INT 6A - DECnet DOS LOCAL AREA TRANSPORT - OPEN SESSION                         
	AH = D0h
	DH = FFh
	AL = password flag
	    FFh no password
	    0Fh password at ES:DI
	ES:BX -> LAT session control block (see #03727)
	ES:DI -> 16-byte blank-padded password (optional)
Return: AH = 00h success
	    DL = handle
SeeAlso: AX=D000h


Format of LAT Session Control Block:
Offset	Size	Description	(Table 03727)
 00h 18 BYTEs	service name
 12h 18 BYTEs	node name (future use)
 24h 18 BYTEs	port name (future use)
 36h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> session stopped post routine
 3Ah	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> service table overflow post routine
 3Eh	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> transmit post routine
 42h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> receive post routine
 46h	WORD	session status
		04h circuit failure
		08h stop slot received
---LAT v???---
 48h	WORD	slot state (LAT driver use)
 4Ah	WORD	local credits (LAT driver use)
 4Ch	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> VCB (LAT driver use)
 50h	WORD	backward slot (LAT driver use)
 52h	WORD	forward slot (LAT driver use)
 54h	WORD	remote slot ID (LAT driver use)
 56h	WORD	local slot ID (LAT driver use)
 58h	WORD	slot byte count (LAT driver use)
 5Ah	BYTE	remote credits (LAT driver use)
 5Bh 255 BYTEs	transmitted data slot
15Ah	BYTE	number of receive data slots (4 recommended)
15Bh	BYTE	number of occupied slots
15Ch	BYTE	index of next receive slot to use
15Dh	BYTE	index of current receive slot
15Eh	WORD	pointer to first received character
160h  N WORDs	pointers to receive slots (buffers); each is 259 bytes
     259N BYTEs	buffers
Note:	set post routines to 0000h:0000h if polled operation will be used
---LAT v4.1.17---
 48h	WORD	session state (LAT driver use)
 4Ah	BYTE	local credits (LAT driver use)
 4Bh	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	-> VCB (LAT driver use)
 4Fh	WORD	backward slot (LAT driver use)
 51h	WORD	forward slot (LAT driver use)
 53h	BYTE	remote slot ID (LAT driver use)
 54h	BYTE	local slot ID (LAT driver use)
 55h	BYTE	slot byte count (LAT driver use)
 56h	BYTE	remote credits (LAT driver use)
 57h 255 BYTEs	transmitted data slot
156h	BYTE	number of receive data slots (4 recommended)
157h	BYTE	number of occupied slots
158h	BYTE	index of next receive slot to use
159h	BYTE	index of current receive slot
15Ah	WORD	pointer to first received character
15Ch  N WORDs	pointers to receive slots (buffers); each is 259 bytes
     259N BYTEs	buffers
Note:	set post routines to 0000h:0000h if polled operation will be used