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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft-ietf-opsawg-ipfix-fixes-03" category="std" consensus="true" submissionType="IETF" tocInclude="true" sortRefs="true" symRefs="true" version="3">
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  <front>
    <title abbrev="IPFIX IANA Fixes">Simple Fixes to the IP Flow Information Export (IPFIX) IANA Registry</title>
    <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-ipfix-fixes-03"/>
    <author fullname="Mohamed Boucadair">
      <organization>Orange</organization>
      <address>
        <email>mohamed.boucadair@orange.com</email>
      </address>
    </author>
    <author fullname="Benoit Claise">
      <organization>Huawei</organization>
      <address>
        <email>benoit.claise@huawei.com</email>
      </address>
    </author>
    <date year="2023" month="October" day="17"/>
    <area>Operations and Management</area>
    <workgroup>OPSAWG</workgroup>
    <keyword>IPFIX</keyword>
    <abstract>
      <?line 43?>

<t>This document provides simple fixes to the IANA IP Flow Information Export (IPFIX) registry. Specifically, this document provides updates to fix a shortcoming in the description of some Information Elements (IE), updates to ensure a consistent structure when calling an existing IANA registry, and updates to fix broken pointers, orphan section references, etc. The updates are also meant to bringing some consistency among the entries of the registry.</t>
    </abstract>
    <note removeInRFC="true">
      <name>Discussion Venues</name>
      <t>Discussion of this document takes place on the
    Operations and Management Area Working Group Working Group mailing list (opsawg@ietf.org),
    which is archived at <eref target="https://mailarchive.ietf.org/arch/browse/opsawg/"/>.</t>
      <t>Source for this draft and an issue tracker can be found at
    <eref target="https://github.com/boucadair/simple-ipfix-fixes"/>.</t>
    </note>
  </front>
  <middle>
    <?line 48?>

<section anchor="introduction">
      <name>Introduction</name>
      <t>As the OPSAWG is currently considering <xref target="I-D.ietf-opsawg-rfc7125-update"/> which updates <xref target="RFC7125"/>, the WG realized that some other parts of the IANA IP Flow Information Export (IPFIX) registry <xref target="IANA-IPFIX"/> were not up-to-date. Indeed, since its initial creation in 2007, some IPFIX Information Elements (IEs) are not adequately specified any longer (while they were at some point in time in the past). This document intends to update the IANA registry and bringing some consistency among the entries of the registry.</t>
      <t>As discussed with IANA, the "Additional Information" entry in <xref target="IANA-IPFIX"/> should contain a link to an existing registry, when applicable, as opposed to having:</t>
      <ul spacing="normal">
        <li>
          <t>A link to an exiting registry in the "Description" entry.</t>
        </li>
        <li>
          <t>The registry detailed values repeated in the "Description" entry. This practice has the drawback that the description must be updated each time the registry is updated.</t>
        </li>
      </ul>
      <t>Therefore, this document lists a set of simple fixes to the IPFIX IANA registry <xref target="IANA-IPFIX"/>. These fixes are classified as follows:</t>
      <ul spacing="normal">
        <li>
          <t>Updates that fix a shortcoming in the description of an IE (<xref target="desc"/>).</t>
        </li>
        <li>
          <t>Updates that require adding a pointer to an existing IANA registry (<xref target="to-iana"/>).</t>
        </li>
        <li>
          <t>Updates that are meant to ensure a consistent structure when calling an existing IANA registry (<xref target="consistent"/>).</t>
        </li>
        <li>
          <t>Miscellaneous updates that fix broken pointers, orphan section references, etc. (<xref target="misc"/>).</t>
        </li>
      </ul>
      <t>These updates are also meant to facilitate the automatic extraction of the values maintained in IANA registries (e.g., with a cron job), required by Collectors to be able to support new IPFIX IEs and, more importantly, adequately interpret new values in registries specified by those IPFIX IEs.</t>
      <t>Note that, as per <xref section="5" sectionFormat="of" target="RFC7012"/>, <xref target="IANA-IPFIX"/> is the normative reference for the IPFIX IEs that were defined in <xref target="RFC5102"/>. Therefore, the updates in this document do not update any part of <xref target="RFC7011"/>.</t>
    </section>
    <section anchor="conventions-and-definitions">
      <name>Conventions and Definitions</name>
      <t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as
described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they
appear in all capitals, as shown here.</t>
      <?line -18?>

<t>This document uses the IPFIX-specific terminology (Information Element, Template,
   Collector,  Data Record, Flow Record, Exporting Process,
   Collecting Process, etc.) defined in
   Section 2 of <xref target="RFC7011"/>. As in <xref target="RFC7011"/>, these IPFIX-specific terms
   have the first letter of a word capitalized.</t>
    </section>
    <section anchor="why-an-rfc-is-needed-for-these-updates">
      <name>Why An RFC is Needed for These Updates?</name>
      <t>Many of the edits in this document may be handled by the IPFIX Experts (informally called the IE-DOCTORS <xref target="RFC7013"/>). However, and given that many of the impacted IEs were created via the IETF stream, the following from <xref section="5.1" sectionFormat="of" target="RFC7013"/> should be followed:</t>
      <ul empty="true">
        <li>
          <t>This process should not in any way be construed as allowing the IE-DOCTORS to overrule IETF consensus.  Specifically, Information Elements in the IANA IE registry that were added with IETF consensus require IETF consensus for revision or deprecation.</t>
        </li>
      </ul>
    </section>
    <section anchor="desc">
      <name>Update the Description</name>
      <section anchor="ipv6extensionheaders-information-element">
        <name>ipv6ExtensionHeaders Information Element</name>
        <section anchor="issues">
          <name>Issues</name>
          <t>The current specification of the ipv6ExtensionHeaders Information Element should be updated to:</t>
          <ol spacing="normal" type="1"><li>
              <t>Reflect missing IPv6 EHs, specifically 139, 140, 253, and 254.</t>
            </li>
            <li>
              <t>Specify how to automatically update the registry when a new value is assigned in <xref target="IANA-EH"/>.</t>
            </li>
            <li>
              <t>Update the 108 entry given that 108 does not correspond to an extension header as per <xref target="IANA-Protocols"/>.</t>
            </li>
            <li>
              <t>Specify the procedure to follow when all bits are exhausted.</t>
            </li>
          </ol>
          <t><xref target="sec-up-eh"/> specifies fixes to the first three issues. <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/> specifies a new Information Element to fix the last issue. Other Information Elements are defined in <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/> to address some other limitations such as lack of reporting of extension header chains or aggregate extension headers length.</t>
          <t>Note that some implementations may not be able to export all observed extension headers in a Flow because of a hardware of software limit (see, e.g., <xref target="I-D.ietf-6man-eh-limits"/>. The specification of the ipv6ExtensionHeaders Information Element does not discuss whether it covers all enclosed extension headers or only up to a limit. A solution to this shortcoming is also defined in <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/>.</t>
        </section>
        <section anchor="sec-up-eh">
          <name>Updates to the ipv6ExtensionHeaders Description</name>
          <ul spacing="normal">
            <li>
              <t>OLD:</t>
            </li>
          </ul>
          <artwork><![CDATA[
 Description:
    IPv6 extension headers observed in packets of this Flow.  The
    information is encoded in a set of bit fields.  For each IPv6
    option header, there is a bit in this set.  The bit is set to 1 if
    any observed packet of this Flow contains the corresponding IPv6
    extension header.  Otherwise, if no observed packet of this Flow
    contained the respective IPv6 extension header, the value of the
    corresponding bit is 0.

             0     1     2     3     4     5     6     7
         +-----+-----+-----+-----+-----+-----+-----+-----+
         | DST | HOP | Res | UNK |FRA0 | RH  |FRA1 | Res |  ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

             8     9    10    11    12    13    14    15
         +-----+-----+-----+-----+-----+-----+-----+-----+
     ... |           Reserved    | MOB | ESP | AH  | PAY | ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

            16    17    18    19    20    21    22    23
         +-----+-----+-----+-----+-----+-----+-----+-----+
     ... |                  Reserved                     | ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

            24    25    26    27    28    29    30    31
         +-----+-----+-----+-----+-----+-----+-----+-----+
     ... |                  Reserved                     |
         +-----+-----+-----+-----+-----+-----+-----+-----+

     Bit    IPv6 Option   Description

     0, DST      60       Destination option header
     1, HOP       0       Hop-by-hop option header
     2, Res               Reserved
     3, UNK               Unknown Layer 4 header
                          (compressed, encrypted, not supported)
     4, FRA0     44       Fragment header - first fragment
     5, RH       43       Routing header
     6, FRA1     44       Fragmentation header - not first fragment
     7, Res               Reserved
     8 to 11              Reserved
     12, MOB     135      IPv6 mobility [RFC3775]
     13, ESP      50      Encrypted security payload
     14, AH       51      Authentication Header
     15, PAY     108      Payload compression header
     16 to 31             Reserved

 Abstract Data Type: unsigned32

 Data Type Semantics: flags

 ElementId: 64

 Status: current

 Reference: [RFC5102]

