Internet Engineering Task Force                             F. Brockners
Internet-Draft                                               S. Bhandari
Intended status: Standards Track                                   Cisco
Expires: September 8, 2010 January 13, 2011                                       V. Singh
                                                         Mavenir Systems
                                                              V. Fajardo
                                                  Telcordia Technologies
                                                           March 7,
                                                           July 12, 2010

   Diameter Network Address and Port Translation Control Application
                     draft-ietf-dime-nat-control-02
                     draft-ietf-dime-nat-control-03

Abstract

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

Status of this Memo

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   This Internet-Draft will expire on September 8, 2010. January 13, 2011.

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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 The Diameter NAPT Control
           Application  . . . . . . . . . DNCA  . . . . . . . . . . . . . .  8  9
   4.  Diameter NAT Control Application  DNCA Session Establishment and Management  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1.  Parties Involved . . . . . . . . . . . . . . . . . . . . . 11
     4.2.  Session Establishment  . . . . . . . . . . . . . . . . . . 11
     4.3.  Session Re-Authorization . . . . . . . . . . . . . . . . . 13
     4.4.  Session And and Binding Query  . . . . . . . . . . . . . . . . 15
     4.5.  Session Termination  . . . . . . . . . . . . . . . . . . . 17
     4.6.  DNCA Manager/Agent Manager and Agent Failures  . . . . . . . . . . . . . . . 18
   5.  Use Of The Diameter Base Protocol  . . . . . . . . . . . . . . 19 18
     5.1.  Securing Diameter Messages . . . . . . . . . . . . . . . . 19
     5.2.  Accounting Functionality . . . . . . . . . . . . . . . . . 20 19
     5.3.  Use Of Sessions  . . . . . . . . . . . . . . . . . . . . . 20 19
     5.4.  Routing Considerations . . . . . . . . . . . . . . . . . . 20 19
     5.5.  Advertising Application Support  . . . . . . . . . . . . . 20 19
   6.  Diameter NAT Control Application  DNCA Commands  . . . . . . . . . . . . . . . . . . . . . . . . 20
     6.1.  NAT-Control Request (NCR) Command  . . . . . . . . . . . . 21 20
     6.2.  NAT-Control Answer (NCA) Command . . . . . . . . . . . . . 21
   7.  Diameter NAT Control Application  DNCA AVPs  . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     7.1.  Reused Base Protocol AVPs  . . . . . . . . . . . . . . . . 22
     7.2.  Additional Result-Code AVP Values  . . . . . . . . . . . . 23
       7.2.1.  Success  . . . . . . . . . . . . . . . . . . . . . . . 23
       7.2.2.  Transient Failures . . . . . . . . . . . . . . . . . . 24
       7.2.3.  Permanent Failures . . . . . . . . . . . . . . . . . . 24
     7.3.  Reused NASREQ Diameter Application AVPs  . . . . . . . . . 25
     7.4.  Reused from RFC 4675 . . . . . . . . . . . . . . . . . . . 25
     7.5.  Reused from Diameter QoS Application . . . . . . . . . . . 26
     7.6.  Reused From from ETSI ES 283 034, e4 Diameter Application . . . 26
     7.7.  Diameter NAT Control Application  DNCA Defined AVPs  . . . . . . . . . . . . . . . . . . . . 27
       7.7.1.  NC-Request-Type AVP  . . . . . . . . . . . . . . . . . 27
       7.7.2.  NAT-Control-Install AVP  . . . . . . . . . . . . . . . 28
       7.7.3.  NAT-Control-Remove AVP . . . . . . . . . . . . . . . . 28
       7.7.4.  NAT-Control-Definition AVP . . . . . . . . . . . . . . 29
       7.7.5.  NAT-Internal-Address AVP . . . . . . . . . . . . . . . 29
       7.7.6.  NAT-External-Address AVP . . . . . . . . . . . . . . . 30
       7.7.7.  Max-NAT-Bindings . . . . . . . . . . . . . . . . . . . 30
       7.7.8.  NAT-Control-Binding-Rule AVP . . . . . . . . . . . . . 30
       7.7.9.  Duplicate-Session-Id AVP . . . . . . . . . . . . . . . 30
   8.  Accounting Commands  . . . . . . . . . . . . . . . . . . . . . 30
     8.1.  NAT Control Accounting Messages  . . . . . . . . . . . . . 31
     8.2.  NAT Control Accounting AVPs  . . . . . . . . . . . . . . . 31
       8.2.1.  NAT-Control-Record . . . . . . . . . . . . . . . . . . 31
       8.2.2.  NAT-Control-Binding-Status . . . . . . . . . . . . . . 31
       8.2.3.  Current-NAT-Bindings . . . . . . . . . . . . . . . . . 32
   9.  AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . . 32
     9.1.  DNCA AVP Table for NAT control initial Control Initial and update
           requests Update
           Requests . . . . . . . . . . . . . . . . . . . . . . . . . 33
     9.2.  DNCA AVP Table for Session Query request . . . . . . . . . 33
     9.3.  DNCA AVP Table for NAT Control Terminate requests  . . . . 33
     9.4.  DNCA AVP Table For for Accounting Message  . . . . . . . . . . 34
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 34
     10.1. Command Codes  . . . . . . . . . . . . . . . . . . . . . . 34
     10.2. AVP Codes  . . . . . . . . . . . . . . . . . . . . . . . . 35
     10.3. AVP Values . . . . . . . . . . . . . . . . . . . . . . . . 35
       10.3.1. Result-Code AVP Values . . . . . . . . . . . . . . . . 35
     10.4. Application IDs  . . . . . . . . . . . . . . . . . . . . . 36
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 36
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 37
   13. Change History (to be removed prior to publication as an
       RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 38
     14.2. Informative References . . . . . . . . . . . . . . . . . . 38
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39

