NetFlow is a key element of the original version of the Cisco Cyber Threat Defense solution, and continues to play a vital role in this second-generation update. NetFlow is a Cisco application that measures IP network traffic attributes of a traffic flow. A flow is identified as a unidirectional stream of packets between a given source and destination as it traverses the Cisco device. NetFlow was initially created to measure network traffic characteristics such as bandwidth, application performance, and utilization. Reference: https://www.cisco.com/c/dam/en/us/td/docs/security/network_security/ctd/ctd2- 0/design_guides/ctd_2-0_cvd_guide_jul15.pdf