be used to select the external IP address in NAPT/NAT bindings
       for multiple subscribers.

   4.  Generates reports and accounting records: Reports established
       bindings for a particular user.  The collected information is
       used by accounting systems for statistical purposes.

   5.  Queries and retrieves details about bindings on demand: This
       feature complements the previously mentioned accounting
       functionality(see
       functionality (see item 4).

   6.  Identifies a subscriber or endpoint on multiple network devices
       (NAPT or NAT
       (NAT/NAPT device, the AAA-server, or the Network Access Server
       (NAS)): Endpoint identification is facilitated through a Global
       Endpoint ID.  Endpoints are identified through a single or a set
       of classifiers, such as IP address, Virtual Local Area Network
       (VLAN) identifier, or interface identifier which uniquely
       identify the traffic associated with a particular global endpoint
       endpoint.

   This document is structured as follows: Section 2 lists terminology,
   while Section 3 provides an introduction to DNCA and its overall
   deployment framework.  Sections 4 to 8 cover DNCA specifics, with
   Section 4 describing session management, Section 5 the use of the
   Diameter base protocol, Section 6 new commands, Section 7 AVPs used,
   and Section 8 accounting aspects.  Section 9 presents an AVP
   occurance
   occurence table.  IANA and security considerations are addressed in
   Sections 10 and 11.

2.  Conventions

   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 [RFC2119].

   Abbreviations used in this document:

      AAA: Authentication, Authorization, Accounting

      DNCA: Diameter Network address and port translation Control
      Application

      NAPT: Network Address and Port Translation

      NAT: Network Address Translation (NAT and NAPT are used in this
      document interchangeably)

      NAT Binding

      NAT-binding or Binding: binding: Association of two IP address/port pairs
      (with one IP address typically being private and the other one
      public) to facilitate NAT

      NAT-device: Network Address Translator or Network Address and Port
      Translator: An entity performing NAT or NAPT
      NAT-controller: Entity controlling the behavior of a NAT-device

      NAS: Network Access Server

      NCR:NAT

      NCR: NAT Control Request
      NCA:NAT

      NCA: NAT Control Answer

3.  Deployment Framework

3.1.  Deployment Scenario

   Figure 1 shows a typical network deployment for Internet access.  A
   user's IPv4 host gains access to the Internet though a NAS, which
   facilitates the authentication of the endpoint and configures the
   user's connection according to the authorization and configuration
   data received from the AAA-server upon successful authentication.
   Public IPv4 addresses are used throughout the network.

                         +---------+
                         |         |
                         |   AAA   |
                         |         |
                         +---------+
                              |
                              |
                              |
                              |
    +---------+          +---------+             +----------+
    |  IPv4   |          |         |             |  IPv4    |
    |  Host   |----------|   NAS   |-------------| Internet |
    |         |          |         |             |          |
    +---------+          +---------+             +----------+

    <-------------------- Public IPv4 ---------------------->

         Figure 1: Typical network deployment for internet access

   Figure 2 depicts the deployment scenario when a service provider
   introduces a NAT device NAT-device to increase the efficiency of the global IPv4
   address pool utilization.  The objective is to provide the customer
   with connectivity to the public IPv4 Internet.  The NAT device NAT-device
   performs network address and port (and optionally address family)
   translation, depending on whether the access network uses private
   IPv4 addresses or public IPv6 addresses, to public IPv4 addresses.
   If the NAT device NAT-device would be put in place without any endpoint
   awareness, the service offerings of the service provider could be
   hampered.
   impacted.  This includes cases like:

   o  Provisioning static NAT bindings for particular endpoints,
   using endpoints

   o  Using different public IP address pools for different set of
   endpoints; for
      endpoints (for example, residential or business customers, and
   reporting customers)

   o  Reporting allocated bindings on a per endpoint basis is burdensome
   for a service provider if the NAT device is not aware of endpoints
   and allows per endpoint

   o  Integrate control and management, which easily
   integrates with of the NAT-device into the already existing per
      endpoint management infrastructure of the service provider. provider

                   +---------+
                   |         |
                   |   AAA   |
                   |         |
                   +---------+
                        |
                        |
                        |
                        |
     +--------+    +---------+    +---------+    +--------+    +----------+
     |  IPv4/ |    |         |    |        |    |  IPv4    |
     |  IPv6  |----|   NAS   |----|   NAT  NAT-  |----| Internet |
     |  Host  |    |         |    | device |    |          |
     +--------+    +---------+    +---------+    +--------+    +----------+
     <-------- Private IPv4 -----------><--- ----------><--- Public IPv4 --->
     <-------- Public  IPv6 -----------><--- ----------><--- Public IPv4 --->

               Figure 2: Access network deployment with NAT

3.2.  Diameter NAPT Control Application Overview

   DNCA runs between a two DNCA Agent on Diameter peers.  One DNCA Diameter peer
   resides within the NAT and NAT-device, the other DNCA Manager. Diameter peer resides
   within the NAT-Controller.  DNCA allows per endpoint control and
   management of NAT. NAT within the NAT-device.  Based on Diameter, DNCA
   integrates well with the suite of Diameter applications deployed for
   per endpoint authentication, authorization, accounting, and policy
   control in service provider networks.

   DNCA offers:

   o  Request and answer commands to control the allowed number of NAT
      bindings per endpoint , to request the allocation of specific
      bindings for an endpoint, to define the address pool to be used
      for an endpoint.

   o  Provides per endpoint reporting of the allocated NAT bindings.

   o  Provides unique identification of an endpoint on NAT device, NAT-device, AAA-
      server and NAS, to simplify correlation of accounting data
      streams.

   DNCA allows controlling the behavior of a NAT device NAT-device on a per
   endpoint basis during initial session establishment and at later
   stages by providing an update procedure for already established
   sessions.  Using DNCA, per endpoint NAT binding information can be
   retrieved either using accounting mechanisms or through an explicit
   session query to the NAT.

3.3.  Deployment Scenarios For DNCA

   The role of

   DNCA can be fulfilled by either the NAS or by an external
   server, such as AAA-server.  The two deployed in different ways.  Two common deployment
   scenarios are outlined in Figure 3 ("integrated deployment") and
   Figure 4 ("autonomous deployment").  The two scenarios differ in
   which entity fulfills the role of the NAT-controller.  Within the
   figures (M) (C) denotes the network element, which takes on
   DNCA Manager role.  Similarly, (A) identifies element performing the network element,
   which performs DNCA Agent role. role of the
   NAT-controller.

   The integrated deployment approach hides the existence of the NAT NAT-
   device from external servers, such as the AAA-server as much as
   possible. AAA-server.  It is suited
   for environments where minimal changes to the existing AAA deployment
   are desired.  As DNCA Manager  The NAS and the NAT-device are Diameter peers
   supporting the DNCA.  The Diameter peer within the NAS, performing
   the role of the NAT-controller, initiates and manages session sessions with
   the NAT device, NAT-device, exchanges NAT specific configuration information and
   handles reporting and accounting information.  The NAS receives
   reporting and accounting information from NAT device. NAT-device.  With this
   information, the NAS provides can provide a single accounting record for the user.  This reduces the usage of
   an external accounting
   endpoint.  A system for correlating the accounting information received
   from multiple sources. NAS and NAT-device would not be needed.

   An example network attachment for an integrated NAT deployment can be
   described as follows: An endpoint connects to the network, with the
   NAS being the point of attachment.  After successful authentication,
   the NAS receives endpoint related authorization data from the AAA-server. AAA-
   server.  A portion of the authorization data applies to per endpoint
   configuration on the NAS itself, another portion describes
   authorization and configuration information for NAT control aimed at
   the NAT device. NAT-device.  The NAS will initiate initiates a DNCA session to the NAT NAT-device
   and send
   the sends relevant authorization and configuration information for
   the particular endpoint to the NAT device. NAT-device.  This can comprise NAT NAT-
   bindings, which have to be pre-established for the endpoint, or
   management related configuration, such as the maximum number of NAT NAT-
   bindings allowed for the endpoint or accounting requirements. endpoint.  The
   NAT device NAT-device sends its per
   endpoint accounting information to the NAS, which aggregates the
   accounting information received form from the NAT
   device NAT-device with its local
   accounting information for the endpoint into a single accounting
   stream towards the AAA-server.

                   +---------+
                   |         |
                   |   AAA   |
                   |         |
                   +---------+
                        |
                        |
                        |
     +--------+    +---------+    +---------+    +--------+    +----------+
     |  IPv4/ |    |   (M)   (C)   |    |   (A)        |    |  IPv4    |
     |  IPv6  |----|   NAS   |----|   NAT  NAT-  |----| Internet |
     |  Host  |    |         |    | device |    |          |
     +--------+    +---------+    +---------+    +--------+    +----------+
     <-------- Public  IPv6 ----------><--- Public IPv4 ----> --->
     <-------- Private IPv4 ----------><--- Public IPv4 ----> --->

          Figure 3: NAT Control control deployment: Integrated deployment

   The autonomous deployment approach decouples user management on NAS
   and NAT device.  The AAA NAT-device.  In the autonomous deployment approach, the AAA-
   system performing and the role of DNCA Manager NAT-device are the Diameter peers running the DNCA.
   The AAA-system also serves as NAT-controller.  It manages the
   connection to the NAT device, NAT-device, controls the per endpoint
   configuration, and also receives accounting and reporting information
   from the NAT device. NAT-device.  Different from the integrated deployment
   scenario, the autonomous deployment scenario does not "hide" the
   existence of the NAT device NAT-device from the AAA infrastructure.  Here two
   accounting streams are received by the AAA-server for one particular
   endpoint, one from the NAS, and one from the NAT device. NAT-device.

