<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><blockquote type="cite" class="">On 26 Aug, 2023, at 2:48 pm, Sebastian Moeller via Ecn-sane <<a href="mailto:ecn-sane@lists.bufferbloat.net" class="">ecn-sane@lists.bufferbloat.net</a>> wrote:<br class=""><br class="">percentage of packets marked: 100 * (2346329 / 3259777) = 72%<br class=""><br class="">This seems like too high a marking rate to me. I would naively expect that a flow on getting a mark scale back by its cwin by 20-50% and then slowly increaer it again, so I expect the actual marking rate to be considerably below 50% per flow...<br class=""></blockquote><br class=""><blockquote type="cite" class="">My gut feeling is that these steam flows do not obey RFC3168 ECN (or something wipes the CE marks my router sends upstream along the path)... but without a good model what marking rate I should expect this is very hand-wavy, so if anybody could help me out with an easy derivation of the expected average marking rate I would be grateful.<br class=""></blockquote><br class=""><div class="">Yeah, that's definitely too much marking. We've actually seen this behaviour from Steam servers before, but they had fixed it at some point. Perhaps they've unfixed it again.</div><div class=""><br class=""></div><div class="">My best guess is that they're running an old version of BBR with ECN negotiation left on. BBRv1, at least, completely ignores ECE responses. Fortunately BBR itself does a good job of congestion control in the FQ environment which Cake provides, as you can tell by the fact that the queues never get full enough to trigger heavy dropping.</div><div class=""><br class=""></div><div class="">The CUBIC RFC offers an answer to your question:</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="24475E4D-4E63-4F63-82D1-686917A15F39" src="cid:61242A12-7B72-4562-A737-FB1FD106E5EF" class=""></div><div class=""><br class=""></div><div class="">Reading the table, for RTT of 100ms and throughput 100Mbps in a single flow, a "loss rate" (equivalent to a marking rate) of about 1 per 7000 packets is required. The formula can be rearranged to find a more general answer.</div><div class=""><br class=""></div><div class=""> - Jonathan Morton</div></body></html>