Network Working Group                                       S. Perreault
Internet-Draft                                       Jive Communications
Intended status: Standards Track                                 T. Tsou
Expires: September 25, November 26, 2015                           Huawei Technologies
                                                            S. Sivakumar
                                                           Cisco Systems
                                                               T. Taylor
                                                    PT Taylor Consulting
                                                          March 24,
                                                            May 25, 2015

  Definitions of Managed Objects for Network Address Translators (NAT)
                   draft-perrault-behave-natv2-mib-03
                   draft-perrault-behave-natv2-mib-04

Abstract

   This memo defines a portion of the Management Information Base (MIB)
   for devices implementing the Network Address Translator (NAT)
   function.  The new MIB module defined in this document, NATV2-MIB, is
   intended to replace module NAT-MIB (RFC 4008).  NATV2-MIB is not
   backwards compatible with NAT-MIB, for reasons given in the text of
   this document.  A companion document deprecates all objects in NAT-
   MIB.  NATV2-MIB can be used for monitoring of NAT instances on a
   device capable of NAT function.  Compliance levels are defined for
   three application scenarios: basic NAT, pooled NAT, and carrier-grade
   NAT (CGN).

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 25, November 26, 2015.

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Table of Contents

   1.  The SNMP Management Framework . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Content Provided by the NATV2-MIB Module  . . . . . . . .   5
       3.1.1.  Configuration Data  . . . . . . . . . . . . . . . . .   5
       3.1.2.  Notifications . . . . . . . . . . . . . . . . . . . .   6
       3.1.3.  State Information . . . . . . . . . . . . . . . . . .   9
       3.1.4.  Statistics  . . . . . . . . . . . . . . . . . . . . .   9
     3.2.  Outline of MIB Module Organization  . . . . . . . . . . .  11
     3.3.  Detailed MIB Module Walk-Through  . . . . . . . . . . . .  13
       3.3.1.  Textual Conventions . . . . . . . . . . . . . . . . .  13
       3.3.2.  Notifications . . . . . . . . . . . . . . . . . . . .  13
       3.3.3.  The Subscriber Table: natv2SubscriberTable  . . . . .  13
       3.3.4.  The Instance Table: natv2InstanceTable  . . . . . . .  14
       3.3.5.  The Protocol Table: natv2ProtocolTable  . . . . . . .  15
       3.3.6.  The Address Pool Table: natv2PoolTable  . . . . . . .  15
       3.3.7.  The Address Pool Address Range Table:
               natv2PoolRangeTable . . . . . . . . . . . . . . . . .  16
       3.3.8.  The Address Map Table: natv2AddressMapTable . . . . .  16
       3.3.9.  The Port Map Table: natv2PortMapTable . . . . . . . .  17
     3.4.  Conformance: Three Application Scenarios  . . . . . . . .  17
   4.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .  18
   5.  Operational and Management Considerations . . . . . . . . . .  74
     5.1.  Configuration Requirements  . . . . . . . . . . . . . . .  74
     5.2.  Transition From and Coexistence With NAT-MIB  [RFC 4008]   76
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  78
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  80
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  81  80
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  81  80
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  82  81
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  82

1.  The SNMP Management Framework

   For a detailed overview of the documents that describe the current
   Internet-Standard Management Framework, please refer to section 7 of
   RFC 3410 [RFC3410].

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  MIB objects are generally
   accessed through the Simple Network Management Protocol (SNMP).
   Objects in the MIB are defined using the mechanisms defined in the
   Structure of Management Information (SMI).  This memo specifies a MIB
   module that is compliant to the SMIv2, which is described in STD 58,
   [RFC2578], [RFC2579] and [RFC2580].

2.  Introduction

   Note to RFC Ed.: please replace RFC yyyy with actual RFC number
   throughout this document and remove this note.

   This memo defines a portion of the Management Information Base (MIB)
   for devices implementing NAT functions.  This MIB module, NATV2-MIB,
   may be used for monitoring of such devices.  NATV2-MIB supersedes
   NAT-MIB [RFC4008], which did not fit well with existing NAT
   implementations, and hence was not itself much implemented.
   [I-D.perrault-behave-deprecate-nat-mib-v1] provides a detailed
   analysis of the deficiencies of NAT-MIB.

   Relative to [RFC4008] and based on the analysis just mentioned, the
   present document introduces the following changes:

   o  removed all writable configuration except that related to control
      of the generation of notifications and the setting of quotas on
      the use of NAT resources;

   o  minimized the read-only exposure of configuration to what is
      needed to provide context for the state and statistical
      information presented by the MIB module;

   o  removed the association between mapping and interfaces, retaining
      only the mapping aspect;

   o  replaced references to NAT types with references to NAT behaviors
      as specified in [RFC4787];

   o  replaced a module-specific enumeration of protocols with the
      standard protocol numbers provided by the IANA Assigned Internet
      Protocol Numbers registry.

   This MIB module adds the following features not present in [RFC4008]:

   o  additional writable protective limits on NAT state data;

   o  additional objects to report state, statistics, and notifications;

   o  support for the carrier grade NAT (CGN) application, including
      subscriber-awareness, support for an arbitrary number of address
      realms, and support for multiple NAT instances running on a single
      device;

   o  expanded support for address pools;

   o  revised indexing of port map entries to simplify traceback from
      externally observable packet parameters to the corresponding
      internal endpoint.

   These features are described in more detail below.

   The remainder of this document is organized as follows:

   o  Section 3 provides a verbal description of the content and
      organization of the MIB module.

   o  Section 4 provides the MIB module definition.

   o  Section 5 discusses operational and management issues relating to
      the deployment of NATV2-MIB.  One of these issues is NAT
      management when both NAT-MIB [RFC4008] and NATV2-MIB are deployed.

   o  Section 6 and Section 7 provide a security discussion and a
      request to IANA for allocation of an object identifier for the
      module in the mib-2 tree, respectively.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   This document uses the following terminology:

   Upper layer protocol:  The protocol following the outer IP header of
      a packet.  This follows the terminology of [RFC2460], but as that
      document points out, "upper" is not necessarily a correct
      description of the protocol relationships (e.g., where IP is
      encapsulated in IP).  The abbreviated term "protocol" will often
      be used where it is unambiguous.

   Trigger:  With respect to notifications, the logical recognition of
      the event that the notification is intended to report.

   Report:  The actual production of a notification message.  Reporting
      can happen later than triggering, or may never happen for a given
      notification instance, because of the operation of notification
      rate controls.

   Address realm:  A network domain in which the network addresses are
      uniquely assigned to entities such that datagrams can be routed to
      them.  (Definition taken from [RFC2663] Section 2.1.)  The
      abbreviated term "realm" will often be used.

3.  Overview

   This section provides a prose description of the contents and
   organization of the NATV2-MIB module.

3.1.  Content Provided by the NATV2-MIB Module

   The content provided by the NATV2-MIB module can be classed under
   four headings: configuration data, notifications, state information,
   and statistics.

3.1.1.  Configuration Data

   As mentioned above, the intent in designing the NATV2-MIB module was
   to minimize the amount of configuration data presented to that needed
   to give a context for interpreting the other types of information
   provided.  Detailed descriptions of the configuration data are
   included with the descriptions of the individual tables.  In general,
   that data is limited to what is needed for indexing and cross-
   referencing between tables.  The two exceptions are the objects
   describing NAT instance behavior in the NAT instance table, and the
   detailed enumeration of resources allocated to each address pool in
   the pool table and its extension.

   The NATV2-MIB module provides three sets of read-write objects,
   specifically related to other aspects of the module content.  The
   first set controls the rate at which specific notifications are
   generated.  The second set provides thresholds used to trigger the
   notifications.  These objects are listed in Section 3.1.2.

   A third set of read-write objects sets limits on resource consumption
   per NAT instance and per subscriber.  When these limits are reached,
   packets requiring further consumption of the given resource are
   dropped rather than translated.  Statistics described in
   Section 3.1.4 record the numbers of packets so dropped.  Limits are
   provided for:

   o  total number of address map entries over the NAT instance.  Limit
      is set by object natv2InstanceLimitAddressMapEntries in table
      natv2InstanceTable.  Dropped packets are counted in
      natv2InstanceAddressMapEntryLimitDrops in that table.

   o  total number of port map entries over the NAT instance.  Limit is
      set by object natv2InstanceLimitPortMapEntries in table
      natv2InstanceTable.  Dropped packets are counted in
      natv2InstancePortMapEntryLimitDrops in that table.

   o  total number of held fragments (applicable only when the NAT
      instance can receive fragments out of order; see [RFC4787]
      Section 11).  Limit is set by object
      natv2InstanceLimitPendingFragments in table natv2InstanceTable.
      Dropped packets are counted by natv2InstanceFragmentDrops in the
      same table.

   o  total number of active subscribers (i.e., subscribers having at
      least one mapping table entry) over the NAT instance.  Limit is
      set by object natv2InstanceLimitSubscriberActives in table
      natv2InstanceTable.  Dropped packets are counted by
      natv2InstanceSubscriberActiveLimitDrops in the same table.

   o  number of port map entries for an individual subscriber.  Limit is
      set by object natv2SubscriberLimitPortMapEntries in table
      natv2SubscriberTable.  Dropped packets are counted by
      natv2SubscriberPortMapFailureDrops in the same table.  Note that,
      unlike in the instance table, the per-subscriber count is lumped
      in with the count of packets dropped because of failures to
      allocate a port map entry for other reasons to save on storage.

3.1.2.  Notifications

   NATV2-MIB provides five notifications, intended to provide warning of
   the need to provision or reallocate NAT resources.  As indicated in
   the previous section, each notification is associated with two read-
   write objects: a control on the rate at which that notification is
   generated, and a threshold value used to trigger the notification in
   the first place.  The default setting within the MIB module
   specification is that all notifications are disabled.  The setting of
   threshold values is discussed in Section 5.

   The five notifications are as follows:

   o  Two notifications relate to the management of address pools.  One
      indicates that usage equals or exceeds an upper threshold, and is
      therefore a warning that the pool may be over-utilized unless more
      addresses are assigned to it.  The other notification indicates
      that usage equals or has fallen below a lower threshold,
      suggesting that some addresses allocated to that pool could be
      reallocated to other pools.  Address pool usage is calculated as
      the percentage of the total number of ports allocated to the
      address pool that are already in use, for the most-mapped protocol
      at the time the notification is generated.  The notifications
      identify that protocol and report the number of port map entries
      for that protocol in the given address pool at the moment the
      notification was triggered.

   o  Two notifications relate to the number of address and port map
      entries respectively, in total over the whole NAT instance.  In
      both cases the threshold that triggers the notification is an
      upper threshold.  The notifications return the number of mapping
      entries of the given type, plus a cumulative counter of the number
      of entries created in that mapping table at the moment the
      notification was triggered.  The intent is that the notifications
      provide a warning that the total number of address or port map
      entries is approaching the configured limit.

   o  The final notification is generated on a per-subscriber basis when
      the number of port map entries for that subscriber crosses the
      associated threshold.  The objects returned by this notification
      are similar to those returned for the instance-level mapping
      notifications.  This notification is a warning that the number of
      port map entries for the subscriber is approaching the configured
      limit for that subscriber.

   Here is a detailed specification of the notifications.  A given
   notification can be disabled by setting the threshold to 0 (default),
   with the exception noted below.

   Notification: natv2NotificationPoolUsageLow.  Indicates that address
   pool usage for the most-mapped protocol equals or is less than the
   threshold value.

   Compared value:  natv2PoolNotifiedPortMapEntries as a percentage of
      total available ports in the pool.

   Threshold:  natv2PoolThresholdUsageLow in natv2PoolTable.  To allow
      for a threshold of zero usage, disabling of the
      natv2NotificationPoolUsageLow is done by setting
      natv2PoolThresholdUsageLow to -1 rather than 0, in contrast to all
      of the other notifications.

   Objects returned:  natv2PoolNotifiedPortMapEntries and
      natv2PoolNotifiedPortMapProtocol in natv2PoolTable;

   Rate control:  natv2PoolNotificationInterval in
      natv2PoolTable (default 20 seconds between notifications for a
      given address pool). natv2PoolTable.

   Notification: natv2NotificationPoolUsageHigh.  Indicates that address
   pool usage for the most-mapped protocol has risen to the threshold
   value or more.

   Compared value:  natv2PoolNotifiedPortMapEntries as a percentage of
      total available ports in the pool.

   Threshold:  natv2PoolThresholdUsageHigh in natv2PoolTable;

   Objects returned:  natv2PoolNotifiedPortMapEntries,
      natv2PoolNotifiedPortMapProtocol in natv2PoolTable;

   Rate control:  natv2PoolNotificationInterval in
      natv2PoolTable (default 20 seconds between notifications for a
      given address pool). natv2PoolTable.

   Notification: natv2NotificationInstanceAddressMapEntriesHigh.
   Indicates that the total number of entries in the address map table
   over the whole NAT instance equals or exceeds the threshold value.

   Compared value:  natv2InstanceAddressMapEntries in
      natv2InstanceTable;

   Threshold:  natv2InstanceThresholdAddressMapEntriesHigh in
      natv2InstanceTable;

   Objects returned:  natv2InstanceAddressMapEntries,
      natv2InstanceAddressMapCreations in natv2InstanceTable;

   Rate control:  natv2InstanceNotificationInterval in
      natv2InstanceTable (default 10 seconds between notifications for a
      given NAT instance).
      natv2InstanceTable.

   Notification: natv2NotificationInstancePortMapEntriesHigh.  Indicates
   that the total number of entries in the port map table over the whole
   NAT instance equals or exceeds the threshold value.

   Compared value:  natv2InstancePortMapEntries in natv2InstanceTable;

   Threshold:  natv2InstanceThresholdPortMapEntriesHigh in
      natv2InstanceTable;

   Objects returned:  natv2InstancePortMapEntries,
      natv2InstancePortMapCreations in natv2InstanceTable;

   Rate control:  natv2InstanceNotificationInterval in
      natv2InstanceTable (default 10 seconds between notifications for a
      given NAT instance).
      natv2InstanceTable.

   Notification: natv2NotificationSubscriberPortMapEntriesHigh.
   Indicates that the total number of entries in the port map table for
   the given subscriber equals or exceeds the threshold value configured
   for that subscriber.

   Compared value:  natv2SubscriberPortMapEntries in
      natv2SubscriberTable;

   Threshold:  natv2SubscriberThresholdPortMapEntriesHigh in
      natv2SubscriberTable;

   Objects returned:  natv2SubscriberPortMapEntries,
      natv2SubscriberPortMapCreations in natv2SubscriberTable;

   Rate control:  natv2SubscriberNotificationInterval in
      natv2SubscriberTable (default 60 seconds between notifications for
      a given subscriber).
      natv2SubscriberTable.

3.1.3.  State Information

   State information provides a snapshot of the content and extent of
   the NAT mapping tables at a given moment of time.  The address and
   port mapping tables are described in detail below.  In addition to
   these tables, two state variables are provided: current number of
   entries in the address mapping table, and current number of entries
   in the port mapping table.  With one exception, these are provided at
   four levels of granularity: per NAT instance, per protocol, per
   address pool, and per subscriber.  Address map entries are not
   tracked per protocol, since address mapping is protocol-independent.

3.1.4.  Statistics

   NATV2-MIB provides a number of counters, intended to help both with
   provisioning of the NAT and debugging of problems.  As with the state
   data, these counters are provided at the four levels of NAT instance,
   protocol, address pool, and subscriber when they make sense.  Each
   counter is cumulative beginning from a "last discontuity time"
   recorded by an object that is usually in the table containing the
   counter.

   The basic set of counters, as reflected in the NAT instance table, is
   as follows:

   Translations:  number of packets processed and translated (in this
      case, in total for the NAT instance);

   Address map entry creations:  cumulative number of address map
      entries created, including static mappings;

   Port map entry creations:  cumulative number of port map entries
      created, including static mappings;

   Address map limit drops:  cumulative number of packets dropped rather
      than translated because the packet would have triggered the
      creation of a new address mapping, but the configured limit on
      number of address map entries has already been reached.

