



Internet Engineering Task Force (IETF)                           T. Graf
Request for Comments: 9951                                      Swisscom
Category: Standards Track                                      B. Claise
ISSN: 2070-1721                                                   Huawei
                                                           A. Huang-Feng
                                                               INSA-Lyon
                                                              April 2026


   Export of Delay Performance Metrics in IP Flow Information Export
                                (IPFIX)

Abstract

   This document specifies new IP Flow Information Export (IPFIX)
   Information Elements to export the On-Path delay at each Operations,
   Administration, and Maintenance (OAM) transit and decapsulating
   nodes.  The On-Path delay is defined as the delay between the OAM
   header encapsulating node and each OAM header transit and OAM header
   decapsulating nodes.  This delay measurement is computed by an On-
   Path Telemetry protocol and is exported by the IPFIX process.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9951.

Copyright Notice

   Copyright (c) 2026 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.  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.  Terminology
   3.  Solution
   4.  Performance Metrics
     4.1.  IP One-Way Delay Hybrid Type I Performance Metrics
       4.1.1.  Summary
       4.1.2.  Description
       4.1.3.  Reference
       4.1.4.  Change Controller
       4.1.5.  Version of Registry Format
     4.2.  Metric Definition
       4.2.1.  Reference Definition
       4.2.2.  Fixed Parameters
     4.3.  Method of Measurement
       4.3.1.  Reference Methods
       4.3.2.  Packet Stream Generation
       4.3.3.  Traffic Filtering (Observation) Details
       4.3.4.  Sampling Distribution
       4.3.5.  Runtime Parameters and Data Format
       4.3.6.  Roles
     4.4.  Output
       4.4.1.  Type
       4.4.2.  Reference Definition
       4.4.3.  Administrative Items
       4.4.4.  Comments and Remarks
   5.  Use Cases
   6.  IANA Considerations
     6.1.  Performance Metrics
     6.2.  IPFIX Entities
       6.2.1.  pathDelayMeanDeltaMicroseconds
       6.2.2.  pathDelayMinDeltaMicroseconds
       6.2.3.  pathDelayMaxDeltaMicroseconds
       6.2.4.  pathDelaySumDeltaMicroseconds
   7.  Operational Considerations
     7.1.  Time Accuracy
     7.2.  Mean Delay
     7.3.  Reduced-Size Encoding
     7.4.  Measurement Interval
     7.5.  In-Packet OAM Application
   8.  Security Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  IPFIX Encoding Examples
     A.1.  Aggregated On-Path Delay Examples
       A.1.1.  Template Record and Data Set with Mean Delta
       A.1.2.  Template Record and Data Set with Sum Delta
   Acknowledgements
   Authors' Addresses

1.  Introduction

   Network operators usually maintain statistical views of delay across
   their networks to support diagnostics and performance analysis.
   These views assist in identifying the location, extent, and potential
   causes of abnormal delay affecting specific customer traffic or
   services.  To achieve this, delay-related metrics need to be reported
   from devices covering both data and control planes.  Further, in
   order to understand which customers are affected, delay-related
   metrics need to be reported in the context of the customer data
   plane.  This correlation enables the detection of changes in
   forwarding paths, such as updated intermediate hops or interfaces,
   and of the resulting impact on delay experienced by customer traffic.

   Delay measurements in the network are computed using an On-Path
   Telemetry protocol, which inserts metadata into the data-plane packet
   when entering the monitored domain [RFC9232].  To compute delay
   measurements, the On-Path Telemetry protocol inserts a timestamp
   reference when entering the OAM encapsulating node.  Implementation
   examples are In situ Operations, Administration, and Maintenance
   (IOAM) [RFC9197] or Enhanced Alternate Marking [ENH-ALT-MARKING].

   Two modes of On-Path Telemetry are generally recognized: passport
   mode, in which only the OAM header decapsulating node of the OAM
   domain reports metrics; and postcard mode, in which OAM header
   transit nodes also export On-Path Telemetry data.  Both modes enable
   exposure of per-hop performance metrics, including delay
   accumulation.  The approach defined in this document is primarily
   applicable to postcard mode.

   To enable the export of the delay-related metrics via IPFIX
   [RFC7011], this document defines four new IPFIX Information Elements
   (IEs), exposing the On-Path delay on OAM header transit and
   decapsulating nodes, following the principles of postcard mode.

   This enables the computation of delay metrics (minimum, maximum, and
   mean) directly on the OAM header transit and decapsulating node,
   allowing aggregation within the Flow Record.

   As these IEs represent performance metrics, they are also registered
   in the IANA "Performance Metrics Registry" [IANA-PERF-METRIC] in
   accordance with [RFC8911].

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 defines the following terms:

   OAM Header Encapsulating Node:
      Receives the IP packets, encapsulates the packets with an OAM
      header, and adds the timestamp into the OAM header.

   OAM Header Transit Node:
      Receives the IP packets, then measures the delay between the
      timestamp in the packet and the timestamp when the packet was
      received.

   OAM Header Decapsulating Node:
      Receives the IP packets, computes the delay between the timestamp
      in the packet and the timestamp when the packet was received, and
      removes the OAM header from the packet.

   This document makes use of the terms defined in [RFC7011], [RFC8911]
   and [RFC7799].

