Interband Roaming; Multicast; Designing The Wireless Lan; Planning Channel Usage - Cisco 9971 Deployment Manual

Interband Roaming

The Cisco Unified IP Phone 9971 defaults to Auto for the frequency band mode, which enables interband roaming and gives
preference to 5 GHz over 2.4 GHz.
At power on, the Cisco Unified IP Phone 9971 will scan all 2.4 and 5 GHz channels when in Auto mode, then attempt to
associate to an access point for the configured network if available.
If configured for 802.11a only (5 GHz) or 802.11b only (2.4 GHz) mode, then just those channels are scanned.
It is recommended to perform a spectrum analysis to ensure that the desired bands can be enabled in order to perform interband
roaming.

Multicast

When enabling multicast in the wireless LAN, performance and capacity must be considered.
The Cisco Unified IP Phone 9971 is a client that primarily utilizes active mode, but if there is an associated client that is in
power save mode, then all multicast packets will be queued until the DTIM period.
With multicast, there is no guarantee that the packet will be received the by the client.
The multicast traffic will be sent at the highest mandatory / basic data rate enabled on the access point, so will want to ensure
that only the lowest enabled rate is configured as the only mandatory / basic rate.
The client will send the IGMP join request to receive that multicast stream. The client will send the IGMP leave when the
session is to be ended.
The Cisco Unified IP Phone 9971 supports the IGMP query feature, which can be used to reduce the amount of multicast traffic
on the wireless LAN when not necessary.
Ensure that IGMP snooping is also enabled on all switches.
It is recommended to enable Multicast Direct in the Cisco Unified Wireless LAN Controller.
Note: If using Coexistence where 802.11b/g and Bluetooth are being used simultaneously, then multicast voice is not
supported.

Designing the Wireless LAN

The following network design guidelines must be followed in order to accommodate for adequate coverage, call capacity and
seamless roaming for the Cisco Unified IP Phone 9971.

Planning Channel Usage

Use the following guidelines to plan channel usage for these wireless environments.

5 GHz (802.11a)

The Cisco Unified IP Phone 9971 supports Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) from
802.11h, which are required when using channels operating at 5.25 - 5.725 GHz, which are 15 of the 23 possible channels.
DFS dynamically instructs a transmitter to switch to another channel whenever radar signal is detected. If the access point
detects radar, the radio on the access point goes on hold for at least 60 seconds while the access point passively scans for
another usable channel.
Cisco Unified IP Phone 9971 Wireless LAN Deployment Guide
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