AP Channel selection with no Radio Resource Provision

[fjulianom]

Hi guys,

I know if I enable Radio Resource Provision under FortiAP profiles, the APs will scan the frequency range and select the channel with less interference between the other APs, this is well documented in Deploying Wireless Network Guide.

But what happens if this feature is not enabled? I have several APs working with this feature disabled:

The APs have selected a channel, some on channel 1, some on channel 11... Do you know what the criteria or algorithm is for this channel selection?

Regards,

Julián

[Ahslan · Accepted solution]

My understanding is that when an AP initially boots up , it automatically does a scan of the environment and based off of that, selects a channel (unless the channel was manually configured). If the "radio resource provision" feature is enabled, it will continue to do this type of scan periodically (by default, every 30 mins). You can adjust the frequency of how often this scan is done via the CLI:

http://help.fortinet.com/fos50hlp/54/Content/FortiOS/fortigate-wireless-54/wifi-arrp.htm

Hope that helps!

[Ahslan · Accepted solution]

fjulianom wrote:

...I have enabled this feature for my FortiAPs and they are changing the channels very often, but I don't know if they change channels always they find bettter channels or only if they find better channels and have no associated clients.

Regards,

Julián 

If DARRP is enabled, then i believe even if clients are connected, the AP will change channels at the set interval (would be awesome if someone from fortinet could confirm but I'm pretty sure this is right). This is why it is important to change the frequency of this scan to some time period that is normally quiet (for example, 3AM).

[bravishank_FTNT · Accepted solution]

Yes, even with Clients connected to the FAP, once DARRP Optimization kicks in, FAP will be forced to change the channel.

However FAP will send CSA on the last 5 Beacons of the current channel before changing to the newer channel.

[Sumanth_FTNT · Accepted solution]

>>But what happens if this feature is not enabled?

If the DARRP is not selected the AP hooks on to one channel forever with which it came up during bootup process. There is no channel optimization algorithm running in background that calculates the interference & suggests the AP's to move to better channel if available.

[Sumanth_FTNT · Accepted solution]

During bootup/startup its not random but we do support DFS ( Dynamic Frequency Selection) based on background algorithm where we passively scan for and select the least congested channel.

[fjulianom]

Hi guys,

Any idea?

Regards,

Julián

[fjulianom]

Hi everyone,

Has anyone hands-on experience with the "Radio Resource Provision" feature? I have enabled this feature for my FortiAPs but they are changing the channels very often. Is this normal behaviour? Do the FortiAPs change channels when they have clients associated?

Regards,

Julián

[Ahslan · Accepted solution]

My understanding is that when an AP initially boots up , it automatically does a scan of the environment and based off of that, selects a channel (unless the channel was manually configured). If the "radio resource provision" feature is enabled, it will continue to do this type of scan periodically (by default, every 30 mins). You can adjust the frequency of how often this scan is done via the CLI:

http://help.fortinet.com/fos50hlp/54/Content/FortiOS/fortigate-wireless-54/wifi-arrp.htm

Hope that helps!

[fjulianom]

Hi Ashlan,

Yeah, my understanding is the same and it is explained in the link you provided. But my question is if the FortiAPs change channels even if they have associated clients when they find a new better channel (and by default, every 30 mins). I have enabled this feature for my FortiAPs and they are changing the channels very often, but I don't know if they change channels always they find bettter channels or only if they find better channels and have no associated clients.

Regards,

Julián 

[Ahslan · Accepted solution]

fjulianom wrote:

...I have enabled this feature for my FortiAPs and they are changing the channels very often, but I don't know if they change channels always they find bettter channels or only if they find better channels and have no associated clients.

Regards,

Julián 

If DARRP is enabled, then i believe even if clients are connected, the AP will change channels at the set interval (would be awesome if someone from fortinet could confirm but I'm pretty sure this is right). This is why it is important to change the frequency of this scan to some time period that is normally quiet (for example, 3AM).

[bravishank_FTNT · Accepted solution]

Yes, even with Clients connected to the FAP, once DARRP Optimization kicks in, FAP will be forced to change the channel.

However FAP will send CSA on the last 5 Beacons of the current channel before changing to the newer channel.

[Ahslan]

Balaji Ravishankar wrote:

Yes, even with Clients connected to the FAP, once DARRP Optimization kicks in, FAP will be forced to change the channel.

However FAP will send CSA on the last 5 Beacons of the current channel before changing to the newer channel.

Thanks

[fjulianom]

Hi guys,

Yeah, because I suspected the AP changes channel even with associated clients, I set the ARRP optimizacion to occur at fixed time every day at 7am. Thanks for confirming.

But what if the clients doesn't support CSA? I think it would be better the AP doesn't change channels with associated clients, like other vendors do.

Regards,

Julián

[Sumanth_FTNT · Accepted solution]

>>But what happens if this feature is not enabled?

If the DARRP is not selected the AP hooks on to one channel forever with which it came up during bootup process. There is no channel optimization algorithm running in background that calculates the interference & suggests the AP's to move to better channel if available.