   The following terms are used as defined in [RFC7011]:

   *  Collector

   *  Exporter

   *  Flow

   *  Flow Record

   *  IPFIX

   *  IPFIX Information Elements (IEs)

   *  Observation Point

   The following terms are used as defined in [RFC8911]:

   *  Performance Metric

   *  Performance Metrics Registry

   *  Registered Performance Metric

   The following term is used as defined in Section 3.8 of [RFC7799]:

   *  Hybrid Type I

3.  Solution

   In line with the guidelines for Registered Performance Metric
   requesters and reviewers [RFC8911], each metric is specified with its
   required characteristics (e.g., Identifier, Name, URI, Status,
   Requester, Revision, Description) to ensure comparability of
   measurement results across implementations and environments.  These
   characteristics are registered in the IANA "Performance Metrics
   Registry" [IANA-PERF-METRIC].  Metric naming follows the
   "MetricType_Method_SubTypeMethod_... Spec_Units_Output" convention
   defined in Section 7.1.2 of [RFC8911].

   This document defines the following performance metrics and IPFIX
   Information Elements:

     +=============================+================================+
     | Performance Metric          | IPFIX Information Element      |
     +=============================+================================+
     | OWDelay_HybridType1_I       | pathDelayMeanDeltaMicroseconds |
     | P_RFC9951_Seconds_Mean (27) | (530)                          |
     +-----------------------------+--------------------------------+
     | OWDelay_HybridType1_I       | pathDelayMinDeltaMicroseconds  |
     | P_RFC9951_Seconds_Min (28)  | (531)                          |
     +-----------------------------+--------------------------------+
     | OWDelay_HybridType1_I       | pathDelayMaxDeltaMicroseconds  |
     | P_RFC9951_Seconds_Max (29)  | (532)                          |
     +-----------------------------+--------------------------------+
     | OWDelay_HybridType1_I       | pathDelaySumDeltaMicroseconds  |
     | P_RFC9951_Seconds_Sum (30)  | (533)                          |
     +-----------------------------+--------------------------------+

        Table 1: Mapping Between IPFIX IEs and Performance Metrics

   Assuming time synchronization on devices, the delay is measured by
   calculating the difference between the timestamp imposed with On-Path
   Telemetry in the packet at an OAM header encapsulating node and the
   timestamp exported in the IPFIX Flow Record from the OAM header
   transit and OAM header decapsulating nodes.  The lowest, highest,
   mean, and the sum of measured path delay can be exported, thanks to
   the different IPFIX IE specifications.

                          On-Path Telemetry Domain
                 .........................................
                 .                                       .
                 .    D1                                 .
                 . x------->                              .
                 .                                       .
                 .          D2                           .
                 . x-------------------->                .
                 .                                       .
                 .                  D3                   .
                 . x---------------------------------->  .
                 .                                       .
   (H1) -----> (R0) ------> (R1) ------> (R2) -------> (R3) -----> (H2)
   Host 1  Encapsulating   Transit      Transit   Decapsulating  Host 2
               Node         Node 1       Node 2        Node
                 .                                       .
                 .                                       .
                 .........................................

        Figure 1: Delay Use Case: Packets Flow from Host 1 to Host 2

   In the use case shown in Figure 1, using On-Path Telemetry to export
   the delay metrics, the node R1 exports the delay D1, the node R2
   exports the delay D2, and the OAM header decapsulating node R3
   exports the total delay D3 for the same flow using IPFIX.

   This solution enables the computation of delay metrics (minimum,
   maximum, and mean) directly on the OAM header transit and
   decapsulating node, allowing aggregation within the Flow Record.
   This reduces both export bandwidth and processing requirements on the
   Collector.  To compute these metrics locally, the Exporter's Metering
   Process must perform per-packet caching and processing, particularly
   when computing mean delay under Flow Aggregation [RFC7015].  A less
   computationally intensive alternative is to export the sum of delays,
   allowing the Collector to compute the mean via a simple division
   using the packet count.

   In contrast, if no delay processing occurs on the OAM header transit
   or decapsulating node, each packet must be exported as an individual
   Flow Record, including timestamp information, as specified in
   [IPFIX-ALT-MARK].  The Collector must then compute the delay metrics
   and reconstruct the aggregated Flow Record accordingly.

4.  Performance Metrics

   This section defines four new performance metrics following the
   template defined in Section 11 of [RFC8911].

4.1.  IP One-Way Delay Hybrid Type I Performance Metrics

   This section specifies four performance metrics for the Hybrid Type I
   assessment of IP One-Way Delay; they have been registered in the IANA
   "Performance Metrics Registry" [IANA-PERF-METRIC].

   All column entries besides the Identifier, Name, URI, Description,
   Reference Description (Output only) categories are the same; thus,
   this section defines four closely related performance metrics.  As a
   result, IANA has assigned corresponding URIs to each of the four
   registered performance metrics.

4.1.1.  Summary

   This category includes multiple indexes of the registered performance
   metrics: the Identifier and Metric Name.

4.1.1.1.  ID (Identifier)

   IANA has allocated the numeric Identifiers 27, 28, 29, and 30 for the
   four Named Metric Entries in the following section.

4.1.1.2.  Name

   27:  OWDelay_HybridType1_IP_RFC9951_Seconds_Mean

   28:  OWDelay_HybridType1_IP_RFC9951_Seconds_Min

   29:  OWDelay_HybridType1_IP_RFC9951_Seconds_Max

   30:  OWDelay_HybridType1_IP_RFC9951_Seconds_Sum

4.1.1.3.  URI

   URI:
      <https://www.iana.org/assignments/performance-metrics/
      OWDelay_HybridType1_IP_RFC9951_Seconds_Mean>

   URI:
      <https://www.iana.org/assignments/performance-metrics/
      OWDelay_HybridType1_IP_RFC9951_Seconds_Min>

   URI:
      <https://www.iana.org/assignments/performance-metrics/
      OWDelay_HybridType1_IP_RFC9951_Seconds_Max>

   URI:
      <https://www.iana.org/assignments/performance-metrics/
      OWDelay_HybridType1_IP_RFC9951_Seconds_Sum>

4.1.2.  Description

   OWDelay_HybridType1_IP_RFC9951_Seconds_Mean:
      This metric assesses the mean of one-way delays of all
      successfully forwarded IP packets constituting a single Flow.  The
      measurement of one-way delay is based on a single Observation
      Point [RFC7011] somewhere in the network.