 Additional Information:
    See [RFC8200] for the general definition of IPv6 extension headers
    and for the specification of the hop-by-hop options header, the
    routing header, the fragment header, and the destination options
    header. See [RFC4302] for the specification of the authentication
    header. See [RFC4303] for the specification of the encapsulating
    security payload. The diagram provided in [RFC5102] is incorrect.
    The diagram in this registry is taken from Errata 1738.
    See [RFC Errata 1738].
]]></artwork>
          <ul spacing="normal">
            <li>
              <t>NEW:</t>
            </li>
          </ul>
          <dl>
            <dt>Description:</dt>
            <dd>
              <t>IPv6 extension headers observed in packets of this Flow. The
  information is encoded in a set of bit fields.  For each IPv6
  option header, there is a bit in this set.  The bit is set to 1 if
  any observed packet of this Flow contains the corresponding IPv6
  extension header.  Otherwise, if no observed packet of this Flow
  contained the respective IPv6 extension header, the value of the
  corresponding bit is 0. The IPv6 extension header associated with each bit
  is provided in  [NEW_IPFIX_IPv6EH_SUBREGISTRY]. The following drawing indicates
  the position of each bit in the encoding of the Information Element.</t>
            </dd>
            <dt/>
            <dd>
              <t>This IE is used only when the observed extension headers are in the 0-31
  range.</t>
            </dd>
            <dt/>
            <dd>
              <t>If the observed EHs exceeds that range,
  ipv6ExtensionHeadersFull Information Element <bcp14>MUST</bcp14> be used
  <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/>.</t>
            </dd>
          </dl>
          <artwork><![CDATA[
             0     1     2     3     4     5     6     7
         +-----+-----+-----+-----+-----+-----+-----+-----+
         |        IPv6 extension header bits            |  ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

             8     9    10    11    12    13    14    15
         +-----+-----+-----+-----+-----+-----+-----+-----+
         |         IPv6 extension header bits            |  ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

            16    17    18    19    20    21    22    23
         +-----+-----+-----+-----+-----+-----+-----+-----+
         |         IPv6 extension header bits            |  ...
         +-----+-----+-----+-----+-----+-----+-----+-----+

            24    25    26    27    28    29    30    31
         +-----+-----+-----+-----+-----+-----+-----+-----+
     ... |        IPv6 extension header bits             |
         +-----+-----+-----+-----+-----+-----+-----+-----+
]]></artwork>
          <dl>
            <dt>Abstract Data Type:</dt>
            <dd>
              <t>unsigned32</t>
            </dd>
            <dt>Data Type Semantics:</dt>
            <dd>
              <t>flags</t>
            </dd>
            <dt>ElementId:</dt>
            <dd>
              <t>64</t>
            </dd>
            <dt>Status:</dt>
            <dd>
              <t>current</t>
            </dd>
            <dt>Reference:</dt>
            <dd>
              <t><xref target="RFC5102"/>This-Document</t>
            </dd>
            <dt>Additional Information:</dt>
            <dd>
              <t>See the assigned bits to each IPv6 extension header in [NEW_IPFIX_IPv6EH_SUBREGISTRY].</t>
            </dd>
            <dt/>
            <dd>
              <t>See <xref target="RFC8200"/> for the general definition of IPv6 extension headers and <xref target="IANA-EH"/> for assigned extension headers.</t>
            </dd>
          </dl>
        </section>
      </section>
      <section anchor="tcpoptions">
        <name>tcpOptions</name>
        <section anchor="issues-1">
          <name>Issues</name>
          <t>Only options having a kind =&lt; 63 can be included in a tcpOptions IE. An update is thus required to specify how any observed TCP option in a packet can be exported using IPFIX. Also, there is no way to report the observed Experimental Identifiers (ExIDs) that are carried in shared TCP options (kind=253 or 254) <xref target="RFC6994"/>.</t>
          <t>The following section updates the description of the tcpOptions IE to explicitly indicate the applicable kind range and to point to the new IEs defined in <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/>.</t>
        </section>
        <section anchor="update-the-description-of-the-tcpoptions-ie">
          <name>Update the Description of the tcpOptions IE</name>
          <t>This document requests IANA to update the description of the tcpOptions IE in the IANA IPFIX registry <xref target="IANA-IPFIX"/> as follows:</t>
          <ul spacing="normal">
            <li>
              <dl>
                <dt>OLD Description:</dt>
                <dd>
                  <t>TCP options in packets of this Flow.  The information is encoded
  in a set of bit fields.  For each TCP option, there is a bit in
  this set.  The bit is set to 1 if any observed packet of this Flow
  contains the corresponding TCP option.  Otherwise, if no observed
  packet of this Flow contained the respective TCP option, the value
  of the corresponding bit is 0.
  Options are mapped to bits according to their option numbers.
  Option number X is mapped to bit X.  TCP option numbers are
  maintained by IANA.</t>
                </dd>
              </dl>
            </li>
          </ul>
          <artwork><![CDATA[
            0     1     2     3     4     5     6     7
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   7 |   6 |   5 |   4 |   3 |   2 |   1 |   0 |  ...
        +-----+-----+-----+-----+-----+-----+-----+-----+

            8     9    10    11    12    13    14    15
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  15 |  14 |  13 |  12 |  11 |  10 |   9 |   8 |...
        +-----+-----+-----+-----+-----+-----+-----+-----+

           16    17    18    19    20    21    22    23
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  23 |  22 |  21 |  20 |  19 |  18 |  17 |  16 |...
        +-----+-----+-----+-----+-----+-----+-----+-----+

                              . . .

           56    57    58    59    60    61    62    63
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  63 |  62 |  61 |  60 |  59 |  58 |  57 |  56 |
        +-----+-----+-----+-----+-----+-----+-----+-----+
]]></artwork>
          <ul spacing="normal">
            <li>
              <dl>
                <dt>NEW Description:</dt>
                <dd>
                  <t>TCP options in packets of this Flow.  The information is encoded
  in a set of bit fields.  For each TCP option, there is a bit in
  this set.  The bit is set to 1 if any observed packet of this Flow
  contains the corresponding TCP option.  Otherwise, if no observed
  packet of this Flow contained the respective TCP option, the value
  of the corresponding bit is 0.
  Options are mapped to bits according to the drawing below.  TCP option numbers are
  maintained by IANA. This information element is used only
  when the observed kinds are within the 0-63 range. If not, the tcpOptionsFull IE <xref target="I-D.ietf-opsawg-ipfix-tcpo-v6eh"/> <bcp14>MUST</bcp14> be used.</t>
                </dd>
              </dl>
            </li>
          </ul>
          <artwork><![CDATA[
            0     1     2     3     4     5     6     7
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   7 |   6 |   5 |   4 |   3 |   2 |   1 |   0 |  ...
        +-----+-----+-----+-----+-----+-----+-----+-----+

            8     9    10    11    12    13    14    15
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  15 |  14 |  13 |  12 |  11 |  10 |   9 |   8 |...
        +-----+-----+-----+-----+-----+-----+-----+-----+

           16    17    18    19    20    21    22    23
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  23 |  22 |  21 |  20 |  19 |  18 |  17 |  16 |...
        +-----+-----+-----+-----+-----+-----+-----+-----+

                              . . .

           56    57    58    59    60    61    62    63
        +-----+-----+-----+-----+-----+-----+-----+-----+
    ... |  63 |  62 |  61 |  60 |  59 |  58 |  57 |  56 |
        +-----+-----+-----+-----+-----+-----+-----+-----+
]]></artwork>
        </section>
      </section>
      <section anchor="forwardingstatus">
        <name>forwardingStatus</name>
        <t>The current forwardingStatus entry in <xref target="IANA-IPFIX"/> deviates from what is provided in <xref target="RFC7270"/>. In particular, the registered Abstract Data Type is unsigned8, while it must be unsigned32. The following update fixes that issue. The description is also updated to clarify the use of the reduced-size encoding as per <xref section="6.2" sectionFormat="of" target="RFC7011"/>.</t>
        <ul spacing="normal">
          <li>
            <t>OLD:</t>
          </li>
        </ul>
        <artwork><![CDATA[
   - Description:  This Information Element describes the forwarding
                   status of the flow and any attached reasons.

                   The layout of the encoding is as follows:

                   MSB  -  0   1   2   3   4   5   6   7  -  LSB
                         +---+---+---+---+---+---+---+---+
                         | Status|  Reason code or flags |
                         +---+---+---+---+---+---+---+---+

                   See the Forwarding Status sub-registries at
                   https://www.iana.org/assignments/ipfix/ipfix.xhtml#forwarding-status.

                   Examples:

                   value : 0x40 = 64
                   binary: 01000000
                   decode: 01        -> Forward
                             000000  -> No further information

                   value : 0x89 = 137
                   binary: 10001001
                   decode: 10        -> Drop
                             001001  -> Bad TTL

   - Additional Information: See "NetFlow Version 9 Flow-Record Format"
             [CCO-NF9FMT].

   - Abstract Data Type: unsigned8
]]></artwork>
        <ul spacing="normal">
          <li>
            <t>NEW:</t>
          </li>
        </ul>
        <artwork><![CDATA[
   - Description:  This Information Element describes the forwarding
                   status of the flow and any attached reasons.
                   IPFIX reduced-size encoding is used as required.

                   A structure is currently associated with the first
                   byte. Future versions may be defined to associate
                   meanings with the remaining bits.

                   The current version of the Information Element
                   should be exported as unsigned8.

