7.1.2 A-ASSOCIATE SERVICE PROCEDURE A DICOM Application Entity (which includes the Upper Layer service-user) that desires to establish an association shall issue an A-ASSOCIATE request primitive. The called AE is identified by parameters of the request primitive. The requestor shall not issue any primitives except an A-ABORT request primitive until it receives an A-ASSOCIATE confirmation primitive. The Upper Layer (UL) service-provider shall issue an A-ASSOCIATE indication primitive to the called AE. The called AE shall accept or reject the association by sending an A-ASSOCIATE response primitive with an appropriate Result parameter. The Upper layer service-provider shall issue an A-ASSOCIATE confirmation primitive having the same Result parameter. The Result Source parameter shall be assigned the symbolic value of “UL service-user.” If the acceptor accepts the association, the association is available for use. Both AEs may now use any service provided by the DICOM application context that is in effect (with the exception of A-ASSOCIATE).

Note: This implies that once the association has been established, DICOM Messages can be exchanged as defined in PS 3.7. If the called AE rejects the association, the association shall not be established. The UL service-provider may not be capable of supporting the requested association. In this situation, it shall return an A-ASSOCIATE confirmation primitive to the requestor with an appropriate Result parameter (rejected). The Result Source parameter shall be appropriately assigned either the symbolic value of “UL service-provider (ACSE related function)” or “UL service-provider (Presentation related function).” The indication primitive shall not be issued. The association shall not be established. Either an association-requestor or acceptor may disrupt the A-ASSOCIATE service procedure by issuing an A-ABORT request primitive (see Section 7.3). The remote AE receives an A-ABORT indication primitive. The association shall not be established.