IETF standardizes four IPFIX delay metrics for on-path telemetry
The Internet Engineering Task Force (IETF) has published RFC 9951 as a Proposed Standard. The document specifies four new IP Flow Information Export (IPFIX) Information Elements designed to export on-path network delay metrics, including mean, minimum, maximum, and sum of delays for a given flow. This standard is intended to help network operators with performance analysis and diagnostics by enabling the aggregation of delay metrics on transit and decapsulating nodes, reducing export bandwidth and processing requirements on collectors.
Key Takeaways
- RFC 9951 is a Proposed Standard from the IETF, last updated 2026-04-24.
- The document defines four IPFIX Information Elements: pathDelayMeanDeltaMicroseconds(530), pathDelayMinDeltaMicroseconds(531), pathDelayMaxDeltaMicroseconds(532), and pathDelaySumDeltaMicroseconds(533).
- The metrics export on-path delay from OAM transit and decapsulating nodes, based on an encapsulating node timestamp.
- The RFC says exporting sum delay lets the collector compute mean delay by dividing by packetDeltaCount(2), reducing work on the exporter.
- The RFC ties the approach to postcard-mode on-path telemetry and examples including IOAM and Enhanced Alternate Marking.
Why It Matters
This gives operators a standardized way to move delay measurement from per-packet export toward aggregated Flow Records. The immediate effect is lower export bandwidth and less collector-side processing when delay is summarized at the transit or decapsulating node. It also aligns on-path telemetry with IPFIX flow aggregation, which matters for environments that want delay data correlated with interfaces, next hops, SRv6 segments, or BGP community-based paths. What to watch: whether implementations expose pathDelaySumDeltaMicroseconds(533) alone or the full mean/min/max set in deployed templates.
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