9.3.3.2 Presentation Context Item Structure
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#### 9.3.3.2 Presentation Context Item Structure

The Presentation Context Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-18 shows the sequence of the mandatory fields.

The variable field shall consist of one Transfer Syntax Sub-Item.

Table 9-18. Presentation Context Item Fields

Item bytes | Field name | Description of field
--- | --- | ---
1 | Item-type | 21H
2 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
3-4 | Item-length | This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the Transfer Syntax Sub-Item. It shall be encoded as an unsigned binary number.
5 | Presentation-context-ID | Presentation-context-ID values shall be odd integers between 1 and 255, encoded as an unsigned binary number. For a complete description of the use of this field see Section 7.1.1.13.
6 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
7 | Result/Reason | This Result/Reason field shall contain an integer value encoded as an unsigned binary number. One of the following values shall be used: 0 - acceptance 1 - user-rejection 2 - no-reason (provider rejection) 3 - abstract-syntax-not-supported (provider rejection) 4 - transfer-syntaxes-not-supported (provider rejection)
8 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
9-xxx | Transfer syntax sub-item | This variable field shall contain one Transfer Syntax Sub-Item. When the Result/Reason field has a value other than acceptance (0), this field shall not be significant and its value shall not be tested when received. For a complete description of the use and encoding of this item see Section 9.3.3.2.1.

##### 9.3.3.2.1 Transfer Syntax Sub-Item Structure

The Transfer Syntax Sub-Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-19 shows the sequence of the mandatory fields.

Table 9-19. Transfer Syntax Sub-Item Fields

Item bytes | Field name | Description of field
--- | --- | ---
1 | Item-type | 40H
2 | Reserved | This reserved field shall be sent with a value 00H but not tested to this value when received.
3-4 | Item-length | This Item-length shall be the number of bytes from the first byte of the following field to the last byte of the Transfer-syntax-name field. It shall be encoded as an unsigned binary number.
5-xxx | Transfer-syntax-name | This variable field shall contain the Transfer-syntax-name proposed for this presentation context. A valid Transfer-syntax-name shall be encoded as defined in Annex F. For a description of the use of this field see Section 7.1.1.14. Transfer-syntax-names are structured as UIDs as defined in PS3.5 (see Annex B for an overview of this concept). DICOM Transfer-syntax-names are registered in PS3.5.

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