Accounting for MPLS-Based Networks

NetFlow capitalizes on the flow nature of traffic in the network to provide detailed IP accounting information with minimal impact on router/switch performance. NetFlow monitors IP flows in the router/switch and exports the flows in UDP format to a NetFlow collector. The NetFlow collector can correlate, aggregate, and report on the data received from the network. NetFlow data can be used for a variety of purposes, including network management and planning, enterprise accounting, departmental chargeback, usage-based billing, data warehousing/mining for marketing purposes, and so on. The latest version of NetFlow, version 9, extends it to support MPLS label information, IPv6 details, BGP next-hop data, and multicast information.

MPLS-aware NetFlow can be used to determine and account for traffic to a particular destination in the MPLS cloud. It also supports the complete IP flow information export plus the export of up to three labels and label destination prefix information including the MPLS EXP value. In addition, MPLS-aware NetFlow can also account for MPLS traffic that contains IP or non-IP packets and has the capability to include the MPLS header as part of the accounting information. MPLS-aware NetFlow is an extension of NetFlow accounting that provides highly granular traffic statistics for Cisco routers. It collects statistics on a per-flow basis using the NetFlow Version 9 export format. MPLS-aware NetFlow exports up to three labels of interest from the incoming label stack, the IP address associated with the top label, as well as traditional NetFlow data. A network administrator can turn on MPLS-aware NetFlow inside an MPLS cloud on a subset of provider backbone (P) routers. These routers can export MPLS-aware NetFlow data to an external NetFlow collector device for further processing and analysis or show NetFlow cache data on a router terminal. All statistics can be used for detailed MPLS traffic studies and analysis.

The MPLS egress NetFlow accounting feature captures IP flow information for packets undergoing MPLS label dispositionthat is, packets that arrive on a router as MPLS and that are transmitted as IP. One common application of the MPLS egress NetFlow accounting is to capture the MPLS VPN IP flows that are traveling from one site of a VPN to another site of the same VPN through the service provider backbone.