   OWDelay_HybridType1_IP_RFC9951_Seconds_Min:
      This metric assesses the minimum of one-way delays of all
      successfully forwarded IP packets constituting a single Flow.  The
      measurement of one-way delay is based on a single Observation
      Point [RFC7011] somewhere in the network.

   OWDelay_HybridType1_IP_RFC9951_Seconds_Max:
      This metric assesses the maximum of one-way delays of all
      successfully forwarded IP packets constituting a single Flow.  The
      measurement of one-way delay is based on a single Observation
      Point [RFC7011] somewhere in the network.

   OWDelay_HybridType1_IP_RFC9951_Seconds_Sum:
      This metric assesses the sum of one-way delays of all successfully
      forwarded IP packets constituting a single Flow.  The measurement
      of one-way delay is based on a single Observation Point [RFC7011]
      somewhere in the network.

4.1.3.  Reference

   RFC 9951

4.1.4.  Change Controller

   IETF

4.1.5.  Version of Registry Format

   1.0

4.2.  Metric Definition

   This category includes columns to prompt the entry of all necessary
   details related to the metric definition, including the immutable
   document reference and values of input factors, called "Fixed
   Parameters".

4.2.1.  Reference Definition

   See [RFC6049] and [RFC7679] in the Normative References
   (Section 9.1).

   Section 3.4 of [RFC7679] provides the reference definition of the
   singleton (single value) one-way delay metric.  Section 4.4 of
   [RFC7679] provides the reference definition expanded to cover a
   multi-value sample.  Note that terms such as "singleton" and "sample"
   are defined in Section 11 of [RFC2330].

   With the Observation Point [RFC7011] typically located between the
   hosts participating in the IP Flow, the one-way delay metric requires
   one individual measurement between the Observation Point and sourcing
   host, such that the Spatial Composition [RFC6049] of the measurements
   yields a one-way delay singleton.

   This document specifies how to export the performance metric using
   IPFIX.

4.2.2.  Fixed Parameters

   None

4.3.  Method of Measurement

   This category includes columns for references to relevant sections of
   the RFC(s) and any supplemental information needed to ensure an
   unambiguous method for implementations.

4.3.1.  Reference Methods

   The foundational methodology for this metric is defined in Section 4
   of [RFC7323] using the Timestamps option with modifications that
   allow application at a mid-path Observation Point [RFC7011].

4.3.2.  Packet Stream Generation

   This is the time when the packet is being received at the OAM header
   encapsulating node.  The timestamp format depends on the On-Path
   Telemetry implementation.  For IOAM, Section 4.4.1 of [RFC9197]
   describes the supported timestamps.  Sections 4.4.2.3 and 4.4.2.4 of
   [RFC9197] describe where the timestamp is being inserted.  For the
   Enhanced Alternate Marking Method, Section 2 of [ENH-ALT-MARKING] and
   Section 3.2 of [RFC9947] define the supported timestamp encodings and
   granularity.

4.3.3.  Traffic Filtering (Observation) Details

   Runtime Parameters (in the following sections) may be used for
   Traffic Filtering.

4.3.4.  Sampling Distribution

   This metric requires a partial sample of all packets that qualify
   according to the Traffic Filter criteria.

4.3.5.  Runtime Parameters and Data Format

   Runtime Parameters are input factors that must be determined,
   configured into a measurement system, and reported with the results
   for the context to be complete.

   The Hybrid Type I metering parameters must be reported to provide the
   complete measurement context.  As an example, if the IPFIX Metering
   Process is used, then the IPFIX Metering Process parameters (IPFIX
   Template Record, potential traffic filters, and potential sampling
   method and parameters) that generate the Flow Records must be
   reported to provide the complete measurement context.  At a minimum,
   the following fields are required:

   Src:  The IP address of the host in the host A Role (format ipv4-
      address-no-zone value for IPv4 or ipv6-address-no-zone value for
      IPv6; see Section 4 of [RFC9911]).

   Dst:  The IP address of the host in the host B Role (format ipv4-
      address-no-zone value for IPv4 or ipv6-address-no-zone value for
      IPv6; see Section 4 of [RFC9911]).

   T0:  T time, the start of a measurement interval (format "date/time"
      as specified in Section 5.6 of [RFC3339]; see also "date-and-time"
      in Section 3 of [RFC9911]).  The UTC Time Zone is required by
      Section 6.1 of [RFC2330].  When T0 is "all-zeros", a start time is
      unspecified, and Tf is to be interpreted as the duration of the
      measurement interval.  The start time is controlled through other
      means.

   Tf:  A time, the end of a measurement interval (format "date/time" as
      specified in Section 5.6 of [RFC3339]; see also "date-and-time" in
      Section 3 of [RFC9911]).  The UTC Time Zone is required by
      Section 6.1 of [RFC2330].  When T0 is "all-zeros", an ending time
      and date are ignored, and Tf is interpreted as the duration of the
      measurement interval.

4.3.6.  Roles

   Host A:  Launches an IP packet to start the Flow.

   Host B:  Receives the IP packet to start the Flow.

   OAM Header Encapsulating Node:  Receives the IP packets, encapsulates
      the packets with the OAM header, and adds the timestamp into the
      OAM header.

   OAM Header Transit Node:  Receives the IP packets, measures the delay
      between the timestamp in the packet and the timestamp when the
      packet was received.

