Packets dropped due to the CPCAR Restriction

Publication Date:  2014-09-15 Views:  4803 Downloads:  0
Issue Description
 Version: V100R001C02B125 and earlier
The S9300 is directly connected to the competitor’s devices. The S9300 pings the peer by sending long packets with the size of 8000 bytes and packet loss occurs regularly. If the size of a packet is of the default byte, the S9300 successfully pings the peer.
Alarm Information
null
Handling Process
 The system limits the rate of sending packets to the CPU of the main control board through the CPCAR. By default, the rate limit of ICMP packets is 64 kbit/s. After the rate limit of ICMP packets is changed to 128 kbit/s, the fault is rectified.
Run the corresponding command:
The command for setting the CPCAR of packets of a type in the system view: cpcar packet-type [slot slot-number]
The command for setting the CAR of packets of a type in the CPCAR view: car cir cir-value [ cbs cbs-value ]
Root Cause
 If packet loss occurs regularly when the S9300 is directly connected to the competitor’s devices, packet loss is caused by the self-protection mechanism of the S9300.
If many protocol packets are received and sent to the main control board for processing at the same time, many CPU resources are occupied and services may be interrupted when too many CPU resources are occupied. The S9300 limits the CAR of sending protocol packets to the main control board. In this manner, the rate of sending these packets to the CPU of the main control board is limited. The self-protection mechanism is also adopted by other datacom devices.
Suggestions
In versions later than V100R001C02B125, the CPCAR of ICMP packets is changed to 192 kbit/s and the loss of long packets does not occur during the ping operation.

END