   Port map limit drops:  cumulative number of packets dropped rather
      than translated because the packet would have triggered the
      creation of a new port mapping, but the configured limit on number
      of port map entries has already been reached.

   Active subscriber limit drops:  cumulative number of packets dropped
      rather than translated because the packet would have triggered the
      creation of a new address and/or port mapping for a subscriber
      with no existing entries in either table, but the configured limit
      on number of active subscribers has already been reached.

   Address mapping failure drops:  cumulative number of packets dropped
      because the packet would have triggered the creation of a new
      address mapping, but no address could be allocated in the external
      realm concerned because all addresses from the selected address
      pool (or the whole realm, if no address pool has been configured
      for that realm) have already been fully allocated.

   Port mapping failure drops:  cumulative number of packets dropped
      because the packet would have triggered the creation of a new port
      mapping, but no port could be allocated for the protocol
      concerned.  The precise conditions under which these packet drops
      occur depend on the pooling behavior [RFC4787] configured or
      implemented in the NAT instance.  See the DESCRIPTION clause for
      the natv2InstancePortMapFailureDrops object for a detailed
      description of the different cases.  These cases were defined with
      care to ensure that address mapping failure could be distinguished
      from port mapping failure.

   Fragment drops:  cumulative number of packets dropped because the
      packet contains a fragment and the fragment behavior [RFC4787]
      configured or implemented in the NAT instance indicates that the
      packet should be dropped.  The main case is a NAT instance that
      meets REQ-14 of [RFC4787], hence can receive and process out-of-
      order fragments.  In that case, dropping occurs only when the
      configured limit on pending fragments provided by NATV2-MIB has
      already been reached.  The other cases are detailed in the
      DESCRIPTION clause of the natv2InstanceFragmentBehavior object.

   Other resource drops:  cumulative number of packets dropped because
      of unavailability of some other resource.  The most likely case
      would be packets where the upper layer protocol is not one
      supported by the NAT instance.

   Table 1 indicates the granularities at which these statistics are
   reported.

   +-----------------------+------------+----------+------+------------+
   | Statistic             |    NAT     | Protocol | Pool | Subscriber |
   |                       |  Instance  |          |      |            |
   +-----------------------+------------+----------+------+------------+
   | Translations          |    Yes     |   Yes    |  No  |    Yes     |
   | Address map entry     |    Yes     |    No    | Yes  |    Yes     |
   | creations             |            |          |      |            |
   | Port map entry        |    Yes     |   Yes    | Yes  |    Yes     |
   | creations             |            |          |      |            |
   | Address map limit     |    Yes     |    No    |  No  |     No     |
   | drops                 |            |          |      |            |
   | Port map limit drops  |    Yes     |    No    |  No  |    Yes     |
   | Active subscriber     |    Yes     |    No    |  No  |     No     |
   | limit drops           |            |          |      |            |
   | Address mapping       |    Yes     |    No    | Yes  |    Yes     |
   | failure drops         |            |          |      |            |
   | Port mapping failure  |    Yes     |   Yes    | Yes  |    Yes     |
   | drops                 |            |          |      |            |
   | Fragment drops        |    Yes     |    No    |  No  |     No     |
   | Other resource drops  |    Yes     |    No    |  No  |     No     |
   +-----------------------+------------+----------+------+------------+

           Table 1: Statistics Provided By Level of Granularity

3.2.  Outline of MIB Module Organization

   Figure 1 shows how object identifiers are organized in the NATV2-MIB
   module.  Under the general natv2MIB object identifier in the mib-2
   tree, the objects are classed into four groups:

   natv2MIBNotifications(0)  identifies the five notifications described
      in Section 3.1.2;

   natv2MIBDeviceObjects(1)  identifies objects relating to the whole
      device, specifically, the subscriber table.

   natv2MIBInstanceObjects(2)  identifies objects relating to individual
      NAT instances.  These include the NAT instance table, the protocol
      table, the address pool table and its address range expansion, the
      address map table, and the port map table.

   natv2MIBConformance(3)  identifies the group and compliance clauses,
      specified for the three application scenarios described in
      Section 3.4.

                              natv2MIB
                                  |
              +-------------+-------------+-------------+
              |             |             |             |
                            |             |             |
              0             |             |             |
    natv2MIBNotifications   |             |             |
       |                                  |             |
       |                    1             |             |
       |          natv2MIBDeviceObjects   |             |
      Five            |                                 |
   notifications      |                   2             |
                      |         natv2MIBInstanceObjects |
                      |             |
                  Subscriber        |                   3
                  table             |         natv2MIBConformance
                                    |                   |
                                    |                   |
                                Six per-NAT-            |
                                instance tables         |
                                                        |
                          +----------------------+-------
                          |                      |
                          |                      |

                          1                      2
                 natv2MIBCompliances       natv2MIBGroups
                          |                      |
                          |                      |
                        Basic                  Basic
                        Pooled                 Pooled
                   Carrier grade NAT     Carrier grade NAT

        Figure 1: Organization of Object Identifiers For NATV2-MIB

3.3.  Detailed MIB Module Walk-Through

   This section reviews the contents of the NATV2-MIB module.  The table
   descriptions include references to subsections of Section 3.1 where
   desirable to avoid repetition of that information.

3.3.1.  Textual Conventions

   The module defines four key textual conventions: ProtocolNumber,
   Natv2SubscriberIndex, Natv2InstanceIndex, and Natv2PoolIndex.
   ProtocolNumber is based on the IANA registry of protocol numbers,
   hence is potentially reusable by other MIB modules.

   Objects of type Natv2SubscriberIndex identify individual subscribers
   served by the the NAT device.  The values of these identifiers are
   administered and, in intent, are permanently associated with their
   respective subscribers.  Reuse of a value after a subscriber has been
   deleted is discouraged.  The scope of the subscriber index was
   defined to be at device rather than NAT instance level to make it
   easier to shift subscribers between instances (e.g., for load
   balancing).

   Objects of type Natv2InstanceIndex identify specific NAT instances on
   the device.  Again, these are administered values intended to be
   permanently associated with the NAT instances to which they have been
   assigned.

   Objects of type Natv2PoolIndex identify individual address pools in a
   given NAT instance.  As with the subscriber and instance index
   objects, the pool identifiers are administered and intended to be
   permanently associated with their respective pools.

3.3.2.  Notifications

   Notifications were described in Section 3.1.2.

3.3.3.  The Subscriber Table: natv2SubscriberTable

   Table natv2SubscriberTable is indexed by subscriber index.  One
   conceptual row contains information relating to a specific
   subscriber: the subscriber's internal address or prefix for
   correlation with other management information; state and statistical
   information as described in Section 3.1.3 and Section 3.1.4, the per-
   subscriber control objects described in Section 3.1.1, and
   natv2SubscriberDiscontinuityTime, which provides a timestamp of the
   latest time following which the statistics have accumulated without
   discontinuity.

   Turning back to the address information for a moment: this
   information includes the identity of the address realm in which the
   address is routable.  That enables support of an arbitrary number of
   address realms on the same NAT instance.  Address realm identifiers
   are administered values in the form of a limited-length
   SnmpAdminString.  In the absence of configuration to the contrary,
   the default realm for all internal addresses as recorded in mapping
   entries is "internal".

      The term "address realm" is defined in [RFC2663] Section 2.1 and
      reused in subsequent NAT-related documents.

   In the special case of DS-Lite [RFC6333], for unique matching of the
   subscriber data to other information in the MIB module, it is
   necessary that the address information should relate to the outer
   IPv6 header of packets going to or from the host, with the address
   realm being the one in which that IPv6 address is routable.  The
   presentation of address information for other types of tunneled
   access to the NAT is out of scope.

3.3.4.  The Instance Table: natv2InstanceTable

   Table natv2InstanceTable is indexed by an object of type
   Natv2InstanceIndex.  A conceptual row of this table provides
   information relating to a particular NAT instance configured on the
   device.

   Configuration information provided by this table includes an instance
   name of type DisplayString that may have been configured for this
   instance, and a set of objects indicating respectively the port
   mapping, filtering, pooling, and fragment behaviors configured or
   implemented in the instance.  These behaviors are all defined in
   [RFC4787].  Their values affect the interpretation of some of the
   statistics provided in the instance table.

   Read-write objects listed in Section 3.1.2 set the notification rate
   for instance-level notifications and set the thresholds that trigger
   them.  Additional read-write objects described in Section 3.1.1 set
   limits on the number of address and port mapping entries, number of
   pending fragments, and number of active subscribers for the instance.

   The state and statistical information provided by this table consists
   of the per-instance items described in Section 3.1.3 and
   Section 3.1.4 respectively. natv2InstanceDiscontinuityTime is a
   timestamp giving the time beyond which all of the statistical
   counters in natv2InstanceTable are guaranteed to have accumulated
   continuously.

3.3.5.  The Protocol Table: natv2ProtocolTable

   The protocol table is indexed by the NAT instance number and an
   object of type ProtocolNumber as described in Section 3.3.1 (i.e., an
   IANA-registered protocol number).  The set of protocols supported by
   the NAT instance is implementation-dependent, but MUST include
   ICMP(1), TCP(6), UDP(17), and ICMPv6(58).  Depending on the
   application, it SHOULD include IPv4 encapsulation(4), IPv6
   encapsulation(41), IPSec AH(51), and SCTP(132).  Support of PIM(103)
   is highly desirable.

   This table includes no configuration information.  The state and
   statistical information provided by this table consists of the per-
   protocol items described in Section 3.1.3 and Section 3.1.4
   respectively. natv2InstanceDiscontinuityTime in natv2InstanceTable is
   reused as the timestamp giving the time beyond which all of the
   statistical counters in natv2ProtocolTable are guaranteed to have
   accumulated continuously.  The reasoning is that any event affecting
   the continuity of per-protocol statistics will affect the continuity
   of NAT instance statistics, and vice versa.

3.3.6.  The Address Pool Table: natv2PoolTable

   The address pool table is indexed by the NAT instance identifier for
   the instance on which it is provisioned, plus a pool index of type
   Natv2PoolIndex.  Configuration information provided includes the
   address realm for which the pool provides addresses, the type of
   address (IPv4 or IPv6) supported by the realm, plus the port range it
   makes available for allocation.  The same set of port numbers (or, in
   the ICMP case, identifier values), is made available for every
   protocol supported by the NAT instance.  The port range is specified
   in terms of minimum and maximum port number.

   The state and statistical information provided by this table consists
   of the per-pool items described in Section 3.1.3 and Section 3.1.4
   respectively, plus two additional state objects described below.
   natv2PoolTable provides the pool-specific object
   natv2PoolDiscontinuityTime to indicate the time since which the
   statistical counters have accumulated continuously.

   Read-write objects to set high and low thresholds for pool usage
   notifications and for governing notification rate were identified in
   Section 3.1.2.  The default interval between notifications for a
   given address pool is set to 20 seconds.

      Implementation note: the thresholds are defined in terms of
      percentage of available port utilization.  The number of available
      ports in a pool is equal to (max port - min port + 1) (from the
      natv2PoolTable configuration information) multiplied by the number
      of addresses provisioned in the pool (sum of number of addresses
      provided by each natv2PoolRangeTable conceptual row relating to
      that pool).  At configuration time, the thresholds can be
      recalculated in terms of total number of port map entries
      corresponding to the configured percentage, so that runtime
      comparisons to the current number of port map entries require no
      further arithmetic operations.

   natv2PoolTable also provides two state objects that are returned with
   the notifications.  natv2PoolNotifiedPortMapProtocol identifies the
   most-mapped protocol at the time the notification was triggered.
   natv2PoolNotifiedPortMapEntries provides the total number of port map
   entries for that protocol using addresses owned by this pool at that
   same time.

3.3.7.  The Address Pool Address Range Table: natv2PoolRangeTable

   natv2PoolRangeTable provides configuration information only.  It is
   an expansion of natv2PoolTable giving the address ranges with which a
   given address pool has been configured.  As such, it is indexed by
   the combination of NAT instance index, address pool index, and a
   conceptual row index, where each conceptual row conveys a different
   address range.  The address range is specified in terms of lowest
   address, highest address rather than the usual prefix notation to
   provide maximum flexibility.

3.3.8.  The Address Map Table: natv2AddressMapTable

   The address map table provides a table of mappings from internal to
   external address at a given moment.  It is indexed by the combination
   of NAT instance index, internal realm, internal address type (IPv4 or
   IPv6) in that realm, the internal address of the local host for which
   the map entry was created, and a conceptual row index to traverse all
   of the entries relating to the same internal address.

   In the special case of DS-Lite [RFC6333], the internal address and
   realm used in the index are those of the IPv6 outer header.  The IPv4
   source address for the inner header, for which [RFC6333] has reserved
   addresses in the 192.0.0.0/29 range, is captured in two additional
   objects in the corresponding conceptual row:
   natv2AddressMapInternalMappedAddressType, and
   natv2AddressMapInternalMappedAddress.  In cases other than DS-Lite
   access these objects have no meaning.  (Other tunneled access is out
   of scope.)

   The additional information provided by natv2AddressMapTable consists
   of the external realm, address type in that realm, and mapped
   external address.  Depending on implementation support, the table
   also provides the index of the address pool from which the external
   address was drawn and the index of the subscriber to which the map
   entry belongs.

3.3.9.  The Port Map Table: natv2PortMapTable

   The port map table provides a table of mappings by protocol from
   external port, address, and realm to internal port, address, and
   realm.  As such, it is indexed by the combination of NAT instance
   index, protocol number, external realm identifier, address type in
   that realm, external address, and external port.  The mapping from
   external realm, address, and port to internal realm, address, and
   port is unique, so no conceptual row index is needed.  The indexing
   is designed to make it easy to trace individual sessions back to the
   host, based on the contents of packets observed in the external
   realm.

   Beyond the indexing, the information provided by the port map table
   consists of the internal realm, address type, address, and port
   number, and, depending on implementation support, the index of the
   subscriber to which the map entry belongs.

   As with the address map table, special provision is made for the case
   of DS-Lite [RFC6333].  The realm and outgoing source address are
   those for the outer header, and the address type is IPv6.  Additional
   objects natv2PortMapInternalMappedAddressType and
   natv2PortMapInternalMappedAddress capture the outgoing source address
   in the inner header, which will be in the well-known 192.0.0.0/29
   range.

3.4.  Conformance: Three Application Scenarios

   The conformance statements in NATV2-MIB provide for three application
   scenarios: basic NAT, NAT supporting address pools, and carrier grade
   NAT (CGN).

   A basic NAT MAY limit the number of NAT instances it supports to one,
   but MUST support indexing by NAT instance.  Similarly, a basic NAT
   MAY limit the number of realms it supports to two.  By definition, a
   basic NAT is not required to support the subscriber table, the
   address pool table, or the address pool address range table.  Some
   individual objects in other tables are also not relevant to basic
   NAT.

   A NAT supporting address pools adds the address pool table and the
   address pool address range table to what it implements.  Some
   individual objects in other tables also need to be implemented.  A
   NAT supporting address pools MUST support more than two realms.

   Finally, a CGN MUST support the full contents of the MIB module.
   That includes the subscriber table, but also includes the special
   provision for DS-Lite access in the address and port map tables.

4.  Definitions

   This MIB module IMPORTs objects from [RFC2578], [RFC2579], [RFC2580],
   [RFC3411], and [RFC4001].

