sary functionality in steady state and nonsteady state processing. By executing NPU picocode, the NPU itself performs all steady state operations. These operations include filtering, frame forwarding, frame alterations, protocol layer 2, 3, and 4 pro- cessing, classification, QoS, traffic management, and accounting. At the same time, the so-called con- trol point (CP) processor performs nonsteady state functions. These include route discovery, updates to the tree, updates to the Open Shortest Path First (OSPF) database, Simple Network Management Protocol (SNMP) agent processing, debug/diagnostics, configuration management, and deep frame processing, as well as executing applications that the network equipment vendor (NEV) develops. The CP is an external processor that supervises and serves a system comprised of several NPUs. The NP4GS3 is designed to accommodate many vendor designs with various CP-NP configurations. Refer to Figure 4.1 for an example of two NPUs and one CP. Either of the internal PowerPC CPUs or an external one can be used as the configuration CP. When traffic requires nonsteady state operations in such an arrangement, the NPU communicates with the CP by special frames of a special EtherType. IBM calls these frames guided frames, and they can contain data and one or more commands. The CP uses them to update forwarding tables in the NPUs (that is, trees). This two-NPU configuration can support 80 Fast Ethernet (10/100 Mbps) ports or 8 Gigabit Ethernet ports. It can also support eight OC-3/OC-12 Packet over SONET (POS) ports or even two OC-48 POS ports. In contrast, a single-NPU configuration where no switch fabric is required can sup- port half as many of the same ports in an NP-CP scheme. Up to 16 NPUs can be controlled by 1 CP. When the design requires more than two NP4GS3 network processors, as shown in Figure 4.2, switch fabric is required for the data movement. In the configuration shown in Figure 4.2, the NPUs split the set of chores of layer 2 forwarding and filtering (frame repository and 