Understanding DLE and extended ATT_MTU

[Michael]

Hello,

When using extended ATT_MTU without DLE, and the MTU is larger than the LL data length, I know that the MTU is divided into smaller LL packets when sending.

But say that I have extended ATT_MTU with DLE enabled so that, for example, data_length=127 bytes and the maximum ATT_MTU = 123 bytes.

What happens when I try to send a notification where the payload is shorter than the maximum ATT_MTU?

For example: if I send a notification where the payload is 60 bytes long. Will the LL still send a 127 bytes packet, or will it only send a 64 bytes packet?

[I am using nRF52832 with SDK v14.1 if that makes any difference.]

Thanks, Michael.

[endnode]

This should be easy to answer: no BLE layer "fills" packets with padding so already if you have Default MTU size of 23B and your Notification or Indication is <20B the PDU payload will be just what you provided from (G)ATT layer nothing more.