3Com WX1200 3CRWX120695A, WXR100 3CRWXR10095A manual Configuring and Managing Security Acls

402CHAPTER 19: CONFIGURING AND MANAGING SECURITY ACLS

General Guidelines 3Com 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.

MSS uses IP ToS values to prioritize voice traffic. For example, when a MAP receives traffic from its WX switch, the MAP classifies the traffic based on the IP ToS value in the IP header of the tunnel that is carrying the traffic. By default, the WX switch 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 WX does not reclassify the packet, and the packet does not receive priority forwarding on the MAP.

„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 “Enabling SVP Optimization for SpectraLink Phones” on page 404 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.

Table 35 shows how WMM priority information is mapped across the network. When WMM is enabled in MSS, WX switches and MAPs perform these mappings automatically.