[GROW] Re: Mail regarding draft-ietf-grow-bmp-stats-informational-tlv

["Srivastava, Mukul" <[e-mail]>]

Hello Shunwan

Thanks for your detail review and valuable feedback.

I agree that the temporal context of aggregate statistics is important. The next revision can add field, for example a measurement window duration field to the Statistics Information TLV header. This will allow a collector to determine the duration over which the aggregate values carried in the TLV were calculated.

I also agree to use the RFC 7854 timestamp format to keep things consistent. We also plan to implement P5 and P95 entry types, which might help to detect the network anomalies.

We will create a operational consideration section in the draft to clarify that the reported values are local significance. These values are derived from implementation specific collections methods and sample populations.

I don’t think we should use this draft to export the configuration and algorithms. I am assuming collector will have other channels to collect this information from a router. Also note that specifying the algorithm name is not enough. Different vendor can implement same algorithm with different parameters resulting in different values with same algorithm.

Thanks
Mukul


From: Zhuangshunwan <zhuangshunwan=[e-mail]>
Date: Thursday, August 13, 2026 at 8:33 PM
To: Srivastava, Mukul <[e-mail]>
Cc: [e-mail] <[e-mail]>; [e-mail] <[e-mail]>
Subject: RE: Mail regarding draft-ietf-grow-bmp-stats-informational-tlv


Hi Mukul,

Thanks for the positive feedback! It’s great to hear that you will consider adding higher percentiles in the next revision.
I completely agree with your point regarding P95 vs. P99 and the need to balance computation overhead with operational value. Focusing on P95 strikes the right balance—it effectively captures tail latencies and anomalous spikes without being overly sensitive to extreme 1% outliers.

Additionally, after reviewing the draft further, I'd like to share a few complementary observations regarding the current design for the WG and authors to consider:
1. Missing Time Window / Sampling Interval Context
Currently, the draft defines metrics like Max, Min, and Median (P50), but it does not specify the time window over which these statistics were calculated (e.g., is P50 computed over the last 5 seconds, 15 minutes, or since session reset?). Furthermore, sampling intervals are undefined.

  *   Risk: If the export frequency varies or is dynamically triggered, the BMP Collector/Server cannot accurately interpret these values. A "Max" over 5 seconds has a drastically different operational meaning for capacity planning than a "Max" over 1 hour. Adding an optional Measurement Window Duration / Sampling Interval TLV would resolve this ambiguity.
2. Timestamp Precision Alignment (Seconds vs. Sub-seconds)
The current draft uses a 4-byte timestamp (second precision). Modern routing anomalies (e.g., BGP hijacking, rapid route leaks, or micro-bursts) and CPU/Queue spikes often occur at the millisecond or microsecond scale.

  *   Risk: 4-byte timestamps create a discrepancy with the standard 8-byte sub-second precision used in RFC 7854. More importantly, it introduces potential causality inversion—collectors may be unable to determine whether a CPU load spike preceded or followed a sudden burst of route updates. Aligning with sub-second timestamps would significantly enhance event correlation.
3. Lack of Standardization for Percentile Estimation Algorithms
The computation methodology for metrics like Median (P50) and P95 is currently a "black box." Different vendors (e.g., Cisco, Juniper, HPE, Huawei) may implement different estimation techniques (e.g., streaming algorithms like T-Digest, fixed-window sampling, or simplified binning/histogram methods).

  *   Risk: Heterogeneous calculation baselines across multi-vendor networks make cross-vendor telemetry aggregation and comparison unreliable for operators. It might be beneficial for the draft to either specify a recommended default algorithm or allow the router to signal the estimation method used in the metadata.
Regarding the router overhead you mentioned, these concerns could be addressed in the Operational Considerations section by making high percentiles optional/configurable, and recommending lightweight streaming estimation techniques (e.g., T-Digest or HdrHistogram) that require minimal memory and CPU footprints.

Looking forward to hearing your and the WG's thoughts on these points!

Best regards,
Shunwan


From: Srivastava, Mukul <mukul.srivastava=[e-mail]>
Sent: Thursday, August 13, 2026 10:09 PM
To: Zhuangshunwan <[e-mail]>
Cc: [e-mail]; [e-mail]
Subject: Re: Mail regarding draft-ietf-grow-bmp-stats-informational-tlv

Hi Shunwan

Thanks for the review and comment.

We will explore this and update the draft to add higher percentiles in next version.
I am more inclined to keep P95 than P99 (which is almost 100%).

Note that maintaining/exporting these multiple percentiles stats might be an overhead at router. So we should maintain a balance between overhead and the value that it provides.

Thanks
Mukul

From: Zhuangshunwan <zhuangshunwan=[e-mail]<mailto:zhuangshunwan=[e-mail]>>
Date: Tuesday, August 11, 2026 at 2:27 AM
To: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Subject: [GROW] Mail regarding draft-ietf-grow-bmp-stats-informational-tlv
Hi Authors and GROW WG,

Thanks for introducing draft-ietf-grow-bmp-stats-informational-tlv-00. Moving to a flexible TLV structure for BMP Statistics is a very welcomed step.

I noticed that the draft currently introduces Median (P50) for statistical metrics. I would like to suggest exploring the addition of higher percentiles, such as P75, P95, or P99.

In operational telemetry (e.g., routing convergence time, processing latency, or queueing delays), metrics often exhibit long-tailed distributions. While P50 provides a useful baseline, tail latencies and transient anomalies are usually masked by P50. In practice, operators rely heavily on P95 or P99 to detect SLA degradation and bottlenecks.

It would be great to get the authors' and the WG's thoughts on whether expanding the scope to cover higher percentiles makes sense for this draft.

Best regards,
Shunwan