1.  Introduction

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

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

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

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

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

       *  Allocation of an external IP-address IP address for a given internal IP-
          address. IP
          address: The allocated external IP-address will be 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 IP address but does not control the allocation
          of the external IP-address (e.g. IP address; for example, SIP-proxy server deployments).
          deployments.

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

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

   5.  Query functionality to retrieve  Queries and retrieves details about bindings on demand. demand: This
       feature complements the previously mentioned accounting
       functionality mentioned above (see
       functionality(see item 4).  The query functionality complements
       alternative information query
       mechanisms mechanisms, such as SNMP-based mechanisms,
       mechanism, if available.

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

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

      AAA: Authentication, Authorization, Accounting

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

      NAS: Network Access Server

3.  Deployment Framework

3.1.  Deployment Scenario

   Figure 1 shows a typical network deployment for internet Internet access.  A
   user's IPv4-host IPv4 host gains access to the internet Internet though a Network Access
   Server (NAS) 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 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
   performs network address (and and port and optionally protocol) 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 would be put in place without any endpoint
   awareness, the service offerings of the service provider would could be
   hampered.  Provisioning static NAT-bindings NAT bindings for particular endpoints,
   using different public IP-address IP address pools for different set sets of endpoints
   (e.g.
   endpoints; for example, residential or business customers), as well as customers, and
   reporting on the allocated bindings on a per-endpoint per endpoint basis would be is burdensome
   for a service provider if the NAT device would is not be aware of endpoints
   and allow for per-endpoint allows per endpoint control and management management, which easily
   integrates with the already existing per-endpoint per endpoint management
   infrastructure of the service provider.

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

               Figure 2: Access network deployment with LSN

3.2.  Diameter NAPT Control Application Overview

   The Diameter NAT Control Application DNCA runs between a Diameter NAT
   Control Application DNCA Agent on the NAT device and the Diameter NAT Control
   Application DNCA
   Manager.  DNCA allows for per-endpoint per endpoint control and management of a NAT.
   Being based on Diameter, DNCA integrates well with the suite of
   Diameter applications deployed for per-endpoint per endpoint authentication,
   authorization, accounting, and policy control in service provider
   networks.

   DNCA offers request offers:

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

   o  Provides per endpoint reporting on of the allocated NAT-
   bindings, as well as to provide for NAT bindings.

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

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

3.3.  Deployment Scenarios For DNCA

   The Diameter NAPT Control Application

   Deployment dependent, the role of the Diameter NAT Control Manager can be fulfilled by
   either the NAS or by an external server server, such as
   an AAA-server.  The two
   deployment scenarios are outlined in Figure 3 ("integrated
   deployment") and Figure 4 ("autonomous deployment").

   Within the figures (M) denotes the network element element, which takes on
   the DNCA manager Manager role.  Similarly, (A) identifies the network element
   element, which performs the DNCA agent Agent role.

   The integrated deployment approach hides the existence of the NAT
   device from external servers servers, such as the AAA-server as much as
   possible.  It is suited for environments where minimal changes to the
   existing AAA deployment are desired.  The NAS, taking the role of the  As DNCA manager, is in charge of initiating and managing Manager the NAS,
   initiates and manages session to with the NAT device, exchanging exchanges NAT
   specific configuration information as
   well as handling and handles reporting and
   accounting information.  The NAS receives reporting and accounting
   information from NAT device.  This
   way  With this information, the NAS can provide for provides
   a single accounting record for the user,
   offloading user.  This reduces the usage of
   an external accounting systems from system for correlating accounting the information
   received from multiple sources.

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

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

          Figure 3: LSN Control deployment: Integrated deployment

   The autonomous deployment approach decouples user management on NAS
   and NAT device.  The AAA system performing the role of the DNCA
   manager
   Manager manages the connection to the NAT device, controls the per- per
   endpoint configuration, and also receives accounting and reporting
   information from the NAT device.  Different from the integrated
   deployment scenario, the autonomous deployment scenario does not
   "hide" the existence of the 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.
                     +---------+
                     |   (M)   |
                     |   AAA   |
                     |         |
                     +---------+
                          |
                          |
                          |
       +--------+    +---------+    +---------+    +----------+
       |  IPv4  |    |         |    |   (A)   |    |  IPv4    |
       |  Host  |----|   NAS   |----|   NAT   |----| Internet |
       |        |    |         |    |         |    |          |
       +--------+    +---------+    +---------+    +----------+
       <-------- Public  IPv6 ----------><---- Public IPv4 --->
       <-------- Private IPv4 ----------><---- Public IPv4 --->

          Figure 4: LSN Control deployment: Autonomous deployment

4.  Diameter NAT Control Application  DNCA Session Establishment and Management

   Note that this section forward references some of the commands and
   AVPs defined for the DNCA.  Please refer to Section 6 and Section 7
   for details.