                     +---------+
                     |   (M)   (C)   |
                     |   AAA   |---------
                     |         |         |
                     +---------+         |
                          |              |
                          |              |
                          |              |
       +--------+    +---------+    +---------+    +----------+
       |  IPv4/ |    |         |    |   (A)         |    |  IPv4    |
       |  IPv6  |----|   NAS   |----|   NAT  NAT-   |----| Internet |
       |  Host  |    |         |    | device  |    |          |
       +--------+    +---------+    +---------+    +----------+
       <-------- Public  IPv6 ----------><---- Public IPv4 --->
       <-------- Private IPv4 ----------><---- Public IPv4 --->

          Figure 4: NAT Control control deployment: Autonomous deployment

4.  DNCA Session Establishment and Management

   Note that this section forward references some of the commands and
   AVPs defined for DNCA.  Please refer to Section 6 and Section 8 for
   details.

4.1.  Parties Involved

   Authorization  DNCA runs between a Diameter peer residing in a NAT-
   controller and control models supported by this application
   include a Diameter peer residing in a NAT-device.  The
   Diameter peer within the following parties:

   o  DNCA Agent: DNCA Agent NAT-controller is part of always the NAT device

   o  DNCA Manager

   The NAT control
   requesting entity is always DNCA Manager.  DNCA
   Manager always entity: It initiates, updates, or terminates the sessions.  This
   mode of operation is sometimes also referred to as "push mode".

   DNCA Manager can be NAS or AAA-server.  DNCA Manager initiates a
   session with DNCA Agent
   Sessions are initiated when it learns about the subscriber.  DNCA
   Manager may learn NAT-controller learns about a subscriber when it receives new
   endpoint (i.e., host) that requires a NAT service.  This could for
   example be due to the entity hosting the NAT-controller receiving
   authentication, authorization, or accounting request requests for that subscriber or by some
   other means, such as on from the box configuration to identify
   endpoint.  Alternate methods that could trigger session set up
   include local configuration, receipt of a
   subscriber with respect to his IP packets.

4.2. packet from a formerly
   unknown IP-address, etc.

4.1.  Session Establishment

   The DNCA Manager Diameter peer within the NAT-controller establishes a
   session with the DNCA Agent Diameter peer within the NAT-device to control
   the behavior of the NAT device. function within the NAT-device.  During
   session establishment, the DNCA
   Manager Diameter peer within the NAT-
   controller passes along configuration information to DNCA Agent. Diameter
   peer within the NAT-device.  The session configuration information
   comprises the maximum number of bindings allowed for the endpoint
   associated with this session, a set of pre-defined NAT bindings to be
   established for this endpoint, or a description of the address pool,
   that external addresses are to be allocated from.

   The DNCA Manager initiates the Diameter NAT Control session to DNCA
   Agent.  DNCA Manager peer within the NAT-controller generates a NAT-Control NAT-
   Control Request (NCR) message to the DNCA Agent Diameter peer within the
   NAT-device with NC-Request-Type AVP set to INITIAL_REQUEST. INITIAL_REQUEST to
   initiate a Diameter NAT control session.  On receipt of a NCR the
   DNCA Agent Diameter peer within the NAT-device sets up a new session for
   the endpoint associated with the endpoint classifier(s) contained in
   the NCR.  The DNCA Agent Diameter peer within the NAT-device notifies its
   DNCA Manager Diameter peer within the NAT-controller about successful session
   setup using a NAT-Control Answer (NCA) message with Result-Code set
   to DIAMETER_SUCCESS.  Figure 5 shows the initial protocol interaction
   between the two DNCA Manager and DNCA Agent. Diameter peers.

   The initial NAT-Control-Request may contain configuration information
   for the session, which specifies the behavior of the NAT device NAT-device for
   the session.  The configuration information, information which may be included,
   comprises:

   o  A list of NAT bindings, which should be pre-allocated for the
      session; for example, in case a subscriber user requires a fixed external IP-
      address/port pair for one of the his applications.

   o  The maximum number of NAT bindings NAT-bindings allowed for an endpoint.

   o  A description of the external address IP-address pool(s) to be used for
      the session.

   o  A reference to a predefined binding rule on DNCA Agent, the NAT-device, which
      is applied to the session.  Such a predefined binding rule on DNCA
      Agent the
      NAT-device may contain, for example, the name of the IP address IP-address
      pool that external IP addresses IP-addresses should be allocated from, the
      maximum number of bindings permitted for the endpoint endpoint, etc.

   In certain cases, DNCA Agent the NAT-device may not be able to perform the tasks
   requested within the NCR.  These include the following:

   o  If a DNCA Agent Diameter peer within the NAT-device receives a NCR from
      a DNCA Manager Diameter peer within a NAT-controller with NC- Request-Type
      AVP set to INITIAL_REQUEST that identifies an already existing
      session; that is, DNCA Manager Diameter peer and endpoint identifier match
      an already existing session, the DNCA Agent Diameter peer within the
      NAT-device returns NCA with Result-Code set to SESSION_EXISTS, and
      provides the Session-Id of the existing session in Duplicate-Session-Id the Duplicate-
      Session-Id AVP.

   o  If a DNCA Agent Diameter peer within the NAT-device receives an a NCR from
      a DNCA Manager Diameter peer within a NAT-controller with NC- Request-Type
      AVP set to INITIAL_REQUEST that matches more than one of the
      already existing sessions; that is, DNCA Manager Diameter peer and
      endpoint identifier match already existing sessions, the DNCA Agent
      Diameter peer within the NAT-device returns a NCA with Result-Code
      set to INSUFFICIENT-CLASSIFIERS.  In case a DNCA Manager Diameter peer
      receives a NCA that reports Insufficient-
      Classifiers, Insufficient-Classifiers, it may
      choose to retry establishing a new session using additional and or
      more specific classifiers.

   o  If the NCR contains a binding rule not defined on the NAT device, NAT-device,
      the DNCA Agent Diameter peer within the NAT-device returns NCA with
      Result-Code AVP set to UNKNOWN_BINDING_RULE.

   o  In case DNCA Agent the NAT-device is unable to establish all of the bindings
      requested in the NCR, it the DNCA Diameter peer will return a NCA
      with Result-Code set to BINDING_FAILURE.  A DNCA Agent, that is NAT device, Diameter peer
      within a NAT-device treats a NCR as an atomic operation; hence
      none of the requested bindings will be established by the NAT NAT-
      device.  Either all requested actions within a NCR are completed
      successfully, or the entire request fails.

   o  If DNCA Agent a NAT-device does not have sufficient resources to process a
      request, it the DNCA Diameter peer returns a NCA with Result-Code set
      to RESOURCE_FAILURE.

   o  In case Max-NAT-Binding and NAT-Control-Definition are included in
      the NCR along with a reference to a binding rule; that is, a
      predefined template on NAT device, NAT-device, and the values in Max-NAT-
      Binding and NAT-Control-Definition contradict those specified in
      the pre-defined binding rule, Max-NAT-Binding and NAT-Control-
      Definition override the values specified in the binding rule.

            DNCA Manager                             DNCA Agent

   NAT-controller (DNCA Diameter peer)   NAT-device (DNCA Diameter peer)
               |                                           |
               |                                           |
               |                                           |
            Trigger                                        |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               | (INITIAL_REQUEST, endpoint classifier,    |
               |     session id, NAT control config data)  |
               |                                           |
               |                                           |
               |                                           |
               |                                           |
               |                                 If Able to comply
               |                                 with Request then
               |                                 Create session state
               |                                           |
               |                                           |
               |                     NCA                   |
               |<------------------------------------------|
               |                 (result code)             |
               |                                           |
               |                                           |

      Figure 5: Initial NAT Control control request and session establishment

4.3.

   Note: The DNCA Diameter peer within the NAT-device creates session
   state only if it is able to comply with the NCR.  On success it will
   reply with a NCA with Result-Code set to DIAMETER_SUCCESS.

4.2.  Session Re-Authorization

   Session re-authorization is performed if DNCA Manager the NAT-controller desires
   to change the behavior of the NAT NAT-device for an existing session.  Re-
   authorization
   Session re-authorization could be used, for example, to change the
   number of allowed bindings for a particular session, or establish or
   remove a pre-defined binding.

   The DNCA Manager Diameter peer within the NAT-controller generates a NCR
   message to DNCA Agent Diameter peer within NAT-device with NC-Request-
   Type NC-Request-Type
   AVP set to UPDATE_REQUEST upon receiving a trigger signal.  In
   case  If the
   session is updated successfully, the DNCA Agent Diameter peer within the
   NAT-device notifies the DNCA
   Manager Diameter peer within the NAT-controller
   about the successful session update using a NAT-Control Answer (NCA)
   message with Result-Code set to DIAMETER_SUCCESS.  Figure 6 shows the
   protocol interaction between the two DNCA Manager and DNCA Agent. Diameter peers.