   OAM Header Decapsulating Node:  Receives the IP packets, computes the
      delay between the timestamp in the packet and the timestamp when
      the packet was received, and removes the OAM header from the
      packet.

4.4.  Output

   This category specifies all details of the output of measurements
   using the metric.

4.4.1.  Type

   OWDelay Types are discussed in the subsections below.

4.4.2.  Reference Definition

   For all output types:

   OWDelay_HybridType1_IP:  The one-way delay of one IP packet is a
      singleton.

   For each <statistic> singleton, one of the following subsections
   applies.

4.4.2.1.  OWDelay_HybridType1_IP_RFC9951_Seconds_Mean

   Similar to Section 7.4.2.2 of [RFC8912], the mean SHALL be calculated
   using the conditional distribution of all packets with a finite value
   of one-way delay (undefined delays are excluded) -- a single value,
   as follows:

   See Section 4.1 of [RFC3393] for details on the conditional
   distribution to exclude undefined values of delay, and see Section 5
   of [RFC6703] for background on this analytic choice.

   See Section 4.2.2 of [RFC6049] for details on calculating this
   statistic; see also Section 4.2.3 of [RFC6049].

   Mean:  The time value of the result is expressed in units of
      microseconds, as a positive value of type decimal64 with fraction
      digits = 9 (similar to decimal64 in YANG, Section 9.3 of
      [RFC6020]) with a resolution of 0.001 microseconds (1.0 ns), and
      with lossless conversion to/from the 64-bit NTP timestamp as per
      Section 6 of [RFC5905].

4.4.2.2.  OWDelay_HybridType1_IP_RFC9951_Seconds_Min

   Similar to Section 7.4.2.3 of [RFC8912], the minimum SHALL be
   calculated using the conditional distribution of all packets with a
   finite value of one-way delay (undefined delays are excluded) -- a
   single value, as follows:

   See Section 4.1 of [RFC3393] for details on the conditional
   distribution to exclude undefined values of delay, and see Section 5
   of [RFC6703] for background on this analytic choice.

   See Section 4.3.2 of [RFC6049] for details on calculating this
   statistic; see also Section 4.3.3 of [RFC6049].

   Min:  The time value of the result is expressed in units of
      microseconds, as a positive value of type decimal64 with fraction
      digits = 9 (similar to decimal64 in YANG, Section 9.3 of
      [RFC6020]) with a resolution of 0.001 microseconds (1.0 ns), and
      with lossless conversion to/from the 64-bit NTP timestamp as per
      Section 6 of [RFC5905].

4.4.2.3.  OWDelay_HybridType1_IP_RFC9951_Seconds_Max

   Similar to Section 7.4.2.4 of [RFC8912], the maximum SHALL be
   calculated using the conditional distribution of all packets with a
   finite value of one-way delay (undefined delays are excluded) -- a
   single value, as follows:

   See Section 4.1 of [RFC3393] for details on the conditional
   distribution to exclude undefined values of delay, and see Section 5
   of [RFC6703] for background on this analytic choice.

   See Section 4.3.2 of [RFC6049] for a closely related method for
   calculating this statistic; see also Section 4.3.3 of [RFC6049].  The
   formula is as follows:

    Max = (FiniteDelay[j])
    such that for some index, j, where 1 <= j <= N
    FiniteDelay[j] >= FiniteDelay[n] for all n

   where all packets n = 1 through N have finite singleton delays.

   Max:  The time value of the result is expressed in units of
      microseconds, as a positive value of type decimal64 with fraction
      digits = 9 (similar to decimal64 in YANG, Section 9.3 of
      [RFC6020]) with a resolution of 0.001 microseconds (1.0 ns), and
      with lossless conversion to/from the 64-bit NTP timestamp as per
      Section 6 of [RFC5905].

4.4.2.4.  OWDelay_HybridType1_IP_RFC9951_Seconds_Sum

   The sum SHALL be calculated using the conditional distribution of all
   packets with a finite value of one-way delay (undefined delays are
   excluded) -- a single value, as follows:

   See Section 4.1 of [RFC3393] for details on the conditional
   distribution to exclude undefined values of delay, and see Section 5
   of [RFC6703] for background on this analytic choice.

   See Section 4.3.5 of [RFC6049] for details on calculating this
   statistic; however, in this case, FiniteDelay or MaxDelay MAY be
   used.

   Sum:  The time value of the result is expressed in units of
      microseconds, as a positive value of type decimal64 with fraction
      digits = 9 (similar to decimal64 in YANG, Section 9.3 of
      [RFC6020]) with a resolution of 0.001 microseconds (1.0 ns), and
      with lossless conversion to/from the 64-bit NTP timestamp as per
      Section 6 of [RFC5905].

4.4.2.5.  Metric Units

   *  Mean

   *  Min

   *  Max

   *  Sum

   The one-way delay of the IP Flow singleton is expressed in
   microseconds.

4.4.2.6.  Calibration

   A clock synchronization between the nodes of the monitored OAM domain
   is needed to compute representative delay measurements at the OAM
   header transit and decapsulating nodes.  NTP, as defined in
   [RFC5905], can be used for synchronizing the clocks of the monitored
   nodes.

4.4.3.  Administrative Items

4.4.3.1.  Status

   Current

4.4.3.2.  Requester

   RFC 9951

4.4.3.3.  Revision

   1.0

4.4.3.4.  Revision Date

   2026-04-02

4.4.4.  Comments and Remarks

   None

5.  Use Cases

   The measured On-Path delay can be aggregated with Flow Aggregation as
   defined in [RFC7015] across the following device and control-plane
   dimensions [IANA-IPFIX] to determine:

   *  With node id and egressInterface(14), on which node which logical
      egress interfaces have been contributing to how much delay.

