Configuring Voice Parameters In Indoor Mesh Networks - Cisco aironet 1522 Design And Deployment Manual

Client roaming is enabled by default.
Note

Configuring Voice Parameters in Indoor Mesh Networks

You can configure call admission control (CAC) and QoS on the controller to manage voice and video
quality on the mesh network.
The indoor mesh access points (1130 and 1240) are 802.11e capable, and QoS is supported on the local
2.4-GHz access radio and the 5-GHz backhaul radio. CAC is supported on the backhaul and the CCXv4
clients (which provides CAC between the mesh access point and the client).
Voice is only supported on indoor mesh networks.
Note
CAC
CAC enables a mesh access point to maintain controlled quality of service (QoS) when the wireless LAN
is experiencing congestion. The Wi-Fi Multimedia (WMM) protocol deployed in CCXv3 ensures
sufficient QoS as long as the wireless LAN is not congested. However, in order to maintain QoS under
differing network loads, CAC in CCXv4 or later is required.
CAC is supported in Cisco Compatible Extensions (CCX) v4 or later. Refer to Chapter 6 of the Cisco
Note
Wireless LAN Controller Configuration Guide, Release 5.2 at:
http://www.cisco.com/en/US/products/ps6366/products_installation_and_configuration_guides_list.html
Two types of CAC are available for access points: bandwidth-based CAC and load-based CAC. All calls
on a mesh network are bandwidth-based, so mesh access points use only bandwidth-based CAC.
Bandwidth-based, or static CAC enables the client to specify how much bandwidth or shared medium
time is required to accept a new call. Each access point determines whether it is capable of
accommodating a particular call by looking at the bandwidth available and compares it against the
bandwidth required for the call. If there is not enough bandwidth available to maintain the maximum
allowed number of calls with acceptable quality, the mesh access point rejects the call.
QoS and DSCP Marking
Cisco supports 802.11e on the local access and on the backhaul. Mesh access points prioritize user traffic
based on classification, and therefore all user traffic is treated on a best-effort basis.
Resources available to users of the mesh vary, according to the location within the mesh, and a
configuration that provides bandwidth limitation in one point of the network can result in
oversubscription in other parts of the network.
Similarly, limiting clients on their percentage of RF is not suitable for mesh clients. The limiting
resource is not the client WLAN, but the resources available on the mesh backhaul.
Similar to wired Ethernet networks, 802.11 WLANs employ Carrier Sense Multiple Access (CSMA),
but instead of using collision detection (CD), WLANs use collision avoidance (CA). This means that
instead of each station trying to transmit as soon as the medium is free, WLAN devices will use a
collision avoidance mechanism to prevent multiple stations from transmitting at the same time.
Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
Connecting the Cisco 1520 Series Mesh Access Point to Your Network
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