What is the lower layer protocol (LLP) used with HL7?

This is a really simple framing TCP/IP protocol. Each HL7 message is preceded with some special characters which are:

• \x0B

and is followed by these special characters:

• \x1C\x0D

These are expressed in hexadecimal.

So:

0x0B … MSH…..<hl7 message> … \0x1C\0x0D