ass-Based Hosts generate RSVP signaling when it is necessary to Queuing. Many vendors use different names for these obtain high quality guarantees. The network listens to schemes and often combine the schemes together. this signaling at strategic points in the network. We will refer to devices that participate in RSVP signaling as Priority queuing RSVP agents or alternatively as signaling or admission control agents. As we have shown, appointing such agents In Priority Queuing, packets are forwarded on a strict at varying densities can provide varying quality/efficiency priority basis. This means that packets in the products. At a minimum we assume one or more ad- higher-priority queue are sent first before any packets in mission control agents in each subnet. Each agent uses the lower-priority queue (see Figure 3.3-1). the mappings defined in ISSLL to translate high-level This works well for giving highly predictable perfor- end-to-end RSVP requests into parameters that are mance for the high-priority packets, but lower-priority meaningful to the media for which the agent is re- packets can be greatly delayed if there is significant sponsible. The admission control agent then determines, high-priority traffic. Priority queuing works best in situ- based on resource availability and/or policy decisions ations where the high-priority traffic has a relatively fixed (with the cooperation of PDPs), whether an RSVP re- bandwidth requirement (like voice). That allows priority quest is admissible or not. Any admission control agent queuing to be use while still giving predictable perfor- along the route from sender to receiver may veto an mance to the lower-priority traffic. RSVP request for resources. Requests that are not vetoed by any device are considered admitted and result in the return of an RSVP RESV message to the requesting Weighted fair queuing transmitting host. Weighted Fair Queuing (WFQ) is a method to overcome problems in strict Priority Queuing by giving all of the Prioritized queuing packets a weighting 