12Mar2020 [FreeBSD WIKI]

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Attendees: jtl, tuexen, rrs, rscheff

====== Discussion ======
  * tuexen discussed how to mitigate blackhole detection problems
    * Long-term ideas include PMTUD, D-SACK-based probing, etc. Using real data introduces congestion control algorithm concerns.
    * tuexen found that RTO length has dropped since blackhole detection values were set. Those values are based on RTO length. Therefore, he proposes a short-term change of setting fixed values for blackhole detection timer (which could be higher than current values) to reduce false positives.
    * rscheff points out that they also care about probing back to increase MSS when the blackhole is resolved.
    * Discussion about whether D-SACK-based probing would work and be "simple enough" for a short-term solution.
    * Action item:
      * tuexen will commit change to allow an administrator to commit a fixed value. The used value will be max(current calculate value, fixed value). Therefore, a fixed value of 0 will maintain the current behavior.
      * rscheff will propose a patch with the D-SACK probing he suggests.
  * D23904: KMOD_TCPSTAT_INC vs. TCPSTAT_INC: tuexen will commit change to use stable KPI from modules.

Next meeting: 26 March @ 1400 UTC