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Versions: (draft-sivakumar-behave-nat-logging) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 8158

Behave                                                      S. Sivakumar
Internet-Draft                                                  R. Penno
Intended status: Standards Track                           Cisco Systems
Expires: July 13, 2017                                   January 9, 2017


           IPFIX Information Elements for logging NAT Events
                 draft-ietf-behave-ipfix-nat-logging-13

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.  The logs are essential in many cases 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
   log the information using proprietary formats and hence it is
   difficult to expect a consistent behavior.  The lack of a consistent
   way to log the data makes it difficult to write the collector
   applications that would receive this data and process it to present
   useful information.  This document describes the formats for logging
   of NAT events.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 13, 2017.

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



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   (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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Deployment  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Event based logging . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Logging of destination information  . . . . . . . . . . .   6
     4.2.  Information Elements  . . . . . . . . . . . . . . . . . .   6
     4.3.  Definition of NAT Events  . . . . . . . . . . . . . . . .   8
     4.4.  Quota exceeded Event types  . . . . . . . . . . . . . . .   9
     4.5.  Threshold reached Event types . . . . . . . . . . . . . .  10
     4.6.  Templates for NAT Events  . . . . . . . . . . . . . . . .  11
       4.6.1.  NAT44 create and delete session events  . . . . . . .  11
       4.6.2.  NAT64 create and delete session events  . . . . . . .  12
       4.6.3.  NAT44 BIB create and delete events  . . . . . . . . .  13
       4.6.4.  NAT64 BIB create and delete events  . . . . . . . . .  13
       4.6.5.  Addresses Exhausted event . . . . . . . . . . . . . .  14
       4.6.6.  Ports Exhausted event . . . . . . . . . . . . . . . .  14
       4.6.7.  Quota exceeded events . . . . . . . . . . . . . . . .  15
         4.6.7.1.  Maximum session entries exceeded  . . . . . . . .  15
         4.6.7.2.  Maximum BIB entries exceeded  . . . . . . . . . .  15
         4.6.7.3.  Maximum entries per user exceeded . . . . . . . .  15
         4.6.7.4.  Maximum active host or subscribers exceeded . . .  16
         4.6.7.5.  Maximum fragments pending reassembly exceeded . .  16
       4.6.8.  Threshold reached events  . . . . . . . . . . . . . .  17
         4.6.8.1.  Address pool high or low threshold reached  . . .  17
         4.6.8.2.  Address and port high threshold reached . . . . .  17
         4.6.8.3.  Per-user Address and port high threshold reached   18
         4.6.8.4.  Global Address mapping high threshold reached . .  18
       4.6.9.  Address binding create and delete events  . . . . . .  19
       4.6.10. Port block allocation and de-allocation . . . . . . .  19
   5.  Management Considerations . . . . . . . . . . . . . . . . . .  20
     5.1.  Ability to collect events from multiple NAT devices . . .  20
     5.2.  Ability to suppress events  . . . . . . . . . . . . . . .  20
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     7.1.  Information Elements  . . . . . . . . . . . . . . . . . .  21
       7.1.1.  natInstanceID . . . . . . . . . . . . . . . . . . . .  21



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       7.1.2.  internalAddressRealm  . . . . . . . . . . . . . . . .  21
       7.1.3.  externalAddressRealm  . . . . . . . . . . . . . . . .  22
       7.1.4.  natQuotaExceededEvent . . . . . . . . . . . . . . . .  22
       7.1.5.  natThresholdEvent . . . . . . . . . . . . . . . . . .  23
       7.1.6.  natEvent  . . . . . . . . . . . . . . . . . . . . . .  24
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  25
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   The IPFIX Protocol [RFC7011] defines a generic push mechanism for
   exporting information and events.  The IPFIX Information Model
   [IPFIX-IANA] defines a set of standard IEs which can be carried by
   the IPFIX protocol.  This document details the IPFIX Information
   Elements(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 [I-D.ietf-behave-syslog-nat-logging] 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 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 is it an IETF standard that meets all
   the needs for a reliable logging mechanism.  IPFIX provides the
   flexibility to the logging device to define the data sets that it is
   logging.  The IEs specified for logging must be the same irrespective
   of the encoding mechanism used.

