F.4.2.3.4 Association Acceptance Policy
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##### F.4.2.3.4 Association Acceptance Policy

###### F.4.2.3.4.1 Activity - Receive Images and Storage Commitment Requests

###### F.4.2.3.4.1.1 Description and Sequencing of Activity

The STORAGE-SCP AE accepts Associations only if they have valid Presentation Contexts. If none of the requested Presentation Contexts are accepted then the Association Request itself is rejected. It can be configured to only accept Associations with certain hosts (using TCP/IP address) and/or Application Entity Titles.

The default behavior of the STORAGE-SCP AE is to always attempt to send a Storage Commitment Push Model Notification (N-EVENT-REPORT) over the same Association opened by the peer AE to send the request (N-ACTION). If the STORAGE-SCP AE receives a request to close the Association either before sending the Notification or before receiving the corresponding N-EVENT-REPORT-RSP then it will open a new Association to send the Notification. Refer to Section F.4.2.3.4.1.5 for the details.

Figure F.4.2-4. Sequencing of Activity - Receive Images and Storage Commitment Requests

The following sequencing constraints illustrated in Figure F.4.2-4 apply to the STORAGE-SCP AE for handling Storage Commitment Push Model Requests over the original Association:

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

2. Peer AE sends zero or more Composite SOP Instances.

3. 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).

4. STORAGE-SCP AE sends Storage Commitment Push Model Notification request (N-EVENT-REPORT-RQ) and successfully receives Notification response (N-EVENT-REPORT-RSP) from peer AE.

5. Peer AE closes the Association.

If the STORAGE-SCP AE receives a request to close the Association from the peer AE before sending the Notification request (N-EVENT-REPORT-RQ) or when expecting to receive a Notification response (N-EVENT-REPORT-RSP) then it will open a new Association to send (or resend) the Notification. Refer to 0 for the details. The STORAGE-SCP AE has a configurable timeout value for the maximum amount of time that it will wait on an open Association for a new request from a peer AE. A peer AE can reset this timer by sending a Verification request (C-ECHO-RQ). This can act as a useful mechanism for a peer AE to maintain an active Association if the length of time between sending Storage or Storage Commitment requests can be long (such as when using a single Association to send images as they are acquired during an ultrasound exam).

The STORAGE-SCP AE may reject Association attempts as shown in the Table below. The Result, Source and Reason/Diag columns represent the values returned in the corresponding fields of an ASSOCIATE-RJ PDU (see Section 9.3.4 “A-ASSOCIATE-RJ PDU Structure” in PS3.8 ). The following abbreviations are used in the Source column:

1. 1 - DICOM UL service-user

2. 2 - DICOM UL service-provider (ASCE related function)

3. 3 - DICOM UL service-provider (Presentation related function)

Table F.4.2-29. Association Rejection Reasons

Result | Source | Reason/Diag | Explanation
--- | --- | --- | ---
2 - rejected-transient | c | 2 - local-limit-exceeded | The (configurable) maximum number of simultaneous Associations has been reached. An Association request with the same parameters may succeed at a later time.
2 - rejected-transient | c | 1 - temporary-congestion | No Associations can be accepted at this time due to the real-time requirements of higher priority activities (e.g., during image acquisition no Associations will be accepted) or because insufficient resources are available (e.g., memory, processes, threads). An Association request with the same parameters may succeed at a later time.
1 - rejected-permanent | a | 2 - application-context-name-not-supported | The Association request contained an unsupported Application Context Name. An association request with the same parameters will not succeed at a later time.
1 - rejected-permanent | a | 7 - called-AE-title-not-recognized | The Association request contained an unrecognized Called AE Title. An Association request with the same parameters will not succeed at a later time unless configuration changes are made. This rejection reason normally occurs when the Association initiator is incorrectly configured and attempts to address the Association acceptor using the wrong AE Title.
1 - rejected-permanent | a | 3 - calling-AE-title-not-recognized | The Association request contained an unrecognized Calling AE Title. An Association request with the same parameters will not succeed at a later time unless configuration changes are made. This rejection reason normally occurs when the Association acceptor has not been configured to recognize the AE Title of the Association initiator.
1 - rejected-permanent | b | 1 - no-reason-given | The Association request could not be parsed. An Association request with the same format will not succeed at a later time.

