Cisco DX650, Руководство администратора

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Access Point Association
At startup, the Cisco Desktop Collaboration Experience DX650 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:
• 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.
• 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.
The Cisco Desktop Collaboration Experience DX650 associates with the AP that has the highest RSSI and
lowest channel-usage values (QBSS) that possess matching Service Set Identifier (SSID) and encryption
types. To ensure that voice traffic is handled properly, you must configure the correct QoS in the AP.
Related Topics
Voice QoS in Wireless Network, on page 83
Security for Voice Communications in WLANs, on page 86
VoIP WLAN Deployment, on page 93
Voice QoS in 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 can seriously impact 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 as they travel across the network. Also, use a
separate VLAN for data traffic, not the default native VLAN that 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:
• Voice/Video VLAN - Voice traffic to and from Cisco Desktop Collaboration Experience
• Data VLAN - Data traffic to and from other wireless devices
• Native VLAN - AP management
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, which results in lower packet delay and fewer lost
packets.
Cisco Desktop Collaboration Experience DX650 Administration Guide, Release 10.1(1)
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VoIP Wireless Network Components