RFC 596 (rfc596) - Page 1 of 5


Second thoughts on Telnet Go-Ahead



Alternative Format: Original Text Document



Network Working Group                                            E. Taft
Request for Comments: 596                                      PARC-MAXC
NIC: 15372                                               8 December 1973


                   Second Thoughts on Telnet Go-Ahead

INTRODUCTION

   In this RFC we present objections to the requirement that hosts
   implement the Telnet Go-Ahead (GA) command, as specified in the
   Telnet Protocol Specification (NIC #15372).  The thrust of these
   objections is in three major directions:

      1. The GA mechanism is esthetically unappealing, both to myself
      and to many other people I have talked to.  I shall attempt to
      describe why this is so.

      2. As specified in the Protocol, GA will not, in general, work;
      i.e. it will not serve its intended purpose unless hosts make
      various unwarranted assumptions about how other hosts operate.

      3. GA is impossible for most hosts to implement correctly in all
      cases.  This is certainly true of the PDP-10 operating systems
      with which I am familiar (10/50 and Tenex).

   The purpose of this RFC is to advocate either complete removal of the
   GA mechanism or relegating it to the status of a negotiated option
   whose default state is that it be suppressed.

TERMINOLOGY

   "Half-duplex" is a two-way communication discipline in which
   transmission takes place in only one direction at a time and the
   receiving party is constrained not to transmit until the transmitting
   party has explicitly given up control of the communication path
   ("turned the line around").

   This definition is distinct from a common (but incorrect) use of the
   terms "half-duplex" and "full-duplex" to designate local and remote
   character echoing.

   "Reverse break" is a means by which a computer connected to a
   terminal by a half-duplex path may regain control of the path for
   further typeout after previously having relinquished it.






Taft