summaryrefslogtreecommitdiff
path: root/doc/rfc/rfc560.txt
diff options
context:
space:
mode:
Diffstat (limited to 'doc/rfc/rfc560.txt')
-rw-r--r--doc/rfc/rfc560.txt675
1 files changed, 675 insertions, 0 deletions
diff --git a/doc/rfc/rfc560.txt b/doc/rfc/rfc560.txt
new file mode 100644
index 0000000..6cf9f17
--- /dev/null
+++ b/doc/rfc/rfc560.txt
@@ -0,0 +1,675 @@
+
+
+
+
+
+
+Network Working Group D. Crocker
+Request for Comments: 560 J. Postel
+Category: Protocols, TELNET 20 August 1973
+NIC: 18492
+
+
+ Remote Controlled Transmission & Echoing TELNET Option
+
+ Currently, a terminal in character-at-a-time transmission and
+ foreign-host echo causes four Network Messages for each character
+ struck. (The character sent from local to foreign host; its RFNM;
+ the echoed character sent from the foreign to the local host; and its
+ RFNM.)
+
+ By eliminating most echoing (1/2 as many messages) and packaging the
+ characters into useful units (assuming an average of five character
+ per unit; therefore another 80 per cent reduction), it is believed
+ that almost a 90 per cent reduction in character-mode interactive
+ Network terminal traffic can be attained.
+
+ The packaging of characters and elimination of foreign echoing should
+ also lessen the load placed on the foreign hosts.
+
+1. Command name and code:
+
+ RCTE
+
+2. Command meanings:
+
+ IAC WILL RCTE
+
+ The sender of this command REQUESTS or AGREES to use the RCTE
+ option, and will send instructions for controlling the other
+ side's terminal printer.
+
+ IAC WON'T RCTE
+
+ The sender of this option REFUSES to send instructions for
+ controlling the other side's terminal printer.
+
+ IAC DO RCTE
+
+ The sender REQUEST or AGREES to have the other side (sender of
+ WILL RCTE) issue commands which will control his (sender of the
+ DO) output to the terminal printer.
+
+
+
+
+
+
+Crocker, et. al. [Page 1]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ IAC DON'T RCTE
+
+ The sender of this command REFUSES to allow the other side to
+ control his (sender of DON'T) terminal printer.
+
+ IAC SB RCTE <cmd> [BC1 BC2] [TC1 TC2]
+
+ where:
+
+ <cmd> is one 8-bit byte having the following flags (bits are
+ counted from the right):
+
+ Bit Meaning
+
+ 0 0 = Ignore all other bits in this byte and repeat the
+ last <cmd> that was sent. Equals a 'continue what
+ you have been doing'.
+ 1 = Perform actions as indicated by other bits in this
+ byte.
+
+ 1 0 = Print (echo) Break character
+ 1 = Skip (don't echo) Break character
+
+ 2 0 = Print (echo) text up to Break character
+ 1 = Skip (don't echo) text up to Break character
+
+ 3 0 = Continue using same classes of Break characters.
+ 1 = The two 8-bit bytes following this byte contain
+ flags for the new Break classes.
+
+ 4 0 = Continue using same classes of Transmit characters.
+ 1 = Reset Transmit classes according to the two bytes
+ following 1) the Break classes bytes, if the Break
+ classes are also being reset, or 2) this byte, if
+ the Break classes are NOT also being reset.
+
+ Value (decimal) of the <cmd> byte and its meaning:
+
+ 0 = Continue what you have been doing
+
+ 1 = Print (echo) up to AND INCLUDING Break character
+
+ 3 = Print up to Break character and SKIP (don't echo)
+ Break character
+
+ 5 = Skip text (don't echo) up to Break character, but
+ PRINT Break character
+
+
+
+
+Crocker, et. al. [Page 2]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ 7 = Skip up to and including Break character
+
+ Add one of the previous non-zero values to one of the
+ following values, to get the total decimal value for
+ the byte (Note that Classes may not be reset without
+ also resetting the printing action; so an odd number
+ is guaranteed):
+
+ 8 = Set Break classes (using the next two bytes [BC1
+ BC2])
+
+ 16 = Set Transmission classes (using the next two bytes
+ [TC1 TC2])
+
+ 24 = Set Break classes (using the next two bytes [BC1
+ BC2]) and the Transmission classes (using the two
+ bytes after that [TC1 TC2]).
+
+ Sub-commands (IAC SB RCTE...) are only sent by the Controlling
+ Host and, in addition to other functions, functionally replace the
+ Go-Ahead (IAC GA) Telnet Command.
