The Cisco 7200 supports process switching, fast switching, and Cisco Express Forwarding (CEF), but doesn't support any form of distributed switching. The main CPU in the NPE performs all the switching tasks.
Figure 5-6 illustrates what occurs when a packet is received.
The packet is copied from the media into a series of particles linked to the interface's receive ring. The particles can reside in either I/O memory or PCI memory depending on the platform and the interface's media speed.
The interface raises a receive interrupt ...