Hello.
I have a PTMP setup with a RB912UAB AP with a Ubiquity AM-5G19-120 antenna.
9 Clients: 3x RB911G-5HPnD, 6x RB SXT-5HPnD
All at Router OS 6.24
I use NV2

Occasionally i have really bad speed on my entire network.
I have come down to that one of my clients (RB911G-5HPnD) is the problem.
It opperates at 6.5 Mbps and my whole network does the same.
If i remove it from the access list everything work perfect.

Is it really possible that one client can take down the overall network speed for the other clients?
How can i prevent this?
Can i remove 6.5 Mbps as a option? how?
What is the minimum signal strength i should allow on my network?

This is my AP wireless setup:

/interface wireless
set [ find default-name=wlan1 ] adaptive-noise-immunity=ap-and-client-mode \
band=5ghz-onlyn channel-width=20/40mhz-ht-above country="norway 5.8 p-p" \
default-authentication=no default-forwarding=no disabled=no frequency=\
5780 frequency-mode=regulatory-domain hide-ssid=yes ht-guard-interval=\
long ht-rxchains=0,1 ht-supported-mcs="mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5\
,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-13,mcs-14,mcs-15" \
ht-txchains=0,1 l2mtu=2290 mode=ap-bridge nv2-cell-radius=10 \
nv2-preshared-key=xxxxxxxx nv2-security=enabled radio-name=\
HUSEBY-BB5-AP1 security-profile=S1 ssid=xxxx wireless-protocol=\
nv2

Any ideas on my setup?
I am happy for all help

The bad client seems to have serious issues with interference and also the 11dB difference between CH0 and CH1 is suspicious. Is this SXT or 911? Might be too far for the antenna used, you may want to use better antenna to keep the signal similar to other clients.

This client uses all airtime when passes data, therefore performance of whole AP gets bad. Apparently this is happening even NV2 is using TDMA. Thats why we need some kind of airtime priority to be able to limit bad clients.

Thanks for your answer.
This is a 911. I found out the client had a bad placement.

But the question is, how can i ensure that this will not happen again?
I can set a "Signal strength range" at minimum -65dm in the "Access List"
But is it a better way of doing this?

I have a plan of expanding my network, and i cannot let one customer take down the network this easy.

Anyone with experience on this?

Well, when you are building the network you need to make sure your clients are properly installed, aimed and that they all have similar signal strength. Do not allow such a bad client to connect to the AP, low CCQ and low signal is the values you are looking for.

I guess at this moment there is no way how to protect the AP, however if you are connecting the clients yourself then you can make sure that its properly installed and have a good signal / CCQ.

The competitors HW have same problem even both are using the TDMA. But competitor implemented the priority which can be set at the client radio and this should help to prevent the bad client to eat all the airtime of the AP.

I guess many of us have already asked Mikrotik to implement similar client priority feature but I am not sure if it has been accepted by the devs or not. Anyway this will still not prevent you from unexpected signal / CCQ drop and you would still need to monitor your APs (which all of us do all the time) for the bad boys.

Access list and minimum signal strength is a good thing but sometimes the signal could be OK but bad CCQ because of interference. In this case the client will still be connected to your AP because will have good signal but performance would be bad because of bad CCQ...

Lets hope they implement prioritation then.
I have set the minimum Connection db to -65.
Then in my case the problem stopped, and i contacted the customer to find a better placement of the CPE.
Its better to have a strict policy on signal and loose connection on one customer, than loose speed on all.

Can i remove the lower speeds? So it cannot Connect on 6.5Mbps ?

Thanks for your help.

..(cut) .. using the TDMA.. .. priority .. can be set at the client radio and this should help to prevent the bad client to eat all the airtime of the AP...

Surely priority should be implemented because it's useful on many situations (e.g. pro users vs best effort ones) ..and I'm sure you are right but I was guessing "why" ..?!?
..TDMA should distribute equal time slots to clients.. or not?

If I understand well:
- any clients handshake their best speed with AP
- any client use their assigned time slot at their maximum possible speed with AP (if Tdma ..if not I don't know which mechanism is adopted..)
- a bad client use inefficiently his air time.. but why it penalize also others ????? how?

thanks in advance for any info you would give to me

mikrotik devs ..help

..(cut) .. using the TDMA.. .. priority .. can be set at the client radio and this should help to prevent the bad client to eat all the airtime of the AP...

