Cisco Systems 7920 IP manual Wlan QoS for VoIP

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For more details on deploying VLANs in WLAN networks, refer to the Wireless Virtual LAN Deployment Guide.

WLAN QoS for VoIP

As mentioned earlier, WLANs operate as a shared medium. This means that QoS on WLAN networks are more difficult than wired networks because end points do not have dedicated bandwidth for sending and receiving traffic. The following is a list of characteristics of a wired VoIP QoS:

∙Dedicated access per user or device (switched ethernet, Point−to−Point (P2P) WAN).

∙Packets marked with 802.1p and IP Type of Service (ToS) or Differentiated Services (DiffServ).

∙Can provide hard QoS.

∙QoS can be applied to upstream or downstream traffic.

∙Can provide hard admission control.

The following is an example of characteristics of WLAN VoIP QoS:

∙Shared access to bandwidth.

∙Packets marked with 802.1p and IP ToS or DiffServ.

∙Provides soft QoS.

∙QoS is currently available to downstream traffic from the AP, but few devices other than the Cisco 7920 provide upstream QoS toward the AP.

∙Can only provide limited admission control.

Unlike networks with dedicated bandwidth, WLAN networks have to consider traffic direction when discussing QoS. Traffic needs to be considered as either upstream or downstream from the point of view of the AP, as shown in the following example:

Cisco − Wireless IPT Design Guide for the Cisco 7920 IP Phone

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Contents Table of Contents Introduction PrerequisitesRequirements Components Used Cisco 7920 IP Phone OverviewWlan Overview RF Overview Site Surveys and Design RecommendationsRssi VoIP QoS∙ Delay Variation Jitter Not to exceed 30ms Security for the Cisco 7920 and Wlan Networks Network Sizing Number of 802.11b Devices per APNumber of 802.11b IP Phones per AP Page Numbers of 802.11b Phones per Layer 2 Subnet or Vlan Understanding Roaming Terminology Understanding Layer 2 and Layer 3 RoamingLayer 2 Roaming Page Layer 3 Roaming VLANs Wlan QoS for VoIP Page Page Page Interconnecting WLANs to Cisco Campus Infrastructure Connecting APs to the Catalyst 3550 SMI or EMI Connecting APs to the Catalyst 2950 SI Connecting APs to the Catalyst 2950 EICaveats and Limitations Call Admission Control Designing Around the Lack of Layer 3 RoamingOther Caveats and Limitations Related Information
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