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Ethernet Card Software Feature and Configuration Guide, R7.2
January 2009
Chapter 14 Configuring Quality of Service
ML-Series QoS
ML-Series QoS
The ML-Series QoS classifies each packet in the network based on its input interface, bridge group
(VLAN), Ethernet CoS, IP precedence, IP DSCP, or Cisco proprietary resilient packet ring RPR-CoS.
After they are classified into class flows, further QoS functions can be applied to each packet as it
traverses the card. Figure 14-3 illustrates the ML-Series QoS flow.
Figure 14-3 ML-Series QoS Flow
Policing provided by the ML-Series card ensures that attached equipment does not submit more than a
predefined amount of bandwidth (Rate Limiting) into the network. The policing feature can be used to
enforce the committed information rate (CIR) and the peak information rate (PIR) available to a
customer at an interface. Policing also helps characterize the statistical nature of the information allowed
into the network so that traffic engineering can more effectively ensure that the amount of committed
bandwidth is available on the network, and that the peak bandwidth is over-subscribed with an
appropriate ratio. The policing action is applied per classification.
Priority marking can set the Ethernet IEEE 802.1p CoS bits or RPR-CoS bits as they exit the ML-Series
card. The marking feature operates on the outer IEEE 802.1p tag, and provides a mec hanism for tagging
packets at the ingress of a QinQ packet. The subsequent network elements can provide QoS based only
on this service-provider-created QoS indicator.
Per-class flow queuing enables fair access to excess network bandwidth, allows allocation of bandwidth
to support SLAs, and ensures that applications with high network resource requi rements are adequately
served. Buffers are allocated to queues dynamically from a shared resource pool. The allocation process
incorporates the instantaneous system load as well as the allocated bandwidth to each queue to optimize
buffer allocation. Congestion management on the ML-Series is performed through a tail drop mech anism
along with discard eligibility on the egress scheduler.
The ML-Series uses a Weighted Deficit Round Robin (WDRR) scheduling process to provide fair acc ess
to excess bandwidth as well as guaranteed throughput to each class flow.
Admission control is a process that is invoked each time that service is configured on the ML-Series card
to ensure that QoS resources are not overcommitted. In particular, admission control ensures that no
configurations are accepted, where a sum of the committed bandwidths on an interface exceeds total
bandwidth on the interface.

Classification

Classification can be based on any single packet classification criteria or a combination (logical AND
and OR). A total of 254 classes, not including the class default, can be defined o n the card. Classification
of packets is configured using the Modular CLI class-map command. For traffic transiting the Cisco
Proprietary RPR, only the input interface and/or the RPR-CoS can be used as classification criteria.
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Policing & MarkingClassification
QoS Actions at Ingress QoS Actions at Egress
Queueing & ScheduleingClassification