Time critical data traffic such as voice and video benefit from QoS, which
can be configured to give voice and video higher priority. This allows for
smooth voice communication, jitter free video, and reliable delivery of E-Mail
configured with a lower priority.
QoS is disabled by default. The most
important guideline in QoS deployment is to be familiar with the traffic on the
wireless LAN. It is important to know the applications used by wireless client
devices, the delay sensitivity of the applications, and the amount of traffic
associated with the applications. QoS does not create additional bandwidth for
the wireless LAN. Rather it helps control the allocation of bandwidth. If there
is adequate bandwidth on the WLAN, QoS may not be needed.
QoS on the
wireless LAN focuses on downstream prioritization from the AP. Figure
shows the
upstream and downstream traffic flow. The radio downstream flow is traffic
transmitted out the AP radio to a wireless client device. This traffic is the
main focus for QoS on a wireless LAN. The radio upstream flow is traffic
transmitted out the wireless client device to the AP. QoS for wireless LANs
does not affect this traffic.
The Ethernet downstream flow is traffic
sent from a switch or a router to the Ethernet port on the AP. If QoS is
enabled on the switch or router, the switch or router might prioritize and
rate-limit traffic to the AP. The Ethernet upstream flow is traffic sent from
the AP Ethernet port to a switch or router on the wired LAN. The AP does not
prioritize traffic that it sends to the wired LAN based on traffic
classification.
When QoS is enabled, the AP queues packets based on the
Layer 2 class of service value for each packet. The AP applies QoS policies in
the order shown in Figure
. From
the Services > QoS Policies Page, configuring QoS is a two step
process
.
- Create/Edit the policy

- Apply the policy

The steps to configure QoS can be found in the Topics section of the
online AP Help or through the link below. The Traffic Class Definition page is
shown in Figure
along with the
common values in Figure
.
The
Advanced QoS page is shown in Figure
. If QoS Element
for Wireless Phones feature is enabled, traffic from wireless phone clients
have a higher priority than the rest of the clients. When Internet Group
Membership Protocol (IGMP) snooping is enabled on a switch and a client roams
from one AP to another, the client's multicast session is dropped. When
the IGMP snooping helper of the AP is enabled, the AP sends a general IGMP
query to the network infrastructure on behalf of the client every time the
client associates or reassociates to the AP. By doing so, the multicast stream
is maintained for the client as it roams. The Snooping Helper is enabled by
default. To disable, click the Disable selection and click Apply.