   In certain cases, DNCA Agent the NAT-device may not be able to perform the tasks
   requested within the NCR.  These include the following:

   o  If DNCA Agent Diameter peer within a NAT-device receives a NCR update or
      query request for a non-
      existent non-existent session, it sets Result-Code in
      the answer to DIAMETER_UNKNOWN_SESSION_ID.

   o  If the NCR contains a binding rule not defined on the NAT device,
      DNCA Agent returns NAT-device,
      a NCA with Result-Code AVP set to
      UNKNOWN_BINDING_RULE. UNKNOWN_BINDING_RULE is
      returned.

   o  If DNCA Agent the NAT-device cannot establish the requested binding because
      the maximum number of allowed bindings has been reached for the
      Endpoint Classifier, it returns
      endpoint classifier, a NCA with Result-Code AVP set to
      MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT.
      MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT by the DNCA Diameter peer.

   o  If DNCA Agent the NAT-device cannot establish some or all of the bindings
      requested in a NCR, but has not yet reached the maximum number of
      allowed bindings for the subscriber, it returns endpoint, a NCA with Result-
      Code Result-Code set to BINDING_FAILURE.
      BINDING_FAILURE is returned.  As already noted, the DNCA Agent (i.e., NAT device) Diameter
      peer in a NAT-device treats a NCR as an atomic operation.  Hence
      none of the requested bindings will be established by NAT device.  Either all the NAT-
      device in case of failure.  Actions requested
      actions within a NCR are
      either all successful or failed completely. all fail.

   o  If DNCA Agent the NAT-device does not have sufficient resources to process a
      request, it returns a NCA with Result-Code set to RESOURCE_FAILURE. RESOURCE_FAILURE is
      returned.

   o  If a NCR redefines the maximum number of NAT bindings NAT-bindings allowed for
      the endpoint, the new value will override any previously defined
      limit on NAT bindings.  It depends on the implementation of the
      NAT device
      NAT-device on how the NAT device NAT-device copes with a case where the new
      value is lower than the actual number of allocated bindings.
      Typically the NAT device NAT-device refrains from enforcing the new limit
      immediately; that is, actively remove bindings, but rather
      disallow the establishment of new bindings until the current
      number of bindings is lower than the newly established maximum
      number of allowed bindings.

   o  If a NCR specifies a new binding rule, predefined on DNCA Agent, the NAT-
      device, the binding rule overrides any previously defined rules rule for
      the session.

   o  If Max-NAT-Binding and NAT-Control-Definition AVPs are included in
      the NCR along with a reference to a binding rule (a predefined
      template on NAT device) the NAT-device) and the values in Max-NAT-Binding and NAT-
      Control-Definition
      NAT-Control-Definition AVPs contradict those specified in the pre-
      defined binding rule, Max-NAT-Binding and NAT-Control-Definition
      AVPs override the values specified in the binding rule.

   Note: Already established bindings for the session will not be
   affected.
            DNCA Manager                             DNCA Agent
   affected in case the tasks requested within the NCR cannot be
   completed.

   NAT-controller (DNCA Diameter peer)   NAT-device (DNCA Diameter peer)
               |                                           |
               |                                           |
               |                                           |
        Change of session                                  |
           attributes                                      |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               |       (UPDATE_REQUEST session id,         |
               |         NAT control config data)          |
               |                                           |
               |                                           |
               |                                   If able to comply
               |                                   with the request:
               |                                  Update session state
               |                                           |
               |                                           |
               |                     NCA                   |
               |<------------------------------------------|
               |                 (result code)             |
               |                                           |
               |                                           |

             Figure 6: NAT Control control request for session update

4.4.

4.3.  Session and Binding Query

   Session query can be used by the DNCA Manager Diameter peer within the NAT-
   controller to either retrieve information on the current bindings for
   a particular session at the
   NAT device NAT-device or discover the session
   identifier for a particular external IP address/port pair.

   A DNCA Manager initiates Diameter peer within the NAT-controller starts a session query
   by sending a NCR message to
   DNCA Agent with NC-Request-Type AVP set to
   QUERY_REQUEST.  Figure 7 shows the protocol interaction between the
   DNCA Manager and DNCA Agent. Diameter peers.

   Two types of query requests exist.  The first type of query request
   uses the session ID as input parameter to the query.  It is to allow
   the DNCA Manager Diameter peer within the NAT-controller to retrieve the
   current set of bindings for a specific session.  The second type of
   query request is used to retrieve the session identifiers, along with
   the associated bindings, matching a criteria.  This enables the DNCA Manager
   Diameter peer within the NAT-controller to find the those sessions, which
   utilize a specific external IP address. IP-address.

   1.  Request a list of currently allocated NAT bindings for a
       particular session: DNCA Agent on On receiving a NCR, the NAT-device looks up
       the session information for the session ID contained in the NCR,
       and reports all currently active NAT bindings NAT-bindings for the session
       using a NCA message with Result-Code set to DIAMETER_SUCCESS.  In
       this case the NCR MUST NOT contain a NAT-Control-Definition AVP.
       Each NAT
       binding NAT-binding is reported in a NAT-Control-Definition AVP.  In
       case the session ID is unknown, the DNCA Agent Diameter peer within the
       NAT-device returns NCA with Result-Code set to
       DIAMETER_UNKNOWN_SESSION_ID.

   2.  Retrieve session IDs and internal IP address/port pairs for one
       or multiple external IP address/port IP-address/port pairs: If the DNCA Manager Diameter
       peer within the NAT-controller wishes to retrieve the session
       ID(s) for one or multiple external
       IP address/port IP-address/port pairs, it MUST
       include the external IP address/
       port IP-address/port pair(s) as part of the NAT-Control-Definition NAT-
       Control-Definition AVP of the NCR.  The session ID is not
       included in the NCR or the NCA for this type of a query.  The
       DNCA Agent Diameter peer within the NAT-device reports the NAT bindings NAT-bindings
       and associated session IDs corresponding to the external IP address/
       port IP-
       address/port pairs in a NCA message with Result-Code set to
       DIAMETER_SUCCESS with the same session ID, which is was used in NCR.
       In case an external IP address/port IP-address/port pair has no associated
       existing NAT binding, NAT-binding, the NAT-Control-Definition AVP contained in
       the reply just contains the NAT-External-Address AVP.

            DNCA Manager                             DNCA Agent

   NAT-controller (DNCA Diameter peer)   NAT-device (DNCA Diameter peer)
               |                                           |
               |                                           |
               |                                           |
     DNCA Session Established                              |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               |              (QUERY_REQUEST)              |
               |                                           |
               |                                           |
               |                                           |
               |                          Look up corresponding session
               |                            and associated NAT Bindings NAT-bindings
               |                                           |
               |                   NCA                     |
               |<------------------------------------------|
               |              (Result-Code)                |
               |                                           |
               |                                           |

                          Figure 7: Session Query

4.5. query

4.4.  Session Termination

   Similar to session initiation, session tear down is always initiated
   by the DNCA Manager generates Diameter peer within the NAT-controller.  The DNCA
   Diameter peer sends a Session Terminate Request (STR) message to
   DNCA Agent its
   peer within the NAT-device upon receiving a trigger signal.  The
   source of the trigger signal is outside the scope of this document.
   In response, the DNCA Agent Diameter peer within the NAT-device sends an
   accounting stop record reporting all the bindings and notifies its DNCA Manager
   Diameter peer about successful session termination using a Session
   Terminate Answer (STA) message with Result-Code set to
   DIAMETER_SUCCESS.  Figure 8 shows the protocol interaction between
   the two DNCA Manager and DNCA Agent. Diameter peers.

   If a DNCA Agent Diameter peer within a NAT-device receives STR from a DNCA Manager STR and fails
   to find a matching session, the DNCA Agent Diameter peer returns a STA with
   Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.

            DNCA Manager                             DNCA Agent
               |                                            |

   NAT-controller (DNCA Diameter peer)   NAT-device (DNCA Diameter peer)
               |                                            |
               |                                            |
            Trigger                                         |
               |                                            |
               |                   STR                      |
               |------------------------------------------->|
               |               (session id)                 |
               |                                            |
               |                                            |
               |                                  Remove NAT bindings NAT-bindings
               |                                       of session
               |                                            |
               |                                            |
               |           Send accounting stop             |
               |<-------------------------------------------|
               |           for       reporting all session bindings       |
               |                                            |
               |                                  Terminate Session session /
               |                                 Remove session state
               |                                            |
               |                                            |
               |                                            |
               |                  STA                       |
               |<-------------------------------------------|
               |             (Result-Code)                  |
               |                                            |

                  Figure 8: Terminate NAT Control control session

4.5.  Session Abort

   An Abort-Session-Request (ASR) message is sent from the DNCA Diameter
   peer within the NAT-device to the DNCA Diameter peer within the NAT-
   controller when it is unable to maintain a session due to resource
   limitations.  The DNCA Diameter peer within the NAT-controller
   acknowledges successful session abort using a Abort Session Answer
   (ASA) message with Result-Code set to DIAMETER_SUCCESS.  Figure 9
   shows the protocol interaction between the DNCA Diameter peers.  The
   DNCA Diameter peers will start a session termination procedure as
   described in Section 4.4 following an ASA with Result-Code set to
   DIAMETER_SUCCESS.

   If the DNCA Diameter peer within a NAT-controller receives an ASR but
   fails to find a matching session, it returns an ASA with Result-Code
   set to DIAMETER_UNKNOWN_SESSION_ID.  If the DNCA Diameter peer within
   the NAT-controller is unable to comply with the ASR for any other
   reason, an ASA with Result-Code set to DIAMETER_UNABLE_TO_COMPLY is
   returned.

