MLLP Transmission Mode

This transmission mode implements the Minimal Lower Layer Protocol (MLLP) specified by HL7, and is often used when transmitting HL7 v2.x messages. There are two versions of MLLP, v1 and v2. The first version is similar to the Basic TCP Transmission Mode in that it only specifies sequences for the start/end message bytes.

The second version builds on the first with "reliable delivery assurance", by having each system send a protocol-level ACK or NAK immediately after every received frame.

By default only MLLPv1 is enabled, as it is the most common use-case.

Item	Name	Default Value	Description
A	Start of Message Bytes	0x0B <VT>)	The MLLP Start Block bytes before the beginning of the actual message. Only valid hexadecimal characters (0-9, A-F) are allowed.
B	End of Message Bytes	0x1C0D (<FS><CR>)	The MLLP End Data/Block bytes after the end of the actual message. Only valid hexadecimal characters (0-9, A-F) are allowed.
C	Use MLLPv2	No	Select Yes to use the MLLPv2 bi-directional transport layer, which includes reliable delivery assurance as per the HL7 specifications.
D	Commit ACK Bytes	0x06 (<ACK>)	The MLLPv2 Affirmative Commit Acknowledgement bytes to expect after successfully sending a message, and to send after successfully receiving a message. Only valid hexadecimal characters (0-9, A-F) are allowed.
E	Commit NACK Bytes	0x15 (<NAK>)	The MLLPv2 Negative Commit Acknowledgement bytes to expect after unsuccessfully sending a message, and to send after unsuccessfully receiving a message. Only valid hexadecimal characters (0-9, A-F) are allowed.
F	Max Retry Count	2	The maximum number of time to retry unsuccessful dispatches before giving up and logging an error.

MLLP Transmission Mode

Recommendations

TCP Transmission Modes

Basic TCP Transmission Mode

Byte Abbreviations

Outbound Properties

Standard Variables/Templates

HL7 v2.x Data Type

MLLP Transmission Mode