# MSPP Unsolicited Events

The following table lists the unsolicited events returned by NbUP filters:

Event | Description
MSPEVN_NBUP_INIT | Indicates the completion of Initialization phase. Could be positive acknowledgement (ACK), negative acknowledgement (NACK), or Timeout.
MSPEVN_NBUP_ERROR | Indicates an error condition during the session.

### MSPEVN_NBUP_INIT event Reason Codes

The following table summarizes the possible reason codes in MSPEVN_NBUP_INIT event:

Reason code | Description
NBUP_INIT_SUCCESS | SUCCESS
NBUP_INIT_TIMEOUT | Timeout waiting for INIT message.
NBUP_INIT_ACK_TIMEOUT | Timeout waiting for acknowledgement
NBUP_INIT_NACK | Negative acknowledgement received.

### MSPEVN_NBUP_ERROR Event Reason Codes

Reason code | Description
NBUP_ERROR_CRC_HEADER | CRC error of frame header
NBUP_ERROR_CRC_PAYLOAD | CRC error of frame payload
NBUP_ERROR_UNEXP_FRAME_NB | Unexpected frame number
NBUP_ERROR_FRAME_LOSS | Frame loss
NBUP_ERROR_UNKNOWN_PDU | PDU type unknown
NBUP_ERROR_UNKNOWN_PROC | Unknown procedure
NBUP_ERROR_UNKNOWN_RSV | Unknown reserved value
NBUP_ERROR_UNKNOWN_FIELD | Unknown field
NBUP_ERROR_FRAMME_TOO_SHORT | Frame too short
NBUP_ERROR_MISSING_FIELD | Missing fields
NBUP_ERROR_UNEXP_PDU | Unexpected PDU type
NBUP_ERROR_UNEXP_PROC | Unexpected procedure
NBUP_ERROR_UNEXP_RFCI | Unexpected RFCI
NBUP_ERROR_UNEXP_VALUE | Unexpected value
NBUP_ERROR_INIT_FAILURE | Initialization failure
NBUP_ERROR_INIT_NET_FAILURE | Initialization failure (network error, timer expiry)
NBUP_ERROR_INIT_NACK_FAILURE | Initialization failure (IuUP function error, repeated negative acknowledgement)
NBUP_ERROR_RATE_CTRL_FAILURE | Rate control failure
NBUP_ERROR_EVENT_FAILURE | Error event failure
NBUP_ERROR_TIME_ALIGNMENT_NOT_SUPP | Time Alignment not supported
NBUP_ERROR_TIME_ALIGNMENT_NOT_POSS | Requested Time Alignment not possible
NBUP_ERROR_MODE_VERSION_NOT_SUPP | IuUP Mode version not supported