Multi-Point Telemetry Correlation for Network Measurement
draft-li-ippm-multipoint-telemetry-00

IPPM                                                               Z. Li
Internet-Draft                                                     Z. Du
Intended status: Standards Track                            China Mobile
Expires: 5 January 2027                                          J. Wang
                                                                W. Cheng
                                                                G. Zhang
                                                                  Centec
                                                                  X. Sun
                                                                   Inesa
                                                                 C. Zhao
                                                                    SAIA
                                                             4 July 2026

       Multi-Point Telemetry Correlation for Network Measurement
                 draft-li-ippm-multipoint-telemetry-00

Abstract

   Network measurement and telemetry systems that collect data at
   multiple points along a path or across multiple targets require a
   means to correlate the collected data.  When each collection point
   independently selects which packets to observe, the resulting data
   sets may not overlap, preventing per-packet correlation of
   measurements across points.

   This document specifies how source-directed selection -- where a
   single node determines which packets are subject to measurement and
   signals this to other nodes -- achieves correlated data collection
   across multiple points.  Two applications are described: IOAM Direct
   Export for in-band network telemetry, and PTP Sequence ID range
   assignment for multi-slave time synchronization.

Status of This Memo

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   This Internet-Draft will expire on 5 January 2027.

Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Application to IOAM Direct Export . . . . . . . . . . . . . .   3
     2.1.  Encapsulating Node  . . . . . . . . . . . . . . . . . . .   3
     2.2.  Transit and Decapsulating Nodes . . . . . . . . . . . . .   3
     2.3.  Data Correlation  . . . . . . . . . . . . . . . . . . . .   4
   3.  Application to PTP Multi-Slave Topologies . . . . . . . . . .   4
     3.1.  Sequence ID Range Assignment  . . . . . . . . . . . . . .   4
     3.2.  Grandmaster Timestamp Correlation . . . . . . . . . . . .   4
     3.3.  Slave Processing  . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Distributed network measurement systems collect data at multiple
   points in the network.  In forwarding-plane telemetry systems such as
   IOAM [RFC9197], each node along a packet's path may independently
   export measurement data.  In time synchronization systems such as PTP
   [IEEE-1588], a Grandmaster may serve multiple slaves, generating
   timestamped messages that must be correlated with specific targets.

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   A common challenge in both scenarios is ensuring that data collected
   at different points corresponds to the same set of packets or the
   same target.  When each collection point independently selects
   packets for observation (per [RFC5475]), different points may observe
   different subsets of the same flow, making per-packet path analysis
   impossible.  Similarly, when a time source generates timestamps for
   multiple targets, each timestamp must be associated with the correct
   target.

   This document specifies source-directed selection, in which a single
   node makes the selection or assignment decision and communicates it
   to other nodes via in-band signaling.  Two specific applications are
   described in the following sections.

1.1.  Requirements Language

   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.

2.  Application to IOAM Direct Export

   IOAM Direct Export (DEX) [RFC9326] defines an IOAM Option-Type that
   triggers each transit node to export telemetry data for a packet
   without embedding the data in the packet itself.  The IOAM
   encapsulating node selects which packets carry the DEX option, and
   all downstream nodes export data for those packets.

2.1.  Encapsulating Node

   The IOAM encapsulating node applies a sampling policy (e.g., 1-in-N,
   probabilistic, or hash-based per [RFC5475]) to monitored flows.
   Packets selected by the sampling policy are encapsulated with the DEX
   Option-Type per [RFC9326].  Packets not selected are forwarded
   without the DEX option.  The encapsulating node SHOULD also export
   its own local telemetry data for each DEX-carrying packet.

2.2.  Transit and Decapsulating Nodes

   IOAM transit nodes export local telemetry data for every packet
   carrying the DEX option, per [RFC9326].  Transit nodes MUST NOT apply
   independent sampling decisions to DEX packets; the presence of the
   DEX option is itself the selection indicator.  The IOAM decapsulating
   node exports its local telemetry data and removes the DEX option
   before forwarding the packet beyond the IOAM domain.