###### F.4.2.3.4.1.2 Accepted Presentation Contexts

The default Behavior of the STORAGE-SCP AE supports the Implicit VR Little Endian and Explicit VR Little Endian Transfer Syntaxes for all Associations. In addition, explicit JPEG (baseline lossy) compression syntax is supported for the following SOP Classes: US Image, US Multi-frame Image, US Image (retired), US Multi-frame Image (retired), VL Image, VL Multi-frame and Secondary Capture Image Storage.

The STORAGE-SCP AE can be configured to accept a subset of these Transfer Syntaxes, with the inclusion of Implicit VR Little Endian being mandatory.

If multiple Transfer Syntaxes are proposed per Presentation Context then only the most preferable Transfer Syntax is accepted. The order of Transfer Syntax preference for the STORAGE-SCP AE is configurable. The default preference order if multiple Transfer Syntaxes are proposed in a single Presentation Context is: JPEG Baseline1, Little Endian Explicit, Little Endian Implicit (if all these are proposed for a single Presentation Context). This means that if the Implicit VR Little Endian and Explicit VR Little Endian Transfer Syntaxes are proposed in a single Presentation Context then the accepted Transfer Syntax will be Explicit VR Little Endian. This order of preference is configurable.

Any of the Presentation Contexts shown in the following table are acceptable to the STORAGE-SCP AE for receiving images.

Table F.4.2-30. Accepted Presentation Contexts By 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 | SCP | 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
US Image Storage (Retired) | 1.2.840.10008.5.1.4.1.1.6 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
US Image Storage (Retired) | 1.2.840.10008.5.1.4.1.1.6 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
US Image Storage (Retired) | 1.2.840.10008.5.1.4.1.1.6 | DICOM Explicit JPEG baseline lossy compression | 1.2.840.10008.1.2.4.50 | SCP | None
US Image Storage | 1.2.840.10008.5.1.4.1.1.6.1 | DICOM Implicit VR Little Endian (uncompressed) | 1.2.840.10008.1.2 | SCP | None
US Image Storage | 1.2.840.10008.5.1.4.1.1.6.1 | DICOM Explicit VR Little Endian (uncompressed) | 1.2.840.10008.1.2.1 | SCP | None
US Image Storage | 1.2.840.10008.5.1.4.1.1.6.1 | DICOM Explicit JPEG baseline lossy compression | 1.2.840.10008.1.2.4.50 | SCP | None
US Multi-frame Storage (Retired) | 1.2.840.10008.5.1.4.1.1.3 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
US Multi-frame Storage (Retired) | 1.2.840.10008.5.1.4.1.1.3 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
US Multi-frame Storage (Retired) | 1.2.840.10008.5.1.4.1.1.3 | DICOM Explicit JPEG baseline lossy compression | 1.2.840.10008.1.2.4.50 | SCP | None
US Multi-frame Storage | 1.2.840.10008.5.1.4.1.1.3.1 | DICOM Implicit VR Little Endian (uncompressed) | 1.2.840.10008.1.2 | SCP | None
US Multi-frame Storage | 1.2.840.10008.5.1.4.1.1.3.1 | DICOM Explicit VR Little Endian (uncompressed) | 1.2.840.10008.1.2.1 | SCP | None
US Multi-frame Storage | 1.2.840.10008.5.1.4.1.1.3.1 | DICOM Explicit JPEG baseline lossy compression | 1.2.840.10008.1.2.4.50 | SCP | None
Computer Radiography Image Storage | 1.2.840.10008.5.1.4.1.1.1 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
Computer Radiography Image Storage | 1.2.840.10008.5.1.4.1.1.1 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
CT Image Storage | 1.2.840.10008.5.1.4.1.1.2 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
CT Image Storage | 1.2.840.10008.5.1.4.1.1.2 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
MR Image Storage | 1.2.840.10008.5.1.4.1.1.4 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
MR Image Storage | 1.2.840.10008.5.1.4.1.1.4 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
NM Image Storage (Retired) | 1.2.840.10008.5.1.4.1.1.5 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
Secondary Capture Image Storage | 1.2.840.10008.5.1.4.1.1.7 | DICOM Implicit VR Little Endian | 1.2.840.10008.1.2 | SCP | None
Secondary Capture Image Storage | 1.2.840.10008.5.1.4.1.1.7 | DICOM Explicit VR Little Endian | 1.2.840.10008.1.2.1 | SCP | None
Secondary Capture Image Storage | 1.2.840.10008.5.1.4.1.1.7 | DICOM Explicit JPEG lossy compression | 1.2.840.10008.1.2.4.50 | SCP | None

###### F.4.2.3.4.1.3 SOP Specific Conformance for Verification SOP Class

The STORAGE-SCP AE provides standard conformance to the Verification SOP Class as an SCP.

