On Tue, Jul 24, 2018 at 1:11 PM Benjamin Cronce <[email protected]> wrote: > > Maybe the Bobbie idea already would do this, but I did not see it explicitly > mentioned on its wiki.
you are basically correct below. bobbie's core idea was a kinder, gentler, deficit mode policer, with something fq_codel-like aimed at reducing accumulated bytes to below the set rate. this is way different from conventional policers > The below is all about shaping ingress, not egress. > > My issue is that my ISP already does a good job with their AQM but nothing is > perfect and their implementation of rate limiting has a kind of burst at the > start. According to speedtests, my 250Mb connection starts off around 500Mb/s > and slowly drops over the next few seconds until a near perfect 250Mb/s > steady state. ideally their htb shaper would use fq_codel as the underlying qdisc. Or at least reduce their burst size to something saner. I hope it's not a policer. You can usually "see" a policer in action. Long strings of packets are dropped in a row. > The burst at the beginning adds a certain amount of destabilization to the > TCP flows since the window quickly grows to 500Mb and then has to backdown by > dropping. If I add my own traffic shaping and AQM, I can reduce the reported > TCP retransmissions from ~3% to ~0.1%. sure. > > The problem that I'm getting is by adding my own shaping, a measurable amount > of the benefit of their AQM is lost. While I am limited to Codel, HFSC+Codel, > or FairQ+Codel for now, I am actually doing a worse job of anti-bufferbloat > than my ISP is. Fewer latency spices according to DSLReports. ? measured how. > > This also does not touch on that the act of adding back-pressure in its > nature increases latency. I cannot say if it's a fundamental requirement in > order to better my current situation, but I am curious if there's a better > way. A thought that came to me is that like Bobbie, do a light touch as the > packets have already made their way and you don't want to aggressively drop > packets, but at the same time, I want the packets that already made the > journey to mostly unhindered enter my network. > > That's when I thought of a backpressure-less AQM. I like the restating of what policers do.... >Instead of having backpressure and measuring sojourn time as a function of how >long it takes packets to get scheduled, predict an estimated sojourn time >based on the observed rate of flow, but allow packets to immediately vacate >the queue. The AQM would either mark ECN or drop the packet, but never delay >the packet. aqms don't delay packets. shapers do. > In summary, my ISP seems to have better latency with their AQM, but due to > their shaper, loss during the burst is much higher than desirable. > > Maybe this will be mostly moot once I get fq_codel going on pfSense, but I do > find it an interesting issue. I thought it's been in there for a while? > _______________________________________________ > Bloat mailing list > [email protected] > https://lists.bufferbloat.net/listinfo/bloat -- Dave Täht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619 _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
