Subject: [aqm] [Technical Errata Reported] RFC8033 (5095)

From: RFC Errata System <[email-masked]>
Date: Thu, 24 Aug 2017 10:13:51 -0700 (PDT)

The following errata report has been submitted for RFC8033,
"Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem".

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You may review the report below and at:
http://www.rfc-editor.org/errata/eid5095

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Type: Technical
Reported by: Liang Tian <[email-masked]>

Section: 5.2

Original Text
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      if PIE->in_measurement_ == TRUE:
         PIE->dq_count_ = PIE->dq_count_ + deque_pkt_size;
         if PIE->dq_count_ >= DQ_THRESHOLD then
            weight = DQ_THRESHOLD/2^16
            PIE->avg_dq_time_ = (now - PIE->measurement_start_) *
                                weight + PIE->avg_dq_time_ *
                                (1 - weight);
            PIE->dq_count_ = 0;
            PIE->measurement_start_ = now
         else
            PIE->in_measurement_ = FALSE;

Corrected Text
--------------
      if PIE->in_measurement_ == TRUE:
         PIE->dq_count_ = PIE->dq_count_ + deque_pkt_size;
         if PIE->dq_count_ >= DQ_THRESHOLD then
            weight = DQ_THRESHOLD/2^16
            PIE->avg_dq_time_ = (now - PIE->measurement_start_) *
                                weight + PIE->avg_dq_time_ *
                                (1 - weight);
            PIE->in_measurement_ = FALSE;

Notes
-----
There should not be an "else" because if PIE->dq_count_ >= DQ_THRESHOLD, this measurement is over: avg_dq_time is calculated and in_measurement is set to FALSE; otherwise dq_count has been increased before this "if" and now we wait for next packet. Resetting dq_count and measurement_start is not necessary because they will be set again when a new measurement begins.

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RFC8033 (draft-ietf-aqm-pie-10)
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Title               : Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem
Publication Date    : February 2017
Author(s)           : R. Pan, P. Natarajan, F. Baker, G. White
Category            : EXPERIMENTAL
Source              : Active Queue Management and Packet Scheduling
Area                : Transport
Stream              : IETF
Verifying Party     : IESG