Cisco ASR 920 Series Configuration Manual page 61

Hierarchical Color-Aware Policing
xDSL connection. As shown in the figure below, a customer could send up to 1000 kb/s. However, this
involved sending more voice and voice-control packets, which required policing the traffic for both classes.
Figure 3: Policing Traffic in Child Classes
As shown in the figure below, it is important to control the overall input bandwidth. The important requirement
is that the premium traffic in the overall limit is not affected. In the figure below, voice and voice-control
packets are not dropped in the overall limit. Only packets from the child class-default class are dropped to
fulfill the limit.
Figure 4: Policing Traffic in Parent Classes
The first classes function the same way. Voice and voice-control are policed to the allowed level and the
class-default class is not affected. In the next level, the overall bandwidth is forced to 500 kb/s and must only
drop packets from the class-default class. Voice and voice-control must remain unaffected.
The order of policer execution is as follows:
1 Police the traffic in the child classes, as shown in the figure above, police VoIP-Control class to 112 kb/s,
police VoIP class to 200 kb/s, and police class-default to 500 kb/s.
2 Police the traffic in the class default of the parent policy map, but only drop the traffic from the child class
default, and do not drop the remaining child classes. As shown in the figure above, 112 kb/s VoIP-Control
and 200 kb/s VoIP traffic are unaffected at the parent policer, but 500 kb/s class default from the child is
policed to 188kb/s to meet the overall police policy of 500 kb/s at the parent level.
Policing Traffic in Child Classes and Parent Classes
QoS: Policing and Shaping Configuration Guide (Cisco ASR 920 Series)
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