Internet Engineering Task Force (IETF) S. Sivakumar Request for Comments: 8158 R. Penno Category: Standards Track Cisco Systems ISSN: 2070-1721AprilDecember 2017 IP Flow Information Export (IPFIX) Information Elements for Logging NAT Events Abstract Network operators require NAT devices to log events like creation and deletion of translations and information about the resources that the NAT device is managing. In many cases, the logs are essential to identify an attacker or a host that was used to launch malicious attacks and for various other purposes of accounting. Since there is no standard way of logging this information, different NAT devices use proprietary formats; hence, it is difficult to expect consistent behavior. This lack of standardization makes it difficult to write thecollectorCollector applications that would receive this data and process it to present useful information. This document describes the formats for logging NAT events. 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 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8158.https://www.rfc-editor.org/info/rfc8158. Copyright Notice Copyright (c) 2017 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)(https://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Deployment . . . . . . . . . . . . . . . . . . . . . . . . .45 4. Event-Based Logging . . . . . . . . . . . . . . . . . . . . . 5 4.1. Logging Destination Information . . . . . . . . . . . . . 6 4.2. Information Elements . . . . . . . . . . . . . . . . . . 6 4.3. Definition of NAT Events . . . . . . . . . . . . . . . .910 4.4. Quota Exceeded Event Types . . . . . . . . . . . . . . .1011 4.5. Threshold Reached Event Types . . . . . . . . . . . . . .1112 4.6. Templates for NAT Events . . . . . . . . . . . . . . . .1213 4.6.1. NAT44 Session Create and DeleteSessionEvents . . . . . . .1213 4.6.2. NAT64 Session Create and DeleteSessionEvents . . . . . . .1314 4.6.3. NAT44 BIB Create and Delete Events . . . . . . . . .1415 4.6.4. NAT64 BIB Create and Delete Events . . . . . . . . .1415 4.6.5. Addresses Exhausted Event . . . . . . . . . . . . . .1516 4.6.6. Ports Exhausted Event . . . . . . . . . . . . . . . .1516 4.6.7. Quota Exceeded Events . . . . . . . . . . . . . . . .1617 4.6.7.1. Maximum Session Entries Exceeded . . . . . . . .1617 4.6.7.2. Maximum BIB Entries Exceeded . . . . . . . . . .1617 4.6.7.3. Maximum Entries per User Exceeded . . . . . . . .1617 4.6.7.4. Maximum Active Hosts or Subscribers Exceeded . .1718 4.6.7.5. Maximum Fragments Pending Reassembly Exceeded . .1718 4.6.8. Threshold Reached Events . . . . . . . . . . . . . .1819 4.6.8.1. Address Pool High or Low Threshold Reached . . .1819 4.6.8.2. Address and Port Mapping High Threshold Reached .1820 4.6.8.3. Address and Port Mapping per User High Threshold Reached . . . . . . . . . . . . . . . . . . . . .1920 4.6.8.4. Global Address Mapping High Threshold Reached . .1921 4.6.9. Address Binding Create and Delete Events . . . . . .2021 4.6.10. Port Block Allocation and De-allocation . . . . . . .2021 5. Management Considerations . . . . . . . . . . . . . . . . . .2122 5.1. Ability to Collect Events from Multiple NAT Devices . . .2122 5.2. Ability to Suppress Events . . . . . . . . . . . . . . .2122 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . .2223 6.1. Information Elements . . . . . . . . . . . . . . . . . .2223 6.1.1. natInstanceID . . . . . . . . . . . . . . . . . . . .2223 6.1.2. internalAddressRealm . . . . . . . . . . . . . . . .2223 6.1.3. externalAddressRealm . . . . . . . . . . . . . . . .2324 6.1.4. natQuotaExceededEvent . . . . . . . . . . . . . . . .2324 6.1.5. natThresholdEvent . . . . . . . . . . . . . . . . . .2425 6.1.6. natEvent . . . . . . . . . . . . . . . . . . . . . .2526 6.1.7. maxSessionEntries . . . . . . . . . . . . . . . . . . 26 6.1.8. maxBIBEntries . . . . . . . . . . . . . . . . . . . . 27 6.1.9. maxEntriesPerUser . . . . . . . . . . . . . . . . . . 27 6.1.10. maxSubscribers . . . . . . . . . . . . . . . . . . . 27 6.1.11. maxFragmentsPendingReassembly . . . . . . . . . . . . 28 6.1.12. addressPoolHighThreshold . . . . . . . . . . . . . . 28 6.1.13. addressPoolLowThreshold . . . . . . . . . . . . . . . 28 6.1.14. addressPortMappingHighThreshold . . . . . . . . . . . 29 6.1.15. addressPortMappingLowThreshold . . . . . . . . . . . 29 6.1.16. addressPortMappingPerUserHighThreshold . . . . . . . 29 6.1.17. globalAddressMappingHighThreshold . . . . . . . . . . 30 7. Security Considerations . . . . . . . . . . . . . . . . . . .2530 8. References . . . . . . . . . . . . . . . . . . . . . . . . .2631 8.1. Normative References . . . . . . . . . . . . . . . . . .2631 8.2. Informative References . . . . . . . . . . . . . . . . .2732 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . .2832 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .2833 1. Introduction The IP Flow Information Export (IPFIX) Protocol [RFC7011] defines a generic push mechanism for exporting information and events. The IPFIX Information Model [IPFIX-IANA] defines a set of standard Information Elements (IEs) that can be carried by the IPFIX protocol.-->This document details the IPFIX IEs that MUST be logged by a NAT device that supports NAT logging using IPFIX and all the optional fields. The fields specified in this document are gleaned from [RFC4787] and [RFC5382]. This document and [NAT-LOG] are written in order to standardize the events and parameters to be recorded using IPFIX [RFC7011] and SYSLOG [RFC5424], respectively.The intent is to provide a consistent way to log information irrespective of the mechanism that is used. This document uses IPFIX as the encoding mechanismThis document uses IPFIX as the encoding mechanism to describe the logging of NAT events. However, the information that is logged should be the same irrespective of what kind of encoding scheme is used. IPFIX is chosen because it is an IETF standard that meets all the needs for a reliable logging mechanism. IPFIX provides the flexibility to the logging device to define the datasets that it is logging. The IEs specified for logging must be the same irrespective of the encoding mechanism used. 1.1. Terminology The term "NAT device" in this document refers to any NAT44 or NAT64 device. The term"collector""Collector" refers to any device that receives binary data from a NAT device and converts it into meaningful information. This document uses the term "session" as defined in [RFC2663], and the term "Binding Information Base" (BIB) as defined in [RFC6146]. The term "Information Element" or "IE" is defined in [RFC7011]. The term "Carrier-Grade NAT" refers to a large-scale NAT device as described in [RFC6888] The IPFIX IEs that are NAT specific are created with NAT terminology. In order to avoid creating duplicates, IEs are reused if they convey the same meaning. This document uses the term "timestamp" for the IE, which defines the time when an event is logged; this is the same as the IPFIX term "observationTimeMilliseconds" as described in [IPFIX-IANA]. Since observationTimeMilliseconds is not self- explanatory for NAT implementors, the term "timeStamp" is used. Event templates, which refer to IPFIX Template Records, as well as log events, which refer to IPFIX Flow Records, are also used in this document. 1.2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Scope This document provides the information model to be used for logging the NAT events, including Carrier-Grade NAT (CGN) events. [RFC7011] provides guidance on the choices of the transport protocols used for IPFIX and their effects. This document does not provide guidance on transport protocols like TCP, UDP, or Stream Control Transmission Protocol (SCTP), which are to be used to log NAT events. The logs SHOULD be reliably sent to thecollectorCollector to ensure that the log events are not lost. The choice of the actual transport protocol is beyond the scope of this document. This document uses the allocated IPFIX IEs in the IANA "IPFIX Information Elements" registry [IPFIX-IANA] and registers some new ones. This document assumes that the NAT device will use the existing IPFIX framework to send the log events to thecollector.Collector. This would mean that the NAT device will specify the template that it is going to use for each of the events. The templates can be of varying length, and there could be multiple templates that a NAT device could use to log the events. The implementation details of thecollectorCollector application are beyond the scope of this document. The optimization of logging the NAT events is left to the implementation and is beyond the scope of this document. 