Inside Cisco IOS Software Architecture

Appendix A. NetFlow Switching

Although many people think of NetFlow as a switching path, it isn’t; instead, it enables several key applications that customers can use for billing, traffic monitoring, and traffic profiling. Although NetFlow provides traffic accounting and feature acceleration services, packet switching is still performed by process switching, fast switching, optimum switching, or CEF. Therefore, NetFlow can be applied with other switching methods.

A flow is defined as a unidirectional sequence of packets between given source and destination endpoints. A flow in the context of NetFlow is defined as the combination of the following fields:

• Source IP address

• Destination IP address

• Source TCP/UDP application port number

• Destination ...