   NAT-controller (DNCA Diameter peer)   NAT-device (DNCA Diameter peer)
               |                                            |
               |                                            |
               |                                         Trigger
               |                                            |
               |                   ASR                      |
               |<-------------------------------------------|
               |               (session id)                 |
               |                                            |
               |                                            |
               |                  ASA                       |
               |------------------------------------------->|
               |             (Result-Code)                  |
               |                                            |
               |                                            |
               |           On successful ASA                |
               |<------Session Termination Procedure------->|

                    Figure 9: Abort NAT control session

4.6.  Failure cases of the DNCA Manager and Agent Failures Diameter peers

   This document does not cover details specify the behavior in case DNCA Manager NAT-device and
   NAT-controller, or their respective DNCA
   Agent Diameter peers are out of
   sync.  This happens when DNCA Manager or DNCA Agent
   restart, could happen for example if one of the entities restarts,
   in case of a (temporary) loss of network connectivity etc.  DNCA Manager
   and DNCA Agent  The
   peering entities MUST have builtin built-in redundancy support to recover
   state in case of failure.

   Example failure cases include the following:

   o  NAT-controller and the DNCA Manager loses session Diameter peer within the NAT-
      controller lose state (e.g. due to a restart).  In this case,

      *  the DNCA Agent Diameter peer within the NAT-device may receive a NCR
         with NC-Request-Type AVP set to INITIAL_REQUEST that matches an
         existing session of the DNCA Agent.
         DNCA Agent returns a Result-Code Diameter peer within the NAT-
         device.  The DNCA Diameter peer within the NAT-device returns a
         Result-Code that contains Duplicate-
         Session-Id Duplicate-Session-Id AVP to report
         the Session-ID of the existing session.  The DNCA Manager Diameter peer
         within the NAT-controller may send an explicit Sesstion Session
         Terminate Request (STR) for the older session, which was lost.

      *  a DNCA Manager Diameter peer may receive accounting records for a
         session that does not exist.  The DNCA Manager Diameter peer sends an
         accounting answer with Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.
         DIAMETER_UNKNOWN_SESSION_ID in response.  On receiving
         this, the
         response, the DNCA Agent Diameter peer clears the session and removes
         the associated session state.

   o  NAT-device and the DNCA Agent loses session Diameter peer within NAT-device lose
      state.  In such a case, the DNCA Agent Diameter peer may receive a NCR
      with NC-Request-Type AVP set to UPDATE_REQUEST for a non-existent
      session.  The DNCA Agent Diameter peer returns NCA with Result-Code set
      to DIAMETER_UNKNOWN_SESSION_ID.

   o  The DNCA Manager Diameter peer within the NAT-controller is unreachable,
      for example detected by Diameter watchdog, or down and accounting request
      requests from the DNCA Agent fails Diameter peer fail to get a response.  The
      mechanism to ensure that a DNCA Manager Diameter peer within the NAT-
      controller no longer has associated state for a session being which was
      cleared or removed by a the DNCA
      Agent Diameter peer within the NAT-device
      is beyond the scope of this document.

   o  The DNCA Agent Diameter peer within the NAT-device is unreachable or
      down and NCR requests fail to get a response.  Handling of this
      case depends on the actual service offering of the service
      provider.  The service provider can could for example choose to terminate the access session to the endpoint. stop
      offering connectivity service.

5.  Use Of The Diameter Base Protocol

   The Diameter Base Protocol defined by [RFC3588] applies with the
   clarifications listed in the present specification.

5.1.  Securing Diameter Messages

   For secure transport of Diameter messages recommendations in
   [RFC3588] apply.

   DNCA Agent Diameter peers MAY verify the their identity of DNCA Manager during the Capabilities
   Exchange Request procedure.

   A DNCA Agent Diameter peer within the NAT-device MAY verify if that a DNCA Manager
   Diameter peer that issues a NCR command is allowed and it is to do so based on:

   o  The identity of the DNCA Manager Diameter peer

   o  The type of NCR Command

   o  The content of the NCR Command
   o  Any combination of the above

5.2.  Accounting Functionality

   Accounting functionality (accounting session state machine, related
   command codes and AVPs) is defined in Section 9 below.

5.3.  Use Of Sessions

   Each DNCA session MUST have a globally unique Session-ID as defined
   in [RFC3588], which MUST NOT be changed during the lifetime of a DNCA
   session.  The Diameter Session-ID serves as the global endpoint
   identifier.  The DNCA Agent and DNCA Manager Diameter peers maintain state associated with
   the Session-ID.  This globally unique Session-ID is used for
   updating, accounting, and terminating the session.  DNCA session MUST
   NOT have more than one outstanding request at any given instant.  A
   DNCA Agent Diameter peer sends an Abort-Session-Request as defined in
   [RFC3588] if it is unable to maintain sessions due to resource
   limitation.

5.4.  Routing Considerations

   It is assumed that the DNCA Manager Diameter peer within a NAT-controller
   knows the DiameterIdentity of DNCA
   Agent the Diameter peer within a NAT-device
   for a given endpoint.  Both the Destination-Realm and
   Destination-Host Destination-
   Host AVPs are present in the request from a DNCA Manager Diameter peer within
   a NAT-controller to a DNCA Agent. Diameter peer within a NAT-device.

5.5.  Advertising Application Support

   Diameter nodes conforming to this specification MUST advertise
   support for DNCA by including the value of TBD in the Auth-
   Application-Id of the Capabilities-Exchange-Request and Capabilities-
   Exchange-Answer command[RFC3588].

6.  DNCA Commands

   The following commands are used to establish, maintain and query NAT NAT-
   bindings.

6.1.  NAT-Control Request (NCR) Command

   The NAT-Control Request (NCR) command, indicated by the command field
   set to TBD and the "R" bit set in the Command Flags field, is sent
   from the DNCA Manager Diameter peer within the NAT-controller to the DNCA Agent
   Diameter peer within the NAT-device in order to install NAT bindings. NAT-bindings.

   User-Name, Logical-Access-Id, Physical-Access-ID, Framed-IP-Address,
   Framed-IPv6-Prefix , Framed-Interface-Id, EGRESS-VLANID, NAS-Port-ID,
   Address-Realm, Calling-Station-ID AVPs serve as identifiers for the
   subscriber.
   endpoint.

   Message Format: format:
      < NC-Request > ::= < Diameter Header: TBD, REQ, PXY>
                       [ Session-Id ]
                       { Auth-Application-Id }
                       { Origin-Host }
                       { Origin-Realm }
                       { Destination-Realm }
                       { Destination-Host }
                       { NC-Request-Type }
                       [ Origin-State-Id ]
                    *1 [ NAT-Control-Remove ]
                    *1 [ NAT-Control-Install ]
                       [ User-Name ]
                       [ Logical-Access-Id ]
                       [ Physical-Access-ID ]
                       [ Framed-IP-Address ]
                       [ Framed-IPv6-Prefix ]
                       [ Framed-Interface-Id ]
                       [ EGRESS-VLANID]
                       [ NAS-Port-ID]
                       [ Address-Realm ]
                       [ Calling-Station-ID ]
                     * [ Proxy-Info ]
                     * [ Route-Record ]
                     * [ AVP ]

6.2.  NAT-Control Answer (NCA) Command

   The NAT-Control-Answer (NCA) command, indicated by the Command-Code
   field set to TBD and the "R" bit cleared in the Command Flags field,
   is sent by the DNCA Agent Diameter peer within the NAT-device in response
   to NAT-Control-Request command.

   Message Format: format:

      <NC-Answer> ::= < Diameter Header: TBD, PXY >
                      [ Session-Id ]
                      { Origin-Host }
                      { Origin-Realm }
                      { NC-Request-Type Result-Code }
                      [ Result-Code NC-Request-Type ]
                    * [ NAT-Control-Definition ]
                      [ Current-NAT-Bindings   ]
                      [ Origin-State-Id ]
                      [ Error-Message ]
                      [ Error-Reporting-Host ]
                    * [ Failed-AVP ]
                    * [ Proxy-Info ]
                      [ Duplicate-Session-ID ]
                    * [ Redirect-Host]
                      [ Redirect-Host-Usage ]
                      [ Redirect-Max-Cache-Time ]
                    * [ Proxy-Info ]
                    * [ Route-Record ]
                    * [ Failed-AVP ]
                    * [ AVP ]
                    * [ AVP ]

7.  NAT Control Application Session State Machine

   This section contains a set of finite state machines, representing
   the life cycle of DNCA session, which MUST be observed by all
   implementations of the DNCA Diameter application.  The DNCA Agent and Manager Diameter
   peers are stateful and the state machine maintained is similar to the
   stateful Client and Server authorization state machine described in
   [RFC3588].  When a session is moved to the Idle state, any resources
   that were allocated for the particular session must be released.  Any
   event not listed in the state machines MUST be considered as an error
   condition, and an answer, if applicable, MUST be returned to the
   originator of the message.

   In the state table, the event 'Failure to send NCR' means that the
   DNCA
   Manager Diameter peer within the NAT-controller is unable to send command the
   NCR command to the desired destination.  This could be due to the
   peer being down, or due to the peer sending back a the transient
   failure or temporary protocol error notification DIAMETER_TOO_BUSY or
   DIAMETER_LOOP_DETECTED in the Result-Code AVP of NCA.

   In the state table "FAILED NCA" means that the DNCA Agent Diameter peer
   within the NAT-device was not able to honor the corresponding NCR.
   This can happen due to any of the transient and permanent error at the NAT-
   device or its associated DNCA Agent Diameter peer within indicated by the
   following error Result-Code values - values: RESOURCE_FAILURE,
   UNKNOWN_BINDING_RULE_NAME, BINDING_FAILURE,
   MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT, SESSION_EXISTS, INSUFFICIENT_CLASSIFIERS
   INSUFFICIENT_CLASSIFIERS.

