/mcpQuality of Service for Voice over IP VoIP QoS over Frame Relay Networks 36 QoSVoIP.mif VoIP QoS over Frame Relay Networks This section describes how to configure VoIP in a typical network where Frame Relay WAN links are used to carry voice traffic. It includes the following subsections: • VoIP QoS over Frame Relay Scenario • VoIP QoS over Frame Relay Recommended Solution VoIP QoS over Frame Relay Scenario Another typical VoIP application is for a large corporation to use its existing Frame Relay WAN data traffic infrastructure to carry voice calls between its headquarters and its branch offices. There are two options here: either carry the voice and data on separate PVCs or use the same PVC for voice and data traffic. In the first scenario, you must still give the voice traffic priority by using a technique such as PVC Interface Priority Queue (PIPQ). PIPQ lets you assign different priorities for PVCs—high, medium, normal, or low. PIPQ also allows PVCs to be queued at the main physical interface so that high priority traffic goes before medium, normal, and low priority traffic. PIPQ, however, has the same problem as priority queueing—the high priority traffic can starve the other traffic of bandwidth. However, if you use Frame Relay traffic shaping correctly, you can minimize this problem because each PVC will have a defined maximum transmission rate. In the most common scenario, you use a single PVC to carry all the traffic between sites, as shown in Figure 10.