The RDP documents are available under the “Windows Protocols”, “Windows Communication Protocols (MCPP)”
You can access these either online at http://msdn.microsoft.com/en-us/library/cc240445.aspx or by downloading the “Windows Communication Protocols (MCPP)” package and extracting the documents from the zip package.
Click here to view this version of the [MS-RDPBCGR] PDF.