RFC 595 (rfc595) - Page 1 of 5

Second thoughts in defense of the Telnet Go-Ahead

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Network Working Group                                      Wayne Hathaway
Request for Comments # 595                                        AMES-67
NIC # 20617                                                   12 Dec 1973
References: NIC # 20812


            Some Thoughts in Defense of the TELNET Go-Ahead

This note is a reply to Edward Taft's "Second Thoughts on TELNET Go-
Ahead" (NIC #20812).  Specifically, I will attempt to show the
following about the three main directions of his objections:

     1. It is the idea of line-at-a-time systems which are esthetically
     unappealing, not the GA mechanism.  This may be a valid point, but
     given the large number of such systems on the net, it would seem a
     rather academic one.

     2. The specified GA mechanism will in fact work very well between
     (reasonably implemented) line-at-a-time systems, and should provide
     significant help elsewhere.

     3. While the GA mechanism may not be correct in all cases, it can
     provide significant advantages fro the line-at-a-time systems and
     users.

   My comments will be arranged under the original headings from the
   subject RFC (NIC #20812).

"TECHNOLOGY"

   The definitions of "half-duplex" and "reverse break" are
   satisfactory.  Two points should be made regarding "reverse break",
   however.  First: having reverse break on the terminal is of course not
   sufficient; the operating system must support it.  As "support" is
   equivalent to "require" in this context, it is not too surprising
   that some systems do not in fact do this.  That is, there are systems
   which will not type through an unlocked keyboard until the user
   manually turns the line around, and the operational problems with
   such systems are much less than might be assumed.  Second, at least on
   IBM 2741's and equivalent, the line turnaround takes a significant
   amount of time, during which user-typed characters may be missed or
   garbled.  In fact, a fairly standard mode of operation with systems
   that use reverse break (including TIP's) is to automatically enter
   a "line delete" character and start over every time the reverse break
   is used while typing, which can hardly be called esthetic.  One
   solution to this problem would be for the system to not use reverse
   break once the user has begun typing (as suggested near the end of
   NIC #20812), but most systems (including TIP's) do not do this.



Hathaway
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