RFC7659
Internet Engineering Task Force (IETF) S. Perreault Request for Comments: 7659 Jive Communications Category: Standards Track T. Tsou ISSN: 2070-1721 Huawei Technologies
S. Sivakumar
Cisco Systems
T. Taylor
PT Taylor Consulting
October 2015
Definitions of Managed Objects for Network Address Translators (NATs)
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 the 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
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7659.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
3.3.7. The Address Pool Address Range Table:
5.2. Transition from and Coexistence with NAT-MIB (RFC 4008) . 76
Contents
- 1 The Internet-Standard Management Framework
- 2 Introduction
- 3 Overview
- 3.1 Content Provided by the NATV2-MIB Module
- 3.2 Outline of MIB Module Organization
- 3.3 Detailed MIB Module Walk-Through
- 3.3.1 Textual Conventions
- 3.3.2 Notifications
- 3.3.3 The Subscriber Table: natv2SubscriberTable
- 3.3.4 The Instance Table: natv2InstanceTable
- 3.3.5 The Protocol Table: natv2ProtocolTable
- 3.3.6 The Address Pool Table: natv2PoolTable
- 3.3.7 The Address Pool Address Range Table: natv2PoolRangeTable
- 3.3.8 The Address Map Table: natv2AddressMapTable
- 3.3.9 The Port Map Table: natv2PortMapTable
- 3.4 Conformance: Three Application Scenarios
- 4 Definitions
- 5 Operational and Management Considerations
- 6 Security Considerations
- 7 IANA Considerations
- 8 References
The Internet-Standard 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, RFC 2578 RFC2578, STD 58, RFC 2579 RFC2579 and STD 58, RFC 2580 RFC2580.
Introduction
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 the 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. RFC7658 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 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 Sections 6 and 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.
Overview
This section provides a prose description of the contents and organization of the NATV2-MIB module.
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.
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 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.
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 -1 (default).
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.
Objects returned: natv2PoolNotifiedPortMapEntries and
natv2PoolNotifiedPortMapProtocol in natv2PoolTable.
Rate control: natv2PoolNotificationInterval in 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 and
natv2PoolNotifiedPortMapProtocol in natv2PoolTable.
Rate control: natv2PoolNotificationInterval in 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 and
natv2InstanceAddressMapCreations in natv2InstanceTable.
Rate control: natv2InstanceNotificationInterval in
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 and
natv2InstancePortMapCreations in natv2InstanceTable.
Rate control: natv2InstanceNotificationInterval in
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 and
natv2SubscriberPortMapCreations in natv2SubscriberTable.
Rate control: natv2SubscriberNotificationInterval in
natv2SubscriberTable.
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.
Statistics
NATV2-MIB provides a number of counters, intended to help with both the provisioning of the NAT and the 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 discontinuity 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 it 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
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
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.
Textual Conventions
The module defines four key textual conventions: ProtocolNumber, Natv2SubscriberIndex, Natv2InstanceIndex, and Natv2PoolIndex. ProtocolNumber is based on the IANA registry of protocol numbers and hence is potentially reusable by other MIB modules.
Objects of type Natv2SubscriberIndex identify individual subscribers served by 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 the device rather than the 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.
Notifications
Notifications were described in Section 3.1.2.
The Subscriber Table: natv2SubscriberTable
Table natv2SubscriberTable is indexed by the 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 Sections 3.1.3 and 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 Dual-Stack Lite (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.
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 Sections 3.1.3 and 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.
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 they 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 Sections 3.1.3 and 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.
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 Sections 3.1.3 and 3.1.4 respectively, plus two additional state objects described below. natv2PoolTable provides the pool-specific object natv2PoolDiscontinuityTime to indicate the time since the statistical counters have accumulated continuously.
Read-write objects to set high and low thresholds for pool usage notifications and for governing the notification rate were identified in Section 3.1.2.
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.
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.
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.
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.
