Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter Guide De Conception
5-24
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 5 Cisco Unified Wireless QoS
Guidelines for Deploying Wireless QoS
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The wired LWAPP AP interface does read or write Layer 2 CoS (802.1P) information, the WLC and
the APs depend on Layer 3 classification (DSCP) information to communicate WLAN client traffic
classification. This DSCP value may be subject to modification by intermediate routers, and
therefore the Layer 2 classification received by the destination might not reflect the Layer 2
classification marked by the source of the LWAPP traffic.
the APs depend on Layer 3 classification (DSCP) information to communicate WLAN client traffic
classification. This DSCP value may be subject to modification by intermediate routers, and
therefore the Layer 2 classification received by the destination might not reflect the Layer 2
classification marked by the source of the LWAPP traffic.
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The APs no longer use NULL VLAN ID. As a consequence, L2 LWAPP does not effectively support
QoS because the AP does not send the 802.1P/Q tags, and in L2 LWAPP there is no outer DSCP on
which to fall back.
QoS because the AP does not send the 802.1P/Q tags, and in L2 LWAPP there is no outer DSCP on
which to fall back.
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APs do not re-classify frames; they prioritize based on CoS value or WLAN profile.
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APs carry out EDCF-like queuing on the radio egress port only.
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APs do FIFO queueing only on the Ethernet egress port.
WAN QoS and the H-REAP
For WLANs that have data traffic forwarded to the WLC, the behavior is same as non-hybrid remote
edge access point (H-REAP) APs. For locally-switched WLANs with WMM traffic, the AP marks the
dot1p value in the dot1q VLAN tag for upstream traffic. This occurs only on tagged VLANs; that is, not
native VLANs.
edge access point (H-REAP) APs. For locally-switched WLANs with WMM traffic, the AP marks the
dot1p value in the dot1q VLAN tag for upstream traffic. This occurs only on tagged VLANs; that is, not
native VLANs.
For downstream traffic, the H-REAP uses the incoming dot1q tag from the Ethernet side and uses this
to queue and mark the WMM values on the radio of the locally-switched VLAN.
to queue and mark the WMM values on the radio of the locally-switched VLAN.
The WLAN QoS profile is applied both for upstream and downstream packets. For downstream, if an
802.1P value that is higher than the default WLAN value is received, the default WLAN value is used.
For upstream, if the client sends an WMM value that is higher than the default WLAN value, the default
WLAN value is used. For non-WMM traffic, there is no CoS marking on the client frames from the AP.
802.1P value that is higher than the default WLAN value is received, the default WLAN value is used.
For upstream, if the client sends an WMM value that is higher than the default WLAN value, the default
WLAN value is used. For non-WMM traffic, there is no CoS marking on the client frames from the AP.
Note
Bug CSCsi78368 currently impacts the CoS Marking of traffic from the WLC and the CoS marked on
frames sent by the WLC represents the value set by the QoS profile and not the WMM CoS marked by
the client.
frames sent by the WLC represents the value set by the QoS profile and not the WMM CoS marked by
the client.
Guidelines for Deploying Wireless QoS
The same rules for deploying QoS in a wired network apply to deploying QoS in a wireless network. The
first and most important guideline in QoS deployment is to know your traffic. Know your protocols, the
sensitivity to delay of your application, and traffic bandwidth. QoS does not create additional bandwidth;
it simply gives more control over where the bandwidth is allocated.
first and most important guideline in QoS deployment is to know your traffic. Know your protocols, the
sensitivity to delay of your application, and traffic bandwidth. QoS does not create additional bandwidth;
it simply gives more control over where the bandwidth is allocated.
Throughput
An important consideration when deploying 802.11 QoS is to understand the offered traffic, not only in
terms of bit rate, but also in terms of frame size, because 802.11 throughput is sensitive to the frame size
of the offered traffic.
terms of bit rate, but also in terms of frame size, because 802.11 throughput is sensitive to the frame size
of the offered traffic.
shows the impact that frame size has on throughput: as packet size decreases, so does
throughput. For example, if an application offering traffic at a rate of 3 Mbps is deployed on an 11 Mbps
802.11b network, but uses an average frame size of 300 bytes, no QoS setting on the AP allows the
802.11b network, but uses an average frame size of 300 bytes, no QoS setting on the AP allows the