Cisco Cisco Access Registrar 4.2 Spezifikationen PDF herunterladen (Seite 148)

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Cisco Wireless LAN Controller Configuration Guide

OL-13826-01

Chapter 4 Configuring Controller SettingsWireless Device Access

Configuring Voice and Video Parameters

U-APSD

Unscheduled automatic power save delivery (U-APSD) is a QoS facility defined in IEEE 802.11e that

extends the battery life of mobile clients. In addition to extending battery life, this feature reduces the

latency of traffic flow delivered over the wireless media. Because U-APSD does not require the client to

poll each individual packet buffered at the access point, it allows delivery of multiple downlink packets

by sending a single uplink trigger packet. U-APSD is enabled automatically when WMM is enabled.

Traffic Stream Metrics

In a voice-over-wireless LAN (VoWLAN) deployment, traffic stream metrics (TSM) can be used to

monitor voice-related metrics on the client-access point air interface. It reports both packet latency and

packet loss. An administrator can isolate poor voice quality issues by studying these reports.

The metrics consist of a collection of uplink (client side) and downlink (access point side) statistics

between an access point and a client device that supports CCX v4 or later. If the client is not CCX v4 or

CCXv5 compliant, only downlink statistics are captured. The client and access point measure these

metrics. The access point also collects the measurements every 5 seconds, prepares 90-second reports,

and then sends the reports to the controller. The controller organizes the uplink measurements on a client

basis and the downlink measurements on an access point basis and maintains an hour’s worth of

historical data. To store this data, the controller requires 32 MB of additional memory for uplink metrics

and 4.8 MB for downlink metrics.

Table 4-2 TSPEC Request Handling Examples

CAC Mode

Reserved bandwidth for

voice calls

1

1. For bandwidth-based CAC, the voice call bandwidth usage is per access point and does not take into account co-channel access points. For load-based

CAC, the voice call bandwidth usage is measured for the entire channel.

Usage

2

2. Bandwidth-based CAC (consumed voice and video bandwidth) or load-based CAC (channel utilization [Pb]).

Normal TSPEC

Request

TSPEC with Expedited

Bandwidth Request

Bandwidth-

based CAC

75% (default setting) Less than 75% Admitted Admitted

Between 75% and 90%

(reserved bandwidth for voice

calls exhausted)

Rejected Admitted

More than 90% Rejected Rejected

Load-based

CAC

Less than 75% Admitted Admitted

Between 75% and 85%

(reserved bandwidth for voice

calls exhausted)

Rejected Admitted

More than 85% Rejected Rejected

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