E.2 Message Control Header Encoding

E.2 Message Control Header Encoding (Current)
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The Message Control Header is located in front of each DICOM message fragment (see Figure E.2-1). Its presence is mandatory for all DICOM Abstract Syntaxes (see Annex B for further discussion on Abstract Syntaxes).

The Message Control Header shall be made of one byte with the least significant bit (bit 0) taking one of the following values:

If bit 0 is set to 1, the following fragment shall contain Message Command information.
If bit 0 is set to 0, the following fragment shall contain Message Data Set information.

The next least significant bit (bit 1) shall be defined by the following rules:

If bit 1 is set to 1, the following fragment shall contain the last fragment of a Message Data Set or of a Message Command.
If bit 1 is set to 0, the following fragment does not contain the last fragment of a Message Data Set or of a Message Command.

Bits 2 through 7 are always set to 0 by the sender and never checked by the receiver.

Note

The Message Control Header, in the Transport data flow, is the 1st byte in each PDV. The Transfer Syntax, negotiated at association establishment, defines the encoding for the Command/Data fragment.

Figure E.2-1. Presentation Data Value and the Message Control Header