. Invoce with "tc_stab_parameter_guide_03('path/to/the/data/file/you/created/name_of_said_file')". The parser will run on the first invocation and is reallr really slow, but further invocations should be faster. If issues arise, let me know, I am happy to help. > > Were I to use a single directly connected gateway, I would input a suitable value for PPPoA in that openWRT firmware. I think you should do that right now. > In theory, I might need to use a negative value, bmt the current kernel does not support that. If you use tc_stab, negative overheads are fully supported, only htb_private has overhead defined as unsigned integer and hence does not allow negative values. > I have used many different arbitrary values for overhead. All appear to have little effect. So the issue here is that only at small packet sizes does the overhead and last cell padding eat a disproportionate amount of your bandwidth (64 byte packet plus 44 byte overhead plus 47 byte worst case cell padding: 100* (44+47+64)/64 = 242% effective packet size to what the shaper estimated ), at typical packet sizes the max error (44 bytes missing overhead and potentially misjudged cell padding of 47 bytes adds up to a theoretical 100*(44+47+1500)/1500 = 106% effective packet size to what the shaper estimated). It is obvious that at 1500 byte packets the whole ATM issue can be easily dismissed with just reducing the link rate by ~10% for the 48 in 53 framing and an additional ~6% for overhead and cell padding. But once you mix smaller packets in your traffic for say VoIP, the effective wire size misjudgment will kill your ability to control the queueing. Note that the common wisdom of shape down to 85% might be fem the ~15% ATM "tax" on 1500 byte traffic size... > As I understand it, the current recommendation is to use tc_stab in preference to htb_private. I do not know the basis for this value judgement. In short: tc_stab allows negative overheads, tc_stab works with HTB, TBF, HFSC while htb_private only works with HTB. Currently htb_private has two advantages: it will estimate the per packet overhead correctly of GSO (generic segmentation offload) is enabled and it will produce exact ATM link layer estimates for all possible packet sizes. In practice almost everyone uses an MTU of 1500 or less for their internet access making both htb_private advantages effectively moot. (Plus if no one beats me to it I intend to address both theoretical short coming of tc_stab next year). Best Regards Sebastian > > > > > > On 28/12/13 10:01, Sebastian Moeller wrote: >> Hi Rich, >> >> great! A few comments: >> >> Basic Settings: >> [Is 95% the right fudge factor?] I think that ideally, if we get can precisely measure the useable link rate even 99% of that should work out well, to keep the queue in our device. I assume that due to the difficulties in measuring and accounting for the link properties as link layer and overhead people typically rely on setting the shaped rate a bit lower than required to stochastically/empirically account for the link properties. I predict that if we get a correct description of the link properties to the shaper we should be fine with 95% shaping. Note though, it is not trivial on an adel link to get the actually useable bit rate from the modem so 95% of what can be deduced from the modem or the ISP's invoice might be a decent proxy… >> >> [Do we have a recommendation for an easy way to tell if it's working? Perhaps a link to a new Quick Test for Bufferbloat page. ] The linked page looks like a decent probe for buffer bloat. >> >> >>> Basic Settings - the details... >>> >>> CeroWrt is designed to manage the queues of packets waiting to be sent across the slowest (bottleneck) link, which is usually your connection to the Internet. >>> >> I think we can only actually control the first link to the ISP, which often happens to be the bottleneck. At a typical DSLAM (xDSL head end station) the cumulative sold bandwidth to the customers is larger than the back bone connection (which is called over-subscription and is almost guaranteed to be the case in every DSLAM) which typically is not a problem, as typically people do not use their internet that much. My point being we can not really control congestion in the DSLAM's uplink (as we have no idea what the reserved rate per customer is in the worst case, if there is any). >> >> >>> CeroWrt can automatically adapt to network conditions to improve the delay/latency of data without any settings. >>> >> Does this describe the default fq_codels on each interface (except fib?)? >> >> >>> However, it can do a better job if it knows more about the actual link speeds available. You can adjust this setting by entering link speeds that are a few percent below the actual speeds. >>> >>> Note: it can be difficult to get an accurate measurement of the link speeds. The speed advertised by your provider is a starting point, but your experience often won't meet their published specs. You can also use a speed test program or web site like >>> http://speedtest.net >>> to estimate actual operating speeds. >>> >> While this approach is commonly recommended on the internet, I do not believe that it is that useful. Between a user and the speediest site there are a number of potential congestion points that can affect (reduce) the throughput, like bad peering. Now that said the sppedtets will report something <= the actual link speed and hence be conservative (interactivity stays great at 90% of link rate as well as 80% so underestimating the bandwidth within reason does not affect the latency gains from traffic shaping it just sacrifices a bit more bandwidth; and given the difficulty to actually measure the actually attainable bandwidth might have been effectively a decent recommendation even though the theory of it seems flawed) >> >> >>> Be sure to make your measurement when network is quiet, and others in your home aren’t generating traffic. >>> >> This is great advise. >> >> I would love to comment further, but after reloading >> http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_AQM_for_CeroWrt_310 >> just returns a blank page and I can not get back to the page as of yesterday evening… I will have a look later to see whether the page resurfaces… >> >> Best >> Sebastian >> >> >> On Dec 27, 2013, at 23:09 , Rich Brown >> >> wrote: >> >> >>>> You are a very good writer and I am on a tablet. >>>> >>>> >>> Thanks! >>> >>>> Ill take a pass at the wiki tomorrow. >>>> >>>> The shaper does up and down was my first thought... >>>> >>>> >>> Everyone else… Don’t let Dave hog all the fun! Read the tech note and give feedback! >>> >>> Rich >>> >>> >>>> On Dec 27, 2013 10:48 AM, "Rich Brown" >>>> wrote: >>>> I updated the page to reflect the 3.10.24-8 build, and its new GUI pages. >>>> >>>> >>>> http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_AQM_for_CeroWrt_310 >>>> >>>> >>>> There are still lots of open questions. Comments, please. >>>> >>>> Rich >>>> _______________________________________________ >>>> Cerowrt-devel mailing list >>>> >>>> Cerowrt-devel@lists.bufferbloat.net >>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel >>> _______________________________________________ >>> Cerowrt-devel mailing list >>> >>> Cerowrt-devel@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/cerowrt-devel >> _______________________________________________ >> Cerowrt-devel mailing list >> >> Cerowrt-devel@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/cerowrt-devel >