Low throughput and high latency on 2,4ghz AP after some time

CyberTod · Wed Jan 25, 2012 10:49 am

Hello,

I have a RB433 with ROS v5.11 installed. The internet comes on a wireless 5ghz PtP link and there are no problems with it, the throughput and latency are stable at all times.
There are clients connected on an omnidirectional antenna, around 15 clients, their signals are -60dBm ~ -75dBm, ccq is between 70 and 100. The wireless card is Atheros AR5213.
The problem is that the latency goes to 1-2sec and at that time the throughput can not go over 1Mbit/s. If I disconnect all clients so they can connect again all goes no normal - latency is 2-3ms, the throughput can go to 10-12Mbit/s. But after some time that varies from 2min to 30min all goes bad again, reconnecting the clients immediately solves all problems for another short amount of time.

mahnet · Wed Jan 25, 2012 9:32 pm

check broadcast amongst users. use some firewall rules as instructed in wiki. it should help.

CyberTod · Wed Jan 25, 2012 10:07 pm

I added a rule to limit connections to 35 on every user. It improves things a little, but still the problem exists. I have 300-400 Tx and the same number Rx packets.

mikb262 · Sun Feb 05, 2012 5:21 pm

i have same problum
i m useing too rb433 with mini pci R52h
same situation when users more then 20 online
my through put rate stable but Rx rate decreesing at 1mb when latency going high like 200ms 400ms
plz help

eszaknet · Mon Feb 06, 2012 1:26 am

Try to use nv2 protocol, if the clients are mikrotiks

mikb262 · Mon Feb 06, 2012 5:15 pm

i m useing at client end tp link products
like g500 wn5210 wn722n wn422g only
plzz tel some solution

eszaknet · Mon Feb 06, 2012 7:33 pm

20 clients?

I now see it.
I think, if you would like to work this normally, you have to reduce your clients maximum 10/AP in 2,4Ghz b or g mode without TDMA.
You try to enable hardware protection rts/cts on AP and clients, set up the rts threshold, and the frame fragmentation (Hidden node problem and collission).
It is not enough just on the AP!

Watch the ack times in registration table and if it is too large (greater than 100) or not a stable value, maybe the client is bad.

Suddenly I haven't any ideas.

CyberTod · Thu Feb 09, 2012 10:24 am

I have tried using rts/cts but it changes nothing. I did not however played with the threshold value. Can you advice on some value ? The best throughput is when I use g-only standard with full auto on tx-rate. I would like to use nv2 as i know it will improve things a lot, but all clients are tp-link.
The thing that helped me most so far is limiting to 3 udp connections (!53) and 10 tcp connections on 1024-65535 ports.
Still the latency spikes to 1sec for about half an hour and then goes back normal.
Also I wonder if frame lifetime can help with things ?

eszaknet · Thu Feb 09, 2012 3:09 pm

Try to set the rts threshold to 512 in the AP, and in TP-Link clients. The frame life time...I don't know exactly, I think it's a store time, so how many times will be stored a frame if the router can't send it instantly, before drop them.
I don't know the value is milli-, mikro- or nanosec for frame lifetime. This is not sure to help you, but try it.

But my opinion, without TDMA 10 active clients are the maximum (outdoor) in one 2,4Ghz AP.

0ldman · Thu Feb 09, 2012 6:32 pm

Just a slightly different perspective, I've got 31 clients on a single R52H, straight 802.11G. This AP is going to be upgraded soon, but the only problem I have with it now is if someone is using torrents, which caused the same problem back when there were only 5 people on it.

Sounds like you may have a problem with your card or a bad client. Have you run torch to see what is going across the interface during these problems?

Bittorrent will send thousands of UDP packets per second. The data rate will only be ~100k, but it will thrash an access point.

CyberTod, would you mind posting your connection limit rules? I have tried several different methods and had no luck.

CyberTod · Thu Feb 09, 2012 10:25 pm

Almost all of my clients use torrents

I have an AP with ~30 clients too, the situation is almost the same. So I guess the torrent users do more damage than connected clients.

