3.2.5.3.6 Sending MCS Attach User Request PDU

The structure and fields of the MCS Attach User Request PDU are specified in section 2.2.1.6.

The tpktHeader field is initialized as specified in [T123] section 8, while the x224Data field (which contains an X.224 Class 0 Data TPDU) is initialized as specified in [X224] section 13.7.

The MCS Attach User Request PDU (embedded within the mcsAUrq field) is specified in [T125] section 7, parts 5 and 10.

If Enhanced RDP Security (section 5.4) is in effect, the External Security Protocol (section 5.4.5) MUST be used to encrypt the entire PDU and generate a verification digest before the PDU is transmitted over the wire.