Format of APPC/PC "Request_to_Send" control block:
Offset	Size	Description	)
 00h 12 BYTEs	reserved
 0Ch	WORD	0E00h (verb "Request_to_Send" or "MC_Request_to_Send")
 0Eh	BYTE	1 if MC_ (mapped conversation) form of verb
		0 if basic verb
 0Fh  5 BYTEs	reserved (0)
 14h	WORD	(big-endian) primary return code (see #03681)
 16h	DWORD	(big-endian) error code (see #03682)
 1Ah  8 BYTEs	(big-endian) TP_ID
 22h	DWORD	(big-endian) conversation ID