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mrb
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WDS Mesh performing poorly

Wed Feb 06, 2013 2:47 pm

Hi all! My first post here!

The problems are that packets are dropped suddenly, sometimes in a succession. Round trip times vary widely (5ms-150ms) and are quite erratic. Occasionally, an AP becomes unreachable via network, but at the same time it is visible to other devices in their registration tables. Speed that clients can reach through mesh are between 2 and 6 mbit/s (and I've seen 13 mbit/s once).

To be honest, this is the first WDS mesh I've built, hence I have no idea what kind of behavior and performance I should expect from this kind of configuration. I've learned that there are better protocols used for communication between APs (nstream, nv2) but then APs are not visible to wifi-enabled consumer electronics.

My goal is to provide about 25-30 clients with "fast" internet access. This is kind of "modern" office where everybody uses devices without ethernet connectivity (and perhaps only 3-4 devices could be connected that way if we really did pull cables everywhere). I didn't think WDS mesh would be a silver bullet (that much I could figure out by reading and by using common sense) but I had no idea it would be this "bad". I put 'bad' under quotes because it's not like this setup doesn't work at all, but that performance is not that good, when compared to 3-4 devices on a single AP sharing same ISP connection.

I have 4x RB951-2n devices, connected with each other into a mesh, exactly as in this image:

Image

The only difference is that physical bridge between ethernet and wds is on device number 1 (as opposed to number 4 in above image). My devices are named AP1 through AP4.

All devices are running 5.23.

This installation is done in our offices, located in a combined residental/business building. There are about 20 visible APs with signal level above -100dBm with varying signal strengths across the office. Strongest ones are on channels 1, 6 and 11.

Devices are spread as evenly as possible, across the office space. Signal strengths between APs (obtained using /interface wireless registration-table print):

- AP1
 # INTERFACE         RADIO-NAME       MAC-ADDRESS       AP  SIGNAL-STRENGTH TX-RATE UPTIME              
 0 wlan1             AP3              D4:CA:6D:xx:xx:xx yes -74dBm@1Mbps    18.0... 12m30s              
 1 wlan1             AP4              D4:CA:6D:xx:xx:xx yes -65dBm@1Mbps    48.0... 12m29s              
 2 wlan1             AP2              D4:CA:6D:xx:xx:xx yes -63dBm@1Mbps    24.0... 12m29s           
- AP2
 # INTERFACE         RADIO-NAME       MAC-ADDRESS       AP  SIGNAL-STRENGTH TX-RATE UPTIME              
 0 wlan1                              E4:CE:8F:62:DC:EB no  -55dBm@1Mbps    54.0... 1h12m7s             
 1 wlan1                              DC:85:DE:3A:A5:DC no  -76dBm@1Mbps    54.0... 1h11m35s            
 2 wlan1             AP4              D4:CA:6D:xx:xx:xx yes -80dBm@1Mbps    36.0... 1h11m30s            
 3 wlan1             AP3              D4:CA:6D:xx:xx:xx yes -69dBm@1Mbps    11.0... 1h10m26s            
 4 wlan1             AP1              D4:CA:6D:xx:xx:xx yes -79dBm@1Mbps    48.0... 14m8s              
- AP3
 # INTERFACE         RADIO-NAME       MAC-ADDRESS       AP  SIGNAL-STRENGTH TX-RATE UPTIME              
 0 wlan1             AP4              D4:CA:6D:xx:xx:xx yes -84dBm@1Mbps    11.0... 1h12m7s             
 1 wlan1             AP2              D4:CA:6D:xx:xx:xx yes -80dBm@1Mbps    48.0... 1h12m7s             
 2 wlan1             AP1              D4:CA:6D:xx:xx:xx yes -85dBm@1Mbps    24.0... 15m49s      
- AP4
 # INTERFACE         RADIO-NAME       MAC-ADDRESS       AP  SIGNAL-STRENGTH TX-RATE UPTIME              
 0 wlan1             AP2              D4:CA:6D:xx:xx:xx yes -75dBm@1Mbps    24.0... 1h11m35s            
 1 wlan1             AP3              D4:CA:6D:xx:xx:xx yes -79dBm@1Mbps    11.0... 1h10m31s            
 2 wlan1             AP1              D4:CA:6D:xx:xx:xx yes -66dBm@1Mbps    48.0... 14m13s        
Configuration used on all 4 devices (IP addresses, identity and radio name were adjusted for each AP):
/system identity
	set name=AP3
/system package
	disable user-manager
	disable ppp
	disable dhcp
	disable multicast
	disable hotspot
	disable routing
/interface ethernet
	set ether3 master-port=ether2
	set ether4 master-port=ether2
	set ether5 master-port=ether2
/system ntp client
	set enabled=yes mode=unicast primary-ntp="89.238.75.57" secondary-ntp="37.59.115.231"
/ip dns
	set servers="192.168.1.1" allow-remote-requests=no
/interface mesh
	add name=mesh1
/interface mesh port
	add mesh=mesh1 interface=ether1 port-type=auto
	add mesh=mesh1 interface=wlan1 port-type=auto
/interface wireless security-profiles
	add name=default-wpa2 mode=dynamic-keys authentication-types=wpa2-psk unicast-ciphers=aes-ccm \
		group-ciphers=aes-ccm wpa2-pre-shared-key=********
/interface wireless
	set wlan1 disabled=no ssid=MySSID band="2ghz-b/g" frequency=2422 mode=ap-bridge \
		security-profile=default-wpa2 hide-ssid=no wireless-protocol=any \
		wds-mode=dynamic-mesh wds-default-bridge=mesh1 radio-name=AP3
/interface wireless connect-list
	add connect=yes disabled=no interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx \
		security-profile=default signal-range=-120..120 ssid="" wireless-protocol=any
	add connect=yes disabled=no interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx \
		security-profile=default signal-range=-120..120 ssid="" wireless-protocol=any
	add connect=yes disabled=no interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx \
		security-profile=default signal-range=-120..120 ssid="" wireless-protocol=any
	add connect=yes disabled=no interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx \
		security-profile=default signal-range=-120..120 ssid="" wireless-protocol=any
/interface wireless access-list
	add ap-tx-limit=0 authentication=yes client-tx-limit=0 disabled=no forwarding=yes \
		interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx management-protection-key="" \
		private-algo=none private-key="" private-pre-shared-key="" signal-range=-120..120
	add ap-tx-limit=0 authentication=yes client-tx-limit=0 disabled=no forwarding=yes \
		interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx management-protection-key="" \
		private-algo=none private-key="" private-pre-shared-key="" signal-range=-120..120
	add ap-tx-limit=0 authentication=yes client-tx-limit=0 disabled=no forwarding=yes \
		interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx management-protection-key="" \
		private-algo=none private-key="" private-pre-shared-key="" signal-range=-120..120
	add ap-tx-limit=0 authentication=yes client-tx-limit=0 disabled=no forwarding=yes \
		interface=wlan1 mac-address=D4:CA:6D:xx:xx:xx management-protection-key="" \
		private-algo=none private-key="" private-pre-shared-key="" signal-range=-120..120
/ip address
	add address="192.168.1.13/24" interface=mesh1
/ip route
	add gateway="192.168.1.1" dst-address="0.0.0.0/0"
I've disabled 802.11n on purpose - my guess was that it is much more sensitive to interference in a densely populated 2.4 ghz space and that most clients would keep switching between high and low speeds. I've been thinking of disabling 802.11g as well, but I wasn't so sure if it would help, and also if there were devices which are not backward-compatible with 802.11b.

