9.3.3 A-ASSOCIATE-AC PDU Structure
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### 9.3.3 A-ASSOCIATE-AC PDU Structure

An A-ASSOCIATE-AC PDU shall be made of a sequence of mandatory fields followed by a variable length field. Table 9-17 shows the sequence of the mandatory fields.

The variable field consist of one Application Context Item, one or more Presentation Context Items, and one User Information Item. Sub-Items shall exist for the Presentation Context and User Information Items.

Table 9-17. ASSOCIATE-AC PDU Fields

PDU bytes | Field name | Description of field
--- | --- | ---
1 | PDU-type | 02H
2 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
3-6 | PDU-length | This PDU-length shall be the number of bytes from the first byte of the following field to the last byte of the variable field. It shall be encoded as an unsigned binary number.
7-8 | Protocol-version | This two byte field shall use one bit to identify each version of the DICOM UL protocol supported by the calling end-system. This is Version 1 and shall be identified with bit 0 set. A receiver of this PDU implementing only this version of the DICOM UL protocol shall only test that bit 0 is set.
9-10 | Reserved | This reserved field shall be sent with a value 0000H but not tested to this value when received.
11-26 | Reserved | This reserved field shall be sent with a value identical to the value received in the same field of the A-ASSOCIATE-RQ PDU, but its value shall not be tested when received.
27-42 | Reserved | This reserved field shall be sent with a value identical to the value received in the same field of the A-ASSOCIATE-RQ PDU, but its value shall not be tested when received.
43-74 | Reserved | This reserved field shall be sent with a value identical to the value received in the same field of the A-ASSOCIATE-RQ PDU, but its value shall not be tested when received.
75-xxx | Variable items | This variable field shall contain the following items: one Application Context Item, one or more Presentation Context Item(s) and one User Information Item. For a complete description of these items see Section 7.1.1.2, Section 7.1.1.14, and Section 7.1.1.6.

#### 9.3.3.1 Application Context Item Structure

An Application Context Item shall be made of a sequence of mandatory fields followed by a variable length field. Table 9-12 shows the sequence of mandatory fields.

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9.3.2.3 User Information Item Structure | Home | 9.3.3.2 Presentation Context Item Structure