Export of GTP-U Information in
IP Flow Information Export (IPFIX)Bell Canadadaniel.voyer@bell.caCisco SystemsIndiasriragop@cisco.comCisco SystemsIndiarjohny@cisco.com
Operations and Management
OperationsThis document introduces IP Flow Information Export
Information Elements to identify informantion containted 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.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
traffic of mobile subscribers.This document specifies six IPFIX Information Elements (IEs)
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.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
when, and only when,
they appear in all capitals, as shown here.This document makes use of the terms defined in IPFIXIPFIX Information ElementsTemplateTemplate RecordOptions TemplateOptions Template RecordData RecordData SetThis section defines IPFIX IEs corresponding to various fields in the
GTP-U. 8-bit flags field
defined in the GTP-U. 8-bit message
type field defined in the GTP-U. 32-bit tunnel
endpoint identifier field defined in GTP-U. 16-bit
sequence number field defined in the GTP-U. 8-bit QoS flow
identifier field defined in PDU Session Container extension header
of GTP-U. 8-bit PDU Type
field defined in PDU Session Container extension header of
GTP-U.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.This document requests IANA to add the IEs listed in Table 1 below
to the "IPFIX Information Elements" registry
available at .Table 1 lists the GTP-U IEs:The authors would like to thank Ketan Talaulikar and
Dhananjay Patki for their reviews and valuable comments.Bell Canadacristian.staicu@bell.caBell Canadakandhla.chandi@bell.caThere exists no extra security considerations regarding allocation of
these IPFIX IEs compared to .The IEs described in this document export provider 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 as appropriate.General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)3GPPVersion 17.4.0IANA, "IP Flow Information Export (IPFIX) Entities"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.Sample template consisting of the GTP-U IEs:In this example, the Template ID is 256, which will be used in
the Data Record.The data set is represented as follows: