Movatterモバイル変換

Network Working Group                                         D. CrockerRequest for Comments: 581                                       UCLE-NMCNIC: 19860                                                     J. PostelReferences:RFC 560,RFC 563                                   MITRE-TIPCategories: Protocols, TELNET, RCTE                        November 1973Corrections toRFC 560Remote Controlled Transmission & Echoing TELNET Option                                                                   1a   [This RFC contains corrections toRFC 560 (NIC -- 18492,) which   described the Remote Controlled Transmission and Echoing TELNET   Option.  A completely updated version of 18492 has been journalized   and will be included in the Protocols Notebook.  These new   specifications for RCTE are in NIC document (19859,).]          2Section 1 of the RCTE Option specification (18492,2a:gy) was supposed   to include the name and code for the option.  The code was   accidentally left out.  That statement should read:                                                                   3      RCTE  7                                                      3aSection 2 should include the End of Subnegotiation Parameter, at the   end of the subnegotiation parameter specification (18492,2b5:gy).   All examples in the option specifications, showing RCTE SB commands,   should also show the IAC SE parameter. (The revised RCTE   specifications have been so changed.)Section 2 should be changed so   that it reads:                                                  4      IAC SB RCTE <cmd> [BC1 BC2] [TC1 TC2] IAC SE                 4a   The sample scenario, inSection 5.D (18492,2e4:gy), should be   modified to reflect the kind of asynchrony of events that can occur   with the RCTE protocol.  The updated RCTE specifications (in --   19859,1e4:gy) now reflects this.                                5   InRFC 563 (18755,) John Davidson criticizes RCTE's apparent failure   to allow Net I/O and server computation to overlap.             6   I agree with John's criticisms and feel that the following should fix   the problem:                                                    7Crocker & Postel                                                [Page 1]

RFC 581         Remote Controlled Transmission & Echoing   November 1973   1. Change 5.A (18492,2e1)                                       7a      from:                                                        7a1         Overview of Interaction                                   7a1a      to:                                                          7a2         Overview of User Terminal Printing Action & Control       7a2a   2. Change 5.B.5.a (18492,2e2e1)                                 7b      from:                                                        7b1         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).                                               7b1a      to:                                                          7b2         A Transmission character is one which RECOMMENDS that the Using         Host transmit all text accumulated up to and including its         occurrence. (For Net efficiency, Using hosts are DISCOURAGED         from sending before the occurrence of a Transmission character,         as defined at the moment the character is typed).         7b2a   3. Change 5.B.5.b (18492,2e2e2)                                 7c      from:                                                        7c1         A Break character has the effect of a Transmission character,         but 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.            7c1a      to:                                                          7c2         A Break character REQUIRES that the Using host 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.  BreakCrocker & Postel                                                [Page 2]

RFC 581         Remote Controlled Transmission & Echoing   November 1973         characters therefore define printing units.  "Break character"         as used in this document does NOT mean Telnet Break character.         7c2a   4. Change 5.B.6 (18492,2e2f)                                    7d      from:                                                        7d1         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.                 7d1a      to:                                                          7d2         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 RCTE Break reset command         determines the Break actions.                             7d2a   5. Change 5.C.4 (18492,2e3d)                                    7e      FROM:                                                        7e1         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.    7e1a      to:                                                          7e2         Buffering Problems and Transmission vs. Printing Constraints:         7e2a            There are NO mandatory transmission constraints.  The Using            host is allowed to send a character a time, though this            would be a waste of RCTE.  The Transmission Classes commands            are GUIDELINES, so deviating from them, as when the User's            buffer gets full, is allowed.               7e2a1Crocker & Postel                                                [Page 3]

RFC 581         Remote Controlled Transmission & Echoing   November 1973            Additionally, the Using host may send a Break Class            character, without knowing that it is one (as with type-            ahead).                                           7e2a2            The problem with buffering occurs when printing on the            user's terminal must be suspended, after the user has typed            a currently valid Break Character and until a Break Reset            command is received from the serving host.  During this            time, the user may be typing merrily along.  The text being            typed may be SENT, but may not yet be PRINTED.   7e2a3            The more standard problem of filling the transmission            buffer, while awaiting an ALLOC from the Serving host, may            also occur, but this problem is well known to implementors            and in no way special to RCTE.            7e2a4            In any case, when the buffer does fill and further text            typed by the user will be lost, the user should be notified.            7e2a5   6. And add 5.C.5, 5.C.6, 5.C.7, 5.C.8, and 5.C.9 as follows:    7f      (5) The Serving and Using hosts must carefully synchronize Break          Class 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 User 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 a Break Classes reset to the same class(es) as          before.) The Reset command may be preceded by terminal output.          7f1      (6) Text should be buffered by the User host until the user types          a character which belongs to the transmission class in force          at THE MOMENT THE CHARACTER IS TYPED.            7f2      (7) Transmission Class Reset commands may be sent by the Serving          host at ANY TIME.  If they are frequently sent separate from          Break Class Reset commands, it will probably be better to exit          from RCTE and enter regular character at a time transmission.          7f3      8) It is not immediately clear what the Using host should do with          currently buffered text, when a Transmission Classes Reset          command is received.  The buffering is according to the          previous Transmission Classes scheme.                 7f4Crocker & Postel                                                [Page 4]

RFC 581         Remote Controlled Transmission & Echoing   November 1973          The Using host clearly should NOT simply wait until a          Transmission character (according to the new scheme) is typed.          7f4a          Either the buffered text should be rescanned, under the new          scheme;                                                   7f4b          Or the buffered text should simply be sent as a group.  This          is the simpler approach, and probably quite adequate.     7f4c      9) It is possible to define NO BREAK CHARACTERS except TELNET          commands (IAC ...).  This might actually be useful, as in the          case of transmitting on carriage-return, with the Using host          echoing (a controlled half-duplex).                  7f5          Having the using host send a Telnet Command will allow the          serving host to know when he may reset the Break classes, but          the mechanism is awkward and probably should be avoided.          b 7e2Crocker & Postel                                                [Page 5]