On Tue, Oct 11, 2022 at 9:58 AM Bob McMahon via Rpm <r...@lists.bufferbloat.net> wrote: > > > Saturate a link in both directions simultaneously with multiple greedy > > flows while measuring load-dependent latency changes for small isochronous > > probe flows. > > This functionality is released in iperf 2.1.8 per the bounceback feature but, > unfortunately, OpenWRT doesn't maintain iperf 2 as a package anymore and uses > 2.0.13
iperf 2.1.8 was pushed into the openwrt mainline and may appear as of 22.03.1. I'll check. > > CLIENT SPECIFIC OPTIONS > > --bounceback[=n]run a TCP bounceback or rps test with optional number writes > in a burst per value of n. The default is ten writes every period and the > default period is one second (Note: set size with -l or --len which defaults > to 100 bytes)--bounceback-congest[=up|down|bidir][,n]request a concurrent > working load or TCP stream(s), defaults to full duplex (or bidir) unless the > up or down option is provided. The number of TCP streams defaults to 1 and > can be changed via the n value, e.g. --bounceback-congest=down,4 will use > four TCP streams from server to the client as the working load. The IP ToS > will be BE (0x0) for working load traffic.--bounceback-hold nrequest the > server to insert a delay of n milliseconds between its read and write > (default is no delay)--bounceback-period[=n]request the client schedule its > send(s) every n seconds (default is one second, use zero value for immediate > or continuous back to back)--bounceback-no-quickackrequest the server not set > the TCP_QUICKACK socket option (disabling TCP ACK delays) during a bounceback > test (see NOTES)--bounceback-txdelay nrequest the client to delay n seconds > between the start of the working load and the bounceback traffic (default is > no delay) > > On Tue, Oct 11, 2022 at 12:15 AM Sebastian Moeller <moell...@gmx.de> wrote: >> >> Hi Bob, >> >> On 11 October 2022 02:05:40 CEST, Bob McMahon <bob.mcma...@broadcom.com> >> wrote: >> >It's too big because it's oversized so it's in the size domain. It's >> >basically Little's law's value for the number of items in a queue. >> > >> >*Number of items in the system = (the rate items enter and leave the >> >system) x (the average amount of time items spend in the system)* >> > >> > >> >Which gets driven to the standing queue size when the arrival rate >> >exceeds the service rate - so the driving factor isn't the service and >> >arrival rates, but *the queue size *when *any service rate is less than an >> >arrival rate.* >> >> [SM] You could also argue it is the ratio of arrival to service rates, with >> the queue size being a measure correlating with how long the system will >> tolerate ratios larger than one... >> >> >> > >> >In other words, one can find and measure bloat regardless of the >> >enter/leave rates (as long as the leave rate is too slow) and the value of >> >memory units found will always be the same. >> > >> >Things like prioritizations to jump the line are somewhat of hacks at >> >reducing the service time for a specialized class of packets but nobody >> >really knows which packets should jump. >> >> [SM] Au contraire most everybody 'knows' it is their packets that should >> jump ahead of the rest ;) For intermediate hop queues however that endpoint >> perception is not really actionable due to lack of robust and reliable >> importance identifiers on packets. In side a 'domain' dscps might work if >> treated to strict admission control, but that typically will not help >> end2end traffic over the internet. This is BTW why I think FQ is a great >> concept, as it mostly results in the desirable outcome of not picking >> winners and losers (like arbitrarily starving a flow), but I digress. >> >> >Also, nobody can define what >> >working conditions are so that's another problem with this class of tests. >> >> [SM] While real working conditions will be different for each link and >> probably vary over time, it seems achievable to come up with a set of >> pessimistic assumptions how to model a challenging work condition against >> which to test potential remedies, assuming that such remedies will also work >> well under less challenging conditions, no? >> >> >> > >> >Better maybe just to shrink the queue and eliminate all unneeded queueing >> >delays. >> >> [SM] The 'unneeded' does a lot of work in that sentence ;). I like Van's? >> Description of queues as shock absorbers so queue size will have a lower >> acceptable limit assuming users want to achieve 'acceptable' throughput even >> with existing bursty senders. (Not all applications are suited for pacing so >> some level of burstiness seems unavoidable). >> >> >> > Also, measure the performance per "user conditions" which is going >> >to be different for almost every environment (and is correlated to time and >> >space.) So any engineering solution is fundamentally suboptimal. >> >> [SM] A matter of definition, if the requirement is to cover many user >> conditions the optimality measure simply needs to be changed from per >> individual condition to over many/all conditions, no? >> >> >Even >> >pacing the source doesn't necessarily do the right thing because that's >> >like waiting in the waitlist while at home vs the restaurant lobby. >> >> [SM] +1. >> >> > Few >> >care about where messages wait (unless the pitch is AQM is the only >> >solution that drives to a self-fulfilling prophecy - that's why the tests >> >have to come up with artificial conditions that can't be simply defined.) >> >> Hrm, so the RRUL test, while not the end all of bufferbloat/working >> conditions tests, is not that complicated: >> Saturate a link in both directions simultaneously with multiple greedy flows >> while measuring load-dependent latency changes for small isochronous probe >> flows. >> >> Yes, the it would be nice to have additional higher rate probe flows also >> bursty ones to emulate on-linev games, and 'pumped' greedy flows to emulate >> DASH 'streaming', and a horde of small greedy flows that mostly end inside >> the initial window and slow start. But at its core existing RRUL already >> gives a useful estimate on how a link behaves under saturating loads all the >> while being relatively simple. >> The responsiveness under working condition seems similar in that it tries to >> saturate a link with an increasing number of greedy flows, in a sense to >> create a reasonable bad case that ideally rarely happens. >> >> Regards >> Sebastian >> >> >> > >> >Bob >> > >> >On Mon, Oct 10, 2022 at 3:57 PM David Lang <da...