###### F.4.2.3.4.1.4 SOP Specific Conformance for Storage SOP Classes

The associated Activity with the Storage service is the storage of medical image data received over the network on a designated hard disk. The STORAGE-SCP AE will return a failure status if it is unable to store the images on to the hard disk.

The STORAGE-SCP AE does not have any dependencies on the number of Associations used to send images to it. Images belonging to more than one Study or Series can be sent over a single or multiple Associations. Images belonging to a single Study or Series can also be sent over different Associations. There is no limit on either the number of SOP Instances or the maximum amount of total SOP Instance data that can be transferred over a single Association.

The STORAGE-SCP AE is configured to retain the original DICOM data in DICOM Part 10 compliant file format. The STORAGE-SCP AE is Level 2 (Full) conformant as a Storage SCP. In addition, all Private and SOP Class Extended Elements are maintained in the DICOM format files. In addition to saving all Elements in files, a subset of the Elements are stored in the EXAMPLE-QUERY-RETRIEVE-SERVER database to support query and retrieval requests and also allow updating of Patient, Study, and Series information by user input, or demographic and Study related messages. Refer to the Annex for the list of Elements that are checked and/or processed upon receiving a Composite SOP Instance.

The Behavior for handling duplicate SOP Instances is configurable. The default Behavior is to assign a new SOP Instance UID to a received SOP Instance if it conflicts with an existing SOP Instance UID. An alternative configuration is possible that causes the original object with the conflicting SOP Instance UID to be replaced by the new SOP Instance. This Behavior is most commonly enabled if a Storage SCU re-sends entire Studies or Series if a single failure occurs when sending a group of SOP Instances.

For the purposes of image display the system supports the following photometric interpretations: MONOCHROME1, MONOCHROME2, RGB, PALETTE COLOR, YBR FULL 422, and YBR FULL.

It is expected that optimal Window Center and Width values are specified in the DICOM Image Objects if they have greater than 8 bits of image data stored per sample. If optimal Window Center and Width values are not provided, then the EXAMPLE-QUERY-RETRIEVE-SERVER is capable of estimating values using histogram analysis.

For multi-frame image SOP Instances sent using JPEG compression Transfer Syntax, sending a fully specified offset table increases performance, because the entire file does not have to be parsed to find the individual frame offsets. However, the inclusion of an offset table is not required for archiving or viewing of such SOP Instances.

Display of information conveyed using the DICOM Curve Module is not supported. Graphic overlay data sent either embedded in the unused image pixel data bits or in the separate Overlay Data Element is supported for display. Region of Interest overlays are not yet supported.

If an image SOP Instance specifies an aspect ratio that is not one-to-one then the image data will be automatically resized when displayed on the system monitor so that they are always displayed in a one-to-one aspect ratio.

The average throughput performance has been determined to be between 2 and 6 Mega Bytes per second on a 100 Megabit Ethernet network. Actual performance will depend greatly on the performance of the C-STORE SCU, the number of simultaneous active Associations, and the underlying network performance.

Table F.4.2-31. STORAGE-SCP AE C-STORE Response Status Return Reasons

Service Status | Further Meaning | Error Code | Reason
--- | --- | --- | ---
Success | Success | 0000 | The Composite SOP Instance was successfully received, verified, and stored in the system database.
Refused | Out of Resources | A700 | Indicates that there was not enough disk space to store the image. Error message is output to the Service Log. The SOP Instance will not be saved.
Error | Data Set does not match SOP Class | A900 | Indicates that the Data Set does not encode a valid instance of the SOP Class specified. This status is returned if the DICOM Object stream can be successfully parsed but does not contain values for one or more mandatory Elements of the SOP Class. The STORAGE-SCP AE does not perform a comprehensive check, as it only checks a subset of required Elements. In addition, if the SOP Class is for a type of image but the SOP Instance does not contain values necessary for its display then this status is returned. Error message is output to the Service Log. The system can be configured to temporarily save such Data Sets in order to aid problem diagnosis.
Cannot understand | C000 | Indicates that the STORAGE-SCP AE cannot parse the Data Set into Elements. Error message is output to the Service Log. The system can be configured to temporarily save such Data Sets in order to aid problem diagnosis.
Warning | Coercion of Data Elements | B000 | Indicates that one or more Element values were coerced. Refer to the Attributes defined in Annex for a list of those that can be coerced. Note that return of this status is disabled by default, as some SCUs treat it as an Error code rather than a Warning.