Conformance: Three Application Scenarios
The conformance statements in NATV2-MIB provide for three application scenarios: basic NAT, NAT supporting address pools, and CGN.
A basic NAT MAY limit the number of NAT instances it supports to one, but it 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 it also includes the special provision for DS-Lite access in the address and port map tables.
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 "201510020000Z" -- 2 October 2015
ORGANIZATION
"IETF Behavior Engineering for Hindrance
Avoidance (BEHAVE) Working Group"
CONTACT-INFO
"Working Group Email: [email protected]
Simon Perreault
Jive Communications
Quebec, QC
Canada
Email: [email protected]
Tina Tsou
Huawei Technologies
Bantian, Longgang
Shenzhen 518129
China
Email: [email protected]
Senthil Sivakumar
Cisco Systems
7100-8 Kit Creek Road
Research Triangle Park, North Carolina 27709
United States
Phone: +1 919 392 5158
Email: [email protected]
Tom Taylor
PT Taylor Consulting
Ottawa
Canada
Email: [email protected]"
DESCRIPTION
"This MIB module defines the generic managed objects
for NAT.
Copyright (c) 2015 IETF Trust and the persons
identified as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this MIB module is part of RFC 7659; see the RFC itself for full legal notices." REVISION "201510020000Z" -- 2 October 2015 DESCRIPTION "Complete rewrite, published as RFC 7659. Replaces former version published as RFC 4008." ::= { mib-2 234 }
-- Textual conventions
ProtocolNumber ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"A protocol number, from the IANA Protocol Numbers
registry."
REFERENCE
"IANA Protocol Numbers,
<http://www.iana.org/assignments/protocol-numbers>"
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 7659, Sections 3.1.2 and 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 -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 7659, Sections 3.1.2 and 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 -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 7659, 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 -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 -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 a writable
threshold value and limit on port consumption."
REFERENCE
"RFC 7659, 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 notifications by setting threshold to -1
natv2SubscriberThresholdPortMapEntriesHigh Integer32,
-- Disable limit by setting to 0
natv2SubscriberNotificationInterval Unsigned32 }
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 Customer Premises Equipment
(CPE). The type of this prefix is given by
natv2SubscriberInternalPrefixType. 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 7659, 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 7659, 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."
DEFVAL
{ 0 }
::= { natv2SubscriberEntry 15 }
natv2SubscriberThresholdPortMapEntriesHigh OBJECT-TYPE
SYNTAX 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 -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
{ -1 }
::= { natv2SubscriberEntry 16 }
natv2SubscriberNotificationInterval OBJECT-TYPE
SYNTAX Unsigned32 (1..3600)
UNITS
"Seconds"
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Minimum number of seconds 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 that 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 7659, Section 3.3.4.
NAT behaviors: RFC 4787 (primary, UDP); RFC 5382 (TCP);
RFC 5508 (ICMP); and RFC 5597 (Datagram Congestion Control
Protocol (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 -1
natv2InstanceThresholdAddressMapEntriesHigh Integer32,
natv2InstanceThresholdPortMapEntriesHigh 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 that 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 Virtual Routing and Forwarding
(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 the 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
the 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 7659, Section 3.3.8.
Hairpinning: 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 7659, 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 -1.
natv2InstanceThresholdAddressMapEntriesHigh OBJECT-TYPE
SYNTAX 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 -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
{ -1 }
::= { natv2InstanceEntry 20 }
natv2InstanceThresholdPortMapEntriesHigh OBJECT-TYPE
SYNTAX 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 -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
{ -1 }
::= { natv2InstanceEntry 21 }
natv2InstanceNotificationInterval OBJECT-TYPE
SYNTAX Unsigned32 (1..3600)
UNITS
"Seconds"
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Minimum number of seconds 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.
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.
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.
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."
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 Textual Convention
(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 7659, 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 7659, Section 3.3.5.
IANA Protocol Numbers,
<http://www.iana.org/assignments/protocol-numbers>"
::= { 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 7659, Sections 3.3.5 and 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 7659, 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 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 that is 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 7659. The primary reference is RFC 2663, Section 2.1."
