The Asynchronous Operations Window is used to negotiate the maximum number of outstanding operation or sub-operation requests (i.e., command requests) for each direction. The synchronous operations mode is the default mode and shall be support by all DICOM AEs. This negotiation is optional.
The Association-requester conveys in the A-ASSOCIATE request:
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when negotiating the SCU role for operations, the maximum number of outstanding operations it may invoke asynchronously; when negotiating the SCP role for operations,the maximum number of outstanding sub-operations it may invoke asynchronously; when negotiating the SCP role for notifications, the maximum number of notifications it may invoke asynchronously
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when negotiating the SCP role for operations, the maximum number of outstanding operations it may invoke asynchronously; when negotiating the SCU role for operations, the maximum number of outstanding sub-operations it may perform asynchronously; when negotiating the SCU role for notifications, the maximum number of notifications it may perform asynchronously when negotiating the SCP role
A value of zero indicates that the above parameters are unlimited. If the Asynchronous Operations Window is absent the default for the above parameters shall be equal to one.
The Association-acceptor conveys in the A-ASSOCIATE response:
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when negotiating the SCP role for operations, the maximum number of outstanding operations; when negotiating the SCU role for operations, the maximum number of sub-operations it allows the Association-requester to invoke asynchronously; when negotiating the SCU role for notifications, the maximum number of outstanding notifications it allows the Association-requester to invoke asynchronously when negotiating the SCU role. This number shall be equal or less than the number of outstanding notifications, operations and/or sub-operations the Association-requester offers to invoke (by the A-ASSOCIATE indication).
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when negotiating the SCU role for operations, the maximum number of outstanding operations; when negotiating the SCP role for operations, the maximum number of sub-operations it allows the Association-requester to perform asynchronously; when negotiating the SCP role for notifications, the maximum number of outstanding notifications it allows the Association-requester to perform asynchronously. This number shall be equal or less than the number of outstanding notifications, operations and/or sub-operations the Association-requester offers to perform (by the A-ASSOCIATE indication).
A value of zero indicates that the above parameters are unlimited. If the Asynchronous Operations Window is absent the default for the above parameters shall be equal to one. Figures D.3-5 and D.3-6 illustrate examples of Asynchronous Operations Window negotiation.
If this negotiation is not present in the A-ASSOCIATE indication it shall be omitted in the A-ASSOCIATE response.
Note
The case where the Association-requester offers the value of zero (which indicates unlimited operations), the Association-acceptor may return zero (agreeing to unlimited operations) or negotiate the parameter down by conveying a value other than zero.
Figure D.3-5. Asynchronous Operations Window Negotiation (Window Being Negotiated Down By DICOM Application Entity "B")
Figure D.3-6. Asynchronous Operations Window Negotiation (Window Being Defaulted to 1, 1 By DICOM Application Entity "B")
The Asynchronous Operations Window Sub-Item shall be made of a sequence of mandatory fixed length fields. This Sub-Item is optional and if supported, only one Asynchronous Operations Window Sub-Item shall be present in the User Data Item of the A-ASSOCIATE-RQ. Table D.3-7 shows the sequence of the mandatory fields.
Table D.3-7. Asynchronous Operations Window Sub-Item Fields (A-ASSOCIATE-RQ)
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This reserved field shall be sent with a value 00H but not tested to this value when received. |
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This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the Maximum-number-operations-performed field. In the case of this Sub-Item, it shall have the fixed value of 00000004H encoded as an unsigned binary number. |
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This field shall contain the Maximum-number-operations-invoked as defined for the Association-requester in Section D.3.3.3. It shall be encoded as an unsigned binary number. |
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This field shall contain the Maximum-number-operations-performed as defined for the Association-requester in Section D.3.3.3. It shall be encoded as an unsigned binary number. |