   *  With node id and egressPhysicalInterface(253), on which node which
      physical egress interfaces have been contributing to how much
      delay.

   *  With ipNextHopIPv4Address(15) or ipNextHopIPv6Address(62), the
      forwarding path to which next-hop IP contributed to how much
      delay.

   *  With mplsTopLabelIPv4Address(47) or destinationIPv6Address and
      srhActiveSegmentIPv6(495), the forwarding path to which MPLS top-
      label IPv4 address or IPv6 destination address and Segment Routing
      over IPv6 (SRv6) active segment contributed to how much delay.

   *  BGP communities [RFC1997] are often used for setting a path
      priority or service selection.  With
      bgpDestinationExtendedCommunityList(488) or
      bgpDestinationCommunityList(485) or
      bgpDestinationLargeCommunityList(491), which group of prefixes
      accumulated at which node how much delay.

   *  With destinationIPv4Address(13), destinationTransportPort(11),
      protocolIdentifier(4), and sourceIPv4Address(8), or equivalent
      IPFIX IEs for IPv6, the forwarding path delay on each node from
      each IPv4 source address to a specific application in the network.

   Let us consider Figure 1 as a topology example.  Table 2 shows the
   aggregated delay per each node, ingressInterface(10),
   egressInterface(14), destinationIPv6Address(28), and
   srhActiveSegmentIPv6(495) measured at ingress.

   +===========+===========+======+=============+=============+=======+
   | ingress   | egress    | Node | destination | srhActive   | Path  |
   | Interface | Interface |      | IPv6Address | SegmentIPv6 | Delay |
   +===========+===========+======+=============+=============+=======+
   | 271       | 276       | R0   |             |             | 0 µs  |
   +-----------+-----------+------+-------------+-------------+-------+
   | 301       | 312       | R1   | 2001:db8::1 | 2001:db8::3 | 22 µs |
   +-----------+-----------+------+-------------+-------------+-------+
   | 22        | 27        | R2   | 2001:db8::2 | 2001:db8::3 | 42 µs |
   +-----------+-----------+------+-------------+-------------+-------+
   | 852       | 854       | R3   | 2001:db8::3 | 2001:db8::3 | 122   |
   |           |           |      |             |             | µs    |
   +-----------+-----------+------+-------------+-------------+-------+

      Table 2: Example Table of Measured Delay at Ingress, Ascending
                                 by Delay

6.  IANA Considerations

6.1.  Performance Metrics

   IANA has add four new performance metrics in the "Performance Metrics
   Registry" [RFC8911] with the four templates defined in Section 3.

6.2.  IPFIX Entities

   IANA has registered new IPFIX IEs (see Table 3) in the "IPFIX
   Information Elements" registry in the "IP Flow Information Export
   (IPFIX) Entities" registry group [IANA-IPFIX] and assigned the
   following code points.

              +===========+================================+
              | ElementID | Name                           |
              +===========+================================+
              | 530       | pathDelayMeanDeltaMicroseconds |
              +-----------+--------------------------------+
              | 531       | pathDelayMinDeltaMicroseconds  |
              +-----------+--------------------------------+
              | 532       | pathDelayMaxDeltaMicroseconds  |
              +-----------+--------------------------------+
              | 533       | pathDelaySumDeltaMicroseconds  |
              +-----------+--------------------------------+

                   Table 3: New IPFIX IEs in the "IPFIX
                      Information Elements" Registry

6.2.1.  pathDelayMeanDeltaMicroseconds

   Name:  pathDelayMeanDeltaMicroseconds

   ElementID:  530

   Description:  This Information Element identifies the mean path delay
      of all packets in the Flow, in microseconds, between an OAM header
      encapsulating node and the local node with the OAM domain (either
      an OAM header transit node or an OAM header decapsulating node),
      according to OWDelay_HybridType1_IP_RFC9951_Seconds_Mean in the
      IANA "Performance Metrics Registry".

   Abstract Data Type:  unsigned32

   Data Type Semantics:  deltaCounter

   Reference:  RFC 9951

   Additional Information:  OWDelay_HybridType1_IP_RFC9951_Seconds_Mean
      in the IANA "Performance Metrics Registry".

6.2.2.  pathDelayMinDeltaMicroseconds

   Name:  pathDelayMinDeltaMicroseconds

   ElementID:  531

   Description:  This Information Element identifies the lowest path
      delay of all packets in the Flow, in microseconds, between an OAM
      header encapsulating node and the local node with the OAM domain
      (either an OAM header transit node or an OAM header decapsulating
      node), according to the OWDelay_HybridType1_IP_RFC9951_Seconds_Min
      in the IANA "Performance Metrics Registry".

   Abstract Data Type:  unsigned32

   Data Type Semantics:  deltaCounter

   Reference:  RFC 9951

   Additional Information:  OWDelay_HybridType1_IP_RFC9951_Seconds_Min
      in the IANA "Performance Metrics Registry".

6.2.3.  pathDelayMaxDeltaMicroseconds

   Name:  pathDelayMaxDeltaMicroseconds

   ElementID:  532

   Description:  This Information Element identifies the highest path
      delay of all packets in the Flow, in microseconds, between an OAM
      header encapsulating node and the local node with the OAM domain
      (either an OAM header transit node or an OAM header decapsulating
      node), according to OWDelay_HybridType1_IP_RFC9951_Seconds_Max in
      the IANA "Performance Metrics Registry".

   Abstract Data Type:  unsigned32

   Data Type Semantics:  deltaCounter

   Reference:  RFC 9951

   Additional Information:  OWDelay_HybridType1_IP_RFC9951_Seconds_Max
      in the IANA "Performance Metrics Registry".