::= { natv2PoolEntry 3 }
natv2PoolAddressType OBJECT-TYPE
SYNTAX InetAddressType
MAX-ACCESS read-only
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-only
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-only
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 7659, 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 7659, 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 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. 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 7659, Sections 3.1.2 and 3.3.6."
DEFVAL { -1 }
::= { natv2PoolEntry 14 }
natv2PoolThresholdUsageHigh OBJECT-TYPE
SYNTAX 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 -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 { -1 }
::= { natv2PoolEntry 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 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 17 }
natv2PoolNotificationInterval OBJECT-TYPE
SYNTAX Unsigned32 (1..3600)
UNITS
"Seconds"
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Minimum number of seconds between successive
notifications for this address pool. Controls the generation
of natv2NotificationPoolUsageLow and
natv2NotificationPoolUsageHigh."
DEFVAL
{ 20 }
::= { natv2PoolEntry 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 7659, Section 3.3.7."
::= { 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 the internal to external address.
natv2AddressMapTable OBJECT-TYPE
SYNTAX SEQUENCE OF Natv2AddressMapEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Table of mappings from the 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 7659, 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, Sections 5.7 (for well-known addresses)
and 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, Sections 5.7 (for well-known addresses)
and 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. The address
type is given by natv2AddressMapInternalAddressType.
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, Sections 5.7 (for well-known addresses) and 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. The address type is
given by natv2AddressMapInternalMappedAddressType. In the
case of DS-Lite (RFC 6333), this is the source address of
the encapsulated IPv4 packet, normally lying in 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, Sections 5.7 (for well-known addresses)
and 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.
The address type is given by
natv2AddressMapExternalAddressType.
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, Sections 5.7 (for well-known addresses)
and 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 the 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 7659, Section 3.3.9. DS-Lite: RFC 6333, Sections 5.7 (for well-known addresses) and 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. The address type is given
by natv2PortMapExternalAddressType."
::= { 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
"DS-Lite: RFC 6333."
::= { 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. The address type is given
by natv2PortMapInternalAddressType."
REFERENCE
"DS-Lite: RFC 6333, Sections 5.7 (for well-known addresses)
and 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. The address type is given
by natv2PortMapInternalMappedAddressType.
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, Sections 5.7 (for well-known addresses) and 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 Network Address and Port Translator (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
}
::= { 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
}
::= { 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
}
::= { 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
Operational and Management Considerations
This section covers two particular areas of operations and management: configuration requirements and transition from or coexistence with the MIB module in RFC4008.
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.
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 focused on configuration, while NATV2-MIB is primarily focused 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 address map in RFC4008 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 they can be either unidirectional or bidirectional. The model in RFC4008 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 modeling of NAT service types as defined in RFC3489 (the symmetric NAT in particular) instead of the more granular set of behaviors described in RFC4787. (Note: RFC3489 has been obsoleted by RFC5389.)
With regard to that last point, the mapping between RFC3489 service types and RFC4787 NAT behaviors 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 troubleshooting. 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.
Security Considerations
There are a number of management objects defined in this MIB module with 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 opens devices to attack. 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. If nothing else, unauthorized monitoring of these objects will violate individual subscribers' privacy.
* entries in the natv2SubscriberTable;
* 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.
IANA Considerations
IANA has assigned an object identifier to the natv2MIB module, with prefix iso.org.dod.internet.mgmt.mib-2 in the SMI Numbers registry [SMI-NUMBERS].
References
Normative References
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>.
RFC2578 McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578,
DOI 10.17487/RFC2578, April 1999,
<http://www.rfc-editor.org/info/rfc2578>.
RFC2579 McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2",
STD 58, RFC 2579, DOI 10.17487/RFC2579, April 1999,
<http://www.rfc-editor.org/info/rfc2579>.
RFC2580 McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Conformance Statements for SMIv2",
STD 58, RFC 2580, DOI 10.17487/RFC2580, April 1999,
<http://www.rfc-editor.org/info/rfc2580>.