1.1.  Terminology

   The usage of the term "NAT device" in this document refer to any
   NAT44 and NAT64 devices.  The usage of the term "collector" refers to
   any device that receives the binary data from a NAT device and
   converts that into meaningful information.  This document uses the
   term "Session" as it is defined in [RFC2663] and the term Binding
   Information Base (BIB) as it is defined in [RFC6146].  The usage of
   the term Information Element (IE) is defined in [RFC7011].  The term
   Carrier Grade NAT refers to a large scale NAT device as described in
   [RFC6888]




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   The IPFIX Information Elements that are NAT specific are created with
   NAT terminology.  In order to avoid creating duplicate IEs, IEs are
   reused if they convey the same meaning.  This document uses the term
   timestamp for the Information element which defines the time when an
   event is logged, this is the same as IPFIX term
   observationTimeMilliseconds as described in [IPFIX-IANA].  Since
   observationTimeMilliseconds is not self explanatory for NAT
   implementors, this document uses the term timeStamp.  This document
   refers to event templates, that refers to IPFIX template records.
   This document refers to log events that refers to IPFIX Flow records.

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
   the transport protocol like TCP, UDP or SCTP that is to be used to
   log NAT events.  The logs SHOULD be reliably sent to the collector to
   ensure that the log events are not lost.  The choice of the actual
   transport protocol is beyond the scope of this document.

   The existing IANA IPFIX IEs registry [IPFIX-IANA] already has
   assignments for most of the NAT logging events.  This document uses
   the allocated IPFIX IEs and will request IANA for the ones that are
   defined in this document but not yet allocated.

   This document assumes that the NAT device will use the existing IPFIX
   framework to send the log events to the 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 the collector application is 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.






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3.  Deployment

   NAT logging based on IPFIX uses binary encoding and hence 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 a collector that processes the binary data and
   requires a network management application that converts this binary
   data to a human readable format.

   A collector may receive NAT events from multiple CGN devices.  The
   collector distinguishes between the devices using the source IP
   address, source port, and Observation Domain ID in the IPFIX header.
   The collector can decide to store the information based on the
   administrative policies that are inline with the operator and the
   local juridiction.  The retention policy is not dictated by the
   exporter and is left to the policies that are defined at the
   collector.

   A collector 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, need for additional IP addresses 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 transition as 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 or 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 are provided in Table 2.  Each of
   these events SHOULD be logged, unless they are administratively
   prohibited.  A NAT device MAY log these events to multiple collectors
   if redundancy is required.  The network administrator will specify
   the collectors to which the log records are to be sent.  It is
   necessary to preserve the list of collectors and its associated
   information like the IPv4/IPv6 address, port and protocol across



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   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 specs as specified in RFC 7011.

4.1.  Logging of destination information

   Logging of destination information in a NAT event has been discussed
   in [RFC6302] and [RFC6888].  Logging of 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 of the
   source and destination addresses result in loss of privacy.  Logging
   of destination addresses and ports, pre or post NAT, SHOULD NOT be
   done [RFC6888].  However, this draft 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,

   {sourceIPv4Adress, postNATSourceIPv4Address, destinationIpv4Address,
   postNATDestinationIPv4Address, sourceTransportPort,
   postNAPTSourceTransportPort, destinationTransportPort,
   postNAPTDestTransportPort, 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 the
   collector MUST support receiving multiple templates from the same
   source.














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   The following is the table of all the IEs that a NAT device would
   need to export the events.  The formats of the IEs and the IPFIX IDs
   are listed below.  Some of the IPFIX IEs are not yet assigned.  The
   detailed description of these fields that are requested are in the
   IANA considerations section.

   +--------------------------------+------------+-------+-------------+
   |           Field Name           |       Size |  IANA | Description |
   |                                |     (bits) | IPFIX |             |
   |                                |            |    ID |             |
   +--------------------------------+------------+-------+-------------+
   |           timeStamp            |         64 |   323 | System Time |
   |                                |            |       |   when the  |
   |                                |            |       |    event    |
   |                                |            |       |   occured.  |
   |         natInstanceId          |         32 |   TBD |     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    |
   | postNAPTdestinationTransportPo |         16 |   228 |  Translated |
   |               rt               |            |       | Destination |
   |                                |            |       |     port    |



