Specifications

Cisco Unified Wireless IP Phone 7921G Series Deployment Guide 27
refused, there is no messaging from the Cisco Unified Wireless IP Phone 7921G Series 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 Wireless IP Phone 7921G 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 wireless IP
phone will send an ADDTS request during the roam to the new access point.
For more information about Call Admission Control and QoS, refer to the “Cisco Unified Wireless Quality of Service” chapter
in the Enterprise Mobility Design Guide at this URL:
http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob41dg/eMob4.1.pdf
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.