Operations                                                      D. Voyer
Internet-Draft                                               Bell Canada
Intended status: Standards Track                       S. Gopalakrishnan
Expires: 19 June 2025                                      Cisco Systems
                                                                 T. Graf
                                                                Swisscom
                                                               B. Claise
                                                                  Huawei
                                                        V. Satyanarayana
                                                        Juniper Networks
                                                        16 December 2024


   Export of GTP-U Information in IP Flow Information Export (IPFIX)
                    draft-ietf-opsawg-ipfix-gtpu-02

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

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

   This Internet-Draft will expire on 19 June 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.






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   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.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

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

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] 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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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 defined in the GTP-U.

   gtpuMsgType
      8-bit message type field defined in the GTP-U.

   gtpuTEid
      32-bit tunnel endpoint identifier field defined in GTP-U which
      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.  The presense 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.  The presense of this extension header is
      interpreted based on the extension header flag value from
      gtpuFlags.

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



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   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 intermediate UPF or Uplink Classifier 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.

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     |
        |       |                 |
        |       |                 |
        |       |                 |
        +-------+-----------------+

     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
      protocol, protocol type and presence of extension header, sequence
      number and N-PDU number defined in section 5.1 of the 3GPP
      specification [TS.29281].

   Abstract Data Type:  unsigned8



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   Data Type Semantics:  flags

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

   Reference:  [RFC-to-be]

5.2.  gtpuMsgType

   Name:  gtpuMsgType

   ElementID:  506

   Description:  8-bit Message type field indicating the type of GTP-U
      message defined in section 5.1 of the 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].

   Reference:  [RFC-to-be]

5.3.  gtpuTEid

   Name:  gtpuTEid

   ElementID:  507

   Description:  32-bit tunnel endpoint identifier field defined in
      section 5.1 of the 3GPP specification [TS.29281].  This field
      unambiguously identifies a tunnel endpoint in the receiving GTP-U
      protocol entity for a given UDP/IP endpoint.  The receiving side
      of a GTP tunnel locally assigns the TEID value the transmitting
      side has to use.  The TEID values are exchanged between tunnel
      endpoints using control plane messages.

   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]



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5.4.  gtpuSequenceNum

   Name:  gtpuSequenceNum

   ElementID:  508

   Description:  16-bit sequence number field defined in section 5.1
      (Optional Fields) of the 3GPP specification [TS.29281].

   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
      Container extension header of GTP-U.  This is defined in section
      5.5.3.3 of the 3GPP specification [TS.38415].  This is used to
      determine the QoS flow and QoS profile which are associated with
      the received packet.

      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





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      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 from 3GPP
      specification [TS.23501] for additional details.

   Reference:  [RFC-to-be]

5.6.  gtpuPduType

   Name:  gtpuPduType

   ElementID:  510

   Description:  4-bit PDU type field defined in PDU Session Container
      extension header of GTP-U.  This is defined in section 5.5.3 of
      the 3GPP specification [TS.38415].  This field indicates the
      structure of the PDU session user plane frame.

      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




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

   Reference:  [RFC-to-be]

6.  Acknowledgements

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

7.  Contributors

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


   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

   *  gtpuMsgType

   *  gtpuTEid

   *  gtpuSequenceNum

   *  gtpuQFI

   *  gtpuPduType



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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>.

   [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>.

   [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>.

   [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>.



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   [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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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 = 0x1,
             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:

       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 = 32             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Template ID = 256        |      Field Count = 6          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuFlags = 505            |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuMsgType = 506          |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuTEid = 507             |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuSequenceNum = 508      |      Field Length = 2         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuQFI = 509              |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|  gtpuPduType = 510          |      Field Length = 1         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           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 = 14         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | gtpuFlags     |  gtpuMsgType  |      gtpuTEid = 0x1           |
      | = 0x36        |  = 0xff       |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |   gtpuSequenceNum = 0x0000    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | gtpuQFI = 8   | gtpuPduType   |
      |               | = 0           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



              Figure 2: Data Set Encoding Format


Authors' Addresses

   Daniel Voyer
   Bell Canada
   Email: danvoyerwork@gmail.com


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


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


   Benoit Claise
   Huawei
   Email: benoit.claise@huawei.com


   Vyasraj Satyanarayana
   Juniper Networks
   Email: vyasraj@juniper.net






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