4.1.  Parties Involved

   Authorization and control models supported by this application
   include the following parties:

   o  Diameter NAT Control Application (DNCA) agent:  DNCA Agent: The DNCA agent Agent is part of the Large scale Scale NAT (NAT) (LSN)
      device

   o  Diameter NAT Control Application (DNCA) manager  DNCA Manager

   The NAT control requesting entity is always the DNCA manager.
   Sessions will Manager.  The
   DNCA Manager always be initiated, updated, initiates, updates, or terminated by terminates the DNCA
   manager. sessions.
   This mode of operation is sometimes also referred to as "push mode".

   The DNCA manager Manager can be NAS or AAA Server. AAA-server.  The DNCA manager will initiate Manager
   initiates a session with the DNCA agent Agent when it learns about the
   subscriber.  The DNCA
   manager Manager may learn about a subscriber when it
   receives authentication,
   authorization authorization, or accounting request for
   that subscriber or by some other means means, such as on the box
   configuration to identify a subscriber
   w.r.t with respect to his IP
   packets.

4.2.  Session Establishment

   The DNCA manager Manager establishes a session to with the DNCA agent Agent to control
   the behavior of the NAT device.  During session establishment, the
   DNCA manager will pass Manager passes along configuration information to the DNCA
   agent.  Session
   Agent.  The session configuration information could for example comprise comprises the maximum
   number of bindings allowed for the endpoint associated with this
   session, a set of pre-defined NAT-bindings NAT bindings to be established for this
   endpoint, or a description of the address pool, external addresses should to
   be allocated from.

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

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

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

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

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

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

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

   o  If a DNCA agent Agent receives a NCR from a DNCA manager Manager with NC-
      Request-Type AVP set to INITIAL_REQUEST that identifies an already
      existing session (i.e. session; that is, DNCA manager Manager and endpoint identifier
      match an already existing session), session, the DNCA agent will return Agent returns NCA with
      Result-Code set to SESSION_EXISTS, and provides the Session-Id of
      the existing session in Duplicate-Session-Id AVP.

   o  If a DNCA agent Agent receives an NCR from a DNCA manager Manager with NC-
      Request-Type AVP set to INITIAL_REQUEST that matches more than one
      of the already existing sessions (i.e. sessions; that is, DNCA manager Manager and
      endpoint identifier match already existing sessions), sessions, the DNCA agent will
      return
      Agent returns a NCA with Result-Code set to Insufficient-Classifiers. Insufficient-
      Classifiers.  In case a DNCA manager Manager receives a NCA that reports Insufficient-
      Classifiers,
      Insufficient-Classifiers, it may choose to retry establishing a
      new session using additional/more additional or more specific classifiers.

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

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

   o  If DNCA agent Agent does not have sufficient resources to process a
      request, it will return returns NCA with Result-Code set to RESOURCE_FAILURE.

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

            DNCA Manager                             DNCA Agent
               |                                           |
               |                                           |
               |                                           |
            Trigger                                        |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               | (INITIAL_REQUEST, endpoint classifier,    |
               |     session id, NAT control config data)  |
               |                                           |
               |                                           |
               |                                  Create session state
               |                                           |
               |                                           |
               |                     NCA                   |
               |<------------------------------------------|
               |                 (result code)             |
               |                                           |
               |                                           |

      Figure 5: Initial NAT Control request and session establishment

4.3.  Session Re-Authorization

   Session re-authorization is performed if the DNCA manager Manager desires to
   change the behavior of the NAT device for an existing 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 Manager generates a NAT-Control Request (NCR) NC message to the DNCA agent Agent with NC-Request-Type NC-
   Request-Type AVP set to UPDATE_REQUEST upon receiving a trigger
   signal.  In case the session is updated successfully, the DNCA agent Agent
   notifies the DNCA manager Manager about 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 DNCA manager Manager and the DNCA agent. Agent.

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

   o  If DNCA agent Agent receives a NCR update/query update or query request for non-existent
      session a non-
      existent session, it will set error code sets Result-Code in answer, the answer to
      DIAMETER_UNKNOWN_SESSION_ID.

