8 Protocol overview

8.1 DIMSE protocol

This Section provides an overview of the DIMSE protocol machine. The DIMSE protocol machine defines the procedures and the encoding rules necessary to construct Messages used to exchange command requests and responses between peer DIMSE-service-users (e.g. two DICOM Application Entities). The relationship between Messages and the different types of service primitives is shown in Figure 7-1.

The DIMSE protocol machine accepts DIMSE-service-user request and response service primitives and constructs Messages defined by the procedures defined in 9.3 and 10.3. The DIMSE protocol machine accepts Messages and passes them to the DIMSE-service-user by the means of indication and confirmation service primitives.

Procedures define the rules for the transfer of Messages that convey command requests and responses. These rules define interpretation of the various fields in the command part of the Message. They do not define what an invoking DIMSE-service-user should do with the information (the Data Set part of the Message) it requested nor how a performing DIMSE-service-user should process the operation.

Messages may be fragmented. The fragmentation of Messages exchanged between peer DICOM Application Entities and the P-DATA service used to exchange these Message fragments are defined in Annex F.

Note: These Message fragments are called Application Protocol Data Units (APDUs) by the OSI construct.

The invoking DIMSE-service-user request primitive results in a Message carrying a Command Request (with an optional associated Data Set). Each Message induces an indication primitive to the performing DIMSE-service-user.

The performing DIMSE-service-user response primitives result in a Message carrying a Command Response (with an optional associated Data Set). Each Message induces a confirmation primitive to the invoking DIMSE-service-user.

8.2 Association protocol

The establishment of an Association involves two DIMSE-service-users, one which is the Association-requester and one which is the Association-acceptor. A DIMSE-service-user may initiate an Association establishment by using the A-ASSOCIATE service described in PS 3.8.

Included in the parameters of the A-ASSOCIATE service is the Application Context which specifies, among other things, the rules required for the coordination of initialization information corresponding to different DICOM Application Entities. The Application Contexts permitted for DIMSE are specified in Annex A.

8.3 Conformance

Implementors conform to the DIMSE protocol only by conformance to a SOP class as defined in PS 3.2 and PS 3.4. Implementors do not conform directly to the DIMSE protocol, and are not required to include a statement about DIMSE conformance in conformance statements except as required in PS 3.4.