Chapter 7 Configuring QoS on an Access Point
Configuration Guidelines
Cisco Wireless IP Phone 7920 Support
The Wireless IP Phone 7920 phone uses Cisco CDP message with Appliance
If VLAN is enabled, all phone clients should be associated to a single Voice VLAN. If VLAN is not enabled, we advise that all the VoIP packets be classified by using the same user_priority value (6).
The access point always uses DIFS with minimum contention window (CW) value derived from the CWmax and CWmin range parameters to prioritize voice traffic.
Radio Interface Transmit Queues
The radio maintains four priority queues, one for each traffic category, and 802.11e Enhanced DCF (EDCF) to provide differentiate Distributed Coordination Function (DCF) access to the wireless medium. An
Adjusting Radio Access Categories
The access point uses the radio access categories to calculate backoff times for each packet. As a rule,
The default values in the minimum and maximum contention window fields, and in the slot time fields are based on settings recommended in IEEE Draft Standard 802.11e. For detailed information on these values, consult the standard.
We recommend that you use the default settings. Changing these values can lead to unexpected blockages of traffic on your wireless LAN, and the blockages might be difficult to diagnose. If you change these values and find that you need to reset them to the default values.
The values listed in Table
Table | CWmin and CWmax Default Parameters |
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Priority |
| Fixed slottime Number | CWmin | CWmax |
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0 |
| 6 | 15 | 1023 |
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1 |
| 2 | 15 | 1023 |
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2 |
| 1 | 7 | 15 |
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3 |
| 1 | 3 | 7 |
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Cisco Wireless Router and HWIC Configuration Guide
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