rfc1184.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

Network Working Group                               Telnet Working Group
Request for Comments: 1184                             D. Borman, Editor
Obsoletes: RFC 1116                                  Cray Research, Inc.
                                                            October 1990


                         Telnet Linemode Option

Status of this Memo

   This memo describes a Draft Standard for the Internet community, and
   requests discussion and suggestions for improvements.  This RFC
   specifies an IAB standards track protocol for the Internet community.
   Please refer to the current edition of the "IAB Official Protocol
   Standards" for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

Changes from RFC1116:

      Two new mode bits have been added, SOFT_TAB and LIT_ECHO.  These
      bits allow the server to give the client some advise on how to
      echo tabs and non-printable characters.

      Several new special character mappings have been added for cursor
      motion when visual editing is supported.  These are: Move cursor
      one character left/right (SLC_MCL/SLC_MCR), move cursor one word
      left/right (SLC_MCWL/SLC_MCWR), move cursor to begining/end of
      line (SLC_MCBOL/SLC_MCEOL), enter insert/overstrike mode
      (SLC_INSRT/SLC_OVER), erase one character/word to the right
      (SLC_ECR/SLC_EWR), and erase to the beginning/end of the line
      (SLC_EBOL/SLC_EEOL).

Overview

   Linemode Telnet is a way of doing terminal character processing on
   the client side of a Telnet connection.  While in Linemode with
   editing enabled for the local side, network traffic is reduced to a
   couple of packets per command line, rather than a couple of packets
   per character typed. This is very useful for long delay networks,
   because the user has local response time while typing the command
   line, and only incurs the network delays after the command is typed.
   It is also useful to reduce costs on networks that charge on a per
   packet basis.  Please send comments to the [e-mail]
   mailing list.







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RFC 1184                 Telnet Linemode Option             October 1990


Table of Contents

   1.   Command Names and Codes                                        2
   2.   Command Meanings                                               3
   2.1  The LINEMODE function                                          3
   2.2  LINEMODE suboption MODE                                        4
   2.3  LINEMODE suboption FORWARDMASK                                 5
   2.4  LINEMODE suboption SLC, Set Local Characters                   6
   2.5  New control characters                                        10
   3.   Default Specification                                         11
   4.   Motivation                                                    11
   5.   Implementation Rules                                          13
   5.1  User Interface                                                13
   5.2  End of line terminators                                       14
   5.3  Output processing                                             14
   5.4  A terminal driver in Telnet?                                  14
   5.5  Setting of Local Characters                                   14
   5.6  FORWARDMASK and SLC_FORW1 and SLC_FORW2                       15
   5.7  Valid and invalid modes and values                            16
   5.8  Flushing input and output                                     16
   5.9  State diagram for SLC                                         18
   5.10 Example of a connection                                       19
   6.   Other Telnet options and RFCs                                 22
   7.   Security Considerations                                       23
   8.   Author's Address                                              23

1.  Command Names and Codes

       LINEMODE        34
           MODE             1
               EDIT             1
               TRAPSIG          2
               MODE_ACK         4
               SOFT_TAB         8
               LIT_ECHO        16
           FORWARDMASK      2
           SLC              3
               SLC_SYNCH        1
               SLC_BRK          2
               SLC_IP           3
               SLC_AO           4
               SLC_AYT          5
               SLC_EOR          6
               SLC_ABORT        7
               SLC_EOF          8
               SLC_SUSP         9
               SLC_EC          10
               SLC_EL          11



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RFC 1184                 Telnet Linemode Option             October 1990


               SLC_EW          12
               SLC_RP          13
               SLC_LNEXT       14
               SLC_XON         15
               SLC_XOFF        16
               SLC_FORW1       17
               SLC_FORW2       18
               SLC_MCL         19
               SLC_MCR         20
               SLC_MCWL        21
               SLC_MCWR        22
               SLC_MCBOL       23
               SLC_MCEOL       24
               SLC_INSRT       25
               SLC_OVER        26
               SLC_ECR         27
               SLC_EWR         28
               SLC_EBOL        29
               SLC_EEOL        30

               SLC_DEFAULT      3
               SLC_VALUE        2
               SLC_CANTCHANGE   1
               SLC_NOSUPPORT    0
               SLC_LEVELBITS    3

               SLC_ACK        128
               SLC_FLUSHIN     64
               SLC_FLUSHOUT    32
       EOF            236
       SUSP           237
       ABORT          238

2.  Command Meanings

2.1 The LINEMODE function

   IAC WILL LINEMODE

      The sender of this command REQUESTS permission to begin sub-
      negotiation of the editing/signaling status.  This should only be
      sent by the client side of the connection.

   IAC WONT LINEMODE

      The sender of this command DEMANDS that sub-negotiation of the
      editing/signaling status not be allowed.




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RFC 1184                 Telnet Linemode Option             October 1990


   IAC DO LINEMODE

      The sender of this command REQUESTS that the remote side begin
      sub-negotiation of the editing/signaling status.  This should only
      be sent by the server side of the connection.

   IAC DONT LINEMODE

      The sender of this command DEMANDS that the remote side not begin
      sub-negotiation of the editing/signaling status.

2.2 LINEMODE suboption MODE

   IAC SB LINEMODE MODE mask IAC SE

      The sender of this command CONFIRMS, or REQUESTS permission for, a
      switch to the mode defined by "mask".

