Export of GTP-U Information in IP Flow Information Export (IPFIX)
draft-ietf-opsawg-ipfix-gtpu-06

Operations                                                      D. Voyer
Internet-Draft                                         S. Gopalakrishnan
Intended status: Standards Track                           Cisco Systems
Expires: 4 January 2026                                          T. Graf
                                                                Swisscom
                                                        V. Satyanarayana
                                                        Juniper Networks
                                                               C. Staicu
                                                             Bell Canada
                                                             3 July 2025

   Export of GTP-U Information in IP Flow Information Export (IPFIX)
                    draft-ietf-opsawg-ipfix-gtpu-06

Abstract

   This document introduces IP Flow Information Export (IPFIX)
   Information Elements to report information contained in the Generic
   Packet Radio Service Tunneling Protocol User Plane header such as
   Tunnel Endpoint Identifier, and data contained in its session
   container extension header.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   This Internet-Draft will expire on 4 January 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IPFIX GTP-U Information Elements  . . . . . . . . . . . . . .   4
   4.  Sample Use Cases  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  gtpuFlags . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  gtpuMsgType . . . . . . . . . . . . . . . . . . . . . . .   7
     5.3.  gtpuTEid  . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.4.  gtpuSequenceNum . . . . . . . . . . . . . . . . . . . . .   8
     5.5.  gtpuQFI . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.6.  gtpuPduType . . . . . . . . . . . . . . . . . . . . . . .   9
     5.7.  gtpuTotalHdrLength  . . . . . . . . . . . . . . . . . . .  10
     5.8.  gtpuHeaderSection . . . . . . . . . . . . . . . . . . . .  11
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Implementation Status . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Cisco IOS XR  . . . . . . . . . . . . . . . . . . . . . .  11
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   10. Operational Considerations  . . . . . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  IPFIX Encoding Examples  . . . . . . . . . . . . . .  14
     A.1.  Template Record . . . . . . . . . . . . . . . . . . . . .  14
       A.1.1.  Template Record and Data Set  . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   A dedicated header, called GPRS Tunneling Protocol Header (GTP), is
   defined by the 3GPP for use of user Plane (GTP User (GTP-U))
   [TS.29281] (latest reference being Release 19) traffic of mobile
   subscribers.

   This document specifies six IPFIX Information Elements (IEs)
   [RFC7012] to export GTP-U information.

   Specifically, these IEs are used to export the GTP-U Tunnel Endpoint
   Identifier (TEID), QoS Flow Identifier (QFI), and PDU Type from the
   PDU Session Container extension header.

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   Some examples are provided in Appendix A.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document makes use of the terms defined in [RFC7011]

   *  IPFIX

   *  IPFIX Information Element

   *  Template

   *  Template Record

   *  Options Template

   *  Options Template Record

   *  Data Record

   *  Data Set

   This document makes use of following terms from [RFC6459]:

   *  User Plane

   The document uses the following abbreviations:

   *  IE: Information Element

   *  GTP: GPRS Tunneling Protocol

   *  GTP-U: GTP User

   *  GTP-C: GTP Control

   *  PDU: Protocol Data Unit

   *  TEID: Tunnel Endpoint Identifier

   *  UPF: User Plane Function

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   *  QFI: QoS Flow Identifier

3.  IPFIX GTP-U Information Elements

   This section defines IPFIX IEs corresponding to various fields in the
   GTP-U header.

   gtpuFlags
      8-bit flags field indicating the version of GTP-U header, protocol
      type, and presence of extension header, sequence number and N-PDU
      number defined in Section 5.1 of the 3GPP specification
      [TS.29281].  The bits are exported as observed.

   gtpuMsgType
      8-bit field which indicates the type of the GTP-U message as
      mentioned in section 6.1 of 3GPP specification [TS.29281].

   gtpuTEid
      32-bit tunnel endpoint identifier field unambiguously identifies a
      tunnel endpoint in the receiving GTP-U protocol entity for a given
      UDP/IP endpoint.

