Cisco Performance Routing (PfR) enhances traditional routing methods by dynamically selecting the best path for applications based on network performance. The path selection procedure can be influenced by several factors, including delay, packet loss, reachability, throughput, jitter, and mean opinion score (MOS).

PfR passive monitoring mode relies on NetFlow to capture performance metrics. Metrics used by passive mode include delay, packet loss, reachability, and throughput. Throughput can be measured for all traffic flows. Delay, packet loss, and reachability can be measured only for Transmission Control Protocol (TCP) flows.

PfR active monitoring mode relies on IP Service Level Agreement (SLA) probes that generate traffic to capture performance metrics. Metrics used by active mode include delay, jitter, MOS, and reachability. Short term monitoring uses the last five probe results; long term monitoring uses the last 60 probe results.

A third PfR monitoring mode, fast mode, is similar to active mode. Active mode generates probes only for the active exit path. By contrast, fast mode continuously generates probes for all possible exit paths, not just the active exit path. Fast mode allows route changes to be made within three seconds. However, the performance benefits of fast mode require significant processor overhead? therefore, Cisco recommends that you use fast mode only for performance sensitive traffic, such as Voice over IP (VoIP) or video traffic.