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