Материал: part07

D.3.3.3 Asynchronous Operations (And Sub-Operations) Window Negotiation​

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 supported by all​ DICOM AEs. This negotiation is optional.​

The Association-requester conveys in the A-ASSOCIATE request:​

•​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​

•​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. A value of one indicates that there is no Asynchronous Operations​ support. 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:​

•​when negotiating the SCP role for operations, the maximum number of outstanding operations; when negotiating the SCU role for​ operations,themaximumnumberofsub-operationsitallowstheAssociation-requestertoinvokeasynchronously;whennegotiating​ 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).​

•​when negotiating the SCU role for operations, the maximum number of outstanding operations; when negotiating the SCP role for​ operations,themaximumnumberofsub-operationsitallowstheAssociation-requestertoperformasynchronously;whennegotiating​ 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 nego-​ tiation.​

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.​

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FigureD.3-5.AsynchronousOperationsWindowNegotiation(WindowBeingNegotiatedDownByDICOM​

Application Entity "B")​

DICOM AE “A”

FigureD.3-6.AsynchronousOperationsWindowNegotiation(WindowBeingDefaultedto1,1ByDICOM​

Application Entity "B")​

D.3.3.3.1 Asynchronous Operations Window Sub-Item Structure (A-ASSOCIATE-RQ)​

The Asynchronous Operations Window Sub-Item shall be made of a sequence of mandatory fixed length fields. This Sub-Item is op-​ tional and if supported, only one Asynchronous Operations Window Sub-Item shall be present in the User Data Item of the A-ASSO-​ CIATE-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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D.3.3.3.2 Asynchronous Operations Window Sub-Item Structure (A-ASSOCIATE-AC)​

The Asynchronous Operations Window Sub-Item shall be made of a sequence of mandatory fixed length fields. This Sub-Item is op-​ tional and if supported, only one Asynchronous Operations Window Sub-Item shall be present in the User Data Item of the A-ASSO-​ CIATE-AC. Table D.3-8 shows the sequence of the mandatory fields.​

Table D.3-8. Asynchronous Operations Window Sub-Item Fields (A-ASSOCIATE-AC)​

7-8​ Maximum-number-operations-performed​This field shall contain the Maximum-number-operations-performed as​ definedfortheAssociation-acceptorinSectionD.3.3.3.Itshallbeencoded​ as an unsigned binary number.​

D.3.3.4 SCP/SCU Role Selection Negotiation​

The SCP/SCU role selection negotiation allows peer AEs to negotiate the roles in which they will serve for each SOP Class or Meta​ SOP Class supported on the Association. This negotiation is optional.​

The Association-requester, for each SOP Class UID or Meta SOP Class UID, may use one SCP/SCU Role Selection item. The SOP​ Class or Meta SOP Class shall be identified by its corresponding Abstract Syntax Name followed by one of the three role values:​

•​Association-requester is SCU only​

•​Association-requester is SCP only​

•​Association-requester is both SCU and SCP​

If the SCP/SCU Role Selection item is absent the default role of the Association-requester shall be SCU and the default role of the​ Association-acceptor shall be SCP.​

The Association-acceptor, for each SCP/SCU Role Selection item offered, either accepts the Association-requester proposal by re-​ turning the same value (1) or turns down the proposal by returning the value (0). The Association-acceptor shall not return the value​

(1)iftheAssociation-requesterhasnotproposedtherole,i.e.,ithassentavalue(0).TheAssociation-requestershallignoretheresponse​ if it has not proposed the role.​

If the SCP/SCU Role Selection item is not returned by the Association-acceptor then the role of the Association-requester shall be​ SCU and the role of the Association-acceptor shall be SCP. Figure D.3-7 illustrates the SCP/SCU Role Selection negotiation.​

IftheSCP/SCURoleSelectionitemsdonotexistintheA-ASSOCIATEindicationtheyshallbeomittedintheA-ASSOCIATEresponse.​

Note​

1.​ThechoicesmadeforthedefaultrolesarebasedonclarificationmadetopreviousversionsoftheStandard.Association-​ requesters that wish to offer Abstract Syntax Names using the SCP role must support this item. Association-acceptors​ that wish to accept Abstract Syntax Names using the SCU role must support this item.​

2.​If an Association-requestor offers an SCP/SCU Role Selection item for an Abstract Syntax Name but the Association-​ acceptor does not return a SCP/SCU Role Selection item for the same Abstract Syntax Name then the proposed roles​

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have not been accepted and the default roles apply (i.e., Association-requester is SCU and Association-acceptor is​ SCP).​

DICOM AE “A”

Figure D.3-7. SCU/SCP Role Negotiation​

Note​

1.​DICOM AE "B" accepts DICOM AE "A"'s proposed role as an SCU for the Storage-MR SOP; therefore, DICOM AE "B"​ will perform in the SCP role. DICOM AE "B" turns down the SCP proposal from DICOM AE "A".​

2.​Both DICOM AEs may be SCU and SCP for the Storage-CT SOP.​

3.​DICOM AE "B" accepts DICOM AE "A"'s proposed role as an SCU for the Print-SOP; therefore, DICOM AE "B" will​ perform in the SCP role.​

D.3.3.4.1 SCP/SCU Role Selection Sub-Item Structure (A-ASSOCIATE-RQ)​

The SCP/SCU Role Selection Sub-Item shall be made of a sequence of mandatory fields. This Sub-Item is optional and if supported,​ one or more SCP/SCU Role Selection Sub-Items may be present in the User Data Item of the A-ASSOCIATE-RQ. The Association-​ requester may only offer one SOP Class SCP/SCU Role Selection Sub-Item for each SOP Class UID or Meta SOP Class that is​ present in the A-ASSOCIATE request. Table D.3-9 shows the sequence of the mandatory fields.​

Table D.3-9. SCP/SCU Role Selection Sub-Item Fields (A-ASSOCIATE-RQ)​

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D.3.3.4.2 SCP/SCU Role Selection Sub-Item Structure (A-ASSOCIATE-AC)​

The SCP/SCU Role Selection Sub-Item shall be made of a sequence of mandatory fields. This Sub-Item is optional and if supported,​ one or more SCP/SCU Role Selection Sub-Items may be present in the User Data Item of the A-ASSOCIATE-AC. Table D.3-10​ shows the sequence of the mandatory fields.​

Table D.3-10. SCP/SCU Role Selection Sub-Item Fields (A-ASSOCIATE-AC)​

D.3.3.5 Service-Object Pair (SOP) Class Extended Negotiation​

The SOP Class Extended Negotiation allows, at Association establishment, peer DICOM AEs to exchange application information​ defined by specific Service Class specifications. This is an optional feature that various Service Classes may or may not choose to​ support.​

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