6.2.4.  pathDelaySumDeltaMicroseconds

   Name:  pathDelaySumDeltaMicroseconds

   ElementID:  533

   Description:  This Information Element identifies the sum of the path
      delay of all packets in the Flow, in microseconds, between an OAM
      header encapsulating node and the local node with the OAM domain
      (either an OAM header transit node or an OAM header decapsulating
      node), according to OWDelay_HybridType1_IP_RFC9951_Seconds_Sum in
      the IANA "Performance Metrics Registry".

   Abstract Data Type:  unsigned64

   Data Type Semantics:  deltaCounter

   Reference:  RFC 9951

   Additional Information:  OWDelay_HybridType1_IP_RFC9951_Seconds_Sum
      in the IANA "Performance Metrics Registry".

7.  Operational Considerations

7.1.  Time Accuracy

   In terms of clock precision, the same recommendation as defined in
   Section 4.5 of [RFC5153] for IPFIX applies to this document as well.

7.2.  Mean Delay

   The mean (average) path delay can be calculated by dividing the
   pathDelaySumDeltaMicroseconds(533) by the packetDeltaCount(2) at the
   IPFIX data collection at the collection time instead of the IPFIX
   Exporter at the export time.

7.3.  Reduced-Size Encoding

   Unsigned64 has been chosen as the type for
   pathDelaySumDeltaMicroseconds to support cases with large delay
   numbers and where many packets are being counted.  As an example, a
   specific Flow Record with path delay of 100 milliseconds cannot
   observe more than 42949 packets without overflowing the unsigned32
   counter.  The procedure described in Section 6.2 of [RFC7011] may be
   applied to reduce network bandwidth between the IPFIX Exporter and
   Collector if unsigned32 would be large enough without wrapping
   around.

7.4.  Measurement Interval

   The delay metrics are computed for the Flow Record lifetime by
   comparing the OAM timestamps in each received packet with the
   timestamp when they were received.  For a long-running Flow, the
   IPFIX Metering Process might miss the temporal distribution of the
   delay (for example, a longer delay only at the beginning of the
   Flow).  If this is an operational problem, the IPFIX Metering Process
   might be configured with a smaller expiration timeout (see "Flow
   Expiration", Section 5.1.1 of [RFC5470]).

7.5.  In-Packet OAM Application

   Multiple methods can be used to compute the delay performance metrics
   defined in this document.  Some examples of such methods are IOAM
   [RFC9197] and Enhanced Alternate Marking [ENH-ALT-MARKING].

   For IOAM, these performance metrics can be computed using the Edge-
   to-Edge and the Direct Exporting Option-Type.

   IOAM Edge-to-Edge Option-Type, as described in Section 4.6 of
   [RFC9197], can use bits 2 and 3.  In this case, timestamps are
   encoded as defined in Sections 4.4.2.3 and 4.4.2.4 of [RFC9197].
   This timestamp can be used to compute the delay between an OAM header
   encapsulating node and the decapsulating node.

   The IOAM Direct Exporting Option-Type, as described in [RFC9326], can
   use the Extension-Flag defined in [IOAM-DEX] to insert a timestamp in
   the OAM header encapsulating node.  The timestamp is encoded as
   defined in Sections 4.4.2.3 and 4.4.2.4 of [RFC9197].  This timestamp
   can be used to compute the delay between the inserted timestamp and
   the OAM header transit and decapsulating node.

   For the Enhanced Alternate Marking Method, Section 2 of
   [ENH-ALT-MARKING] and Section 3.2 of [RFC9947] define that, within
   the metaInfo, a nanosecond timestamp can be encoded in an OAM header
   encapsulating node and be read at the OAM header intermediate and
   decapsulating nodes to calculate the On-path delay.  [RFC9343]
   defines how this can be applied to the IPv6 extensions header, and
   [RFC9947] defines how this can be applied to the SRv6 Segment Routing
   Header [RFC8754].

   Given that the delay measurements are computed with the timestamp
   introduced on the OAM header encapsulating node, regardless of the
   approach, implementations should document at which point of the
   forwarding plane this timestamp is introduced (e.g., the time at
   which the packet was received by the node, the time at which the
   packet was transmitted by the node, etc.).  Based on this
   information, different actions can be taken.

8.  Security Considerations

   The IPFIX Information Elements introduced in this document do not
   directly introduce security issues.  Rather, they define a set of
   performance metrics that may, for privacy or business issues, be
   considered sensitive information.

   For example, exporting delay metrics may make attacks possible by the
   receiver of this information; otherwise, this would only be possible
   for direct observers of the reported Flows along the data path.

   IPFIX collectors MUST ensure that IPFIX data originates from trusted
   sources.  Accepting IPFIX data from unauthenticated sources could
   lead to data spoofing, policy misapplication, or denial of service.

   Therefore, the underlying protocol used to exchange the information
   described here must apply appropriate procedures to guarantee the
   integrity and confidentiality of the exported information.  These
   protocols are defined in separate documents; specifically, see the
   IPFIX security considerations in Section 11 of [RFC7011].
   Implementations SHOULD also refer to [BCP195] for additional details.

9.  References

9.1.  Normative References

   [BCP195]   Best Current Practice 195,
              <https://www.rfc-editor.org/info/bcp195>.
              At the time of writing, this BCP comprises the following:

              Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
              <https://www.rfc-editor.org/info/rfc8996>.

              Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/info/rfc9325>.

   [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>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
              <https://www.rfc-editor.org/info/rfc5905>.

   [RFC6049]  Morton, A. and E. Stephan, "Spatial Composition of
              Metrics", RFC 6049, DOI 10.17487/RFC6049, January 2011,
              <https://www.rfc-editor.org/info/rfc6049>.

