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CHAPTER 7
Configuring QoS on an Access Point
This chapter describes how to configure quality of service (QoS) on an access point. QoS provides
preferential treatment to certain traffic at the expense of other traffic. Without QoS, the access point
offers best-effort service to each packet, regardless of the packet contents or size. It sends the packets
without any assurance of reliability, delay bounds, or throughput.
Recommended Reading
The following information is recommended for gaining a bet
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Chapter 7 Configuring QoS on an Access Point Understanding QoS for Wireless LANs • Does not construct internal DSCP values; it only supports mapping by assigning IP DSCP, precedence, or protocol values to Layer 2 CoS values. Table 7-1 lists the class of service (CoS) values as they map to DSCP values. Table 7-1 CoS Values Mapped to DSCP Values CoS Value DSCP Value 110 218 326 434 546 648 756 • Carries out Enhanced DCF (EDCF)-like queuing on the radio egress port only. • Support only 802.1
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Chapter 7 Configuring QoS on an Access Point Configuration Guidelines Figure 7-1 Upstream and Downstream Traffic Flow Radio Ethernet downstream downstream Wired LAN Access Radio Ethernet Client point upstream upstream device Precedence of QoS Settings When you enable QoS, the access point queues packets based on the CoS value for each packet. If a packet matches one of the filter types based on its current precedence, the packet is classified based on the matching filter and no other filte
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Chapter 7 Configuring QoS on an Access Point Configuration Guidelines In addition, a Cisco access point uses Access Control Lists for forwarding or blocking packets on selective basis, as designated by the user for the purpose of: • Providing QoS for Voice-over-IP (VoIP) phones. • Mapping IP precedence values into 802.1P/Q Class of Service (CoS) values for downlink traffic. • Providing Layer 2 and Layer 3 Access Control List features to the bridging path and access point host receive pat
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Chapter 7 Configuring QoS on an Access Point Configuration Guidelines Cisco Wireless IP Phone 7920 Support The Wireless IP Phone 7920 phone uses Cisco CDP message with Appliance VLAN-ID TLV to inform the access point of its presence. The access point intercepts the CDP messages sent from the client, and if it contains the Appliance VLAN-ID TLV, it should flag the client as VoIP phone client. If VLAN is enabled, all phone clients should be associated to a single Voice VLAN. If VLAN is not
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Chapter 7 Configuring QoS on an Access Point Configuration Guidelines Ethernet Interface Transmit Queue Since the Ethernet interface always has a larger bandwidth than radio interface, there is no need to maintain priority queues for Ethernet interface. There will be only one transmit queue per Ethernet interface. 802.1Q Untagged Voice Packets If VLAN is enabled, IOS bridging code adds 802.11q tags into the untagged voice packets. The class of service (CoS) value should be part of the VLA
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Chapter 7 Configuring QoS on an Access Point Configuration Guidelines Table 7-4 Access Control List Numbers 700 - 799 MAC address access list Allow or deny packet forwarding based on Ethernet packet MAC source or destination addresses 200 - 299 Protocol type-code access list Allow or deny packet forwarding based on packet protocol type-code, in the case of Ethernet, it is either DIX, SAP, or SNAP type The radio interface supports the following access lists: • <1 - 99> IP standard access l
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Chapter 7 Configuring QoS on an Access Point End User Interface End User Interface The 802.1Q user_priority maps to radio transmit priority queues automatically. VLAN default user_priority value must be explicitly assigned through the command line interface (CLI), or the default value zero is used for the VLAN. For voice traffic, whenever a 802.11 VOIP phone is associated with an access point, a default traffic egress filter with user_priority value 6 is installed for all the voice traffi
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Chapter 7 Configuring QoS on an Access Point End User Interface Apply Layer 2 Acess Control List To Packet Received/Sent Use the l2-filter bridge-group-acl configuration interface command to apply a Layer 2 access control list (ACL) filter to the bridge group incoming and outgoing packets between the access point and the host (upper layer). Use the no form of the command to disable the Layer 2 ACL filter. [no] l2-filter bridge-group-acl If enabled, and if any L2 ACLs are installed in ingr
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Chapter 7 Configuring QoS on an Access Point End User Interface Cisco Wireless Router and HWIC Configuration Guide 7-10 OL-6415-03
