The generally accepted definition of an active network is one that modifies its behavior based on the packets crossing the devices. Active networks generally contain parts such as Network Processor Units (NPUs) or Field Programmable Gate Arrays (FPGAs) rather than Application-Specific Integrated Circuit (ASIC).

While newer ASICs have some programmable capacity, they are still less malleable than FPGAs.

An NPU is a computer processor optimized for handling network data. As we discussed earlier, all of the initial routing devices on the internet did software forwarding, using a general-purpose Computer Processing Unit (CPU) which limited the throughput and speed of these devices. The NPU, similar to the CPU, will have a programmable path, or pipeline that can be modified in real-time to process network data. Network-specific ASICs, NPUs, and FPGAs brought forwarding to the hardware level.

An FPGA, as the name says, is a re-programmable application specific...