   The following state machine is observed by a DNCA Manager:
                              MANAGER
      State     Event                          Action     New State
      -------------------------------------------------------------
      Idle      New Host detected that         Send Diameter peer
   within a NAT-controller.  The state machine description uses the term
   "access session" to describe the connectivity service offered to the
   endpoint or host.  "Access session" should not be confused with the
   Diameter session ID.

             DNCA Diameter peer within a NAT-controller
      State     Event                          Action     New State
      -------------------------------------------------------------
      Idle      New endpoint detected that     Send       Pending
                requires NAT Control           NCR
                                               Initial
                                               Request

      Idle      ASR Received                   Send ASA   Idle
                for unknown session            with
                                               Result-Code
                                               = UNKNOWN_
                                               SESSION_ID

      Pending   Successful NCA                 Setup      Open
                received                       complete

      Pending   Successful NCA                 Sent STR   Discon
                received
                but Agent peer unable to provide
                service

      Pending   Error processing successful    Sent STR   Discon
                NCA

      Pending   Failed                         Cleanup    Idle
                NCA received

      Open      NAT control                    Send       Open
                update required                NCR Update
                                               Request

      Open      Successful                                Open
                NCA received

      Open      Failed                         Cleanup    Idle
                NCA received.

      Open      Access Session session end detected    Send STR   Discon

      Open      ASR Received,                  Send ASA   Discon
                client
                access session will comply with be         with
                request to end the session
                terminated                     Result-Code
                                               = SUCCESS,
                                               Send STR.

      Open      ASR Received,                  Send ASA   Open
                client
                access session will not comply        with    with
                request to end the session
                be terminated                  Result-Code
                                               != SUCCESS

      Discon    ASR Received                   Send ASA   Idle

      Discon    STA Received                   Discon.    Idle
                                               user/device

   The following state machine is observed by a DNCA Agent:

                             AGENT Diameter peer
   within a NAT-device.

             DNCA Diameter peer within a NAT-device
      State     Event                          Action     New State
      -------------------------------------------------------------
      Idle      NCR request                    Send       Open
                received, and                  successful
                able to provide requested      NCA
                NAT control service

      Idle      NCR request                    Send       Idle
                received, and                  failed
                unable to provide requested    NCA
                NAT control service

      Open      NCR  request                   Send       Open
                received, and                  successful
                able to provide requested      NCA
                NAT control service

      Open      NCR request                    Send       Idle
                received, and                  failed
                unable to provide requested    NCA,
                NAT control service            Cleanup

      Open      Unable to continue             Send ASR   Discon
                providing requested
                NAT control service

      Discon    Failure to send ASR            Wait,      Discon
                                               resend ASR

      Discon    ASR successfully sent and      Cleanup    Idle
                ASA Received with Result-Code

      Not       ASA Received                   None       No Change. change
      Discon

      Any       STR Received                   Send STA,  Idle
                                               Cleanup.

8.  DNCA AVPs

8.1.  Reused Base Protocol AVPs

   AVPs reused from Diameter Base Protocol [RFC3588] are listed below.

                                                   +-------------------+
                                                   |  AVP Flag rules   |
   +-----------------------------------------------|-----+---+---------+
   |                           AVP                 |     |   |   May   |
   | Attribute Name            Code     Data Type  |MUST |MAY| encrypt |
   +-----------------------------------------------+-----+---+---------+
   |Acct-Interim-Interval      85       Unsigned32 | M   | P |    Y    |
   |Auth-Application-Id        258      Unsigned32 | M   | P |    N    |
   |Destination-Host           293      DiamIdent  | M   | P |    N    |
   |Destination-Realm          283      DiamIdent  | M   | P |    N    |
   |Error-Message              281      UTF8String | M   | P |    N    |
   |Error-Reporting-Host       294      DiamIdent  | M   | P |    N    |
   |Failed-AVP                 279      Grouped    | M   | P |    N    |
   |Origin-Host                264      DiamIdent  | M   | P |    N    |
   |Origin-Realm               296      DiamIdent  | M   | P |    N    |
   |Origin-State-Id            278      Unsigned32 | M   | P |    N    |
   |Proxy-Info                 284      Grouped    | M   | P |    N    |
   |Result-Code                268      Unsigned32 | M   | P |    N    |
   |Route-Record               282      DiamIdent  | M   |   |    N    |
   |Session-Id                 263      UTF8String | M   | P |    Y    |
   |User-Name                  1        UTF8String | M   | P |    Y    |
   +-----------------------------------------------+-----+---+---------+
   |M - Mandatory bit. An AVP with "M" bit set and its value MUST be   |
   |    supported and recognized by a Diameter entity in order the     |
   |    message, which carries this AVP, to be accepted.               |
   |P - Indicates the need for encryption for end-to-end security.     |
   +-------------------------------------------------------------------+

             Figure 9: 10: DIAMETER AVPs used from Diameter base

   The Auth-Application-Id AVP (AVP Code 258) is assigned by IANA to
   Diameter applications.  The value of the Auth-Application-Id for the
   Diameter NAT Control Application is TBD.

8.2.  Additional Result-Code AVP Values

   This section defines new values for the Result-Code AVP which SHALL
   be supported by all Diameter implementations that conform to the
   present document.

8.2.1.  Success

   No new Result-Code AVP value is defined within this category.

8.2.2.  Transient Failures

   Result-Code AVP values that fall within the transient failures
   category are those used to inform a peer that the request could not
   be satisfied at the time that it was received.  The request may be
   able to be satisfied in the future.

   The following new values of the Result-Code AVP are defined:

      RESOURCE_FAILURE (TBD)

         The DNCA Agent Diameter peer within the NAT-device indicates that the
         binding could not be installed or a new session could not be
         created due to resource shortage.

8.2.3.  Permanent Failures

   The Result-Code AVP values, which fall within the permanent failures
   category are used to inform the peer that the request failed, and
   should not be attempted again.  The request may be able to be
   satisfied in the future.

   The following new values of the Result-Code AVP are defined:

      UNKNOWN_BINDING_RULE_NAME (TBD)

         The DNCA Agent Diameter peer within the NAT-device indicates that the
         binding could not be installed or a new session could not be
         created due because the specified NAT-Control-Binding-Rule AVP,
         that refers to resource shortage. a predefined policy template in the NAT-device,
         is unknown.

      BINDING_FAILURE (TBD)

         DNCA indicates that the requested binding(s) could not be
         installed.  For example: Requested ports are already in use.

      MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT (TBD)

         The DNCA Agent Diameter peer within the NAT-device denies the request
         because the maximum number of allowed bindings has been reached
         for the specified Endpoint
         Classifier. endpoint classifier.

      SESSION_EXISTS (TBD)

         The DNCA Agent Diameter peer within the NAT-device denies request to
         initialize a new session, if it already has a DNCA session that
         uses the same set of classifiers as indicated by the DNCA Manager
         Diameter peer within the NAT-controller in the new session
         initialization request.

      INSUFFICIENT_CLASSIFIERS (TBD)

         The DNCA Agent defines request Diameter peer within the NAT-device requests to
         initialize a new session, if the classifiers in the request
         match more than one of the existing sessions on the DNCA Agent.
         Diameter peer within the NAT-device.

8.3.  Reused NASREQ Diameter Application AVPs

   The following AVPs are reused from Diameter Network Access Server
   Application [RFC4005].
                                          +---------------------+
                                          |    AVP Flag rules   |
   +------------------+------+------------|----+-----+----+-----|----+
   |                  | AVP  |            |    |     |SHLD| MUST|    |
   | Attribute Name   | Code |  Value Type|MUST| MAY | NOT|  NOT|Encr|
   |------------------|------|------------|----+-----+----+-----|----|
   | NAS-Port         |   5  | Unsigned32 | M  |  P  |    |  V  | Y  |
   | NAS-Port-Id      |  87  | UTF8String | M  |  P  |    |  V  | Y  |
   | Calling-Station- |  31  | UTF8String | M  |  P  |    |  V  | Y  |
   |   Id             |      |            |    |     |    |     |    |
   | Framed-IP-Address|   8  | OctetString| M  |  P  |    |  V  | Y  |
   | Framed-Interface-|  96  | Unsigned64 | M  |  P  |    |  V  | Y  |
   |   ID   Id             |      |            |    |     |    |     |    |
   | Framed-IPv6-     |  97  | OctetString| M  |  P  |    |  V  | Y  |
   |  Prefix          |      |            |    |     |    |     |    |
   +------------------+------+------------|----+-----+----+-----|----+

            Figure 10: 11: Reused NASREQ Diameter application AVPs

8.4.  Reused AVPs from RFC 4675

   The following AVPs are reused from "RADIUS Attributes for Virtual LAN
   and Priority Support" specification [RFC4675].
                                          +---------------------+
                                          |    AVP Flag rules   |
   +------------------+------+------------|----+-----+----+-----|----+
   |                  | AVP  |            |    |     |SHLD| MUST|    |
   | Attribute Name   | Code |  Value Type|MUST| MAY | NOT|  NOT|Encr|
   |------------------|------|------------|----+-----+----+-----|----|
   | Egress-VLANID    |  56  | OctetString| M  |  P  |    |  V  | Y  |
   +------------------+------+------------|----+-----+----+-----|----+