3. Deployment NAT logging based on IPFIX uses binary encoding; hence, it is very efficient. IPFIX-based logging is recommended for environments where a high volume of logging is required, for example, where per-flow logging is needed or in case of Carrier-Grade NAT. However, IPFIX- based logging requires acollectorCollector that processes the binary data and requires a network management application that converts this binary data to a human-readable format. AcollectorCollector may receive NAT events from multiple CGN devices. ThecollectorCollector distinguishes between the devices using the source IP address, source port, and Observation Domain ID in the IPFIX header. ThecollectorCollector can decide to store the information based on the administrative policies that are in line with the operator and the local jurisdiction. The retention policy is not dictated by theexporterExporter and is left to the policies that are defined at thecollector.Collector. AcollectorCollector may have scale issues if it is overloaded by a large number of simultaneous events. An appropriate throttling mechanism may be used to handle the oversubscription. The logs that are exported can be used for a variety of reasons. An example use case is to do accounting based on when the users logged on and off. The translation will be installed when the user logs on and removed when the user logs off. These events create log records. Another use case is to identify an attacker or a host in a provider network. The network administrators can use these logs to identify the usage patterns, the need for additional IP addresses, and etc. The deployment of NAT logging is not limited to just these cases. 4. Event-Based Logging An event in a NAT device can be viewed as a state transitionasbecause it relates to the management of NAT resources. The creation and deletion of NAT sessions and bindings are examples of events, as they result in resources (addresses and ports) being allocated or freed. The events can happen through the processing of data packets flowing through the NAT device, through an external entity installing policies on the NAT router, or as a result of an asynchronous event like a timer. The list of events is provided in Table 2. Each of these events SHOULD be logged, unless this is administratively prohibited. A NAT device MAY log these events to multiplecollectorsCollectors if redundancy is required. The network administrator will specify thecollectorsCollectors to which the log records are to be sent. It is necessary to preserve the list ofcollectorsCollectors and its associated information like the IPv4/IPv6 address, port, and protocol across reboots so that the configuration information is not lost when the device is restarted. The NAT device implementing the IPFIX logging MUST follow the IPFIX specification in [RFC7011]. 4.1. Logging Destination Information Logging destination information in a NAT event is discussed in [RFC6302] and [RFC6888]. Logging destination information increases the size of each record and increases the need for storage considerably. It increases the number of log events generated because when the same user connects to a different destination, it results in a log record per destination address. Logging the source and destination addresses results in loss of privacy. Logging of destination addresses and ports, pre- or post-NAT, SHOULD NOT be done [RFC6888]. However, this document provides the necessary fields to log the destination information in cases where they must be logged. 4.2. Information Elements The templates could contain a subset of the IEs shown in Table 1, depending upon the event being logged. For example, a NAT44 session creation template record will contain: {sourceIPv4Address, postNATSourceIPv4Address, destinationIPv4Address, postNATDestinationIPv4Address, sourceTransportPort, postNAPTSourceTransportPort, destinationTransportPort, postNAPTDestinationTransportPort, internalAddressRealm, natEvent, timeStamp} An example of the actual event data record is shown below in a human- readable form: {192.0.2.1, 203.0.113.100, 192.0.2.104, 192.0.2.104, 14800, 1024, 80, 80, 0, 1, 09:20:10:789} A single NAT device could be exporting multiple templates, and thecollectorCollector MUST support receiving multiple templates from the same source. The following table includes all the IEs that a NAT device would need to export the events. The formats of the IEs and the IPFIX IDs are listed. Detailed descriptions of the fields natInstanceID, internalAddressRealm, externalAddressRealm, natQuotaExceededEvent, and natThresholdEvent are included in the IANA Considerations section.+----------------------------------+------------+-----+-------------++----------------------------------+----------+-------+-------------+ | Field Name | Size |IDIANA | Description | | | (bits) | IPFIX | | | | | ID | |+----------------------------------+------------+-----+-------------++----------------------------------+----------+-------+-------------+ | timeStamp | 64 | 323 | System Time | | | | | when the | | | | | event | | | | | occurred | | | | | | | natInstanceID | 32 | 463 | NAT | | | | | Instance | | | | | Identifier | | | | | | | vlanId | 16 | 58 | VLAN ID in | | | | | case of | | | | | overlapping | | | | | networks | | | | | | | ingressVRFID | 32 | 234 | VRF ID in | | | | | case of | | | | | overlapping | | | | | networks | | | | | | | sourceIPv4Address | 32 | 8 | Source IPv4 | | | | | Address | | | | | | | postNATSourceIPv4Address | 32 | 225 | Translated | | | | | Source IPv4 | | | | | Address | | | | | | | protocolIdentifier | 8 | 4 | Transport | | | | | protocol | | | | | | | sourceTransportPort | 16 | 7 | Source Port | | | | | | | postNAPTSourceTransportPort | 16 | 227 | Translated | | | | | Source port | | | | | | | destinationIPv4Address | 32 | 12 | Destination | | | | | IPv4 | | | | | Address | | | | | | | postNATDestinationIPv4Address | 32 | 226 | Translated | | | | | IPv4 | | | | | destination | | | | | address | | | | | | | destinationTransportPort | 16 | 11 | Destination | | | | | port | | | | | | | postNAPTDestinationTransportPort | 16 | 228 | Translated | | | | | Destination | | | | | port | | | | | | | sourceIPv6Address | 128 | 27 | Source IPv6 | | | | | address | | | | | | | destinationIPv6Address | 128 | 28 | Destination | | | | | IPv6 | | | | | address | | | | | | | postNATSourceIPv6Address | 128 | 281 | Translated | | | | | source IPv6 | | | | | address | | | | | | | postNATDestinationIPv6Address | 128 | 282 | Translated | | | | | Destination | | | | | IPv6 | | | | | address | | | | | | | internalAddressRealm |octetArrayoctetArr | 464 | Source | | | ay | | Address | | | | | Realm | | | | | | | externalAddressRealm |octetArrayoctetArr | 465 | Destination | | | ay | | Address | | | | | Realm | | | | | | | natEvent | 8 | 230 | Type of | | | | | Event | | | | | | | portRangeStart | 16 | 361 | Allocated | | | | | port block | | | | | start | | | | | | | portRangeEnd | 16 | 362 | Allocated | | | | | Port block | | | | | end | | | | | | | natPoolId | 32 | 283 | NAT pool | | | | | Identifier | | | | | | | natQuotaExceededEvent | 32 | 466 | Limit event | | | | | identifier | | | | | | | natThresholdEvent | 32 | 467 | Threshold | | | | | event | | | | | identifier |+----------------------------------+------------+-----+-------------+ Table 1: Template Format 4.3. Definition of NAT Events The following is the complete list of NAT events and the proposed event type values. The natEvent IE is defined in the "IPFIX Information Elements" registry [IPFIX-IANA];. The list can be expanded in the future as necessary. The data record will have the corresponding natEvent value to indicate the event that is being logged. Note that the first two events are marked "Historic" and are listed here for the sole purpose of completeness. Any compliant implementation SHOULD NOT use the events that are marked "Historic". These values were defined prior to the existence of this document and outside the IETF. These events are not standalone and require more information to be conveyed to qualify the event. For example, the NAT Translation create event does not specify if it is NAT44 or NAT64. As a result, the Behave working group decided to have an explicit definition for each one of the unique events. +-------------------------------------+--------+ | Event Name | Values|+-------------------------------------+--------+|Reserved|0| |NAT Translation create (Historic)|1maxSessionEntries | 32 |NAT Translation Delete (Historic)471 |2Maximum | |NAT Addresses exhausted|3| |NAT44sessioncreate|4| |NAT44 session delete|5| entries |NAT64 session create|6| |NAT64 session delete|7| |NAT44 BIB createmaxBIBEntries |832 | 472 |NAT44 BIB deleteMaximum |9| |NAT64 BIB create|10| bind |NAT64 BIB delete|11| |NAT ports exhausted|12entries | |Quota exceeded|13| |Address binding create|14| maxEntriesPerUser |Address binding delete32 |15473 | Maximum |Port block allocation|16| |Port block de-allocation|17entries | |Threshold reached|18|+-------------------------------------+--------+ Table 2: NAT Event ID 4.4. Quota Exceeded Event Types The Quota Exceeded event is a natEvent IE described in Table 2. The Quota exceeded events are generated when the hard limits set by the administrator have been reached or exceeded. The following table shows the sub-event types for the Quota exceeded or limits reached event. The events that can be reported are the maximum session entries limit reached, maximum BIB entries limit reached, maximum (session/BIB) entries per user limit reached, maximum active hosts or subscribers limit reached, and maximum Fragments pending reassembly limit reached. +---------------------------------------+--------+|Quota Exceeded Event Nameper-user |Values|+---------------------------------------+--------+|Reserved|0| |Maximum session entries|1maxSubscribers | 32 |Maximum BIB entries474 |2Maximum | |Maximum entries per user|3| |Maximum active hosts orsubscribers |4| | | | | | maxFragmentsPendingReassembly | 32 | 475 | Maximum | | | | | fragmentspending reassembly|5|+---------------------------------------+--------+ Table 3: Quota Exceeded Event 4.5. Threshold Reached Event Types The following table shows the sub-event types| | | forthe| | | | | ressembly | | | | | | | addressPoolHighThreshold | 32 | 476 | High | | | | | thresholdreached event. The administrator can configure the thresholds, and whenever the| | | | | for address | | | | | pool | | | | | | | addressPoolLowThreshold | 32 | 477 | Low | | | | | thresholdis reached or exceeded, the corresponding| | | | | for address | | | | | pool | | | | | | | addressPortMappingHighThreshold | 32 | 478 | High | | | | | threshold | | | | | for address | | | | | /port | | | | | mapping | | | | | | | addressPortMappingLowThreshold | 32 | 479 | Low | | | | | threshold | | | | | for address | | | | | /port | | | | | mapping | | | | | | | addressPortMappingPerUserHighThr | 32 | 480 | High | | eshold | | | threshold | | | | | for per- | | | | | user addres | | | | | s/port | | | | | mapping | | | | | | | globalAddressMappingHighThreshol | 32 | 481 | High | | d | | | threshold | | | | | for global | | | | | address | | | | | mapping | +----------------------------------+----------+-------+-------------+ Table 1: NAT IE List 4.3. Definition of NAT Events The following is the complete list of NAT events and the proposed event type values. The natEvent IE is defined in the "IPFIX Information Elements" registry [IPFIX-IANA];. The list can be expanded in the future as necessary. The data record will have the corresponding natEvent value to indicate the event that is being logged. Note that the first two events are marked "Historic" and are listed here for the sole purpose of completeness. Any compliant implementation SHOULD NOT use the events that are marked "Historic". These values were defined prior to the existence of this document and outside the IETF. These events are not standalone and require more information to be conveyed to qualify the event. For example, the NAT translation create event does not specify if it is NAT44 or NAT64. As a result, the Behave working group decided to have an explicit definition for each one of the unique events. +-------+------------------------------------+ | Value | Event Name | +-------+------------------------------------+ | 0 | Reserved | | 1 | NAT translation create (Historic) | | 2 | NAT translation delete (Historic) | | 3 | NAT Addresses exhausted | | 4 | NAT44 session create | | 5 | NAT44 session delete | | 6 | NAT64 session create | | 7 | NAT64 session delete | | 8 | NAT44 BIB create | | 9 | NAT44 BIB delete | | 10 | NAT64 BIB create | | 11 | NAT64 BIB delete | | 12 | NAT ports exhausted | | 13 | Quota Exceeded | | 14 | Address binding create | | 15 | Address binding delete | | 16 | Port block allocation | | 17 | Port block de-allocation | | 18 | Threshold Reached | +-------+------------------------------------+ Table 2: NAT Event ID 4.4. Quota Exceeded Event Types The Quota Exceeded event is a natEvent IE described in Table 2. The Quota Exceeded events are generated when the hard limits set by the administrator have been reached or exceeded. The following table shows the sub-event types for the Quota Exceeded event. The events that can be reported are the maximum session entries limit reached, maximum BIB entries limit reached, maximum (session/BIB) entries per user limit reached, maximum active hosts or subscribers limit reached, and maximum Fragments pending reassembly limit reached. +-------+---------------------------------------+ | Value | Quota Exceeded Event Name | +-------+---------------------------------------+ | 0 | Reserved | | 1 | Maximum session entries | | 2 | Maximum BIB entries | | 3 | Maximum entries per user | | 4 | Maximum active hosts or subscribers | | 5 | Maximum fragments pending reassembly | +-------+---------------------------------------+ Table 3: Quota Exceeded Event 4.5. Threshold Reached Event Types The following table shows the sub-event types for the Threshold Reached event. The administrator can configure the thresholds, and whenever the threshold is reached or exceeded, the corresponding events are generated. The main difference between the Quota Exceeded and ThresholdreachedReached events is that, once the QuotaexceededExceeded events are hit, the packets are dropped or mappings will not be created, whereas thethreshold reachedThreshold Reached events will provide the operator a chance to take action before the traffic disruptions can happen. A NAT device can choose to implement one or the other, or both. The address pool high threshold event will be reported when the address pool reaches a high-water mark as defined by the operator. This will serve as an indication that either the operator might have to add more addresses to the pool or the subsequent users may be denied NAT translation mappings. The address pool low threshold event will be reported when the address pool reaches a low-water mark as defined by the operator. This will serve as an indication that the operator can reclaim some of the global IPv4 addresses in the pool. The address and port mapping high threshold event is generated when thenumber of ports innumber of ports in the configured address pool has reached a configured threshold. The per-user address and port mapping high threshold is generated when a single user utilizes more address and port mapping than a configured threshold. We don't track the low threshold for per-user address and port mappings because, as the ports are freed, the address will become available. The address pool low threshold event will then be triggered so that the global IPv4 address can be reclaimed. The global address mapping high threshold event is generated when the maximum number of mappings per user is reached for a NAT device doing paired-address pooling. +-------+---------------------------------------------------------+ | Value | Threshold Exceeded Event Name | +-------+---------------------------------------------------------+ | 0 | Reserved | | 1 | Address pool high threshold event | | 2 | Address pool low threshold event | | 3 | Address and port mapping high threshold event | | 4 | Address and port mapping per user high threshold event | | 5 | Global address mapping high threshold event | +-------+---------------------------------------------------------+ Table 4: Threshold Event 4.6. Templates for NAT Events The following is the template of events that will be logged. The events below are identified at the time of this writing, but the set of events is extensible. A NAT device that implements a given NAT event MUST support the mandatory IEs in the templates. Depending on the implementation and configuration, various IEs that are not mandatory can be included or ignored. 