tory objectives of throughput maximization, the isolation of flows, rate guarantees, and the allocation of excess net- working resources with some commonly acceptable notion of fairness. The use of a first-in first-out (FIFO) approach to manage buffers with some sense of fair discard- ing of packets and of fair allocation of the excessive free headroom ends up being favorably compared to a major per-flow scheduling method such as WFQ. Ideally, multiple buffer pools enable a better traffic flow isolation. In terms of admissibility based on two criteria-namely, buffer availability transmission bandwidth availability-buffer management with FIFO matches WFQ in bandwidth availability and outperforms WFQ in bandwidth availability. The technique is therefore more than worthy of attention. Some interesting work has also been done where the two methods are combined and concatenated. In other words, FIFO buffer management was followed by WFQ scheduling. Some systems also take this idea of differentiated packet treatment and expand it to the entire QoS toolkit, providing a more sophisticated approach to the problem. TRAFFIC MANAGER CASE STUDIES Multiple traffic manager chips have been discussed in the previous chapters at points where we pre- sented the overall network-processing platform of each of the most prominent vendors in the indus- try. Refer to the appropriate chapters for specific case studies. SUMMARY In this chapter, we discussed the fundamental workings of typical standalone traffic managers. We reviewed fundamental concepts in QoS provisioning. We also discussed typical architectures of inter- facing traffic managers with network processors and switch fabrics and, of course, algorithms used to implement traffic policing, shaping, queuing, scheduling, buffer management, and congestion avoid- ance. We also reviewed the major protocols involved in providing state-of-the-art QoS services in the evolving high-speed networks. Case studies of traffic manager chips are provided in previous chap- ters where specific ve