MLP is how an application should wrap an HL7 message to ensure HL7 compliant applications know where a message starts, where a message stops, and where the next message starts.
MLP places a wrapper (i.e., a header and a trailer) around each HL7 message prior to sending the message via TCP/IP. This wrapping is recommended because TCP/IP is a “stream-oriented” protocol and HL7 messages are atomic. The header is a vertical tab character <VT> its hex value is 0×0b. The trailer is a file separator character <FS> (hex 0×1c) immediately followed by a carriage return <CR> (hex 0×0d)