rfc726.txt

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         2) If the terminal input buffer is empty, then go to 3,
         else go to 4.                                               6a3

         3) Wait for an item to appear either from the terminal
         or from the network.                                        6a4

           If an item appears from the terminal, then go to 4.      6a4a

           If a data item appears from the network, then print
           it and go to 3.                                          6a4b

           If a command appears from the network, then an error
           has occured.                                             6a4c

         4) Read an item from the terminal input buffer.             6a5

           If the item is not a break, then print/skip it and go
           to 2.                                                    6a5a

           If the item is a break, then print/skip it and go to
           1.                                                       6a5b

         Note:  Output from the server host may occur at any
         time, such "spontaneous output" is printed in step 3.       6a6













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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



       Explanation:                                                   6b

         Both Hosts agree to use the RCTE option. After that,
         the using host (IAC DO RCTE) merely acts upon the
         controlling (serving) host's commands and does not
         issue any RCTE commands unless and until it (using
         host) decides to stop allowing use of the option (by
         sending IAC DON'T RCTE).                                    6b1

         1)  The using host is synchronized with the server by
         initially and when ever it returns to step 1 suspending
         terminal echo printing until it receives a command from
         the server.                                                 6b2

         The server may send either output to the terminal
         printer or a command, and usually sends a both.             6b3

         The server may send output to the terminal printer
         either in response to user input or spontaneously. In
         the former case, the output is processed in step 1. In
         the latter case, the output is processed in step 3.         6b4

         Server sends an RCTE command. The command may redefine
         break and transmission classes, action to be performed
         on break characters, and action to be performed on
         text. Each of these independent functions is controlled
         by separate bits in the <cmd> byte.                         6b5

           A transmission character is one which RECOMMENDS that
           the using host transmit all text accumulated up to
           and including its occurrence. (For network
           efficiency, using hosts are DISCOURAGED (but not
           prohibited) from sending before the occurrence of a
           transmission character, as defined at the moment the
           character is typed).                                     6b5a

             If the transmission classes bit (bit 4) is on, the
             two bytes following the two break classes bytes (or
             immediately following the <cmd> byte, if the break
             classes bit is not on) will indicate what classes
             are to be enabled.

             If the bit is OFF, the transmission classes remain
             unchanged. When the RCTE option is first initiated,
             NO CLASSES are in effect. That is, no character
             will be considered a transmission character. (As if
             both TC1 and TC2 are zero.)

           A break character REQUIRES that the using host



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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



           transmit all text accumulated up to and including its
           occurrence and also causes the using host to stop its
           print/discard action upon the user's input text,
           until directed to do otherwise by another IAC SB RCTE
           <cmd> IAC SE command from the serving host. Break
           characters therefore define printing units. "Break
           character" as used in this document does NOT mean
           Telnet Break character.                                  6b5b

             If the break classes bit (bit 3) is on, the two
             bytes following <cmd> will indicate what classes
             are to be enabled. There are currently nine (9)
             classes defined, with room for expansion.

             If the bit is OFF, the break classes remain
             unchanged. When the RCTE option is initiated, NO
             CLASSES are to be in effect. That is, no
             transmission will take place in the user to server
             direction until the first break reset command is
             received by the user from the server.

           The list of character classes, used to define break
           and transmission classes are listed at the end of
           this document, in the Tables Section.                    6b5c

           Because break characters are special, the
           print/discard action that should be performed upon
           them is not always the same as should be performed
           upon the rest of the input text.                         6b5d

             For example, while typing a filename to TENEX, I
             want the text of the filename to be printed
             (echoed); but I do not want the <escape> (if I use
             the name completion feature) to be printed.

             If bit 1 is ON the break character is NOT to be
             printed.

           A separate bit (bit 2) signals whether or not the
           text itself should be printed (echoed) to the
           terminal. If bit 2 = 0, then the text IS to be
           printed.                                                 6b5e

           Yet another bit (bit 0 - right-most bit) signals
           whether or not any of the other bits of the command
           should be checked. If this bit is OFF, then the
           command should be interpreted to mean "continue
           whatever echoing strategy you have been following,
           using the same break and transmission classes."          6b5f



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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



         2)  The user Telnet now checks the terminal input
         buffer, if it contains data it is processed in step 4,
         otherwise the user Telnet waits in step 3 for further
         developments.                                               6b6

