Summary 227 programmable logic rather than a custom design is that FPGAs are broadly avail- able and do not require fabrication of a custom chip. Also, an FPGA integrated into a network system design could be used for different accelerators and thus allows a level of customization not possible with custom logic accelerators. Many existing network processing systems use custom logic for their accelera- tors since they provide better performance than FPGA-based implementations. The need for flexibility may change this balance toward more programmable logic implementations in future networks (see Chapter 15). SUMMARY This chapter explored some of the specialized hardware components used for packet processing in router systems. Network processors use multiple parallel pro- cessor cores to implement packet forwarding and more advanced functions. These network processors provide a general-purpose platform, where the router operation can be changed by updating software. In contrast, hardware accelerators provide a fixed set of functions specialized for the networking domain. Hardware accelera-