[1] For example dedicated packet routing hardware used to build computer networks will often take care of the most common kinds of packets in hardware, with other kinds passed to the "slow path", usually implemented by software running on the control processor.
Even in pure software, specific implementations have been developed that leverage the concept of a fast path to maximize the performance of packet processing.
In these implementations, the networking stack is split into two layers and the lower layer processes the majority of incoming packets outside the operating system (OS) environment without incurring any of the OS overheads that degrade overall performance.
Only those rare packets that require complex processing are forwarded to the OS networking stack, which performs the necessary management, signaling and control functions.
One common way to perform a denial-of-service attack is to flood a device with packets which require use of the slow path.