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

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

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


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


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.


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.