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

   o  If the DNCA agent Agent cannot establish the requested binding because
      the maximum number of allowed bindings has been reached for the
      Endpoint Classifier, it will return returns NCA with Result-Code AVP set to
      MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT.

   o  In case  If the DNCA agent Agent 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 will return returns a NCA with Result-Code Result-
      Code set to BINDING_FAILURE.  The DNCA agent (i.e.
      NAT) Agent (i.e., NAT device)
      treats a NCR as an atomic operation; hence operation.  Hence none of the requested
      bindings will be established by NAT. NAT device.  Either all requested
      actions within a NCR are completed successfully, either successful or the
      entire request fails. failed completely..

   o  If DNCA agent Agent does not have sufficient resources to process a
      request, it will return a returns NCA with Result-Code set to RESOURCE_FAILURE.

   o  If a NCR redefines the maximum number of NAT bindings allowed for
      the endpoint, the new value will override any previously defined
      limit on NAT-bindings. NAT bindings.  It depends on the implementation of the
      NAT device on how the NAT would cope device copes with a case where the new
      value is lower than the actual number of allocated bindings.
      Typically the NAT
      would refrain device refrains from enforcing the new limit immediately (i.e.
      immediately; that is, actively remove bindings) 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 the DNCA
      agent,
      Agent, the binding rule will override overrides any previously defined rules for
      the session.

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

            DNCA Manager                             DNCA Agent
               |                                           |
               |                                           |
               |                                           |
        Change of session                                  |
           attributes                                      |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               |       (UPDATE_REQUEST session id,         |
               |         NAT control config data)          |
               |                                           |
               |                                           |
               |                                  Update session state
               |                                           |
               |                                           |
               |                     NCA                   |
               |<------------------------------------------|
               |                 (result code)             |
               |                                           |
               |                                           |

             Figure 6: NAT Control request for session update

4.4.  Session And and Binding Query

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

   The DNCA manager Manager initiates a session query by sending a NAT-Control
   Request (NCR) NCR message
   to the DNCA agent Agent with NC-Request-Type AVP set to QUERY_REQUEST.
   Figure 7 shows the protocol interaction between the DNCA manager Manager and
   the DNCA agent. Agent.

   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 Manager retrieve the current set of bindings for a specific
   session.  The second type of query request is used in to retrieve the
   session identifiers, along with the associated bindings, matching a
   criteria.  This enables the DNCA manager Manager to find out the sessions, which sessions
   utilize a specific external IP address.

   1.  Request a list of currently allocated NAT-bindings NAT bindings for a
       particular session: The DNCA agent will, Agent on receipt of the receiving NCR,
       lookup the looks up
       session information for the session id ID contained in the NCR, and will report
       reports all currently active NAT-bindings NAT bindings for the session using a NAT-Control Answer (NCA)
       NCA message with Result-
       Code Result-Code set to DIAMETER_SUCCESS.  In this
       case the NCR MUST NOT contain a NAT-Control-Definition AVP.  Each NAT-Binding will be
       NAT binding is reported in a NAT-Control-Definition AVP.  In case
       the session id ID is unknown to unknown, the DNCA agent a DIAMETER_UNKNOWN_SESSION_ID error
       is returned. Agent returns NCA with
       Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.

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

            DNCA Manager                             DNCA Agent
               |                                           |
               |                                           |
               |                                           |
     DNCA Session Established                              |
               |                                           |
               |                   NCR                     |
               |------------------------------------------>|
               |              (QUERY_REQUEST)              |
               |                                           |
               |                                           |
               |                                           |
               |                          Look up corresponding session
               |                            and associated NAT Bindings
               |                                           |
               |                     NCA                   |
               |<------------------------------------------|
               |                 (result code)             |
               |                                           |
               |                                           |

                          Figure 7: Session Query

4.5.  Session Termination

   The DNCA manager Manager generates a NAT-Control Request (NCR) message to the
   DNCA agent Agent with NC-Request-Type AVP set to TERMINATE_REQUEST upon
   receiving a trigger signal.  The DNCA agent Agent sends accounting stop
   record reporting all the bindings and notifies the DNCA manager Manager about
   successful session termination using a NAT-Control Answer (NCA)
   message with Result-Code set to DIAMETER_SUCCESS.  Figure 8 shows the
   protocol interaction between the DNCA manager Manager and the DNCA agent. Agent.

   If a DNCA agent Agent receives a NCR from a DNCA manager Manager with NC-Request-
   Type AVP set to TERMINATE_REQUEST and fails to find a matching
   session, the DNCA agent Agent returns DIAMETER_UNKNOWN_SESSION_ID error. NCA with Result-Code set to
   DIAMETER_UNKNOWN_SESSION_ID.
            DNCA Manager                             DNCA Agent
               |                                            |
               |                                            |
            Trigger                                         |
               |                                            |
               |                   NCR                      |
               |------------------------------------------->|
               |       (TERMINATE_REQUEST, session id)      |
               |                                            |
               |                                            |
               |                                  Remove NAT bindings
               |                                       of session
               |                                            |
               |                                            |
               |           Send accounting stop             |
               |<-------------------------------------------|
               |           for all session bindings         |
               |                                            |
               |                                  Terminate Session /
               |                                 Remove session state
               |                                            |
               |                                            |
               |                                            |
               |                     NCA                    |
               |<-------------------------------------------|
               |                 (result code)              |
               |                                            |

                  Figure 8: Terminate NAT Control session

4.6.  DNCA Manager/Agent Manager and Agent Failures

   This document does not cover details in case DNCA manager Manager and DNCA
   agent go
   Agent are out of sync, which could happen for example due to sync.  This happens when the DNCA
   manager Manager or DNCA agent
   Agent restart, (temporary) loss of network connectivity etc.  The
   DNCA application will rely relies on DNCA Manager and DNCA Agent to have builtin redundancy
   support to recover state in case of failure.