  NATV2-MIB DEFINITIONS ::= BEGIN

  IMPORTS
       MODULE-IDENTITY,
       OBJECT-TYPE,
       Integer32,
       Unsigned32,
       Counter64,
       mib-2,
       NOTIFICATION-TYPE
               FROM SNMPv2-SMI          -- RFC 2578
       TEXTUAL-CONVENTION,
       DisplayString,
       TimeStamp
               FROM SNMPv2-TC           -- RFC 2579
       MODULE-COMPLIANCE,
       NOTIFICATION-GROUP,
       OBJECT-GROUP
               FROM SNMPv2-CONF         -- RFC 2580
       SnmpAdminString
               FROM SNMP-FRAMEWORK-MIB  -- RFC 3411
       InetAddressType,
       InetAddress,
       InetAddressPrefixLength,
       InetPortNumber
               FROM INET-ADDRESS-MIB;    -- RFC 4001

  natv2MIB MODULE-IDENTITY
       LAST-UPDATED "201502170000Z"
  -- RFC Ed.: set to publication date
       ORGANIZATION
               "IETF Behavior Engineering for Hindrance Avoidance
                (BEHAVE) Working Group"
       CONTACT-INFO
               "Working Group Email: behave@ietf.org

                Simon Perreault
                Jive Communications
                Quebec, QC
                Canada

                Email: sperreault@jive.com

                Tina Tsou
                Huawei Technologies
                Bantian, Longgang
                Shenzhen 518129
                PR China

                Email: tina.tsou.zouting@huawei.com

                Senthil Sivakumar
                Cisco Systems
                7100-8 Kit Creek Road
                Research Triangle Park, North Carolina  27709
                USA

                Phone: +1 919 392 5158
                Email: ssenthil@cisco.com

                Tom Taylor
                PT Taylor Consulting
                Ottawa
                Canada

                Email: tom.taylor.stds@gmail.com"

       DESCRIPTION
               "This MIB module defines the generic managed objects
                for NAT.

                Copyright (C) The Internet Society (2015).  This
                version of this MIB module is part of RFC yyyy; see
                the RFC itself for full legal notices."
       REVISION     "201502170000Z"
  -- RFC Ed.: set to publication date
       DESCRIPTION
               "Complete rewrite, published as RFC yyyy.
                Replaces former version published as RFC 4008."
  -- RFC Ed.: replace yyyy with actual RFC number and set date"
       ::= { mib-2 123 }
         -- temporary for compilation pending IANA assignment

  -- textual conventions
  ProtocolNumber ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
          "A protocol number, from the 'protocol-numbers' IANA
           registry."
      REFERENCE
          "IANA Protocol Numbers,
           http://www.iana.org/assignments/protocol-numbers/protocol-
           numbers.xhtml#protocol-numbers-1"
      SYNTAX Unsigned32 (0..255)

  Natv2SubscriberIndex ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
          "A unique value, greater than zero, for each subscriber
           in the managed system.  The value for each
           subscriber MUST remain constant at least from one
           update of the entity's natv2SubscriberDiscontinuityTime
           object until the next update of that object. If a
           subscriber is deleted, its assigned index value MUST NOT
           be assigned to another subscriber at least until
           reinitialization of the entity's management system."
      SYNTAX Unsigned32 (1..4294967295)

  Natv2SubscriberIndexOrZero ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
          "This textual convention is an extension of the
           Natv2SubscriberIndex convention.  The latter defines a
           greater than zero value used to identify a subscriber in
           the managed system. This extension permits the additional
           value of zero, which serves as a placeholder when no
           subscriber is associated with the object."
      SYNTAX Unsigned32 (0|1..4294967295)

  Natv2InstanceIndex ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
          "A unique value, greater than zero, for each NAT instance
           in the managed system.  It is RECOMMENDED that values are
           assigned contiguously starting from 1.  The value for each
           NAT instance MUST remain constant at least from one
           update of the entity's natv2InstanceDiscontinuityTime
           object until the next update of that object. If a NAT
           instance is deleted, its assigned index value MUST NOT
           be assigned to another NAT instance at least until
           reinitialization of the entity's management system."
      SYNTAX Unsigned32 (1..4294967295)

  Natv2PoolIndex ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
         "A unique value over the containing NAT instance, greater than
          zero, for each address pool supported by that NAT instance.
          It is RECOMMENDED that values are assigned contiguously
          starting from 1.  The value for each address pool MUST remain
          constant at least from one update of the entity's
          natv2PoolDiscontinuityTime object until the next update of
          that object. If an address pool is deleted, its assigned
          index value MUST NOT be assigned to another address pool for
          the same NAT instance at least until reinitialization of the
          entity's management system."
      SYNTAX Unsigned32 (1..4294967295)

  Natv2PoolIndexOrZero ::= TEXTUAL-CONVENTION
      DISPLAY-HINT "d"
      STATUS current
      DESCRIPTION
          "This textual convention is an extension of the
           Natv2PoolIndex convention.  The latter defines a greater
           than zero value used to identify address pools in the
           managed system.  This extension permits the additional
           value of zero, which serves as a placeholder when the
           implementation does not support address pools or no address
           pool is configured in a given external realm."
      SYNTAX Unsigned32 (0|1..4294967295)

  -- notifications

  natv2MIBNotifications OBJECT IDENTIFIER ::= { natv2MIB 0 }

  natv2NotificationPoolUsageLow NOTIFICATION-TYPE
      OBJECTS { natv2PoolNotifiedPortMapEntries,
                natv2PoolNotifiedPortMapProtocol  }
      STATUS current
      DESCRIPTION
          "This notification is triggered when an address pool's usage
           becomes less than or equal to the value of the
           natv2PoolThresholdUsageLow object for that pool, unless the
           notification has been disabled by setting the value of the
           threshold to -1. It is reported subject to the rate
           limitation specified by natv2PortMapNotificationInterval.

           Address pool usage is calculated as the percentage of the
           total number of ports allocated to the address pool that are
           already in use, for the most-mapped protocol at the time
           the notification is triggered. The two returned objects are
           members of natv2PoolTable indexed by the NAT instance and
           pool indices for which the event is being reported. They
           give the number of port map entries using external addresses
           configured on the pool for the most-mapped protocol and
           identify that protocol at the time the notification was
           triggered."
      REFERENCE
          "RFC yyyy Section 3.1.2 and Section 3.3.6."
      ::= { natv2MIBNotifications 1 }

  natv2NotificationPoolUsageHigh NOTIFICATION-TYPE
      OBJECTS { natv2PoolNotifiedPortMapEntries,
                natv2PoolNotifiedPortMapProtocol  }
      STATUS current
      DESCRIPTION
          "This notification is triggered when an address pool's usage
           becomes greater than or equal to the value of the
           natv2PoolThresholdUsageHigh object for that pool, unless
           the notification has been disabled by setting the value of
           the threshold to 0. -1. It is reported subject to the rate
           limitation specified by natv2PortMapNotificationInterval.

           Address pool usage is calculated as the percentage of the
           total number of ports allocated to the address pool that are
           already in use, for the most-mapped protocol at the time the
           notification is triggered. The two returned objects are
           members of natv2PoolTable indexed by the NAT instance and
           pool indices for which the event is being reported. They
           give the number of port map entries using external addresses
           configured on the pool for the most-mapped protocol and
           identify that protocol at the time the notification was
           triggered."
      REFERENCE
          "RFC yyyy Section 3.1.2 and Section 3.3.6."
      ::= { natv2MIBNotifications 2 }

  natv2NotificationInstanceAddressMapEntriesHigh NOTIFICATION-TYPE
      OBJECTS { natv2InstanceAddressMapEntries,
                natv2InstanceAddressMapCreations }
      STATUS current
      DESCRIPTION
          "This notification is triggered when the value of
           natv2InstanceAddressMapEntries equals or exceeds the value
           of the natv2InstanceThresholdAddressMapEntriesHigh object
           for the NAT instance, unless disabled by setting that
           threshold to 0. -1. Reporting is subject to the rate limitation
           given by natv2InstanceNotificationInterval.

           natv2InstanceAddressMapEntries and
           natv2InstanceAddressMapCreations are members of table
           natv2InstanceTable indexed by the identifier of the NAT
           instance for which the event is being reported. The values
           reported are those observed at the moment the notification
           was triggered."
      REFERENCE
          "RFC yyyy Section 3.1.2."
      ::= { natv2MIBNotifications 3 }

  natv2NotificationInstancePortMapEntriesHigh NOTIFICATION-TYPE
      OBJECTS { natv2InstancePortMapEntries,
                natv2InstancePortMapCreations }
      STATUS current
      DESCRIPTION
          "This notification is triggered when the value of
           natv2InstancePortMapEntries becomes greater than or equal to
           the value of natv2InstanceThresholdPortMapEntriesHigh,
           unless disabled by setting that threshold to 0. -1. Reporting is
           subject to the rate limitation given by
           natv2InstanceNotificationInterval.

           natv2InstancePortMapEntries and
           natv2InstancePortMapCreations are members of table
           natv2InstanceTable indexed by the identifier of the NAT
           instance for which the event is being reported.  The values
           reported are those observed at the moment the notification
           was triggered."
      ::= { natv2MIBNotifications 4 }

  natv2NotificationSubscriberPortMappingEntriesHigh
  NOTIFICATION-TYPE
      OBJECTS { natv2SubscriberPortMapEntries,
                natv2SubscriberPortMapCreations }
      STATUS current
      DESCRIPTION
          "This notification is triggered when the value of
           natv2SubscriberPortMapEntries for an individual subscriber
           becomes greater than or equal to the value of the
           natv2SubscriberThresholdPortMapEntriesHigh object for that
           subscriber, unless disabled by setting that threshold to 0. -1.

           Reporting is subject to the rate limitation given by
           natv2SubscriberNotificationInterval.

           natv2SubscriberPortMapEntries and
           natv2SubscriberPortMapCreations are members of table
           natv2SubscriberTable indexed by the subscriber for
           which the event is being reported.  The values
           reported are those observed at the moment the notification
           was triggered."
      ::= { natv2MIBNotifications 5 }

  -- Device-level objects

  natv2MIBDeviceObjects OBJECT IDENTIFIER ::= { natv2MIB 1 }

  -- subscriber table

  natv2SubscriberTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2SubscriberEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Table of subscribers. As well as the subscriber index, it
           provides per-subscriber state and counter objects, a last
           discontinuity time object for the counters, and writable
           threshold value and limit on port consumption."
      REFERENCE
          "RFC yyyy Section 3.3.3."
      ::= { natv2MIBDeviceObjects 1 }

  natv2SubscriberEntry OBJECT-TYPE
      SYNTAX Natv2SubscriberEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Each entry describes a single subscriber."
      INDEX { natv2SubscriberIndex }
      ::= { natv2SubscriberTable 1 }

  Natv2SubscriberEntry ::=
      SEQUENCE {
          natv2SubscriberIndex                  Natv2SubscriberIndex,
          natv2SubscriberInternalRealm               SnmpAdminString,
          natv2SubscriberInternalPrefixType          InetAddressType,
          natv2SubscriberInternalPrefix              InetAddress,
          natv2SubscriberInternalPrefixLength InetAddressPrefixLength,
  -- State
          natv2SubscriberAddressMapEntries           Unsigned32,
          natv2SubscriberPortMapEntries              Unsigned32,
  -- Counters and last discontinuity time
          natv2SubscriberTranslations                Counter64,
          natv2SubscriberAddressMapCreations         Counter64,
          natv2SubscriberPortMapCreations            Counter64,
          natv2SubscriberAddressMapFailureDrops      Counter64,
          natv2SubscriberPortMapFailureDrops         Counter64,
          natv2SubscriberDiscontinuityTime           TimeStamp,
  -- Read-write controls
          natv2SubscriberLimitPortMapEntries         Unsigned32,
  -- Disable limit notifications by setting threshold to 0 (default) -1
          natv2SubscriberThresholdPortMapEntriesHigh Unsigned32, Integer32,
  -- Disable notifications limit by setting threshold to 0 (default)
          natv2SubscriberNotificationInterval        Unsigned32
   -- Default is 60 seconds
      }

  natv2SubscriberIndex OBJECT-TYPE
      SYNTAX Natv2SubscriberIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "A unique value, greater than zero, for each subscriber
           in the managed system.  The value for each
           subscriber MUST remain constant at least from one
           update of the entity's natv2SubscriberDiscontinuityTime
           object until the next update of that object. If a
           subscriber is deleted, its assigned index value MUST NOT
           be assigned to another subscriber at least until
           reinitialization of the entity's management system."
      ::= { natv2SubscriberEntry 1 }

  -- Configuration for this subscriber: realm, internal address(es)

  natv2SubscriberInternalRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE(0..32))
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The address realm to which this subscriber belongs. A realm
           defines an address space. All NATs support at least two
           realms.

           The default realm for subscribers is 'internal'.
           Administrators can set other values for individual
           subscribers when they are configured. The administrator MAY
           configure a new value of natv2SubscriberRealm at any time
           subsequent to initial configuration of the subscriber. If
           this happens, it MUST be treated as a point of discontinuity
           requiring an update of natv2SubscriberDiscontinuityTime.

           When the subscriber sends a packet to the NAT through a
           DS-Lite [RFC 6333] tunnel, this is the realm of the outer
           packet header source address. Other tunneled access is out
           of scope."
      REFERENCE
           "Address realm: RFC 2663. DS-Lite: RFC 6333."
      DEFVAL
          { "internal" }
      ::= { natv2SubscriberEntry 2 }

  natv2SubscriberInternalPrefixType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Subscriber's internal prefix type. Any value other than
           ipv4(1) or ipv6(2) would be unexpected. In the case of
           DS-Lite access, this is the prefix type (IPv6(2)) used in
           the outer packet header."
      REFERENCE
          "DS-Lite: RFC 6333."
      ::= { natv2SubscriberEntry 3 }

  natv2SubscriberInternalPrefix OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Prefix assigned to a subscriber's CPE. Source addresses of
           packets outgoing from the subscriber will be contained
           within this prefix.  In the case of DS-Lite access,
           the source address taken from the prefix will be
           that of the outer header."
      REFERENCE
          "DS-Lite: RFC 6333."
      ::= { natv2SubscriberEntry 4 }

  natv2SubscriberInternalPrefixLength OBJECT-TYPE
      SYNTAX InetAddressPrefixLength
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Length of the prefix assigned to a subscriber's CPE, in
           bits.  If a single address is assigned, this will be 32
           for IPv4 and 128 for IPv6."

      ::= { natv2SubscriberEntry 5 }

  -- State objects

  natv2SubscriberAddressMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of address map entries for the
           subscriber, including static mappings. An address map entry
           maps from a given internal address and realm to an external
           address in a particular external realm. This definition
           includes 'hairpin' mappings, where the external realm is the
           same as the internal one. Address map entries are also
           tracked per instance and per address pool within the
           instance."
      REFERENCE
          "RFC yyyy Section 3.3.8."
      ::= { natv2SubscriberEntry 6 }

  natv2SubscriberPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of port map entries in the port map table
           for the subscriber, including static mappings. A port map
           entry maps from a given external realm, address, and port
           for a given protocol to an internal realm, address, and
           port. This definition includes 'hairpin' mappings, where the
           external realm is the same as the internal one. Port map
           entries are also tracked per instance and per protocol and
           address pool within the instance."
      REFERENCE
          "RFC yyyy Section 3.3.9."
      ::= { natv2SubscriberEntry 7 }

  -- Counters and last discontinuity time

  natv2SubscriberTranslations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of translated packets received from or
           sent to this subscriber. This value MUST be monotone
           increasing in the periods between updates of the entity's
           natv2SubscriberDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2SubscriberDiscontinuityTime."
      ::= { natv2SubscriberEntry 8 }

  natv2SubscriberAddressMapCreations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of address map entries created for
           this subscriber, including static mappings. Address map
           entries are also tracked per instance and per protocol and
           address pool within the instance.

           This value MUST be monotone increasing in
           the periods between updates of the entity's
           natv2SubscriberDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2SubscriberDiscontinuityTime."
      ::= { natv2SubscriberEntry 9 }

  natv2SubscriberPortMapCreations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of port map entries created for this
           subscriber, including static mappings. Port map entries are
           also tracked per instance and per protocol and address pool
           within the instance.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2SubscriberDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2SubscriberDiscontinuityTime."
      ::= { natv2SubscriberEntry 10 }

  natv2SubscriberAddressMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets originated by this
           subscriber that were dropped because the packet would have
           triggered the creation of a new address map entry, but no
           address could be allocated in the selected external realm
           because all addresses from the selected address pool (or the
           whole realm, if no address pool has been configured for that
           realm) have already been fully allocated.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2SubscriberDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2SubscriberDiscontinuityTime."
      ::= { natv2SubscriberEntry 11 }

  natv2SubscriberPortMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because the
           packet would have triggered the creation of a new
           port mapping, but no port could be allocated for the
           protocol concerned. The usual case for this will be
           for a NAT instance that supports address pooling and
           the 'paired' pooling behavior recommended by RFC 4787,
           where the internal endpoint has used up all of the
           ports allocated to it for the address it was mapped to
           in the selected address pool in the external realm
           concerned and cannot be given more ports because
           - policy or implementation prevents it from having a
             second address in the same pool, and
           - policy or unavailability prevents it from acquiring
             more ports at its originally assigned address.