1 ;;; UDP Conn Limit
chain=forward action=drop protocol=udp dst-port=!53 connection-limit=3,32

2 ;;; High Port Conn Limit - 10 conn
chain=forward action=drop tcp-flags=syn protocol=tcp dst-port=1024-65535
connection-limit=10,32

0ldman · Thu Feb 09, 2012 10:48 pm

Thanks. I'm going to try those out.

Done a little differently than the rules I've tried.

mramos · Fri Feb 10, 2012 8:19 am

Hi ...

I saw this behaviour a couple of times on a 2,4AP (~30 CPEs), suddenly ping times rise from 1 .. 5ms to > 500ms and the only way to make it back was those turn around already mentioned: make all clients reconnect back.

I tried some setups to keep it stable and at least at a 20MHz BW channel on R52nM cards I settle down using only G mode, legacy speed selection, configured to only G speeds, distance = dynamic and adaptive noise immunity = off. No hw protection.

HW retries = between 4 and 7. Higher than that = higher ping times.

I use to run adaptive noise immunity = on and distance = 2Km 'til ROS 5.0X but after - I don't remember - 5.5 under such setup I started to face this ping time jumps.

To be honest no conclusion except I keep adaptive noise off, hw retries < 7 and data rate = legacy on 20MHz channel. On 10MHz channels distance = 4Km, adaptive noise immunity = on, only G mode and configured data rates (legacy).

This AP uses 3 freq on 2.4 (is a 433UAH with 3 x R52nM) and handle ~30 CPEs each frequency (access list have 92 UBNT CPEs).

Regards;

christyjame · Sat Feb 11, 2012 9:44 pm

Hi ...

I saw this behaviour a couple of times on a 2,4AP (~30 CPEs), suddenly ping times rise from 1 .. 5ms to > 500ms and the only way to make it back was those turn around already mentioned: make all clients reconnect back.

I tried some setups to keep it stable and at least at a 20MHz BW channel on R52nM cards I settle down using only G mode, legacy speed selection, configured to only G speeds, distance = dynamic and adaptive noise immunity = off. No hw protection.

HW retries = between 4 and 7. Higher than that = higher ping times.

I use to run adaptive noise immunity = on and distance = 2Km 'til ROS 5.0X but after - I don't remember - 5.5 under such setup I started to face this ping time jumps.

To be honest no conclusion except I keep adaptive noise off, hw retries < 7 and data rate = legacy on 20MHz channel. On 10MHz channels distance = 4Km, adaptive noise immunity = on, only G mode and configured data rates (legacy).

This AP uses 3 freq on 2.4 (is a 433UAH with 3 x R52nM) and handle ~30 CPEs each frequency (access list have 92 UBNT CPEs).

Regards;

Thanks for your valuable advices . . .
I've try to do this friend,

baasit · Mon Feb 13, 2012 12:34 am

this was a gud discussion

ur problem is HIDDEN NODE n u cant do anything about it untill u shift to tdma. some of your clients cant see each other so if they start transmission together collisions will occur at ur AP (ur AP can listen to one client at a time)

here are some suggestions
-ur AP can see all the clients so turn on the "CTS to SELF" on AP
-all of ur clients cant see each other so turn on rts/cts on ur cpes ( i m also using tp-link products which are realy weak but cheap)
-while installing ur client end devices try to give them as much height as possible so they can see each other

Finally dont put emphasis on a large ptmp networks (if u want weak and cheap cpe to work). instead of one AP add many APs
ur life will b easy

CyberTod · Mon Feb 13, 2012 10:47 am

So what is better in your opinion - cts to self or rts/cts. Yes the clients do not see each other very well so it very well could be hidden node problem. I have tried setting rts/cts on ap and 512 threshold. On the tp-link clients there is no way to turn it on/off but there is a threshold value so i guess it is always turned on. The default value is 2346. I have changed it to 512 too, but not on all devices. Is it a problem if on some of them it stays 2346 and on others 512 ?
Also i have enabled wmm just to see if it makes any difference. I dont see improvement, but dont see it going worse either.

baasit · Mon Feb 13, 2012 10:06 pm

WMM is not related to hidden node it just sets the priorities for differnt traffic
i m also fighting with this hidden node issue

use following

on AP cts to self, threshold=0
on clients rts/cts threshold=32

the only solution for me to this problem is to shift to TDMA

baasit · Mon Feb 13, 2012 10:12 pm

or add more APs a small coverage area will work definitly better as client devices will be able to see each other

i m fed up with tp-link

draguzet · Tue Mar 06, 2012 11:24 am

Hi guys !

