Figure 9: Prefix Accounting With Source And Destination Classes - Juniper JUNOS 10.1 - CONFIGURATION GUIDE 1-2010 Configuration Manual

Chapter 5: Configuring Protocol Family and Interface Address Properties
NOTE: SCU and DCU accounting are supported on the J Series router only for IPv4
and IPv6 traffic.
NOTE: We recommend that you stop the network traffic on an interface before you
modify the DCU or SCU configuration for that interface. Modifying the DCU or SCU
configuration without stopping the traffic might corrupt the DCU or SCU statistics.
Before you restart the traffic after modifying the configuration, enter the clear
command.
interfaces statistics
Figure 9 on page 221 illustrates an Internet service provider (ISP) network. In this
topology, you can use DCU to count packets customers send to specific prefixes. For
example, you can have three counters, one per customer, that count the packets
destined for prefix 210.210/16 and 220.220/16 .
You can use SCU to count packets the provider sends from specific prefixes. For
example, you can count the packets sent from prefix 210.210/16 and 215.215/16
and transmitted on a specific output interface.

Figure 9: Prefix Accounting with Source and Destination Classes

You can configure up to 126 source classes and 126 destination classes. For each
interface on which you enable destination class usage and source class usage, the
JUNOS Software maintains an interface-specific counter for each corresponding class
up to the 126 class limit.
NOTE: To configure source class and destination class usage, your router must be
equipped with the Internet Processor II ASIC.
For transit packets exiting the router through the tunnel, forwarding path features,
such as RPF, forwarding table filtering, source class usage, and destination class
usage are not supported on the interfaces you configure as the output interface for
tunnel traffic. For firewall filtering, you must allow the output tunnel packets through
the firewall filter applied to input traffic on the interface that is the next-hop interface
towards the tunnel destination.
221
Enabling Source Class and Destination Class Usage