Cisco ASR 9000 Series Service Configuration Guide

Configuring Modular QoS Congestion Management on Cisco ASR 9000 Series Routers
Information About Configuring QoS Congestion Management on Cisco ASR 9000 Series Routers
QC-50
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
OL-23108-02
The time interval between token updates (Tc) to the token bucket is updated at the CIR value each time
a packet arrives at the traffic policer. The Tc token bucket can contain up to the Bc value. If a packet of
size B is greater than the Tc token bucket, then the packet exceeds the CIR value and a configured action
is performed. If a packet of size B is less than the Tc token bucket, then the packet conforms and a
different configured action is performed.
Traffic Shaping Versus Traffic Policing
Although traffic shaping and traffic policing can be implemented together on the same network, there
are distinct differences between them, as shown in
Table 1.
Congestion Management Using DEI
You can manage congestion based on the Drop Eligible Indicator (DEI) bit that is present in 802.1ad
frames and 802.1ah frames. Random early detection based on the DEI value is supported on 802.1ad
packets for:
• Layer 2 subinterfaces
• Layer 2 main interfaces
• Layer 3 main interfaces
• Ingress and egress
Note If there are any marking actions in the policy, the marked values are used for doing WRED.
Ta b l e 1 Differences Between Traffic Shaping and Traffic Policing
Traffic Shaping Traffic Policing
Triggering Event • Occurs automatically at regular intervals (Tc).
or
Occurs whenever a packet arrives at an interface.
• Occurs whenever a packet arrives at an
interface.
What it Does • Classifies packets.
• If a packet does not meet match criteria, no
further action is taken.
• Packets meeting match criteria are sent (if there
are enough tokens in the token bucket)
or
Packets are placed in a queue for transmission
later.
• If the number of packets in the queue exceed the
queue limit, the packets are dropped.
• Classifies packets.
• If a packet does not meet match criteria, no
further action is taken.
• Packets meeting match criteria and
conforming to or exceeding a specified
rate, receive the configured policing action
(for example, drop, send, mark, then send).
• Packets are not placed in a queue for
transmission later.

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English