Cisco Systems OL-6415-04 manual Precedence of QoS Settings, Upstream and Downstream Traffic Flow

Chapter 9 Configuring QoS

Understanding QoS for Wireless LANs

QoS on the wireless LAN focuses on downstream prioritization from the access point. Figure 9-1shows the upstream and downstream traffic flow.

Figure 9-1 Upstream and Downstream Traffic Flow

•The radio downstream flow is traffic transmitted out the access point radio to a wireless client device. This traffic is the main focus for QoS on a wireless LAN.

•The radio upstream flow is traffic transmitted out the wireless client device to the access point. QoS for wireless LANs does not affect this traffic.

•The Ethernet downstream flow is traffic sent from a switch or a router to the Ethernet port on the access point. If QoS is enabled on the switch or router, the switch or router might prioritize and rate-limit traffic to the access point.

•The Ethernet upstream flow is traffic sent from the access point Ethernet port to a switch or router on the wired LAN. The access point does not prioritize traffic that it sends to the wired LAN based on traffic classification.

Precedence of QoS Settings

When you enable QoS, the access point queues packets based on the Layer 2 class of service value for each packet. The access point applies QoS policies in this order:

1.Packets already classified—When the access point receives packets from a QoS-enabled switch or router that has already classified the packets with non-zero 802.1Q/P user_priority values, the access point uses that classification and does not apply other QoS policy rules to the packets. An existing classification takes precedence over all other policies on the access point.

Note Even if you have not configured a QoS policy, the access point always honors tagged 802.1P packets that it receives over the radio interface.

2.QoS Element for Wireless Phones setting—If you enable the QoS Element for Wireless Phones setting, dynamic voice classifiers are created for some of the wireless phone vendor clients, which allows the wireless phone traffic to be a higher priority than other clients’ traffic. Additionally, the QoS Basic Service Set (QBSS) is enabled to advertise channel load information in the beacon and probe response frames. Some IP phones use QBSS elements to determine which access point to associate to, based on the traffic load.

You can use the Cisco IOS command dot11 phone dot11e command to enable the future upgrade of the 7920 Wireless Phone firmware to support the standard QBSS Load IE. The new 7920 Wireless Phone firmware will be announced at a later date.

Cisco Wireless ISR and HWIC Access Point Configuration Guide

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