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 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
>>
>>
>> _______________________________________________
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>> Wireless@wispa.org
>> http://lists.wispa.org/mailman/listinfo/wireless
> --
> Fred R. Goldstein k1io fred "at" interisle.net
> Interisle Consulting Group
> +1 617 795 2701
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