Zigbee end device sending leave command after receiving Transport key command

[anusha_14]

Hello Nordic support,

My application is a Zigbee coordinator application on nrf52840 based on nRF5 SDK for Thread and Zigbee v4.2.0. I was able to pair a Zigbee end device to this coordinator without any issues. However, I noticed that after a while, the coordinator sent a Transport Key command to this end device even though the end device did not request for key and after this, the Zigbee end device sent a leave command and left the network. 

I have attached the Wireshark Zigbee capture where packet number 14456 shows the Transport Key command sent by coordinator and packet number 14463 shows Zigbee end device sending leave command. 

Encryption key is 72:C1:C3:89:AD:F4:94:46:94:7F:15:51:07:71:DC:93 (Order Reverse) and Global Zigbee alliance Trust Center Link Key 5A 69 67 42 65 65 41 6C 6C 69 61 6E 63 65 30 39 (Order Normal).

I would like to get information on the following points:

1. On what occasions does the coordinator send Transport Key command without Zigbee end device requesting for Key? Is there a way to simulate this behavior to make the Zigbee coordinator send Transport Key command?

2. Why would Zigbee end device send leave command in response to Transport Key command?

Please let me know if you need more details to help in looking into this issue.

Regards,

Anusha

.trv.pcapng

 

[Maria Gilje]

Hi Anusha,

This may be tricky to get to the bottom of, but I will give it at shot. High traffic in the environment could be a cause for the ZED leaving if the traffic causes interference with ACKs.

My apologies for such a short reply at this time. I will be back with more before this weekend.

Best regards,

Maria

[Maria Gilje]

I was not able to find any good answers for you today. I appreciate your patience.

In the mean time I would like to know your reason for using nRF5 SDK for Thread and Zigbee at this point in time. Is your coordinator an older product?

I am asking because of the maintenance mode status for nRF5 SDK for Thread and Zigbee.

Best regards,

Maria

[anusha_14]

Hi Maria,

Thanks for your response. 

High traffic in the environment could be a cause for the ZED leaving if the traffic causes interference with ACKs - In case of high traffic, does it cause the coordinator to send a new Transport key command to end device without the end device sending a key request? In my case, this is what happened and I wanted to check if zigbee end device leaving in case of high traffic is as per zigbee specifications? Is there a way to avoid this from happening from coordinator side? 

In the mean time I would like to know your reason for using nRF5 SDK for Thread and Zigbee at this point in time. Is your coordinator an older product? - Yes, since we started development on our coordinator application few years ago, when nRF Connect SDK was just introduced. 

Additionally, could you please provide information for these specific points?

1. On what occasions does the coordinator send Transport Key command without Zigbee end device requesting for Key? Is there a way to simulate this behavior to make the Zigbee coordinator send Transport Key command?

2. Why would Zigbee end device send leave command in response to Transport Key command?

Looking forward to more information on this behaviour as it's a bit worrying to see the end device leaving the network and affect our deployed projects. 

Regards,

Anusha