   gtpuSequenceNum
      16-bit sequence number field defined in the GTP-U.  This field is
      interpreted based on the sequence number flag value from
      gtpuFlags.

   gtpuQFI
      6-bit QoS flow identifier field defined in PDU Session Container
      extension header of GTP-U.  This may be used to determine the QoS
      flow and QoS profile which are associated with the received
      packet.  The presence of this extension header is interpreted
      based on the extension header flag value from gtpuFlags.

   gtpuPduType
      4-bit PDU type field defined in PDU Session Container extension
      header of GTP-U.  This field indicates the structure of the PDU
      session user plane frame.  The presence of this extension header
      is interpreted based on the extension header flag value from
      gtpuFlags.

   gtpuTotalHdrLength
      8-bit field indicating the total length of the GTP-U header which
      includes mandatory fields and all the optional headers as defined
      in Section 5 of the 3GPP specification [TS.29281].

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   gtpuHeaderSection
      This Information Element carries a series of n octets from the
      GTP-U header mandatory fields and all the following optional
      headers if any, defined in Section 5 of the 3GPP specification
      [TS.29281] as a series of octets in IPFIX.

4.  Sample Use Cases

   The GTP-U related IPFIX IEs are helpful in order to identify the
   transport performance of PDU Sessions, e.g., with specific QoS class
   within a network slice (refer to [I-D.ietf-teas-5g-ns-ip-mpls]) or
   within a group of network slices hosted on the same User Plane
   Function (UPF).

   For example, when a set of UPFs are deployed per 5G slice, the slice
   is identified first using a list of gNodeB IP addresses composing the
   slice and a list of IP addresses of UPFs dedicated for the slice.
   The gNodeB and the UPF form the tunnel endpoints.  The traffic for
   each individual PDU Session per direction is identified using the
   GTP-U TEID, GTP-U PDU Type together with the above mentioned IP
   tunnel endpoints.  Furthermore, the traffic for a specific QoS class
   within a PDU Session per traffic direction is identified using the
   combination of GTP-U TEID, GTP-U PDU Type, and GTP-U QFI attributes.
   It is possible that within the same PDU session there might be
   multiple IP flows having the same attributes.

   In another scenario when multiple 5G slices share the same UPF, each
   slice is identified using a separated list of gNodeB IPv4 or IPv6
   addresses per slice.  If an Uplink Classifier (refer to section 3.1
   of [TS.23501]) is deployed there is an addition of a GTP-U tunnel
   between the Intermediate/Uplink-Classifier UPF and the final UPF.
   This brings a challenge for identifying the end-to-end path for a
   certain PDU Session - the GTP-U PDU Type and GTP-U QFI attributes
   from the gNodeB and Intermediate/Uplink-Classifier UPF tunnel will be
   the same on the Intermediate/Uplink-Classifier and final UPF tunnels,
   however the GTP-U TEIDs will be different since on each tunnel.

   Additionally, exporting GTP-U IEs together with transportChecksum IE
   would help detect misbehaving nodes particularly when using GTP-U
   over IPv6.

5.  IANA Considerations

   IANA has registered the following IEs in the "IPFIX Information
   Elements" registry available at [IANA-IPFIX].

   Table 1 lists the GTP-U IEs:

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        +-------+-------------------+
        |Element| Name              |
        |       |                   |
        |   ID  |                   |
        |       |                   |
        +-------+-------------------+
        | 505   | gtpuFlags         |
        |       |                   |
        +-------+-------------------+
        | 506   | gtpuMsgType       |
        |       |                   |
        +-------+-------------------+
        | 507   | gtpuTEid          |
        |       |                   |
        +-------+-------------------+
        | 508   | gtpuSequenceNum   |
        |       |                   |
        +-------+-------------------+
        | 509   | gtpuQFI           |
        |       |                   |
        +-------+-------------------+
        | 510   | gtpuPduType       |
        |       |                   |
        +-------+-------------------+
        | TBD1  | gtpuTotalHdrLength|
        |       |                   |
        +-------+-------------------+
        | TBD2  | gtpuHeaderSection |
        |       |                   |
        +-------+-------------------+

     Table 1: GTP-U IEs in the "IPFIX Information Elements" Registry

   IANA is requested to update these entries as indicated in the
   following subsections.