           If the NAT instance supports address pooling but its
           pooling behavior is 'arbitrary' (meaning that
           the NAT instance can allocate a new port mapping for
           the given internal endpoint on any address in the
           selected address pool and is not bound to what it has
           already mapped for that endpoint), then this counter
           is incremented when all ports for the protocol concerned
           over the whole of the selected address pool are already
           in use.

           As a third case, if no address pools have been configured
           for the external realm concerned, then this counter is
           incremented because all ports for the protocol involved over
           the whole set of addresses available for that external realm
           are already in use.

           Finally, this counter is incremented if the packet would
           have triggered the creation of a new port mapping, but the
           current value of natv2SubscriberPortMapEntries equals or
           exceeds the value of natv2SubscriberLimitPortMapEntries
           for this subscriber (unless that limit is disabled).

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2SubscriberDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2SubscriberDiscontinuityTime."
      REFERENCE
          "Pooling behavior: RFC 4787, end of section 4.1."
      ::= { natv2SubscriberEntry 12 }

  natv2SubscriberDiscontinuityTime OBJECT-TYPE
      SYNTAX TimeStamp
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Snapshot of the value of the sysUpTime object at the
           beginning of the latest period of continuity of the
           statistical counters associated with this subscriber."
      ::= { natv2SubscriberEntry 14 }

  -- Per-subscriber limit and threshold on port mappings
  -- Disabled if set to zero
  natv2SubscriberLimitPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Limit on total number of port mappings active for this
           subscriber (natv2SubscriberPortMapEntries). Once this limit
           is reached, packets that might have triggered new port
           mappings are dropped. The number of such packets dropped is
           counted in natv2InstancePortMapFailureDrops.

           Limit is disabled if set to zero (default)." zero."
      DEFVAL
           { 0 }
      ::= { natv2SubscriberEntry 15 }

  natv2SubscriberThresholdPortMapEntriesHigh OBJECT-TYPE
      SYNTAX Unsigned32 Integer32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Notification threshold for total number of port mappings
           active for this subscriber. Whenever
           natv2SubscriberPortMapEntries is updated, if it equals or
           exceeds natv2SubscriberThresholdPortMapEntriesHigh, the
           notification
           natv2NotificationSubscriberPortMappingEntriesHigh is
           triggered, unless the notification is disabled by setting
           the threshold to 0. -1. Reporting is subject to the minimum
           inter-notification interval given by
           natv2SubscriberNotificationInterval. If multiple
           notifications are triggered during one interval, the agent
           MUST report only the one containing the highest value of
           natv2SubscriberPortMapEntries and discard the others."
      DEFVAL
           { 0 -1 }
      ::= { natv2SubscriberEntry 16 }

  natv2SubscriberNotificationInterval OBJECT-TYPE
      SYNTAX Unsigned32 (1..3600)
      UNITS
          "Seconds"
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Minimum number of seconds (default 60) between successive
           reporting of notifications for this subscriber. Controls the
           reporting of
           natv2NotificationSubscriberPortMappingEntriesHigh."
      DEFVAL
           { 60 }
      ::= { natv2SubscriberEntry 17 }

  -- Per-NAT-instance objects

  natv2MIBInstanceObjects OBJECT IDENTIFIER ::= { natv2MIB 2 }

  -- Instance table

  natv2InstanceTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2InstanceEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Table of NAT instances. As well as state and counter
           objects, it provides the instance index, instance name, and
           the last discontinuity time object which is applicable to
           the counters. It also contains writable thresholds for
           reporting of notifications and limits on usage of resources
           at the level of the NAT instance.

           It is assumed that NAT instances can be created and deleted
           dynamically, but this MIB module does not provide the means
           to do so. For restrictions on assignment and maintenance of
           the NAT index instance see the description of
           natv2InstanceIndex in the table below. For the requirements
           on maintenance of the values of the counters in this table
           see the description of natv2InstanceDiscontinuityTime in
           this table.

           Each NAT instance has its own resources and behavior. The
           resources include memory as reflected in space for map
           entries, processing power as reflected in the rate of map
           creation and deletion, and mappable addresses in each realm
           that can play the role of an external realm for at least
           some mappings for that instance. The NAT instance table
           includes limits and notification thresholds that relate to
           memory usage for mapping at the level of the whole instance.
           The limit on number of subscribers with active mappings is a
           limit to some extent on processor usage.

           The mappable 'external' addresses may or may not be
           organized into address pools. For a definition of address
           pools see the description of natv2PoolTable. If the instance
           does support address pools, it also has a pooling behavior.
           Mapping, filtering, and pooling behavior are defined in the
           descriptions of the natv2InstancePortMappingBehavior,
           natv2InstanceFilteringBehavior, and
           natv2InstancePoolingBehavior objects in this table. The
           instance also has a fragmentation behavior, defined in the
           description of the natv2InstanceFragmentBehavior object."
      REFERENCE
          "RFC yyyy Section 3.3.4. NAT behaviors: RFC 4787
           (primary, UDP); RFC 5382 (TCP), RFC 5508 (ICMP), RFC5597
           (DCCP)."
      ::= { natv2MIBInstanceObjects 1 }

  natv2InstanceEntry OBJECT-TYPE
      SYNTAX Natv2InstanceEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Objects related to a single NAT instance."
      INDEX { natv2InstanceIndex }
      ::= { natv2InstanceTable 1 }

  Natv2InstanceEntry ::=
      SEQUENCE {
           natv2InstanceIndex                    Natv2InstanceIndex,
           natv2InstanceAlias                         DisplayString,
  -- Configured behaviors
           natv2InstancePortMappingBehavior           INTEGER,
           natv2InstanceFilteringBehavior             INTEGER,
           natv2InstancePoolingBehavior               INTEGER,
           natv2InstanceFragmentBehavior              INTEGER,
  -- State
           natv2InstanceAddressMapEntries              Unsigned32,
           natv2InstancePortMapEntries                 Unsigned32,
  -- Statistics and discontinuity time
           natv2InstanceTranslations                   Counter64,
           natv2InstanceAddressMapCreations            Counter64,
           natv2InstancePortMapCreations               Counter64,
           natv2InstanceAddressMapEntryLimitDrops      Counter64,
           natv2InstancePortMapEntryLimitDrops         Counter64,
           natv2InstanceSubscriberActiveLimitDrops     Counter64,
           natv2InstanceAddressMapFailureDrops         Counter64,
           natv2InstancePortMapFailureDrops            Counter64,
           natv2InstanceFragmentDrops                  Counter64,
           natv2InstanceOtherResourceFailureDrops      Counter64,
           natv2InstanceDiscontinuityTime              TimeStamp,
  -- Notification thresholds, disabled if set to 0 -1
           natv2InstanceThresholdAddressMapEntriesHigh Unsigned32, Integer32,
           natv2InstanceThresholdPortMapEntriesHigh    Unsigned32,    Integer32,
           natv2InstanceNotificationInterval           Unsigned32,
  -- Limits, disabled if set to 0
           natv2InstanceLimitAddressMapEntries         Unsigned32,
           natv2InstanceLimitPortMapEntries            Unsigned32,
           natv2InstanceLimitPendingFragments          Unsigned32,
           natv2InstanceLimitSubscriberActives         Unsigned32
      }

  natv2InstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "NAT instance index. It is up to the implementation to
           determine which values correspond to in-service NAT
           instances. This object is used as an index for all tables
           defined below."
      ::= { natv2InstanceEntry 1 }

  natv2InstanceAlias OBJECT-TYPE
      SYNTAX DisplayString (SIZE (0..64))
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "This object is an 'alias' name for the NAT instance as
           specified by a network manager, and provides a non-volatile
           'handle' for the instance.

           An example of the value which a network manager might store
           in this object for a NAT instance is the name/identifier of
           the interface that brings in internal traffic for this NAT
           instance or the name of the VRF for internal traffic."
      ::= { natv2InstanceEntry 2 }

  -- Configured behaviors

  natv2InstancePortMappingBehavior OBJECT-TYPE
      SYNTAX INTEGER {
             endpointIndependent (0),
             addressDependent (1),
             addressAndPortDependent (2)
          }
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Port mapping behavior is the policy governing selection of
           external address and port in a given realm for a given
           five-tuple of source address and port, destination address
           and port, and protocol.

           endpointIndependent(0), the behavior REQUIRED by RFC 4787
           REQ-1, maps the source address and port to the same
           external address and port for all destination address and
           port combinations reached through the same external realm
           and using the given protocol.

           addressDependent(1) maps to the same external address and
           port for all destination ports at the same destination
           address reached through the same external realm and using
           the given protocol.

           addressAndPortDependent(2) maps to a separate external
           address and port combination for each different
           destination address and port combination reached through
           the same external realm."
      REFERENCE
           "RFC 4787 section 4.1."
      ::= { natv2InstanceEntry 3 }

  natv2InstanceFilteringBehavior OBJECT-TYPE
      SYNTAX INTEGER {
             endpointIndependent (0),
             addressDependent (1),
             addressAndPortDependent (2)
          }
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Filtering behavior is the policy governing acceptance or
           dropping of packets incoming from remote sources via a
           given external realm and destined to a specific three-tuple
           of external address, port, and protocol at the NAT instance
           that has been assigned in a port mapping.

           endpointIndependent(0) accepts for translation packets from
           all combinations of remote address and port destined to the
           mapped external address and port via the given external
           realm and using the given protocol.

           addressDependent(1) accepts for translation packets from all
           remote ports from the same remote source address destined to
           the mapped external address and port via the given external
           realm and using the given protocol.

           addressAndPortDependent(2) accepts for translation only
           those packets with the same remote source address, port, and
           protocol incoming from the same external realm as identified
           when the applicable port map entry was created.

           RFC 4787 REQ-8 recommends either endpointIndependent(0) or
           addressDependent(1) filtering behavior depending on whether
           application-friendliness or security takes priority."
      REFERENCE
          "RFC 4787 section 5."
      ::= { natv2InstanceEntry 4 }

  natv2InstancePoolingBehavior OBJECT-TYPE
      SYNTAX INTEGER {
             arbitrary (0),
             paired (1)
          }
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Pooling behavior is the policy used to select the address
           for a new port mapping within a given address pool to which
           the internal address has already been mapped.

           arbitrary(0) pooling behavior means that the NAT instance
           may create the new port mapping using any address in the
           pool that has a free port for the protocol concerned.

           paired(1) pooling behavior, the behavior RECOMMENDED by RFC
           4787 REQ-2, means that once a given internal address has
           been mapped to a particular address in a particular pool,
           further mappings of the same internal address to that pool
           will reuse the previously assigned pool member address."
      REFERENCE
          "RFC 4787 near the end of section 4.1"
      ::= { natv2InstanceEntry 5 }

  natv2InstanceFragmentBehavior OBJECT-TYPE
      SYNTAX INTEGER {
             fragmentNone (0),
             fragmentInOrder (1),
             fragmentOutOfOrder (2)
          }
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Fragment behavior is the NAT instance's capability to
           receive and translate fragments incoming from remote
           sources.

           fragmentNone(0) implies no capability to translate incoming
           fragments, so all received fragments are dropped. Each
           dropped fragment is counted in natv2InstanceFragmentDrops.

           fragmentInOrder(1) implies the ability to translate
           fragments only if they are received in order, so that in
           particular the header is in the first packet. If a fragment
           is received out of order, it is dropped and counted in
           natv2InstanceFragmentDrops.

           fragmentOutOfOrder(2), the capability REQUIRED by RFC 4787
           REQ-14, implies the capability to translate fragments even
           when they arrive out of order, subject to a protective
           limit natv2InstanceLimitPendingFragments on total number of
           fragments awaiting the first fragment of the chain. If the
           implementation supports this capability,
           natv2InstanceFragmentDrops is incremented only when a new
           fragment arrives but is dropped because the limit on pending
           fragments has already been reached."
      REFERENCE
          "RFC 4787 section 11."
      ::= { natv2InstanceEntry 6 }

  -- State

  natv2InstanceAddressMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of address map entries in total over the
           whole NAT instance, including static mappings. An address
           map entry maps from a given internal address and realm to an
           external address in a particular external realm. This
           definition includes 'hairpin' mappings, where the external
           realm is the same as the internal one. Address map entries
           are also tracked per subscriber and per address pool within
           the instance."
      REFERENCE
          "RFC yyyy Section 3.3.8. RFC 4787 section 6."
      ::= { natv2InstanceEntry 7 }

  natv2InstancePortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of entries in the port map table in total
           over the whole NAT instance, including static mappings. A
           port map entry maps from a given external realm, address,
           and port for a given protocol to an internal realm, address,
           and port. This definition includes 'hairpin' mappings, where
           the external realm is the same as the internal one. Port map
           entries are also tracked per subscriber and per protocol and
           address pool within the instance."
      REFERENCE
          "RFC yyyy Section 3.3.9.
           Hairpinning: RFC 4787 Section 6."
      ::= { natv2InstanceEntry 8 }

  -- Statistics
  natv2InstanceTranslations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of translated packets passing through
           this NAT instance. This value MUST be monotone increasing in
           the periods between updates of
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 9 }

  natv2InstanceAddressMapCreations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of address map entries created by the
           NAT instance, including static mappings. Address map
           creations are also tracked per address pool within the
           instance and per subscriber.

           This value MUST be monotone increasing in
           the periods between updates of
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 10 }

  natv2InstancePortMapCreations  OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of port map entries created by the
           NAT instance, including static mappings. Port map
           creations are also tracked per protocol and address pool
           within the instance and per subscriber.

           This value MUST be monotone increasing in
           the periods between updates of
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 11 }

  natv2InstanceAddressMapEntryLimitDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped rather than
           translated because the packet would have triggered
           the creation of a new address map entry but the limit
           on number of address map entries for the NAT instance
           given by natv2InstanceLimitAddressMapEntries has
           already been reached.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 12 }

  natv2InstancePortMapEntryLimitDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped rather than
           translated because the packet would have triggered
           the creation of a new port map entry but the limit
           on number of port map entries for the NAT instance
           given by natv2InstanceLimitPortMapEntries has
           already been reached.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 13 }

  natv2InstanceSubscriberActiveLimitDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped rather than
           translated because the packet would have triggered the
           creation of a new mapping for a subscriber with no other
           active mappings, but the limit on number of active
           subscribers for the NAT instance given by
           natv2InstanceLimitSubscriberActives has already been
           reached.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 14 }

  natv2InstanceAddressMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because the packet
           would have triggered the creation of a new address map
           entry, but no address could be allocated in the selected
           external realm because all addresses from the selected
           address pool (or the whole realm, if no address pool has
           been configured for that realm) have already been fully
           allocated.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 15 }

  natv2InstancePortMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because the
           packet would have triggered the creation of a new
           port map entry, but no port could be allocated for the
           protocol concerned. The usual case for this will be
           for a NAT instance that supports address pooling and
           the 'paired' pooling behavior recommended by RFC 4787,
           where the internal endpoint has used up all of the
           ports allocated to it for the address it was mapped to
           in the selected address pool in the external realm
           concerned and cannot be given more ports because
           - policy or implementation prevents it from having a
             second address in the same pool, and
           - policy or unavailability prevents it from acquiring
             more ports at its originally assigned address.

