As network administrators learn to manage and scale larger and larger networks, they must also be able to account for the usage of a growing customer base. How can you ensure that customers are being charged correctly for their network utilization? How can you ensure that they are receiving the services for which they have contracted? BGP policy accounting addresses these concerns.
BGP policy accounting using AS numbers can be used to improve the design of network circuit peering and transit agreements between ISPs.
BGP policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an input interface, and counters based on parameters such as community-list, AS number, or AS path are assigned to identify the IP traffic. Using BGP policy accounting, you can account for traffic according to the route that it traverses. Service providers can identify and account for all traffic by customer and can bill accordingly. In the figure, BGP policy accounting can be implemented in Router A to measure packet and byte volumes in AS buckets. Customers are billed appropriately for traffic that is routed from a domestic, international, or satellite source.
Using the BGP table-map command, prefixes added to the routing table are classified by BGP attribute, AS number, or AS path. Packet and byte counters are incremented per input interface. A Cisco IOS policy-based classifier maps the traffic into one of eight possible buckets, representing different traffic classes.
Implementing BGP policy accounting on an edge router can highlight potential design improvements for peering and transit agreements.
Scaling Service Provider Networks
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