Apple Device terminates connection after 30 seconds the connection establishment when reconnect with the a bonded N52832

[Bing]

Hi, I am using N52832 to developing a producation need to implements ANCS NC. I am using sdk 15.2. And I found the connection is terminated by the apple device after the reconnect with the bonded N52832. 

reconncet_30s_AAA.pcapng

The attachment is the nrf-sniffer log of the whole testing procedure. 

I found there is Encrypted packet decrypted incorrectly  (bad MIC) in the log record. The packet number 6275. And the disconnection event happened afther 30 seconds of this bad MIC report. Why this problem happen? What should I do to solve this problem.

[Jimmy Wong]

Data length extension.  It has already included the gatt_init. You can find it at the documentation of the Softdevice.

[Bing]

OK thanks. In the thread https://devzone.nordicsemi.com/f/nordic-q-a/44825/ios-mtu-size-why-only-185-bytes/176316#176316 you mentioned to comment the processing code if I modified the MTU size. That is, the peripheral device needs to wait the central device to send MTU exchange request to exchange their MTU size. If the central device won't initiate the MTU exchange request. Where should I trigger the MTU exchanging procedure?

[Jimmy Wong]

IOS will send the MTU request all the time.  but the android would not initialize the mtu request.

[Bing]

So. This is the problem. How can I know the peer device will or not  initiate MTU request?

[Jimmy Wong]

The result after the mtu exchange will send the notification event to application layer.  It can use as the indicator. 

[Bing]

My question is if no MTU exchange procedure happen, why softdevice can notify applicaiton layer? I want solve if peer device won't send ATT MTU exachange request, when should the N52832 send this request to peer device, Now it seems that we cannot send the MTU exchange request upon the connection is established. My protocol needs to know the maximum ATT payload. If no MTU exachange request send by peer device, the N52832 must initiate to send the request.