           If the NAT instance supports address pooling but its
           pooling behavior is 'arbitrary' (meaning that
           the NAT instance can allocate a new port mapping for
           the given internal endpoint on any address in the
           selected address pool and is not bound to what it has
           already mapped for that endpoint), then this counter
           is incremented when all ports for the protocol concerned
           over the whole of the selected address pool are already
           in use.

           Finally, if no address pools have been configured for the
           external realm concerned, then this counter is incremented
           because all ports for the protocol involved over the whole
           set of addresses available for that external realm are
           already in use.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      REFERENCE
          "Pooling behavior: RFC 4787, end of section 4.1."
      ::= { natv2InstanceEntry 16 }

  natv2InstanceFragmentDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of fragments received by the NAT
           instance but dropped rather than translated. When the NAT
           instance supports the 'Receive Fragment Out of Order'
           capability as required by RFC 4787, this occurs because the
           fragment was received out of order and would be added to the
           queue of fragments awaiting the initial fragment of the
           chain, but the queue has already reached the limit set by
           natv2InstanceLimitsPendingFragments. Counting in other cases
           is specified in the description of
           natv2InstanceFragmentBehavior.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      REFERENCE
          "RFC 4787, section 11."
      ::= { natv2InstanceEntry 17 }

  natv2InstanceOtherResourceFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because of
           unavailability of a resource other than an address or port
           that would have been required to process it. The most likely
           case is where the upper layer protocol in the packet is not
           supported by the NAT instance.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2InstanceEntry 18 }

  natv2InstanceDiscontinuityTime OBJECT-TYPE
      SYNTAX TimeStamp
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Snapshot of the value of the sysUpTime object at the
           beginning of the latest period of continuity of the
           statistical counters associated with this NAT instance."
      ::= { natv2InstanceEntry 19 }

  -- Notification thresholds, disabled by setting to zero

  natv2InstanceThresholdAddressMapEntriesHigh OBJECT-TYPE
      SYNTAX Unsigned32 Integer32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Notification threshold for total number of address map
           entries held by this NAT instance. Whenever
           natv2InstanceAddressMapEntries is updated, if it equals or
           exceeds natv2InstanceThresholdAddressMapEntriesHigh, then
           natv2NotificationInstanceAddressMapEntriesHigh may be
           triggered, unless the notification is disabled by setting
           the threshold to 0. -1. Reporting is subject to the minimum
           inter-notification interval given by
           natv2InstanceNotificationInterval. If multiple notifications
           are triggered during one interval, the agent MUST report
           only the one containing the highest value of
           natv2InstanceAddressMapEntries and discard the others."
      DEFVAL
           { 0 -1 }
      ::= { natv2InstanceEntry 20 }

  natv2InstanceThresholdPortMapEntriesHigh OBJECT-TYPE
      SYNTAX Unsigned32 Integer32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Notification threshold for total number of port map
           entries held by this NAT instance. Whenever
           natv2InstancePortMapEntries is updated, if it equals or
           exceeds natv2InstanceThresholdPortMapEntriesHigh, then
           natv2NotificationInstancePortMapEntriesHigh may be
           triggered, unless the notification is disabled by setting
           the threshold to 0. -1. Reporting is subject to the minimum
           inter-notification interval given by
           natv2InstanceNotificationInterval. If multiple notifications
           are triggered during one interval, the agent MUST report
           only the one containing the highest value of
           natv2InstancePortMapEntries and discard the others."
      DEFVAL
          { 0 -1 }
      ::= { natv2InstanceEntry 21 }

  natv2InstanceNotificationInterval OBJECT-TYPE
      SYNTAX Unsigned32 (1..3600)
      UNITS
          "Seconds"
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Minimum number of seconds (default 10) between successive
           notifications for this NAT instance. Controls the reporting
           of natv2NotificationInstanceAddressMapEntriesHigh and
           natv2NotificationInstancePortMapEntriesHigh."
      DEFVAL
          { 10 }
      ::= { natv2InstanceEntry 22 }

    -- Limits, disabled if set to 0

  natv2InstanceLimitAddressMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Limit on total number of address map entries supported by
           the NAT instance. When natv2InstanceAddressMapEntries has
           reached this limit, subsequent packets that would normally
           trigger creation of a new address map entry will be dropped
           and counted in natv2InstanceAddressMapEntryLimitDrops.
           Warning of an approach to this limit can be achieved by
           setting natv2InstanceThresholdAddressMapEntriesHigh to a
           non-zero value, for example, 80% of the limit. The limit is
           disabled by setting its value to zero (default value). zero.

           For further information please see the descriptions of
           natv2NotificationInstanceAddressMapEntriesHigh and
           natv2InstanceAddressMapEntries."
      DEFVAL
          { 0 }
      ::= { natv2InstanceEntry 23 }

  natv2InstanceLimitPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Limit on total number of port map entries supported by the
           NAT instance. When natv2InstancePortMapEntries has reached
           this limit, subsequent packets that would normally trigger
           creation of a new port map entry will be dropped and counted
           in natv2InstancePortMapEntryLimitDrops. Warning of an
           approach to this limit can be achieved by setting
           natv2InstanceThresholdPortMapEntriesHigh to a non-zero
           value, for example, 80% of the limit. The limit is disabled
           by setting its value to zero (default value). zero.

           For further information please see the descriptions of
           natv2NotificationInstancePortMapEntriesHigh and
           natv2InstancePortMapEntries."
      DEFVAL
          { 0 }
      ::= { natv2InstanceEntry 24 }

  natv2InstanceLimitPendingFragments OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Limit on number of out-of-order fragments received by the
           NAT instance from remote sources and held until head of
           chain appears. While the number of held fragments is at this
           limit, subsequent packets that contain fragments not
           relating to those already held will be dropped and counted
           in natv2InstancePendingFragmentLimitDrops. The limit is
           disabled by setting the value to zero (default value). zero.

           Applicable only when the NAT instance supports 'Receive
           Fragments Out of Order' behavior, leave at default
           otherwise. See the description of
           natv2InstanceFragmentBehavior."
      REFERENCE
           "RFC 4787 Section 11"
      DEFVAL { 0 }
      ::= { natv2InstanceEntry 25 }

  natv2InstanceLimitSubscriberActives OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Limit on number of total number of active subscribers
           supported by the NAT instance. An active subscriber is
           defined as any subscriber with at least one map entry,
           including static mappings. While the number of active
           subscribers is at this limit, subsequent packets that would
           otherwise trigger first mappings for newly active
           subscribers will be dropped and counted in
           natv2InstanceSubscriberActiveLimitDrops. The limit is
           disabled by setting the value to zero (default value)." zero."

      DEFVAL { 0 }
      ::= { natv2InstanceEntry 26 }

  -- Table of counters per upper layer protocol identified by the
  -- packet header and supported by the NAT instance

  natv2ProtocolTable  OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2ProtocolEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Table of protocols with per-protocol counters. Conceptual
           rows of the table are indexed by the combination of the NAT
           instance number and the IANA-assigned upper layer protocol
           number as given by the ProtocolNumber TC and contained in
           the packet IP header. It is up to the agent implementation
           to determine and operate upon only those upper layer
           protocol numbers supported by the NAT instance."
      REFERENCE
          "RFC yyyy Section 3.3.5."
      ::= { natv2MIBInstanceObjects 2 }

  natv2ProtocolEntry OBJECT-TYPE
      SYNTAX Natv2ProtocolEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Per-protocol counters."
      INDEX { natv2ProtocolInstanceIndex,
              natv2ProtocolNumber }
      ::= { natv2ProtocolTable 1 }

  Natv2ProtocolEntry ::=
      SEQUENCE {
          natv2ProtocolInstanceIndex          Natv2InstanceIndex,
          natv2ProtocolNumber                     ProtocolNumber,
  -- State
          natv2ProtocolPortMapEntries             Unsigned32,
  -- Statistics. Discontinuity object from instance table reused here.
          natv2ProtocolTranslations               Counter64,
          natv2ProtocolPortMapCreations           Counter64,
          natv2ProtocolPortMapFailureDrops        Counter64
      }

  natv2ProtocolInstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "NAT instance index. It is up to the implementation to
           determine and operate upon only those values that
           correspond to in-service NAT instances."
      ::= { natv2ProtocolEntry 1 }

  natv2ProtocolNumber OBJECT-TYPE
      SYNTAX ProtocolNumber
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Counters in this conceptual row apply to packets indicating
           the upper layer protocol identified by the value of
           this object. It is up to the implementation to determine and
           operate upon only those values that correspond to protocols
           supported by the NAT instance."
      REFERENCE
          "RFC yyyy Section 3.3.5.
           IANA Protocol Numbers, http://www.iana.org/assignments/
           protocol-numbers/protocol-numbers.xhtml#protocol-numbers-1"
      ::= { natv2ProtocolEntry 2 }

   -- State
  natv2ProtocolPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of entries in the port map table in total
           over the whole NAT instance for a given protocol, including
           static mappings. A port map entry maps from a given external
           realm, address, and port for a given protocol to an internal
           realm, address, and port. This definition includes 'hairpin'
           mappings, where the external realm is the same as the
           internal one. Port map entries are also tracked per
           subscriber, per instance, and per address pool within the
           instance."
      REFERENCE
          "RFC yyyy Section 3.3.5 and Section 3.3.9. Hairpinning:
           RFC 4787 Section 6."
      ::= { natv2ProtocolEntry 3 }

  -- Statistics
  natv2ProtocolTranslations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets translated by the NAT
           instance in either direction for the given protocol.

           This value MUST be monotone increasing in the periods
           between updates of the NAT instance
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2ProtocolEntry 4 }

  natv2ProtocolPortMapCreations  OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of port map entries created by the NAT
           instance for the given protocol.

           This value MUST be monotone increasing in the periods
           between updates of the NAT instance
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      ::= { natv2ProtocolEntry 5 }

  natv2ProtocolPortMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because the packet
           would have triggered the creation of a new port map entry,
           but no port could be allocated for the protocol concerned.
           The usual case for this will be for a NAT instance that
           supports address pooling and the 'paired' pooling behavior
           recommended by RFC 4787, where the internal endpoint has
           used up all of the ports allocated to it for the address it
           was mapped to in the selected address pool in the external
           realm concerned and cannot be given more ports because
           - policy or implementation prevents it from having a
             second address in the same pool, and
           - policy or unavailability prevents it from acquiring
             more ports at its originally assigned address.

           If the NAT instance supports address pooling but its
           pooling behavior is 'arbitrary' (meaning that
           the NAT instance can allocate a new port mapping for
           the given internal endpoint on any address in the
           selected address pool and is not bound to what it has
           already mapped for that endpoint), then this counter
           is incremented when all ports for the protocol concerned
           over the whole of the selected address pool are already
           in use.

           Finally, if the NAT instance has no configured address
           pooling, then this counter is incremented because all
           ports for the protocol concerned over the whole of the
           NAT instance for the external realm concerned are already
           in use.

           This value MUST be monotone increasing in the periods
           between updates of the NAT instance
           natv2InstanceDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2InstanceDiscontinuityTime."
      REFERENCE
          "RFC 4787, end of section 4.1."
      ::= { natv2ProtocolEntry 6 }

  -- pools

  natv2PoolTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2PoolEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
         "Table of address pools, applicable only if these are
          supported by the NAT instance. An address pool is a set of
          addresses and ports in a particular realm, available for
          assignment to the 'external' portion of a mapping. Where more
          than one pool has been configured for the realm, policy
          determines which subscribers and/or services are mapped to
          which pool. natv2PoolTable provides basic information, state,
          statistics, and two notification thresholds for each pool.
          natv2PoolRangeTable is an expansion table for natv2PoolTable
          that identifies particular address ranges allocated to the
          pool."
      REFERENCE
          "RFC yyyy Section 3.3.6."

      ::= { natv2MIBInstanceObjects 3 }

  natv2PoolEntry OBJECT-TYPE
      SYNTAX Natv2PoolEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Entry in the table of address pools."
      INDEX { natv2PoolInstanceIndex, natv2PoolIndex }
      ::= { natv2PoolTable 1 }

  Natv2PoolEntry ::=
      SEQUENCE {
  -- Index
           natv2PoolInstanceIndex                 Natv2InstanceIndex,
           natv2PoolIndex                         Natv2PoolIndex,
  -- Configuration
           natv2PoolRealm                         SnmpAdminString,
           natv2PoolAddressType                   InetAddressType,
           natv2PoolMinimumPort                   InetPortNumber,
           natv2PoolMaximumPort                   InetPortNumber,
  -- State
           natv2PoolAddressMapEntries             Unsigned32,
           natv2PoolPortMapEntries                Unsigned32,
  -- Statistics and discontinuity time
           natv2PoolAddressMapCreations           Counter64,
           natv2PoolPortMapCreations              Counter64,
           natv2PoolAddressMapFailureDrops        Counter64,
           natv2PoolPortMapFailureDrops           Counter64,
           natv2PoolDiscontinuityTime             TimeStamp,
  -- Notification thresholds and objects returned by notifications
           natv2PoolThresholdUsageLow             Integer32,
           natv2PoolThresholdUsageHigh            Unsigned32,            Integer32,
           natv2PoolNotifiedPortMapEntries        Unsigned32,
           natv2PoolNotifiedPortMapProtocol       ProtocolNumber,
           natv2PoolNotificationInterval          Unsigned32
      }

  natv2PoolInstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "NAT instance index. It is up to the agent implementation
           to determine and operate upon only those values that
           correspond to in-service NAT instances."
      ::= { natv2PoolEntry 1 }

  natv2PoolIndex OBJECT-TYPE
      SYNTAX Natv2PoolIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of an address pool, unique for a given NAT instance.
           It is up to the agent implementation to determine and
           operate upon only those values that correspond to
           provisioned pools."
      ::= { natv2PoolEntry 2 }

  -- configuration
  natv2PoolRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE (0..32))
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Address realm to which this pool's addresses belong."
      REFERENCE
          "Address realms are discussed in Section 3.3.3 of
           RFC yyyy. Primary reference is RFC 2663 Section 2.1."
      ::= { natv2PoolEntry 3 }

  natv2PoolAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-create
      STATUS current
      DESCRIPTION
          "Address type supplied by this address pool. This will be the
           same for all pools in a given realm (by definition of an
           address realm). Values other than ipv4(1) or ipv6(2) would
           be unexpected."
      REFERENCE
          "InetAddressType in RFC 4001."
      ::= { natv2PoolEntry 4 }

  natv2PoolMinimumPort OBJECT-TYPE
      SYNTAX InetPortNumber
      MAX-ACCESS read-create
      STATUS current
      DESCRIPTION
          "Minimum port number of the range that can be allocated in
           this pool. Applies to all protocols supported by the NAT
           instance."
      REFERENCE
          "InetPortNumber in RFC 4001."
      ::= { natv2PoolEntry 5 }

  natv2PoolMaximumPort OBJECT-TYPE
      SYNTAX InetPortNumber
      MAX-ACCESS read-create
      STATUS current
      DESCRIPTION
          "Maximum port number of the range that can be allocated in
           this pool. Applies to all protocols supported by the NAT
           instance."
      REFERENCE
          "InetPortNumber in RFC 4001."
      ::= { natv2PoolEntry 6 }

  -- State
  natv2PoolAddressMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of address map entries using external
           addresses drawn from this pool, including static mappings.
           This definition includes 'hairpin' mappings, where the
           external realm is the same as the internal one. Address map
           entries are also tracked per subscriber and per instance."
      REFERENCE
          "RFC yyyy Section 3.3.8. Hairpinning: RFC 4787 section 6."
      ::= { natv2PoolEntry 7 }

  natv2PoolPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The current number of entries in the port map table using
           external addresses and ports drawn from this pool, including
           static mappings. This definition includes 'hairpin'
           mappings, where the external realm is the same as the
           internal one. Port map entries are also tracked per
           subscriber, per instance, and per protocol within the
           instance."
      REFERENCE
          "RFC yyyy Section 3.3.9. Hairpinning: RFC 4787 Section 6."
      ::= { natv2PoolEntry 8 }

  -- Statistics and discontinuity time
  natv2PoolAddressMapCreations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of address map entries created in this
           pool, including static mappings. Address map entries are
           also tracked per instance and per subscriber.