                   The layout of the encoding is as follows:

                   MSB  -  0   1   2   3   4   5   6   7  -  LSB
                         +---+---+---+---+---+---+---+---+
                         | Status|  Reason code or flags |
                         +---+---+---+---+---+---+---+---+

                   Examples:

                   value : 0x40 = 64
                   binary: 01000000
                   decode: 01        -> Forward
                             000000  -> No further information

                   value : 0x89 = 137
                   binary: 10001001
                   decode: 10        -> Drop
                             001001  -> Bad TTL

   - Additional Information: See the Forwarding Status sub-registries
       at https://www.iana.org/assignments/ipfix/ipfix.xhtml#forwarding-status.

   - Abstract Data Type: unsigned32
]]></artwork>
      </section>
    </section>
    <section anchor="to-iana">
      <name>Point to An Existing IANA Registry</name>
      <t>This document requests IANA to update the following entries by adding the indicated "Additional Information" to the <xref target="IANA-IPFIX"/> registry:</t>
      <table>
        <name>Cite an IANA Registry under Additional Information</name>
        <thead>
          <tr>
            <th align="left">IE</th>
            <th align="left">Additional Information</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td align="left">icmpTypeCodeIPv4</td>
            <td align="left">https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml</td>
          </tr>
          <tr>
            <td align="left">igmpType</td>
            <td align="left">https://www.iana.org/assignments/igmp-type-numbers/igmp-type-numbers.xhtml#igmp-type-numbers-1</td>
          </tr>
          <tr>
            <td align="left">icmpTypeCodeIPv6</td>
            <td align="left">https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml</td>
          </tr>
          <tr>
            <td align="left">icmpTypeIPv4</td>
            <td align="left">https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-types</td>
          </tr>
          <tr>
            <td align="left">icmpCodeIPv4</td>
            <td align="left">https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-codes</td>
          </tr>
          <tr>
            <td align="left">icmpTypeIPv6</td>
            <td align="left">https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml#icmpv6-parameters-2</td>
          </tr>
          <tr>
            <td align="left">icmpCodeIPv6</td>
            <td align="left">https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml#icmpv6-parameters-3</td>
          </tr>
          <tr>
            <td align="left">privateEnterpriseNumber</td>
            <td align="left">https://www.iana.org/assignments/enterprise-numbers/enterprise-numbers</td>
          </tr>
        </tbody>
      </table>
    </section>
    <section anchor="consistent">
      <name>Consistent Citation of IANA Registries</name>
      <t>This document requests IANA to update <xref target="IANA-IPFIX"/> for each of the IE entries listed in the following subsections.</t>
      <section anchor="mplstoplabeltype">
        <name>mplsTopLabelType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This field identifies the control protocol that allocated the top-of-stack label. Values for this field are listed in the MPLS label type registry.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-mpls-label-type.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC3031"/> for the MPLS label structure.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See the list of MPLS label types assigned by IANA at [https://www.iana.org/assignments/mpls-label-values].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This field identifies the control protocol that allocated the top-of-stack label. Values for this field are listed in the MPLS label type registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the list of MPLS label types assigned by IANA at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-mpls-label-type].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3031"/> for the MPLS label structure.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="classificationengineid">
        <name>classificationEngineId</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A unique identifier for the engine that determined the Selector ID. Thus, the Classification Engine ID defines the context for the Selector ID. The Classification Engine can be considered a specific registry for application assignments.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values for this field are listed in the Classification Engine IDs registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#classification-engine-ids.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A unique identifier for the engine that determined the Selector ID. Thus, the Classification Engine ID defines the context for the Selector ID. The Classification Engine can be considered a specific registry for application assignments.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values for this field are listed in the Classification Engine IDs registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See https://www.iana.org/assignments/ipfix/ipfix.xhtml#classification-engine-ids.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="flowendreason">
        <name>flowEndReason</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The reason for Flow termination. Values are listed in the flowEndReason registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-flow-end-reason.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The reason for Flow termination. Values are listed in the flowEndReason registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the Classification Engine IDs registry available at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-flow-end-reason].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="natoriginatingaddressrealm">
        <name>natOriginatingAddressRealm</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates whether the session was created because traffic originated in the private or public address realm. postNATSourceIPv4Address, postNATDestinationIPv4Address, postNAPTSourceTransportPort, and postNAPTDestinationTransportPort are qualified with the address realm in perspective.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values are listed in the natOriginatingAddressRealm registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-originating-address-realm.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates whether the session was created because traffic originated in the private or public address realm. postNATSourceIPv4Address, postNATDestinationIPv4Address, postNAPTSourceTransportPort, and postNAPTDestinationTransportPort are qualified with the address realm in perspective.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values are listed in the natOriginatingAddressRealm registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned NAT originating address realm at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-originating-address-realm]. See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="natevent">
        <name>natEvent</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies a NAT event. This IE identifies the type of a NAT event. 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 the "NAT Event Type" registry, see https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-event-type.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC8158"/> for the definitions of values 4-16.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies a NAT event. This IE identifies the type of a NAT event. 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 the "NAT Event Type" registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned NAT Event Types at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-event-type].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC8158"/> for the definitions of values 4-16.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="firewallevent">
        <name>firewallEvent</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates a firewall event. Allowed values are listed in the firewallEvent registry.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-firewall-event.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates a firewall event. Allowed values are listed in the firewallEvent registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned firewall events at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-firewall-event].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="biflowdirection">
        <name>biflowDirection</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the direction assignment method used to assign the Biflow Source and Destination. This Information Element <bcp14>MAY</bcp14> be present in a Flow Data Record, or applied to all flows exported from an Exporting Process or Observation Domain using IPFIX Options. If this Information Element is not present in a Flow Record or associated with a Biflow via scope, it is assumed that the configuration of the direction assignment method is done out-of-band. Note that when using IPFIX Options to apply this Information Element to all flows within an Observation Domain or from an Exporting Process, the Option <bcp14>SHOULD</bcp14> be sent reliably. If reliable transport is not available (i.e., when using UDP), this Information Element <bcp14>SHOULD</bcp14> appear in each Flow Record. Values are listed in the biflowDirection registry. See [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-biflow-direction].</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the direction assignment method used to assign the Biflow Source and Destination. This Information Element <bcp14>MAY</bcp14> be present in a Flow Data Record, or applied to all flows exported from an Exporting Process or Observation Domain using IPFIX Options. If this Information Element is not present in a Flow Record or associated with a Biflow via scope, it is assumed that the configuration of the direction assignment method is done out-of-band. Note that when using IPFIX Options to apply this Information Element to all flows within an Observation Domain or from an Exporting Process, the Option <bcp14>SHOULD</bcp14> be sent reliably. If reliable transport is not available (i.e., when using UDP), this Information Element <bcp14>SHOULD</bcp14> appear in each Flow Record. Values are listed in the biflowDirection registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned biflow direction values at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-biflow-direction].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="observationpointtype">
        <name>observationPointType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Type of observation point. Values are listed in the observationPointType registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-observation-point-type.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Type of observation point. Values are listed in the observationPointType registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned observation point type at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-observation-point-type].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="anonymizationtechnique">
        <name>anonymizationTechnique</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the anonymization technique applied to a referenced Information Element within a referenced Template. Each technique may be applicable only to certain Information Elements and recommended only for certain Information Elements. Values are listed in the anonymizationTechnique registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-anonymization-technique.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the anonymization technique applied to a referenced Information Element within a referenced Template. Each technique may be applicable only to certain Information Elements and recommended only for certain Information Elements. Values are listed in the anonymizationTechnique registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned anonymization techniques at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-anonymization-technique].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="nattype">
        <name>natType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Values are listed in the natType registry.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-type.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC1631"/> for the definition of NAT44.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6144"/> for the definition of NAT64.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6146"/> for the definition of NAT46.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6296"/> for the definition of NAT66.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of IPv4.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC8200"/> for the definition of IPv6.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Values are listed in the natType registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned NAT types at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-type].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC1631"/> for the definition of NAT44.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6144"/> for the definition of NAT46.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6146"/> for the definition of NAT64.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC6296"/> for the definition of NPTv6.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of IPv4.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC8200"/> for the definition of IPv6.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
        <ul empty="true">
          <li>
            <t>Note: This change also corrects errors in the pointers provided NAT46/NAT64.</t>
          </li>
        </ul>
      </section>
      <section anchor="selectoralgorithm">
        <name>selectorAlgorithm</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the packet selection methods (e.g., Filtering, Sampling) that are applied by the Selection Process. Most of these methods have parameters. Further Information Elements are needed to fully specify packet selection with these methods and all their parameters. The methods listed below are defined in <xref target="RFC5475"/>. For their parameters, Information Elements are defined in the information model document. The names of these Information Elements are listed for each method identifier. Further method identifiers may be added to the list below. It might be necessary to define new Information Elements to specify their parameters.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>The following packet selection methods identifiers are defined here: https://www.iana.org/assignments/psamp-parameters.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>There is a broad variety of possible parameters that could be used for Property match Filtering (5) but currently there are no agreed parameters specified.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the packet selection methods (e.g., Filtering, Sampling) that are applied by the Selection Process. Most of these methods have parameters. Further Information Elements are needed to fully specify packet selection with these methods and all their parameters. For the methods parameters, Information Elements are defined in the information model document. The names of these Information Elements are listed for each method identifier. Further method identifiers may be added to the list. It might be necessary to define new Information Elements to specify their parameters.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>There is a broad variety of possible parameters that could be used for Property match Filtering (5) but currently there are no agreed parameters specified.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned PSAMP parameters at [https://www.iana.org/assignments/psamp-parameters].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="informationelementdatatype">
        <name>informationElementDataType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the abstract data type of an IPFIX information element.These are taken from the abstract data types defined in section 3.1 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types described in the [informationElementDataType] subregistry. These types are registered in the IANA IPFIX Information Element Data Type subregistry. This subregistry is intended to assign numbers for type names, not to provide a mechanism for adding data types to the IPFIX Protocol, and as such requires a Standards Action <xref target="RFC8126"/> to modify.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the abstract data type of an IPFIX information element.These are taken from the abstract data types defined in Section 3.1 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types described in the [informationElementDataType] subregistry. These types are registered in the IANA IPFIX Information Element Data Type subregistry.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>The [informationElementDataType] subregistry is intended to assign numbers for type names, not to provide a mechanism for adding data types to the IPFIX Protocol, and as such requires a Standards Action <xref target="RFC8126"/> to modify.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned emelement data types at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-information-element-data-types].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="informationelementsemantics">