@lang.hm> wrote: >> > >> >> On Mon, 10 Oct 2022, Bob McMahon via Bloat wrote: >> >> >> >> > I think conflating bufferbloat with latency misses the subtle point in >> >> that >> >> > bufferbloat is a measurement in memory units more than a measurement in >> >> > time units. The first design flaw is a queue that is too big. This >> >> youtube >> >> > video analogy doesn't help one understand this important point. >> >> >> >> but the queue is only too big because of the time it takes to empty the >> >> queue, >> >> which puts us back into the time domain. >> >> >> >> David Lang >> >> >> >> > Another subtle point is that the video assumes AQM as the only solution >> >> and >> >> > ignores others, i.e. pacing at the source(s) and/or faster service >> >> rates. A >> >> > restaurant that let's one call ahead to put their name on the waitlist >> >> > doesn't change the wait time. Just because a transport layer slowed down >> >> > and hasn't congested a downstream queue doesn't mean the e2e latency >> >> > performance will meet the gaming needs as an example. The delay is still >> >> > there it's just not manifesting itself in a shared queue that may or may >> >> > not negatively impact others using that shared queue. >> >> > >> >> > Bob >> >> > >> >> > >> >> > >> >> > On Mon, Oct 10, 2022 at 2:40 AM Sebastian Moeller via Make-wifi-fast < >> >> > make-wifi-f...@lists.bufferbloat.net> wrote: >> >> > >> >> >> Hi Erik, >> >> >> >> >> >> >> >> >>> On Oct 10, 2022, at 11:32, Taraldsen Erik <erik.tarald...@telenor.no> >> >> >> wrote: >> >> >>> >> >> >>> On 10/10/2022, 11:09, "Sebastian Moeller" <moell...@gmx.de> wrote: >> >> >>> >> >> >>> Nice! >> >> >>> >> >> >>>> On Oct 10, 2022, at 07:52, Taraldsen Erik via Cake < >> >> >> cake@lists.bufferbloat.net> wrote: >> >> >>>> >> >> >>>> It took about 3 hours from the video was release before we got the >> >> >> first request to have SQM on the CPE's we manage as a ISP. Finally >> >> >> getting some customer response on the issue. >> >> >>> >> >> >>> [SM] Will you be able to bump these requests to higher-ups and >> >> >>> at >> >> >> least change some perception of customer demand for tighter latency >> >> >> performance? >> >> >>> >> >> >>> That would be the hope. >> >> >> >> >> >> [SM} Excellent, hope this plays out as we wish for. >> >> >> >> >> >> >> >> >>> We actually have fq_codel implemented on the two latest generations >> >> >>> of >> >> >> DSL routers. Use sync rate as input to set the rate. Works quite >> >> >> well. >> >> >> >> >> >> [SM] Cool, if I might ask what fraction of the sync are you >> >> >> setting the traffic shaper for and are you doing fine grained overhead >> >> >> accounting (or simply fold that into a grand "de-rating"-factor)? >> >> >> >> >> >> >> >> >>> There is also a bit of traction around speedtest.net's inclusion of >> >> >> latency under load internally. >> >> >> >> >> >> [SM] Yes, although IIUC they are reporting the interquartile >> >> mean >> >> >> for the two loaded latency estimates, which is pretty conservative and >> >> only >> >> >> really "triggers" for massive consistently elevated latency; so I >> >> >> expect >> >> >> this to be great for detecting really bad cases, but I fear it is too >> >> >> conservative and will make a number of problematic links look OK. But >> >> hey, >> >> >> even that is leaps and bounds better than the old only idle latency >> >> report. >> >> >> >> >> >> >> >> >>> My hope is that some publication in Norway will pick up on that score >> >> >> and do a test and get some mainstream publicity with the results. >> >> >> >> >> >> [SM] Inside the EU the challenge is to get national regulators >> >> and >> >> >> the BEREC to start bothering about latency-under-load at all, "some >> >> >> mainstream publicity" would probably help here as well. >> >> >> >> >> >> Regards >> >> >> Sebastian >> >> >> >> >> >> >> >> >>> >> >> >>> -Erik >> >> >>> >> >> >>> >> >> >>> >> >> >> >> >> >> _______________________________________________ >> >> >> Make-wifi-fast mailing list >> >> >> make-wifi-f...@lists.bufferbloat.net >> >> >> https://lists.bufferbloat.net/listinfo/make-wifi-fast >> >> > >> >> >_______________________________________________ >> >> Bloat mailing list >> >> bl...@lists.bufferbloat.net >> >> https://lists.bufferbloat.net/listinfo/bloat >> >> >> > >> >> -- >> Sent from my Android device with K-9 Mail. 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If you received this e-mail in error, please return > the e-mail to the sender, delete it from your computer, and destroy any > printed copy of it._______________________________________________ > Rpm mailing list > r...@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/rpm -- This song goes out to all the folk that thought Stadia would work: https://www.linkedin.com/posts/dtaht_the-mushroom-song-activity-6981366665607352320-FXtz Dave Täht CEO, TekLibre, LLC _______________________________________________ Cake mailing list Cake@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/cake