I have same situation, problem are escalating to me over time

I also see that Bittorrent kil AP with connections, and open Topic recently: http://forum.mikrotik.com/viewtopic.php?f=14&t=59823

We have for redundancy dubble setup, 2 x 2.4 for clients, 2x5 Ghz for connection with central location, normally on separated 433AH.
For testing I try to transfer some clients on "backup" AP, but if only 2 clients are on AP, problem persist

Here is ping graphs...

draguzet · Mon Mar 12, 2012 10:15 pm

Hi !

I have news about high latency...but I don't know what is reason for this behavior.
I power up Snooper on another card, and see that usage of Freq. are high on this time high ping, but is not visible that is any client using it, because is on same MAC as AP card is ?? Picture in attach !
What might this be ?

BAND1C00T · Sun Jan 18, 2015 4:48 pm

I have the samw problem on 951g-2hnd
after 2 years no solution found...

saintofinternet · Mon Mar 30, 2015 4:10 pm

normis... please help!!!

i upgraded to ROS 6.27 and now i am facing real bad latency on WiFi 802.11

the ping timeout is starting from 1ms and going to 1000ms....

what can be done... this really getting bad for me..

saintofinternet · Mon Mar 30, 2015 7:58 pm

now i changed the "HT Guard Interval" value to "LONG" and it gave me some what better stability... but still there is a surge. check the the screenshot attached.

roserror-1.png

CyberTod · Mon Mar 30, 2015 9:57 pm

This is a very old topic of mine, but here is what I did to improve things for me :
Using default rates, previously was using only-g. Started using wireless-fp package. Made some wireless rules to limit number of connections.
Mine are all ptmp links. I have quite good results now, but still sometimes there are times with high latency and this is mainly with some client having rx-rate of 1mbit. This is the only thing I don't know why is happening. Maybe missing management frames and reducing rate. But I have given up to expect better because this is plain 802.11 and the protocol itself has problem with hidden nodes and so on ..

saintofinternet · Tue Mar 31, 2015 3:59 am

This is a very old topic of mine, but here is what I did to improve things for me :
Using default rates, previously was using only-g. Started using wireless-fp package. Made some wireless rules to limit number of connections.
Mine are all ptmp links. I have quite good results now, but still sometimes there are times with high latency and this is mainly with some client having rx-rate of 1mbit. This is the only thing I don't know why is happening. Maybe missing management frames and reducing rate. But I have given up to expect better because this is plain 802.11 and the protocol itself has problem with hidden nodes and so on ..

can you please share your rules for limiting connections....

ironically it happens even when i have one client connected...

CyberTod · Tue Mar 31, 2015 9:29 am

With 1 client and a good signal never had problems. Here are some of the rules, I have more but they are a bit specific for my network :

/ip firewall filter add action=add-src-to-address-list address-list="udp limit" address-list-timeout=1m chain=forward connection-limit=4,32 dst-port=!53 protocol=udp
/ip firewall filter add action=drop chain=forward connection-limit=4,32 dst-port=!53 protocol=udp
/ip firewall filter add action=add-src-to-address-list address-list="tcp limit" address-list-timeout=1m chain=forward connection-limit=11,32 dst-port=1024-65535 protocol=tcp tcp-flags=syn
/ip firewall filter add action=drop chain=forward connection-limit=11,32 dst-port=1024-65535 protocol=tcp tcp-flags=syn

The rules also include a 'src-address=' for my network, because otherwise sometimes there are problems with the service. You can play a bit with the 'connection-limit' if needed.

Low throughput and high latency on 2,4ghz AP after some time

Low throughput and high latency on 2,4ghz AP after some time

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