5.1.  gtpuFlags

   Name:  gtpuFlags

   ElementID:  505

   Description:  8-bit flags field indicating the version of GTP-U
      header, protocol type, and presence of extension header, sequence
      number and N-PDU number defined in Section 5.1 of the 3GPP
      specification [TS.29281].  The bits are exported as observed.

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      The basic encoding is 8 bits.  The layout of basic encoding is as
      follows:

                MSB -   0     1    2    3    4    5    6    7   - LSB
                      +----+----+----+----+----+----+----+----+
                      |           8 bit flags value           |
                      +----+----+----+----+----+----+----+----+

      Examples:

      value : 0x34

      binary: 00110100

      decode: 00110100 - Flags value

      value : 0x30

      binary: 00110000

      decode: 00110000 - Flags value

   Abstract Data Type:  unsigned8

   Data Type Semantics:  flags

   Additional Information:  Refer to Section 5.1 of [TS.29281].

   Reference:  [RFC-to-be]

5.2.  gtpuMsgType

   Name:  gtpuMsgType

   ElementID:  506

   Description:  8-bit field which indicates the type of the GTP-U
      message as mentioned in section 6.1 of 3GPP specification
      [TS.29281].

   Abstract Data Type:  unsigned8

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5.1 of the 3GPP
      specification [TS.29281].

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   Reference:  [RFC-to-be]

5.3.  gtpuTEid

   Name:  gtpuTEid

   ElementID:  507

   Description:  32-bit tunnel endpoint identifier field unambiguously
      identifies a tunnel endpoint in the receiving GTP-U protocol
      entity for a given UDP/IP endpoint.

   Abstract Data Type:  unsigned32

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5.1 of the 3GPP
      specification [TS.29281].

   Reference:  [RFC-to-be]

5.4.  gtpuSequenceNum

   Name:  gtpuSequenceNum

   ElementID:  508

   Description:  16-bit sequence number field defined in the GTP-U.
      This field is interpreted based on the sequence number flag value
      from gtpuFlags.

   Abstract Data Type:  unsigned16

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5.1 of the 3GPP
      specification [TS.29281].

   Reference:  [RFC-to-be]

5.5.  gtpuQFI

   Name:  gtpuQFI

   ElementID:  509

   Description:  6-bit QoS flow identifier field defined in PDU Session

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      Container extension header of GTP-U.  This may be used to
      determine the QoS flow and QoS profile which are associated with
      the received packet.  The presence of this extension header is
      interpreted based on the extension header flag value from
      gtpuFlags.

      The basic encoding is 8 bits.  The layout of basic encoding is as
      follows:

                MSB -   0     1    2    3    4    5    6    7   - LSB
                      +----+----+----+----+----+----+----+----+
                      |Reserved |       6 bit QFI value       |
                      +----+----+----+----+----+----+----+----+

      Examples:

      value : 0x08

      binary: 00001000

      decode: 001000 - QFI value

      value : 0x3e

      binary: 00111110

      decode: 111110 - QFI value

   Abstract Data Type:  unsigned8

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5.5.3.3 of the 3GPP
      specification [TS.38415] and Section 5.7.1.1 of the 3GPP
      specification [TS.23501].

   Reference:  [RFC-to-be]

5.6.  gtpuPduType

   Name:  gtpuPduType

   ElementID:  510

   Description:  4-bit PDU type field defined in PDU Session Container

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      extension header of GTP-U.  This field indicates the structure of
      the PDU session user plane frame.  The presence of this extension
      header is interpreted based on the extension header flag value
      from gtpuFlags.

