Dell 6.2 ARM Sup port for 802.11n, Monitoring Y our Network w ith ARM

347| Adaptive Radio Mana gement (ARM ) DellPowerConnect W- Series ArubaOS 6.2 | User Guide

ARM Sup port for 802.11n

ArubaOSversion 3.3.x or later supports APs with the 802.11n standard, ensuringseamless integration of 802.11n

devices into your RF domain.The Dell AP’s 5 Ghz band capacity simplifies the integration of newA Ps into your

legacy network.You can also replace olderA Ps with newer8 02.11n-compliant APs while reusingyour existing cabling

and PoE infrastructure.

A high-throughput(802.11n) AP can use a 40 MHz channelpair comprised of two adjacent 20 MHz channels

availablei n the regulatorydomain profile for your country. When ARM is c onfiguredfor a dual-band AP, it wi ll

dynamicallyselect t he primaryand seco ndarychannels for these devices. It can, however, continue to scan all changes

in the a+b/g bandst o calculate interferenceand detect rogue APs.

Monitoring Y our Network w ith ARM

WhenAR M is enabled,t he Dell AP dynamically scans all 802.11 channels in its regulatory domain at regular

intervalsand will report everything it sees to the controlleron each channeli t scans.(By default, 802.11n-capable

APs scan channelsin all regulatory domains.)This includes, but is not limited to, data regardingWLAN coverage,

interference,and intrusion detection. You can retrieve this information from the controller to get a quick health

check of your WLAN deploymentw ithout having to walk around everypart o f a buildingwi th a network analyzer.

(For additional information on the individual matrix gathered on the AP’s current assigned RF channel,see “"AR M

Metrics" on page 361.)

The defaultAR M scanning intervali s determined by the scan-interval parameter in the ARM profile. If the AP does

not have anyass ociated clients (ori fmo st of its clients arei nactive) the ARM featurewill dynamically readjust this

defaultscan i nterval,allowing the AP obtain better information about its R F neighborhoodby scanning non-home

channelsmore frequently. Starting with ArubaOS 6.2, if an AP att empts to scan a non-home channel but is

unsuccessful,the AP will make additional attempts to rescan that channel before skipping it and continuing on to

other channels.

Dell APs keep a count of the number of data bytes transmitted and received by their radios to calculate the traffic

load.When a WLAN gets very busy and traffic exceeds a predefinedthreshold, load-aware ARM dynamicallyadjusts

scanningbehavior t o maintain uninterrupteddata transfero n heavily loadedsy stems. ARM-enabledA Ps will resume

their complete monitoring scans when the traffic has dropped to normal levels. You can also define a firewall policy

that pauses ARM scanning when the AP detects crit ically important or latency-sensitive traffic from a specified host

or network.

ARM’s band steering featureencourages dual-bandc apableclients to stay on the 5GHz band on dual-bandA Ps. This

freesup resources on the 2.4GHz band for single band clients like VoIP phones.

The ARM “Mode Aware” option is a useful feature forsi ngleradio, dual-band WLAN networks with high density AP

deployments.If t hereis to o muchA P coverage,t hose APs can cause interferenceand negatively impact your

network.Mode aware A RM can turn APs into Air Monit ors if necessary, then turn those Air Monitors back into A Ps

whent hey detect gaps in coverage. Note that an Air Monitor wi llnot turn back into an AP if it detects client traffic

(or client traffic increases), but will change to an AP only if i t detects coverage holes.