Any help, advice, etc. would be highly appreciated! Thanks.
 
gnuttisch
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Re: WDS Mesh performing poorly

Fri Feb 08, 2013 10:21 am

We had 3 groove 2,4ghz connecting wireless to each other and had some problem like you in the beginning.

But after a few days of trying and testing we did the following.

Dished mesh and run bridge instead.
running wireless N 20MHz channel width.
VERY important to run on a clear freq.
disabled default forwarding.
staic WDS

thats all i remember at this time,
 
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shahbazian
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Re: WDS Mesh performing poorly

Fri Feb 08, 2013 10:26 pm

What appears at first glance that signal strength is poor in AP3.
To help select the clear channel use spectral history or spectral scan commands to get highest possible CCQ.
You don't need one connect list entry for each mac address, So you can replace all with one entry without any specific mac address for all wds.
You can select b/g/n band with 20/40MHz channel width for raise possible wireless data rate.
At this situation don't need add ether1 as mesh port on all APs just should on AP1, and in AP1 (AP that connected to ethernet network directly) do this:
/interface mesh mesh1 set mesh-portal=yes
Access list don't check for wds connectivity.
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TheWiFiGuy
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Re: WDS Mesh performing poorly

Sat Feb 09, 2013 6:43 pm

HWMP+ Mesh does not work properly, Static WDS is the best way, as soon as you use dynamic WDS or WDS MESH or HWMP+ all sorts of bridge loops occur. WDS was supposedly fixed in 5.18 , but not HWMP+ , when I rasied a ticket I was told it 'may get fixed' but no change logs show .
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uldis
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Re: WDS Mesh performing poorly

Tue Feb 12, 2013 3:51 pm

If you are using wireless encryption we suggest to contact support@mikrotik.com for a test release of v5.24rc1 which contains a fix for AES encryption speed.
After upgrade please reset wireless configuration and reconfigure wireless interface.
On the problem with speed and ping times. The problem is that each tome when WDS connection is made and wds interface added to the mesh port it needs to check the throughput of that wds link in order to set the path-cost. During that time the traffic is being generated over that WDS interface. If you reboot the router and when it comes back it creates 3 WDS links and it needs to send out traffic through all those 3 WDS links to detect the patch cost. At that time the wireless network is full (you will see lot of traffic on all the WDS interfaces) - during that time the ping times will increase a lot. After approx minute the WDS link throughput detection has finished and you see normal ping reply times.
One solution to avoid that is to manually set path-cost for each WDS interface in the mesh ports and after that disable wds-default-bridge option in the wireless interface. In this case the WDS link will not send out traffic to determine the path cost.
 
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TheWiFiGuy
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Re: WDS Mesh performing poorly

Tue Feb 12, 2013 9:54 pm

Thanks Uldis, will give the manual wds cost a go.
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mrb
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Re: WDS Mesh performing poorly

Thu Feb 14, 2013 10:37 pm

You don't need one connect list entry for each mac address, So you can replace all with one entry without any specific mac address for all wds.
How would that work? In other words, how would APs know which other APs to connect to?

How would that one entry look like?
 
mrb
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Re: WDS Mesh performing poorly

Thu Feb 14, 2013 11:11 pm

If you are using wireless encryption we suggest to contact support@mikrotik.com for a test release of v5.24rc1 which contains a fix for AES encryption speed.
After upgrade please reset wireless configuration and reconfigure wireless interface.
Thanks, I'll try it out. By the way, how is this fix supposed to manifest itself? Clients will be able to reach higher throughput or what?
 
tkgit
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Re: WDS Mesh performing poorly

Tue Feb 19, 2013 2:42 pm

i also use wds mesh (dynamic-mesh mode) in my network, all my routers (rb435g & rb433AH series) use 5.23 ROS.
the problem is, how mikrotik choose handover or client handle selection? some client in my network connect to more than 1 antenna or 1 AP at a same time, is that "as usually" in mikrotik?

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