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故障类型 : 性能问题现象描述
1, this is a big pipe into a small pipe phenomenon, due to the big pipe is to do its own ability to send, as long as the flow inside the big pipe exceeds the flow of the small pipe, then the use of cache in the small pipe, flow back pressure, TCP window jitter and other phenomena is inevitable. When the bandwidth is bound to 3 vc12, the peak of the burst is less than the bandwidth, and the traffic will not go into the cache, so the latency is much smaller.
T2000 V2R006C03 , OSN1500 5.36.19.22 ,EFS0 2.18
Networking Overview
Failure phenomenon
Telecom MSTP bus header open line when the response delay is relatively large, the specific grouping of the network as shown in the figure above, the use of ping test and instrumentation test; test results are as follows: found that 1500 bytes of the packet to reach 37-40 milliseconds, the delay of the standard packet to reach 9-10MS;
2、Explore equipment problems, no abnormal alarms on the network element, replace the line delay after the route is unchanged;
3、Explore the version of the information, to confirm that the version of the network elements in the network version and version of the supporting table;
4、Exclude the line and equipment problems, consider the capture of the analysis of the packet
5、Capture of packet analysis, to take the binding of the time slot of 1 VC12/3 VC12 for comparison test 6、1 VC12 / 1 VC12 for comparison test 6、1 VC12 / 1 VC12 for comparison test Comparison test
6, 1 VC12 line delay: 64 bytes 4ms, 1500 bytes 29ms; 3 VC12 line delay: 64 bytes 2ms, 1500 bytes 13ms
7, the conclusion of the packet analysis data, in ping 1500 bytes is the occurrence of burst traffic to 3.5M or so, resulting in increased delay
2, ping the long packets are all bursts of peak value are more than 3.5M.
When bandwidth is bound for 1 vc12 When the bandwidth is bound to 1 vc12, because the peak value of the burst is larger than the bandwidth, the excess traffic will be stored in the cache of the single board, and then sent after there is spare bandwidth, which will increase the delay, so it causes the phenomenon of ping long packet latency increase.
