Users Guide

Understanding ARM Application Awareness
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 predefined threshold, load-aware ARM
dynamically adjusts scanning behavior to maintain uninterrupted data transfer on heavily loaded systems.
ARM-enabled APs 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 critically important or
latency-sensitive traffic from a specified host or network.
ARM’s band steering feature encourages dual-band capable clients to stay on the 5GHz band on dual-band
APs. This frees up resources on the 2.4GHz band for single band clients like VoIP phones.
The ARM “Mode Aware” option is a useful feature for single radio, dual-band WLAN networks with high density
AP deployments. If there is too much AP coverage, those APs can cause interference and negatively impact
your network. Mode aware ARM can turn APs into Air Monitors if necessary, then turn those Air Monitors back
into APs when they detect gaps in coverage. Note that an Air Monitor will not turn back into an AP if it detects
client traffic (or client traffic increases), but will change to an AP only if it detects coverage holes.
Client Match
The ARM client match feature continually monitors a client's RF neighborhood to provide ongoing client
bandsteering and load balancing, and enhanced AP reassignment for roaming mobile clients. This feature is
recommended over the legacy bandsteering and spectrum load balancing features, which, unlike client match,
do not trigger AP changes for clients already associated to an AP.
Legacy 802.11a/b/g devices do not support the client match feature. When you enable client match on 802.11n-
capable devices, the client match feature overrides any settings configured for the legacy bandsteering, station
handoff assist or load balancing features. 802.11ac-capable devices do not support the legacy bandsteering, station
hand off or load balancing settings, so these APs must be managed on using client match.
When you enable this feature on an AP, that AP is responsible for measuring the RF health of its associated
clients. The APreceives and collects information about clients in its neighborhood, and periodically sends this
information to the controller. The controller aggregates information it receives from all APs using client match,
and maintains information for all associated clients in a database. The controller shares this database with the
APs (for their associated clients), and the APs use the information to compute the client-based RF
neighborhood and determine which APs should be considered candidate APs for each client. When the
controller receives a client steer request from an AP, the controller identifies the optimal APcandidate and
manages the client’s relocation to the desired radio. This is an improvement from previous releases, where the
ARMfeature was managed exclusively by APs, without the larger perspective of the client's RFneighborhood.
The following client/AP mismatch conditions are managed by the client match feature:
l Load Balancing: Client match balances clients across APs on different channels, based upon the client
load on the APs and the SNR levels that the client detects from an underused AP. If an APradio can support
additional clients, the AP will participate in client match load balancing and clients can be directed to that AP
radio, subject to predefined SNRthresholds.
l Sticky Clients: The client match feature also helps mobile clients that tend to stay associated to an AP
despite low signal levels. APs using client match continually monitor the client's RSSI as it roams between
APs, and moves the client to an AP when a better radio match is found. This prevents mobile clients from
remaining associated to an APs with less than ideal RSSI, which can cause poor connectivity and reduce
performance for other clients associated with that AP.
l Band Steering/Band Balancing: APs using the client match feature monitor the RSSI for clients that
advertise a dual-band capability. If a client is currently associated to a 2.4 GHz radio and the AP detects that
the client has a good RSSIfrom the 5 Ghz radio, the controller attempts to steer the client to the 5 Ghz
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