Traffic Classification (TCLAS). Cisco Video Phone 8875 , IP Phone 8800 Series

If the admission is refused for an inbound call there is no messaging from the Cisco IP Conference Phone 8832 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 IP Conference Phone 8832 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 enabled, then the Cisco IP Conference

Phone 8832 will send an ADDTS request during the roam to the new access point, which embedded in the reassociation request frame.

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.

Using port based QoS policies is inadequate for CAPWAP based wireless LAN solutions as all data packets use the same UDP port (CAPWAP = UDP 5246) and the access point uses the outside QoS marking to determine which queue the packets should be placed in.

With TCLAS, DSCP preservation is not a requirement.

Call Admission Control must be enabled on the access point in order to enable TCLAS.

TCLAS will be negotiated within the ADDTS packets, which are used to request bandwidth in order to place or receive a call.

QoS Basic Service Set (QBSS)

There are three different versions of QoS Basic Service Set (QBSS) that the Cisco IP Conference Phone 8832 supports.

The first version from Cisco was on a 0-100 scale and was not based on clear channel assessment (CCA), so it does not account for channel utilization, but only the 802.11 traffic traversing that individual access point’s radio. So it does not account for other 802.11 energy or interferers using the same frequencies.

QBSS is also a part of 802.11e, which is on a 0-255 scale and is CCA based. So this gives a true representation on how busy the channel is. The max threshold is also defined on the client side, which is set to 105.

The second version from Cisco is based on the 802.11e version, but allows the default max threshold of 105 to be optionally configured.

Each version of QBSS can be optionally be configured on the access point.

Wired QoS

Configure QoS settings and policies for the necessary network devices.

Cisco IP Conference Phone 8832 Wireless LAN Deployment Guide

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