Discussion on RCTE

Network Working Group                                     Jon Postel  (SRI-ARC)
Request for Comments: 719                                                Jul 76
NIC #36138




                          Discussion on RCTE

The following is the significant portion of a dialog on RCTE that has
followed the publication of RFC 718.

15-Jul-76 Nancy Mimno (BBN-NET)

   Jon,
   I've read RFC718 and have got some comments, in particular with
   respect to the "third problem" or clearing the input buffer part.

   1) I believe the stated implementation is backwards: in the normal
   case of the RCTE mode negotiation, the server sends "WILL RCTE" and
   the user sends ,"DO RCTE"; the reverse case is thus the server sending
   "DO RCTE" and the user "WILL RCTE" Also, it is probably wise to say
   explicitly that the server's sending "DO RCTE" requires the user
   process to respond "WILL (or WON'T) RCTE" and that this response is
   the synchronizing mark.

   2) The problem is a real one and I think the RCTE protocol would be
   better with a "clear input, reset counters" function.  The question is
   Ill now to do it.  In talking with Rav yesterday, I learned that he had
   this in mind as a general function, not restricted to RCTE; in fact,
   TENEX sends the "reverse RCTE" option for "clear your input buffer"
   whether or not the connection is in RCTE mode.  In this case, the
   statement about "cannot be confused with the normal use of the RCTE
   option" will not always be true.  I think we both agreed that the
   current solution should just be an interim one.

   3) I suggest a different way of performing this function, using the
   synch-datamark sequence.  First, the RCTE option would have to
   explicitly require that this function reset the counters and cause a
   "clear your input buffer (of data)", all synchronized with the
   datamark of course.  This is pretty much what it is now except for
   the reset counters; receiving Synch-data mark when in RCTE probably
   needed defining anyhow.  Because RCTE won't work unless both sides
   agree, the "clear input and reset counters" meaning for
   synch-data mark would have to be a mandatory part of the RCTE option.
   Second, since the Synch-data mark is a "one-way" function, there needs
   to be a way for one side of the connection to tell the other side to
   "send me a Synch-data mark".  The New Telnet protocol spec implied that
   Abort Output could be used for that purpose; if hot, then perhaps a
   new function could be defined.  Again, the RCTE option should make
   some explicit statement requiring (or very strongLy recommending)
   this interpretation of AO.  For non-RCTE mode, it's a nice idea but
   probably not required.  Ray has tentatively agreed- thinks it could
   work on Tenex (server side).   I would like your comments and Doug
   Dodds' (Tenex user RCTE).  I don't know of any other existing RCTE
   implementations that would have to change.  I also don't know what it

                                     -1-

   takes to extend official protocols these days, but maybe it's easier
   to do that than define a new option (ie reverse RCTE).

   Regards,
   Nancy



15-Jul-76 Doug Dodds (BBN-RCC)

   Nancy,

   Your suggestion for the RCTE-clear function being performed by the Au
   command (when RCTE is on) is a good one.  I see no problem with it
   from the side of the Tenex User Telnet (NTELNET).  At present NTELNET
   is ignoring AO (and some other commands) entirely; this is a good
   opportunity to implement it in general.

   Doug




21-Jul-76 Jon Postel (SRI-ARC)

   I met with Ray Tomlinson for a few minutes to discuss the RCTE-clear
   function and other RCTE features.  We agreed that Nancy's suggestion
   for using the AO command for the clear function made sense.  We also
   determined that the RCTE document should say something about the
   state some other options should be in when using RCTE.  For example we
   believe that GO-AHEAD must be suppressed while RCTE is in use, that
   when one quits RCTE the ECHO mode must be restored to what it was at
   the time of entering RCTE,, and that BINARY and RCTE do not make sense
   as a combination because every byte would have to be assumed to be a
   break character.  We also determined that it is unworkable to use
   RCTE and no break characters since there is no way to get out of that
   state.

22-Jul-76 Jon Postel (SRI-ARC)

   As a result of the above discussion I will prepare a revised RCTE
   specification document.  A draft will be distributed to interested
   parties for comments and the final document will be published as an
   RFC.










                                     -2-