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Ping Packets Are Lost Due to Improper Configuration of CIR Parameters

Publication Date:  2012-07-27 Views:  74 Downloads:  0
Issue Description
After a user in a domain of the ME60 goes online, the user cannot open a certain Web page. When you ping the Web site from the user through large-size packets, the ping fails; When you ping the Web site from the user through small-size packets, the ping succeeds. 
Alarm Information
Handling Process
1. Check the MTU of the link. You can find that the MTU of the link is correct. The check on the users in other domains also shows that the MTU of the link is correct.
2. Compare the configurations of different domains. You can find that QoS is configured in the faulty domain. The QoS configuration in the domain is as follows:
scheduler-profile 1
car cir 512 cbs 512 pbs 10240 upstream
car cir 2048 cbs 512 pbs 10240 downstream
The stream of ping packets is 1 K, but the CBS is configured to be excessively small and cannot meet the requirement of the stream. Therefore, the large-size ping packets are discarded.
3. Change the CBS to 2 K. Then, the fault is cleared. 
Root Cause
1. The MTU on the link is not configured properly.
2. Related QoS configuration is improper. 
In addition to the improper MTU of the link, the improper QoS configuration also causes packet loss. The CBS should be greater than the CIR and the size of packets.