9.2.3 DICOM UPPER LAYER PROTOCOL FOR TCP/IP STATE TRANSITION TABLE

The DICOM Upper Layer Protocol State transitions are specified in Table 9-10. This table addresses both the normal and error cases for the protocol operation. Both the called and the calling aspects of an association are described in this table.

Table 9-10 DICOM UPPER LAYER PROTOCOL STATE TRANSITION TABLE

STATES No assocn Association establishment Data transfer Association release (normal & collision) Wait for Tp Close
EVENTS Sta1 Sta2
1 PDU-type 01H
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 Called-AE-title Destination DICOM Application Name. It shall be encoded as 16 characters as defined by the ISO 646:1990-Basic G0 Set with leading and trailing spaces (20H) being non-significant. The value made of 16 spaces (20H) meaning “no Application Name specified” shall not be used. For a complete description of the use of this field, see Section 7.1.1.4.
27-42 Calling-AE-title Source DICOM Application Name. It shall be encoded as 16 characters as defined by the ISO 646:1990-Basic G0 Set with leading and trailing spaces (20H) being non-significant. The value made of 16 spaces (20H) meaning “no Application Name specified” shall not be used. For a complete description of the use of this field, see Section 7.1.1.3.
43-74 Reserved This reserved field shall be sent with a value 00H for all bytes but not tested to this value when received
75-xxx Variable items This variable field shall contain the following items: one Application Context Item, one or more Presentation Context Items and one User Information Item. For a complete description of the use of these items see Sections 7.1.1.2, 7.1.1.13, and 7.1.1.6.

9.3.2.1 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 the mandatory fields.

Table 9-12 APPLICATION CONTEXT ITEM FIELDS

Item bytes Field name Description of field
1 Item-type 10H
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 Application-context-name field. It shall be encoded as an unsigned binary number.
5-xxx Application-context-name A valid Application-context-name shall be encoded as defined in Annex F. For a description of the use of this field see Section 7.1.1.2. Application-context-names are structured as UIDs as defined in PS 3.5 (see Annex A for an overview of this concept). DICOM Application-context-names are registered in PS 3.7.

9.3.2.2 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 9-13 shows the sequence of the mandatory fields.

The variable field shall consist of one Abstract Syntax Sub-Item followed by one or more Transfer Syntax Sub-Items.

Table 9-13 PRESENTATION CONTEXT ITEM FIELDS

Item bytes Field name Description of field
1 Item-type 20H
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 last Transfer Syntax 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 Reserved This reserved field shall be sent with a value 00H but not tested to this value when received.
8 Reserved This reserved field shall be sent with a value 00H but not tested to this value when received.
9-xxx Abstract/Transfer Syntax Sub-Items This variable field shall contain the following sub-items: one Abstract Syntax and one or more Transfer Syntax(es). For a complete description of the use and encoding of these sub-items see Sections 9.3.2.2.1 and 9.3.2.2.2.

9.3.2.2.1 Abstract syntax sub-item structure

The Abstract Syntax Sub-Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-14 shows the sequence of the mandatory fields.

Table 9-14 ABSTRACT SYNTAX SUB-ITEM FIELDS

Item bytes Field name Description of field
1 Item-type 30H
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 Abstract-syntax-name field. It shall be encoded as an unsigned binary number.
5-xxx Abstract-syntax-name This variable field shall contain the Abstract-syntax-name related to the proposed presentation context. A valid Abstract-syntax-name shall be encoded as defined in Annex F. For a description of the use of this field see Section 7.1.1.13. Abstract-syntax-names are structured as UIDs as defined in PS 3.5 (see Annex B for an overview of this concept). DICOM Abstract-syntax-names are registered in PS 3.4.

9.3.2.2.2 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 9-15 shows the sequence of the mandatory fields.

Table 9-15 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(s). It shall be encoded as an unsigned binary numbers
5-xxx Transfer-syntax-name(s) 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 7.1.1.13. Transfer-syntax-names are structured as UIDs as defined in PS 3.5 (see Annex B for an overview of this concept). DICOM Transfer-syntax-names are registered in PS 3.5.

9.3.2.3 User information item structure

The User Information Item shall be made of a sequence of mandatory fixed length fields followed by a variable field. Table 9-16 shows the sequence of the mandatory fields.

The variable field shall consist of one or more User-Data Sub-Items.

Note: The User-Data Sub-Items may be present in any order within the User-Information Item. No significance should be placed on the order of User-Data Sub-Items within the User Information Item. Sending applications should be aware that some older applications might expect Sub-Items to be encoded in ascending order of Item-type within the enclosing Item.

Table 9-16 USER INFORMATION ITEM FIELDS

Item bytes Field name Description of field
1 Item-type 50H
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 User-data field(s). It shall be encoded as an unsigned binary number.
5-xxx User-data This variable field shall contain User-data sub-items as defined by the DICOM Application Entity. The structure and content of these sub-items is defined in Annex D.