           This value MUST be monotone increasing in
           the periods between updates of the entity's
           natv2PoolDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2PoolDiscontinuityTime."
      ::= { natv2PoolEntry 9 }

  natv2PoolPortMapCreations OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of port map entries created in this
           pool, including static mappings. Port map entries are also
           tracked per instance, per protocol, and per subscriber.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2PoolDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2PoolDiscontinuityTime."
      ::= { natv2PoolEntry 10 }

  natv2PoolAddressMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets originated by the
           subscriber that were dropped because the packet would have
           triggered the creation of a new address map entry, but no
           address could be allocated from this address pool because
           all addresses in the pool have already been fully allocated.
           Counters of this event are also provided per instance, per
           protocol and per subscriber.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2PoolDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2PoolDiscontinuityTime."
      ::= { natv2PoolEntry 11 }

  natv2PoolPortMapFailureDrops OBJECT-TYPE
      SYNTAX Counter64
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The cumulative number of packets dropped because the packet
           would have triggered the creation of a new port map entry,
           but no port could be allocated for the protocol concerned.
           The usual case for this will be for a NAT instance that
           supports the 'paired' pooling behavior recommended by RFC
           4787, where the internal endpoint has used up all of the
           ports allocated to it for the address it was mapped to in
           this pool and cannot be given more ports because
           - policy or implementation prevents it from having a
             second address in the same pool, and
           - policy or unavailability prevents it from acquiring
             more ports at its originally assigned address.

           If the NAT instance pooling behavior is 'arbitrary' (meaning
           that the NAT instance can allocate a new port mapping for
           the given internal endpoint on any address in the selected
           address pool and is not bound to what it has already mapped
           for that endpoint), then this counter is incremented when
           all ports for the protocol concerned over the whole of this
           address pool are already in use.

           This value MUST be monotone increasing in the periods
           between updates of the entity's
           natv2PoolDiscontinuityTime. If a manager detects a
           change in the latter since the last time it sampled this
           counter, it SHOULD NOT make use of the difference between
           the latest value of the counter and any value retrieved
           before the new value of natv2PoolDiscontinuityTime."
      REFERENCE
          "Pooling behavior: RFC 4787, end of section 4.1."
      ::= { natv2PoolEntry 12 }

  natv2PoolDiscontinuityTime OBJECT-TYPE
      SYNTAX TimeStamp
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Snapshot of the value of the sysUpTime object at the
           beginning of the latest period of continuity of the
           statistical counters associated with this address
           pool. This MUST be initialized when the address pool
           is configured and MUST be updated whenever the port
           or address ranges allocated to the pool change."
      ::= { natv2PoolEntry 14 13 }

  -- Notification thresholds and objects returned by notifications
  natv2PoolThresholdUsageLow OBJECT-TYPE
      SYNTAX Integer32 (-1|0..100)
      UNITS "Percent"
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Threshold for reporting low utilization of the address pool.
           Utilization at a given instant is calculated as the
           percentage of ports allocated in port map entries for the
           most-used protocol at that instant. If utilization is less
           than or equal to natv2PoolThresholdUsageLow, an instance of
           natv2NotificationPoolUsageLow may be triggered, unless
           disabled by setting it to -1.  Note the difference from the
           disabling setting for other notifications. Reporting is
           subject to the per-pool notification interval given by
           natv2PoolNotificationInterval. If multiple notifications are
           triggered during one interval, the agent MUST report only
           the one with the lowest value of
           natv2PoolNotifiedPortMapEntries and discard the others.

           Implementation note: the percentage specified by this object
           can be converted to a number of port map entries at
           configuration time (after port and address ranges have been
           configured or reconfigured) and compared to the current
           value of natv2PoolNotifiedPortMapEntries."
      REFERENCE
          "RFC yyyy Section 3.1.2 and Section 3.3.6."
      DEFVAL { -1 }
      ::= { natv2PoolEntry 15 14 }

  natv2PoolThresholdUsageHigh OBJECT-TYPE
      SYNTAX Unsigned32 (0..100) Integer32 (-1|0..100)
      UNITS "Percent"
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Threshold for reporting high utilization of the address
           pool. Utilization at a given instant is calculated as the
           percentage of ports allocated in port map entries for the
           most-used protocol at that instant.  If utilization is
           greater than or equal to natv2PoolThresholdUsageHigh, an
           instance of natv2NotificationPoolUsageHigh may be triggered,
           unless disabled by setting it to 0. -1.

           Reporting is subject to the per-pool notification interval
           given by natv2PoolNotificationInterval. If multiple
           notifications are triggered during one interval, the agent
           MUST report only the one with the highest value of
           natv2PoolNotifiedPortMapEntries and discard the others. In
           the rare case where both upper and lower thresholds
           are crossed in the same interval, the agent MUST report only
           the upper threshold notification.

           Implementation note: the percentage specified by this object
           can be converted to a number of port map entries at
           configuration time (after port and address ranges have been
           configured or reconfigured) and compared to the current
           value of natv2PoolNotifiedPortMapEntries."
      DEFVAL { 0 -1 }
      ::= { natv2PoolEntry 16 15 }

  natv2PoolNotifiedPortMapEntries OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS accessible-for-notify
      STATUS current
      DESCRIPTION
          "Number of port map entries using addresses and ports from
           this address pool for the most-used protocol at a given
           instant. One of the objects returned by
           natv2NotificationPoolUsageLow and
           natv2NotificationPoolUsageHigh."
      ::= { natv2PoolEntry 17 16 }

  natv2PoolNotifiedPortMapProtocol OBJECT-TYPE
      SYNTAX ProtocolNumber
      MAX-ACCESS accessible-for-notify
      STATUS current
      DESCRIPTION
          "The most-used protocol (i.e., with the largest number of
           port map entries) mapped into this address pool at a given
           instant. One of the objects returned by
           natv2NotificationPoolUsageLow and
           natv2NotificationPoolUsageHigh."
      ::= { natv2PoolEntry 18 17 }

  natv2PoolNotificationInterval OBJECT-TYPE
      SYNTAX Unsigned32 (1..3600)
      UNITS
          "Seconds"
      MAX-ACCESS read-write
      STATUS current
      DESCRIPTION
          "Minimum number of seconds (default 20) between successive
           notifications for this address pool. Controls the generation
           of  natv2NotificationPoolUsageLow and
           natv2NotificationPoolUsageHigh."
      DEFVAL
          { 20 }
      ::= { natv2PoolEntry 19 18 }

  natv2PoolRangeTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2PoolRangeEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "This table contains address ranges used by pool entries.
           It is an expansion of natv2PoolTable."
      REFERENCE
          "RFC yyyy <xref target='poolRangeTable'/>."
      ::= { natv2MIBInstanceObjects 4 }

  natv2PoolRangeEntry OBJECT-TYPE
      SYNTAX Natv2PoolRangeEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "NAT pool address range."
      INDEX {
           natv2PoolRangeInstanceIndex,
           natv2PoolRangePoolIndex,
           natv2PoolRangeRowIndex
      }
      ::= { natv2PoolRangeTable 1 }

  Natv2PoolRangeEntry ::=
      SEQUENCE {
          natv2PoolRangeInstanceIndex    Natv2InstanceIndex,
          natv2PoolRangePoolIndex        Natv2PoolIndex,
          natv2PoolRangeRowIndex         Unsigned32,
          natv2PoolRangeBegin            InetAddress,
          natv2PoolRangeEnd              InetAddress
      }

  natv2PoolRangeInstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of the NAT instance on which the address pool and this
           address range are configured. See Natv2InstanceIndex."
      ::= { natv2PoolRangeEntry 1 }

  natv2PoolRangePoolIndex OBJECT-TYPE
      SYNTAX Natv2PoolIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of the address pool to which this address range
           belongs. See Natv2PoolIndex."
      ::= { natv2PoolRangeEntry 2 }

  natv2PoolRangeRowIndex OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Row index for successive range entries for the same
           address pool."
      ::= { natv2PoolRangeEntry 3 }

  natv2PoolRangeBegin OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Lowest address included in this range. The type of address
           (IPv4 or IPv6) is given by natv2PoolAddressType
           in natv2PoolTable."
      ::= { natv2PoolRangeEntry 4 }

  natv2PoolRangeEnd OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Highest address included in this range. The type of address
           (IPv4 or IPv6) is given by natv2PoolAddressType
           in natv2PoolTable."
      ::= { natv2PoolRangeEntry 5 }

  -- indexed mapping tables

  -- Address Map Table. Mapped from internal to external address.

  natv2AddressMapTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2AddressMapEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Table of mappings from internal to external address. By
           definition, this is a snapshot of NAT instance state at a
           given moment. Indexed by NAT instance, internal realm, and
           internal address in that realm. Provides the mapped external
           address and, depending on implementation support, identifies
           the address pool from which the external address and port
           were taken and the index of the subscriber to which the
           mapping has been allocated.

           In the case of DS-Lite [RFC 6333], the indexing realm and
           address are those of the IPv6 encapsulation rather than the
           IPv4 inner packet."
      REFERENCE
          "RFC yyyy Section 3.3.8. DS-Lite: RFC 6333"
      ::= { natv2MIBInstanceObjects 5 }

  natv2AddressMapEntry OBJECT-TYPE
      SYNTAX Natv2AddressMapEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Mapping from internal to external address."
      INDEX { natv2AddressMapInstanceIndex,
              natv2AddressMapInternalRealm,
              natv2AddressMapInternalAddressType,
              natv2AddressMapInternalAddress,
              natv2AddressMapRowIndex }
      ::= { natv2AddressMapTable 1 }

  Natv2AddressMapEntry ::=
      SEQUENCE {
          natv2AddressMapInstanceIndex       Natv2InstanceIndex,
          natv2AddressMapInternalRealm       SnmpAdminString,
          natv2AddressMapInternalAddressType  InetAddressType,
          natv2AddressMapInternalAddress      InetAddress,
          natv2AddressMapRowIndex            Unsigned32,
          natv2AddressMapInternalMappedAddressType InetAddressType,
          natv2AddressMapInternalMappedAddress     InetAddress,
          natv2AddressMapExternalRealm       SnmpAdminString,
          natv2AddressMapExternalAddressType InetAddressType,
          natv2AddressMapExternalAddress     InetAddress,
          natv2AddressMapExternalPoolIndex   Natv2PoolIndexOrZero,
          natv2AddressMapSubscriberIndex     Natv2SubscriberIndexOrZero
      }

  natv2AddressMapInstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of the NAT instance that generated this address map."
      ::= { natv2AddressMapEntry 1 }

  natv2AddressMapInternalRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE(0..32))
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Realm to which the internal address belongs. In most cases
           this is the realm defining the address space of the packet
           being translated. However, in the case of DS-Lite [RFC
           6333], this realm defines the IPv6 outer header address
           space. It is the combination of that outer header and
           the inner IPv4 packet header that is remapped to the
           external address and realm. The corresponding IPv4 realm is
           restricted in scope to the tunnel, so there is no point in
           identifying it. The mapped IPv4 address will normally be the
           well-known value 192.0.0.2, or at least lie in the reserved
           192.0.0.0/29 range.

           If natv2AddressMapSubscriberIndex in this table is a valid
           subscriber index (i.e., greater than zero), then the value
           of natv2AddressMapInternalRealm MUST be identical to the
           value of natv2SubscriberRealm associated with that index."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2AddressMapEntry 2 }

  natv2AddressMapInternalAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Address type in the header of packets on the
           interior side of this mapping. Any value other than ipv4(1)
           or ipv6(2) would be unexpected.

           In the DS-Lite case, the address type is ipv6(2)."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel source
           address in the NAT mapping tables."
      ::= { natv2AddressMapEntry 3 }

  natv2AddressMapInternalAddress OBJECT-TYPE
      SYNTAX InetAddress (SIZE (0..16))
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Source address of packets originating from the interior
           of the association provided by this mapping.

           In the case of DS-Lite [RFC 6333], this is the IPv6 tunnel
           source address.  The mapping in this case is considered to
           be from the combination of the IPv6 tunnel source address
           natv2AddressMapInternalRealmAddress and the well-known IPv4
           inner source address natv2AddressMapInternalMappedAddress to
           the external address."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2AddressMapEntry 4 }

  natv2AddressMapRowIndex OBJECT-TYPE
      SYNTAX Unsigned32
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of a conceptual row corresponding to a mapping of the
           given internal realm and address to a single external realm
           and address. Multiple rows will be present because of a
           promiscuous external address selection policy, policies
           associating the same internal address with different address
           pools, or because the same internal realm-address
           combination is communicating with multiple external address
           realms."
      ::= { natv2AddressMapEntry 5 }

  natv2AddressMapInternalMappedAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Internal address type actually translated by this mapping.
           Any value other than ipv4(1) or ipv6(2) would be unexpected.
           In the general case, this is the same as given by
           natv2AddressMapInternalRealmAddressType. In the
           tunneled case it is the address type used in the
           encapsulated packet header. In particular, in the DS-Lite
           case, the mapped address type is ipv4(1)."
      REFERENCE
          "DS-Lite: RFC 6333."
      ::= { natv2AddressMapEntry 6 }

  natv2AddressMapInternalMappedAddress OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Internal address actually translated by this mapping. In the
           general case, this is the same as
           natv2AddressMapInternalRealmAddress. In the case of DS-Lite
           [RFC 6333], this is the source address of the encapsulated
           IPv4 packet, normally lying the well-known range
           192.0.0.0/29. The mapping in this case is considered to be
           from the combination of the IPv6 tunnel source address
           natv2AddressMapInternalRealmAddress and the well-known IPv4
           inner source address natv2AddressMapInternalMappedAddress to
           the external address."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2AddressMapEntry 7 }

  natv2AddressMapExternalRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE(0..32))
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "External address realm to which this mapping maps the
           internal address. This can be the same as the internal realm
           in the case of a 'hairpin' connection, but otherwise will be
           different."
      ::= { natv2AddressMapEntry 8 }

  natv2AddressMapExternalAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Address type for the external realm. Any value other than
           ipv4(1) or ipv6(2) would be unexpected."
      ::= { natv2AddressMapEntry 9 }

  natv2AddressMapExternalAddress OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "External address to which the internal address is mapped.

           In the DS-Lite case, the mapping is from the combination of
           the internal IPv6 tunnel source address as presented in this
           table and the well-known IPv4 source address of the
           encapsulated IPv4 packet."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2AddressMapEntry 10 }

  natv2AddressMapExternalPoolIndex OBJECT-TYPE
      SYNTAX Natv2PoolIndexOrZero
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Index of the address pool in the external realm from which
           the mapped external address given in
           natv2AddressMapExternalAddress was taken. Zero if the
           implementation does not support address pools but has chosen
           to support this object, or if no pool was configured for the
           given external realm."
      ::= { natv2AddressMapEntry 11 }

  natv2AddressMapSubscriberIndex OBJECT-TYPE
      SYNTAX Natv2SubscriberIndexOrZero
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Index of the subscriber to which this address mapping
           applies, or zero if no subscribers are configured on
           this NAT instance."
      ::= { natv2AddressMapEntry 12 }

  -- natv2PortMapTable
  natv2PortMapTable OBJECT-TYPE
      SYNTAX SEQUENCE OF Natv2PortMapEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Table of port map entries indexed by NAT instance, protocol,
           and external realm and address. A port map entry associates
           an internal upper layer protocol endpoint with an endpoint
           for the same protocol in the given external realm. By
           definition, this is a snapshot of NAT instance state at a
           given moment. The table provides the basic mapping
           information.

