Netflow provides a means to do accounting in IP networks, which can be used for network management, planning, and billing. The data gathered is a set of traffic statistics, such as protocol, port, and QoS information. You can export the information that you gather on network flows to a Netflow collector to analyze and further process. A flow is unidirectional and is defined as the set of source IP address, destination IP address, source port, destination port, protocol, TOS byte, and input interface. Netflow provides accounting in IP networks, but it can also provide accounting in MPLS networks. Look at Figure 14-11 for an overview of where Netflow can operate in MPLS networks.