Users Guide

as many entries as possible, and then generates an CAM-full error message (shown in the following example). The partial policy-map
conguration might cause unintentional system behavior.
%EX2YD:12 %DIFFSERV-2-DSA_QOS_CAM_INSTALL_FAILED: Not enough space in L3
Cam(PolicyQos) for class 2 (TeGi 12/20) entries on portpipe 1
The test cam-usage command allows you to verify that there are enough available CAM entries before applying a policy-map to an
interface so that you avoid exceeding the QoS CAM space and partial congurations. This command measures the size of the specied
policy-map and compares it to the available CAM space in a partition for a specied port-pipe.
Test the policy-map size against the CAM space for a specic port-pipe or all port-pipes using these commands:
• test cam-usage service-policy input policy-map {stack-unit } number port-set number
• test cam-usage service-policy input policy-map {stack-unit } all
The output of this command, shown in the following example, displays:
• The estimated number of CAM entries the policy-map will consume.
• Whether or not the policy-map can be applied.
• The number of interfaces in a port-pipe to which the policy-map can be applied.
Specically:
• Available CAM — the available number of CAM entries in the specied CAM partition for the specied line card or stack-unit port-
pipe.
• Estimated CAM — the estimated number of CAM entries that the policy will consume when it is applied to an interface.
• Status — indicates whether the specied policy-map can be completely applied to an interface in the port-pipe.
• Allowed — indicates that the policy-map can be applied because the estimated number of CAM entries is less or equal to the
available number of CAM entries. The number of interfaces in the port-pipe to which the policy-map can be applied is given in
parentheses.
• Exception — indicates that the number of CAM entries required to write the policy-map to the CAM is greater than the number of
available CAM entries, and therefore the policy-map cannot be applied to an interface in the specied port-pipe.
NOTE
: The show cam-usage command provides much of the same information as the test cam-usage command, but
whether a policy-map can be successfully applied to an interface cannot be determined without rst measuring how many CAM
entries the policy-map would consume; the test cam-usage command is useful because it provides this measurement.
• Verify that there are enough available CAM entries.
test cam-usage
Example of the test cam-usage Command
Dell# test cam-usage service-policy input pmap_l2 port-set 0 | port pipe
Port-pipe | CAM Partition | Available CAM | Estimated CAM | Status
=====================================================================
0 L2ACL 500 200 Allowed(2)
Conguring Weights and ECN for WRED
The WRED congestion avoidance functionality drops packets to prevent buering resources from being consumed. Trac is a mixture of
various kinds of packets. The rate at which some types of packets arrive might be greater than others. In this case, the space on the buer
and trac manager (BTM) (ingress or egress) can be consumed by only one or few types of trac, leaving no space for other types. You
can apply a WRED prole to a policy-map so that the specied trac can be prevented from consuming too much of the BTM resources.
WRED drops packets when the average queue length exceeds the congured threshold value to signify congestion. ECN is a capability that
enhances WRED by marking the packets instead of causing WRED to drop them when the threshold value is exceeded. If you congure
ECN for WRED, devices employ ECN to mark the packets and reduce the rate of sending packets in a congested network.
In a best-eort network topology, data packets are transmitted in a manner in which latency or throughput is not maintained to be at an
eective level. Packets are dropped when the network experiences a large trac load. This best-eort network deployment is not suitable
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Quality of Service (QoS)