Long Network Latency

Symptom

When the network communication latency between the engine server and engine client is too long, the engine reports a VMI_ENGINE_EVENT_BAD_LATENCY event. A related message (the content depends on the ISV's implementation) is displayed on the GUI.

It is recommended that the network latency between the engine server and engine client be less than 80 ms to ensure optimal user experience.

Impact on the System

When this fault occurs, the engine client cannot work properly. Severe frame freezing or drawing errors may occur, which affects user experience. After reporting a VMI_ENGINE_EVENT_BAD_LATENCY event, the engine client exits.

When this fault occurs, the engine server is disconnected from the client and switches from the online state to the offline state. In the offline state, apps in the cloud phone still run. However, in this case, touch input of the engine client cannot be received, and audio/drawing instructions of apps cannot be transmitted to the engine client.

Possible Cause

The communication connection between the engine server and client depends on the ISV's implementation. The cause of long network communication latency is related to the specific network connection mechanism. Possible causes include but are not limited to the following:

• The mobile phone (engine client) is located in an area with weak signals, such as an elevator, a subway, or a garage.
• The mobile phone (engine client) switches from 4G/5G signals to Wi-Fi signals or the other way around. During the switchover, the latency increases.
• The connection between the mobile phone (engine client) and the Wi-Fi hotspot is unstable, and the packet loss rate is high.
• Network congestion or packet loss occurs on the network node between the mobile phone (engine client) and the cloud phone (engine server).

Fault Locating

• Check the network connection and signal strength of the mobile phone.
• Check the network connection and latency between the mobile phone and cloud phone.

Procedure

1. Check the network connection of the mobile phone and ensure that the Wi-Fi access or 4G/5G access of the mobile phone is normal.
2. Enter www.huawei.com in the address box of the browser on the mobile phone and check whether the web page can be opened properly.
3. Check the network signal strength of the mobile phone by viewing the network signal icon on the mobile phone.
4. Check the network latency between the mobile phone and the cloud phone. Search for "VMI_Communication: rate limited: MaxLatency = XXXX us, AverageLatency = XXXX us" in logs of the engine client.
5. When the network latency is within an acceptable range, reconnect the engine client to the engine server. The service recovers.