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   |       sourceIPv6Address        |        128 |    27 | Source IPv6 |
   |                                |            |       |   address   |
   |     destinationIPv6Address     |        128 |    28 | Destination |
   |                                |            |       |     IPv6    |
   |                                |            |       |   address   |
   |    postNATSourceIPv6Address    |        128 |   281 |  Translated |
   |                                |            |       | source IPv6 |
   |                                |            |       |   addresss  |
   | postNATDestinationIPv6Address  |        128 |   282 |  Translated |
   |                                |            |       | Destination |
   |                                |            |       |     IPv6    |
   |                                |            |       |   address   |
   |      internalAddressRealm      | OctetArray |   TBD |    Source   |
   |                                |            |       |   Address   |
   |                                |            |       |    Realm    |
   |      externalAddressRealm      | OctetArray |   TBD | Destination |
   |                                |            |       |   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 |   TBD | Limit event |
   |                                |            |       |  identifier |
   |       natThresholdEvent        |         32 |   TBD |  Threshold  |
   |                                |            |       |    event    |
   |                                |            |       |  identifier |
   +--------------------------------+------------+-------+-------------+

                      Table 1: Template format Table

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 IANA
   registry in http://www.iana.org/assignments/ipfix/ipfix.xml.  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.  These values
   were defined prior to the existence of this draft and outside the



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   IETF working group.  These events are not standalone and require more
   information need to be conveyed to qualify the event.  For example,
   the NAT Translation create event does not specify if it is a NAT44 or
   NAT64.  As a result the Behave WG decided to have explicit definition
   for each one of the unique events.  The historic events are listed
   here for the purpose of completeness and are already defined in the
   IPFIX IANA registry.  Any compliant implementation SHOULD NOT
   implement the events that are marked historic.

             +-------------------------------------+--------+
             |              Event Name             | Values |
             +-------------------------------------+--------+
             |  NAT Translation create (Historic)  |      1 |
             |  NAT Translation Delete (Historic)  |      2 |
             |       NAT Addresses exhausted       |      3 |
             |         NAT44 Session create        |      4 |
             |         NAT44 Session delete        |      5 |
             |         NAT64 Session create        |      6 |
             |         NAT64 Session delete        |      7 |
             |           NAT44 BIB create          |      8 |
             |           NAT44 BIB delete          |      9 |
             |           NAT64 BIB create          |     10 |
             |           NAT64 BIB delete          |     11 |
             |         NAT ports exhausted         |     12 |
             |            Quota exceeded           |     13 |
             |        Address binding create       |     14 |
             |        Address binding delete       |     15 |
             |        Port block allocation        |     16 |
             |       Port block de-allocation      |     17 |
             |          Threshold reached          |     18 |
             +-------------------------------------+--------+

                        Table 2: NAT Event ID table

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 has 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
   limit reached or maximum subscribers limit reached and Maximum
   Fragments pending reassembly limit reached.






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            +---------------------------------------+--------+
            |       Quota Exceeded Event Name       | Values |
            +---------------------------------------+--------+
            |        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 3: Quota Exceeded event table

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 Quota Exceeded and
   the Threshold reached events is that, once the Quota exceeded events
   are hit, the packets are dropped or mappings wont be created etc,
   whereas, the threshold 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 the operator might have to add
   more addresses to the pool or an indication that 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
   the number 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 uses 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 threhold event
   will then be triggered so that the IPv4 global address can be
   reclaimed.





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   The Global address mapping high threshold event is generated when the
   maximum mappings per-user is reached for a NAT device doing paired
   address pooling.

   +---------------------------------------------------------+--------+
   |              Threshold Exceeded Event Name              | Values |
   +---------------------------------------------------------+--------+
   |            Address pool high threshold event            |      1 |
   |             Address pool low threshold event            |      2 |
   |      Address and port mapping high threshold event      |      3 |
   |  Address and port mapping per user high threshold event |      4 |
   |       Global Address mapping high threshold event       |      5 |
   +---------------------------------------------------------+--------+

                      Table 4: Threshold event table

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 IE's in the templates.  Depending on
   the implementation and configuration various IEs that are not
   mandatory can be included or ignored.

4.6.1.  NAT44 create and delete session events

   These events will be generated when a NAT44 session is created or
   deleted.  The template will be the same, the natEvent will indicate
   whether it is a create or a delete event.  The following 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.