                Figure 11: 12: Reused attributes from RFC 4675

8.5.  Reused AVPs from Diameter QoS Application

   The following AVPs are reused from the Traffic Classification and
   Quality of Service (QoS) Attributes for Diameter [RFC5777].
                                                   +-------------------+
                                                   |  AVP Flag rules   |
   +-----------------------------------------------|-----+---+---------+
   |                           AVP                 |     |   |   May   |
   | Attribute Name            Code     Data Type  |MUST |MAY| encrypt |
   +-----------------------------------------------+-----+---+---------+
   |Port                       TBD     Integer32   |  M  | P |    Y    |
   |IP-Address-Mask            TBD     Grouped     |  M  | P |    Y    |
   |Protocol                   TBD     Enumerated  |  M  | P |    Y    |
   |Direction                  TBD     Enumerated  |  M  | P |    Y    |
   +-----------------------------------------------+-----+---+---------+
   |M - Mandatory bit. An AVP with "M" bit set and its value MUST be   |
   |    supported and recognized by a Diameter entity in order the     |
   |    message, which carries this AVP, to be accepted.               |
   |P - Indicates the need for encryption for end-to-end security.     |
   +-------------------------------------------------------------------+

                     Figure 12: 13: Reused QoS-attributes

8.6.  Reused AVPs from ETSI ES 283 034, e4 Diameter Application

   The following AVPs are reused from the Diameter e4 Application
   [ETSIES283034].
                                                   +-------------------+
                                                   |  AVP Flag rules   |
   +-----------------------------------------------|-----+---+---------+
   |                           AVP                 |     |   |   May   |
   | Attribute Name            Code     Data Type  |MUST |MAY| encrypt |
   +-----------------------------------------------+-----+---+---------+
   |Address-Realm              301     OctetString | M,V |   |    Y    |
   |Logical-Access-Id          302     OctetString |   V | M |    Y    |
   |Physical-Access-ID         313     UTF8String  |   V | M |    Y    |
   +-----------------------------------------------+-----+---+---------+
   |M - Mandatory bit. An AVP with "M" bit set and its value MUST be   |
   |    supported and recognized by a Diameter entity in order the     |
   |    message, which carries this AVP, to be accepted.               |
   |P - Indicates the need for encryption for end-to-end security.     |
   |V - Indicates whether the optional Vendor-ID field is present      |
   |    in the AVP header. Vendor-Id header of all AVPs in             |
   |    this table will be set to ETSI (13019).                        |
   +-------------------------------------------------------------------+

            Figure 13: 14: Reused AVPs from Diameter e4 application

8.7.  DNCA Defined AVPs

   The following table describes the new Diameter AVPs used in this
   document.
                                                   +-------------------+
                                                   |  AVP Flag rules   |
   +-----------------------------------------------|-----+---+---------+
   |                       AVP  Section            |     |   |   May   |
   | Attribute Name        Code Defined Data Type  |MUST |MAY| encrypt |
   +-----------------------------------------------+-----+---+---------+
   |NC-Request-Type        TBD  7.7.1  8.7.1   Enumerated | M   | P |    Y    |
   |NAT-Control-Install    TBD  7.7.2  8.7.2   Grouped    | M   | P |    Y    |
   |NAT-Control-Remove     TBD  7.7.3  8.7.3   Grouped    | M   | P |    Y    |
   |NAT-Control-Definition TBD  7.7.4  8.7.4   Grouped    | M   | P |    Y    |
   |NAT-Internal-Address   TBD  7.7.5  8.7.5   Grouped    | M   | P |    Y    |
   |NAT-External-Address   TBD  7.7.6  8.7.6   Grouped    | M   | P |    Y    |
   |Max-NAT-Bindings       TBD  7.7.7  8.7.7   Unsigned32 | M   | P |    Y    |
   |NAT-Control-           TBD  7.7.8  8.7.8   OctetString| M   | P |    Y    |
   | Binding-Rule                                  |     |   |         |
   |Duplicate-             TBD  7.7.9  8.7.9   UTF8String | M   | P |    Y    |
   | Session-ID                                    |     |   |         |
   |NAT-Control-Record     TBD  8.2.1  9.2.1   Grouped    | M   | P |    Y    |
   |NAT-Control-           TBD  8.2.2  9.2.2   Enumerated | M   | P |    Y    |
   | Binding-Status                                |     |   |         |
   |Current-NAT-Bindings   TBD  8.2.3  9.2.3   Unsigned32 | M   | P |    Y    |
   +-----------------------------------------------+-----+---+---------+
   |M - Mandatory bit. An AVP with "M" bit set and its value MUST be   |
   |    supported and recognized by a Diameter entity in order the     |
   |    message, which carries this AVP, to be accepted.               |
   |P - Indicates the need for encryption for end-to-end security.     |
   |V - Vendor specific bit that indicates whether the optional        |
   |    Vendor-ID field is present in the AVP header.                  |
   +-------------------------------------------------------------------+

                       Figure 14: 15: New Diameter AVPs

8.7.1.  NC-Request-Type AVP

   The NC-Request-Type AVP (AVP Code TBD) is of type Enumerated and
   contains the reason for sending the NAT-Control-Request command.  It
   shall be present in all NAT-Control-Request messages.

   The following values are defined:

      INITIAL_REQUEST (1)

         An Initial Request is used to install binding at DNCA Agent on initiate a successful access Diameter NAT control
         session setup. between the DNCA Diameter peers.

      UPDATE_REQUEST (2)
         An Update Request is used to update bindings previously
         installed on a given access session, to add new binding on a
         given access session, or to remove one or several binding(s)
         activated on a given access session.

      QUERY_REQUEST (4) (3)

         Query Request is used to query DNCA Agent a NAT-device about the currently
         installed bindings for an endpoint classifier.

8.7.2.  NAT-Control-Install AVP

   The NAT-Control AVP (AVP code TBD) is of type Grouped, and it is used
   to activate or install NAT bindings.  It also contains Max-NAT-
   Bindings that defines the maximum number of NAT bindings to be
   allowed for a subscriber and the NAT-Control-Binding-Rule that
   references a predefined policy template on DNCA Agent the NAT-device that may
   contain static
   bindings, binding, a maximum number of bindings to be allowed, an IP-
   address pool from which external binding address addresses should be
   allocated.

   AVP format:
     NAT-Control-Install ::= < AVP Header: TBD >
                              * [ NAT-Control-Definition ]
                                [ NAT-Control-Binding-Rule ]
                                [ Max-NAT-Bindings]
                              * [ AVP ]

8.7.3.  NAT-Control-Remove AVP

   The NAT-Control-Remove AVP (AVP code TBD) is of type Grouped, and it
   is used to deactivate or remove NAT bindings. NAT-bindings.

   AVP format:
     NAT-Control-Remove ::= < AVP Header: TBD >
                             * [ NAT-Control-Definition ]
                               [ NAT-Control-Binding-Rule ]
                             * [ AVP ]

8.7.4.  NAT-Control-Definition AVP

   The NAT-Control-Definition AVP (AVP code TBD) is of type Grouped, and
   it describes a binding.

   The NAT-Control-Definition AVP uniquely identifies the binding
   between the DNCA Agent and DNCA Manager. Diameter peers.

   If both the NAT-Internal-Address and NAT-External-Address AVP(s) are
   supplied, it is a pre-defined binding.

   The Protocol AVP describes the transport protocol for the binding.
   The NAT-Control-Definition AVP can contain either zero or one
   Protocol AVP.  If the Protocol AVP is omitted and if both internal
   and external address IP-address are specified then the binding reserves the
   addresses
   IP-addresses for all transport protocols.

   The Direction AVP is of type Enumerated.  It specifies the direction
   for the binding.  The values of the enumeration applicable in this
   context are: "IN","OUT".  If Direction AVP is OUT or absent, the NAT-
   Internal-Address refers to the address IP-address of the subscriber device endpoint that needs
   to be translated.  If Direction AVP is "IN", NAT-Internal-
   Address NAT-Internal-Address is
   the destination address IP-address that has to be translated.

   AVP format:
     NAT-Control-Definition ::= < AVP Header: TBD >
                                 { NAT-Internal-Address }
                                 [ Protocol ]
                                 [ Direction ]
                                 [ NAT-External-Address ]
                                 [ Session-Id ]
                               * [ AVP ]

8.7.5.  NAT-Internal-Address AVP

   The NAT-Internal-Address AVP (AVP code TBD) is of type Grouped.  It
   describes the internal IP address IP-address and port for a binding.  Framed-
   IPV6-Prefix and Framed-IP-Address AVPs are mutually exclusive.

   AVP format:
     NAT-Internal-Address ::= < AVP Header: TBD >
                               [ Framed-IP-Address ]
                               [ Framed-IPv6-Prefix ]
                               [ Port]
                             * [ AVP ]

8.7.6.  NAT-External-Address AVP

   The NAT-External-Address AVP (AVP code TBD) is of type Grouped, and
   it describes the external IP address IP-address and port for a binding.  IP-
   Address-Mask AVP can only be specified when the Framed-IP-Address AVP
   is present.  External IP address  The external IP-address specified in this attribute can
   be reused for multiple subscribers endpoints by specifying the same address in
   the respective NAT-External-Address AVPs.

   AVP format:

     NAT-External-Address ::= < AVP Header: TBD >
                               [ Framed-IP-Address ]
                               [ IP-Address-Mask ]
                               [ Port ]
                             * [ AVP ]

8.7.7.  Max-NAT-Bindings

   The Max-NAT-Bindings AVP (AVP code TBD) is of type Unsigned32.  It
   indicates the maximum number of NAT bindings allowed. NAT-bindings allowed for a particular
   endpoint.

