Associating To Aps; Voice Qos In A Wireless Network; Security For Voice Communications In Wlans; Voip Wlan Configuration - Cisco 7925G - Unified Wireless IP Phone VoIP Administration Manual

Components of the VoIP Wireless Network

Associating to APs

At startup, the Cisco Unified Wireless IP Phone 7925G scans for APs with SSIDs and encryption types
that it recognizes. The phone builds and maintains a list of eligible APs and uses the following variables
to determine the best AP.
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Note
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The wireless IP phone associates with the AP with the highest RSSI and lowest channel usage values
(QBSS) that have matching SSID and encryption types.To ensure that voice traffic is handled properly,
you must configure the correct QoS in the AP. For configuration information, see
Requirements for VoIP" section on page
Related Topics
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Voice QoS in a Wireless Network

Voice traffic on the Wireless LAN, like data traffic, is susceptible to delay, jitter, and packet loss. These
issues do not impact the data end user, but have serious implications for a voice call. To ensure that voice
traffic receives timely and reliable treatment with low delay and low jitter, you must use Quality of
Service (QoS), and use separate virtual LANs (VLANs) for voice and data. By isolating the voice traffic
onto a separate VLAN, you can use QoS to provide priority 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 APs that support voice connections on
the WLAN.
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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 into a voice VLAN and marking voice packets with higher QoS, you can ensure
that voice traffic gets priority treatment over data traffic resulting in lower packet delay and fewer lost
packets.
Cisco Unified Wireless IP Phone 7925G Administration Guide for Cisco Unified Communications Manager 7.0(1)
2-12
Received Signal Strength Indicator (RSSI)—Signal strength of available APs within the RF
coverage area. The phone attempts to associate with the AP with the highest RSSI value.
QoS Basic Service Set (QBSS)—Beacon information element (IE) that sends the channel usage of
the AP to the wireless IP phone. The phone uses the QBSS value to determine whether the AP can
effectively handle more traffic.
QBSS is not supported when using Wi-Fi 802.11a.
Traffic Specification (TSpec)—Calculation of call limits and WLAN load balancing. The TSpec
value of each voice stream allows the system to allocate bandwidth to voice devices on a first-come,
first-served basis. For more information, see
page 2-12.
Security for Voice Communications in WLANs, page 2-16
VoIP WLAN Configuration, page 2-21
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
Chapter 2
"Voice QoS in a Wireless Network" section on
2-21.
Overview of the VoIP Wireless Network
"Wireless Network
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