+
+3. Default:
+
+ WON'T RCTE -- DON'T RCTE
+
+ Neither host asserts special control over the other host's
+ terminal printer.
+
+4. Motivation for the option:
+
+ RFC's 1, 5 and 51 discuss Network and process efficiency and
+ smoothness.
+
+ RFC 357, by John Davidson, introduces the problem of echoing delay
+ that occurs when a remote user accesses a full-duplex host, thru a
+ satellite link. In order to save the many thousands of miles of
+ transit time for each echoed character, while still permitting full
+ server responsiveness and clean terminal output, an echo control
+ similar to that used by some Time-sharing systems is suggested for
+ the entire Network.
+
+ In effect, the proposed option involves making a user host
+ carefully regulate the local terminal printer according to
+ explicit instructions from the foreign (serving) host.
+
+
+
+
+
+
+Crocker, et. al. [Page 3]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ An important additional issue is efficient Network transmission.
+ Implementation of the Davidson Echoing Scheme will eliminate almost
+ all server-to-user echoing.
+
+ The proposed option also requests using hosts to buffer a
+ terminal's input to the foreign host until it forms a useful unit
+ (with "useful unit" delimited by Break or Transmission characters
+ as described below). Therefore, fewer messages are sent on the
+ user-to-server path.
+
+ N.B.: This option is only intended for use with full-duplex hosts.
+ The Go-Ahead Telnet feature is completely adequate for HALF-duplex
+ server hosts.
+
+5. Explicit description of control mechanism:
+
+ A. Overview of Interaction
+
+ (1) Agree to use RCTE option
+ (2) User holds echo printing until instructed by server to do
+ otherwise
+ (3) Server may send output to terminal printer.
+ (4) Network output is printed up to an RCTE command
+ (5) Server sends IAC SB RCTE <cmd>
+ (6) User acts upon the command up to a Break character or until
+ receipt of output from the server host.
+ (7) Go to (2)
+
+ Note: Output from the server host may occur at any time, in which
+ case, the flow of control switches to (2) and then proceeds to
+ (3), (4), etc.
+
+ B. Explanation:
+
+ (1) 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).
+
+ (2) User host begins synchronization between the serving host and
+ itself by suspending terminal echo printing until directed to
+ do otherwise by the controlling host, thru an IAC SB RCTE
+ <cmd>.
+
+
+
+
+
+
+
+Crocker, et. al. [Page 4]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ (3) The server may send output to the terminal printer, either in
+ response to input from the user (in which case it is already
+ synchronized with the terminal input) or spontaneously. In
+ the latter case, flow of control automatically switches to (2)
+ and continues from there. Output from the server is defined
+ as completed when step (5) occurs. That is, text from the
+ Server to the terminal printer MUST end with an RCTE command.
+
+ (4) Any output from the server is printed on the terminal
+ IMMEDIATELY. Again note that the end of such output is
+ defined to be the occurrence of an IAC SB RCTE <cmd> command.
+
+ (5) 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.
+
+ a. A Transmission character is one which REQUIRES the User
+ Host to transmit all text accumulated up to and including
+ its occurrence. (For Net efficiency, User hosts are
+ DISCOURAGED from sending before the occurrence of a
+ Transmission character).
+
+ 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.)
+
+ b. A Break character has the effect of a Transmission
+ character, but also causes the User host to stop its
+ print/discard action upon the User's input text, until
+ directed to do otherwise by another IAC SB RCTE <cmd>
+ command from the Serving host. Break characters therefore
+ define printing units. "Break character" as used in this
+ document does NOT mean Telnet Break character.
+
+ 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.
+
+
+
+Crocker, et. al. [Page 5]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ If the bit is OFF, the Break classes remain unchanged.
+ When the RCTE option is initiated, CLASSES 4, 5, and 9
+ are to be in effect. That is, Format Effectors, Non-
+ format effector Control Characters and DEL, and
+ Punctuation characters are to be Break characters.
+
+ c. The list of the character classes, used to define Break and
+ Transmission classes are listed at the end of this
+ document, in the "Tables" Section.
+
+ d. 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.
+
+ 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.
+
+ e. 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.
+
+ f. 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."
+
+ This is particularly useful for the <cmd> command that
+ follows spontaneously generated output from the Serving
+ host (such as "System Going Down") which needs to signal
+ End-of-Message, but does not usually want to reset any
+ other conditions.
+
+ The server may, however, alter user action after a
+ spontaneous message, but it is possible that text will
+ be lost, or printed when it should not be, since there
+ is no guarantee that the RCTE <cmd> from the serving
+ host will be properly synchronized with the terminal
+ input.
