Inside Cisco IOS Software Architecture (CCIE Professional Development)

Packet Switching with the Cbus

Recall the descriptions of fast switching and process switching from Chapter 2, “Packet Switching Architecture.” In both of these methods, the receiving interface hardware copies the received packet into I/O memory and interrupts the main processor to begin switching the packet. Whether during the interrupt or in a background process, the main processor has to do all the work of actually switching the packet; the interface hardware just receives the packet and transmits it to the media. Also, packet switching is just one of the many tasks the main processor has to do, so not all of its capacity is available for packet switching.

The Cbus and the Cbus Controller provided another processing alternative on the AGS+. ...