   Example failure cases include the following:

   o  The DNCA manager Manager loses session state (e.g. due to a restart).  In
      this case,

      *  the  The DNCA agent Agent may receive a NCR with NC-Request-Type AVP set
         to INITIAL_REQUEST that matches an existing session of DNCA
         agent.
         Agent.  The DNCA agent will return Agent returns an error that contains
         Duplicate-Session-Id AVP to report Session-Id the Session-ID of existing
         session.  The DNCA manager Manager may then send an explicit
         TERMINATE_REQUEST for the older session that session, which was lost.

      *  the  The DNCA manager Manager may receive accounting records for a session
         that does not exist.  The DNCA manager will send Manager sends an accounting
         answer with error-code Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.  On
         receipt of which
         receiving this, the DNCA agent Agent clears the session and removes
         the associated session state.

   o  The DNCA agent Agent loses session state.  In such a case, the DNCA
      agent could
      Agent may receive a NCR with NC-Request-Type AVP set to
      UPDATE_REQUEST for a non-existent session.  The DNCA agent will
      return Agent returns
      NCA with error code Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.
      State recovery procedures of the DNCA agent will be covered in a
      future version of this document.

   o  The DNCA manager Manager is unreachable (as e.g. unreachable, for example detected by Diameter
      watchdog)
      watchdog, or down and accounting requests request from the DNCA agent fail Agent fails
      to get a response.  The mechanism to ensure that a DNCA manager Manager no
      longer has associated state for a session being cleared at the by a DNCA agent
      Agent is beyond the scope of this document.

   o  The DNCA agent Agent 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 could, for
      example, can choose
      to terminate the access session to the endpoint.

5.  Use Of The Diameter Base Protocol

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

5.1.  Securing Diameter Messages

   For secure transport of Diameter messages, IPSec MAY be used.

   The DNCA agent Agent MAY verify the identity of the DNCA Manager during the
   Capabilities Exchange Request procedure.

   The DNCA agent Agent MAY verify if the DNCA Manager that issues a NCR
   command is allowed to do so, and it is based on:

   o  The Identity identity of the DNCA Manager

   o  The Type 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, (accounting session state machine, related
   command codes and AVPs) is defined in Section 8 below.

5.3.  Use Of Sessions

   Each DNCA session MUST have a globally unique Session-Id Session-ID as defined
   in [RFC3588], which MUST NOT be changed during the lifetime of a DNCA
   session.  The Diameter Session-Id Session-ID serves as the global endpoint
   identifier.  The DNCA agent Agent and DNCA manager Manager maintain state
   associated with the Session-Id. Session-ID.  This globally unique Session-Id Session-ID is
   used for updating, accounting for accounting, and terminating the session.  The DNCA
   session MUST NOT have more than one outstanding request at any given
   instant.  The DNCA agent Agent 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 Manager knows the DiameterIdentity of the
   DNCA agent Agent for a given endpoint.  Both the Destination-Realm and
   Destination-Host AVPs are present in the Request request from the DNCA
   manager
   Manager to the DNCA agent. Agent.

5.5.  Advertising Application Support

   Diameter applications conforming to this specification MUST advertise
   support by including the value of TBD in:

   o  Auth-Application-Id and Acct-Application-Id of Capabilities-
      Exchange-Request (CER)

   o  Auth-Application-Id of NC-request (NCR), NC-Answer (NCA), Abort-
      Session-Request(ASR), Abort-Session-Answer (AAA) messages

   o  Acct-Application-Id in Accounting-Request (ACR) and Accounting-
      Answer (AAA) messages.

6.  Diameter NAT Control Application  DNCA Commands

   The following commands are used to establish, maintain and clear 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 Manager to the DNCA agent Agent in order to install 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.

   Message 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 ]
                       [ Auth-Session-State ]
                     * [ NAT-Control-Remove ]
                     * [ 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 Agent in response to NAT-Control-Request command.

   Message Format:

      <NC-Answer> ::= < Diameter Header: TBD, PXY >
                      < Session-Id >
                      { Origin-Host }
                      { Origin-Realm }
                      { NC-Request-Type }
                      [ Result-Code ]
                    * [ 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.  Diameter NAT Control Application  DNCA AVPs

7.1.  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    |
   |Auth-Session-State         277      Enumerated | 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: 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.

7.2.  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.

7.2.1.  Success

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

7.2.2.  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 Agent indicates that the binding could not be
         installed or a new session could not be created due to resource
         shortage.

7.2.3.  Permanent Failures

   The Result-Code AVP values that 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 Agent indicates that the binding could not be
         installed or a new session could not be created due to resource
         shortage.

