Avaya Communication Server 1000 Installation And Commissioning Manual page 231

- Assign all devices in this VLAN to one subnet.
There are other access point parameters necessary for the proper operation of voice
communications. Often, these are not adjustable. By specifying IP protocol 119 the following
parameters are enabled on the voice path in the access point:
• Voice packet retry limit of three
If a voice packet is not ACKed, it is retried three times and then dropped. This parameter
must be enabled in the code to be able to control the number of packet retries and limit
them to three. There are access points that identify IP protocol 119 (SpectraLink voice
packets), to limit packet retries to three and other access points simply identify voice
transmissions to limit retries.
• Round Robin Queuing
During voice packet retry transmissions, the AP can also transmit other voice packets in
the queue. This ability prevents other wireless telephones that use the AP from having
their voice communications held up while retries occur. This causes all other wireless
telephones to have poor audio while one wireless telephone is in a retry state.
These parameters can be invoked by specifying the voice profile or IP protocol 119 < 10 ms
latency. Disable the following parameters:
• Dynamic Transmit Power at the Control (DTPC) for wireless clients
• AP Dynamic TX Power (or configure to On Demand Only)
• AP Dynamic Channel Select (or configure to On Demand Only)
• Intrusion Detection System (IDS) involvement
IDS causes the AP to go off channel and listen for other wireless clients and APs. This
causes degraded voice quality.
• Load balancing at the AP for clients and network
• Interference detection and avoidance
• Coverage hole detection and correction
• Client Holdoff Time
• EAP or MAC Reauthentication interval
• TKIP MIC Failure Holdoff Time
Avaya WLAN IP Telephony Installation and Commissioning
• Ideally, there is no routing between any network devices used for voice
communication.
• If routing is necessary, keep it in the back-end, between the SVP and PBX Call
Server. Keep routing short and quick.
Quality of Service checklist for voice over WLAN applications
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