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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 24 Configuring QoS
Configuring Quality of Service (QoS)
• You can add only a maximum of 128 ACL match filters (including default deny ace) as part of class
or classes.
Improving Feature Scalability
Effective with Cisco IOS Release 15.3(2)S, Ternary Content Addressable Memory (TCAM) is allocated
and deallocated dynamically based on system configuration. This improves both feature scalability and
efficiency of usage of TCAM. 25 percent of this memory is reserved for Layer 2 and Layer 3 control
protocols and the remaining 75 percent is allocated dynamically based on the requirements. Layer 2 and
Layer 3 forwarding tables are independent of TCAM.
TCAM with QoS
The scalability of QoS will change depending on the features configured on the Cisco ASR 901 Router.
The following are the examples:
• You can create a maximum of 768 TCAM rules.
• You can create a maximum of 640 TCAM rules with remote loopback in Ethernet OAM (802.3ah),
Ethernet loopback, and DelayMeasurement configured.
• You can create a maximum of 512 TCAM rules with remote loopback in Ethernet OAM (802.3ah),
Ethernet loopback, DelayMeasurement, and Router ACL configured.
For more information on troubleshooting scalability, see Troubleshooting Tips, page 24-81.
QoS for MPLS/IP over MLPPP
Effective with Cisco IOS Release 15.4(1)S, the extended QoS functionality is supported on the MLPPP
interface. The egress policy supports classification on the MLPS EXP bits.
The following actions are supported:
• Bandwidth percent
• Priority percent
• Setting the MPLS EXP bits
• Setting the queue limit.
QoS for CPU Generated Traffic
Effective with Cisco IOS Release 15.4(1)S, QoS is provided for CPU generated traffic. The classification
is based on DSCP (for packets going over IP adjacency) or EXP (for packets going over TAG
Adjacency).
QoS treatment is available for the following CPU generated traffic:
• OSPF Packets
• ICMP Packets
• BGP Packets
• LDP Packets
• ISIS Frames