      The basic encoding is 8 bits.  The layout of basic encoding is as
      follows:

                MSB -   0     1    2    3    4    5    6    7   - LSB
                      +----+----+----+----+----+----+----+----+
                      |     Reserved      |  4 bit PDU Type   |
                      +----+----+----+----+----+----+----+----+

      Examples:

      value : 0x01

      binary: 00000001

      decode: 0001 - PDU Type value

   Abstract Data Type:  unsigned8

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5.5.3 of the 3GPP
      specification [TS.38415].

   Reference:  [RFC-to-be]

5.7.  gtpuTotalHdrLength

   Name:  gtpuHeaderLength

   ElementID:  TBD1

   Description:  8-bit field indicating the total header length of the
      GTP-U which includes mandatory fields and all the optional headers
      as defined in Section 5 of the 3GPP specification [TS.29281].

   Abstract Data Type:  unsigned8

   Data Type Semantics:  identifier

   Additional Information:  Refer to Section 5 of [TS.29281].

   Reference:  [RFC-to-be]

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5.8.  gtpuHeaderSection

   Name:  gtpuHeaderSection

   ElementID:  TBD2

   Description:  This Information Element carries a series of n octets
      from the GTP-U header mandatory fields and all the following
      optional headers if any, defined in Section 5 of the 3GPP
      specification [TS.29281] as a series of octets in IPFIX

   Abstract Data Type:  octetArray

   Data Type Semantics:  default

   Additional Information:  Refer to Section 5 of [TS.29281].

   Reference:  [RFC-to-be]

6.  Acknowledgements

   The authors would like to thank Benoit Claise, Ketan Talaulikar,
   Dhananjay Patki, Paul Aitken and Shraddha Hegde for their reviews and
   valuable comments.

7.  Contributors

   Kandhla Chandi
   Bell Canada
   Email: kandhla.chandi@bell.ca

   Ralu Johny
   Cisco
   Email: rjohny@cisco.com

8.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing.

8.1.  Cisco IOS XR

   Cisco implemented the following IEs as part of a test implementation
   in the IOS XR platform:

   *  gtpuFlags

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   *  gtpuMsgType

   *  gtpuTEid

   *  gtpuSequenceNum

   *  gtpuQFI

   *  gtpuPduType

9.  Security Considerations

   There exist no extra security considerations regarding allocation of
   these IPFIX IEs compared to [RFC7012].

   The IEs described in this document export GTP user plane data
   information on how packets are being forwarded in a 3GPP network.
   Applications and operators using the IEs described in this document
   must evaluate the sensitivity of this information in their
   implementation context, and apply the data-at-rest storage guidance
   in Section 11.8 of [RFC7011] as appropriate.

10.  Operational Considerations

   The IPFIX IEs defined in this document require extraction of fields
   from packets.  There may exist older devices in the network that do
   not support extensions defined in this document.  For those devices
   [RFC7133] defines dataLinkFrameSection which is a useful mechanism to
   export the packet header as a fallback scenario.  However, when
   dataLinkFrameSection is used, Flow aggregation as per [RFC7015] can't
   be applied.  This document will serve as a guideline to extract the
   necessary fields from the GTP-U header for the above scenarios.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

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   [RFC7012]  Claise, B., Ed. and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              DOI 10.17487/RFC7012, September 2013,
              <https://www.rfc-editor.org/info/rfc7012>.

   [RFC7015]  Trammell, B., Wagner, A., and B. Claise, "Flow Aggregation
              for the IP Flow Information Export (IPFIX) Protocol",
              RFC 7015, DOI 10.17487/RFC7015, September 2013,
              <https://www.rfc-editor.org/info/rfc7015>.

