of NetFlow records exported. NetFlow usually captures all packets received by an ingress IP interface, but some NetFlow implementations use IP filters to decide if a packet can be observed by NetFlow. Some NetFlow implementations also allow the observation of packets on the egress IP interface, but this must be used with care: all flows from any ingress interface with NetFlow enabled to any interface with NetFlow enabled could be counted twice. Sampled NetFlow Standard NetFlow was designed to process all IP packets on an interface. But in some environments, e.g. on Internet backbones, that was too costly, due to the extra processing required for each packet, and large number of simultaneous flows. So Cisco introduced sampled NetFlow on Cisco 12000, and that is now used in all high-end routers that implement NetFlow. Only one packet out of n is processed, where n, the sampling rate, is determined by the router configuration. The exact selection process depends on the implementation: One packet every n packet, in Deterministic NetFlow, as used on Cisco's 12000. One packet randomly selected in an interval of n packet, in Random Sampled NetFlow, used on modern Cisco routers. Some implementations have more complex methods to sample packets, like per-flow sampling on Cisco Martinez Catalysts. The sampling rate is often the same for all interfaces, but can be adjusted per interface for some routers. When Sampled NetFlow is used, the NetFlow records must be adjusted for the effect of sampling - traffic volumes, in particular, are now an estimate rather than the actual measured flow volume. The sampling rate is indicated in a header field of NetFlow version 5 (same sampling rate for all interfaces) or in option records of NetFlow version 9 (sampling rate per interface) Versions NetFlow and IPFIX NetFlow was initially implemented by Cisco, and described in an "informational" document that was not on the standards track: RFC 3954 – Cisco Systems NetFlow Services Export Version 9. The NetFlow protocol itself has been superseded by Internet Protocol Flow Information eXport (IPFIX). Based on the NetFlow Version 9 implementation, IPFIX is on the IETF standards track with RFC 5101 (obsoleted by RFC 7011), RFC 5102 (obsoleted by RFC 7012), etc. which were published in 2008. Equivalents Many vendors other than Cisco provide similar network flow monitoring technology. NetFlow may be a prevalent name in the area of flow monitoring, because of Cisco dominant market share