Enabling Prioritization For Legacy Voice Over Ip; General Guidelines - D-Link DWS-1008 - AirPremier MobileLAN Switch Product Manual

Enabling Prioritization for Legacy Voice
MSS supports Wi-Fi Multimedia (WMM). WMM support is enabled by default and is automatically used
for priority traffic between WMM-capable devices.
MSS also can provide prioritization for non-WMM VoIP devices. However, to provide priority service to
non-WMM VoIP traffic, you must configure static CoS or configure an ACL to set the CoS for the traffic.
The AP maps the CoS value assigned by static CoS or the ACL to a forwarding queue. The examples in
this section show how to configure CoS using ACLs. To use static CoS instead, see "Configuring Static
CoS".
D-Link 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 an AP receives traffic
from its switch, 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 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 switch 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 "Enabling SVP Optimization for SpectraLink Phones" 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.
The table on the next page shows how WMM priority information is mapped across the network. When
WMM is enabled in MSS, DWS-1008 switches and APs perform these mappings automatically.
D-Link DWS-1008 User Manual
over IP

General Guidelines