      BINDING_FAILURE (TBD)

         The DNCA indicates that the requested binding(s) could not be
         installed.

      MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT (TBD)

         The DNCA agent Agent denies the request because the maximum number of
         allowed bindings has been reached for the specified Endpoint
         Classifier.

      SESSION_EXISTS (TBD)

         The DNCA agent Agent denies request to initialize a new session, if
         it already has a DNCA session that uses the same set of
         classifiers as indicated by DNCA manager Manager in the new session
         init request.
         initializationrequest.

      INSUFFICIENT_CLASSIFIERS (TBD)

         The DNCA agent Agent defines request to initialize a new session, if
         the classifiers in the request match more than one of the
         existing sessions on DNCA agent. Agent.

7.3.  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             |      |            |    |     |    |     |    |
   | Framed-IPv6-     |  97  | OctetString| M  |  P  |    |  V  | Y  |
   |  Prefix          |      |            |    |     |    |     |    |
   +------------------+------+------------|----+-----+----+-----|----+

            Figure 10: Reused NASREQ Diameter application AVPs

7.4.  Reused 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: Reused attributes from RFC 4675

7.5.  Reused from Diameter QoS Application

   The following AVPs are reused from the Diameter QoS Application
   [I-D.ietf-dime-diameter-qos].
                                                   +-------------------+
                                                   |  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: Reused QoS-attributes

7.6.  Reused From 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) (13019).                        |
   +-------------------------------------------------------------------+

            Figure 13: Reused AVPs from Diameter e4 application

7.7.  Diameter NAT Control Application  DNCA Defined AVPs

   The following table describes the new Diameter AVPs used in the
   present document, their AVP Code values, types, possible flag values
   and whether the AVP may or not be encrypted. this
   document.
                                                   +-------------------+
                                                   |  AVP Flag rules   |
   +-----------------------------------------------|-----+---+---------+
   |                       AVP  Section            |     |   |   May   |
   | Attribute Name        Code Defined Data Type  |MUST |MAY| encrypt |
   +-----------------------------------------------+-----+---+---------+
   |NC-Request-Type        TBD  7.7.1   Enumerated | M   | P |    Y    |
   |NAT-Control-Install    TBD  7.7.2   Grouped    | M   | P |    Y    |
   |NAT-Control-Remove     TBD  7.7.3   Grouped    | M   | P |    Y    |
   |NAT-Control-Definition TBD  7.7.4   Grouped    | M   | P |    Y    |
   |NAT-Internal-Address   TBD  7.7.5   Grouped    | M   | P |    Y    |
   |NAT-External-Address   TBD  7.7.6   Grouped    | M   | P |    Y    |
   |Max-NAT-Bindings       TBD  7.7.7   Unsigned32 | M   | P |    Y    |
   |NAT-Control-           TBD  7.7.8   OctetString| M   | P |    Y    |
   | Binding-Rule                                  |     |   |         |
   |Duplicate-             TBD  7.7.9   UTF8String | M   | P |    Y    |
   | Session-ID                                    |     |   |         |
   |NAT-Control-Record     TBD  8.2.1   Grouped    | M   | P |    Y    |
   |NAT-Control-           TBD  8.2.2   Enumerated | M   | P |    Y    |
   | Binding-Status                                |     |   |         |
   |Current-NAT-Bindings   TBD  8.2.3   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 header.                  |
   +-------------------------------------------------------------------+

                       Figure 14: New Diameter AVPs

7.7.1.  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 the DNCA agent Agent
         on a successful access session setup.

      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.

      TERMINATION_REQUEST (3)

         Termination Request is used to deactivate and remove all
         bindings previously activated on a given access session.

      QUERY_REQUEST (4)

         Query Request is used to query the DNCA agent Agent about the
         currently installed bindings for an endpoint classifier.

7.7.2.  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 maximum number of NAT bindings to be allowed
   for a subscriber and NAT-Control-Binding-Rule that references
   predefined policy template on DNCA agent Agent that may contain static
   bindings, maximum number of bindings to be allowed, address pool from
   which external binding address should be allocated.

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

7.7.3.  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.

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

7.7.4.  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 Agent and the DNCA manager. Manager.

   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 which the
   binding is created.  Exactly binding.
   The NAT-Control-Definition AVP can contain either zero or one
   Protocol AVP may be
   contained within NAT-Control-Definition AVP.  If the Protocol AVP is omitted and if both internal
   and external address are specified then the binding reserves the
   addresses for all transport protocols.

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

7.7.5.  NAT-Internal-Address AVP

   The NAT-Internal-Address AVP (AVP code TBD) is of type Grouped, and
   it Grouped.  It
   describes the internal 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 ]

7.7.6.  NAT-External-Address AVP

   The NAT-External-Address AVP (AVP code TBD) is of type Grouped, and
   it describes the external IP address and port for a binding.  IP-
   Address-Mask AVP can only be specified when Framed-IP-Address AVP is
   present.

