<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">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.<div><br></div><div>- Yes, I am using netperf 2.6.0 and netperf-wrapper from Toke's github repo.</div><div><br></div><div>- 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...</div><div><br></div><div>- 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.)</div><div><br></div><div>- I looked at the target calculation in Dave's Home Gateway best practices. (<a href="http://snapon.lab.bufferbloat.net/~d/draft-taht-home-gateway-best-practices-00.html">http://snapon.lab.bufferbloat.net/~d/draft-taht-home-gateway-best-practices-00.html</a>) Am I correct that it sets the target to five 1500-byte packet transmission time or 5 msec, whichever is greater?</div><div><br></div><div>- 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!</div><div><br></div><div>- 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?</div><div><br></div><div>- There's also a discussion of setting the target with "auto", but I'm not sure I understand the syntax.</div><div><br></div><div>Now to find some time to go back into the measurement lab! I'll report again when I have more data. Thanks again.</div><div><br></div><div>Rich</div><div><br></div><div><br></div><div><br></div><div><div><div>On Feb 24, 2014, at 9:56 AM, Aaron Wood <<a href="mailto:woody77@gmail.com">woody77@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">Do you have the latest (head) version of netperf and netperf-wrapper? some changes were made to both that give better UDP results.<div><br></div><div>-Aaron</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">
On Mon, Feb 24, 2014 at 3:36 PM, Rich Brown <span dir="ltr"><<a href="mailto:richb.hanover@gmail.com" target="_blank">richb.hanover@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
CeroWrt <a href="tel:3.10.28-14" value="+13102814">3.10.28-14</a> is doing a good job of keeping latency low. But... it has two other effects:<br>
<br>
- 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.<br>
<br>
- 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.<br>
<br>
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...<br>
<br>
Experimental setup:<br>
<br>
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.<br>
<br>
I have posted the results of my netperf-wrapper trials at <a href="http://richb-hanover.com/" target="_blank">http://richb-hanover.com</a> - There are a number of RRUL charts, taken with different link rates configured, and with different link layers.<br>
<br>
I welcome people's thoughts for other tests/adjustments/etc.<br>
<br>
Rich Brown<br>
Hanover, NH USA<br>
<br>
PS I did try the <a href="tel:3.10.28-16" value="+13102816">3.10.28-16</a>, 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 <a href="tel:3.10.28.14" value="+13102814">3.10.28.14</a>.<br>
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