DICOM PS3.7 2019a - Message Exchange
D.3.3.5.2 SOP Class Extended Negotiation Sub-Item Structure (A-ASSOCIATE-AC)

The SOP Class Extended Negotiation Sub-item shall be made of a sequence of mandatory fields followed by the Service-class-application-information field (specific for each Service Class specification). This Sub-Item is required per the specific Service Class specifications. Multiple SOP Class Extended Negotiation Sub-Items may be present in the User Data Item of the A-ASSOCIATE-AC, however, only one Sub-Item per SOP Class UID shall be present. Table D.3-11 shows the sequence of mandatory fields.

DICOM PS3.7 2019a - Message Exchange