8.7.8.  NAT-Control-Binding-Rule AVP

   The NAT-Control-Binding-Rule AVP (AVP code TBD) is of type
   OctetString.  It defines a name for a policy template that will be is
   predefined at NAT. the NAT-device.  Details on the contents and structure
   of the template and configuration are outside the scope of this
   document.  The policy to which this AVP refers to may contain NAT NAT-
   bindings,
   address IP-address pool for allocating the external address allocation IP-address of NAT binding, a
   NAT-binding, and maximum number of allowed NAT bindings. NAT-bindings.  Such policy
   template can be reused by specifying the same NAT-Control-Binding-Rule NAT-Control-Binding-
   Rule AVP in the corresponding NAT-
   Control-Install NAT-Control-Install AVPs of multiple subscribers.
   endpoints.

8.7.9.  Duplicate-Session-Id AVP

   The Duplicate-Session-Id AVP (AVP Code TBD) is of type UTF8String.
   It is used to report error errors and contains the Session-Id of an
   existing session.

9.  Accounting Commands

   The DNCA reuses session based accounting as defined in the Diameter
   Base Protocol[RFC3588] to report the bindings per endpoint.  This
   reporting is achieved by sending Diameter Accounting Requests (ACR)
   [Start, Interim and Stop] from the DNCA Agent Diameter peer within the NAT-
   device to its associated DNCA Manager. Diameter peer within the NAT-
   controller.

   The DNCA Agent Diameter peer within the NAT-device sends an ACR Start on
   receiving an a NCR with NC-Request-
   Type NC-Request-Type AVP set to INITIAL_REQUEST for a
   session or on creation of the first binding for a session requested
   in an earlier NCR.  DNCA may send ACR Interim updates, if required,
   either due to a change in bindings resulting from a NCR with NC-Request-Type NC-
   Request-Type AVP set to UPDATE_REQUEST, or periodically as specified
   in Acct-Interim-Interval by the DNCA Manager, Diameter peer within the NAT-
   controller, or when it creates or tears down bindings.  An ACR Stop
   is sent by the DNCA Agent Diameter peer within the NAT-device on receiving
   STR.

   The function of correlating the multiple bindings used by an endpoint
   at any given time is relegated to the post processor.

   The DNCA Agent Diameter peer within the NAT-device may trigger an interim
   accounting record when maximum number of bindings, if received in
   NCR, is reached.

9.1.  NAT Control Accounting Messages

   The ACR and ACA messages are reused as defined in Diameter Base
   Protocol [RFC3588] for exchanging endpoint NAT binding details
   between the DNCA Agent and DNCA Manager. Diameter peers.  DNCA Application ID is used in the
   accounting commands.  ACR contains one or more optional NAT-
   Control-Record NAT-Control-
   Record AVP to report the bindings.  DNCA Agent  The NAT-device indicates the
   number of allocated NAT bindings to DNCA Manager NAT-controller using the Current-
   NAT-Bindings AVP.  This number needs to match the number of bindings
   identified as active within the NAT-Control-Record AVP.

9.2.  NAT Control Accounting AVPs

   In addition to AVPs for ACR specified in [RFC3588], the DNCA Agent Diameter
   peer within the NAT-device must add the NAT-Control-Record AVP.

9.2.1.  NAT-Control-Record

   The NAT-Control-Record AVP (AVP code TBD) is of type Grouped.  It
   describes a binding and its status.  If NAT-Control-Binding-Status is
   set to Created, Event-Timestamp indicates the binding creation time.
   If NAT-Control-Binding-Status is set to Removed, Event-Timestamp
   indicates the binding removal time.  If NAT-Control-Binding-Status is
   active, Event-Timestamp need not be present; if a value is present,
   it indicates that binding is active at the given time.
     NAT-Control-Record ::= < AVP Header: TBD >
                            { NAT-Control-Definition }
                            { NAT-Control-Binding-Status }
                            [ Event-Timestamp ]

9.2.2.  NAT-Control-Binding-Status

   The NAT-Control-Binding-Status AVP (AVP code TBD) is of type
   enumerated.  It indicates the status of the binding - created,
   removed, or active.

   The following values are defined:

      Created (1)

         NAT binding is created.

      Active (2)

         NAT binding is active.

      Removed (3)

         NAT binding was removed.

9.2.3.  Current-NAT-Bindings

   The Current-NAT-Bindings AVP (AVP code TBD) is of type Unsigned32.
   It indicates number of NAT bindings active on NAT device. NAT-device.

10.  AVP Occurrence Table

   The following sections presents the AVPs defined in this document and
   specifies the Diameter messages in which, they MAY be present.  Note:
   AVPs that can only be present within a Grouped AVP are not
   represented in this table.

   The table uses the following symbols:

      0         The AVP MUST NOT be present in the message.

      0+        Zero or more instances of the AVP MAY be present in the
                message.

      0-1       Zero or one instance of the AVP MAY be present in the
                message.  It is considered an error if there is more
                than one instance of the AVP.

      1         One instance of the AVP MUST be present in the message.

      1+        At least one instance of the AVP MUST be present in the
                message.

10.1.  DNCA AVP Table for NAT Control Initial and Update Requests

   The following table lists DNCA specific AVPs that have to be present
   in NCR and NCA with NC-Request-Type set to INITIAL_REQUEST or
   UPDATE_REQUEST.

                                       +-------------------+
                                       |  Command Code     |
   +-----------------------------------+-------------------+
   | Attribute Name                        NCR    NCA      |
   +-------------------------------------------------------+
   |NC-Request-Type                         1      1       |
   |NAT-Control-Install                     0-1    0       |
   |NAT-Control-Remove                      0-1    0       |
   |NAT-Control-Definition                  0      0       |
   |Current-NAT-Bindings                    0      0       |
   |Duplicate-Session-Id                    0      0-1     |
   +-------------------------------------------------------+

10.2.  DNCA AVP Table for Session Query request

   The following table lists DNCA specific AVPs that have to be present
   in NCR and NCA with NC-Request-Type set to QUERY_REQUEST.
                                       +-------------------+
                                       |  Command Code     |
   +-----------------------------------+-------------------+
   | Attribute Name                        NCR    NCA      |
   +-------------------------------------------------------+
   |NC-Request-Type                         1      1       |
   |NAT-Control-Install                     0      0       |
   |NAT-Control-Remove                      0      0       |
   |NAT-Control-Definition                  0      0+      |
   |Current-NAT-Bindings                    0      1       |
   |Duplicate-Session-Id                    0      0       |
   +-------------------------------------------------------+

10.3.  DNCA AVP Table for Accounting Message

   The following table lists DNCA specific AVPs, which may or may not be
   present in ACR and ACA messages.
                                       +-------------------+
                                       |  Command Code     |
   +-----------------------------------+-------------------+
   | Attribute Name                        ACR    ACA      |
   +-------------------------------------------------------+
   |NAT-Control-Record                      0+     0       |
   |Current-NAT-Bindings                    1      0       |
   +-------------------------------------------------------+

11.  IANA Considerations

   This section contains the namespaces that have either been created in
   this specification specification, or had their the values assigned to existing namespaces
   managed by IANA.

   In the subsections below, when we speak about review by a Designated
   Expert, please note that the designated expert will be assigned by
   the IESG.  Initially, such Expert discussions take place on the AAA
   WG mailing list.

11.1.  Application Identifier

   This specification assigns the value <TBD>, 'Diameter NAT Control
   Application', to the Application Identifier namespace defined in
   [RFC3588].  See Section 4 for more information.

11.2.  Command Codes

   IANA is requested to allocate command

   This specification uses the value <TBD> from the Command code values
   namespace defined in [RFC3588] for the following.

   Registry:

   +------------+-----------------------------------+------------------+
   | Code Value | Name                              | Reference        |
   +------------+-----------------------------------+------------------+
   | to be      | NAT-Control-Request (NCR),        | Section 6.1,     |
   | assigned   |
   NAT-Control-Answer (NCA)          | commands.  See Section 6.1 and Section 6.2      |
   +------------+-----------------------------------+------------------+

                          Table 1: Command codes

11.2.
   for more information on these commands.

11.3.  AVP Codes

   IANA is requested to allocate

   This specification assigns the values <TBD> from the AVP codes for code
   namespace defined in [RFC3588].  See Figure 15for the following AVPs that
   are assignment of
   the namespace in this specification.

11.4.  Result-Code AVP Values

   This specification assigns the values <TBD> (4xxx, 5xxx, 5xxx, 5xxx,
   5xxx,5xxx) from the Result-Code AVP value namespace defined in
   [RFC3588].  See Section 8.2 for the assignment of the namespace in
   this document.

   Registry:

         +----------------+----------------------------+---------------+
         | Code Value     | Name                       | Reference     |
         +----------------+----------------------------+---------------+
         | to be assigned | specification.

11.5.  NC-Request-Type            | Section 8.7.1 |
         | to be assigned | NAT-Control-Install        | Section 8.7.2 |
         | to be assigned | NAT-Control-Remove         | Section 8.7.3 |
         | to be assigned | NAT-Control-Definition     | Section 8.7.4 |
         | to be assigned | NAT-Internal-Address       | Section 8.7.5 |
         | to be assigned | NAT-External-Address       | Section 8.7.6 |
         | to be assigned | Max-NAT-Bindings           | Section 8.7.7 |
         | to be assigned | NAT-Control-Binding-Rule   | Section 8.7.8 |
         | to be assigned | Duplicate-Session-Id       | Section 8.7.9 |
         | to be assigned | NAT-Control-Record         | Section 9.2.1 |
         | to be assigned | NAT-Control-Binding-Status | Section 9.2.2 |
         | to be assigned | Current-NAT-Bindings       | Section 9.2.3 |
         +----------------+----------------------------+---------------+

                            Table 2: AVP codes

11.3.  AVP Values
11.3.1.  Result-Code AVP Values

   As defined in Section 8.2 defines several new values for 8.7.1, the Result-Code NC-Request-Type AVP for
   transient and permanent failures. includes
   Enumerated type values 1 - 3.  IANA has created and is requested to allocate the
   corresponding maintaining a
   namespace for this AVP.  All remaining values from the ranges are available for transient (4xxx) and
   permantent (5xxx) failures.

