Internet DRAFT - draft-voyersriram-opsawg-ipfix-gtpu
draft-voyersriram-opsawg-ipfix-gtpu
Operations D. Voyer
Internet-Draft Bell Canada
Intended status: Standards Track S. Gopalakrishnan
Expires: 26 August 2024 Cisco Systems
T. Graf
Swisscom
B. Claise
Huawei
V. Satyanar
Juniper Networks
23 February 2024
Export of GTP-U Information in IP Flow Information Export (IPFIX)
draft-voyersriram-opsawg-ipfix-gtpu-03
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
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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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 . . . . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. IPFIX Encoding Examples . . . . . . . . . . . . . . 9
A.1. Template Record . . . . . . . . . . . . . . . . . . . . . 10
A.1.1. Template Record and Data Set . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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.
Some examples are provided in Appendix A.
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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.
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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
This document requests IANA to add the IEs listed in Table 1 below to
the "IPFIX Information Elements" registry [RFC7012] available at
[IANA-IPFIX].
Table 1 lists the GTP-U IEs:
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+-------+-----------------+
|Element| Name |
| | |
| ID | |
| | |
+-------+-----------------+
| TBD1 | gtpuFlags |
| | |
+-------+-----------------+
| TBD2 | gtpuMsgType |
| | |
+-------+-----------------+
| TBD3 | gtpuTEid |
| | |
| | |
+-------+-----------------+
| TBD4 | gtpuSequenceNum |
| | |
+-------+-----------------+
| TBD5 | gtpuQFI |
| | |
| | |
| | |
| | |
+-------+-----------------+
| TBD6 | gtpuPduType |
| | |
| | |
| | |
+-------+-----------------+
Table 1: GTP-U IEs in the "IPFIX Information Elements" Registry
5.1. gtpuFlags
Name: gtpuFlags
ElementID: TBD1
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
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Additional Information: Refer to section 5.1 of the 3GPP
specification [TS.29281].
Reference: [RFC-to-be]
5.2. gtpuMsgType
Name: gtpuMsgType
ElementID: TBD2
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: TBD3
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 end
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: TBD4
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: TBD5
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.
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: TBD6
Description: 4-bit PDU type field defined in PDU Session Container
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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.
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]
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. 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.
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<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>.
[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>.
[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.
9.2. Informative References
[IANA-IPFIX]
"IANA, "IP Flow Information Export (IPFIX) Entities"",
<https://www.iana.org/assignments/ipfix/ipfix.xhtml>.
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.
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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 = TBD1 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| gtpuMsgType = TBD2 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| gtpuTEid = TBD3 | Field Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| gtpuSequenceNum = TBD4 | Field Length = 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| gtpuQFI = TBD5 | Field Length = 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| gtpuPduType = TBD6 | 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: 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 Satyanar
Juniper Networks
Email: vyasraj@juniper.net
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