+
+
+
+
+
+
+
+Crocker, et. al. [Page 6]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ (6) Input from the terminal is (hopefully) buffered up to the
+ occurrence of a Transmission or Break character; and the input
+ text is echoed or not echoed, up to the occurrence of a Break
+ Character. The most recent RCTE command determines the echo,
+ Transmission and Break actions.
+
+ (7) When a Break character is typed, the cycle of control is
+ complete and action re-commences at (2). Action also
+ automatically switches to (2) upon receipt of any text from
+ the Server host.
+
+ C. Notes, Comments, Etc.:
+
+ (1) 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.
+
+ (2) Servers will generally instruct Users 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 user
+ must be instructed NOT to echo ANY Break Characters.
+
+ This is generally a tolerable problem, since the server has to
+ send an RCTE command at this point, anyhow. Adding the Break
+ character to the message (so that it appears to be echoed)
+ will not cause any extra Network traffic.
+
+ (3) 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.
+
+ (4) A severe (User) site-dependent problem will be buffering
+ type-ahead input from the terminal. It is possible,
+ especially in the case of TIPS, that the input buffer will
+ overflow often. If the receiving (serving) host will permit,
+ the accumulated text should be transmitted at this point. If
+ the text cannot be transmitted and further typing by the user
+ will result in lost text, the user should be notified.
+
+
+
+
+
+
+
+
+
+Crocker, et. al. [Page 7]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ D. Sample Interaction:
+
+ "S:" is sent from serving (WILL RCTE) host to Using host.
+ "U:" is sent from Using (DO RCTE) host to Serving host.
+ "T:" is entered by the terminal user.
+ "P:" is printed on the terminal.
+
+ Text surrounded by square brackets ([]) is commentary.
+ Text surrounded by angle brackets (<>) is to be taken as a single
+ unit. E.G., carriage return is <cr>, and the decimal value 27
+ is represented <27>.
+
+ The following interaction shows a Logon to a Tenex, initiation of
+ the DED editor, insertion of some text and return to the Exec
+ level. A Telnet connection has already been opened, but the TENEX
+ prompt has not yet been issued. The hosts first discuss using the
+ RCTE option:
+
+ S: <IAC><WILL><RCTE>
+
+ U: <IAC><DO><RCTE>
+
+ S: TENEX 1.31.18, TENEX EXEC 1.50.2 <cr><lf>@
+ <IAC><SB><RCTE><11><1><24>
+
+ [Print the Herald and echo input text upto a Break character,
+ but do not echo the Break Character. Classes 4 (Format
+ Effectors), 5 (Non-format effector Controls and <DEL>), and 9
+ (<space>) act as Break Characters.]
+
+ P: TENEX 1.31.18, TENEX EXEC 1.50.2 <cr><lf>@
+
+ T: LOGIN ARPA <cr>
+
+ P: LOGIN
+
+ U: LOGIN <space>
+
+ S: <space><IAC><SB><RCTE><0>
+
+ P: <space>ARPA
+
+ U: ARPA <cr>
+
+ S: <cr><lf> (PASSWORD) : <IAC><SB><RCTE><7>
+
+ P: <cr><lf> (PASSWORD) :
+
+
+
+
+Crocker, et. al. [Page 8]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ T: WASHINGTON 1000<cr>
+
+ [The password "WASHINGTON" is not echoed. Action on "1000<cr>"
+ is withheld]
+
+ U: WASHINGTON <space>
+
+ S: <space><IAC><SB><RCTE><3>
+
+ P: <space> 1000
+
+ U: 1000<cr>
+
+ S: <cr><lf> JOB 17 ON TTY41 7-JUN-73 14:13 <cr><lf>@
+ <IAC><SB><RCTE><0>
+
+ P: <cr><lf> JOB 17 ON TTY41 7-JUN-73 14:13 <cr><lf>@
+
+ T: DED <esc><cr>
+
+ P: DED
+
+ U: DED<esc>
+
+ S: .SAV;1 <IAC><SB><RCTE><0>
+
+ P: .SAV;1
+
+ U: <cr>
+
+ S: <cr><lf><lf> Ded 3/14/73 DRO,KRK <cr><lf>:
+ <IAC><SB><RCTE><15><1><255>
+
+ [The program is started and the DED prompt ":" is sent. At the
+ command level, DED responds to every character.]
+
+ P: <cr><lf><lf> DED 3/14/73 DRP,KRK <cr><lf>:
+
+ T: IThis is a text line.<cr> This is another test line.<^Z> Q
+
+ ["I" means Insert Text. The text follows, terminated by a
+ Control-Z. The "Q" instructs DED to Quit.]