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

7.7.7.  Max-NAT-Bindings

   The Max-NAT-Bindings AVP (AVP code TBD) is of type Unsigned32, and it Unsigned32.  It
   indicates the maximum number of NAT bindings allowed.

7.7.8.  NAT-Control-Binding-Rule AVP

   The NAT-Control-Binding-Rule AVP (AVP code TBD) is of type is of type
   OctetString, and it
   OctetString.  It defines a name for a policy template that will be
   predefined at NAT.  Details on the contents and structure of the
   template as well as how it would be configured and configuration are outside the scope of this document.
   The policy to which this AVP refers to may contain NAT Bindings, bindings,
   address pool for external address allocation of NAT binding, and
   maximum allowed NAT bindings etc. bindings.

7.7.9.  Duplicate-Session-Id AVP

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

8.  Accounting Commands

   The Diameter NAT Control Application DNCA reuses session based accounting as defined in Diameter Base Protocol [RFC3588]
   Protocol,[RFC3588] to report the bindings
   used per endpoint.  This
   reporting is achieved by sending Diameter Accounting Requests (ACR)
   [Start, Interim and Stop] from the DNCA
   agent Agent to DNCA manager. Manager.

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

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

   The DNCA agent Agent may trigger an interim accounting record when maximum
   number of bindings, if received in NCR, is reached.

8.1.  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 Agent and the CDF. DNCA Manager.  The DNCA Application ID is
   used in the accounting commands.  ACR will contain contains one or more optional NAT-
   Control-Record
   NAT-Control-Record AVP to report the bindings.  The DNCA agent Agent
   indicates the number of the currently allocated NAT bindings to the DNCA
   manager Manager
   using the Current-NAT-Bindings AVP.  This number needs to match the
   number of bindings identified as active within the NAT-
   Control-Record NAT-Control-Record
   AVP.

8.2.  NAT Control Accounting AVPs

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

8.2.1.  NAT-Control-Record

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

8.2.2.  NAT-Control-Binding-Status

   The NAT-Control-Binding-Status AVP (AVP code TBD) is of type
   enumerated and it describes whether
   enumerated.  It indicates the status of the binding being reported was
   created or removed - created,
   removed, or simply indicates that it is active.

   The following values are defined:

      Created (1)

         Indicates that

         NAT binding is created.

      Active (2)

         Indicates that

         NAT binding is active.

      Removed (3)

         Indicates that the

         NAT binding was removed.

8.2.3.  Current-NAT-Bindings

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

9.  AVP Occurrence Table

   The following sections presents the AVPs defined in this document and
   specifies in which the Diameter messages in which, they MAY be present.  Note that  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.

9.1.  DNCA AVP Table for NAT control initial Control Initial and update requests Update Requests

   The following table presents which NAT control application lists the DNCA specific AVPs are that have to be
   present in NCR/NCA 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       |
   |NAT-Control-Record                      0      0       |
   |Current-NAT-Bindings                    0      0       |
   |Duplicate-Session-Id                    0      0-1     |
   +-------------------------------------------------------+

9.2.  DNCA AVP Table for Session Query request

   The following table presents which NAT control application lists the DNCA specific AVPs are that have to be
   present in NCR/NCA 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+      |
   |NAT-Control-Record                      0      0       |
   |Current-NAT-Bindings                    0      1       |
   |Duplicate-Session-Id                    0      0       |
   +-------------------------------------------------------+

9.3.  DNCA AVP Table for NAT Control Terminate requests

   The following table presents which NAT control application lists the DNCA specific AVPs are that have to be
   present in NCR/NCA NCR and NCA with NC-Request-Type set to
   TERMINATION_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       |
   |NAT-Control-Record                      0      0       |
   |Current-NAT-Bindings                    0      0       |
   |Duplicate-Session-Id                    0      0       |
   +-------------------------------------------------------+

9.4.  DNCA AVP Table For for Accounting Message

   Following

   The following table presents which NAT control application lists the DNCA specific AVPs
   May AVPs, which may or May Not may
   not be present in ACR/ACA ACR and ACA messages.
                                       +-------------------+
                                       |  Command Code     |
   +-----------------------------------+-------------------+
   | Attribute Name                        ACR    ACA      |
   +-------------------------------------------------------+
   |NC-Request-Type                         0      0       |
   |NAT-Control-Install                     0      0       |
   |NAT-Control-Remove                      0      0       |
   |NAT-Control-Definition                  0      0       |
   |NAT-Control-Record                      0+     0       |
   |Current-NAT-Bindings                    1      0       |
   |Duplicate-Session-Id                    0      0       |
   +-------------------------------------------------------+

10.  IANA Considerations

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

10.1.  Command Codes

   IANA is requested to allocate command code values for the following.

   Registry:

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

                          Table 1: Command codes

10.2.  AVP Codes

   IANA is requested to allocate AVP codes for the following AVPs that
   are defined in this document.