           In the case of DS-Lite [RFC 6333], the table provides the
           internal IPv6 tunnel source address in
           natv2PortMapInternalRealmAddress and the IPv4 source address
           of the encapsulated packet that is actually translated in
           natv2PortMapInternalMappedAddress. In the general (non-DS-
           Lite) case, those two objects will have the same value."
      REFERENCE
          "RFC yyyy Section 3.3.9. DS-Lite: RFC 6333, Section 5.7 for
           well-known addresses and Section 6.6 on the need to have the
           IPv6 tunnel address in the NAT mapping tables."
      ::= { natv2MIBInstanceObjects 6 }

  natv2PortMapEntry OBJECT-TYPE
      SYNTAX Natv2PortMapEntry
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "A single NAT mapping."
      INDEX { natv2PortMapInstanceIndex,
              natv2PortMapProtocol,
              natv2PortMapExternalRealm,
              natv2PortMapExternalAddressType,
              natv2PortMapExternalAddress,
              natv2PortMapExternalPort }
      ::= { natv2PortMapTable 1 }

  Natv2PortMapEntry ::=
      SEQUENCE {
          natv2PortMapInstanceIndex        Natv2InstanceIndex,
          natv2PortMapProtocol             ProtocolNumber,
          natv2PortMapExternalRealm        SnmpAdminString,
          natv2PortMapExternalAddressType  InetAddressType,
          natv2PortMapExternalAddress      InetAddress,
          natv2PortMapExternalPort         InetPortNumber,
          natv2PortMapInternalRealm        SnmpAdminString,
          natv2PortMapInternalAddressType  InetAddressType,
          natv2PortMapInternalAddress      InetAddress,
          natv2PortMapInternalMappedAddressType InetAddressType,
          natv2PortMapInternalMappedAddress     InetAddress,
          natv2PortMapInternalPort         InetPortNumber,
          natv2PortMapExternalPoolIndex    Natv2PoolIndexOrZero,
          natv2PortMapSubscriberIndex      Natv2SubscriberIndexOrZero
      }

  natv2PortMapInstanceIndex OBJECT-TYPE
      SYNTAX Natv2InstanceIndex
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Index of the NAT instance that created this port map entry."
      ::= { natv2PortMapEntry 1 }

  natv2PortMapProtocol OBJECT-TYPE
      SYNTAX ProtocolNumber
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "The map entry's upper layer protocol number."
      ::= { natv2PortMapEntry 2 }

  natv2PortMapExternalRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE(0..32))
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "The realm to which natv2PortMapExternalAddress belongs."
      ::= { natv2PortMapEntry 3 }

  natv2PortMapExternalAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "Address type for the external realm. A value other
           than ipv4(1) or ipv6(2) would be unexpected."
      ::= { natv2PortMapEntry 4 }

  natv2PortMapExternalAddress OBJECT-TYPE
      SYNTAX InetAddress (SIZE (0..16))
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "The mapping's assigned external address. (This address is
           taken from the address pool identified by
           natv2PortMapExternalPoolIndex, if the implementation
           supports address pools and pools are configured for the
           given external realm.) This is the source address for
           translated outgoing packets."

      ::= { natv2PortMapEntry 5 }

  natv2PortMapExternalPort OBJECT-TYPE
      SYNTAX InetPortNumber
      MAX-ACCESS not-accessible
      STATUS current
      DESCRIPTION
          "The mapping's assigned external port number. This is the
           source port for translated outgoing packets. If the internal
           port number given by natv2PortMapInternalPort is zero this
           value MUST also be zero. Otherwise this MUST be a non-zero
           value."
      ::= { natv2PortMapEntry 6 }

  natv2PortMapInternalRealm OBJECT-TYPE
      SYNTAX SnmpAdminString (SIZE(0..32))
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The realm to which natv2PortMapInternalRealmAddress belongs.
           In the general case, this realm contains the address that is
           being translated. In the DS-Lite [RFC 6333] case, this realm
           defines the IPv6 address space from which the tunnel source
           address is taken. The realm of the encapsulated IPv4 address
           is restricted in scope to the tunnel, so there is no point
           in identifying it separately."
      REFERENCE
          "RFC 6333 DS-Lite."
      ::= { natv2PortMapEntry 7 }

  natv2PortMapInternalAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Address type for addresses in the realm identified by
           natv2PortMapInternalRealm."
      ::= { natv2PortMapEntry 8 }

  natv2PortMapInternalAddress OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Source address for packets received under this mapping on
           the internal side of the NAT instance. In the general case
           this address is the same as the address given in
           natv2PortMapInternalMappedAddress. In the DS-Lite case,
           natv2PortMapInternalAddress is the IPv6 tunnel source
           address."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2PortMapEntry 9 }

  natv2PortMapInternalMappedAddressType OBJECT-TYPE
      SYNTAX InetAddressType
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Internal address type actually translated by this mapping.
           Any value other than ipv4(1) or ipv6(2) would be unexpected.
           In the general case, this is the same as given by
           natv2AddressMapInternalAddressType. In the DS-Lite
           case, the address type is ipv4(1)."
      REFERENCE
          "DS-Lite: RFC 6333."
     ::= { natv2PortMapEntry 10 }

  natv2PortMapInternalMappedAddress OBJECT-TYPE
      SYNTAX InetAddress
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Internal address actually translated by this mapping. In the
           general case, this is the same as
           natv2PortMapInternalRealmAddress. In the case of DS-Lite
           [RFC 6333], this is the source address of the encapsulated
           IPv4 packet, normally selected from the well-known range
           192.0.0.0/29. The mapping in this case is considered to be
           from the external address to the combination of the IPv6
           tunnel source address natv2PortMapInternalRealmAddress and
           the well-known IPv4 inner source address
           natv2PortMapInternalMappedAddress."
      REFERENCE
          "DS-Lite: RFC 6333, Section 5.7 for well-known addresses and
           Section 6.6 on the need to have the IPv6 tunnel address in
           the NAT mapping tables."
      ::= { natv2PortMapEntry 11 }

  natv2PortMapInternalPort OBJECT-TYPE
      SYNTAX InetPortNumber
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "The mapping's internal port number. If this is zero, ports
           are not translated (i.e., the NAT instance is a pure NAT
           rather than a NAPT)."
      ::= { natv2PortMapEntry 12 }

  natv2PortMapExternalPoolIndex OBJECT-TYPE
      SYNTAX Natv2PoolIndexOrZero
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Identifies the address pool from which the external address
           in this port map entry was taken. Zero if the implementation
           does not support address pools but has chosen to support
           this object, or if no pools are configured for the given
           external realm."
      ::= { natv2PortMapEntry 13 }

  natv2PortMapSubscriberIndex OBJECT-TYPE
      SYNTAX Natv2SubscriberIndexOrZero
      MAX-ACCESS read-only
      STATUS current
      DESCRIPTION
          "Subscriber using this map entry. Zero if the implementation
           does not support subscribers but has chosen to support
           this object."
      ::= { natv2PortMapEntry 14 }

  -- Conformance section. Specifies three cumulatively more extensive
  -- applications: basic NAT, pooled NAT, and carrier grade NAT

  natv2MIBConformance OBJECT IDENTIFIER ::= { natv2MIB 3 }

  natv2MIBCompliances OBJECT IDENTIFIER ::= { natv2MIBConformance 1 }
  natv2MIBGroups      OBJECT IDENTIFIER ::= { natv2MIBConformance 2 }

  natv2MIBBasicCompliance MODULE-COMPLIANCE
      STATUS current
      DESCRIPTION
          "Describes the requirements for conformance to the basic NAT
           application of NATv2 MIB."
      MODULE  -- this module
          MANDATORY-GROUPS { natv2BasicNotificationGroup,
                             natv2BasicInstanceLevelGroup
                           }
          GROUP  natv2BasicNotificationGroup
          DESCRIPTION
              "The natv2BasicNotificationGroup is mandatory for all
               NAT applications."
          GROUP  natv2BasicInstanceLevelGroup
          DESCRIPTION
              "The natv2BasicInstanceLevelGroup is mandatory for all
               NAT applications."
      ::= { natv2MIBCompliances 1 }

  natv2MIBPooledNATCompliance MODULE-COMPLIANCE
      STATUS current
      DESCRIPTION
          "Describes the requirements for conformance to the pooled NAT
           application of NATv2-MIB."
      MODULE  -- this module
          MANDATORY-GROUPS { natv2BasicNotificationGroup,
                             natv2BasicInstanceLevelGroup,
                             natv2PooledNotificationGroup,
                             natv2PooledInstanceLevelGroup
                           }
          GROUP  natv2BasicNotificationGroup
          DESCRIPTION
              "The natv2BasicNotificationGroup is mandatory for all
               NAT applications."
          GROUP  natv2BasicInstanceLevelGroup
          DESCRIPTION
              "The natv2BasicInstanceLevelGroup is mandatory for all
               NAT applications."
          GROUP  natv2PooledNotificationGroup
          DESCRIPTION
              "The natv2PooledNotificationGroup is mandatory for
               the pooled and CGN applications."
          GROUP  natv2PooledInstanceLevelGroup
          DESCRIPTION
              "The natv2PooledInstanceLevelGroup is mandatory for
               the pooled and CGN applications."
      ::= { natv2MIBCompliances 2 }

  natv2MIBCGNCompliance MODULE-COMPLIANCE
      STATUS current
      DESCRIPTION
          "Describes the requirements for conformance to the
           carrier grade NAT application of NATv2-MIB."
      MODULE  -- this module
          MANDATORY-GROUPS { natv2BasicNotificationGroup,
                             natv2BasicInstanceLevelGroup,
                             natv2PooledNotificationGroup,
                             natv2PooledInstanceLevelGroup,
                             natv2CGNNotificationGroup,
                             natv2CGNDeviceLevelGroup,
                             natv2CGNInstanceLevelGroup
                           }
          GROUP  natv2BasicNotificationGroup
          DESCRIPTION
              "The natv2BasicNotificationGroup is mandatory for all
               NAT applications."
          GROUP  natv2BasicInstanceLevelGroup
          DESCRIPTION
              "The natv2BasicInstanceLevelGroup is mandatory for all
               NAT applications."
          GROUP  natv2PooledNotificationGroup
          DESCRIPTION
              "The natv2PooledNotificationGroup is mandatory for
               the pooled and CGN applications."
          GROUP  natv2PooledInstanceLevelGroup
          DESCRIPTION
              "The natv2PooledInstanceLevelGroup is mandatory for
               the pooled and CGN applications."
          GROUP  natv2CGNNotificationGroup
          DESCRIPTION
              "The natv2CGNNotificationGroup is mandatory
               for the carrier grade NAT application."
          GROUP  natv2CGNDeviceLevelGroup
          DESCRIPTION
              "The natv2CGNDeviceLevelGroup is mandatory
               for the carrier grade NAT application."
          GROUP  natv2CGNInstanceLevelGroup
          DESCRIPTION
              "The natv2CGNInstanceLevelGroup is mandatory
               for the carrier grade NAT application."
      ::= { natv2MIBCompliances 3 }

  -- Groups

  natv2BasicNotificationGroup NOTIFICATION-GROUP
      NOTIFICATIONS {
           natv2NotificationInstanceAddressMapEntriesHigh,
           natv2NotificationInstancePortMapEntriesHigh
      }
      STATUS  current
      DESCRIPTION
          "Notifications that MUST be supported by all NAT
           applications."
      ::= { natv2MIBGroups 1 }

  natv2BasicInstanceLevelGroup OBJECT-GROUP
      OBJECTS {
  -- from natv2InstanceTable
                natv2InstanceAlias,
                natv2InstancePortMappingBehavior,
                natv2InstanceFilteringBehavior,
                natv2InstanceFragmentBehavior,
                natv2InstanceAddressMapEntries,
                natv2InstancePortMapEntries,
                natv2InstanceTranslations,
                natv2InstanceAddressMapCreations,
                natv2InstanceAddressMapEntryLimitDrops,
                natv2InstanceAddressMapFailureDrops,
                natv2InstancePortMapCreations,
                natv2InstancePortMapEntryLimitDrops,
                natv2InstancePortMapFailureDrops,
                natv2InstanceFragmentDrops,
                natv2InstanceOtherResourceFailureDrops,
                natv2InstanceDiscontinuityTime,
                natv2InstanceThresholdAddressMapEntriesHigh,
                natv2InstanceThresholdPortMapEntriesHigh,
                natv2InstanceNotificationInterval,
                natv2InstanceLimitAddressMapEntries,
                natv2InstanceLimitPortMapEntries,
                natv2InstanceLimitPendingFragments,
  -- from natv2ProtocolTable
                natv2ProtocolPortMapEntries,
                natv2ProtocolTranslations,
                natv2ProtocolPortMapCreations,
                natv2ProtocolPortMapFailureDrops,
  -- from natv2AddressMapTable
                natv2AddressMapExternalRealm,
                natv2AddressMapExternalAddressType,
                natv2AddressMapExternalAddress,
  -- from natv2PortMapTable
                natv2PortMapInternalRealm,
                natv2PortMapInternalAddressType,
                natv2PortMapInternalAddress,
                natv2PortMapInternalPort
              }
      STATUS current
      DESCRIPTION
          "Per-instance objects that MUST be supported by
           implementations of all NAT applications."

      ::= { natv2MIBGroups 2 }

  natv2PooledNotificationGroup NOTIFICATION-GROUP
      NOTIFICATIONS {
           natv2NotificationPoolUsageLow,
           natv2NotificationPoolUsageHigh
                    }
      STATUS  current
      DESCRIPTION
          "Notifications that MUST be supported by pooled and
           carrier-grade NAT applications."
      ::= { natv2MIBGroups 3 }

  natv2PooledInstanceLevelGroup OBJECT-GROUP
      OBJECTS {
  -- from natv2InstanceTable
                      natv2InstancePoolingBehavior,
  -- from natv2PoolTable
                      natv2PoolRealm,
                      natv2PoolAddressType,
                      natv2PoolMinimumPort,
                      natv2PoolMaximumPort,
                      natv2PoolAddressMapEntries,
                      natv2PoolPortMapEntries,
                      natv2PoolAddressMapCreations,
                      natv2PoolPortMapCreations,
                      natv2PoolAddressMapFailureDrops,
                      natv2PoolPortMapFailureDrops,
                      natv2PoolDiscontinuityTime,
                      natv2PoolThresholdUsageLow,
                      natv2PoolThresholdUsageHigh,
                      natv2PoolNotifiedPortMapEntries,
                      natv2PoolNotifiedPortMapProtocol,
                      natv2PoolNotificationInterval,
  -- from natv2PoolRangeTable
                      natv2PoolRangeBegin,
                      natv2PoolRangeEnd,
  -- from natv2AddressMapTable
                      natv2AddressMapExternalPoolIndex,
  -- from natv2PortMapTable
                      natv2PortMapExternalPoolIndex
              }
      STATUS current
      DESCRIPTION
          "Per-instance objects that MUST be supported by
           implementations of the pooled and carrier grade
           NAT applications."
      ::= { natv2MIBGroups 4 }

  natv2CGNNotificationGroup NOTIFICATION-GROUP
      NOTIFICATIONS {
           natv2NotificationSubscriberPortMappingEntriesHigh
      }
      STATUS  current
      DESCRIPTION
          "Notification that MUST be supported by implementations
           of the carrier grade NAT application."
      ::= { natv2MIBGroups 5 }

  natv2CGNDeviceLevelGroup OBJECT-GROUP
      OBJECTS {
  -- from table natv2SubscriberTable
                natv2SubscriberInternalRealm,
                natv2SubscriberInternalPrefixType,
                natv2SubscriberInternalPrefix,
                natv2SubscriberInternalPrefixLength,
                natv2SubscriberAddressMapEntries,
                natv2SubscriberPortMapEntries,
                natv2SubscriberTranslations,
                natv2SubscriberAddressMapCreations,
                natv2SubscriberPortMapCreations,
                natv2SubscriberAddressMapFailureDrops,
                natv2SubscriberPortMapFailureDrops,
                natv2SubscriberDiscontinuityTime,
                natv2SubscriberLimitPortMapEntries,
                natv2SubscriberThresholdPortMapEntriesHigh,
                natv2SubscriberNotificationInterval
              }
      STATUS current
      DESCRIPTION
          "Device-level objects that MUST be supported by the
           carrier-grade NAT application."
      ::= { natv2MIBGroups 6 }

  natv2CGNInstanceLevelGroup OBJECT-GROUP
      OBJECTS {
     -- from natv2InstanceTable
                natv2InstanceSubscriberActiveLimitDrops,
                natv2InstanceLimitSubscriberActives,
     -- from natv2AddressMapTable
                natv2AddressMapInternalMappedAddressType,
                natv2AddressMapInternalMappedAddress,
                natv2AddressMapSubscriberIndex,
     -- from natv2PortMapTable
                natv2PortMapInternalMappedAddressType,
                natv2PortMapInternalMappedAddress,
                natv2PortMapSubscriberIndex

              }
      STATUS current
      DESCRIPTION
          "Per-instance objects that MUST be supported by the
           carrier grade NAT application."
      ::= { natv2MIBGroups 7 }

  END

5.  Operational and Management Considerations

   This section covers two particular areas of operations and
   management: configuration requirements, and transition from or
   coexistence with the [RFC4008] MIB module.

