Controller Based WLANs

What are types of channel and scanning enhancement added in 6.4.2.3?

Aruba Employee

Environment : This article is applicable to controllers running 6.4.2.3 or above

 

Channel priority and type
The priority of a channel is proportional to the likelihood that the channel has activity that we need to monitor and potentially act on.  The following list describes the order of priority of channels, and the frequency of visits will be higher based on their membership in one or more of these categories:

1.    “DOS channels”- Channels where we are actively containing devices in AM mode.  These are marked with an ‘O’ flag in the ARM CLI output (show ap arm scan-times).
2.    “Active channels”- Channels where AP activity has already been detected.  These are marked with an ‘A’ flag in the ARM CLI output. They are visited in all scan-modes.
3.    “Reg-domain channels” - The group of channels that are in the AP’s regulatory domain (the channels that are valid for use in the AP’s country). These are marked with a ‘C’ flag in the ARM CLI output.  They are visited in all scan modes.
4.    “All-Reg-domain channels” - The group of channels that belong to the regulatory domain of any country. These are marked with a ‘D’ flag in the ARM CLI output.  They are visited only if scan-mode is set to All-Reg or Rare.
5.    “Unconventional scan channels” – This new channel type category contains channels that belong to any country’s regulatory domain, but with an unconventional scan direction. Ex. 36+ and 40- have conventional scan directions, because 36 and 40 are part of a 40MHz channel pair, but 40+ is an unconventional scan direction because its direction is away from the pair channel. Channels where we do unconventional scans are marked with a ‘J’ or ‘M’ flag in the ARM CLI output. They are visited only if scan-mode is set to All-Reg or Rare.
6.    “Rare channels” - Channels that do not belong to any country’s regulatory domain. We call these rare channels and they are marked with a ‘Z’ flag in the ARM CLI output.  We only do rare channel scanning in AM mode, and only if ‘rare’ scan mode is selected in AM Scanning profile.


AP SCANNING OPTIMIZATION 
We have optimized scanning to provide a more effective RF monitoring.

  • Unconventional scans will only be done in all-reg and rare scan-modes, and will no longer done if scan-mode is set to reg-domain.
  • Group  Scanning.

 
 Unconventional scan means the direction is away from the pair channel. 
Ex. 40+, 44-, 48+, 52-, …
Before Optimization ,Unconventional scans are interspersed with conventional scans, such that both are done before moving on to the next channel. 
Ex. 36+, 40-, 40+, 44+, 44-, 48-, 48+, 52+, 52-, 56-,..
After Optimization Unconventional scans will only be done in all-reg and rare scan-modes,and will no longer done if scan-mode is set to reg-domain 
After Optimization unconventional scans are now run separately at a lower priority (lower frequency than All-reg, but higher frequency than Rare) which allows us to cycle through the conventional scans faster).

This optimization applies to both legacy,11N and 11ac APs, however, 11ac APs currently do not support unconventional, nor Rare channel scanning

Group scanning
Channel group scanning leverages the fact that the 11ac AP's radio can hear 20/40MHz frames on sub-channels when it does an 80MHz wide scan. Because of this, scanning can be optimized by putting channels into scan groups, which will be visited sequentially, each time selecting a new primary channel. This allows us to cycle through the list of channels faster, so that the delay between visits to a channel (group) is much smaller. 
A single 36E scan allows us to hear:
80MHz wide frames in the 36-48 channel width
40MHz wide frames in the 36+/40- channel width
40MHz wide frames in the 44+/48- channel width
20MHz wide frames on 36, 40, 44 and 48
This optimization applies only to 11ac APs

Scan Mode in AP mode
(config) #rf arm-profile default
 
Scan Mode in AM mode
(config) #rf am-scan-profile default

Group Scan output:
 #show ap arm scan-times ap-name ap225-sk

 The same existing CLI command used to show scan state for each channel, has been modified to now show a section containing scan group information when run on 11ac APs:

show ap arm scan-times ap-name <ap_name>

The following existing command is used to configure the scan mode in AP mode:

(Aruba3400) (config) #rf arm-profile default
(Aruba3400) (Adaptive Radio Management (ARM) profile "default") #scan-mode ?
all-reg-domain          Scan channels in all regulatory domains
reg-domain              Scan channels in AP's regulatory domain

The following existing command is used to configure the scan mode in AM mode:

(Aruba3400) (config) #rf am-scan-profile default
(Aruba3400) (AM Scanning profile "default") #scan-mode ?
all-reg-domain          Scan channels in all regulatory domains
rare                    Scan ALL channels (all regulatory domains and rare channels)
reg-domain              Scan channels in AP's regulatory domain

Version history
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Last update:
‎04-09-2015 04:48 AM
Updated by:
 
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