4.6.1. NAT44 Session Create and Delete Events These events will be generated when a NAT44 session is created or deleted. The template will be the same; theconfigured address pool has reachednatEvent will indicate whether it is aconfigured threshold.create or a delete event. Theper-user address and port mapping high thresholdfollowing isgenerated when a single user utilizes more address and port mapping thanaconfigured threshold. We don't tracktemplate of thelow threshold for per-userevent. The destination address and portmappings because,information is optional as required by [RFC6888]. However, when theports are freed,destination information is suppressed, theaddress will become available. The address pool low thresholdsession log eventwill then be triggered so thatcontains theglobal IPv4 address cansame information as the BIB event. In such cases, the NAT device SHOULD NOT send both BIB and session events. +----------------------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory | +----------------------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | sourceIPv4Address | 32 | Yes | | postNATSourceIPv4Address | 32 | Yes | | protocolIdentifier | 8 | Yes | | sourceTransportPort | 16 | Yes | | postNAPTSourceTransportPort | 16 | Yes | | destinationIPv4Address | 32 | No | | postNATDestinationIPv4Address | 32 | No | | destinationTransportPort | 16 | No | | postNAPTDestinationTransportPort | 16 | No | | natInstanceID | 32 | No | | vlanID/ingressVRFID | 16/32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +----------------------------------+-------------+-----------+ Table 5: NAT44 Session Delete/Create Template 4.6.2. NAT64 Session Create and Delete Events These events will bereclaimed. The global address mapping high threshold event isgenerated whenthe maximum number of mappings per usera NAT64 session is created or deleted. The following isreached foraNAT device doing paired-address pooling. +---------------------------------------------------------+--------+template of the event. +----------------------------------+-------------+-----------+ |Threshold Exceeded EventField Name |ValuesSize (bits) |+---------------------------------------------------------+--------+Mandatory |Reserved+----------------------------------+-------------+-----------+ |0timeStamp | 64 |Address pool high threshold eventYes |1| natEvent |Address pool low threshold event8 |2Yes | |Address and port mapping high threshold eventsourceIPv6Address |3128 | Yes |Address and port mapping per user high threshold event|4postNATSourceIPv4Address | 32 |Global address mapping high threshold eventYes |5|+---------------------------------------------------------+--------+protocolIdentifier | 8 | Yes | | sourceTransportPort | 16 | Yes | | postNAPTSourceTransportPort | 16 | Yes | | destinationIPv6Address | 128 | No | | postNATDestinationIPv4Address | 32 | No | | destinationTransportPort | 16 | No | | postNAPTDestinationTransportPort | 16 | No | | natInstanceID | 32 | No | | vlanID/ingressVRFID | 16/32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +----------------------------------+-------------+-----------+ Table4: Threshold6: NAT64 Session Create/Delete Event4.6. Templates for NAT Events The following is the template of events that will be logged. The events below are identified at the time of this writing, but the set of events is extensible. A NAT device that implements a given NAT event MUST support the mandatory IEs in the templates. Depending on the implementation and configuration, various IEs that are not mandatory can be included or ignored. 4.6.1.Template 4.6.3. NAT44 BIB Create and DeleteSessionEvents These events will be generated when a NAT44sessionBind entry is created or deleted. Thetemplate will be the same; the natEvent will indicate whether it is a create or a delete event. Thefollowing is a template of the event.The destination address and port information is optional as required by [RFC6888]. However, when the destination information is suppressed, the session log event contains the same information as the BIB event. In such cases, the NAT device SHOULD NOT send both BIB and session events. +----------------------------------+-------------+-----------++-----------------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+----------------------------------+-------------+-----------++-----------------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | sourceIPv4Address | 32 | Yes | | postNATSourceIPv4Address | 32 | Yes | | protocolIdentifier | 8 |Yes | | sourceTransportPort | 16 | Yes | | postNAPTSourceTransportPort | 16 | Yes | | destinationIPv4Address | 32 | No | | postNATDestinationIPv4Address | 32 |No | |destinationTransportPortsourceTransportPort | 16 | No | |postNAPTDestinationTransportPortpostNAPTSourceTransportPort | 16 | No | | natInstanceID | 32 | No | | vlanID/ingressVRFID |3216/32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No |+----------------------------------+-------------+-----------++-----------------------------+-------------+-----------+ Table5:7: NAT44Session Delete/CreateBIB Create/Delete Event Template4.6.2.4.6.4. NAT64 BIB Create and DeleteSessionEvents These events will be generated when a NAT64sessionBind entry is created or deleted. The following is a template of the event.+----------------------------------+-------------+-----------++-----------------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+----------------------------------+-------------+-----------++-----------------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | sourceIPv6Address | 128 | Yes | | postNATSourceIPv4Address | 32 | Yes | |protocolIdentifierprotocolIdentifier | 8 | No | | sourceTransportPort | 16 | No | | postNAPTSourceTransportPort | 16 | No | | natInstanceID | 32 | No | | vlanID/ingressVRFID | 16/32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +-----------------------------+-------------+-----------+ Table 8: NAT64 BIB Create/Delete Event Template 4.6.5. Addresses Exhausted Event This event will be generated when a NAT device runs out of global IPv4 addresses in a given pool of addresses. Typically, this event would mean that the NAT device won't be able to create any new translations until some addresses/ports are freed. This event SHOULD be rate-limited, as many packets hitting the device at the same time will trigger a burst of addresses exhausted events. The following is a template of the event. +---------------+-------------+-----------+ | Field Name |8Size (bits) |YesMandatory | +---------------+-------------+-----------+ |sourceTransportPorttimeStamp |1664 | Yes | |postNAPTSourceTransportPortnatEvent |168 | Yes | |destinationIPv6Address | 128 | No | | postNATDestinationIPv4AddressnatPoolID | 32 |No | | destinationTransportPort | 16 | No | | postNAPTDestinationTransportPort | 16 | NoYes | | natInstanceID | 32 | No || vlanID/ingressVRFID | 32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +----------------------------------+-------------+-----------++---------------+-------------+-----------+ Table6: NAT64 Session Create/Delete9: Addresses Exhausted Event Template4.6.3. NAT44 BIB Create and Delete Events These events4.6.6. Ports Exhausted Event This event will be generated when aNAT44 Bind entry is created or deleted.NAT device runs out of ports for a global IPv4 address. Port exhaustion shall be reported per protocol (UDP, TCP, etc.). This event SHOULD be rate-limited, as many packets hitting the device at the same time will trigger a burst of port exhausted events. The following is a template of the event.+-----------------------------+-------------+-----------++--------------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+-----------------------------+-------------+-----------++--------------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |sourceIPv4Address | 32 | Yes | |postNATSourceIPv4Address | 32 | Yes | | protocolIdentifier | 8 |No | | sourceTransportPort | 16 | No | | postNAPTSourceTransportPort | 16 | NoYes | | natInstanceID | 32 | No || vlanID/ingressVRFID | 32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +-----------------------------+-------------+-----------++--------------------------+-------------+-----------+ Table7: NAT44 BIB Create/Delete10: Ports Exhausted Event Template4.6.4. NAT64 BIB Create and Delete4.6.7. Quota Exceeded EventsThese eventsThis event will be generated when aNAT64 Bind entryNAT device cannot allocate resources as a result of an administratively defined policy. The Quota Exceeded event templates are described below. 4.6.7.1. Maximum Session Entries Exceeded The maximum session entries exceeded event iscreated or deleted.generated when the administratively configured NAT session limit is reached. The following isathe template of the event.+-----------------------------+-------------+-----------++-----------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+-----------------------------+-------------+-----------++-----------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |sourceIPv6AddressnatQuotaExceededEvent |12832 | Yes | |postNATSourceIPv4AddressmaxSessionEntries | 32 | Yes | |protocolIdentifier | 8 | No | | sourceTransportPort | 16 | No | | postNAPTSourceTransportPort | 16 | No | |natInstanceID | 32 | No || vlanID/ingressVRFID | 32 | No | | internalAddressRealm | octetArray | No | | externalAddressRealm | octetArray | No | +-----------------------------+-------------+-----------++-----------------------+-------------+-----------+ Table8: NAT64 BIB Create/Delete11: Session Entries Exceeded Event Template4.6.5. Addresses Exhausted Event This4.6.7.2. Maximum BIB Entries Exceeded The maximum BIB entries exceeded eventwill beis generated whena NAT device runs out of global IPv4 addresses in a given pool of addresses. Typically, this event would mean that the NAT device won't be able to create any new translations until some addresses/ports are freed. This event SHOULD be rate-limited, as many packets hitting the device atthesame time will trigger a burst of addresses exhausted events.administratively configured BIB entry limit is reached. The following isathe template of the event.