Surely priority should be implemented because it's useful on many situations (e.g. pro users vs best effort ones) ..and I'm sure you are right but I was guessing "why" ..?!?
..TDMA should distribute equal time slots to clients.. or not?

If I understand well:
- any clients handshake their best speed with AP
- any client use their assigned time slot at their maximum possible speed with AP (if Tdma ..if not I don't know which mechanism is adopted..)
- a bad client use inefficiently his air time.. but why it penalize also others ????? how?

thanks in advance for any info you would give to me

+1

..(cut) .. using the TDMA.. .. priority .. can be set at the client radio and this should help to prevent the bad client to eat all the airtime of the AP...

Surely priority should be implemented because it's useful on many situations (e.g. pro users vs best effort ones) ..and I'm sure you are right but I was guessing "why" ..?!?
..TDMA should distribute equal time slots to clients.. or not?

If I understand well:
- any clients handshake their best speed with AP
- any client use their assigned time slot at their maximum possible speed with AP (if Tdma ..if not I don't know which mechanism is adopted..)
- a bad client use inefficiently his air time.. but why it penalize also others ????? how?

thanks in advance for any info you would give to me

I would like to answer but honesly I dont know why maybe its because of implementation of TDMA, it needs to be fair for all stations and when the station asks for amount of airtime, its been given by the AP.. And because its bad signal/ccq station it needs a lot of retransmissions so it takes all airtime of the AP. But why it is affecting other stations when they also ask for their airtime thats a question. I know that Ubiquiti has same problem and they recommend to set the lowest priority to bad clients so they dont affect overal performance of the AP..

Hello, increment on AP tdma-period-size=6

regards

ARIEL HORAS

..(cut) .. using the TDMA.. .. priority .. can be set at the client radio and this should help to prevent the bad client to eat all the airtime of the AP...

Surely priority should be implemented because it's useful on many situations (e.g. pro users vs best effort ones) ..and I'm sure you are right but I was guessing "why" ..?!?
..TDMA should distribute equal time slots to clients.. or not?

If I understand well:
- any clients handshake their best speed with AP
- any client use their assigned time slot at their maximum possible speed with AP (if Tdma ..if not I don't know which mechanism is adopted..)
- a bad client use inefficiently his air time.. but why it penalize also others ????? how?

thanks in advance for any info you would give to me

I would like to answer but honesly I dont know why maybe its because of implementation of TDMA, it needs to be fair for all stations and when the station asks for amount of airtime, its been given by the AP.. And because its bad signal/ccq station it needs a lot of retransmissions so it takes all airtime of the AP. But why it is affecting other stations when they also ask for their airtime thats a question. I know that Ubiquiti has same problem and they recommend to set the lowest priority to bad clients so they dont affect overal performance of the AP..

Problem is the cpu of the APs is not fast enough to handle tdma protocol smooth. Plain 802.11 is done by the wireless card but tdma puts a big load to the cpu. With .ac you see plain 802.11 is faster than nv2 due to this. UBNT has some additional HW in some of their newer products to keep up with the cpu load. Cambium tweaked the HW in their ePMP series, too.

If you run into this throw more HW on the problem. So add another AP and keep the number of CPEs/AP low.

Problem is the cpu of the APs is not fast enough to handle tdma protocol smooth. Plain 802.11 is done by the wireless card but tdma puts a big load to the cpu. With .ac you see plain 802.11 is faster than nv2 due to this. UBNT has some additional HW in some of their newer products to keep up with the cpu load. Cambium tweaked the HW in their ePMP series, too.

If you run into this throw more HW on the problem. So add another AP and keep the number of CPEs/AP low.

In this case, I did not have a CPU issue. Both my AP and CPE is 600Mhz and over 50% free CPU.

All the other Clients shares 6,5 Mbit which is the lowest wireless speed on 802.11N.

Can i disallow access on 6,5 Mbit ?

What if i remove MCS 0 from HT supported MCS?

AFAIK the slowest speed is used by AP for beaconing and you should not disable it

Anyway, I guess even if you disable it ..it should work because it's not really disabled. maybe worth a test?!

I am having a possibly somewhat similar problem, have posted about it here:

http://forum.mikrotik.com/viewtopic.php?f=7&t=94154

I'm wondering now is it because one Client is showing 6.5Mbps its pulling the rest down.

Although my clients only seem to be at 6.5Mbps when they are idle and ramp up when in use. I'm using NStreme and AC? I only have 2 x clients and signals are perfect <1km links.