10.3 Protocol
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## 10.3 Protocol

This section specifies the protocol necessary to perform the set of DIMSE-N operations and notifications. The Value Representations (VR) specified in the following tables shall be encoded as defined in PS3.5.

### 10.3.1 N-EVENT-REPORT Protocol

The information necessary for the N-EVENT-REPORT request and indication DIMSE-N primitives are conveyed in the N-EVENT-REPORT-RQ Message. The information necessary for the N-EVENT-REPORT response and confirmation DIMSE-N primitives are conveyed in the N-EVENT-REPORT-RSP Message.

#### 10.3.1.1 N-EVENT-REPORT-RQ

The N-EVENT-REPORT-RQ Message contains fields as defined in Table 10.3-1. Each field shall conform to DICOM encoding and Value Representation as defined in PS3.5. Fields are required as specified in the N-EVENT-REPORT service definition unless otherwise noted in Table 10.3-1. Fields not specified in the N-EVENT-REPORT service definition but present in Table 10.3-1 are required by the DIMSE-N protocol.

Table 10.3-1. N-EVENT-REPORT-RQ Message Fields

Message Field | Tag | VR | VM | Description of Field
--- | --- | --- | --- | ---
Command Group Length | (0000,0000) | UL | 1 | The even number of bytes from the end of the value field to the beginning of the next group.
Affected SOP Class UID | (0000,0002) | UI | 1 | SOP Class UID of the SOP Instance for which this event occurred.
Command Field | (0000,0100) | US | 1 | This field distinguishes the DIMSE-N notification conveyed by this Message. The value of this field shall be set to 0100H for the N-EVENT-REPORT-RQ Message.
Message ID | (0000,0110) | US | 1 | Implementation-specific value that distinguishes this Message from other Messages.
Command Data Set Type | (0000,0800) | US | 1 | This field indicates if a Data Set is present in the Message. This field shall be set to the value of 0101H if no Data Set is present; any other value indicates a Data Set is included in the Message.
Affected SOP Instance UID | (0000,1000) | UI | 1 | Contains the UID of the SOP Instance for which this event occurred.
Event Type ID | (0000,1002) | US | 1 | Values for this field are application-specific.
Event Information | (no tag) | - | - | Application-specific Data Set containing additional information related to the operation.

### Note

1. Service Class Specifications contained in PS3.4 defines the values needed for the Event Type ID parameter.

2. Service Class Specifications contained in PS3.4 defines the Data Set needed for the Event Information parameter.

#### 10.3.1.2 N-EVENT-REPORT-RSP

The N-EVENT-REPORT-RSP Message contains fields as defined in Table 10.3-2 and Annex C. Each field shall conform to DICOM encoding and Value Representation as defined in PS3.5. Fields are required as specified in the N-EVENT-REPORT service definition unless otherwise noted in Table 10.3-2. Fields not specified in the N-EVENT-REPORT service definition but present in Table 10.3-2 are required by the DIMSE-N protocol.

Table 10.3-2. N-EVENT-REPORT-RSP Message Fields

Message Field | Tag | VR | VM | Description of Field
--- | --- | --- | --- | ---
Command Group Length | (0000,0000) | UL | 1 | The even number of bytes from the end of the value field to the beginning of the next group.
Affected SOP Class UID | (0000,0002) | UI | 1 | SOP Class UID of the SOP Instance for which this event occurred.
Command Field | (0000,0100) | US | 1 | This field distinguishes the DIMSE-N operation conveyed by this Message. The value of this field shall be set to 8100H for the N-EVENT-REPORT-RSP Message.
Message ID Being Responded To | (0000,0120) | US | 1 | Shall be set to the value of the Message ID (0000,0110) field used in associated N-EVENT-REPORT-RQ Message.
Command Data Set Type | (0000,0800) | US | 1 | This field indicates if a Data Set is present in the Message. This field shall be set to the value of 0101H if no Data Set is present; any other value indicates a Data Set is included in the Message.
Status | (0000,0900) | US | 1 | The value of this field depends upon the status type. Annex C defines the encoding of the status types defined in the service definition.
Affected SOP Instance UID | (0000,1000) | UI | 1 | Contains the UID of the SOP Instance for which this event occurred.
Event Type ID | (0000,1002) | US | 1 | Values for this field are application-specific.
Event Reply | (no tag) | - | - | Application-specific Data Set containing additional information related to the operation.

### Note

1. Service Class Specifications contained in PS3.4 defines the values needed for the Event Type ID parameter.

2. Service Class Specifications contained in PS3.4 defines the Data Set needed for the Event Reply parameter related to each defined Event Type ID.

#### 10.3.1.3 N-EVENT-REPORT Protocol Procedures

The N-EVENT-REPORT reporting procedures are initiated by the invoking DIMSE-service-user issuing an N-EVENT-REPORT request primitive. On receipt of the N-EVENT-REPORT request primitive the DIMSE-N protocol machine shall:

- construct a Message conveying the N-EVENT-REPORT-RQ

- send the Message using the P-DATA request service (see 8.1)

On receipt of a Message conveying an N-EVENT-REPORT-RQ the DIMSE-N protocol machine shall issue an N-EVENT-REPORT indication primitive to the performing DIMSE-service-user.

On receipt of the N-EVENT-REPORT response primitive issued by the performing DIMSE-service-user , the DIMSE-N protocol machine shall:

- construct a Message conveying the N-EVENT-REPORT-RSP

- send the Message using the P-DATA request service (see Section 8.1)

On receipt of a Message conveying an N-EVENT-REPORT-RSP the DIMSE-N protocol machine shall issue an N-EVENT-REPORT confirmation primitive to the invoking DIMSE-service-user, thus completing the notification procedure.

The performing DIMSE-service-user may return an N-EVENT-REPORT-RSP with the status of Failed or Refused before the complete N-EVENT-REPORT-RQ request Message has been completely transmitted by the invoking DIMSE-service-user (this is called an early failed response). Upon receipt of this Failed or Refused N-EVENT-REPORT-RSP the invoking DIMSE-service-user may terminate the Message before it is completely sent (i.e., set the Last Fragment bit to 1 in a Data PDV for this Message, see Annex F). Following this, it may invoke another operation or notification. It is a protocol violation for an invoking DIMSE-service-user to set the Last Fragment bit to 1 before an N-EVENT-REPORT-RQ Message has been completely transmitted if it has not received a Failed or Refused N-EVENT-REPORT-RSP to that request.

### Note

When an Association is operating in asynchronous mode, it is possible for an invoking DIMSE-service-user to transmit several Messages before a response. Therefore, while sending a Message it may receive a response to a previously transmitted Message. In this case this response is not an early failed response because the related Message has already been sent.

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