RFC3411 Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
DOI 10.17487/RFC3411, December 2002,
<http://www.rfc-editor.org/info/rfc3411>.
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,
DOI 10.17487/RFC3414, December 2002,
<http://www.rfc-editor.org/info/rfc3414>.
RFC3826 Blumenthal, U., Maino, F., and K. McCloghrie, "The
Advanced Encryption Standard (AES) Cipher Algorithm in the
SNMP User-based Security Model", RFC 3826,
DOI 10.17487/RFC3826, June 2004,
<http://www.rfc-editor.org/info/rfc3826>.
RFC4001 Daniele, M., Haberman, B., Routhier, S., and J.
Schoenwaelder, "Textual Conventions for Internet Network
Addresses", RFC 4001, DOI 10.17487/RFC4001, February 2005,
<http://www.rfc-editor.org/info/rfc4001>.
RFC4787 Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <http://www.rfc-editor.org/info/rfc4787>.
RFC5591 Harrington, D. and W. Hardaker, "Transport Security Model
for the Simple Network Management Protocol (SNMP)",
STD 78, RFC 5591, DOI 10.17487/RFC5591, June 2009,
<http://www.rfc-editor.org/info/rfc5591>.
RFC5592 Harrington, D., Salowey, J., and W. Hardaker, "Secure
Shell Transport Model for the Simple Network Management
Protocol (SNMP)", RFC 5592, DOI 10.17487/RFC5592, June
2009, <http://www.rfc-editor.org/info/rfc5592>.
RFC6353 Hardaker, W., "Transport Layer Security (TLS) Transport
Model for the Simple Network Management Protocol (SNMP)",
STD 78, RFC 6353, DOI 10.17487/RFC6353, July 2011,
<http://www.rfc-editor.org/info/rfc6353>.
Informative References
RFC2460 Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, December 1998, <http://www.rfc-editor.org/info/rfc2460>.
RFC2663 Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663, DOI 10.17487/RFC2663, August 1999,
<http://www.rfc-editor.org/info/rfc2663>.
RFC3410 Case, J., Mundy, R., Partain, D., and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410,
DOI 10.17487/RFC3410, December 2002,
<http://www.rfc-editor.org/info/rfc3410>.
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,
DOI 10.17487/RFC3489, March 2003,
<http://www.rfc-editor.org/info/rfc3489>.
RFC4008 Rohit, R., Srisuresh, P., Raghunarayan, R., Pai, N., and
C. Wang, "Definitions of Managed Objects for Network
Address Translators (NAT)", RFC 4008,
DOI 10.17487/RFC4008, March 2005,
<http://www.rfc-editor.org/info/rfc4008>.
RFC5389 Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389, DOI 10.17487/RFC5389, October 2008, <http://www.rfc-editor.org/info/rfc5389>.
RFC6333 Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<http://www.rfc-editor.org/info/rfc6333>.
RFC7658 Perreault, S., Tsou, T., Sivakumar, S., and T. Taylor,
"Deprecation of MIB Module NAT-MIB: Managed Objects for
Network Address Translators (NATs)", RFC 7658,
DOI 10.17487/RFC7658, October 2015,
<http://www.rfc-editor.org/info/rfc7658>.
[SMI-NUMBERS]
IANA, "Structure of Management Information (SMI) Numbers
(MIB Module Registrations)",
<http://www.iana.org/assignments/smi-number>.
Authors' Addresses
Simon Perreault Jive Communications Quebec, QC Canada
Email: [email protected]
Tina Tsou Huawei Technologies Bantian, Longgang District Shenzhen 518129 China
Email: [email protected]
Senthil Sivakumar Cisco Systems 7100-8 Kit Creek Road Research Triangle Park, North Carolina 27709 United States
Phone: +1 919 392 5158 Email: [email protected]
Tom Taylor PT Taylor Consulting Ottawa Canada
Email: [email protected]