        <name>informationElementSemantics</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the semantics of an IPFIX Information Element. These are taken from the data type semantics defined in section 3.2 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types defined in the [IPFIX Information Element Semantics] subregistry. This field may take the values in the semantics registry; the special value 0x00 (default) is used to note that no semantics apply to the field; it cannot be manipulated by a Collecting Process or File Reader that does not understand it a priori. These semantics are registered in the IANA IPFIX Information Element Semantics subregistry. This subregistry is intended to assign numbers for semantics names, not to provide a mechanism for adding semantics to the IPFIX Protocol, and as such requires a Standards Action <xref target="RFC8126"/> to modify.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the semantics of an IPFIX Information Element. These are taken from the data type semantics defined in Section 3.2 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types defined in the [IPFIX Information Element Semantics] subregistry. This field may take the values in the [IPFIX Information Element Semantics] subregistry; the special value 0x00 (default) is used to note that no semantics apply to the field; it cannot be manipulated by a Collecting Process or File Reader that does not understand it a priori.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>The [IPFIX Information Element Semantics] subregistry is intended to assign numbers for semantics names, not to provide a mechanism for adding semantics to the IPFIX Protocol, and as such requires a Standards Action <xref target="RFC8126"/> to modify.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned semantics of an IPFIX Information Element at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-information-element-semantic].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="informationelementunits">
        <name>informationElementUnits</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the units of an IPFIX Information Element. These correspond to the units implicitly defined in the Information Element definitions in section 5 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types described in the informationElementsUnits subregistry. This field may take the values in Table 3 below; the special value 0x00 (none) is used to note that the field is unitless. These types are registered in the [IANA IPFIX Information Element Units] subregistry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the units of an IPFIX Information Element. These correspond to the units implicitly defined in the Information Element definitions in Section 5 of the IPFIX Information Model <xref target="RFC5102"/>; see that section for more information on the types described in the informationElementsUnits subregistry. These types can take the values in the [IANA IPFIX Information Element Units] subregistry. The special value 0x00 (none) is used to note that the field is unitless.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information: See the assigned units of an IPFIX Information Element at [IANA IPFIX Information Element Units].</t>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="portrangestart">
        <name>portRangeStart</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The port number identifying the start of a range of ports. A value of zero indicates that the range start is not specified, ie the range is defined in some other way.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Additional information on defined TCP port numbers can be found at https://www.iana.org/assignments/service-names-port-numbers.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The port number identifying the start of a range of ports. A value of zero indicates that the range start is not specified, i.e., the range is defined in some other way.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>Additional information on defined TCP port numbers can be found at https://www.iana.org/assignments/service-names-port-numbers.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="portrangeend">
        <name>portRangeEnd</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The port number identifying the end of a range of ports. A value of zero indicates that the range end is not specified, ie the range is defined in some other way. Additional information on defined TCP port numbers can be found at https://www.iana.org/assignments/service-names-port-numbers.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The port number identifying the end of a range of ports. A value of zero indicates that the range end is not specified, i.e., the range is defined in some other way.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>Additional information on defined TCP port numbers can be found at https://www.iana.org/assignments/service-names-port-numbers.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="ingressinterfacetype">
        <name>ingressInterfaceType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The type of interface where packets of this Flow are being received. The value matches the value of managed object 'ifType' as defined in https://www.iana.org/assignments/ianaiftype-mib.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>https://www.iana.org/assignments/ianaiftype-mib</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The type of interface where packets of this Flow are being received. The value matches the value of managed object 'ifType'.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned ingress interface types at [https://www.iana.org/assignments/ianaiftype-mib].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="egressinterfacetype">
        <name>egressInterfaceType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The type of interface where packets of this Flow are being sent. The value matches the value of managed object 'ifType' as defined in https://www.iana.org/assignments/ianaiftype-mib.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>https://www.iana.org/assignments/ianaiftype-mib</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The type of interface where packets of this Flow are being sent. The value matches the value of managed object 'ifType'.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned egress interface types at [https://www.iana.org/assignments/ianaiftype-mib].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="valuedistributionmethod">
        <name>valueDistributionMethod</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the method used to distribute the counters from Contributing Flows into the Aggregated Flow records described by an associated scope, generally a Template. The method is deemed to apply to all the non-key Information Elements in the referenced scope for which value distribution is a valid operation; if the originalFlowsInitiated and/or originalFlowsCompleted Information Elements appear in the Template, they are not subject to this distribution method, as they each infer their own distribution method. The valueDistributionMethod registry is intended to list a complete set of possible value distribution methods.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-value-distribution-method.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A description of the method used to distribute the counters from Contributing Flows into the Aggregated Flow records described by an associated scope, generally a Template. The method is deemed to apply to all the non-key Information Elements in the referenced scope for which value distribution is a valid operation; if the originalFlowsInitiated and/or originalFlowsCompleted Information Elements appear in the Template, they are not subject to this distribution method, as they each infer their own distribution method. The valueDistributionMethod registry is intended to list a complete set of possible value distribution methods.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned distributed methods at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-value-distribution-method].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="flowselectoralgorithm">
        <name>flowSelectorAlgorithm</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the Intermediate Flow Selection Process technique (e.g., Filtering, Sampling) that is applied by the Intermediate Flow Selection Process. Most of these techniques have parameters. Its configuration parameter(s) <bcp14>MUST</bcp14> be clearly specified. Further Information Elements are needed to fully specify packet selection with these methods and all their parameters. Further method identifiers may be added to the flowSelectorAlgorithm registry. It might be necessary to define new Information Elements to specify their parameters.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Please note that the purpose of the flow selection techniques described in this document is the improvement of measurement functions as defined in the Scope (Section 1).</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>The Intermediate Flow Selection Process Techniques identifiers are defined at https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-flowselectoralgorithm.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the Intermediate Flow Selection Process technique (e.g., Filtering, Sampling) that is applied by the Intermediate Flow Selection Process. Most of these techniques have parameters. Its configuration parameter(s) <bcp14>MUST</bcp14> be clearly specified. Further Information Elements are needed to fully specify packet selection with these methods and all their parameters. Further method identifiers may be added to the flowSelectorAlgorithm registry. It might be necessary to define new Information Elements to specify their parameters.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned flow selector algorithms at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-flowselectoralgorithm].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="datalinkframetype">
        <name>dataLinkFrameType</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element specifies the type of the selected data link frame. Data link types are defined in the dataLinkFrameType registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-data-link-frame-type.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Further values may be assigned by IANA. Note that the assigned values are bits so that multiple observations can be OR'd together. The data link layer is defined in [ISO/IEC.7498-1:1994].</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>[IEEE802.3][IEEE802.11][ISO/IEC.7498-1:1994]</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element specifies the type of the selected data link frame. Data link types are defined in the dataLinkFrameType registry.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Further values may be assigned by IANA. Note that the assigned values are bits so that multiple observations can be OR'd together.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned data link frame types at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-data-link-frame-type].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>More information about the data link layer can be found in [IEEE802.3][IEEE802.11][ISO/IEC.7498-1:1994].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="mibcapturetimesemantics">
        <name>mibCaptureTimeSemantics</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates when in the lifetime of the Flow the MIB value was retrieved from the MIB for a mibObjectIdentifier. This is used to indicate if the value exported was collected from the MIB closer to Flow creation or Flow export time and refers to the Timestamp fields included in the same Data Record.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>This field <bcp14>SHOULD</bcp14> be used when exporting a mibObjectValue that specifies counters or statistics. If the MIB value was sampled by SNMP prior to the IPFIX Metering Process or Exporting Process retrieving the value (i.e., the data is already stale) and it is important to know the exact sampling time, then an additional observationTime* element should be paired with the OID using IPFIX Structured Data <xref target="RFC6313"/>. Similarly, if different MIB capture times apply to different mibObjectValue elements within the Data Record, then individual mibCaptureTimeSemantics Information Elements should be paired with each OID using IPFIX Structured Data.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values are listed in the mibCaptureTimeSemantics registry. See https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-mib-capture-time-semantics.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <t>Additional Information:</t>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>Indicates when in the lifetime of the Flow the MIB value was retrieved from the MIB for a mibObjectIdentifier. This is used to indicate if the value exported was collected from the MIB closer to Flow creation or Flow export time and refers to the Timestamp fields included in the same Data Record.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>This field <bcp14>SHOULD</bcp14> be used when exporting a mibObjectValue that specifies counters or statistics. If the MIB value was sampled by SNMP prior to the IPFIX Metering Process or Exporting Process retrieving the value (i.e., the data is already stale) and it is important to know the exact sampling time, then an additional observationTime* element should be paired with the OID using IPFIX Structured Data <xref target="RFC6313"/>. Similarly, if different MIB capture times apply to different mibObjectValue elements within the Data Record, then individual mibCaptureTimeSemantics Information Elements should be paired with each OID using IPFIX Structured Data.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>Values are listed in the mibCaptureTimeSemantics registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned values for the MIB capture time semantics at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-mib-capture-time-semantics].</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="natquotaexceededevent">
        <name>natQuotaExceededEvent</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the type of a NAT Quota Exceeded event. Values for this Information Element are listed in the "NAT Quota Exceeded Event Type" registry, see https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-quota-exceeded-event.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of the IPv4 source address field.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element identifies the type of a NAT Quota Exceeded event. Values for this Information Element are listed in the "NAT Quota Exceeded Event Type" registry.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned events for exceeded NAT quota at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-quota-exceeded-event].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of the IPv4 source address field.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="natthresholdevent">
        <name>natThresholdEvent</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>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 https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-threshold-event.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of the IPv4 source address field.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>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.</t>
                  </dd>
                </dl>
              </li>
              <li>
                <dl>
                  <dt>Additional Information:</dt>
                  <dd>
                    <t>See the assigned values for the NAT Threshold events at [https://www.iana.org/assignments/ipfix/ipfix.xhtml#ipfix-nat-threshold-event].</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC0791"/> for the definition of the IPv4 source address field.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3022"/> for the definition of NAT.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See <xref target="RFC3234"/> for the definition of middleboxes.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
    </section>
    <section anchor="misc">
      <name>Misc</name>
      <t>This document requests IANA to update the description of the following entries in <xref target="IANA-IPFIX"/>.</t>
      <section anchor="collectiontimemilliseconds">
        <name>collectionTimeMilliseconds</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The absolute timestamp at which the data within the scope containing this Information Element was received by a Collecting Process. This Information Element <bcp14>SHOULD</bcp14> be bound to its containing IPFIX Message via IPFIX Options and the messageScope Information Element, as defined below.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The absolute timestamp at which the data within the scope containing this Information Element was received by a Collecting Process. This Information Element <bcp14>SHOULD</bcp14> be bound to its containing IPFIX Message via IPFIX Options and the messageScope Information Element.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="messagemd5checksum">
        <name>messageMD5Checksum</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The MD5 checksum of the IPFIX Message containing this record. This Information Element <bcp14>SHOULD</bcp14> be bound to its containing IPFIX Message via an options record and the messageScope Information Element, as defined below, and <bcp14>SHOULD</bcp14> appear only once in a given IPFIX Message. To calculate the value of this Information Element, first buffer the containing IPFIX Message, setting the value of this Information Element to all zeroes. Then calculate the MD5 checksum of the resulting buffer as defined in <xref target="RFC1321"/>, place the resulting value in this Information Element, and export the buffered message.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>This Information Element is intended as a simple checksum only; therefore collision resistance and algorithm agility are not required, and MD5 is an appropriate message digest. This Information Element has a fixed length of 16 octets.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The MD5 checksum of the IPFIX Message containing this record. This Information Element <bcp14>SHOULD</bcp14> be bound to its containing IPFIX Message via an options record and the messageScope Information Element, and <bcp14>SHOULD</bcp14> appear only once in a given IPFIX Message. To calculate the value of this Information Element, first buffer the containing IPFIX Message, setting the value of this Information Element to all zeroes. Then calculate the MD5 checksum of the resulting buffer as defined in <xref target="RFC1321"/>, place the resulting value in this Information Element, and export the buffered message.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>This Information Element is intended as a simple checksum only; therefore collision resistance and algorithm agility are not required, and MD5 is an appropriate message digest. This Information Element has a fixed length of 16 octets.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="anonymizationflags">
