Some clarification: These were $99 connectorized radios which I chose because I am interested in a cheap upgrade from rockets or a more stable alternative to mikrotik. On a 40mhz channel I'm sure you'd see a benefit from the gigabit eth ports on the $500 radios.
When I say limiting it to 90Mbps eliminated the latency spike, that is true for aggregate as well. So If I limited it to 50Mbps TX and 40Mbps RX, it would not spike, if I limited TX to 50Mbps and left RX open, it would run up to ~55-60Mbps RX and then I saw the latency spike. I did this to eliminate 100mbps eth port as a bottleneck in testing. I am not real familiar with the Buffer Bloat issue Fred mentioned, but I can confirm I was seeing these results for >10 minutes constant using the Mikrotik bandwidth test, TCP, 20 connections, whatever packet size is the default (I think large). I was testing using a CCR at one end and a RB450 at the tower end. The 450 CPU may have been a bottleneck but througput was still much higher than the Rockets. I did ping the RB450 from a different interface and the ping times were normal so the latency spike was not due to CPU load on the RB450. Chris On Mon, Mar 10, 2014 at 9:01 AM, timothy steele <timothy.pct...@gmail.com>wrote: > The test setup they had at AF did not give me much hope that they are > doing real world testing they had the RF outputs from the SM's hard wired > to the AP > -- > Sent from Mailbox <https://www.dropbox.com/mailbox> for iPhone > > > On Mon, Mar 10, 2014 at 8:57 AM, Fred Goldstein <fgoldst...@ionary.com>wrote: > >> Very interesting, Chris, thanks If the latency is going up to 200-400 >> ms. and there are no other buffered network elements in the path, then it >> would seem to me that the ePMP has a very serious case of bufferbloat. >> This is sometimes done because it makes the radio seem to perform better on >> artificial speed tests (as it did), to the severe detriment of real-world >> performance. Nowadays, it's inexcusable. Are there any settings to >> control buffer sizes? Can someone find out from Cambium how much buffer is >> in there? >> >> On 3/10/2014 3:26 AM, Chris Fabien wrote: >> >> I spent some time tonight working with a couple ePMP radios on a test >> link and thought I'd share some results since I didn't get much feedback >> when I asked about this use case a couple weeks ago. >> >> Setup >> The link is a 7.5 mile link in a fairly noisy area, it has 2ft ubiquiti >> rocket dishes with RF Armor shield kits and formerly had normal Rocket M5 >> radios. Mikrotik CCR on one end and RB450 on other end. Evaluated latency >> and throughput between the two routers using the RouterOS bandwidth test. >> Used 20mhz channel throughout test. >> >> On a noisy frequency where the link had been running, about -75 noise >> floor, the Ubnt link would pass around 40 mbps aggregate with low latency >> <10ms. The ePMP would pass about 70mbps with stable 18ms latency, but >> performance was inconsistent when changing direction (tx/rx/both) - almost >> like the noise was little higher in one direction and affecting link >> stability when I tried to run traffic in that direction. It seemed a little >> less stable overall on that freq than the Ubnt radios. Throughout the >> testing at this freq MCS varied 9-13. >> >> On a cleaner frequency (DFS band) I was able to achieve solid MCS15. The >> ePMP was able to deliver >100mbps aggregate throughput consistently, which >> I found very impressive. The most I usually see from normal Rockets in this >> type of test is usually around 70mbps. >> >> The ePMP latency performance was a little unusual however. I noticed that >> when I saturated the link, latency jumped up to 200-400ms. If I restricted >> bandwidth to 90Mbps, I got nice consistent 18ms pings. When I run this type >> of test on ubnt I do not see a latency spike like this. Mikrotik radios >> running NV2 do increase at saturation, but only to around 100ms typically. >> So I would say ePMP performance is worse in this regard. >> >> I also noticed some inconsistent performance with regard to the ping >> times expected for the fixed/flexible scheduling in the ePMP. When I was >> first testing, I ran flexible mode and saw pings generally 6-10ms. In fixed >> mode, I saw 17-18 ms which I think is what's expected. That was several >> days ago... tonight I was seeing the 17-18ms even though I'm set to >> flexible - almost like it's stuck. I am able to push nearly full speed in >> both directions so it is definatley not in fixed mode. >> >> Hope this feedback is valuable for you all. I think these radios could be >> a very good option for low cost ptp radio, it would be nice if they could >> get the latency spike reduced. >> >> Chris Fabien >> LakeNet LLC >> >> >> >> _______________________________________________ >> Wireless mailing >> listWireless@wispa.orghttp://lists.wispa.org/mailman/listinfo/wireless >> >> >> >> -- >> Fred R. Goldstein k1io fred "at" interisle.net >> Interisle Consulting Group >> +1 617 795 2701 >> >> > > _______________________________________________ > Wireless mailing list > Wireless@wispa.org > http://lists.wispa.org/mailman/listinfo/wireless > >
_______________________________________________ Wireless mailing list Wireless@wispa.org http://lists.wispa.org/mailman/listinfo/wireless