+---------------+-------------+-----------++-----------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+---------------+-------------+-----------++-----------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natPoolIDnatQuotaExceededEvent | 32 | Yes | | maxBIBEntries | 32 | Yes | | natInstanceID | 32 | No |+---------------+-------------+-----------++-----------------------+-------------+-----------+ Table9: Addresses Exhausted12: BIB Entries Exceeded Event Template4.6.6. Ports Exhausted Event4.6.7.3. Maximum Entries per User Exceeded This eventwill beis generated when aNAT device runs out of ports for a global IPv4 address. Port exhaustion shall be reported per protocol (UDP, TCP, etc.). This event SHOULD be rate-limited, as many packets hitting the device atsingle user reaches thesame time will trigger a burst of port exhausted events.administratively configured NAT translation limit. The following isathe template of the event.+--------------------------+-------------+-----------++-----------------------+-------------+---------------+ | Field Name | Size (bits) | Mandatory |+--------------------------+-------------+-----------++-----------------------+-------------+---------------+ | timeStamp | 64 | Yes | |natEventnatEvent | 8 | Yes | | natQuotaExceededEvent | 32 | Yes | | maxEntriesPerUser |832 | Yes | |postNATSourceIPv4AddresssourceIPv4Address | 32 | Yes for NAT44 | |protocolIdentifiersourceIPv6Address |8128 | Yes for NAT64 | | natInstanceID | 32 | No |+--------------------------+-------------+-----------+| vlanID/ingressVRFID | 16/32 | No | +-----------------------+-------------+---------------+ Table10: Ports Exhausted13: Per-User Entries Exceeded Event Template4.6.7. Quota Exceeded Events This event will be generated when a NAT device cannot allocate resources as a result of an administratively defined policy. The quota exceeded event templates are described below. 4.6.7.1.4.6.7.4. MaximumSession EntriesActive Hosts or Subscribers ExceededThe maximum session entries exceededThis event is generated when the number of allowed hosts or subscribers reaches the administratively configuredNAT session limit is reached.limit. The following is the template of the event. +-----------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory | +-----------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | natQuotaExceededEvent | 32 | Yes | |configuredLimitmaxSubscribers | 32 | Yes | | natInstanceID | 32 | No | +-----------------------+-------------+-----------+ Table11: Session Entries14: Maximum Hosts/Subscribers Exceeded Event Template4.6.7.2.4.6.7.5. MaximumBIB EntriesFragments Pending Reassembly ExceededThe maximum BIB entries exceededThis event is generated when the number of fragments pending reassembly reaches the administratively configuredBIB entry limitlimit. Note that in the case of NAT64, when this condition isreached.detected in the IPv6-to- IPv4 direction, the IPv6 source address is mandatory in the template. Similarly, when this condition is detected in IPv4-to-IPv6 direction, the source IPv4 address is mandatory in the template below. The following is the template of the event.+-----------------------+-------------+-----------++-------------------------------+-------------+----------------+ | Field Name | Size (bits) | Mandatory |+-----------------------+-------------+-----------++-------------------------------+-------------+----------------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | natQuotaExceededEvent | 32 | Yes | |configuredLimitmaxFragmentsPendingReassembly | 32 | Yes | | sourceIPv4Address | 32 | Yes for NAT44 | | sourceIPv6Address | 128 | Yes for NAT64 | | natInstanceID | 32 | No |+-----------------------+-------------+-----------+| vlanID/ingressVRFID | 16/32 | No | | internalAddressRealm | octetArray | No | +-------------------------------+-------------+----------------+ Table12: BIB Entries15: Maximum Fragments Pending Reassembly Exceeded Event Template4.6.7.3. Maximum Entries per User Exceeded4.6.8. Threshold Reached Events This event will be generated when a NAT device reaches an operator- configured threshold when allocating resources. The Threshold Reached events are described in the section above. The following is a template of the individual events. 4.6.8.1. Address Pool High or Low Threshold Reached This event is generated whena single user reachestheadministratively configured NAT translation limit. The followinghigh or low threshold is reached for the address pool. The templateofis theevent. +-----------------------+-------------+---------------+same for both high and low threshold events +----------------------------------------------+--------+-----------+ | Field Name | Size(bits)| Mandatory |+-----------------------+-------------+---------------+| | (bits) | | +----------------------------------------------+--------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natQuotaExceededEventnatThresholdEvent | 32 | Yes | |configuredLimitnatPoolID | 32 | Yes | |sourceIPv4AddressaddressPoolHighThreshold/ | 32 | Yesfor NAT44| |sourceIPv6AddressaddressPoolLowThreshold |128|Yes for NAT64| | natInstanceID | 32 | No || vlanID/ingressVRFID | 32 | No | +-----------------------+-------------+---------------++----------------------------------------------+--------+-----------+ Table13: Per-User Entries Exceeded16: Address Pool High/Low Threshold Reached Event Template4.6.7.4. Maximum Active Hosts or Subscribers Exceeded4.6.8.2. Address and Port Mapping High Threshold Reached This event is generated when thenumber of allowed hosts or subscribers reaches the administratively configured limit. The followinghigh threshold is reached for thetemplate of the event. +-----------------------+-------------+-----------+address pool and ports. +----------------------------------------------+--------+-----------+ | Field Name | Size(bits)| Mandatory |+-----------------------+-------------+-----------+| | (bits) | | +----------------------------------------------+--------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natQuotaExceededEventnatThresholdEvent | 32 | Yes | |configuredLimitaddressPortMappingHighThreshold/ | 32 | Yes | | addressPortMappingLowThreshold | | | | natInstanceID | 32 | No |+-----------------------+-------------+-----------++----------------------------------------------+--------+-----------+ Table14: Maximum Hosts/Subscribers Exceeded17: Address Port High Threshold Reached Event Template4.6.7.5. Maximum Fragments Pending Reassembly Exceeded4.6.8.3. Address and Port Mapping per User High Threshold Reached This event is generated when thenumber of fragments pending reassembly reaches the administratively configured limit. Note that in the case of NAT64, when this condition is detected in the IPv6-to- IPv4 direction, the IPv6 source address is mandatory in the template. Similarly, when this conditionhigh threshold isdetected in IPv4-to-IPv6 direction,reached for thesource IPv4per-user addressis mandatory in the template below. The following is the template of the event. +-----------------------+-------------+----------------+pool and ports. +----------------------------------------------+--------+-----------+ | Field Name | Size(bits)| Mandatory |+-----------------------+-------------+----------------+| | (bits) | | +----------------------------------------------+--------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natQuotaExceededEventnatThresholdEvent | 32 | Yes | |configuredLimitaddressPortMappingHighThreshold/ | 32 | Yes | | addressPortMappingLowThreshold | | | | sourceIPv4Address | 32 | Yes for | | | | NAT44 | | sourceIPv6Address | 128 | Yes forNAT64| |natInstanceID|32|NoNAT64 | |vlanID/ingressVRFIDnatInstanceID | 32 | No | |internalAddressRealmvlanID/ingressVRFID |octetArray16/32 | No |+-----------------------+-------------+----------------++----------------------------------------------+--------+-----------+ Table15: Maximum Fragments Pending Reassembly Exceeded Event Template 4.6.8.18: Address and Port Mapping per User High Threshold ReachedEvents This event will be generated when a NAT device reaches an operator- configured threshold when allocating resources. The threshold reached events are described in the section above. The following is a template of the individual events. 