RFC 435 (rfc435) - Page 1 of 10

Telnet issues

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Network Working Group                                          B. Cosell
Request for Comment: 435                                         BBN-NET
NIC: 13675                                                     D. Walden
Category: TELNET, Protocols, Echoing                             BBN-NET
References: 318, 357                                      5 January 1973


                             TELNET Issues

   This RFC discusses a number of TELNET related issues which have been
   bothering us [1].  The basic, central issue we started from was that
   of echoing.  We worked downward from our difficulties to discover the
   basic principles at the root of our unhappiness, and from there
   worked back upwards to design a scheme which we believe to be better.
   In this note we will discuss both the alternate scheme and its
   underlying principles.

   As something of a non sequitur, before discussing echoing we feel it
   expedient to dismiss one possible stumbling block, outright.  HIDE
   YOUR INPUT may or may not be a good idea, this question not
   concerning us at the moment.  Whatever the case, the issue of hiding
   input is certainly separable from that of echoing.  We, therefore,
   strongly recommend that a STOP HIDING YOUR INPUT command be
   sanctioned to replace the multiplexing of this function on the NO
   ECHO command.  Once this has been done, the pair of commands HIDE
   YOUR INPUT and STOP HIDING YOUR INPUT can be kept or discarded
   together, and we can discuss the issue of echoing independently of
   them.

Echoing

   The basic observation that we made regarding echoing was that servers
   seem to be optimized to best handle terminals which either do their
   own echoing or do not, but not both.  Therefore, the present TELNET
   echoing conventions, which prohibit the server from initiating a
   change in echo mode, seemed overly confining.  The servers are
   burdened with users who are in the 'wrong' mode, in which they might
   not otherwise have to be, and users, both human and machine, are
   burdened with remembering the proper echoing mode, and explicitly
   setting it up, for all the different servers.  It is our
   understanding that this prohibition was imposed on the servers to
   prevent loops from developing because of races which can arise when
   the server and user both try to set up an echo mode simultaneously.
   We will describe a method wherein both parties can initiate a change
   of echo mode and show that the method does not loop.






Cosell & Walden
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