   [RFC7133]  Kashima, S., Kobayashi, A., Ed., and P. Aitken,
              "Information Elements for Data Link Layer Traffic
              Measurement", RFC 7133, DOI 10.17487/RFC7133, May 2014,
              <https://www.rfc-editor.org/info/rfc7133>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [TS.23501] 3GPP, "5G; System architecture for the 5G System (5GS)",
              Version 17.11.0, 3GPP TS 23.501, January 2024.

   [TS.29281] 3GPP, "General Packet Radio System (GPRS) Tunnelling
              Protocol User Plane (GTPv1-U)", Version 17.4.0, 3GPP
              TS 29.281, October 2022.

   [TS.38415] 3GPP, "NG-RAN; PDU Session User Plane Protocol)", Version
              17.1.0, 3GPP TS 38.415, February 2024.

11.2.  Informative References

   [I-D.ietf-teas-5g-ns-ip-mpls]
              Szarkowicz, K. G., Ed., Roberts, R., Ed., Lucek, J.,
              Boucadair, M., Ed., and L. M. Contreras, "A Realization of
              Network Slices for 5G Networks Using Current IP/MPLS
              Technologies", Work in Progress, Internet-Draft, draft-
              ietf-teas-5g-ns-ip-mpls-13, 5 December 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-5g-
              ns-ip-mpls-13>.

   [IANA-IPFIX]
              "IANA, "IP Flow Information Export (IPFIX) Entities"",
              <https://www.iana.org/assignments/ipfix/ipfix.xhtml>.

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   [RFC6459]  Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen,
              T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, DOI 10.17487/RFC6459, January 2012,
              <https://www.rfc-editor.org/info/rfc6459>.

Appendix A.  IPFIX Encoding Examples

   In this section, an example is provided to show IPFIX encoding format
   for the GTP-U introduced IEs.  Template definition and data set
   corresponding to an observed GTP-U header is illustrated below.

             Observed GTP-U Header:
             Flags = 0x36, Message Type = 0xff, TEID = 0x01,
             Sequence number = 0x0000,
             Next extension header type = 0x85 (PDU Session container),
             PDU Type = 0, QFI = 8

A.1.  Template Record

A.1.1.  Template Record and Data Set

   Sample template consisting of the GTP-U IEs:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          SET ID = 2           |       Length = 40             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 256        |      Field Count = 8          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuFlags = 505            |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuMsgType = 506          |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuSequenceNum = 508      |      Field Length = 2         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuTEid = 507             |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuQFI = 509              |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuPduType = 510          |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuTotalHdrLength = TBD1  |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuHeaderSection = TBD2   |      Field Length = 0xFFFF    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: Sample Template Record

   In this example, the Template ID is 256, which will be used in the
   Data Record.

   The data set is represented as follows:

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         SET ID = 256          |           Length = 32         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | gtpuFlags     |  gtpuMsgType  |   gtpuSequenceNum= 0x0000     |
      | = 0x36        |  = 0xff       |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   gtpuTEid = 0x00000001                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | gtpuQFI = 8   | gtpuPduType   |  gtpuTotalHdr |  Length = 16  |
      |               | = 0           |  Length = 16  |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0x36            0xff           0x00             0x8a     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0x00            0x00           0x00             0x01     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0x00            0x00           0x00             0x85     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0x01            0x10           0x08             0x00     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: Data Set Encoding Format

Authors' Addresses

   Daniel Voyer
   Cisco Systems
   Email: danvoyerwork@gmail.com

   Sriram Gopalakrishnan
   Cisco Systems
   India
   Email: sriragop@cisco.com

   Thomas Graf
   Swisscom
   Email: thomas.graf@swisscom.com

   Vyasraj Satyanarayana
   Juniper Networks
   Email: vyasraj@juniper.net

Voyer, et al.            Expires 4 January 2026                [Page 16]
Internet-Draft           IPFIX support for GTP-U               July 2025

   Cristian Staicu
   Bell Canada
   Email: cristian.staicu@bell.ca

Voyer, et al.            Expires 4 January 2026                [Page 17]