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      +----------------------------------+-------------+-----------+
      |            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        |          32 |     No    |
      |       internalAddressRealm       |  OctetArray |     No    |
      |       externalAddressRealm       |  OctetArray |     No    |
      +----------------------------------+-------------+-----------+

               Table 5: NAT44 Session delete/create template

4.6.2.  NAT64 create and delete session events

   These events will be generated when a NAT64 session 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    |
      |        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        |          32 |     No    |
      |       internalAddressRealm       |  OctetArray |     No    |
      |       externalAddressRealm       |  OctetArray |     No    |
      +----------------------------------+-------------+-----------+

            Table 6: NAT64 session create/delete event template



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4.6.3.  NAT44 BIB create and delete events

   These events will be generated when a NAT44 Bind entry is created or
   deleted.  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 |     No    |
         |        natInstanceID        |          32 |     No    |
         |     vlanID/ingressVRFID     |          32 |     No    |
         |     internalAddressRealm    |  OctetArray |     No    |
         |     externalAddressRealm    |  OctetArray |     No    |
         +-----------------------------+-------------+-----------+

              Table 7: NAT44 BIB create/delete event template

4.6.4.  NAT64 BIB create and delete events

   These events will be generated when a NAT64 Bind 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    |
         |      protocolIdentifier     |           8 |     No    |
         |     sourceTransportPort     |          16 |     No    |
         | postNAPTsourceTransportPort |          16 |     No    |
         |        natInstanceID        |          32 |     No    |
         |     vlanID/ingressVRFID     |          32 |     No    |
         |     internalAddressRealm    |  OctetArray |     No    |
         |     externalAddressRealm    |  OctetArray |     No    |
         +-----------------------------+-------------+-----------+

              Table 8: NAT64 BIB create/delete event template






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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  | Size (bits) | Mandatory |
                +---------------+-------------+-----------+
                |   timeStamp   |          64 |    Yes    |
                |    natEvent   |           8 |    Yes    |
                |   natPoolID   |          32 |    Yes    |
                | natInstanceID |          32 |     No    |
                +---------------+-------------+-----------+

                 Table 9: Address Exhausted event template

4.6.6.  Ports Exhausted event

   This event will be generated when a 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    |
          | postNATSourceIPv4Address |          32 |    Yes    |
          |    protocolIdentifier    |           8 |    Yes    |
          |      natInstanceID       |          32 |     No    |
          +--------------------------+-------------+-----------+

                 Table 10: Ports Exhausted event template








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4.6.7.  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.  Maximum session entries exceeded

   The maximum session entries exceeded event is generated when the
   administratively configured NAT session limit is reached.  The
   following is the template of the event.

            +-----------------------+-------------+-----------+
            |       Field Name      | Size (bits) | Mandatory |
            +-----------------------+-------------+-----------+
            |       timeStamp       |          64 |    Yes    |
            |        natEvent       |           8 |    Yes    |
            | natQuotaExceededEvent |          32 |    Yes    |
            |    configuredLimit    |          32 |    Yes    |
            |     natInstanceID     |          32 |     No    |
            +-----------------------+-------------+-----------+

             Table 11: Session Entries Exceeded event template

4.6.7.2.  Maximum BIB entries exceeded

   The maximum BIB entries exceeded event is generated when the
   administratively configured BIB entry limit is reached.  The
   following is the template of the event.

            +-----------------------+-------------+-----------+
            |       Field Name      | Size (bits) | Mandatory |
            +-----------------------+-------------+-----------+
            |       timeStamp       |          64 |    Yes    |
            |        natEvent       |           8 |    Yes    |
            | natQuotaExceededEvent |          32 |    Yes    |
            |    configuredLimit    |          32 |    Yes    |
            |     natInstanceID     |          32 |     No    |
            +-----------------------+-------------+-----------+

               Table 12: BIB Entries Exceeded event template

4.6.7.3.  Maximum entries per user exceeded

   This event is generated when a single user reaches the
   administratively configured NAT translation limit.  The following is
   the template of the event.




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          +-----------------------+-------------+---------------+
          |       Field Name      | Size (bits) |   Mandatory   |
          +-----------------------+-------------+---------------+
          |       timeStamp       |          64 |      Yes      |
          |        natEvent       |           8 |      Yes      |
          | natQuotaExceededEvent |          32 |      Yes      |
          |    configuredLimit    |          32 |      Yes      |
          |   sourceIPv4 address  |          32 | Yes for NAT44 |
          |   sourceIPv6 address  |         128 | Yes for NAT64 |
          |     natInstanceID     |          32 |       No      |
          |  vlanID/ingressVRFID  |          32 |       No      |
          +-----------------------+-------------+---------------+

            Table 13: Per-user Entries Exceeded event template

4.6.7.4.  Maximum active host or subscribers exceeded

   This event is generated when the number of allowed hosts or
   subscribers reaches the administratively configured limit.  The
   following is the template of the event.

