Operations D. Voyer Internet-Draft Bell Canada Intended status: Standards Track S. Gopalakrishnan Expires: 21 April 2025 Cisco Systems T. Graf Swisscom B. Claise Huawei V. Satyanarayana Juniper Networks 18 October 2024 Export of GTP-U Information in IP Flow Information Export (IPFIX) draft-ietf-opsawg-ipfix-gtpu-00 Abstract This document introduces IP Flow Information Export Information Elements to identify 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 21 April 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Voyer, et al. Expires 21 April 2025 [Page 1] Internet-Draft IPFIX support for GTP-U October 2024 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 . . . . . . . . . . . . . . 3 4. Sample Use Cases . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5.1. gtpuFlags . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. gtpuMsgType . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. gtpuTEid . . . . . . . . . . . . . . . . . . . . . . . . 6 5.4. gtpuSequenceNum . . . . . . . . . . . . . . . . . . . . . 7 5.5. gtpuQFI . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.6. gtpuPduType . . . . . . . . . . . . . . . . . . . . . . . 8 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 8.1. Cisco IOS XR . . . . . . . . . . . . . . . . . . . . . . 9 9. Security Considerations . . . . . . . . . . . . . . . . . . . 10 10. Operational Considerations . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . 11 Appendix A. IPFIX Encoding Examples . . . . . . . . . . . . . . 11 A.1. Template Record . . . . . . . . . . . . . . . . . . . . . 12 A.1.1. Template Record and Data Set . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction A dedicated header, called GPRS Tunneling Protocol Header (GTP), is defined by 3GPP for use of GTP-C Control plane and GTP-U User Plane [TS.29281] traffic of mobile subscribers. This document specifies six IPFIX Information Elements (IEs) [RFC7012] for fields within a GTP-U header. 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. Voyer, et al. Expires 21 April 2025 [Page 2] Internet-Draft IPFIX support for GTP-U October 2024 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 Elements * Template * Template Record * Options Template * Options Template Record * Data Record * Data Set 3. IPFIX GTP-U Information Elements This section defines IPFIX IEs corresponding to various fields in the GTP-U. 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 corresponding flag value from gtpuFlags. Voyer, et al. Expires 21 April 2025 [Page 3] Internet-Draft IPFIX support for GTP-U October 2024 gtpuQFI 6-bit QoS flow identifier field defined in PDU Session Container extension header of GTP-U. gtpuPduType 4-bit PDU Type field defined in PDU Session Container extension header of GTP-U. 4. Sample Use Cases In order to identify the transport performance of PDU Sessions with specific QoS within a slice or within a group of slices hosted on the same UPF the GTP User Plane related IEs would be much helpful. For example when in case of one or a couple of dedicated UPFs are deployed per 5G slice, the slice is identified first using list of gNodeB IPs composing the slice and list of IPs of User Plane Function dedicated for the slice. The gNodeB and the User Plane Function form the tunnel endpoints. Also the traffic for individual PDU session per direction is identified using the GTP-U TEID, GTP-U PDU Type together with above mentioned tunnel endpoints. Further the traffic for specific QoS within a PDU session per direction is identified using the combination of GTP-U TEID, GTP-U PDU Type and GTP-U QFI attributes. It is possible that there may be multiple IP flows having the same attributes. In another scenario when multiple 5G slices are served by the same User Plane Function, the slice is identified using a separated list of gNodeB IPv6 addresses per slice. If Intermediate User Plane Function or Uplink Classifier is deployed there is an addition of a GTP-U tunnel between the Intermediate/Uplink-Classifier UPF and the final UPF. These brings a challenge for identifying the end to end path for a certain PDU session - where 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 tunnel, however the GTP-U TEIDs will be different since this is a different tunnel. 5. IANA Considerations IANA has added the following new IEs to the "IPFIX Information Elements" registry [RFC7012] available at [IANA-IPFIX]. Table 1 lists the GTP-U IEs: Voyer, et al. Expires 21 April 2025 [Page 4] Internet-Draft IPFIX support for GTP-U October 2024 +-------+-----------------+ |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 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 Data Type Semantics: flags Voyer, et al. Expires 21 April 2025 [Page 5] Internet-Draft IPFIX support for GTP-U October 2024 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] Voyer, et al. Expires 21 April 2025 [Page 6] Internet-Draft IPFIX support for GTP-U October 2024 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 Voyer, et al. Expires 21 April 2025 [Page 7] Internet-Draft IPFIX support for GTP-U October 2024 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 Voyer, et al. Expires 21 April 2025 [Page 8] Internet-Draft IPFIX support for GTP-U October 2024 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 and Dhananjay Patki 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 Voyer, et al. Expires 21 April 2025 [Page 9] Internet-Draft IPFIX support for GTP-U October 2024 9. Security Considerations There exists no extra security considerations regarding allocation of these IPFIX IEs compared to [RFC7012]. The IEs described in this document export GTP user plane data metrics on how packets are being forwarded in 5G 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 extensions defined in this draft requires deep parsing and extraction of fields from the packet. 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, . [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, . [RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model for IP Flow Information Export (IPFIX)", RFC 7012, DOI 10.17487/RFC7012, September 2013, . [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, . Voyer, et al. Expires 21 April 2025 [Page 10] Internet-Draft IPFIX support for GTP-U October 2024 [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, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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 [IANA-IPFIX] "IANA, "IP Flow Information Export (IPFIX) Entities"", . 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 Voyer, et al. Expires 21 April 2025 [Page 11] Internet-Draft IPFIX support for GTP-U October 2024 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: Voyer, et al. Expires 21 April 2025 [Page 12] Internet-Draft IPFIX support for GTP-U October 2024 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: daniel.voyer@bell.ca 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 Voyer, et al. 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