         3)  The user Telnet waits until either the human user
         enters some data in which case Telnet proceeeds to step
         4, or an item is received from the network. If the item
         from the network is data it is spontaneous output and
         is printed, Telnet then continues to wait. If the item
         from the network is a command then an error has
         occured. In this case the user Telnet may attempt to
         resynchronize the use of RCTE as indicated below.           6b7

         4)  Items from the terminal are processed with printing
         controlled by the settings of the latest break reset
         command. When a break character is processed, the cycle
         of control is complete and action re-commences at step
         1.                                                          6b8

         Input from the terminal is (hopefully) buffered into
         units ending with a transmission or break character;
         and echoing of input text is suspended after the
         occurrence of a break character and until receipt of a
         break reset command from the serving host. The most
         recent break reset command determines the break
         actions.                                                    6b9

         In summary, what is required is that for every break
         character sent in the user to server direction there be
         a break reset command sent in the server to user
         direction. The user host initially has no knowledge of
         which characters are break characters and so starts in
         a state that assumes that there are no break characters
         and also that no echoing is to be provided. The server
         host is expected to send a break reset command to
         establish the break classes and the echoing mode before
         it receives any data from the user.                        6b10

       Synchronization and Resynchronization:                         6c

         The serving and using hosts must carefully synchronize
         break reset commands with the transmission of break
         characters. Except at the beginning of an interaction,
         the serving host may only send a break reset command in
         response to the Using host's having sent a break
         character as defined at that time. This should
         establish a one-to-one correspondence between them.  (A
         <cmd> value of zero, in this context, is interpreted as



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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



         a break classes reset to the same class(es) as before.)
         The break reset command may be preceded by terminal
         output.                                                     6c1

         The re-synchronization of the break characters and the
         break reset commands is done via the exchange of the
         Telnet signal Abort Output (AO) in the server to user
         direction and the SYNCH in the user to server
         direction.                                                  6c2

         Suppose the server wants to resynchronize the break
         characters and the break reset commands.                    6c3

           a.  The server should be sure all output to the
           terminal has been printed by using, for example, the
           Timing Mark Option.                                      6c3a

           b.  The server sends the AO signal.                      6c3b

           c.  The user receives the AO signal. The user flushes
           all user to server data wheather it has been echoed
           or not. The user sends a SYNCH to the server. [The
           SYNCH consists of the Telnet Data Mark (DM) and the
           host-to-host interrupt (INS).] The user now enters
           the initial state at step 1.                             6c3c

           d.  The server receives the SYNCH and flushes any
           data preceeding the DM (as always). The server now
           sends a break reset command. (Actually the break
           reset command could be sent at any time following the
           AO.)                                                     6c3d

         Suppose the user wants to resynchronize the break
         characters and the break reset commands.                    6c4

           a.  The user should discard all user to server data
           wheather it has been echoed or not.                      6c4a

           b.  The user sends the AO signal. The user now enters
           the algorithm at step 1.                                 6c4b

           c.  The server receives the AO signal. The server
           discards all data buffered but not yet sent to the
           user. The server sends a SYNCH to the user. The
           server sends a break reset command to the user.          6c4c







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     NWG/RFC# 726                          JBP DHC 8-MAR-77 08:29  39237
     Remote Controlled Transmission & Echoing Telnet Option



       Notes and Comments:                                            6d

         Even-numbered commands, greater than zero, are in
         error, since they will have the low-order bit off. The
         command should be interpreted as equal to zero, which
         means that any classes reset bytes ([TC1 TC2] [BC1
         BC2]) will be in error. (The IAC SE, at the end of the
         command, eliminates any parsing problems due to this
         error.)                                                     6d1

         Serving hosts will generally instruct using hosts not
         to echo break characters, even though it might be
         alright to echo most break characters. For example,
         <cr> is usually a safe character to echo but <esc> is
         not. TENEX Exec is willing to accept either, during
         filename specification. Therefore, the using host must
         be instructed not to echo any break characters.             6d2

           This is generally a tolerable problem, since the
           serving host has to send an RCTE command at this
           point, anyhow. Adding an echo for the break character
           to the message will not cause any extra network
           traffic.                                                 6d2a

         The RCTE Option entails a rather large overhead. In a
         true character-at-a-time situation, this overhead is
         not justified. But on the average, it should result in
         significant savings, both in network traffic and host
         wake-ups.                                                   6d3

         Buffering Problems and Transmission vs. Printing
         Constraints:                                                6d4

           There are NO mandatory transmission constraints. The