### Note

If a failure condition does occur when handling an Association then all images previously received successfully over the Association are maintained in the EXAMPLE-QUERY-RETRIEVE-SERVER database. No previously successfully received images are discarded. Even if an image is successfully received but an error occurs transmitting the C-STORE Response then this final image is maintained rather than discarded. If the loss of an Association is detected then the Association is closed.

The Behavior of STORAGE-SCP AE during communication failure is summarized in the following table:

Table F.4.2-32. STORAGE-SCP AE Storage Service Communication Failure Reasons

Exception | Reason
--- | ---
Timeout expiry for an expected DICOM Message Request (DIMSE level timeout). I.e. The STORAGE-SCP AE is waiting for the next C-STORE Request on an open Association but the timer expires. | The Association is aborted by issuing a DICOM A-ABORT. Error message is output to the Service Log. If some Composite SOP Instances have already been successfully received then they are maintained in the database. They are not automatically discarded because of a later failure.
Timeout expiry for an expected DICOM PDU or TCP/IP packet (Low-level timeout). I.e. The STORAGE-SCP AE is waiting for the next C-STORE Data Set PDU but the timer expires. | The Association is aborted by issuing a DICOM A-ABORT. Error message is output to the Service Log. If a C-STORE Data Set has not been fully received then the data already received is discarded. If some Composite SOP Instances have already been successfully received over the Association then they are maintained in the database.
Association aborted by the SCU or the network layers indicate communication loss (i.e., low-level TCP/IP socket closure) | Error message is output to the Service Log. If some Composite SOP Instances have already been successfully received then they are maintained in the database. They are not automatically discarded because of a later failure.

###### F.4.2.3.4.1.5 SOP Specific Conformance for Storage Commitment SOP Class

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 takes the list of Composite SOP Instance UIDs specified in a Storage Commitment Push Model N-ACTION Request and checks if they are present in the EXAMPLE-QUERY-RETRIEVE-SERVER database. As long as the Composite SOP Instance UIDs are present in the database, the STORAGE-SCP AE will consider those Composite SOP Instance UIDs to be successfully archived. The STORAGE-SCP AE does not require the Composite SOP Instances to actually be successfully written to archive media in order to commit to responsibility for maintaining these SOP Instances.

Once the STORAGE-SCP AE has checked for the existence of the specified Composite SOP Instances, it will then attempt to send the Notification request (N-EVENT-REPORT-RQ). The default behavior is to attempt to send this Notification over the same Association that was used by the peer AE to send the original N-ACTION Request. If the Association has already been released or Message transfer fails for some reason then the STORAGE-SCP AE will attempt to send the N-EVENT-REPORT-RQ over a new Association. The STORAGE-SCP AE will request a new Association with the peer AE that made the original N-ACTION Request. The STORAGE-SCP AE can be configured to always open a new Association in order to send the Notification request.

The STORAGE-SCP AE will not cache Storage Commitment Push Model N-ACTION Requests that specify Composite SOP Instances that have not yet been transferred to the EXAMPLE-QUERY-RETRIEVE-SERVER. If a peer AE sends a Storage Commitment Push Model N-ACTION Request before the specified Composite SOP Instances are later sent over the same Association, the STORAGE-SCP AE will not commit to responsibility for such SOP Instances.

The STORAGE-SCP AE does not support the optional Storage Media File-Set ID & UID attributes in the N-ACTION.

The EXAMPLE-QUERY-RETRIEVE-SERVER never automatically deletes Composite SOP Instances from the archive. The absolute persistence of SOP Instances and the maximum archiving capacity for such SOP Instances is dependent on the archiving media and capacity used by the EXAMPLE-QUERY-RETRIEVE-SERVER and is dependent on the actual specifications of the purchased system. It is necessary to check the actual system specifications to determine these characteristics.