+
+ U: I
+
+
+
+
+
+
+
+Crocker, et. al. [Page 9]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ S: I<cr><lf>* <IAC><SB><RCTE><11><0><24>
+
+ [DED prompts the user, during text input, with an asterisk at
+ the beginning of every line.]
+
+ P: I<cr><lf> *This is a test line.
+
+ U: This is a test line.<cr>
+
+ S: <cr><lf>* <IAC><SB><RCTE><O>
+
+ P: <cr><lf>* This is another test line.
+
+ U: This is another test line.<^Z>
+
+ S: ^Z<cr>lf>: <IAC><SB><RCTE><15><1><255>
+
+ [The returned "^Z" is two characters, not the ASCII Control-Z.]
+
+ U: Q
+
+ [Note that the "Q" is not yet printed on the terminal, since it
+ is a Break character.]
+
+ S: Q<cr><lf>@ <IAC><SB><RCTE><11><1><24>
+
+ P: Q<cr><lf> @
+
+ And the user is returned to the Exec level.
+
+ E. Tables:
+
+ (1) <cmd> is one 8-bit byte having the following flags (bits are
+ counted from the right):
+
+ Bit Meaning
+
+ 0 0 = Ignore all other bits in this byte and repeat the last
+ <cmd> that was sent. Equals a 'continue what you have
+ been doing'.
+
+ 1 = Perform actions as indicated by other bits in this
+ byte.
+
+ 1 0 = Print (echo) Break character
+ 1 = Skip (don't echo) Break character
+
+
+
+
+
+Crocker, et. al. [Page 10]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ 2 0 = Print (echo) text up to Break character
+ 1 = Skip (don't echo) text up to Break character
+
+ 3 0 = Continue using same classes of Break characters.
+ 1 = The two 8-bit bytes following this byte contain flags
+ for the new Break classes.
+
+ 4 0 = Continue using same classes of Transmit characters
+
+ 1 = Reset Transmit classes according two the two bytes
+ following 1) the Break classes bytes, if the Break
+ classes are also being reset, or 2) this byte, if the
+ Break classes are NOT also being reset.
+
+ Byte Value (decimal) and its meaning:
+
+ 0 = Continue what you have been doing
+
+ Even numbers greater than zero (i.e., numbers with the right-
+ most bit off) are in error and should be interpreted as
+ equal to zero. When the <cmd> is an even number greater
+ than zero, Classes bytes TC1 & TC2 and/or BC1 & BC2 must
+ not be sent.
+
+ 1 = Print (echo) up to AND INCLUDING Break character
+
+ 3 = Print up to Break character and SKIP (don't echo) Break
+ character
+
+ 5 = Skip text (don't echo) up to Break character, but PRINT
+ Break character
+
+ 7 = Skip up to and including Break character
+
+ Add one of the previous non-zero values to one of the following
+ values, to get the total decimal value for the byte (Note
+ that Classes may not be reset, without also resetting the
+ printing action; so an odd number is guaranteed):
+
+ 8 = Set Break classes (using the next two bytes [BC1 BC2])
+
+ 16 = Set Transmission classes (using the next two bytes [TC1
+ TC2])
+
+ 24 = Set Break classes (using the next two bytes [BC1 BC2]) and
+ the Transmission classes (using the two bytes after that
+ [TC1 TC2]).
+
+
+
+
+Crocker, et. al. [Page 11]
+
+RFC 560 RCT & Echoing TELNET Option August 1973
+
+
+ (2) Classes for Break and Transmission (The right-most bit of the
+ second byte (TC2 or BC2) represents Class 1; the left-most bit
+ of the first byte (TC1 or BC1) represents the currently
+ undefined Class 16):
+
+ 1: Upper-Case Letter (A-Z)
+
+ 2: Lower-case letters (a-z)
+
+ 3: Numbers (0-9)
+
+ 4: Format Effectors (<BS> <CR> <LF> <FF> <HT> <VT>)
+
+ 5: Non-format effectors Control Characters, <DEL> and <ESC>
+
+ 6: . , ; : ? !
+
+ 7; - [ ( < > ) ] |
+
+ 8: ' " / \ % @ $ # + - * = ^ <- _ (square box symbol)
+
+ 9: <space>
+
+ And Telnet commands (IAC...) are ALWAYS to have the effect of
+ a Break character.
+
+
+ [ This RFC was put into machine readable form for entry ]
+ [ into the online RFC archives by Via Genie ]
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Crocker, et. al. [Page 12]
+