   Registry:

         +----------------+----------------------------+---------------+
         | Code Value     | Name                       | Reference     |
         +----------------+----------------------------+---------------+
         | to be assigned | NC-Request-Type            | Section 7.7.1 |
         | to be assigned | NAT-Control-Install        | Section 7.7.2 |
         | to be assigned | NAT-Control-Remove         | Section 7.7.3 |
         | to be assigned | NAT-Control-Definition     | Section 7.7.4 |
         | to be assigned | NAT-Internal-Address       | Section 7.7.5 |
         | to be assigned | NAT-External-Address       | Section 7.7.6 |
         | to be assigned | Max-NAT-Bindings           | Section 7.7.7 |
         | to be assigned | NAT-Control-Binding-Rule   | Section 7.7.8 |
         | to be assigned | Duplicate-Session-Id       | Section 7.7.9 |
         | to be assigned | NAT-Control-Record         | Section 8.2.1 |
         | to be assigned | NAT-Control-Binding-Status | Section 8.2.2 |
         | to be assigned | Current-NAT-Bindings       | Section 8.2.3 |
         +----------------+----------------------------+---------------+

                            Table 2: AVP codes

10.3.  AVP Values

10.3.1.  Result-Code AVP Values

   Section 7.2 defines several new values for the Result-Code AVP for
   transient failures and permanent failures.  IANA is requested to allocate the
   corresponding values from the ranges for transient (4xxx) and
   permantent (5xxx) failures.

   +-----------+---------------------------------------+---------------+
   | Code      | Name                                  | Reference     |
   | Value     |                                       |               |
   +-----------+---------------------------------------+---------------+
   | to be     | RESOURCE_FAILURE                      | Section 7.2.2 |
   | assigned  |                                       |               |
   | (4xxx)    |                                       |               |
   | to be     | UNKNOWN_BINDING_RULE_NAME             | Section 7.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | BINDING_FAILURE                       | Section 7.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT | Section 7.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | SESSION_EXISTS                        | Section 7.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   | to be     | INSUFFICIENT_CLASSIFIERS              | Section 7.2.3 |
   | assigned  |                                       |               |
   | (5xxx)    |                                       |               |
   +-----------+---------------------------------------+---------------+

                      Table 3: Result Code AVP Values

10.4.  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 values

11.  Security Considerations

   Similar to what the impact of Diameter QoS application (see
   [I-D.ietf-dime-diameter-qos]) does for on authorization of QoS reservations,
   this document describes procedures for authorizing
   network address translation NAT related
   attributes and parameters by an
   entity entity, which is non-local to the
   device performing network address
   translation. NAT.  The security considerations for the Diameter
   QoS application (see [I-D.ietf-dime-diameter-qos] section 11) apply
   in a similar way to the DNCA.  Securing the information exchange
   between the authorizing entity (the DNCA manager) as well as Manager) and the NAT device
   requires bilateral authentication of the involved parties,
   authorization of the involved parties to perform the required
   procedures and functions, as well as and procedures to ensure integrity and
   confidentiality of the information exchange.  The DNCA makes use of
   the capabilities offered by Diameter as well as and the underlying transport
   protocols to deliver on these requirements (see Section 5.1 ).

   It is assumed that the DNCA agent Agent and DNCA manager Manager are in the same
   domain and have a mutual trust set up.  Authorization between the
   DNCA agent Agent and DNCA manager Manager is beyond the scope of this document.

12.  Acknowledgements

   The authors would like to thank Ramya Balakrishna, Jouni Korhonen,
   Avi Lior, Chris Metz, Hannes Tschofenig, Greg Weber, and Glen Zorn
   for their input on this document.

13.  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 (shorted intro section
   e.  added support for bindings providing AFT (NAT64)

   Changes from -02 to -03

   a.  Editorial changes

14.  References

14.1.  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.

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

   [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.

14.2.  Informative References

   [I-D.ietf-dime-diameter-qos]
              Sun, D., McCann, P., Tschofenig, H., ZOU), T., Doria, A.,
              and G. Zorn, "Diameter Quality of Service Application",
              draft-ietf-dime-diameter-qos-14 (work in progress),
              February 2010.

   [I-D.narten-iana-considerations-rfc2434bis]
              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs",
              draft-narten-iana-considerations-rfc2434bis-09 (work in
              progress), March 2008.

   [I-D.nishitani-cgn]
              Nishitani, T., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common Functions of Large Scale NAT
              (LSN)", draft-nishitani-cgn-03 (work in progress),
              November 2009.

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

   [RFC5624]  Korhonen, J., Tschofenig, H., and E. Davies, "Quality of
              Service Parameters for Usage with Diameter", RFC 5624,
              August 2009.

   [TS32299]  "3rd Generation Partnership Project; Technical
              Specification Group Service and System Aspects;
              Telecommunication management; Charging management;
              "Diameter charging applications", 3GPP TS 32.299 Version
              6.3.0.2",
              9.4.0", 2008.

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
   Mavenir Systems
   Sharda Towers, 56/13 Nandidurga Road
   Bangalore 560046
   India

   Email: vaneeta@mavenir.com
   Victor Fajardo
   Telcordia Technologies
   1 Telcordia Drive #1S-222
   Piscataway, NJ 08854
   USA

   Email: vf0213@gmail.com