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Troubleshooting Quality of Service
Limitations, errors and warnings
TCAM limitation
The Ternary CAM (TCAM) is a specialized piece of memory designed for rapid table lookups
performed by the ACL engine on Ethernet Modules. Module QoS users ACL based TCAM
lookups for packet classification. ACLs are processed in hardware that is called TCAM. When
you configure policy-map, configure matching rules for the class-maps within the policy-map
and when you apply the QoS policy-map on the interface, the router programs the TCAM. If
you have already utilized all of the available TCAM space on the Router for the QoS, you
encounter this error message: PSL ERROR: TCAM usage reached the maximum limit
Currently there is no show command to display the TCAM usage.
Please note that TCAM is a shared resource used by Module QoS, ACL based firewall rules
and for IPv6 Multicast.
Policer limitation
Module QoS Policing is done in the hardware. The number of policers that can be created is
limited (300). If you have already utilized all policer entries on the Router, you encounter this
error message: ERROR: Configured policers already reached the maximum limit: xxx
Please note that a policer entry is created in the hardware whenever accounting/policing is
configured/enabled for a class-map.
Service Policy limitation
A policy-map with policer configuration (accounting/policing) cannot be mapped across line
cards. If any policy-map is attempted to be mapped to interfaces across line cards, you
encounter this error message: ERROR: Policy map (with policing/accounting enabled) is
mapped across devices
CoS marking of output queue 1 (highest priority queue)
Module QoS supports eight queues on each port. The priorities assigned for these queues are
fixed. Queue 1 is of highest priority and queue 8 is the lowest priority queue. In general, the
control traffic generated by the CPU will go through the highest priority queue. So, if you attempt
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Troubleshooting
Comments? infodev@avaya.com
August 2013
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Table of Contents
Troubleshooting
