Wred Support For Ipv4 Multicast Egress Qos Traffic - Cisco ASR 9000 Series Configuration Manual

Information About Configuring Modular QoS Congestion Avoidance on Cisco ASR 9000 Series Routers
If the value of x gets too high, WRED does not react to congestion. Packets are sent or dropped as if
Note
WRED were not in effect.
For low values of x, the average queue size closely tracks the current queue size. The resulting average
may fluctuate with changes in the traffic levels. In this case, the WRED process responds quickly to long
queues. Once the queue falls below the minimum threshold, the process stops dropping packets.
If the value of x gets too low, WRED overreacts to temporary traffic bursts and drops traffic
unnecessarily.

WRED Support for IPv4 Multicast Egress QoS Traffic

Weighted random early detection (WRED) is supported for IPv4 multicast egress QoS traffic. The
following features are supported:
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Policy map configurations that use Random Early Detection (RED) must comply with the following
requirements. These requirements must be met across all interfaces in the line card for precedence and
DSCP-based WRED to be supported for multicast traffic. The policy map configuration requirements
are specific to a line card and not across the line cards:
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If the policy map requirements are not met for all interfaces in the line card and are not met for at least
one policy map, RED configuration is not applied to the multicast traffic and all multicast traffic in the
line card is tail-dropped. See the
Interfaces with no policy maps and interfaces with policy maps that do not use RED function normally.
For hierarchal policy maps that use WRED, only the child policies should conform to the policy map
configuration requirements.
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
QC-66
D r a f t — C i s c o C o n f i d e n t i a l
Classification based on precedence and differentiated services code point (DSCP)
Queue selection
Maximum and minimum guaranteed bandwidth
Detection of remaining bandwidth
Priority queuing
Queue limit
Random early detection (RED)
Traffic shaping
Layer 2 set on ATM and Ethernet
Multicast must be enabled.
The same class maps must be used in all the policy maps.
The class maps must be configured in the same order in all of the policy maps.
The same RED statements must be configured in a class map across policy maps. The minimum and
maximum threshold values can be different for each policy map.
If a RED profile is used by more than one DSCP or precedence in a class, the precedence or DSCP
values share the same RED profile in all the different policy maps.
Configuring Modular QoS Congestion Avoidance on Cisco ASR 9000 Series Routers
"Tail Drop and the FIFO Queue" section on page 67.
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