F.4.2.3.3 Association Initiation Policy
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##### F.4.2.3.3 Association Initiation Policy

###### F.4.2.3.3.1 Activity - Send Storage Commitment Notification Over New Association

###### F.4.2.3.3.1.1 Description and Sequencing of Activity

The STORAGE-SCP AE will initiate a new Association if a Storage Commitment Push Model Notification (N-EVENT-REPORT) cannot be sent back over the original Association used to send the corresponding request. A new Association will always be requested by the STORAGE-SCP AE in such cases even if the peer AE requests another Association after the original has been closed (i.e., A peer AE opens an Association and sends some Storage requests and a Storage Commitment Push Model request. Before the STORAGE-SCP AE can send the Storage Commitment Push Model N-EVEN-REPORT the Association is closed. The peer AE then opens another Association and begins to send Storage requests. In such a case the STORAGE-SCP AE will always initiate a new Association to send the N-EVENT-REPORT even though it could send the N-EVENT-REPORT over the new Association opened by the peer AE).

An Association Request is sent to the peer AE that sent the Storage Commitment Push Model request and upon successful negotiation of the required Presentation Context the outstanding N-EVENT-REPORT is sent. If there are multiple outstanding N-EVENT-REPORTs to be sent to a single peer AE then the STORAGE-SCP AE will attempt to send them all over a single Association rather than requesting a new Association for each one. The Association will be released when all the N-EVENT-REPORTs for the peer AE have been sent. If any type of error occurs during transmission (either a communication failure or indicated by a Status Code returned by the peer AE) over an open Association then the transfer of N-EVENT-REPORTs is halted. A new Association will be opened to retry sending outstanding N-EVENT-REPORTs. The maximum number of times the STORAGE-SCP AE will attempt to resend an N-EVENT-REPORT is configurable, along with the amount of time to wait between attempts to resend.

If the STORAGE-SCP AE sends a Notification request (N-EVENT-REPORT-RQ) over the original Association opened by the peer AE but receives a request to close the Association rather than a response to the Notification (N-EVENT-REPORT-RSP) then this is handled in the same way as if the request to close the Association had been received before trying to send the Notification request. Thus, the STORAGE-SCP AE will then open a new Association to resend the Notification request.

The STORAGE-SCP AE can be configured to always open a new Association before sending a Storage Commitment Push Model Notifications (N-EVENT-REPORT), in which case the sequencing illustrated in Figure F.4.2-3 will always be followed.

Figure F.4.2-3. Sequencing of Activity - Send Storage Commitment Notification Over New Association

The following sequencing constraints illustrated in Figure F.4.2-3 apply to the STORAGE-SCP AE for handling Storage Commitment Push Model Requests using a new Association:

1. Peer AE opens an Association with the STORAGE-SCP AE.

2. Peer AE requests Storage Commitment of Composite SOP Instance(s) (peer sends N-ACTION-RQ and STORAGE-SCP AE responds with N-ACTION-RSP to indicate that it received the request).

3. Peer AE closes the Association before the STORAGE-SCP AE can successfully send the Storage Commitment Push Model Notification (N-EVENT-REPORT-RQ).

4. STORAGE-SCP AE opens an Association with the peer AE.

5. STORAGE-SCP AE sends Storage Commitment Push Model Notification (N-EVENT-REPORT). More than one can be sent over a single Association if multiple Notifications are outstanding.

6. STORAGE-SCP AE closes the Association with the peer AE.

The Verification Service as an SCU is only supported as a utility function for Service staff. It is used only as a diagnostic tool when the STORAGE-SCP AE is failing to open new Associations to send N-EVENT-REPORTs to peer AEs.

###### F.4.2.3.3.1.2 Proposed Presentation Contexts

STORAGE-SCP AE will propose Presentation Contexts as shown in the following table:

Table F.4.2-28. Proposed Presentation Contexts By the STORAGE-SCP AE

Presentation Context Table
Abstract Syntax | Transfer Syntax | Role | Extended Negotiation
--- | --- | --- | ---
Name | UID | Name | UID
Verification | 1.2.840.10008.1.1 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCU | None
Storage Commitment Push Model | 1.2.840.10008.1.20.1 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
Storage Commitment Push Model | 1.2.840.10008.1.20.1 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None

###### F.4.2.3.3.1.3 SOP Specific Conformance for Storage SOP Classes

The associated Activity with the Storage Commitment Push Model service is the communication by the STORAGE-SCP AE to peer AEs that it has committed to permanently store Composite SOP Instances that have been sent to it. It thus allows peer AEs to determine whether the EXAMPLE-QUERY-RETRIEVE-SERVER has taken responsibility for the archiving of specific SOP Instances so that they can be flushed from the peer AE system.

The STORAGE-SCP AE will initiate a new Association to a peer AE that sent a Storage Commitment Push Model request if the original Association over which this was sent is no longer open. For a detailed explanation of the SOP specific Behavior of the STORAGE-SCP AE in this case please refer to 4.2.4.4.1.3.3, Storage Commitment Push Model as an SCP.

###### F.4.2.3.3.1.4 SOP Specific Conformance for Verification SOP Class

Standard conformance is provided to the DICOM Verification Service Class as an SCU. The Verification Service as an SCU is actually only supported as a diagnostic service tool for network communication issues. It can be used to test whether Associations can actually be opened with a peer AE that is issuing Storage Commitment Push Model requests (i.e., to test whether the indicated TCP/IP port and AE Title for sending N-EVENT-REPORT Requests to the peer AE are truly functional).

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