The STORAGE-SCP AE will support Storage Commitment Push Model requests for SOP Instances of any of the Storage SOP Classes that are also supported by the STORAGE-SCP AE:

Table F.4.2-33. Supported Referenced SOP Classes in Storage Commitment Push Model N-ACTION Requests

Supported Referenced SOP Classes
US Image Storage (Retired)
US Image Storage
US Multi-frame Storage (Retired)
US Multi-frame Storage
Computed Radiography Image Storage
CT Image Storage
MR Image Storage
Secondary Capture Image Storage

The STORAGE-SCP AE will return the following Status Code values in N-ACTION Responses:

Table F.4.2-34. STORAGE-SCP AE Storage Commitment Push Model N-ACTION Response Status Return Behavior

Service Status | Further Meaning | Error Code | Behavior
--- | --- | --- | ---
Success | Success | 0000 | The SCP has successfully received the Storage Commitment Push Model N-ACTION Request and can process the commitment request for the indicated SOP Instances.
Error | Processing Failure | 0110 | Indicates that the Storage Commitment Push Model N-ACTION Request cannot be parsed or fully processed due to a database or system failure.
Error | Missing Attribute | 0120 | Indicates that the Storage Commitment Push Model N-ACTION Request cannot be processed because a required attribute is missing from the N-ACTION Request Data Set.
Error | Missing Attribute Value | 0121 | Indicates that the Storage Commitment Push Model N-ACTION Request cannot be processed because a Type 1 attribute in the N-ACTION Request Data Set does not specify a value.

The STORAGE-SCP AE will exhibit the following Behavior according to the Status Code value returned in an N-EVENT-REPORT Response from a destination Storage Commitment Push Model SCU:

Table F.4.2-35. STORAGE-SCP AE N-EVENT-REPORT Response Status Handling Behavior

Service Status | Further Meaning | Error Code | Behavior
--- | --- | --- | ---
Success | Success | 0000 | The SCU has successfully received the Storage Commitment Push Model N-EVENT-REPORT Request. Success indication message is output to the Service Logs. No message is posted to the User Interface.
Warning | Attribute List Error | 0107 | Transmission of Storage Commitment Push Model N-EVENT-REPORT Request is considered successful. Warning indication message is output to the Service Logs. No message is posted to the User Interface.
* | * | Any other status code. | This is treated as a permanent Failure. Error indication message is output to the Service Logs. No message is posted to the User Interface.

All Status Codes indicating an error or refusal are treated as a permanent failure. The STORAGE-SCP AE can be configured to automatically reattempt the sending of Storage Commitment Push Model N-EVENT-REPORT Requests if an error Status Code is returned or a communication failure occurs. The maximum number of times to attempt sending as well as the time to wait between attempts is configurable.

Table F.4.2-36. STORAGE-SCP AE Storage Commitment Push Model Communication Failure Behavior

Exception | Behavior
--- | ---
Timeout expiry for an expected DICOM Message Request (DIMSE level timeout). I.e. The STORAGE-SCP AE is waiting for the next N-ACTION Request on an open Association but the timer expires. | The Association is aborted by issuing a DICOM A-ABORT. If some Composite SOP Instances have been successfully received over the same Association via the Storage Service then they are maintained in the database. They are not automatically discarded because of a later Storage Commitment messaging failure. Any previously received Storage Commitment Push Model N-ACTION Requests will still be fully processed. Error indication message is output to the Service Logs. No message is posted to the User Interface.
Timeout expiry for an expected DICOM Message Response (DIMSE level timeout). I.e. The STORAGE-SCP AE is waiting for the next N-EVENT-REPORT Response on an open Association but the timer expires. | The Association is aborted by issuing a DICOM A-ABORT. If some Composite SOP Instances have been successfully received over the same Association via the Storage Service then they are maintained in the database. They are not automatically discarded because of a later Storage Commitment messaging failure. Any previously received Storage Commitment Push Model N-ACTION Requests will still be fully processed. Error indication message is output to the Service Logs. No message is posted to the User Interface.
Timeout expiry for an expected DICOM PDU or TCP/IP packet (Low-level timeout). | The Association is aborted by issuing a DICOM A-ABORT. If some Composite SOP Instances have been successfully received over the same Association via the Storage Service then they are maintained in the database. They are not automatically discarded because of a later Storage Commitment messaging failure. Any previously received Storage Commitment Push Model N-ACTION Requests will still be fully processed. Error indication message is output to the Service Logs. No message is posted to the User Interface.
Association A-ABORTed by the SCU or the network layers indicate communication loss (i.e., low-level TCP/IP socket closure) | The TCP/IP socket is closed. If some Composite SOP Instances have been successfully received over the same Association via the Storage Service then they are maintained in the database. They are not automatically discarded because of a later Storage Commitment messaging failure. Any previously received Storage Commitment Push Model N-ACTION Requests will still be fully processed. Error indication message is output to the Service Logs. No message is posted to the User Interface.

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