Qos For Wireless Lans Versus Qos On Wired Lans; Impact Of Qos On A Wireless Lan - Allen-Bradley Stratix 5100 User Manual

Chapter 16 Configuring QoS
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QoS for Wireless LANs Versus QoS on Wired LANs

The QoS implementation for wireless LANs differs from QoS implementations
on other Cisco devices. With QoS enabled, access points perform the following:
• Don't classify packets; they prioritize packets based on DSCP value, client
type (such as a wireless phone), or the priority value in the 802.1q or
802.1p tag.
• Don't construct internal DSCP values; they support only mapping by
assigning IP DSCP, Precedence, or Protocol values to Layer 2 COS values.
• Carry out EDCF like queuing on the radio egress port only.
• Do FIFO queueing only on the Ethernet egress port.
• Support only 802.1Q/P tagged packets. Access points don't support ISL.
• Support only MQC policy-map set cos action.
• Prioritize the traffic from voice clients (such as Symbol phones) over traffic
from other clients when the QoS Element for Wireless Phones feature is
enabled.
• Support Spectralink phones by using the class-map IP protocol clause with
the protocol value set to 119.
To contrast the wireless LAN QoS implementation with the QoS
implementation on other Cisco network devices, see the Cisco IOS Quality of
Service Solutions Configuration Guide at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
fqos_c/index.htm

Impact of QoS on a Wireless LAN

Wireless LAN QoS features are a subset of the proposed 802.11e draft. QoS on
wireless LANs provides prioritization of traffic from the access point over the
WLAN based on traffic classification.
Just as in other media, you can not notice the effects of QoS on a lightly loaded
wireless LAN. The benefits of QoS become more obvious as the load on the
wireless LAN increases, keeping the latency, jitter, and loss for selected traffic
types within an acceptable range.
QoS on the wireless LAN focuses on downstream prioritization from the access
point. This figure shows the upstream and downstream traffic flow.
Figure 111 - Upstream and Downstream Traffic Flow
Radio
downstream
Radio
Client
upstream
device
Rockwell Automation Publication 1783-UM006A-EN-P - May 2014
Ethernet
downstream
Access
Ethernet
point
upstream
Wired
LAN