4.6.8.1.Event Template 4.6.8.4. Global AddressPoolMapping Highor LowThreshold Reached This event is generated when the highor lowthreshold is reached for the per-user addresspool. The template is the same for both highpool andlow threshold events +-------------------+-------------+-----------+ports. This is generated only by NAT devices that use a paired-address-pooling behavior. +-----------------------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory |+-------------------+-------------+-----------++-----------------------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | natThresholdEvent | 32 | Yes | |natPoolIDglobalAddressMappingHighThreshold | 32 | Yes | |configuredLimitnatInstanceID | 32 |YesNo | |natInstanceIDvlanID/ingressVRFID |3216/32 | No |+-------------------+-------------+-----------++-----------------------------------+-------------+-----------+ Table16:19: Global AddressPool High/LowMapping High Threshold Reached Event Template4.6.8.2.4.6.9. Address Binding Create andPort Mapping High Threshold Reached This event isDelete Events These events will be generated when a NAT device binds a local address with a global address and when thehigh thresholdglobal address isreached forfreed. A NAT device will generate theaddress pool and ports. +-------------------+-------------+-----------+binding events when it receives the first packet of the first flow from a host in the private realm. +--------------------------+-------------+---------------+ | Field Name | Size (bits) | Mandatory |+-------------------+-------------+-----------++--------------------------+-------------+---------------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natThresholdEventsourceIPv4Address | 32 | Yes for NAT44 | | sourceIPv6Address | 128 | Yes for NAT64 | |configuredLimitpostNATSourceIPv4Address | 32 | Yes | | natInstanceID | 32 | No |+-------------------+-------------+-----------++--------------------------+-------------+---------------+ Table17:20: NAT AddressPort High Threshold Reached EventBinding Template4.6.8.3. Address and4.6.10. PortMapping per User High Threshold ReachedBlock Allocation and De-allocation This event will be generated when a NAT device allocates/de-allocates ports in a bulk fashion, as opposed to allocating a port on a per- flow basis. portRangeStart represents the starting value of the range. portRangeEnd represents the ending value of the range. NAT devices would do this in order to reduce logs and to potentially limit the number of connections a subscriber isgenerated whenallowed to use. In thehigh thresholdfollowing Port Block allocation template, the portRangeStart and portRangeEnd MUST be specified. It isreachedup to the implementation to choose to consolidate log records in case two consecutive port ranges for theper-user address pool and ports. +---------------------+-------------+---------------+same user are allocated or freed. +--------------------------+-------------+---------------+ | Field Name | Size (bits) | Mandatory |+---------------------+-------------+---------------++--------------------------+-------------+---------------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | |natThresholdEventsourceIPv4Address | 32 | Yes for NAT44 | |configuredLimitsourceIPv6Address |32128 | Yes for NAT64 | |sourceIPv4AddresspostNATSourceIPv4Address | 32 | Yesfor NAT44| |sourceIPv6AddressportRangeStart |12816 | Yesfor NAT64| |natInstanceIDportRangeEnd |3216 | No | |vlanID/ingressVRFIDnatInstanceID | 32 | No |+---------------------+-------------+---------------++--------------------------+-------------+---------------+ Table18: Address and21: NAT PortMapping per User High Threshold ReachedBlock Allocation Event Template4.6.8.4. Global Address Mapping High Threshold Reached5. Management Considerations This section considers requirements for management of the log system to support logging of the events described above. It first covers requirements applicable to log management in general. Any additional standardization required to fulfill these requirements is out of scope of the present document. Some management considerations are covered in [NAT-LOG]. This document covers the additional considerations. 5.1. Ability to Collect Events from Multiple NAT Devices An IPFIX Collector MUST be able to collect events from multiple NAT devices and decipher events based on the Observation Domain ID in the IPFIX header. 5.2. Ability to Suppress Events The exhaustion events can be overwhelming during traffic bursts; hence, they SHOULD be handled by the NAT devices to rate-limit them before sending them to the Collectors. For example, when the port exhaustion happens during bursty conditions, instead of sending a port exhaustion event for every packet, the exhaustion events SHOULD be rate-limited by the NAT device. 6. IANA Considerations 6.1. Information Elements IANA has registered the following IEs in the "IPFIX Information Elements" registry at [IPFIX-IANA]. 6.1.1. natInstanceID ElementID: 463 Name: natInstanceID Description: Thisevent is generated whenInformation Element uniquely identifies an Instance of thehigh thresholdNAT that runs on a NAT middlebox function after the packet passes the Observation Point. natInstanceID isreacheddefined in [RFC7659]. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC791] for theper-userdefinition of the IPv4 source addresspool and ports.field. See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes. 6.1.2. internalAddressRealm ElementID: 464 Name: internalAddressRealm Description: This Information Element represents the internal address realm where the packet isgenerated only by NAT devices that use a paired-address-pooling behavior. +---------------------+-------------+-----------+ | Field Name | Size (bits) | Mandatory | +---------------------+-------------+-----------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | natThresholdEvent | 32 | Yes | | configuredLimit | 32 | Yes | | natInstanceID | 32 | No | | vlanID/ingressVRFID | 32 | No | +---------------------+-------------+-----------+ Table 19: Global Address Mapping High Threshold Reached Event Template 4.6.9. Address Binding Create and Delete Events These events will be generated whenoriginated from or destined to. By definition, a NATdevice binds a localmapping can be created from two addresswithrealms, one from internal and one from external. Realms are implementation dependent and can represent aglobal addressVirtual Routing and Forwarding (VRF) ID, a VLAN ID, or some unique identifier. Realms are optional and, when left unspecified, would mean that the external and internal realms are the same. Abstract Data Type: octetArray Data Type Semantics: identifier Reference: See [RFC791] for theglobaldefinition of the IPv4 source addressis freed. A NAT device will generatefield. See [RFC3022] for thebinding events when it receivesdefinition of NAT. See [RFC3234] for thefirst packetdefinition of middleboxes. 6.1.3. externalAddressRealm ElementID: 465 Name: externalAddressRealm Description: This Information Element represents thefirst flowexternal address realm where the packet is originated froma hostor destined to. The detailed definition is in theprivate realm. +--------------------------------+-------------+---------------+ | Field Name | Size (bits) | Mandatory | +--------------------------------+-------------+---------------+ | timeStamp | 64 | Yes | | natEvent | 8 | Yes | | sourceIPv4Address | 32 | Yes for NAT44 | | sourceIPv6Address | 128 | Yes for NAT64 | | Translated Source IPv4 Address | 32 | Yes | | natInstanceID | 32 | No | +--------------------------------+-------------+---------------+ Table 20: NAT Address Binding Template 4.6.10. Port Block Allocation and De-allocation This event will be generated when a NAT device allocates/de-allocates ports in a bulk fashion,internal address realm asopposed to allocating a port on a per- flow basis. portRangeStart representsspecified above. Abstract Data Type: octetArray Data Type Semantics: identifier Reference: See [RFC791] for thestarting valuedefinition of therange. portRangeEnd representsIPv4 source address field. See [RFC3022] for theending valuedefinition of NAT. See [RFC3234] for therange.definition of middleboxes. 