   [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>.

   [RFC7323]  Borman, D., Braden, B., Jacobson, V., and R.
              Scheffenegger, Ed., "TCP Extensions for High Performance",
              RFC 7323, DOI 10.17487/RFC7323, September 2014,
              <https://www.rfc-editor.org/info/rfc7323>.

   [RFC7679]  Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
              Ed., "A One-Way Delay Metric for IP Performance Metrics
              (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
              2016, <https://www.rfc-editor.org/info/rfc7679>.

   [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>.

   [RFC8911]  Bagnulo, M., Claise, B., Eardley, P., Morton, A., and A.
              Akhter, "Registry for Performance Metrics", RFC 8911,
              DOI 10.17487/RFC8911, November 2021,
              <https://www.rfc-editor.org/info/rfc8911>.

   [RFC8912]  Morton, A., Bagnulo, M., Eardley, P., and K. D'Souza,
              "Initial Performance Metrics Registry Entries", RFC 8912,
              DOI 10.17487/RFC8912, November 2021,
              <https://www.rfc-editor.org/info/rfc8912>.

9.2.  Informative References

   [ENH-ALT-MARKING]
              Zhou, T., Ed., Fioccola, G., Liu, Y., Cociglio, M., Pang,
              R., Xiong, L., Lee, S., and W. Li, "Enhanced Alternate
              Marking Method", Work in Progress, Internet-Draft, draft-
              zhou-ippm-enhanced-alternate-marking-18, 5 December 2025,
              <https://datatracker.ietf.org/doc/html/draft-zhou-ippm-
              enhanced-alternate-marking-18>.

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

   [IANA-PERF-METRIC]
              IANA, "Performance Metrics",
              <https://www.iana.org/assignments/performance-metrics>.

   [IOAM-DEX] Huang Feng, A., Francois, P., Claise, B., and T. Graf,
              "Timestamp extension for In Situ Operations,
              Administration, and Maintenance (IOAM) Direct Export",
              Work in Progress, Internet-Draft, draft-ahuang-ippm-dex-
              timestamp-ext-00, 15 February 2023,
              <https://datatracker.ietf.org/doc/html/draft-ahuang-ippm-
              dex-timestamp-ext-00>.

   [IPFIX-ALT-MARK]
              Graf, T., Fioccola, G., Zhou, T., and Y. Zhu, "IP Flow
              Information Export (IPFIX) Alternate-Marking Information
              Elements", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-ipfix-alt-mark-05, 27 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ipfix-alt-mark-05>.

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
              <https://www.rfc-editor.org/info/rfc1997>.

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              DOI 10.17487/RFC2330, May 1998,
              <https://www.rfc-editor.org/info/rfc2330>.

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              DOI 10.17487/RFC3393, November 2002,
              <https://www.rfc-editor.org/info/rfc3393>.

   [RFC5153]  Boschi, E., Mark, L., Quittek, J., Stiemerling, M., and P.
              Aitken, "IP Flow Information Export (IPFIX) Implementation
              Guidelines", RFC 5153, DOI 10.17487/RFC5153, April 2008,
              <https://www.rfc-editor.org/info/rfc5153>.

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", RFC 5470,
              DOI 10.17487/RFC5470, March 2009,
              <https://www.rfc-editor.org/info/rfc5470>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6703]  Morton, A., Ramachandran, G., and G. Maguluri, "Reporting
              IP Network Performance Metrics: Different Points of View",
              RFC 6703, DOI 10.17487/RFC6703, August 2012,
              <https://www.rfc-editor.org/info/rfc6703>.

   [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>.

   [RFC7799]  Morton, A., "Active and Passive Metrics and Methods (with
              Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
              May 2016, <https://www.rfc-editor.org/info/rfc7799>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

   [RFC9197]  Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
              Ed., "Data Fields for In Situ Operations, Administration,
              and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
              May 2022, <https://www.rfc-editor.org/info/rfc9197>.

   [RFC9232]  Song, H., Qin, F., Martinez-Julia, P., Ciavaglia, L., and
              A. Wang, "Network Telemetry Framework", RFC 9232,
              DOI 10.17487/RFC9232, May 2022,
              <https://www.rfc-editor.org/info/rfc9232>.

   [RFC9326]  Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
              Mizrahi, "In Situ Operations, Administration, and
              Maintenance (IOAM) Direct Exporting", RFC 9326,
              DOI 10.17487/RFC9326, November 2022,
              <https://www.rfc-editor.org/info/rfc9326>.

   [RFC9343]  Fioccola, G., Zhou, T., Cociglio, M., Qin, F., and R.
              Pang, "IPv6 Application of the Alternate-Marking Method",
              RFC 9343, DOI 10.17487/RFC9343, December 2022,
              <https://www.rfc-editor.org/info/rfc9343>.

   [RFC9911]  Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911,
              DOI 10.17487/RFC9911, December 2025,
              <https://www.rfc-editor.org/info/rfc9911>.

   [RFC9947]  Fioccola, G., Zhou, T., Mishra, G., Wang, X., Zhang, G.,
              and M. Cociglio, "Application of the Alternate-Marking
              Method to the Segment Routing Header", RFC 9947,
              DOI 10.17487/RFC9947, March 2026,
              <https://www.rfc-editor.org/info/rfc9947>.

Appendix A.  IPFIX Encoding Examples

   This appendix represents two different encodings for the newly
   introduced IEs.  Let's take Figure 1 as a topology example.  Table 4
   shows the aggregated delay with ingressInterface, egressInterface,
   destinationIPv6Address, and srhActiveSegmentIPv6.

