You can maintain packet counts based on the entry and exit points for traffic passing through your network. Entry and exit points are identified by source and destination prefixes grouped into disjoint sets defined as source classes and destination classes. You can define classes based on a variety of parameters, such as routing neighbors, autonomous systems, and route filters.
Source class usage (SCU) counts packets sent to customers by performing lookup on the IP source address and the IP destination address. SCU makes it possible to track traffic originating from specific prefixes on the provider core and destined for specific prefixes on the customer edge. You must enable SCU accounting on both the inbound and outbound physical interfaces.
Destination class usage (DCU) counts packets from customers by performing lookup of the IP destination address. DCU makes it possible to track traffic originating from the customer edge and destined for specific prefixes on the provider core router.
On T-series and M320 routing platforms, the source class and destination classes are not carried across the platform fabric. The implications of this are as follows:
Class-based filter match conditions are not supported on J-series Services Routers.
For more information about source class usage, see the JUNOS Policy Framework Configuration Guide, the JUNOS Network Interfaces Configuration Guide, and the JUNOS Feature Guide.