Can any1 help me with a peculiar problem. I would hate to blame interference. I am working for a company that plans to deploy mikrotiks on a pretty big scale. We have our first base station up. On the tower we have 3 sectors, of which we are only using two. One sector is connected to a radio set at freq 2412 (channel 1) and the second radio at freq 2462 (channel 11). I have a virtual AP at 2412 (first radio) - called wlan2. The other two wireless interfaces are the master interfaces for the individual radios on the same mikrotik router. Thats the scenario. This is the problem: during the day all the links ping consistently (not too many drop outs ~ 5% packet loss at worst over 3000 packets and I wouldnt have complaints except for long round trip times (ping times ~ 50-300ms) on two of the 4 links connected to the one radio. This radio that provides for 4 wireless clients,3 of which are WDS links (AP-bridge) serves a metropolitan area, reasonably business oriented area. The radio that sits at 2462Mhz serves one client at the moment, again a wds link, because of prism card's incompetance as a station and inability to work well with WEP security, works perfectly, gr8 round trip times (ping times ~avg 6ms) and this is over a much greater distance compared to the others (8.5 km versus the furthest link on the other radio 3 km).

Here is my wireless config:

Flags: X - disabled, R - running
0 R name="wlan1" mtu=1500 mac-address=XX:XX:XX:XX:XX:XX arp=reply-only
disable-running-check=no interface-type=Atheros AR5413
radio-name="XX" mode=ap-bridge ssid="XXX1" area=""
frequency-mode=manual-txpower country=no_country_set antenna-gain=0
frequency=2412 band=2.4ghz-b/g scan-list=default rate-set=default
supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps
supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,
54Mbps
basic-rates-b=1Mbps,2Mbps basic-rates-a/g=6Mbps max-station-count=2007
ack-timeout=dynamic tx-power-mode=default noise-floor-threshold=default
periodic-calibration=enabled periodic-calibration-interval=60
burst-time=disabled dfs-mode=none antenna-mode=ant-a wds-mode=static
wds-default-bridge=bridge1 wds-default-cost=100 wds-cost-range=50-150
wds-ignore-ssid=no update-stats-interval=disabled
default-authentication=no default-forwarding=no default-ap-tx-limit=0
default-client-tx-limit=0 proprietary-extensions=pre-2.9.25
hide-ssid=no security-profile=default disconnect-timeout=3s
on-fail-retry-time=100ms preamble-mode=both compression=no
allow-sharedkey=no

1 R ;;; TkHs
name="wlan2" mtu=1500 mac-address=XX:XX:XX:XX:XX:ZZ arp=enabled
disable-running-check=no interface-type=virtual-AP
master-interface=wlan1 ssid="XX2" area="" max-station-count=2007
wds-mode=disabled wds-default-bridge=none wds-default-cost=0
wds-cost-range=0 wds-ignore-ssid=no default-authentication=yes
default-forwarding=yes default-ap-tx-limit=0 default-client-tx-limit=0
proprietary-extensions=pre-2.9.25 hide-ssid=no security-profile=default

2 R name="wlan4" mtu=1500 mac-address=XX:XX:XX:XX:XX:YY arp=enabled
disable-running-check=no interface-type=Prism prism-cardtype=200mW
radio-name="XXZZ" mode=ap-bridge ssid="ZZZ" area=""
frequency-mode=manual-txpower country=no_country_set antenna-gain=0
frequency=2462 band=2.4ghz-b scan-list=default rate-set=default
supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps basic-rates-b=1Mbps
max-station-count=2007 tx-power-mode=default
periodic-calibration=default periodic-calibration-interval=60
dfs-mode=none antenna-mode=ant-a wds-mode=static
wds-default-bridge=bridge3 wds-default-cost=100 wds-cost-range=50-150
wds-ignore-ssid=no update-stats-interval=disabled
default-authentication=no default-forwarding=no default-ap-tx-limit=0
default-client-tx-limit=0 proprietary-extensions=post-2.9.25
hide-ssid=no security-profile=default disconnect-timeout=3s
on-fail-retry-time=100ms compression=no allow-sharedkey=no

Can any1 help analyse where the problem may be at... any suggestions will be very helpful.

ps. I only recently changed the periodic calibration to enabled (from "default")

Thanks in advance,

mteck

what are the client radios? does the problem happen when more data is flowing?

the client radio is a prism 2.5, i havent got the config unfortunately, ad I cant get it coz the client has left for holiday. He turned off the AP, so cant run tests on it from base station end.

do you have to use WDS? / why are u using wds? as opposed to p-t p or mp bridge ...i ask bc we used to have a repeater setup between two wrap 2c's both with 8602 radios and would get all kinds if issues....we then put a 2nd card in the "repeater" and just did a bridge and then used the other radio to server hotspot clients.

EDIT: OH YEA: can you give us all your wireless info (i.e. distance of links..antennas, signal strenghts....freq. usage numbers.. what does a "scan" show on either client or master side??):

Back about a year or so ago I was having all sorts of problems with high ping times. They would start off low and get higher until it timed out. However closer to the antenna site everything worked ok. I tracked it down to the Prism cards having a fixed ACK timeout value. Less than about 7km ok, over that it did not work very well. 10km no good
Not sure if it is a similar issue but thought I would bring it up.
I fixed it by changing to SR2 cards.

Ok... to tackle the problem... i decided to modularise my approach... i came down to testing an atheros AR 5413 radio link with another of the same kind. Again using WDS... and discovered very large ping times, in the midst of a few short ones and then a log of timeouts. The signal strength is -87dB. The AP on our end picks up a number of APs:
2462 = -72dB
2462 = -22 dB
2462 = -95 dB
2462 = -94 dB
2462 = -90 dB
2462 = -93 dB
2462 = -84 dB
2437 = -85 dB
2437 = -86 dB
2412 = -61 dB
2412 = -81 dB
2412 = -73 dB
2412 = -86 dB
2412 = -83 dB
2422 = -87 dB
2432 = -82 dB
2432 = -91 dB
2417 = -95 dB
2417 = -85 dB
2417 = -91 dB
Frequency and signal strength

Client side has just 3 or 4 APs none in the same frequency as the transmit/rec freq (2412)


I have a prism 2.5 card communicating well with another one at -90 dB... at freq=2462Mhz, I get very good ping times... between 4 and 15ms... hardly any packet drops... but when I use an atheros AR 5413 in place of the prism connecting to another atheros at the office (config shown above), I get lots of packet drops, and very high ping times... and this is with a slightly better signal strength.

And the reason I am using wds is so that i'll be able to simulate a wired lin over a long distance and be able to use OSPF routing to create a mesh for alternate path routing.

And thanks guys for ur replies, although I'm still having the same problem.... think its atheros Ar 5413 cards... am looking at driver details...source code and the closed HAL for any hacks... not getting very far with this either. [/img]

If your signals are at or near -90dB you will very likely see ping problems as you are near the threshold of connectivity. I'm not sure why the Prism would work better other than the Atheros based card being more sensitive and seeing more noise and probably bouncing around on transmit rates. Can you increase the gain of one or both of the antennas in the link to improve the signal? Have you tried other channels besides 1 and 11 (like 3 or 9) to see if this changes anything? -87 for a signal is too low to expect a very reliable link and leaves very little headroom.