             +--------------------------------+-------------+
             | ingressInterface               | 271         |
             +--------------------------------+-------------+
             | egressInterface                | 276         |
             +--------------------------------+-------------+
             | destinationIPv6Address         | 2001:db8::3 |
             +--------------------------------+-------------+
             | srhActiveSegmentIPv6           | 2001:db8::2 |
             +--------------------------------+-------------+
             | packetDeltaCount               | 5           |
             +--------------------------------+-------------+
             | pathDelayMeanDeltaMicroseconds | 36 µs       |
             +--------------------------------+-------------+
             | pathDelayMinDeltaMicroseconds  | 22 µs       |
             +--------------------------------+-------------+
             | pathDelayMaxDeltaMicroseconds  | 74 µs       |
             +--------------------------------+-------------+

                      Table 4: Aggregated Delay with
                 egressInterface and srhActiveSegmentIPv6

A.1.  Aggregated On-Path Delay Examples

A.1.1.  Template Record and Data Set with Mean Delta

   With encoding in Figure 2, the mean (average) path delay is
   calculated on the exporting node.

   *  Ingress interface => ingressInterface

   *  Egress interface => egressInterface

   *  IPv6 destination address => destinationIPv6Address

   *  Active SRv6 Segment => srhActiveSegmentIPv6

   *  Packet Delta Count => packetDeltaCount

   *  Minimum One-Way Delay => pathDelayMinDeltaMicroseconds (531)

   *  Maximum One-Way Delay => pathDelayMaxDeltaMicroseconds (532)

   *  Mean One-Way Delay => pathDelayMeanDeltaMicroseconds (530)

    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|     ingressInterface = 10   |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|     egressInterface = 14    |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| destinationIPv6Address = 28 |      Field Length = 16        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| srhActiveSegmentIPv6 = 495  |      Field Length = 16        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| packetDeltaCount = 5        |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| pathDelayMeanDelta.. = 530  |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| pathDelayMinDelta.. = 531   |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| pathDelayMaxDelta.. = 532   |      Field Length = 4         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 2: Template Record for pathDelayMeanDeltaMicroseconds

   The data set is represented as follows:

    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 = 60         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           ingressInterface =  271                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           egressInterface =  276                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           destinationIPv6Address =                            |
   |                          ...                                  |
   |                          ...                                  |
   |                          2001:db8::2                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           srhActiveSegmentIPv6 = ...                          |
   |                          ...                                  |
   |                          ...                                  |
   |                          2001:db8::3                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           packetDeltaCount = 5                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           pathDelayMeanDeltaMicroseconds =  36                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           pathDelayMinDeltaMicroseconds =  22                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           pathDelayMaxDeltaMicroseconds =  74                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 3: Data Set Encoding for pathDelayMeanDeltaMicroseconds

A.1.2.  Template Record and Data Set with Sum Delta

   With encoding in Figure 4, the mean (average) path delay is
   calculated on the IPFIX data collection.

   *  Ingress interface => ingressInterface

   *  Egress interface => egressInterface

   *  IPv6 destination address => destinationIPv6Address

   *  Active SRv6 Segment => srhActiveSegmentIPv6

   *  Packet Delta Count => packetDeltaCount

   *  Minimum One-Way Delay => pathDelayMinDeltaMicroseconds (531)

   *  Maximum One-Way Delay => pathDelayMaxDeltaMicroseconds (532)

   *  Sum of One-Way Delay => pathDelaySumDeltaMicroseconds (533)

       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 = 257        |      Field Count = 8          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|     ingressInterface = 10   |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|     egressInterface = 14    |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| destinationIPv6Address = 28 |      Field Length = 16        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| srhActiveSegmentIPv6 = 495  |      Field Length = 16        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| packetDeltaCount = 5        |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| pathDelayMinDelta.. = 531   |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| pathDelayMaxDelta.. = 532   |      Field Length = 4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0| pathDelaySumDelta.. = 533   |      Field Length = 8         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 4: Template Record for pathDelaySumDeltaMicroseconds.

   The data set is represented as follows:

       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 = 257          |           Length = 64         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           ingressInterface =  271                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           egressInterface =  276                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           destinationIPv6Address =                            |
      |                          ...                                  |
      |                          ...                                  |
      |                          2001:db8::2                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           srhActiveSegmentIPv6 = ...                          |
      |                          ...                                  |
      |                          ...                                  |
      |                          2001:db8::3                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           packetDeltaCount = 5                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           pathDelayMinDeltaMicroseconds =  22                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           pathDelayMaxDeltaMicroseconds =  74                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           pathDelaySumDeltaMicroseconds =  180                |
      |                          ...                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 5: Data Set Encoding for pathDelaySumDeltaMicroseconds

Acknowledgements

   The authors would like to thank Al Morton (Rest in Peace, Al), Justin
   Iurman, Giuseppe Fioccola, Yannick Buchs, Menachem Dodge, Martin
   Duke, Behcet Sarikaya, Mahesh Jethanandani, Linda Dunbar, Deb Cooley,
   Mike Bishop, Tim Wicinski, Gunter Van de Velde, and Éric Vyncke for
   their review and valuable comments.  Special thanks to Paul Aitken
   (as IPFIX Designated Expert), Greg Mirsky (as IP Performance Metrics
   Designated Expert), and to Med Boucadair for their very detailed
   feedback.

Authors' Addresses

   Thomas Graf
   Swisscom
   Binzring 17
   CH-8045 Zurich
   Switzerland
   Email: thomas.graf@swisscom.com


   Benoit Claise
   Huawei
   Email: benoit@everything-ops.net


   Alex Huang-Feng
   INSA-Lyon
   Lyon
   France
   Email: alex.huang-feng@insa-lyon.fr
