Thanks everyone for all the good advice. I will summarize my responses to all your notes now, then I'll go away and run more tests.
- Yes, I am using netperf 2.6.0 and netperf-wrapper from Toke's github repo. - The "sync rate" is the speed with which the DSL modem sends bits to/from my house. I got this by going into the modem's admin interface and poking around. (It turns out that I have a very clean line, high SNR, low attenuation. I'm much less than a km from the central office.) So actual speed should approach this, except... - Of course, I have to subtract all those overheads that Sebastian described - ATM 48-in-53, which knocks off 10%; ATM frame overhead which could add up to 47 bytes padding to any packet, etc.) - I looked at the target calculation in Dave's Home Gateway best practices. (http://snapon.lab.bufferbloat.net/~d/draft-taht-home-gateway-best-practices-00.html) Am I correct that it sets the target to five 1500-byte packet transmission time or 5 msec, whichever is greater? - I was astonished by the calculation of the bandwidth consumed by acks in the reverse direction. In a 7mbps/768kbps setting, I'm going to lose one quarter of the reverse bandwidth? Wow! - I wasn't entirely clear how to set the target in the SQM GUI. I believe that "target ##msec" is an acceptable format. Is that correct? - There's also a discussion of setting the target with "auto", but I'm not sure I understand the syntax. Now to find some time to go back into the measurement lab! I'll report again when I have more data. Thanks again. Rich On Feb 24, 2014, at 9:56 AM, Aaron Wood <[email protected]> wrote: > Do you have the latest (head) version of netperf and netperf-wrapper? some > changes were made to both that give better UDP results. > > -Aaron > > > On Mon, Feb 24, 2014 at 3:36 PM, Rich Brown <[email protected]> wrote: > > CeroWrt 3.10.28-14 is doing a good job of keeping latency low. But... it has > two other effects: > > - I don't get the full "7 mbps down, 768 kbps up" as touted by my DSL > provider (Fairpoint). In fact, CeroWrt struggles to get above 6.0/0.6 mbps. > > - When I adjust the SQM parameters to get close to those numbers, I get > increasing levels of packet loss (5-8%) during a concurrent ping test. > > So my question to the group is whether this behavior makes sense: that we can > have low latency while losing ~10% of the link capacity, or that getting > close to the link capacity should induce large packet loss... > > Experimental setup: > > I'm using a Comtrend 583-U DSL modem, that has a sync rate of 7616 kbps down, > 864 kbps up. Theoretically, I should be able to tell SQM to use numbers a bit > lower than those values, with an ATM plus header overhead with default > settings. > > I have posted the results of my netperf-wrapper trials at > http://richb-hanover.com - There are a number of RRUL charts, taken with > different link rates configured, and with different link layers. > > I welcome people's thoughts for other tests/adjustments/etc. > > Rich Brown > Hanover, NH USA > > PS I did try the 3.10.28-16, but ran into troubles with wifi and ethernet > connectivity. I must have screwed up my local configuration - I was doing it > quickly - so I rolled back to 3.10.28.14. > _______________________________________________ > Cerowrt-devel mailing list > [email protected] > https://lists.bufferbloat.net/listinfo/cerowrt-devel >
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