# Messages decoded by dectrace

dectrace decodes ISDN layer 3 messages in accordance with Q.931/Q.932 specifications, except where noted.

## Q.931/Q.932 message types

dectrace decodes all the messages types defined in the Q.931/Q.932 specifications. The following table lists the messages types:

Message | Hexadecimal value | Notes
--- | --- | ---
Escape to nationally specific message type:
MSG_ESCAPE | 0x00 | Q.931
Call establishing messages:
MSG_ALERTING | 0x01 | Q.931
MSG_CALL_PROC | 0x02 | Q.931
MSG_PROGRESS | 0x03 | Q.931
MSG_SETUP | 0x05 | Q.931
MSG_CONNECT | 0x07 | Q.931
MSG_SETUP_ACK | 0x0D | Q.931
MSG_CONNECT_ACK | 0x0F | Q.931
Call information phase messages:
MSG_USER_INFO | 0x20 | Q.931
MSG_SUSPEND_REJ | 0x21 | Q.931
MSG_RESUME_REJ | 0x22 | Q.931
MSG_HOLD | 0x24 | Q.932
MSG_SUSPEND | 0x25 | Q.931
MSG_RESUME | 0x26 | Q.931
MSG_HOLD_ACK | 0x28 | Q.932
MSG_SUSPEND_ACK | 0x2D | Q.931
MSG_RESUME_ACK | 0x2E | Q.931
MSG_HOLD_REJ | 0x30 | Q.932
MSG_RETRIEVE | 0x31 | Q.932
MSG_RETRIEVE_ACK | 0x33 | Q.932
MSG_RETRIEVE_REJ | 0x37 | Q.932
Call clearing messages:
MSG_DISCONNECT | 0x45 | Q.931
MSG_RESTART | 0x46 | Q.931
MSG_RELEASE | 0x4D | Q.931
MSG_RESTART_ACK | 0x4E | Q.931
MSG_RELEASE_COMP | 0x5A | Q.931
Miscellaneous messages:
MSG_SEGMENT | 0x60 | Q.931
MSG_FACILITY | 0x62 | Q.931
MSG_REGISTER | 0x34 | Q.932
MSG_NOTIFY | 0x6E | Q.931
MSG_STATUS_ENQ | 0x75 | Q.931
MSG_CONGESTION_CTRL | 0x79 | Q.931
MSG_INFO | 0x7B | Q.931
MSG_STATUS | 0x7D | Q.931
Messages not defined in Q.931/Q.932:
MSG_SERVICE | 0x0F | According to 235-900-342 (5ESS)
MSG_SERVICE_ACK | 0x07 | According to 235-900-342 (5ESS)

## Information elements

dectrace decodes all the information element identifiers defined in the Q.931/Q.932 specifications. The following table lists the information element identifiers:

Message | Hexadecimal value | Notes
--- | --- | ---
Single octet information elements:
IE_SHIFT | 0x90 | All values from 0x90 to 0x9F indicate shift
IE_MORE_DATA | 0xA0 | More data
IE_SENDING_COMPL | 0xA1 | Sending complete
IE_CONG_LEVEL | 0xB0 | All values from 0xB0 to 0xBF indicate congestion level
IE_REPEAT_IND | 0xD0 | All values from 0xD0 to 0xDF indicate repeat indicator
Variable length information elements:
IE_SEGMENTED | 0x00 | Segmented message
IE_BC | 0x04 | Bearer capability
IE_CAUSE | 0x08 | Cause
IE_CONNECTED | 0xC | Connected party number
IE_CALL_ID | 0x10 | Call identity
IE_CALL_STATE | 0x14 | Call state
IE_CHANNEL_ID | 0x18 | Channel identification
IE_FACILITY | 0x1C | Facility
IE_PROGRESS_IND | 0x1E | Progress indicator
IE_NSF | 0x20 | Network-specific facilities
IE_NOTIFY_IND | 0x27 | Notification indicator
IE_DISPLAY | 0x28 | Display
IE_DATE_TIME | 0x29 | Date/time
IE_KEYPAD | 0x2C | Keypad facility
IE_INFO_RQ | 0x32 | Information request
IE_SIGNAL | 0x34 | Signal
IE_SWITCHHOOK | 0x36 | Switchhook
IE_FEATURE_ACK | 0x38 | Feature activation
IE_FEATURE_IND | 0x39 | Feature indication
IE_SERVICE_PROF | 0x3A | Service profile identification
IE_ENDPOINT_ID | 0x3B | Endpoint identifier
IE_INFO_RATE | 0x40 | Information rate
IE_END_TO_END_DELAY | 0x42 | End to end transit delay
IE_TDSI | 0x43 | Transit delay selection and indication
IE_PKT_BIN_PAR | 0x44 | Packet layer binary parameters
IE_PKT_WIN_SIZE | 0x45 | Packet layer window size
IE_PKT_SIZE | 0x46 | Packet size
IE_MIN_THR_CLASS | 0x47 | Minimum throughput class
IE_CONNECTED_QSIG | 0x4C | Connected party number (QSIG)
IE_CALLING | 0x6C | Calling party number
IE_CALLING_SUB | 0x6D | Calling party subaddress
IE_CALLED | 0x70 | Called party number
IE_CALLED_SUB | 0x71 | Called party subaddress
IE_ORIG_CALLED | 0x73 | Original called number
IE_REDIRECTING | 0x74 | Redirecting number
IE_REDIRECTION | 0x76 | Redirection number
IE_TRANSIT_SEL | 0x78 | Transit network selection
IE_REST_IND | 0x79 | Restart indicator
IE_LLC | 0x7C | Low layer compatibility
IE_HLC | 0x7D | High layer compatibility
IE_UUI | 0x7E | User-to-user information
IE_ESCAPE | 0xFF | Escape for extension
Information elements not defined in Q.931/Q.932:
IE_CHANGE_STATUS | 0x01 | Change status according to 235-900-342 (5ESS)

If the program does not decode the contents of an information element, it displays:

IE ie_name: NOT DECODED

If the program does not decode the contents of one octet inside one information element, it displays:

octet octet_number: NOT DECODED

If dectrace encounters a value in the message type, the information element ID, or the information element contents that:

- Is not in accordance with the Q.931/Q.932 specifications (except where noted differently), it displays RESERVED.

- It does not recognize, it displays UNKNOWN. Unknown represents a legal value for several fields.

Note: The presence of RESERVED or UNKNOWN fields in the program output does not necessarily indicate a failure. Values that are illegal in the Q.931/Q.932 specification may be legal depending on the variant you are running.