   +-----------+---------------------------------------+---------------+
   | Code      | Name                                  | Reference     |
   | Value     |                                       |               |
   +-----------+---------------------------------------+---------------+
   | to be     | RESOURCE_FAILURE                      | Section 8.2.2 |
   | assigned  |                                       |               |
   | (4xxx)    |                                       |               |
   | to be     | UNKNOWN_BINDING_RULE_NAME             | Section 8.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | BINDING_FAILURE                       | Section 8.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT | Section 8.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | SESSION_EXISTS                        | Section 8.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | INSUFFICIENT_CLASSIFIERS              | Section 8.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   +-----------+---------------------------------------+---------------+

                      Table 3: Result Code
   assignment by a Designated Expert [RFC5226].

11.6.  NAT-Control-Binding-Status AVP Values

11.4.  Application IDs

   IANA is requested to allocate the following application ID using the
   next value from the 7-16777215 range.

   Registry:

       +----------------+----------------------------------+-----------+
       | ID Value       | Name                             | Reference |
       +----------------+----------------------------------+-----------+
       | to be assigned | Diameter NAT Control Application | Section 4 |
       +----------------+----------------------------------+-----------+

                 Table 4:  Diameter Application ID

   As defined in Section 8.7.1, the NAT-Control-Binding-Status AVP
   includes Enumerated type values 1 - 3.  IANA has created and is
   maintaining a namespace for this AVP.  All remaining values are
   available for assignment by a Designated Expert [RFC5226].

12.  Security Considerations

   Similar to the impact of Diameter QoS application (see [RFC5866]) on
   authorization of QoS reservations, this

   This document describes procedures for authorizing controlling NAT related
   attributes and parameters by an entity, which is non-local non-local to the
   device performing NAT.  This section discusses security
   considerations for DNCA interactions between the Diameter peers
   within a NAT-controller and a NAT-device.  Security between NAT-
   controller and NAT-device has a number of components: authentication,
   authorization, integrity, and confidentiality.

   Authentication refers to confirming the identity of an originator for
   all datagrams received from the originator.  Lack of authentication
   of Diameter messages between the Diameter peers can jeopardize the
   fundamental service of the peering network elements.  A consequence
   of not authenticating the message sender by the recipient would be
   that an attacker could spoof the identity of a "legitimate"
   authorizing entity in order to change the behavior of the receiver.
   An attacker could for example launch a denial of service attack by
   setting the maximum number of bindings for a session on the NAT-
   device to zero; provision bindings on a NAT-device which include IP-
   addresses already in use in other parts of the network; or request
   session termination of the Diameter session and hamper a user's
   connectivity.  Lack of authentication of a NAT-device to a NAT-
   controller could lead to situations where the NAT-device could
   provide a wrong view of the resources (i.e.  NAT-bindings).  In
   addition, templates on the NAT-device specifying pre-defined binding
   rules could be configured differently than expected by the NAT-
   controller.  Failing of any of the two DNCA Diameter peers to provide
   the required credentials should be subject to logging.

   Authorization refers to whether a particular authorizing entity is
   authorized to signal a network element requests for one or more
   applications, adhering to a certain policy profile.  Failing the
   authorization process might indicate a resource theft attempt or
   failure due to administrative and/or credential deficiencies.  In
   either case, the network element should take the proper measures to
   log such attempts.

   Integrity is required to the device performing NAT.  The security
   considerations for ensure that a Diameter message exchanged
   between the Diameter QoS application (see [RFC5866]
   section 11) apply in peers has not been maliciously altered by
   intermediate devices.  The result of a similar way to DNCA.  To secure lack of data integrity
   enforcement in an untrusted environment could be that an impostor
   will alter the
   information exchange messages exchanged between the authorizing entity (DNCA Manager)
   and the NAT device (DNCA Agent) requires bilateral authentication peers.  This could
   cause a change of behavior of the involved parties, authorization peers, including the potential of a
   denial of service.

   Confidentiality protection of Diameter messages ensures that the involved parties
   signaling data is accessible only to
   perform the required procedures and functions, authorized entities.  When
   signaling messages between the DNCA Diameter peers traverse untrusted
   networks, lack of confidentiality will allow eavesdropping and procedures
   traffic analysis.

   Diameter offers security mechanisms to
   ensure integrity and confidentiality of deal with the information exchange MAY
   be performed. functionality
   demanded above.  DNCA makes use of the capabilities offered by
   Diameter and the underlying transport protocols to deliver these
   requirements (see Section 5.1 ).

   It  If the DNCA communication traverses
   untrusted networks, it is assumed that messages between DNCA Agent Diameter
   peers are secured using either IPsec or TLS.  Please refer to
   [RFC3588], section 13 for details.  DNCA Diameter peers MAY perform
   bilateral authentication, authorization as well as procedures to
   ensure integrity and confidentiality of the information exchange.

   It is assumed that the DNCA Manager Diameter peers are typically in the same
   domain and have a mutual trust set up.  Authorization  This document does not
   specify a mechanisms for authorization between the DNCA Agent and
   DNCA Manager Diameter
   peers.  It is beyond assumed that the scope DNCA Diameter peers are provided with
   sufficient information to make an authorization decision.  The
   information can come from various sources, for example the peering
   devices could store local authentication policy, listing the
   identities of this document. authorized peers.

13.  Acknowledgements

   The authors would like to thank Miguel A. Garcia, Jouni Korhonen,
   Matt Lepinski, Avi Lior, Chris Metz, Pallavi Mishra, Lionel Morand,
   Hannes Tschofenig, Shashank Vikram, Greg Weber, and Glen Zorn for
   their input on this document.

14.  Change History (to be removed prior to publication as an RFC)

   Changes from -00 to -01

   a.  new values for Result-Code AVP used - instead of Experimental-
       Result AVP

   b.  added support for transport specific binding (UDP/TCP)

   c.  added support for twice-NAT

   d.  clarified the use of the two different types of query-requests

   Changes from -01 to -02
   a.  Reference to pull mode removed, session initiation event
       clarified in section 4.1

   b.  added Redirect-* AVPs in NCA command

   c.  Removed reference to Called-Station-Id AVP in NCR command

   d.  Editorial changes

   e.  added support for bindings providing AFT (NAT64)

   Changes from -02 to -03

   a.  Editorial changes

   Changes from -03 to -04

   a.  Editorial changes suggested in WG Lastcall last call review

   b.  Removed NCR Request type terminate and replaced with STR

   c.  All references to Auth-Session-State are removed and a new
       section to describe FSM for Manager and Agent has been added

   d.  Clarified reuse of External address and address pools among
       multiple subscribers

   Changes from -04 to -05

   a.  Removed references to Large Scale NAT as per review comments

   Changes from -05 to -06

   a.  Editorial changes

   Changes from -06 to -07

   a.  Added a note in section 4.3 stating the state of pre-existing
       bindings on update failure

   b.  Security considerations are made consistent between sections 5.1
       and 12

   c.  Editorial changes

   Changes from -07 to -08
   a.  Added section 4.6 to describe session abort

   b.  Editorial changes

   c.  Nomenclature change: From DNCA Agent/Manager to DNCA Diameter
       peers identifying the location where they reside (NAT-controller
       or NAT-device)

   d.  IANA consideration Section format changes

   e.  Updated security section (included considerations directly,
       rather than referring to Diameter QoS similarities).

15.  References
15.1.  Normative References

   [ETSIES283034]
              ETSI, "Telecommunications and Internet Converged Services
              and Protocols for Advanced Networks (TISPAN),Network
              Attachment Sub-System (NASS),e4 interface based on the
              Diameter protocol.", September 2008.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

   [RFC4005]  Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
              "Diameter Network Access Server Application", RFC 4005,
              August 2005.

   [RFC4675]  Congdon, P., Sanchez, M., and B. Aboba, "RADIUS Attributes
              for Virtual LAN and Priority Support", RFC 4675,
              September 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5777]  Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M.,
              and A. Lior, "Traffic Classification and Quality of
              Service (QoS) Attributes for Diameter", RFC 5777,
              February 2010.

15.2.  Informative References

   [RFC5866]  Sun, D., McCann, P., Tschofenig, H., Tsou, T., Doria, A.,
              and G. Zorn, "Diameter Quality-of-Service Application",
              RFC 5866, May 2010.

Authors' Addresses

   Frank Brockners
   Cisco
   Hansaallee 249, 3rd Floor
   DUESSELDORF, NORDRHEIN-WESTFALEN  40549
   Germany

   Email: fbrockne@cisco.com

   Shwetha Bhandari
   Cisco
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA 560 087
   India

   Email: shwethab@cisco.com

   Vaneeta Singh
   18, Cambridge Road
   Bangalore 560008
   India

   Email: vaneeta.singh@gmail.com

   Victor Fajardo
   Telcordia Technologies
   1 Telcordia Drive #1S-222
   Piscataway, NJ 08854
   USA

   Email: vf0213@gmail.com