RFC 8033, "Proportional Integral Controller Enhanced (PIE): A Lightweight Control Scheme to Address the Bufferbloat Problem", February 2017

Errata ID: 5095
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Liang Tian
Date Reported: 2017-08-24
Verifier Name: Mirja Kühlewind
Date Verified: 2020-03-04

Section 5.2 says:

      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;

It should say:

      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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