Specifications

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Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
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Chapter 2 An Overview of the Voice Over IP Wireless Network
Components of the VoIP Wireless Network
treatment for voice packets when traveling across the network. Also, use a
separate VLAN for data traffic, not the default native VLAN which is typically
used for all network devices.
You need the following VLANs on the network switches and the access points that
support voice connections on the WLAN.
• Voice VLAN—Voice traffic to and from the wireless IP phone
• Data VLAN—Data traffic to and from the wireless PC
• Native VLAN—Data traffic to and from other wireless devices
Assign separate SSIDs to the voice and to the data VLANs. If you configure a
separate management VLAN in the WLAN, do not associate an SSID with the
management VLAN.
By separating the phones onto a voice VLAN and marking voice packets with
higher CoS, you can ensure that voice traffic gets priority treatment over data
traffic resulting in lower packet delay and fewer lost packets.
Unlike wired networks with dedicated bandwidths, wireless LANs have to
consider traffic direction when implementing QoS. Traffic is classified as
upstream or downstream from the point of view of the access point as shown in
Figure 2-2.
Figure 2-2 Voice Traffic in a Wireless Network
Beginning with Cisco IOS release 12.2(11)JA, Cisco Aironet APs support the
contention-based channel access mechanism called Enhanced Distributed
Coordination Function (EDCF). The EDCF-type of QoS has up to eight queues
for downstream (toward the 802.11b/g clients) QoS. You can allocate the queues
based on these options:
• QoS or Differentiated Services Code Point (DSCP) settings for the packets
• Layer 2 or Layer 3 access lists
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Downstream
Upstream
Downstream
Upstream
Network
Downstream QoS only
Bi-Directional QoS