6.1.4. natQuotaExceededEvent ElementID: 466 Name: natQuotaExceededEvent Description: This Information Element identifies the type of a NATdevices would doQuota Exceeded event. Values for this Information Element are listed inorder to reduce logs and to potentially limitthenumber of connections a subscriber is allowed to use. In"NAT Quota Exceeded Event Type" registry, see [IPFIX-IANA]. Initial values in thefollowing Port Block allocation template,registry are defined by theportRangeStart and portRangeEnd MUSTtable below. New assignments of values will bespecified. It is up to the implementationadministered by IANA and are subject tochooseExpert Review [RFC8126]. Experts need toconsolidate log records in case two consecutive port rangescheck definitions of new values forthe same user are allocated or freed. +--------------------------------+-------------+---------------+completeness, accuracy, and redundancy. +--------+---------------------------------------+ |FieldValue | Quota Exceeded Event Name |Size (bits)+--------+---------------------------------------+ |Mandatory0 |+--------------------------------+-------------+---------------+Reserved |timeStamp|641 |YesMaximum session entries | |natEvent2 |8Maximum BIB entries |Yes| 3 |sourceIPv4AddressMaximum entries per user |32|Yes for NAT444 | Maximum active hosts or subscribers |sourceIPv6Address|1285 |YesMaximum fragments pending reassembly | +--------+---------------------------------------+ Note: This is the same as Table 3. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC791] forNAT64the definition of the IPv4 source address field. See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes. 6.1.5. natThresholdEvent ElementID: 467 Name: natThresholdEvent Description: This Information Element identifies a type of a NAT Threshold event. Values for this Information Element are listed in the "NAT Threshold Event Type" registry, see [IPFIX-IANA]. Initial values in the registry are defined by the table below. New assignments of values will be administered by IANA and are subject to Expert Review [RFC8126]. Experts need to check definitions of new values for completeness, accuracy, and redundancy. +--------+---------------------------------------------------------+ | Value |Translated Source IPv4 AddressThreshold Exceeded Event Name |32+--------+---------------------------------------------------------+ |Yes0 | Reserved |portRangeStart|161 | Address pool high threshold event | | 2 | Address pool low threshold event |Yes| 3 |portRangeEndAddress and port mapping high threshold event |16|No4 | Address and port mapping per user high threshold event |natInstanceID|325 |NoGlobal address mapping high threshold event |+--------------------------------+-------------+---------------+ Table 21: NAT Port Block Allocation Event Template 5. Management Considerations+--------+---------------------------------------------------------+ Note: Thissection considers requirementsis the same as Table 4. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC791] formanagementthe definition of thelog system to support loggingIPv4 source address field. See [RFC3022] for the definition of NAT. See [RFC3234] for theevents described above. It first covers requirements applicable to log management in general. Any additional standardization required to fulfill these requirements is outdefinition ofscopemiddleboxes. 6.1.6. natEvent The original definition ofthe present document. Some management considerations are covered in [NAT-LOG]. This document covers the additional considerations. 5.1. Ability to Collect Events from Multiple NAT Devices An IPFIX collector MUST be able to collect events from multiple NAT devicesthis Information Element specified only three values: 1, 2, anddecipher events based on the Observation Domain ID in the IPFIX header. 5.2. Ability3. This definition has been replaced by a registry, toSuppress Events The exhaustion eventswhich new values can beoverwhelming during traffic bursts; hence, they SHOULD be handled by the NAT devices to rate-limit them before sending them to the collectors. For example, when the port exhaustion happens during bursty conditions, insteadadded. The semantics ofsending a port exhaustion event for every packet, the exhaustion events SHOULD be rate-limited bytheNAT device. 6. IANA Considerations 6.1. Information Elementsthree originally defined values remain unchanged. IANAhas registered the following IEs inmaintains the"IPFIX Information Elements""NAT Event Type (Value 230)" registry for values of this Information Element at [IPFIX-IANA].6.1.1. natInstanceIDElementID: 230 Name:natInstanceIDnatEvent Description: This Information Elementuniquelyidentifiesan Instance of thea NATthat runs onevent. This IE identifies the type of a NATmiddlebox function afterevent. Examples of NAT events include, but are not limited to, NAT translation create, NAT translation delete, Threshold Reached, or Threshold Exceeded, etc. Values for this Information Element are listed in thepacket passes"NAT Event Type" registry, see [IPFIX-IANA]. The NAT event values in theObservation Point. natInstanceID isregistry are defined by Table 2 in[RFC7659].Section 4.3. New assignments of values will be administered by IANA and are subject to Expert Review [RFC8126]. Experts need to check definitions of new values for completeness, accuracy, and redundancy. Abstract Data Type:unsigned32unsigned8 Data Type Semantics: identifier Reference: See[RFC0791][RFC3022] for the definition of NAT. See [RFC3234] for theIPv4 source address field.definition of middleboxes. See RFC 8158 for the definitions of values 4-16. 6.1.7. maxSessionEntries ElementID: 471 Name: maxSessionEntries Description: This element represents the maximum session entries that can be created by the NAT device. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes.6.1.2. internalAddressRealm6.1.8. maxBIBEntries ElementID: 472 Name:internalAddressRealmmaxBIBEntries Description: ThisInformation Elementelement represents theinternal address realm where the packet is originated from or destined to. By definition, a NAT mappingmaximum BIB entries that can be createdfrom two address realms, one from internal and one from external. Realms are implementation dependent and can represent a Virtual Routing and Forwarding (VRF) ID, a VLAN ID, or some unique identifier. Realms are optional and, when left unspecified, would mean that the external and internal realms areby thesame.NAT device. Abstract Data Type:octetArrayunsigned32 Data Type Semantics: identifier Reference: See[RFC0791][RFC3022] for the definition of NAT. See [RFC3234] for theIPv4 source address field.definition of middleboxes. 6.1.9. maxEntriesPerUser ElementID: 473 Name: maxEntriesPerUser Description: This element represents the maximum NAT entries that can be created per user by the NAT device. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes.6.1.3. externalAddressRealm6.1.10. maxSubscribers ElementID: 474 Name:externalAddressRealmmaxSubscribers Description: ThisInformation Elementelement represents theexternal address realm where the packet is originated frommaximum subscribers ordestined to. The detailed definition is inmaximum hosts that are allowed by theinternal address realm as specified above.NAT device. Abstract Data Type:octetArrayunsigned32 Data Type Semantics: identifier Reference: See[RFC0791] for the definition of the IPv4 source address field. See[RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes.6.1.4. natQuotaExceededEvent Values of this Information Element are defined in the "NAT Quota Exceeded Event Type (Value 466)" registry maintained by IANA at [IPFIX-IANA]. New assignments of values will be administered by IANA and are subject to Expert Review [RFC5226]. Experts need to check definitions of new values for completeness, accuracy, and redundancy.6.1.11. maxFragmentsPendingReassembly ElementID: 475 Name:natQuotaExceededEventmaxFragmentsPendingReassembly Description: ThisInformation Element identifieselement represents the maximum fragments that thetype of aNATquota exceeded event. Valuesdevice can store forthis Information Element are listed inreassembling theNAT Quota Exceeded Eventpacket. Abstract Data Type: unsigned32 Data Typeregistry, see [IPFIX-IANA]. Initial values inSemantics: identifier Reference: See [RFC3022] for theregistry are defined bydefinition of NAT. See [RFC3234] for thetable below. +---------------------------------------+--------+ | Quota Exceeded Event Name | Values | +---------------------------------------+--------+ | Reserved | 0 | | Maximum session entries | 1 | | Maximum BIB entries | 2 | | Maximum entries per user | 3 | | Maximum active hosts or subscribers | 4 | | Maximum fragments pending reassembly | 5 | +---------------------------------------+--------+ Table 22: IPFIX-IANAdefinition of middleboxes. 6.1.12. addressPoolHighThreshold ElementID: 476 Name: addressPoolHighThreshold Description: This element represents the high threshold value of the number of public IP addresses in the address pool. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See[RFC0791][RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes. 6.1.13. addressPoolLowThreshold ElementID: 477 Name: addressPoolLowThreshold Description: This element represents the low threshold value of the number of public IP addresses in theIPv4 sourceaddressfield.pool. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes.6.1.5. natThresholdEvent Values6.1.14. addressPortMappingHighThreshold ElementID: 478 Name: addressPortMappingHighThreshold Description: This element represents the high threshold value ofthis Information Element are defined inthe"NAT Threshold Event Type (Value 467)" registry maintained by IANA at [IPFIX-IANA]. New assignmentsnumber ofvalues will be administered by IANAaddress andare subject to Expert Review [RFC5226]. Experts need to check definitionsport mappings. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC3022] for the definition ofnew valuesNAT. See [RFC3234] forcompleteness, accuracy, and redundancy.the definition of middleboxes. 6.1.15. addressPortMappingLowThreshold ElementID: 479 Name:natThresholdEventaddressPortMappingLowThreshold Description: ThisInformation Element identifies a type of a NAT threshold event. Values for this Information Element are listed in the "NAT Threshold Event Type" registry, see [IPFIX-IANA]. Initial values in the registry are defined byelement represents thetable below. +---------------------------------------------------------+--------+ | Threshold Exceeded Event Name | Values | +---------------------------------------------------------+--------+ | Reserved | 0 | | Address pool high threshold event | 1 | | Address poollow thresholdevent | 2 | | Address and port mapping high threshold event | 3 | | Addressvalue of the number of address and portmapping per user high threshold event | 4 | | Global Address mappingmappings. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes. 6.1.16. addressPortMappingPerUserHighThreshold ElementID: 480 Name: addressPortMappingPerUserHighThreshold Description: This element represents the high thresholdevent | 5 | +---------------------------------------------------------+--------+ Table 23: IPFIX-IANAvalue of the number of address and port mappings that a single user is allowed to create on a NAT device. Abstract Data Type: unsigned32 Data Type Semantics: identifier Reference: See[RFC0791] for the definition of the IPv4 source address field. See[RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes.6.1.6. natEvent The original definition of this Information Element specified only three values: 1, 2, and 3. This definition has been replaced by a registry, to which new values can be added. The semantics of the three originally defined values remain unchanged. IANA maintains the "NAT Event Type (Value 230)" registry for values of this Information Element at [IPFIX-IANA]. New assignments of values will be administered by IANA and are subject to Expert Review [RFC5226]. Experts need to check definitions of new values for completeness, accuracy, and redundancy.6.1.17. globalAddressMappingHighThreshold ElementID: 481 Name:natEventglobalAddressMappingHighThreshold Description: ThisInformation Element identifies a NAT event. This IE identifieselement represents thetype of a NAT event. Exampleshigh threshold value ofNAT events include, but are not limited to, creation or deletionthe number of address and port mappings that aNAT translation entry,single user is allowed to create on athreshold reached or exceeded, etc. Values for this Information Element are listed in the NAT Event Type registry, see [IPFIX-IANA]. TheNATevent values in the registry are defined by the Table 2device inSection 4.3.a paired address pooling behavior. Abstract Data Type:unsigned8unsigned32 Data Type Semantics: identifierElement ID: 230Reference: See [RFC3022] for the definition of NAT. See [RFC3234] for the definition of middleboxes. See[RFC8158][RFC4787] for thedefinitionsdefinition ofvalues 4-16.paired address pooling behavior. 7. Security Considerations The security considerations listed in detail for IPFIX in [RFC7011] apply to this document as well. As described in [RFC7011], the messages exchanged between the NAT device and thecollectorCollector MUST be protected to provide confidentiality, integrity, and authenticity. Without those characteristics, the messages are subject to various kinds of attacks. These attacks are described in great detail in [RFC7011]. This document re-emphasizes the use of Transport Layer Security (TLS) or Datagram Transport Layer Security (DTLS) for exchanging the log messages between the NAT device and thecollector.Collector. The log events sent in cleartext can result in confidential data being exposed to attackers, who could then spoof log events based on the information in cleartext messages. Hence, the log events SHOULD NOT be sent in cleartext. The logging of NAT events can result in privacy concerns as a result of exporting information such as the source address and port information. The logging of destination information can also cause privacy concerns, but it has been well documented in [RFC6888]. A NAT device can choose to operate in various logging modes if it wants to avoid logging of private information. ThecollectorCollector that receives the information can also choose to mask the private information but generate reports based on abstract data. It is outside the scope of this document to address the implementation of logging modes for privacy considerations. 8. References 8.1. 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>.<https://www.rfc-editor.org/info/rfc2119>. [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>.<https://www.rfc-editor.org/info/rfc4787>. [RFC5382] Guha, S., Ed., Biswas, K., Ford, B., Sivakumar, S., and P. Srisuresh, "NAT Behavioral Requirements for TCP", BCP 142, RFC 5382, DOI 10.17487/RFC5382, October 2008,<http://www.rfc-editor.org/info/rfc5382>.<https://www.rfc-editor.org/info/rfc5382>. [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, April 2011,<http://www.rfc-editor.org/info/rfc6146>.<https://www.rfc-editor.org/info/rfc6146>. [RFC6302] Durand, A., Gashinsky, I., Lee, D., and S. Sheppard, "Logging Recommendations for Internet-Facing Servers", BCP 162, RFC 6302, DOI 10.17487/RFC6302, June 2011,<http://www.rfc-editor.org/info/rfc6302>.<https://www.rfc-editor.org/info/rfc6302>. [RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa, A., and H. Ashida, "Common Requirements for Carrier-Grade NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888, April 2013,<http://www.rfc-editor.org/info/rfc6888>.<https://www.rfc-editor.org/info/rfc6888>. [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, September 2013,<http://www.rfc-editor.org/info/rfc7011>.<https://www.rfc-editor.org/info/rfc7011>. [RFC7659] Perreault, S., Tsou, T., Sivakumar, S., and T. Taylor, "Definitions of Managed Objects for Network Address Translators (NATs)", RFC 7659, DOI 10.17487/RFC7659, October 2015,<http://www.rfc-editor.org/info/rfc7659>.<https://www.rfc-editor.org/info/rfc7659>. 8.2. Informative References [IPFIX-IANA] IANA, "IPFIX Information Elements", <http://www.iana.org/assignments/ipfix>. [NAT-LOG] Chen, Z., Zhou, C., Tsou, T., and T. Taylor, Ed., "Syslog Format for NAT Logging", Work in Progress, draft-ietf- behave-syslog-nat-logging-06, January 2014.[RFC0791][RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981,<http://www.rfc-editor.org/info/rfc791>.<https://www.rfc-editor.org/info/rfc791>. [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>.<https://www.rfc-editor.org/info/rfc2663>. [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network Address Translator (Traditional NAT)", RFC 3022, DOI 10.17487/RFC3022, January 2001,<http://www.rfc-editor.org/info/rfc3022>.<https://www.rfc-editor.org/info/rfc3022>. [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002,<http://www.rfc-editor.org/info/rfc3234>. [RFC5226] Narten, T.<https://www.rfc-editor.org/info/rfc3234>. [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, DOI 10.17487/RFC5424, March 2009, <https://www.rfc-editor.org/info/rfc5424>. [RFC8126] Cotton, M., Leiba, B., andH. Alvestrand,T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>. [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,8126, DOI10.17487/RFC5424, March 2009, <http://www.rfc-editor.org/info/rfc5424>.10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>. Acknowledgements Thanks to Dan Wing, Selvi Shanmugam, Mohamed Boucadir, Jacni Qin, Ramji Vaithianathan, Simon Perreault, Jean-Francois Tremblay, Paul Aitken, Julia Renouard, Spencer Dawkins, and Brian Trammell for their review and comments. Authors' Addresses Senthil Sivakumar Cisco Systems 7100-8 Kit Creek Road Research Triangle Park, NC 27709 United States of America Phone: +1 919 392 5158 Email: ssenthil@cisco.comRenaldoReinaldo Penno Cisco Systems 170 W Tasman Drive San Jose, CA 95035 United States of America Email: repenno@cisco.com