        <name>anonymizationFlags</name>
        <ul spacing="normal">
          <li>
            <t>OLD:</t>
          </li>
        </ul>
        <artwork><![CDATA[
+--------+----------+-----------------------------------------------+
| bit(s) | name     | description                                   |
| (LSB = |          |                                               |
| 0)     |          |                                               |
+--------+----------+-----------------------------------------------+
| 0-1    | SC       | Stability Class: see the Stability Class      |
|        |          | table below, and section Section 5.1.         |
| 2      | PmA      | Perimeter Anonymization: when set (1),        |
|        |          | source- Information Elements as described in  |
|        |          | [RFC5103] are interpreted as external         |
|        |          | addresses, and destination- Information       |
|        |          | Elements as described in [RFC5103] are        |
|        |          | interpreted as internal addresses, for the    |
|        |          | purposes of associating                       |
|        |          | anonymizationTechnique to Information         |
|        |          | Elements only; see Section 7.2.2 for details. |
|        |          | This bit MUST NOT be set when associated with |
|        |          | a non-endpoint (i.e., source- or              |
|        |          | destination-) Information Element.  SHOULD be |
|        |          | consistent within a record (i.e., if a        |
|        |          | source- Information Element has this flag     |
|        |          | set, the corresponding destination- element   |
|        |          | SHOULD have this flag set, and vice-versa.)   |
+--------+----------+-----------------------------------------------+
]]></artwork>
        <ul spacing="normal">
          <li>
            <t>NEW:</t>
          </li>
        </ul>
        <artwork><![CDATA[
+--------+----------+-----------------------------------------------+
| bit(s) | name     | description                                   |
| (LSB = |          |                                               |
| 0)     |          |                                               |
+--------+----------+-----------------------------------------------+
| 0-1    | SC       | Stability Class: see the Stability Class      |
|        |          | table below, and Section 5.1 of [RFC6235].    |
| 2      | PmA      | Perimeter Anonymization: when set (1),        |
|        |          | source- Information Elements as described in  |
|        |          | [RFC5103] are interpreted as external         |
|        |          | addresses, and destination- Information       |
|        |          | Elements as described in [RFC5103] are        |
|        |          | interpreted as internal addresses, for the    |
|        |          | purposes of associating                       |
|        |          | anonymizationTechnique to Information         |
|        |          | Elements only; see Section 7.2.2 of [RFC6235] |
|        |          | for details.                                  |
|        |          | This bit MUST NOT be set when associated with |
|        |          | a non-endpoint (i.e., source- or              |
|        |          | destination-) Information Element.  SHOULD be |
|        |          | consistent within a record (i.e., if a        |
|        |          | source- Information Element has this flag     |
|        |          | set, the corresponding destination- element   |
|        |          | SHOULD have this flag set, and vice-versa.)   |
+--------+----------+-----------------------------------------------+
]]></artwork>
      </section>
      <section anchor="informationelementdescription">
        <name>informationElementDescription</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A UTF-8 <xref target="RFC3629"/> encoded Unicode string containing a human-readable description of an Information Element. The content of the informationElementDescription <bcp14>MAY</bcp14> be annotated with one or more language tags <xref target="RFC4646"/>, encoded in-line <xref target="RFC2482"/> within the UTF-8 string, in order to specify the language in which the description is written. Description text in multiple languages <bcp14>MAY</bcp14> tag each section with its own language tag; in this case, the description information in each language <bcp14>SHOULD</bcp14> have equivalent meaning. In the absence of any language tag, the "i-default" <xref target="RFC2277"/> language <bcp14>SHOULD</bcp14> be assumed.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See the Security Considerations section for notes on string handling for Information Element type records.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>A UTF-8 <xref target="RFC3629"/> encoded Unicode string containing a human-readable description of an Information Element. The content of the informationElementDescription <bcp14>MAY</bcp14> be annotated with one or more language tags <xref target="RFC4646"/>, encoded in-line <xref target="RFC2482"/> within the UTF-8 string, in order to specify the language in which the description is written. Description text in multiple languages <bcp14>MAY</bcp14> tag each section with its own language tag; in this case, the description information in each language <bcp14>SHOULD</bcp14> have equivalent meaning. In the absence of any language tag, the "i-default" <xref target="RFC2277"/> language <bcp14>SHOULD</bcp14> be assumed.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See the Security Considerations Section of <xref target="RFC5610"/> for notes on string handling for Information Element type records.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="distinctcountofdestinationipaddress">
        <name>distinctCountOfDestinationIPAddress</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The count of distinct destination IP address values for Original Flows contributing to this Aggregated Flow, without regard to IP version. This Information Element is preferred to the version-specific counters below, unless it is important to separate the counts by version.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>The count of distinct destination IP address values for Original Flows contributing to this Aggregated Flow, without regard to IP version. This Information Element is preferred to the version-specific counters, unless it is important to separate the counts by version.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section anchor="externaladdressrealm">
        <name>externalAddressRealm</name>
        <ul spacing="normal">
          <li>
            <t>OLD:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>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.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
          <li>
            <t>NEW:
            </t>
            <ul spacing="normal">
              <li>
                <dl>
                  <dt>Description:</dt>
                  <dd>
                    <t>This Information Element represents the external address realm where the packet is originated from or destined to.</t>
                  </dd>
                  <dt/>
                  <dd>
                    <t>See the internalAddressRealm IE for the detailed definition.</t>
                  </dd>
                </dl>
              </li>
            </ul>
          </li>
        </ul>
      </section>
    </section>
    <section anchor="security-considerations">
      <name>Security Considerations</name>
      <t>IPFIX security considerations are discussed in <xref section="8" sectionFormat="of" target="RFC7012"/>.</t>
    </section>
    <section anchor="iana-considerations">
      <name>IANA Considerations</name>
      <t>Sections 4 to 7 include actions for IANA. These actions are not repeated here.</t>
      <t>This document also requests IANA to update the reference clause of the "IPFIX Information Elements" registry <xref target="IANA-IPFIX"/> with the reference to this document.</t>
      <section anchor="ipfix-subregistry-for-ipv6-extension-headers">
        <name>IPFIX Subregistry for IPv6 Extension Headers</name>
        <t>This document requests IANA to create a new registry entitled "ipv6ExtensionHeaders Bits" under the IANA IPFIX registry group <xref target="IANA-IPFIX"/>.</t>
        <t>When a new code is assigned to an IPv6 EH in <xref target="IANA-EH"/>, a free bit is selected by IANA for this EH from "ipv6ExtensionHeaders Bits" registry and the registry is updated with the details that mirror the assigned EH. The "Label" mirrors the "keyword" of an EH as indicated in <xref target="IANA-Protocols"/>, while the "Protocol Number" mirrors the "Protocol Number" in <xref target="IANA-EH"/>. IANA is requested to add the following note to <xref target="IANA-EH"/>:</t>
        <ul empty="true">
          <li>
            <dl>
              <dt>Note:</dt>
              <dd>
                <t>When a new code is assigned to an IPv6 Extension Header, a free bit in [NEW_IPFIX_IPv6EH_SUBREGISTRY] is selected for this new Extension Header. &gt;&gt;[NEW_IPFIX_IPv6EH_SUBREGISTRY] is updated accordingly. Modifications to existing registrations must be mirrored in [NEW_IPFIX_IPv6EH_SUBREGISTRY].</t>
              </dd>
            </dl>
          </li>
        </ul>
        <ul empty="true">
          <li>
            <t>Note to the RFC Editor: Please replace [NEW_IPFIX_IPv6EH_SUBREGISTRY] with the link used by IANA for this new registry.</t>
          </li>
        </ul>
        <t>Otherwise, the registration policy for the registry is Expert Review (<xref section="4.5" sectionFormat="of" target="RFC8126"/>). See more details in <xref target="sec-de"/>.</t>
        <t>The initial values of this registry are as follows:</t>
        <artwork><![CDATA[
   Bit Label   Protocol Description
               Number
    0  DST      60      Destination Options for IPv6
    1  HOP       0      IPv6 Hop-by-Hop Options
    2  NoNxt     59     No Next Header for IPv6
    3  UNK              Unknown Layer 4 header
                        (compressed, encrypted, not supported)
    4  FRA0     44      Fragment header - first fragment
    5  RH       43      Routing header
    6  FRA1     44      Fragmentation header - not first fragment
    7 to 11             Unassigned
    12 MOB     135      Mobility Header
    13 ESP      50      Encapsulating Security Payload
    14 AH       51      Authentication Header
    15                  Unassigned
    16 HIP     139      Host Identity Protocol
    17 SHIM6   140      Shim6 Protocol
    18         253      Use for experimentation and testing
    19         254      Use for experimentation and testing
    20 to 255           Unassigned
]]></artwork>
      </section>
      <section anchor="sec-de">
        <name>Guidelines for the Designated Experts</name>
        <t>It is suggested that multiple designated experts be appointed for registry change requests.</t>
        <t>Criteria that should be applied by the designated experts include determining whether the proposed registration duplicates existing entries and whether the registration description is clear and fits the purpose of this registry.</t>
        <t>Within the review period, the designated experts will either approve or deny the registration request, communicating this decision to the IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful.</t>
      </section>
    </section>
  </middle>
  <back>
    <references>
      <name>References</name>
      <references anchor="sec-normative-references">
        <name>Normative References</name>
        <reference anchor="IANA-IPFIX" target="https://www.iana.org/assignments/ipfix/ipfix.xhtml">
          <front>
            <title>IP Flow Information Export (IPFIX) Entities</title>
            <author>
              <organization/>
            </author>
            <date>n.d.</date>
          </front>
        </reference>
        <reference anchor="IANA-EH" target="https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#ipv6-parameters-1">
          <front>
            <title>Internet Protocol Version 6 (IPv6) Parameters, IPv6 Extension Header Types</title>
            <author>
              <organization/>
            </author>
            <date>n.d.</date>
          </front>
        </reference>
        <reference anchor="IANA-TCP" target="https://www.iana.org/assignments/tcp-parameters/tcp-parameters.xhtml#tcp-parameters-1">
          <front>
            <title>Transmission Control Protocol (TCP) Parameters, TCP Option Kind Numbers</title>
            <author>
              <organization/>
            </author>
            <date>n.d.</date>
          </front>
        </reference>
        <reference anchor="IANA-Protocols" target="https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml">
          <front>
            <title>Protocol Numbers</title>
            <author>
              <organization/>
            </author>
            <date>n.d.</date>
          </front>
        </reference>
        <reference anchor="RFC7012">
          <front>
            <title>Information Model for IP Flow Information Export (IPFIX)</title>
            <author fullname="B. Claise" initials="B." role="editor" surname="Claise"/>
            <author fullname="B. Trammell" initials="B." role="editor" surname="Trammell"/>
            <date month="September" year="2013"/>
            <abstract>
              <t>This document defines the data types and management policy for the information model for the IP Flow Information Export (IPFIX) protocol. This information model is maintained as the IANA "IPFIX Information Elements" registry, the initial contents of which were defined by RFC 5102. This information model is used by the IPFIX protocol for encoding measured traffic information and information related to the traffic Observation Point, the traffic Metering Process, and the Exporting Process. Although this model was developed for the IPFIX protocol, it is defined in an open way that allows it to be easily used in other protocols, interfaces, and applications. This document obsoletes RFC 5102.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7012"/>
          <seriesInfo name="DOI" value="10.17487/RFC7012"/>
        </reference>
        <reference anchor="RFC7011">
          <front>
            <title>Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information</title>
            <author fullname="B. Claise" initials="B." role="editor" surname="Claise"/>
            <author fullname="B. Trammell" initials="B." role="editor" surname="Trammell"/>
            <author fullname="P. Aitken" initials="P." surname="Aitken"/>
            <date month="September" year="2013"/>
            <abstract>
              <t>This document specifies the IP Flow Information Export (IPFIX) protocol, which serves as a means for transmitting Traffic Flow information over the network. In order to transmit Traffic Flow information from an Exporting Process to a Collecting Process, a common representation of flow data and a standard means of communicating them are required. This document describes how the IPFIX Data and Template Records are carried over a number of transport protocols from an IPFIX Exporting Process to an IPFIX Collecting Process. This document obsoletes RFC 5101.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="77"/>
          <seriesInfo name="RFC" value="7011"/>
          <seriesInfo name="DOI" value="10.17487/RFC7011"/>
        </reference>
        <reference anchor="RFC2119">
          <front>
            <title>Key words for use in RFCs to Indicate Requirement Levels</title>
            <author fullname="S. Bradner" initials="S." surname="Bradner"/>
            <date month="March" year="1997"/>
            <abstract>
              <t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="2119"/>
          <seriesInfo name="DOI" value="10.17487/RFC2119"/>
        </reference>
        <reference anchor="RFC8174">
          <front>
            <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
            <author fullname="B. Leiba" initials="B." surname="Leiba"/>
            <date month="May" year="2017"/>
            <abstract>
              <t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="14"/>
          <seriesInfo name="RFC" value="8174"/>
          <seriesInfo name="DOI" value="10.17487/RFC8174"/>
        </reference>
        <reference anchor="RFC7013">
          <front>
            <title>Guidelines for Authors and Reviewers of IP Flow Information Export (IPFIX) Information Elements</title>
            <author fullname="B. Trammell" initials="B." surname="Trammell"/>
            <author fullname="B. Claise" initials="B." surname="Claise"/>
            <date month="September" year="2013"/>
            <abstract>
              <t>This document provides guidelines for how to write definitions of new Information Elements for the IP Flow Information Export (IPFIX) protocol. It provides instructions on using the proper conventions for Information Elements to be registered in the IANA IPFIX Information Element registry, and provides guidelines for expert reviewers to evaluate new registrations.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="184"/>
          <seriesInfo name="RFC" value="7013"/>
          <seriesInfo name="DOI" value="10.17487/RFC7013"/>
        </reference>
        <reference anchor="I-D.ietf-opsawg-ipfix-tcpo-v6eh">
          <front>
            <title>Extended TCP Options and IPv6 Extension Headers IPFIX Information Elements</title>
            <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
              <organization>Orange</organization>
            </author>
            <author fullname="Benoît Claise" initials="B." surname="Claise">
              <organization>Huawei</organization>
            </author>
            <date day="19" month="September" year="2023"/>
            <abstract>
              <t>   This document specifies new IP Flow Information Export (IPFIX)
   Information Elements (IEs) to solve some issues with existing
   ipv6ExtensionHeaders and tcpOptions IPFIX IEs, especially the ability
   to export any observed IPv6 extension headers or TCP options.

