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The CPU Usage Is High and Traffic Measurement Fails Because of the High Sampling Rate Set on the NetStream Interfaces of the NE80 and of the Heavy Traffic on These Interfaces

Publication Date:  2012-07-27 Views:  79 Downloads:  0
Issue Description
 At a site, the measurement of traffic on the NE80 fails. Meanwhile, the CPU usage of the NetStream board is rather high. 
Alarm Information
Handling Process

1. Check the CPU usage of the board. The information displayed shows that the CPU usage is rather high at certain moments, when traffic collection fails.
[NE80-1-diag]display lpu cpuusage 15
Start to get lpu 15 Cpu usage...
Slot No. 15 Info is: 
 TSK    TID     TIME     PERCE                                                  
-----  -------  ------  ------                                                  
 IDL   fd000002     0     0%                                                    
 OST   fd000003     1     0%                                                    
 LAD   fd000006     0     0%                                                    
 ARP   fd000007     0     0%                                                    
 CON   fd000008     0     0%                                                    
 OUT   fd000009     0     0%                                                    
 DBG   fd00000c     0     0%                                                    
 DGS   fd00000d     0     0%                                                    
 NPS   fd00000e   173    34%                                                    
 IFM   fd00000f     0     0%                                                    
 INT   fd000010     0     0%                                                    
 DVM   fd000011     0     0%                                                    
 ISD   fd000012    12     2%                                                    
 IRV   fd000013     0     0%                                                    
 DEM   fd000014     1     0%                                                    
 NTR   fd000017     0     0%                                                    
 PTT   fd000019   309    61% 

2. Check the configuration of the current network. It is found that all the 20 GE interfaces of the NE80 are configured with the NetStream function for measuring the incoming traffic. In addition, the traffic is rather heavy on certain GE interfaces, reaching 300 Mbit/s.
3. When the traffic goes through a GE interface configured with the NetStream function, this interface sends the traffic to the NP of the NetStream board according to the sampling rate of 1024. After receiving the packets, the NetStream board classifies the packets and then sends these packets from its NP to its CP. After encapsulating the packets, the CP sends the packets back to the NP, which, in turn, routes the NetStream statistics packets to the NMS. If a large quantity of data is collected, the PTT task will occupy a large portion of the CPU space when the NP sends the packets to the CP, and the NPS task will occupy a large portion of the CPU space when the CP delivers the encapsulated packets to the NP. These two tasks ultimately lead to a high CPU usage of the NetStream board, hence the failure of traffic measurement.
4. Change the sampling rate of all GE interfaces by changing ip netstream sampler inbound 1024 to ip netstream sampler inbound 5000. After this operation, the CPU usage becomes normal and then the traffic can be normally measured. 

Root Cause
1. The NetStream board of the NE80 is faulty.
2. The NMS of the customer fails in information collection.
3. The traffic on the information collection interface is heavy and the traffic to be collected is of various types. 
To successfully measure the traffic on a high-end router, set a greater value for the sampling rate on the interfaces in case quite a few interfaces are configured with the NetStream function and the traffic is rather heavy on such interfaces. The value of the sampling rate may be different in different situations.