Microtronix Access User Guide
11.7 LINE
No regard is paid to message boundaries on data passed from the X.25 to TCP direction. Data is
forwarded when and as received (RAW byte stream).
Data from the TCP to X.25 direction is buffered until a carriage return (CR), linefeed (LF), or EOT
character is received, and then forwarded in a single packet sequence. In addition, any LF characters
that may have been inserted after a CR will be stripped, otherwise converted to CR.
This method is useful when replacing an X.25 PAD with a TCP terminal emulator to connect to a
command line interface of an X.25 host.
11.8 IAC-ESC
This setting helps ensure data transparency when connecting with a remote Telnet client/server. Data
from the TCP socket is scanned for Telnet commands which are stripped and ignored. Escaped IAC
characters have the escape removed. Data from the terminal is scanned for IAC characters, and an
IAC escape is inserted. This ensures binary data integrity in the data stream.
11.9 RBP
This method guarantees message boundaries in much the same way as the MBIT method described
above. The message header differs in length and value, and application messages may span multiple
RBP messages by use the the M-bit (0x01) in the RBP flag byte. The RBP header consists of 6 bytes
consisting of 2 fixed-value bytes (version) followed by the length of the payload, and a flag byte.
RBP message format:
Version
Payload length
Flag
Payload
0xD7
0x4A
MSB
LSB
0x00/1
0x00
Application message
11.10 QRBP
Identical to RBP as described above, but also preserves any X.25 Q-bits by use of the 0x02 bit in the
RBP flag byte. Q-bit packets are used by some X.25 applications for passing control information.
RBP message format:
Version
Payload length
Flag
Payload
0xD7
0x4A
MSB
LSB
0x00/1/2
0x00
Application message
11.11 AEPN
This method guarantees application message boundaries and any X.25 Q-bit messages. The
application messages may span multiple AEPN messages by use the the M-bit (0x80) in the flag byte,
and any X.25 Q-bit is preserved with the Q-bit (0x40) in the flag byte. The message header consists of
8 bytes where the application message or fragment length (payload length) is given in big endian
format (MSB, LSB).
AEPN message format:
80
