Nortel 2350 用户指南
Configuring and managing security ACLs 435
Nortel WLAN—Security Switch 2300 Series Configuration Guide
General guidelines
Nortel recommends that you follow these guidelines for any wireless VoIP implementation:
•
Ensure end-to-end priority forwarding by making sure none of the devices that will forward voice traffic resets IP
ToS or Diffserv values to 0. Some devices, such as some types of Layer 2 switches with basic Layer 3 awareness,
reset the IP ToS or Diffserv value of untrusted packets to 0.
ToS or Diffserv values to 0. Some devices, such as some types of Layer 2 switches with basic Layer 3 awareness,
reset the IP ToS or Diffserv value of untrusted packets to 0.
WSS Software uses IP ToS values to prioritize voice traffic. For example, when an AP receives traffic
from its WSS, the AP classifies the traffic based on the IP ToS value in the IP header of the tunnel that is
carrying the traffic. By default, the WSS marks egress traffic for priority forwarding only if WMM is
enabled and only if the ingress traffic was marked for priority forwarding. If another forwarding device in
the network resets a voice packet’s priority by changing the IP ToS or Diffserv value to 0, the WSS does
not reclassify the packet, and the packet does not receive priority forwarding on the AP.
from its WSS, the AP classifies the traffic based on the IP ToS value in the IP header of the tunnel that is
carrying the traffic. By default, the WSS marks egress traffic for priority forwarding only if WMM is
enabled and only if the ingress traffic was marked for priority forwarding. If another forwarding device in
the network resets a voice packet’s priority by changing the IP ToS or Diffserv value to 0, the WSS does
not reclassify the packet, and the packet does not receive priority forwarding on the AP.
•
For WMM-capable devices, leave WMM enabled.
•
For SVP devices, change the QoS mode to svp. You also need to disable IGMP snooping, and configure an ACL
that marks egress traffic from the voice VLAN with CoS value 7. (See
that marks egress traffic from the voice VLAN with CoS value 7. (See
for complete configuration guidelines.)
For other types of non-WMM devices, you do not need to change the QoS mode, but you must configure
an ACL to mark the traffic’s CoS value. This section shows examples for configuring VoIP for devices
that use TeleSym, and for Avaya devices.
an ACL to mark the traffic’s CoS value. This section shows examples for configuring VoIP for devices
that use TeleSym, and for Avaya devices.
shows how WMM priority information is mapped across the network. When WMM is enabled in WSS
Software, WSSs and APs perform these mappings automatically.
You must map the ACL to the outbound traffic direction on an AP port, Distributed AP, or user VLAN. An ACL can set
a packet’s CoS only in these cases.
a packet’s CoS only in these cases.
You can enable legacy VoIP support on a VLAN, port group, port list, virtual port list, Distributed AP, or user wildcard.
You do not need to disable WMM support.
You do not need to disable WMM support.
Table 5: WMM priority mappings
Service
Type
Type
IP Precedence IP ToS
DSCP
802.1p
CoS
AP
Forwarding
Queue
Forwarding
Queue
0
0
0
0
0
0
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
Voice
7
7
0xe0
56
7
7