5.1.  Configuration Requirements

   This MIB module assumes that the following information is configured
   on the NAT device by means outside the scope of the present document
   or is imposed by the implementation:

   o  the set of address realms to which the device connects;

   o  For the CGN application, per-subscriber information including
      subscriber index, address realm, assigned prefix or address, and
      (possibly) policies regarding address pool selection in the
      various possible address realms to which the subscriber may
      connect.  In the particular case of DS-Lite [RFC6333] access, as
      well as the assigned outer layer (IPv6) prefix or address, the
      subscriber information will include an inner (IPv4) source
      address, usually 192.0.0.2.

   o  the set of NAT instances running on the device, identified by NAT
      instance index and name;

   o  the port mapping, filtering, pooling, and fragment behavior for
      each NAT instance;

   o  the set of protocols supported by each NAT instance;

   o  for the pooled NAT and CGN applications, address pool information
      for each NAT instance, including for each pool the pool index,
      address realm, address type, minimum and maximum port number, the
      address ranges assigned to that pool, and policies for access to
      that pool's resources;

   o  static address and port map entries.

   As described in previous sections, this MIB module does provide read-
   write objects for control of notifications (see especially
   Section 3.1.2) and limiting of resource consumption (Section 3.1.1).
   This document is written in advance of any practical experience with
   the setting of these values, and can thus provide only general
   principles for how to set them.

   By default, the MIB module definition disables notifications until
   they are explicitly enabled by the operator, using the associated
   threshold value to do so.  To make use of the notifications, the
   operator may wish to take the following considerations into account.

   Except for the low address pool utilization notification, the
   notifications imply that some sort of administrative action is
   required to mitigate an impending shortage of a particular resource.
   The choice of value for the triggering threshold needs to take two
   factors into account: the volatility of usage of the given resource,
   and the amount of time the operator needs to mitigate the potential
   overload situation.  That time could vary from almost immediate to
   several weeks required to order and install new hardware or software.

   To give a numeric example, if average utilization is going up 1% per
   week but can vary 10% around that average in any given hour, and it
   takes two weeks to carry through mitigating measures, the threshold
   should be set to 88% of the corresponding limit (two weeks' growth
   plus 10% volatility margin).  If mitigating measures can be carried
   out immediately, this can rise to 90%. For this particular example
   that change is insignificant, but in other cases the difference may
   be large enough to matter in terms of reduced load on the management
   plane.

   The notification rate limit settings really depend on the operator's
   processes, but are a tradeoff between reliably reporting the notified
   condition and not having it overload the management plane.
   Reliability rises in importance with the importance of the resource
   involved.  Thus the default notification intervals defined in this
   MIB module range from 10 seconds (high reliability) for the address
   and port map entry thresholds up to 60 seconds (lower reliability)
   for the per-subscriber port entry thresholds.  Experience may suggest
   better values.

   The limits on number of instance-level address map and port map
   entries and held fragments relate directly to memory allocations for
   these tables.  The relationship between number of map entries or
   number of held fragments and memory required will be implementation-
   specific.  Hence it is up to the implementor to provide specific
   advice on the setting of these limits.

   The limit on simultaneous number of active subscribers is indirectly
   related to memory consumption for map entries, but also to processor
   usage by the NAT instance.  The best strategy for setting this limit
   would seem to be to leave it disabled during an initial period while
   observing device processor utilization, then to implement a trial
   setting while observing the number of blocked packets affected by the
   new limit.  The setting may vary by NAT instance if a suitable
   estimator of likely load (e.g., total number of hosts served by that
   instance) is available.

5.2.  Transition From and Coexistence With NAT-MIB [RFC 4008]

   A manager may have to deal with a mixture of devices supporting the
   NAT-MIB module [RFC4008] and the NATV2-MIB module defined in the
   present document.  It is even possible that both modules are
   supported on the same device.  The following discussion brings out
   the limits of comparability between the two MIB modules.  A first
   point to note is that NAT-MIB is primarily focussed on configuration,
   while NATV2-MIB is primarily focussed on measurements.

   To summarize the model used by [RFC4008]:

   o  The basic unit of NAT configuration is the interface.

   o  An interface connects to a single realm, either "private", or
      "public".  In principle that means there could be multiple
      instances of one type of realm or the other, but the number is
      physically limited by the number of interfaces on the NAT device.

   o  Before the NAT can operate on a given interface, an "address map"
      has to be configured on it.  The [RFC4008] address map is
      equivalent to the pool tables in the present document.  Since just
      one "address map" is configured per interface, this is the
      equivalent of a single address pool per interface.

   o  The address binding and port binding tables are roughly equivalent
      to the address map and port map tables in the present document in
      their content, but can be either uni- directional or
      bidirectional.  The [RFC4008] model shows the address binding and
      port binding as alternative precursors to session establishment,
      depending on whether the device does address translation only or
      address and port translation.  In contrast, NATV2-MIB assumes a
      model where bidirectional port mappings are based on bidirectional
      address mappings that have conceptually been established
      beforehand.

   o  The equivalent to an [RFC4008] session in NATV2-MIB would be a
      pair of port map entries.  The added complexity in [RFC4008] is
      due to the modelling of NAT service types as defined in [RFC3489]
      (the symmetric NAT in particular) instead of the more granular set
      of behaviors described in [RFC4787].

   With regard to that last point, the mapping between [RFC3489] service
   types and [RFC4787] NAT behaviours is as follows:

   o  A full cone NAT exhibits endpoint-independent port mapping
      behavior and endpoint-independent filtering behavior.

   o  A restricted cone NAT exhibits endpoint-independent port mapping
      behavior, but address-dependent filtering behavior.

   o  A port restricted cone NAT exhibits endpoint-independent port
      mapping behavior, but address-and-port-dependent filtering
      behavior.

   o  A symmetric NAT exhibits address-and-port-dependent port mapping
      and filtering behaviors.

   Note that these NAT types are a subset of the types that could be
   configured according to the [RFC4787] behavioral classification used
   in NATV2-MIB, but they include the two possibilities (full and
   restricted cone NAT) that satisfy requirements REQ-1 and REQ-8 of
   [RFC4787].  Note further that other behaviors defined in [RFC4787]
   are not considered in [RFC4008].

   Having established a context for discussion, we are now in a position
   to compare the outputs provided to management from the [RFC4008] and
   NATV2-MIB modules.  This comparison relates to the ability to compare
   results if testing with both MIBs implemented on the same device
   during a transition period.

   [RFC4008] provides three counters: incoming translations, outgoing
   translations, and discarded packets, at the granularities of
   interface, address map, and protocol, and incoming and outgoing
   translations at the levels of individual address bind, address port
   bind, and session entries.  Implementation at the protocol and
   address map levels is optional.  NATV2-MIB provides a single total
   (both directions) translations counter at the instance, protocol
   within instance, and subscriber levels.  Given the differences in
   granularity, it appears that the only comparable measurement of
   translations between the two MIB modules would be through aggregation
   of the [RFC4008] interface counters to give a total number of
   translations for the NAT instance.

   NATV2-MIB has broken out the single discard counter into a number of
   different counters reflecting the cause of the discard in more
   detail, to help in trouble-shooting.  Again, with the differing
   levels of granularity, the only comparable statistic would be through
   aggregation to a single value of total discards per NAT instance.

   Moving on to state variables, [RFC4008] offers counts of number of
   "address map" (i.e., address pool) entries used (excluding static
   entries) at the address map level, and number of entries in the
   address bind and address and port bind tables respectively.  Finally,
   [RFC4008] provides a count of the number of sessions currently using
   each entry in the address and port bind table.  None of these counts
   are directly comparable with the state values offered by NATV2-MIB,
   because of the exclusion of static entries at the address map level,
   and because of the differing models of the translation tables between
   [RFC4008] and the NATV2=MIB.

6.  Security Considerations

   A number of management objects defined in this MIB module have a MAX-
   ACCESS clause of read-write.  Such objects may be considered
   sensitive or vulnerable in some network environments.  The support
   for SET operations in a non-secure environment without proper
   protection can have a negative effect on network operations.  These
   are the tables and objects and their sensitivity/vulnerability:

   Limits:  An attacker setting a very low or very high limit can easily
      cause a denial-of-service situation.

      *  natv2InstanceLimitAddressMapEntries;

      *  natv2InstanceLimitPortMapEntries;

      *  natv2InstanceLimitPendingFragments;

      *  natv2InstanceLimitSubscriberActives;

      *  natv2SubscriberLimitPortMapEntries.

   Notification thresholds:  An attacker setting an arbitrarily low
      threshold can cause many useless notifications to be generated
      (subject to the notification interval).  Setting an arbitrarily
      high threshold can effectively disable notifications, which could
      be used to hide another attack.

      *  natv2InstanceThresholdAddressMapEntriesHigh;

      *  natv2InstanceThresholdPortMapEntriesHigh;

      *  natv2PoolThresholdUsageLow;
      *  natv2PoolThresholdUsageHigh;

      *  natv2SubscriberThresholdPortMapEntriesHigh.

   Notification intervals:  An attacker setting a low notification
      interval in combination with a low threshold value can cause many
      useless notifications to be generated.

      *  natv2InstanceNotificationInterval;

      *  natv2PoolNotificationInterval;

      *  natv2SubscriberNotificationInterval.

   Some of the readable objects in this MIB module (i.e., objects with a
   MAX-ACCESS other than not-accessible) may be considered sensitive or
   vulnerable in some network environments.  It is thus important to
   control even GET and/or NOTIFY access to these objects and possibly
   to even encrypt the values of these objects when sending them over
   the network via SNMP.  These are the tables and objects and their
   sensitivity/vulnerability:

   Objects that reveal host identities:  Various objects can reveal the
      identity of private hosts that are engaged in a session with
      external end nodes.  A curious outsider could monitor these to
      assess the number of private hosts being supported by the NAT
      device.  Further, a disgruntled former employee of an enterprise
      could use the information to break into specific private hosts by
      intercepting the existing sessions or originating new sessions
      into the host.

      *  entries in the natv2AddressMapTable;

      *  entries in the natv2PortMapTable.

   Other objects that reveal NAT state:  Other managed objects in this
      MIB may contain information that may be sensitive from a business
      perspective, in that they may represent NAT capabilities, business
      policies, and state information.

      *  natv2SubscriberLimitPortMapEntries;

      *  natv2InstancePortMappingBehavior;

      *  natv2InstanceFilteringBehavior;

      *  natv2InstancePoolingBehavior;
      *  natv2InstanceFragmentBehavior;

      *  natv2InstanceAddressMapEntries;

      *  natv2InstancePortMapEntries.

   There are no objects that are sensitive in their own right, such as
   passwords or monetary amounts.

   SNMP versions prior to SNMPv3 did not include adequate security.
   Even if the network itself is secure (for example by using IPsec),
   there is no control as to who on the secure network is allowed to
   access and GET/SET (read/change/create/delete) the objects in this
   MIB module.

   Implementations SHOULD provide the security features described by the
   SNMPv3 framework (see [RFC3410]), and implementations claiming
   compliance to the SNMPv3 standard MUST include full support for
   authentication and privacy via the User-based Security Model (USM)
   [RFC3414] with the AES cipher algorithm [RFC3826].  Implementations
   MAY also provide support for the Transport Security Model (TSM)
   [RFC5591] in combination with a secure transport such as SSH
   [RFC5592] or TLS/DTLS [RFC6353].

   Further, deployment of SNMP versions prior to SNMPv3 is NOT
   RECOMMENDED.  Instead, it is RECOMMENDED to deploy SNMPv3 and to
   enable cryptographic security.  It is then a customer/operator
   responsibility to ensure that the SNMP entity giving access to an
   instance of this MIB module is properly configured to give access to
   the objects only to those principals (users) that have legitimate
   rights to indeed GET or SET (change/create/delete) them.

7.  IANA Considerations

   IANA is requested to assign an object identifier to the natv2MIB
   module, with prefix iso.org.dod.internet.mgmt.mib-2 in the Network
   Management Parameters registry [SMI-NUMBERS].

8.  References

8.1.  Normative References

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

   [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

   [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Textual Conventions for SMIv2", STD
              58, RFC 2579, April 1999.

   [RFC2580]  McCloghrie, K., Perkins, D., and J. Schoenwaelder,
              "Conformance Statements for SMIv2", STD 58, RFC 2580,
              April 1999.

   [RFC3411]  Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
              December 2002.

   [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.

   [RFC3826]  Blumenthal, U., Maino, F., and K. McCloghrie, "The
              Advanced Encryption Standard (AES) Cipher Algorithm in the
              SNMP User-based Security Model", RFC 3826, June 2004.

   [RFC4001]  Daniele, M., Haberman, B., Routhier, S., and J.
              Schoenwaelder, "Textual Conventions for Internet Network
              Addresses", RFC 4001, February 2005.

   [RFC4787]  Audet, F. and C. Jennings, "Network Address Translation
              (NAT) Behavioral Requirements for Unicast UDP", BCP 127,
              RFC 4787, January 2007.

   [RFC5591]  Harrington, D. and W. Hardaker, "Transport Security Model
              for the Simple Network Management Protocol (SNMP)", STD
              78, RFC 5591, June 2009.

   [RFC5592]  Harrington, D., Salowey, J., and W. Hardaker, "Secure
              Shell Transport Model for the Simple Network Management
              Protocol (SNMP)", RFC 5592, June 2009.

   [RFC6353]  Hardaker, W., "Transport Layer Security (TLS) Transport
              Model for the Simple Network Management Protocol (SNMP)",
              STD 78, RFC 6353, July 2011.

8.2.  Informative References

   [I-D.perrault-behave-deprecate-nat-mib-v1]
              Perrault, S., Tsou, T., Sivakumar, S., and T. Taylor,
              "Deprecation of MIB Module NAT-MIB (Managed Objects for
              Network Address Translators (NAT)) (Work in Progress)",
              October 2014.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations", RFC
              2663, August 1999.

   [RFC3410]  Case, J., Mundy, R., Partain, D., and B. Stewart,
              "Introduction and Applicability Statements for Internet-
              Standard Management Framework", RFC 3410, December 2002.

   [RFC3489]  Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,
              "STUN - Simple Traversal of User Datagram Protocol (UDP)
              Through Network Address Translators (NATs)", RFC 3489,
              March 2003.

   [RFC4008]  Rohit, R., Srisuresh, P., Raghunarayan, R., Pai, N., and
              C. Wang, "Definitions of Managed Objects for Network
              Address Translators (NAT)", RFC 4008, March 2005.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

   [SMI-NUMBERS]
              "Network Management Parameters registry at IANA",
              <http://www.iana.org/assignments/smi-numbers>.

Authors' Addresses

   Simon Perreault
   Jive Communications
   Quebec, QC
   Canada

   Email: sperreault@jive.com

   Tina Tsou
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   PR China

   Email: tina.tsou.zouting@huawei.com
   Senthil Sivakumar
   Cisco Systems
   7100-8 Kit Creek Road
   Research Triangle Park, North Carolina  27709
   USA

   Phone: +1 919 392 5158
   Email: ssenthil@cisco.com

   Tom Taylor
   PT Taylor Consulting
   Ottawa
   Canada

   Email: tom.taylor.stds@gmail.com