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Configuring quality of service 353
Nortel WLAN—Security Switch 2300 Series Configuration Guide
WMM QoS on the WSS
WSS Software performs classification on ingress to determine a packet’s CoS value. This CoS value is used to mark the
packet at the egress interface.
The classification and marking performed by the switch depend on whether the ingress interface has an 802.1p or DSCP
value other than 0, and whether the egress interface is tagged or is an IP tunnel.
The mappings between DSCP and CoS values are configurable. (See “Changing CoS mappings” (page 360).) 802.1p
and CoS values map directly and are not configurable. DSCP 0 of the DSCP-to-CoS map is reserved. 802.1p determines
CoS for packets with DSCP 0. CoS 0 of the CoS-to-DSCP map is also reserved. CoS 0 packets are marked with DSCP 0.
Table 4 shows how WMM priority information is mapped across the network. When WMM is enabled, Nortel switches
and APs perform these mappings automatically.
You can use static CoS to assign the same CoS value to all packets for a specific SSID. The static CoS value is assigned
on the AP, in both traffic directions (from the client to the WSS and from the WSS to the client). (For information, see
“Configuring static CoS” (page 360).)
You also can use ACLs to override marking for specific packets. Configure ACEs that use the dscp option to match on
ingress DSCP value, and use the cos option to mark CoS. A CoS value assigned by an ACE overrides the internal CoS
value. (For information, see “Using ACLs to change CoS” (page 431).)
WMM QoS on an
AP
APs use forwarding queues to prioritize traffic for wireless clients.
For a packet received by the AP from a client, the AP classifies the packet based on the service type in the 802.11 header
and maps the service type value to an internal CoS value. The AP then marks the DSCP value in the IP tunnel header to
the WSS based on the internal CoS value.
For a packet received from a WSS and addressed to a client, the AP classifies the packet by mapping the DSCP value in
the IP tunnel header to an internal CoS value. The AP then assigns the packet to a forwarding queue based on the internal
CoS value. The AP also marks the service type in the 802.11 header based on the internal CoS value.
Table 4.WMM Priority Mappings
Service
Type
IP Precedence IP ToS DSCP 802.1p CoS
AP
Forwarding
Queue
00 0 000
Background
3 3 0x60 24 3 3
1 1 0x20 8 1 1
Best Effort
2 2 0x40 16 2 2
4 4 0x80 32 4 4
Video
5 5 0xa0 40 5 5
6 6 0xc0 48 6 6
Vo i c e
7 7 0xe0 56 7 7