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-ipfix-tcpo-v6eh-01"/>
        </reference>
        <reference anchor="RFC6994">
          <front>
            <title>Shared Use of Experimental TCP Options</title>
            <author fullname="J. Touch" initials="J." surname="Touch"/>
            <date month="August" year="2013"/>
            <abstract>
              <t>This document describes how the experimental TCP option codepoints can concurrently support multiple TCP extensions, even within the same connection, using a new IANA TCP experiment identifier. This approach is robust to experiments that are not registered and to those that do not use this sharing mechanism. It is recommended for all new TCP options that use these codepoints.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6994"/>
          <seriesInfo name="DOI" value="10.17487/RFC6994"/>
        </reference>
        <reference anchor="RFC7270">
          <front>
            <title>Cisco-Specific Information Elements Reused in IP Flow Information Export (IPFIX)</title>
            <author fullname="A. Yourtchenko" initials="A." surname="Yourtchenko"/>
            <author fullname="P. Aitken" initials="P." surname="Aitken"/>
            <author fullname="B. Claise" initials="B." surname="Claise"/>
            <date month="June" year="2014"/>
            <abstract>
              <t>This document describes some additional IP Flow Information Export (IPFIX) Information Elements in the range of 1-127, which is the range compatible with field types used by NetFlow version 9 in RFC 3954, as specified in the IPFIX Information Model in RFC 7012.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7270"/>
          <seriesInfo name="DOI" value="10.17487/RFC7270"/>
        </reference>
        <reference anchor="RFC8126">
          <front>
            <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
            <author fullname="M. Cotton" initials="M." surname="Cotton"/>
            <author fullname="B. Leiba" initials="B." surname="Leiba"/>
            <author fullname="T. Narten" initials="T." surname="Narten"/>
            <date month="June" year="2017"/>
            <abstract>
              <t>Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).</t>
              <t>To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.</t>
              <t>This is the third edition of this document; it obsoletes RFC 5226.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="26"/>
          <seriesInfo name="RFC" value="8126"/>
          <seriesInfo name="DOI" value="10.17487/RFC8126"/>
        </reference>
      </references>
      <references anchor="sec-informative-references">
        <name>Informative References</name>
        <reference anchor="I-D.ietf-opsawg-rfc7125-update">
          <front>
            <title>An Update to the tcpControlBits IP Flow Information Export (IPFIX) Information Element</title>
            <author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
              <organization>Orange</organization>
            </author>
            <date day="12" month="October" year="2023"/>
            <abstract>
              <t>   RFC 7125 revised the tcpControlBits IP Flow Information Export
   (IPFIX) Information Element that was originally defined in RFC 5102
   to reflect changes to the TCP header control bits since RFC 793.
   However, that update is still problematic for interoperability
   because some flag values have subsequently been deprecated.

