Pre-Call Admission Control; Roaming Admission Control; Traffic Classification (Tclas) - Cisco 9971 Deployment Manual

If CAC is enabled on the Cisco Autonomous Access Point, then SRTP and barge calls will fail.

Pre-Call Admission Control

If Call Admission Control (TSPEC) is enabled on the access point, the Cisco Unified IP Phone 9971 will send an Add Traffic
Stream (ADDTS) to the access point to request bandwidth in order to place or receive a call.
If the AP sends an ADDTS successful message then the Cisco Unified IP Phone 9971 establishes the call.
If the access point rejects the call and the Cisco Unified IP Phone 9971 has no other access point to roam to, then the phone will
display Network Busy.
If the admission is refused for an inbound call there is no messaging from the Cisco Unified IP Phone 9971 to inform the remote
endpoint that there is insufficient bandwidth to establish the call, so the call can continue to ring out within the system until the
remote user terminates the call.

Roaming Admission Control

During a call, the Cisco Unified IP Phone 9971 measures Received Signal Strength Indicator (RSSI) and Packet Error Rate
(PER) values for the current and all available access points to make roaming decisions.
If the original access point where the call was established had Call Admission Control (TSPEC) enabled, then the Cisco Unified
IP Phone 9971 will send an ADDTS request during the roam to the new access point, which embedded in the reassociation
request frame.
Note: Call Admission Control for video is currently not supported.

Traffic Classification (TCLAS)

Traffic Classification (TCLAS) helps to ensure that the access point properly classifies voice packets.
Without proper classification, voice packets will be treated as best effort, which will defeat the purpose of TSPEC and QoS in
general.
TCP and UDP port information will be used to set the UP (User Priority) value.
The previous method of classification depends upon preservation of DSCP value throughout the network, where the DSCP
value maps to a particular queue (BE, BK, VI, VO).
However, the DSCP values are not always preserved as this can be viewed as a security risk.
TCLAS is supported in the Cisco Unified Wireless LAN Controller release 5.1.151.0 and later.
Cisco Unified IP Phone 9971 Wireless LAN Deployment Guide
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