   The "mask" is a bit mask of various modes that the connection can be
   in.  Under normal operation, the server side of the connection will
   initiate mode changes, and the client will confirm the mode changes.
   The currently defined modes are:

      EDIT     When set, the client side of the connection should
               process all input lines, performing any editing functions,
               and only send completed lines to the remote side.  When
               unset, client side should not process any input from the
               user, and the server side should take care of all
               character processing that needs to be done.

      TRAPSIG  When set, the client side should translate appropriate
               interrupts/signals to their Telnet equivalent.  (These
               would be IP, BRK, AYT, ABORT, EOF, and SUSP) When unset,
               the client should pass interrupts/signals as their normal
               ASCII values.

      FLOW     Logically, this belongs in the "mask".  However, this
               would overlap the Telnet TOGGLE-FLOW-CONTROL option, so
               the Telnet TOGGLE-FLOW-CONTROL option is used instead.
               When DO/WILL LINEMODE is negotiated, DO/WILL TOGGLE-
               FLOW-CONTROL should also be negotiated.  See RFC 1080,
               "Telnet Remote Flow Control", for correct usage.

      ECHO     Logically, this belongs in the "mask".  However, this
               would overlap the Telnet ECHO option, so the Telnet ECHO
               option is used instead.  The client side should never
               negotiate "WILL ECHO".  When the server has negotiated
               "WILL ECHO", the client should not echo data typed by the



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RFC 1184                 Telnet Linemode Option             October 1990


               user back to the user.  When the server has negotiated
               "WONT ECHO", the the client is responsible for echoing
               data typed by the user back to the user.  See RFC 857,
               "Telnet ECHO OPTION" for a complete discussion on the use
               of the Telnet ECHO option.

      SOFT_TAB When set, the client side should expand the Horizontal
               Tab (HT) code, USASCII 9, into the appropriate number of
               spaces to move the printer to the next horizontal tab
               stop.  When unset, the client side should allow the
               Horizontal Tab code to pass through un-modified.

      LIT_ECHO When set, if the client side is echoing a non-printable
               character that the user has typed to the users screen,
               the character should be echoed as the literal character.
               If the LIT_ECHO bit is not set, then the client side may
               echo the character in any manner that it desires.  (Many
               systems echo unprintable characters as two character
               sequences, for example, they will echo "^A" for an
               ASCII 1 value.)

   When the client side of a connection receives a MODE command, it MUST
   agree with at least the state of the EDIT and TRAPSIG bits.  If a
   MODE command is received with a mode mask that is currently in use
   (ignoring the MODE_ACK bit), the MODE command is ignored.  If a MODE
   command is received that is different from the current mode mask,
   then a reply is sent with either the new mode mask and the MODE_ACK
   bit set, or a subset of the new mode mask.  The only exception is
   that if the server receives a MODE with either the EDIT or TRAPSIG
   bits not set, it may set the EDIT and TRAPSIG bits in the response,
   and if the client receives a MODE with the EDIT or TRAPSIG bits set,
   it may not clear them in the response.

   When a MODE command is received with the MODE_ACK bit set, and the
   mode is different that what the current mode is, the client will
   ignore the new mode, and the server will switch to the new mode.
   This ensures that both sides of the connection will resolve to the
   same mode.  In all cases, a response is never generated to a MODE
   command that has the MODE_ACK bit set.

2.3 LINEMODE suboption FORWARDMASK

   IAC SB LINEMODE DO FORWARDMASK mask0 mask1 ... mask31 IAC SE

      The sender of this command request that the other side send any
      buffered data when any of the ASCII characters defined by the bit
      mask are received.  Only the side of the connection that sent DO
      LINEMODE (the server side) may negotiate this.  The mask is up to



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RFC 1184                 Telnet Linemode Option             October 1990


      32 octets long.  Each octet represents 8 ASCII character codes.
      The high order bit of mask0 corresponds to an ASCII code of 0.
      The low order bit of mask0 corresponds to an ASCII code of 7.  The
      high order bit of mask1 corresponds to an ASCII code of 8.  The
      low order bit of mask1 corresponds to an ASCII code of 15, and so
      on. The mask list may be terminated before the end of the list, in
      which case all the rest of the mask octets are assumed to be reset
      (equal to zero).  When the server side is in DONT TRANSMIT-BINARY
      mode, then only the first 16 octets of the mask (ASCII codes 0
      through 127) are used.  If any individual octet of the mask is
      equal to IAC, it must be sent as a double IAC.

   IAC SB LINEMODE DONT FORWARDMASK IAC SE

      The sender of this command requests that the other side stop using
      the forward mask to determine when to send buffered data.

   IAC SB LINEMODE WILL FORWARDMASK IAC SE

      This command is sent in response to a DO FORWARDMASK command.  It
      indicates that the forward mask will be used to determine when to
      send buffered data.

   IAC SB LINEMODE WONT FORWARDMASK IAC SE

      This command is sent in response to a DO FORWARDMASK command.  It
      indicates that the forward mask will not be used to determine when
      to send buffered data.

2.4 LINEMODE suboption SLC, Set Local Characters

   The SLC suboption uses a list of octet triplets. The first octet
   specifies the function, the second octet specifies modifiers to the
   function, and the third octet specifies the ASCII character for the
   function.

   IAC SB LINEMODE SLC <list of octet triplets> IAC SE