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How to Handle the Frame Freezing at a Site for a Video Investigation Team?

Publication Date:  2019-04-25 Views:  80 Downloads:  0

Issue Description

Topology information:
As shown in the following figure, the system uses the core-aggregation-access architecture. Each branch office has storage devices connected to cameras through LANs to store data collected by cameras. The gateways of all storage devices are deployed on the aggregation switch of each branch office.

Symptom
A customer reported that frame freezing occurs irregularly on some cameras on the terminal. No frame freezing occurs on the videos of all cameras on terminal A or on the videos of all cameras under branch office A on terminal B. Frame freezing occurs on many videos of the cameras under branch office M and N, but not branch office Q.

Alarm Information

Frame freezing occurs on some cameras.

Handling Process

Step 1: Learn about the customer's network topology, route planning, and video viewing mechanism at the site.
Step 2: Reproduce the fault on the site and find that the fault persists.
Step 3: The videos displayed on the terminal are the data returned by the storage devices of each branch office. Run tracert to trace the address of terminal B on the aggregation switches of branch office A, branch office M, branch office N, and branch office Q, respectively. The result shows that:
The path of data returned by a team of branch office A to terminal B is aggregation switch of branch office A → core 1→ core 2→ terminal B.

The path of data returned by a team of branch office M to terminal B is aggregation switch of branch office M → aggregation switch of branch office N → aggregation switch of branch office Q → terminal B.

The path of data returned by a team of branch office N to terminal B is aggregation switch of branch office N → aggregation switch of branch office Q → core 2 → terminal B.

The path of data returned by a team of branch office Q to terminal B is aggregation switch of branch office Q → core 2 → terminal B.

Step 4: Run tracert to trace the address of terminal A on the aggregation switches of branch office M and branch office N, respectively. The result shows that:
The path of data returned by a team of branch office M to terminal A is aggregation switch of branch office M → core 1 → aggregation switch of branch office A → terminal A.
 
The path of data returned by a team of branch office N to terminal A is aggregation switch of branch office N → aggregation switch of branch office M → core 1 → aggregation switch of branch office A → terminal A.


Step 5: Based on the preceding tracert results and fault symptom analysis, it is preliminarily determined that the interconnection between the aggregation switches of the branch offices N and Q is abnormal. At the same time, check whether the optical attenuation and CRC of the optical module on the interconnection ports of the aggregation switches of branch office N and branch office Q are normal.
Step 6: Change the path of data returned by a team of branch office M to terminal B to aggregation switch of branch office M → core 1→ core 2 → terminal B by disconnecting the links between the aggregation switches of branch office M and N.

The path of data returned by a team of branch office N to terminal B remains unchanged.

View the test result on the terminal B. Frame freezing occurs on the videos of cameras under branch office N, but not branch office M.
 
Step 7: Restore the links between the aggregation switches of branch office M and N, and wait until the links are stable. Then, disconnect the links by running shutdown to change the path of data returned by a team of branch office M to terminal B to aggregation switch of branch office M → core 1 → core 2 → terminal B,

and the path of data returned by a team of branch office N to terminal B to aggregation switch of branch office N → aggregation switch of branch office M → core 1→ core 2→ terminal B.

View the test result on terminal B. No frame freezing occurs on the videos of the cameras under branch offices M and N.
 
Step 8: Based on the preceding test results, it is determined that the fault is caused by the interconnection between the aggregation switches of branch offices N and Q.
Step 9: Further analysis shows that the aggregation switches of branch offices N and Q are interconnected through an Eth-trunk interface. By default, load balancing is performed by flow on the Eth-trunk interface. The fault is caused by an unstable physical member port of the Eth-trunk interface.


Root Cause

The fault is caused by an unstable physical member port of the Eth-trunk interface.

Solution

Replace the physical link between the aggregation switches of branch offices N and Q.

Suggestions

1. Periodically check the running status of devices on the live network, including software and hardware, so that maintenance personnel can obtain the running status of devices in a timely manner.
2. Configure the Eth-trunk mode to LACP, which can prevent UP and DOWN from occurring on two ends.


END