7920 on AP1230 --> Network busy

[f-vanryckeghem]

Hi, here is my lab

on Cat 3524 where

an AP1230 is connected

an ACS server is connected

two 7920 wireless Ip phones

One laptop with a Cisco Wireless PCMCIA card

I have setup QOS on the AP to prioritarize Radius, voice RTP and signalling packets.

I have setup QBSS

But my big trouble is the following :

when massive FTP traffic is passing through the AP

even with QOS activated ... a Wireless phone could not establish a phone converstation .. I have the following message on the 7920 : Network Busy

a call estalishment between a fixed Ip phone and a Wireless ip Phone is possible

I thing that it is because the phone see that the Channel utilization has a value of ... 81

RSSI is correct : 51

there is no other device connected to the wlan.

Any clue to avoid this ?

For me it is a big problem because it means that if a Wlan is heavility loaded ... a 7920 could not establish a communication anymore ...

Regards

frederic

[schunt]

Have you tried configuring a Voice only VLAN on the AP and the switch?

Scott

[g.rienstra]

What softwareversions are you using on the 7920 and AP ?

[f-vanryckeghem]

hi,

I am using the latest version right now

firmware 1.06 on the phones and 12.2.13JA1 on the AP

But after discussing with cisco guys and reading all the cisco docs ...

it seems ... to work as designed ....;-)

Answer of cisco, if your AP is too much utilized, the phone will initiate roaming on the nearest AP with a lower Channel Utilization.

I am not convinced ... but I have nothing to say in the Cisco design ...

[michaelgillespie]

You will get this message if the AP's channel utilization reaches 45%. The AP sends this info via QBSS, which the 7920 uses for roaming as well. Traffic can increase this value as well as radio interference. If traffic is causing this, you may need to install additional APs for load-balancing.

[Ivan Villagomez]

Hi, i have the same problem but my network topology is a little diff.

I have 6 AP 1230AG with only 10 7920 IP Phones, even with just 2 or 3 phones associated to my AP i get network busy.

I using the latest phone firmware (2.0) and the AP have the 12.3.7AJ2.

The only wireless clients that i have are the 10 7920 phones.

[michaelgillespie]

If the QBSS values in site survey are above 105, then will get network busy. This means the channel is very utilized. This is for outbound CAC. If no 802.11 traffic and is >= 25 or so, then need to take a look to see what other non-802.11 devices are in the area.

[michaelgillespie]

If using 12.3(7)JA or higher can manage that max threshold as well via a hidden command (dot11 phone cac-threshold X).

Default is 105. Not advised to change this as it may impact voice quality, but the option is there if the admin would like to increase or decrease this value.