            +-----------------------+-------------+-----------+
            |       Field Name      | Size (bits) | Mandatory |
            +-----------------------+-------------+-----------+
            |       timeStamp       |          64 |    Yes    |
            |        natEvent       |           8 |    Yes    |
            | natQuotaExceededEvent |          32 |    Yes    |
            |    configuredLimit    |          32 |    Yes    |
            |     natInstanceID     |          32 |     No    |
            +-----------------------+-------------+-----------+

        Table 14: Maximum hosts/subscribers Exceeded event template

4.6.7.5.  Maximum fragments pending reassembly exceeded

   This event is generated when the number of fragments pending
   reassembly reaches the administratively configured limit.  Note that
   in 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 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.









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         +-----------------------+-------------+----------------+
         |       Field Name      | Size (bits) |   Mandatory    |
         +-----------------------+-------------+----------------+
         |       timeStamp       |          64 |      Yes       |
         |        natEvent       |           8 |      Yes       |
         | natQuotaExceededEvent |          32 |      Yes       |
         |    configuredLimit    |          32 |      Yes       |
         |   sourceIPv4 address  |          32 | Yes for NAT44  |
         |   sourceIPv6 address  |         128 | Yes for NAT64  |
         |     natInstanceID     |          32 |       No       |
         |  vlanID/ingressVRFID  |          32 |       No       |
         |  internalAddressRealm |  OctetArray |       No       |
         +-----------------------+-------------+----------------+

       Table 15: Maximum fragments pending reassembly Exceeded event
                                 template

4.6.8.  Threshold reached events

   This event will be generated when a NAT device reaches a 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 when the high or low threshold is reached for
   the address pool.  The template is the same for both high and low
   threshold events

              +-------------------+-------------+-----------+
              |     Field Name    | Size (bits) | Mandatory |
              +-------------------+-------------+-----------+
              |     timeStamp     |          64 |    Yes    |
              |      natEvent     |           8 |    Yes    |
              | natThresholdEvent |          32 |    Yes    |
              |     natPoolID     |          32 |    Yes    |
              |  configuredLimit  |          32 |    Yes    |
              |   natInstanceID   |          32 |     No    |
              +-------------------+-------------+-----------+

     Table 16: Address pool high/low threshold reached event template

4.6.8.2.  Address and port high threshold reached

   This event is generated when the high threshold is reached for the
   address pool and ports.




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              +-------------------+-------------+-----------+
              |     Field Name    | Size (bits) | Mandatory |
              +-------------------+-------------+-----------+
              |     timeStamp     |          64 |    Yes    |
              |      natEvent     |           8 |    Yes    |
              | natThresholdEvent |          32 |    Yes    |
              |  configuredLimit  |          32 |    Yes    |
              |   natInstanceID   |          32 |     No    |
              +-------------------+-------------+-----------+

       Table 17: Address port high threshold reached event template

4.6.8.3.  Per-user Address and port high threshold reached

   This event is generated when the high threshold is reached for the
   per-user address pool and ports.

           +---------------------+-------------+---------------+
           |      Field Name     | Size (bits) |   Mandatory   |
           +---------------------+-------------+---------------+
           |      timeStamp      |          64 |      Yes      |
           |       natEvent      |           8 |      Yes      |
           |  natThresholdEvent  |          32 |      Yes      |
           |   configuredLimit   |          32 |      Yes      |
           |  sourceIPv4 address |          32 | Yes for NAT44 |
           |  sourceIPv6 address |         128 | Yes for NAT64 |
           |    natInstanceID    |          32 |       No      |
           | vlanID/ingressVRFID |          32 |       No      |
           +---------------------+-------------+---------------+

   Table 18: Per-user Address port high threshold reached event template

4.6.8.4.  Global Address mapping high threshold reached

   This event is generated when the high threshold is reached for the
   per-user address pool and ports.  This is generated only by NAT
   devices that use a paired address pooling behavior.














