An expanded sequence number is added to PDUs in a Bluetooth® low energy system. The expanded sequence number provides more accurate identification of the PDUs and allows the system to avoid delaying transmission of PDUs while retransmitting other PDUs. A PDU security sequence number may also be added to the PDUs. The security sequence number is used to create a unique nonce for use in encrypting or decrypting and authenticating the PDU. Using the security sequence number, a failed connection can be reestablished between two devices without the need of generating an encryption key. The security sequence number allows the devices to perform encryption or decryption and authentication using an existing key and a nonce generated from the security sequence number.