nevtxjustin
join:2006-04-18
Dallas, TX
| UBNT AirMax ACK distance sweet spot
Kewlkeed will prolly post his discover in this forum later on, but here's what was in the UBNT forum...
said by kewlkeed  :It's allllllll in the ACK Lordy these things are sensitive on ACK! I just want to stress that for anyone who's having CCQ issues on what should be a decent link. Simple example. 2 KM link, semi-obstructed. -75 signal. Not the best, but it'll have to do. ACK was set for a 2KM link, got 11%CCQ and next to dialup speed (If it linked at all)... Screwed with ACK and finally got it happy around 4KM, both ends fired up to 117meg sync speed and 100%CCQ... Pounded it with Mikrotik speedtest (Yes I know not the best) and everything held out at about 25Meg with 100%CCQ. The speed test could have been better just the setup wasn't right for it at the time. Going to re-tweak the link tommorrow. Once these things are dialed into the right ACK settings, they fly! Like trying to tweak a 12 cylinder engine's timing. said by WHT_aka_NevTxJustin :
I can think if a fifth reason I don't live in Canada. The first four being three foot snow drifts, two month growing season, nine dollar pack of cigarettes, and one month skinny dippin' season...
...I'm too far for the kewl kid to hunt me down and ACK me to death.
Your observation just reminded me of something I completely, honest...completely forgotten.
Back in May or so, developers would SSH in and would at times change the ACK back to Auto or plus 10 per cent. I mentioned to Mike back in May that the ACK seemed to have a sweet spot of around plus forty percent. But I didn't ponder it further and completely forgot about it.
|
|
Inssomniak
Premium
join:2005-04-06
Cayuga, ON
1 edit | I just learned to set the ACK to about 7 miles for everything, and take the small performance hit instead of adjusting each CPE.
Only a few times did I ever have to adjust the ACK for really far customers. |
|
gunther_01
Premium
join:2004-03-29
Saybrook, IL
| reply to nevtxjustin
We've talked ACK before here, and its one of those topics since most every brand seems to do things differently. I like Star-OS's deal, pretty simple, actual miles PLUS 2 miles in the ACK field.
AUTO ACK is the worst flippen idea EVER. Turn it OFF!!!! Fall short on ACK and you get nothing. So over due it a bit and maybe sacrifice a LITTLE speed.
I would love to see every brand calibrate their units to use Miles and Kilo's instead of a raw number. It would make life sooo much easier, and things would most likely work better for everyone. Hint to developers. Just add the two miles in the calibration, and then when the new guys enter in actual it just works.  |
|
nevtxjustin
join:2006-04-18
Dallas, TX | This is for AirMax where there is a sweet spot that depends on each install. AirMax doesn't deal well with a one size fits all distance, unlike tradition gear. |
|
kewlkeed
Grouch
Premium
join:2005-02-05
Knowlton, QC
| reply to nevtxjustin
gunther got it right when it comes to turning the AutoACK off. Bigtime! Can't stress that enough with the Airmax stuff. It's totally FUBAR as far as I can tell. So yes as gunther says, OFF!! OFF DAMMIT!!!
But as my post indicates, I was just meaning to stress the point of how picky the ACK is on the airmax units and how much a couple points off will either completely make or break a link. |
|
nevtxjustin
join:2006-04-18
Dallas, TX | On my original 22 mile link, the auto ACK would often adjust it to 19 miles. I think its set at 29 miles right now, based on CCQ at 99 to 100% over random samples a day. At 25 miles it averaged 96 to 98%. |
|
gunther_01
Premium
join:2004-03-29
Saybrook, IL
| said by nevtxjustin :On my original 22 mile link, the auto ACK would often adjust it to 19 miles. I think its set at 29 miles right now, based on CCQ at 99 to 100% over random samples a day. At 25 miles it averaged 96 to 98%. I wouldn't call that a "sweet spot" but rather something is a miss in the software. And as far as AirMax goes yes it would be completely different. That's all about timing (TDMA), and if the ACK setting is at all related to the device timing it would be extremely important to have it set correct. The AP should have most of the control on the TDMA timing anyway. As it is the only fixed point in the whole system. (but that's just my theory)
In general Auto can't be perfect, just like auto with data rates is rarely perfect. At some point the device will scale down to "check" what the limits are, and then your too far down for a moment causing packet loss and such. Auto causes a lot of grief for just about all that we do, and we become at the mercy of the software guys. Be like the rotisserie guy, "set it and forget it"
UBNT should look in to getting the distance to ACK setting more accurate though. That alone would make life better and less complicated. You shouldn't need to tweak and watch for a few days, then tweak again, for a setting like that. Personally I would say a sweet spot would be plus or minus a mile of actual.
Another thought as I have seen this also, is that by being high your giving your unit a chance to fight against interference in the air. It adds a bit of a extra delay to the packet ACK wait time allowing your packets to get through, raising your CCQ rating. |
|
nevtxjustin
join:2006-04-18
Dallas, TX
| Mike said at UBNT said,
"Soon we will have our ACKless firmware to test for PTP links like this. Will eliminate the headache that is ACK with 11n."
And I asked...
"So will it be... AirMax ACKless ? ? ? But you know we'll call it A-MACK for short, bubba." |
|
thewisperer
Premium
join:2008-01-16
 ·TekSavvy Solutions..
| reply to nevtxjustin
this is of rocket with sector to Nano
did not have to play much with settings |
|
kewlkeed
Grouch
Premium
join:2005-02-05
Knowlton, QC
| reply to nevtxjustin
That's pretty much what's to be expected. You have a slight imbalance on the H/V Polarities, that if corrected would probably fix the Airmax levels right up to the top.
The test we ran for the short distance was a Nano-Nano and I still haven't gotten around to tweaking it. Too much on the go. |
|
smeghead
join:2009-02-11 | reply to nevtxjustin
I agree its all in the ack. I discovered this early on. |
|
