308 Wi-Fi Multimedia
320657-A
3 WSS A examines the 802.1p and IP ToS information in the packet. If the interface on which the switch
will forward the packet is part of a tagged VLAN, the WSS switch maps the IP ToS value of the tunnel
header to the 802.1p priority field of the data packet. The packet is now marked as high priority at Layer
2 as well as Layer 3.
4 The packet emerges from the network cloud between the WSS switches with the same priority
information.
5 WSS B receives the packet, examines the 802.1p and IP ToS information in the packet, and encapsulates
the data packet in a tunnel packet for sending to the AP. The switch sets the IP ToS value in the tunnel
header based on the data packet’s IP ToS value, or based on the 802.1p value if IP ToS is set to 0 in the
data packet itself.
If the packet matches a permit ACL mapped to the outbound traffic direction on the AP port, Distributed
AP, or user VLAN, and the ACL sets the CoS value, the tunnel header’s IP ToS value is set based on the
CoS value in the ACL instead.
WSS B sends the encapsulated data packet to AP B.
6 AP B receives the packet and maps the IP ToS value in the tunnel header to the Voice forwarding queue
on the AP. The Voice queue has statistically more access to the air than the other queues, so the user’s
voice traffic receives priority treatment.
Table 20 shows how WMM priority information is mapped across the network. When WMM is enabled in WSS
Software, Nortel switches and APs perform these mappings automatically.
Disabling or Reenabling WMM
WMM is enabled by default on all radio profiles. To disable the feature on a radio profile, use the following command:
set radio-profile name wmm {enable | disable}
When WMM is disabled, AP forwarding prioritization is optimized for SVP instead of WMM, and the AP does not tag
packets it sends to the WSS. Otherwise, the classification and tagging described in “How WMM Works in WSS
Software” on page 305 remain in effect.
Table 20: 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
