 as IntServ and DiffServ now treat QoS concerns at layer 3.67 As QoS ultimately becomes an end-to-end issue, the attention to it must eventually encompass all providers in a transparent way for the users. Early generations of switching and routing equipment used simple first-in first-out (FIFO) queues for all traffic indiscriminately. When the forwarding rate exceeded the capabilities of these first routers and switches due to heavy traffic, packets would be dropped and the link reliability challenge was unloaded onto the shoulders of protocols that operated higher on the stack and that were more or less able to provide some recovery (for example, TCP). However, not all applications can afford this type of tinkering anymore. Services are now being differentiated according to their content. Therefore, packets must be inspected in real time with special bits flagging higher- to lower-pri- ority traffic. Lookup tables must be consulted to match services with forwarding policies as dictated in a service level agreement (SLA). This also requires fast and intelligent processing that goes beyond what a typical fast CPU can do. This is yet another angle from which we can look at the area of net- work processors. PERFORMANCE CONSTRAINTS IMPOSED ON COMMUNICATIONS NETWORK EQUIPMENT Figure 1.1 provides the historical overview of the last 30 years as it pertains to the evolution of com- puting and communications networks. From the top moving clockwise, the figure shows the evolving loop of applications requiring sophisticated software. This feeds a more complex hardware evolution that could justify more advanced software and SO on. The two downward-pointing arrows show the effect that the progress of semiconductor technology in conjunction with networking and software technology advances has had. It is rather striking that both arrows converge on the need for higher capability in network equipment-thus creating the need for sophisticated network processors. It must have become clear by now (at least qualitatively) why network