INT 5B - AT&T Starlan Extended NetBIOS (variable length names)
        ES:BX -> Network Control Block (see below)
Return: AL = status (see INT 5C)

Format of Network Control Block
Offset  Size    Description
 00h    BYTE    ncb_command (see below)
 01h    BYTE    ncb_retcode
 02h    BYTE    ncb_lsn
 03h    BYTE    ncb_num
 04h    DWORD   -> ncb_buffer
 08h    WORD    ncb_length
 0Ah 16 BYTEs   ncb_callname
 1Ah 16 BYTEs   ncb_name
 2Ah    BYTE    ncb_rto
 2Bh    BYTE    ncb_sto
 2Ch    DWORD   -> ncb_post     /* int (far *ncb_post)(); */
 30h    BYTE    ncb_lana_num
 31h    BYTE    ncb_cmd_cplt
 32h    DWORD   -> ncb_vname
 36h    BYTE    ncb_vnamelen
 37h  9 BYTEs   ncb_reserve
Note: fields 00h-31h are the same as for a standard NetBIOS NCB (see INT 5C)

Values for ncb_command field same as for INT 5C, except
        70h     send net Break