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             +---------------------+-------------+-----------+
             |      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 when a NAT device binds a local
   address with a global address and when the global address is freed.
   A NAT device will generate the 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      |
     |       sourceIPv4 address       |          32 | Yes for NAT44 |
     |       sourceIPv6 address       |         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, 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 potentially to
   limit the number of connections a subscriber is allowed to use.  In
   the following Port Block allocation template, the portRangeStart and
   portRangeEnd MUST be specified.



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   It is up to the implementation to choose to consolidate log records
   in case two consecutive port ranges for the same user are allocated
   or freed.

     +--------------------------------+-------------+---------------+
     |           Field Name           | Size (bits) |   Mandatory   |
     +--------------------------------+-------------+---------------+
     |           timeStamp            |          64 |      Yes      |
     |            natEvent            |           8 |      Yes      |
     |       sourceIPv4 address       |          32 | Yes for NAT44 |
     |       sourceIPv6 address       |         128 | Yes for NAT64 |
     | Translated Source IPv4 Address |          32 |      Yes      |
     |         portRangeStart         |          16 |      Yes      |
     |          portRangeEnd          |          16 |       No      |
     |         natInstanceID          |          32 |       No      |
     +--------------------------------+-------------+---------------+

            Table 21: NAT Port Block Allocation event template

5.  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 fullfil these requirements is out of
   scope of the present document.  Some management considerations are
   covered in [I-D.ietf-behave-syslog-nat-logging].  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 be able to 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 and
   hence SHOULD be handled by the NAT devices to rate limit them before
   sending them to the collectors.  For eg. 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.








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6.  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.

7.  IANA Considerations

7.1.  Information Elements

   IANA will register the following IEs in the IPFIX Information
   Elements registry at http://www.iana.org/assignments/ipfix/ipfix.xml

7.1.1.  natInstanceID

   Name : natInstanceID

   Description: This Information Element uniquely identifies an Instance
   of the NAT that runs on a NAT middlebox function after the packet
   passed the Observation Point. natInstanceID is defined in RFC 7659
   [RFC7659]

   Abstract Data Type: unsigned32

   Data Type Semantics: identifier

   Reference:

   See RFC 791 [RFC0791] for the definition of the IPv4 source address
   field.  See RFC 3022 [RFC3022] for the definition of NAT.  See RFC
   3234 [RFC3234] for the definition of middleboxes.

7.1.2.  internalAddressRealm

   Name: internalAddressRealm

   Description: This Information Element represents the internal address
   realm where the packet is originated from or destined to.  By
   definition, a NAT mapping can be created from two address realms, one
   from internal and one from external.  Realms are implementation
   dependent and can represent a VRF ID or 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



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   Reference:

   See RFC 791 [RFC0791] for the definition of the IPv4 source address
   field.  See RFC 3022 [RFC3022] for the definition of NAT.  See RFC
   3234 [RFC3234] for the definition of middleboxes.

7.1.3.  externalAddressRealm

   Name: externalAddressRealm

   Description: This Information Element represents the external address
   realm where the packet is originated from or destined to.  The
   detailed definition is in the internal address realm as specified
   above.

   Abstract Data Type: octetArray

   Data Type Semantics: identifier

   Reference:

   See RFC 791 [RFC0791] for the definition of the IPv4 source address
   field.  See RFC 3022 [RFC3022] for the definition of NAT.  See RFC
   3234 [RFC3234] for the definition of middleboxes.

7.1.4.  natQuotaExceededEvent

   Values of this Information Element are defined in a registry
   maintained by IANA at <http://www.iana.org/assignments/ipfix/
   ipfix.xml#TBD-by-IANA>.  New assignments of values will be
   administered by IANA, subject to Expert Review [RFC5226].  Experts
   need to check definitions of new values for completeness, accuracy,
   and redundancy.

   Name : natQuotaExceededEvent

   Description: This Information Element identifies the type of a NAT
   quota exceeded event.  Values for this Information Element are listed
   in the NAT quota exceed event type registry, see
   [http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA] Initial
   values in the registry are defined by the table below.










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            +---------------------------------------+--------+
            |       Quota Exceeded Event Name       | Values |
            +---------------------------------------+--------+
            |        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

   Abstract Data Type: unsigned32

   Data Type Semantics: identifier

   Reference:

   See RFC 791 [RFC0791] for the definition of the IPv4 source address
   field.  See RFC 3022 [RFC3022] for the definition of NAT.  See RFC
   3234 [RFC3234] for the definition of middleboxes.