   This document removes stale information from the IPFIX registry and
   avoids future conflicts with the authoritative TCP Header Flags
   registry.

   This document obsoletes RFC 7125.

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-opsawg-rfc7125-update-05"/>
        </reference>
        <reference anchor="RFC7125">
          <front>
            <title>Revision of the tcpControlBits IP Flow Information Export (IPFIX) Information Element</title>
            <author fullname="B. Trammell" initials="B." surname="Trammell"/>
            <author fullname="P. Aitken" initials="P." surname="Aitken"/>
            <date month="February" year="2014"/>
            <abstract>
              <t>This document revises the tcpControlBits IP Flow Information Export (IPFIX) Information Element as originally defined in RFC 5102 to reflect changes to the TCP Flags header field since RFC 793.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="7125"/>
          <seriesInfo name="DOI" value="10.17487/RFC7125"/>
        </reference>
        <reference anchor="RFC5102">
          <front>
            <title>Information Model for IP Flow Information Export</title>
            <author fullname="J. Quittek" initials="J." surname="Quittek"/>
            <author fullname="S. Bryant" initials="S." surname="Bryant"/>
            <author fullname="B. Claise" initials="B." surname="Claise"/>
            <author fullname="P. Aitken" initials="P." surname="Aitken"/>
            <author fullname="J. Meyer" initials="J." surname="Meyer"/>
            <date month="January" year="2008"/>
            <abstract>
              <t>This memo defines an information model for the IP Flow Information eXport (IPFIX) protocol. It is used by the IPFIX protocol for encoding measured traffic information and information related to the traffic Observation Point, the traffic Metering Process, and the Exporting Process. Although developed for the IPFIX protocol, the model is defined in an open way that easily allows using it in other protocols, interfaces, and applications. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5102"/>
          <seriesInfo name="DOI" value="10.17487/RFC5102"/>
        </reference>
        <reference anchor="I-D.ietf-6man-eh-limits">
          <front>
            <title>Limits on Sending and Processing IPv6 Extension Headers</title>
            <author fullname="Tom Herbert" initials="T." surname="Herbert">
              <organization>SiPanda</organization>
            </author>
            <date day="4" month="October" year="2023"/>
            <abstract>
              <t>   This specification defines various limits that may be applied to
   receiving, sending, and otherwise processing packets that contain
   IPv6 extension headers.  The need for such limits is pragmatic to
   facilitate interoperability amongst hosts and routers in the presence
   of extension headers and thereby increasing the feasibility of
   deployment of extension headers.  The limits described herein
   establish the minimum baseline of support for use of extension
   headers on the Internet.  If it is known that all communicating
   parties for a particular communication, including destination hosts
   and any routers in the path, are capable of supporting more than the
   baseline then these default limits may be freely exceeded.

