Radio Qos Policy - Motorola AP-6511 Reference Manual

Motorola Solutions AP-6511 Access Point System Reference Guide

6.3 Radio QoS Policy

Without a dedicated QoS policy, a network operates on a best-effort delivery basis, meaning all traffic has
equal priority and an equal chance of being delivered in a timely manner. When congestion occurs, all traffic
has an equal chance of being dropped!
When configuring a QoS policy for a radio, select specific network traffic, prioritize it, and use congestion-
management and congestion-avoidance techniques to provide deployment cusomizations best suited to each
QoS policy's intended wireless client base.
Motorola Solutions Access Point radios and wireless clients support several Quality of Service (QoS)
techniques enabling real-time applications (such as voice and video) to co-exist simultaneously with lower
priority background applications (such as Web, Email and file transfers). A well designed QoS policy should:
• Classify and mark data traffic to accurately prioritize and segregate it (by access category) throughout the
network.
• Minimize the network delay and jitter for latency sensitive traffic.
• Ensure higher priority traffic has a better likelihood of delivery in the event of network congestion.
• Prevent the ineffective utilization of access points degrading session quality by configuring admission
control mechanisms within each radio QoS policy
Within a Motorola Solutions wireless network, wireless clients supporting low and high priority traffic
contend with one another for data resources. The IEEE 802.11e amendment has defined Enhanced
Distributed Channel Access (EDCA) mechanisms stating high priority traffic can access the network sooner
then lower priority traffic. The EDCA defines four traffic classes (or access categories); voice (highest), video
(next highest), best effort and background (lowest).The EDCA has defined a time interval for each traffic
class, known as the Transmit Opportunity (TXOP). The TXOP prevents traffic of a higher priority from
completely dominating the wireless medium, thus ensuring lower priority traffic is still supported by
connected radios.
IEEE 802.11e includes an advanced power saving technique called Unscheduled Automatic Power Save
Delivery (U-APSD) that provides a mechanism for wireless clients to retrieve packets buffered by an access
point. U-APSD reduces the amount of signaling frames sent from a client to retrieve buffered data from an
access point. U-APSD also allows access points to deliver buffered data frames as bursts, without backing-
off between data frames. These improvements are useful for voice clients, as they provide improved battery
life and call quality.
The Wi-Fi alliance has created Wireless Multimedia (WMM) and WMM Power Save (WMM-PS) certification
programs to ensure interoperability between 802.11e WLAN infrastructure implementations and wireless
clients. An AP-6511 managed wireless network supports both WMM and WMM-Power Save techniques.
WMM and WMM-PS (U-APSD) are enabled by default in each WLAN profile.
Enabling WMM support on a WLAN just advertises the WLAN's WMM capability and radio configuration to
wireless clients. The wireless clients must be also able to support WMM and use the values correctly while
accessing WLAN to benefit.
WMM includes advanced parameters (CWMin, CWMax, AIFSN and TXOP) specifing back-off duration and
inter-frame spacing when accessing the network. These parameters are relevant to both connected access
point radios and their wireless clients. Parameters impacting access point transmissions to their clients are
controlled using per radio WMM settings, while parameters used by wireless clients are controlled by a
WLAN's WMM settings.
An AP-6511 supports static QoS mechanisms per WLAN to provide prioritization of WLAN traffic when
legacy (non WMM) clients are deployed. An AP-6511 Access Point allows flexible WLAN mapping with a
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