7.1.5.  natThresholdEvent

   Values of this Information Element are defined in a registry
   maintained by IANA at http://www.iana.org/assignments/ipfix/
   ipfix.xml#TBD-by-IANA.  New assignments of values will be
   administered by IANA, subject to Expert Review [RFC5226].  Experts
   need to check definitions of new values for completeness, accuracy,
   and redundancy.

   Name: natThresholdEvent

   Description: This Information Element identifies a type of a NAT
   threshold event.  Values for this Information Element are listed in
   the NAT threshhold event type registry, see
   <http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA>.
   Initial values in the registry are defined by the table below.













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   +---------------------------------------------------------+--------+
   |              Threshold Exceeded Event Name              | Values |
   +---------------------------------------------------------+--------+
   |            Address pool high threshold event            |      1 |
   |             Address pool low threshold event            |      2 |
   |      Address and port mapping high threshold event      |      3 |
   |  Address and port mapping per user high threshold event |      4 |
   |       Global Address mapping high threshold event       |      5 |
   +---------------------------------------------------------+--------+

                                 Table 23

   Abstract Data Type: unsigned32

   Data Type Semantics: identifier

   Reference:

   See RFC 791 [RFC0791] for the definition of the IPv4 source address
   field.  See RFC 3022 [RFC3022] for the definition of NAT.  See RFC
   3234 [RFC3234] for the definition of middleboxes.

7.1.6.  natEvent

   The original definition of this Information Element specified only
   three values 1, 2, and 3.  This definition is replaced by a registry,
   to which new values can be added.  The semantics of the three
   originally defined values remains unchanged.  IANA maintains the
   registry for values of this Information Element at
   <http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA>.  New
   assignments of values will be administered by IANA, subject to Expert
   Review [RFC5226].  Experts need to check definitions of new values
   for completeness, accuracy, and redundancy.

   Name : natEvent

   Description: Description: This Information Element identifies a NAT
   event.  This IE identifies the type of a NAT event.  Examples of NAT
   events include but not limited to, creation or deletion of a NAT
   translation entry, a threshold reached or exceeded etc.  Values for
   this Information Element are listed in the NAT event type registry,
   see [http://www.iana.org/assignments/ipfix/ipfix.xml#TBD-by-IANA] The
   NAT Event values in the registry are defined by the Table 2 in
   Section 5.3.

   Abstract Data Type: unsigned8

   Data Type Semantics: identifier



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   Element ID : 230

   Reference:

   See RFC 3022 [RFC3022] for the definition of NAT.  See RFC 3234
   [RFC3234] for the definition of middleboxes.  See [thisRFC] for the
   definitions of values 4-16.

8.  Security Considerations

   The security considerations listed in detail for IPFIX in [RFC7011]
   applies to this draft as well.  As described in [RFC7011] the
   messages exchanged between the NAT device and the collector 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 TLS or DTLS for exchanging the
   log messages between the NAT device and the collector.  The log
   events sent in clear text can result in confidential data being
   exposed to attackers, who could then spoof log events based on the
   information in clear text messages.  Hence, the log events SHOULD NOT
   be sent in clear text.

   The logging of NAT events can result in privacy concerns as result of
   exporting information such as source address and port information.
   The logging of destinaion 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.  The collector 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.

9.  References

9.1.  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>.







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   [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>.

   [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>.

   [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>.

   [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>.

   [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>.

   [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>.

   [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>.

9.2.  Informative References

   [I-D.ietf-behave-syslog-nat-logging]
              Chen, Z., Zhou, C., Tsou, T., and T. Taylor, "Syslog
              Format for NAT Logging", draft-ietf-behave-syslog-nat-
              logging-06 (work in progress), January 2014.

   [IPFIX-IANA]
              IANA, "IPFIX Information Elements registry",
              <http://www.iana.org/assignments/ipfix>.





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Internet-Draft          IPFIX IEs for NAT logging           January 2017


   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <http://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>.

   [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>.

   [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. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424,
              DOI 10.17487/RFC5424, March 2009,
              <http://www.rfc-editor.org/info/rfc5424>.

Authors' Addresses

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

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


   Renaldo Penno
   Cisco Systems
   170 W Tasman Drive
   San Jose, California  95035
   USA

   Email: repenno@cisco.com





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