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2.3.  Data Correlation

   Because all nodes on the path export data for the same set of
   packets, a collector can reconstruct the per-packet experience at
   each hop.  Telemetry records from different nodes for the same packet
   can be correlated using the flow identifier and a packet-level
   identifier (e.g., a hash of invariant header fields, or a sequence
   number from the transport layer).  The choice of packet-level
   identifier is outside the scope of this document.

3.  Application to PTP Multi-Slave Topologies

   The Precision Time Protocol (PTP) [IEEE-1588] supports time
   synchronization between a Grandmaster and multiple Ordinary Clock
   slaves.  In Two-Step operation, the Grandmaster captures the egress
   timestamp of each Sync message in hardware and communicates it via a
   Follow_Up message.  When the Grandmaster serves multiple slaves using
   multicast Sync messages, the hardware timestamp capture records must
   be correlated with the correct target slave.

3.1.  Sequence ID Range Assignment

   The 16-bit PTP Sequence ID field provides 65,536 values.  When N
   slaves are served by a single Grandmaster, the Sequence ID space can
   be divided into N non-overlapping contiguous ranges, each assigned to
   a specific slave.  The Grandmaster transmits Sync messages for each
   slave using Sequence IDs from that slave's assigned range.  The
   assignment of Sequence ID ranges to slaves MUST be agreed upon by the
   Grandmaster and all slaves before synchronization begins.  The method
   of assignment (e.g., configuration, management protocol) is outside
   the scope of this document.

3.2.  Grandmaster Timestamp Correlation

   In Two-Step mode, the Grandmaster retrieves captured timestamps from
   the hardware and identifies the target slave from the Sequence ID
   recorded with each timestamp.  In One-Step mode, the hardware inserts
   the timestamp directly into each Sync message; the Sequence ID
   identifies the target slave for downstream processing.

3.3.  Slave Processing

   Each slave receives all multicast Sync and Follow_Up messages but
   MUST process only those whose Sequence ID falls within its assigned
   range.  Messages with Sequence IDs outside the assigned range MUST be
   silently discarded.

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4.  Security Considerations

   For the IOAM DEX application, the security considerations of
   [RFC9326] apply.  An attacker that can inject packets with the DEX
   option could cause telemetry export at all IOAM nodes.  IOAM domain
   ingress filtering SHOULD discard DEX options on packets from
   untrusted sources.

   For the PTP application, misconfigured Sequence ID ranges that
   overlap could cause a slave to process timestamps intended for
   another slave.  Implementations SHOULD validate range assignments for
   uniqueness.  PTP authentication (Annex P of [IEEE-1588]) SHOULD be
   used in security-sensitive deployments.

5.  IANA Considerations

   This document has no IANA actions.

6.  Normative References

   [IEEE-1588]
              IEEE, "IEEE Standard for a Precision Clock Synchronization
              Protocol for Networked Measurement and Control Systems",
              IEEE 1588-2019, 2019.

   [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>.

   [RFC5475]  Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
              Raspall, "Sampling and Filtering Techniques for IP Packet
              Selection", RFC 5475, DOI 10.17487/RFC5475, March 2009,
              <https://www.rfc-editor.org/info/rfc5475>.

   [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>.

   [RFC9197]  Brockners, F., Bhandari, S., and T. Mizrahi, "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>.

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

Authors' Addresses

   Zhiqiang Li
   China Mobile
   Beijing
   100053
   China
   Email: lizhiqiangyjy@chinamobile.com

   Zongpeng Du
   China Mobile
   Beijing
   100053
   China
   Email: duzongpeng@chinamobile.com

   Junjie Wang
   Centec
   Shanghai
   201203
   China
   Email: wangjj@centec.com

   Wei Cheng
   Centec
   Shanghai
   201203
   China
   Email: chengw@centec.com

   Guoying Zhang
   Centec
   Shanghai
   201203
   China
   Email: zhanggy@centec.com

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   Xun Sun
   Inesa
   Shanghai
   200030
   China
   Email: sunxun@inesa.com

   Chunhao Zhao
   SAIA
   Shanghai
   200125
   China
   Email: chunhao.zhao@sh-aia.com

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