Brocade Mobility RFS Controller CLI Reference Guide (Supporting software release 5.5.0.0 and later) - Manual (Page 1079)

Brocade Mobility RFS Controller CLI Reference Guide 1071
53-1003098-01
Chapter
18
RADIO-QOS-POLICY
This chapter summarizes the radio QoS policy in the CLI command structure.
Configuring and implementing a radio QoS policy is essential for WLANs with heavy traffic and less
bandwidth. The policy enables you to provide preferential service to selected network traffic by
controlling bandwidth allocation. The radio QoS policy can be applied to VLANs configured on an
access point. In case no VLANs are configured, the radio QoS policy can be applied to an access
point’s Ethernet and radio ports.
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
customizations best suited to each QoS policy’s intended wireless client base.
A well designed QoS policy should:
• Classify and mark data traffic to accurately prioritize and segregate it (by access category)
throughout the network.
• Minimize 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 ineffective utilization of access points degrading session quality by configuring
admission control mechanisms within each radio QoS policy.
Within a Brocade wireless network, wireless clients supporting low and high priority traffic contend
with one another for access and 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.
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. A Brocade wireless network supports both WMM and
WMM-Power Save techniques. WMM and WMM-PS (U-APSD) are enabled by default in each WLAN
profile.