              </t>
            </abstract>
          </front>
          <seriesInfo name="Internet-Draft" value="draft-ietf-6man-eh-limits-08"/>
        </reference>
        <reference anchor="RFC3031">
          <front>
            <title>Multiprotocol Label Switching Architecture</title>
            <author fullname="E. Rosen" initials="E." surname="Rosen"/>
            <author fullname="A. Viswanathan" initials="A." surname="Viswanathan"/>
            <author fullname="R. Callon" initials="R." surname="Callon"/>
            <date month="January" year="2001"/>
            <abstract>
              <t>This document specifies the architecture for Multiprotocol Label Switching (MPLS). [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3031"/>
          <seriesInfo name="DOI" value="10.17487/RFC3031"/>
        </reference>
        <reference anchor="RFC3022">
          <front>
            <title>Traditional IP Network Address Translator (Traditional NAT)</title>
            <author fullname="P. Srisuresh" initials="P." surname="Srisuresh"/>
            <author fullname="K. Egevang" initials="K." surname="Egevang"/>
            <date month="January" year="2001"/>
            <abstract>
              <t>The NAT operation described in this document extends address translation introduced in RFC 1631 and includes a new type of network address and TCP/UDP port translation. In addition, this document corrects the Checksum adjustment algorithm published in RFC 1631 and attempts to discuss NAT operation and limitations in detail. This memo provides information for the Internet community.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3022"/>
          <seriesInfo name="DOI" value="10.17487/RFC3022"/>
        </reference>
        <reference anchor="RFC3234">
          <front>
            <title>Middleboxes: Taxonomy and Issues</title>
            <author fullname="B. Carpenter" initials="B." surname="Carpenter"/>
            <author fullname="S. Brim" initials="S." surname="Brim"/>
            <date month="February" year="2002"/>
            <abstract>
              <t>This document is intended as part of an IETF discussion about "middleboxes" - defined as any intermediary box performing functions apart from normal, standard functions of an IP router on the data path between a source host and destination host. This document establishes a catalogue or taxonomy of middleboxes, cites previous and current IETF work concerning middleboxes, and attempts to identify some preliminary conclusions. It does not, however, claim to be definitive. This memo provides information for the Internet community.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="3234"/>
          <seriesInfo name="DOI" value="10.17487/RFC3234"/>
        </reference>
        <reference anchor="RFC8158">
          <front>
            <title>IP Flow Information Export (IPFIX) Information Elements for Logging NAT Events</title>
            <author fullname="S. Sivakumar" initials="S." surname="Sivakumar"/>
            <author fullname="R. Penno" initials="R." surname="Penno"/>
            <date month="December" year="2017"/>
            <abstract>
              <t>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 the Collector applications that would receive this data and process it to present useful information. This document describes the formats for logging NAT events.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="8158"/>
          <seriesInfo name="DOI" value="10.17487/RFC8158"/>
        </reference>
        <reference anchor="RFC1631">
          <front>
            <title>The IP Network Address Translator (NAT)</title>
            <author fullname="K. Egevang" initials="K." surname="Egevang"/>
            <author fullname="P. Francis" initials="P." surname="Francis"/>
            <date month="May" year="1994"/>
            <abstract>
              <t>This memo proposes another short-term solution, address reuse, that complements CIDR or even makes it unnecessary. The address reuse solution is to place Network Address Translators (NAT) at the borders of stub domains. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="1631"/>
          <seriesInfo name="DOI" value="10.17487/RFC1631"/>
        </reference>
        <reference anchor="RFC6144">
          <front>
            <title>Framework for IPv4/IPv6 Translation</title>
            <author fullname="F. Baker" initials="F." surname="Baker"/>
            <author fullname="X. Li" initials="X." surname="Li"/>
            <author fullname="C. Bao" initials="C." surname="Bao"/>
            <author fullname="K. Yin" initials="K." surname="Yin"/>
            <date month="April" year="2011"/>
            <abstract>
              <t>This note describes a framework for IPv4/IPv6 translation. This is in the context of replacing Network Address Translation - Protocol Translation (NAT-PT), which was deprecated by RFC 4966, and to enable networks to have IPv4 and IPv6 coexist in a somewhat rational manner while transitioning to an IPv6 network. This document is not an Internet Standards Track specification; it is published for informational purposes.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6144"/>
          <seriesInfo name="DOI" value="10.17487/RFC6144"/>
        </reference>
        <reference anchor="RFC6146">
          <front>
            <title>Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers</title>
            <author fullname="M. Bagnulo" initials="M." surname="Bagnulo"/>
            <author fullname="P. Matthews" initials="P." surname="Matthews"/>
            <author fullname="I. van Beijnum" initials="I." surname="van Beijnum"/>
            <date month="April" year="2011"/>
          </front>
          <seriesInfo name="RFC" value="6146"/>
          <seriesInfo name="DOI" value="10.17487/RFC6146"/>
        </reference>
        <reference anchor="RFC6296">
          <front>
            <title>IPv6-to-IPv6 Network Prefix Translation</title>
            <author fullname="M. Wasserman" initials="M." surname="Wasserman"/>
            <author fullname="F. Baker" initials="F." surname="Baker"/>
            <date month="June" year="2011"/>
            <abstract>
              <t>This document describes a stateless, transport-agnostic IPv6-to-IPv6 Network Prefix Translation (NPTv6) function that provides the address-independence benefit associated with IPv4-to-IPv4 NAT (NAPT44) and provides a 1:1 relationship between addresses in the "inside" and "outside" prefixes, preserving end-to-end reachability at the network layer. This document defines an Experimental Protocol for the Internet community.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6296"/>
          <seriesInfo name="DOI" value="10.17487/RFC6296"/>
        </reference>
        <reference anchor="RFC0791">
          <front>
            <title>Internet Protocol</title>
            <author fullname="J. Postel" initials="J." surname="Postel"/>
            <date month="September" year="1981"/>
          </front>
          <seriesInfo name="STD" value="5"/>
          <seriesInfo name="RFC" value="791"/>
          <seriesInfo name="DOI" value="10.17487/RFC0791"/>
        </reference>
        <reference anchor="RFC8200">
          <front>
            <title>Internet Protocol, Version 6 (IPv6) Specification</title>
            <author fullname="S. Deering" initials="S." surname="Deering"/>
            <author fullname="R. Hinden" initials="R." surname="Hinden"/>
            <date month="July" year="2017"/>
            <abstract>
              <t>This document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="86"/>
          <seriesInfo name="RFC" value="8200"/>
          <seriesInfo name="DOI" value="10.17487/RFC8200"/>
        </reference>
        <reference anchor="RFC5475">
          <front>
            <title>Sampling and Filtering Techniques for IP Packet Selection</title>
            <author fullname="T. Zseby" initials="T." surname="Zseby"/>
            <author fullname="M. Molina" initials="M." surname="Molina"/>
            <author fullname="N. Duffield" initials="N." surname="Duffield"/>
            <author fullname="S. Niccolini" initials="S." surname="Niccolini"/>
            <author fullname="F. Raspall" initials="F." surname="Raspall"/>
            <date month="March" year="2009"/>
            <abstract>
              <t>This document describes Sampling and Filtering techniques for IP packet selection. It provides a categorization of schemes and defines what parameters are needed to describe the most common selection schemes. Furthermore, it shows how techniques can be combined to build more elaborate packet Selectors. The document provides the basis for the definition of information models for configuring selection techniques in Metering Processes and for reporting the technique in use to a Collector. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5475"/>
          <seriesInfo name="DOI" value="10.17487/RFC5475"/>
        </reference>
        <reference anchor="RFC6313">
          <front>
            <title>Export of Structured Data in IP Flow Information Export (IPFIX)</title>
            <author fullname="B. Claise" initials="B." surname="Claise"/>
            <author fullname="G. Dhandapani" initials="G." surname="Dhandapani"/>
            <author fullname="P. Aitken" initials="P." surname="Aitken"/>
            <author fullname="S. Yates" initials="S." surname="Yates"/>
            <date month="July" year="2011"/>
            <abstract>
              <t>This document specifies an extension to the IP Flow Information Export (IPFIX) protocol specification in RFC 5101 and the IPFIX information model specified in RFC 5102 to support hierarchical structured data and lists (sequences) of Information Elements in data records. This extension allows definition of complex data structures such as variable-length lists and specification of hierarchical containment relationships between Templates. Finally, the semantics are provided in order to express the relationship among multiple list elements in a structured data record. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="6313"/>
          <seriesInfo name="DOI" value="10.17487/RFC6313"/>
        </reference>
        <reference anchor="RFC1321">
          <front>
            <title>The MD5 Message-Digest Algorithm</title>
            <author fullname="R. Rivest" initials="R." surname="Rivest"/>
            <date month="April" year="1992"/>
            <abstract>
              <t>This document describes the MD5 message-digest algorithm. The algorithm takes as input a message of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest" of the input. This memo provides information for the Internet community. It does not specify an Internet standard.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="1321"/>
          <seriesInfo name="DOI" value="10.17487/RFC1321"/>
        </reference>
        <reference anchor="RFC3629">
          <front>
            <title>UTF-8, a transformation format of ISO 10646</title>
            <author fullname="F. Yergeau" initials="F." surname="Yergeau"/>
            <date month="November" year="2003"/>
            <abstract>
              <t>ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.</t>
            </abstract>
          </front>
          <seriesInfo name="STD" value="63"/>
          <seriesInfo name="RFC" value="3629"/>
          <seriesInfo name="DOI" value="10.17487/RFC3629"/>
        </reference>
        <reference anchor="RFC4646">
          <front>
            <title>Tags for Identifying Languages</title>
            <author fullname="A. Phillips" initials="A." surname="Phillips"/>
            <author fullname="M. Davis" initials="M." surname="Davis"/>
            <date month="September" year="2006"/>
            <abstract>
              <t>This document describes the structure, content, construction, and semantics of language tags for use in cases where it is desirable to indicate the language used in an information object. It also describes how to register values for use in language tags and the creation of user-defined extensions for private interchange. This document, in combination with RFC 4647, replaces RFC 3066, which replaced RFC 1766. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="4646"/>
          <seriesInfo name="DOI" value="10.17487/RFC4646"/>
        </reference>
        <reference anchor="RFC2482">
          <front>
            <title>Language Tagging in Unicode Plain Text</title>
            <author fullname="K. Whistler" initials="K." surname="Whistler"/>
            <author fullname="G. Adams" initials="G." surname="Adams"/>
            <date month="January" year="1999"/>
            <abstract>
              <t>This document proposed a mechanism for language tagging in plain text. This memo provides information for the Internet community.</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="2482"/>
          <seriesInfo name="DOI" value="10.17487/RFC2482"/>
        </reference>
        <reference anchor="RFC2277">
          <front>
            <title>IETF Policy on Character Sets and Languages</title>
            <author fullname="H. Alvestrand" initials="H." surname="Alvestrand"/>
            <date month="January" year="1998"/>
            <abstract>
              <t>This document is the current policies being applied by the Internet Engineering Steering Group (IESG) towards the standardization efforts in the Internet Engineering Task Force (IETF) in order to help Internet protocols fulfill these requirements. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t>
            </abstract>
          </front>
          <seriesInfo name="BCP" value="18"/>
          <seriesInfo name="RFC" value="2277"/>
          <seriesInfo name="DOI" value="10.17487/RFC2277"/>
        </reference>
        <reference anchor="RFC5610">
          <front>
            <title>Exporting Type Information for IP Flow Information Export (IPFIX) Information Elements</title>
            <author fullname="E. Boschi" initials="E." surname="Boschi"/>
            <author fullname="B. Trammell" initials="B." surname="Trammell"/>
            <author fullname="L. Mark" initials="L." surname="Mark"/>
            <author fullname="T. Zseby" initials="T." surname="Zseby"/>
            <date month="July" year="2009"/>
            <abstract>
              <t>This document describes an extension to the IP Flow Information Export (IPFIX) protocol, which is used to represent and transmit data from IP flow measurement devices for collection, storage, and analysis, to allow the encoding of IPFIX Information Model properties within an IPFIX Message stream. This enables the export of extended type information for enterprise-specific Information Elements and the storage of such information within IPFIX Files, facilitating interoperability and reusability among a wide variety of applications and tools. [STANDARDS-TRACK]</t>
            </abstract>
          </front>
          <seriesInfo name="RFC" value="5610"/>
          <seriesInfo name="DOI" value="10.17487/RFC5610"/>
        </reference>
      </references>
    </references>
    <?line 1040?>

<section numbered="false" anchor="acknowledgments">
      <name>Acknowledgments</name>
      <t>Thanks to Paul Aitken for the review. Special thanks to Andrew Feren for sharing data about scans of IPFIX data he collected.</t>
      <t>Thomas Graf tagged an issue with the forwardingStatus Information Element.</t>
      <t>Thanks to Eric Vyncke for the review and comments.</t>
    </section>
  </back>
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