RFC 89 (rfc89) - Page 2 of 7

Some historic moments in networking

RFC 89            SOME HISTORIC MOMENTS IN NETWORKING    19 January 1971


   Brodie, Knight, Metcalfe, Meyer, Padlipsky and Skinner) was
   commissioned to establish a 'polite conversation' between a Multics
   terminal and an MITDG terminal.

   It was agreed that messages would be what we call 'network ASCII
   messages': 7-bit ASCII characters right-adjusted in 8-bit fields
   having the most significant bit set, marking, and padding.  In that
   Multics is presently predisposed toward line-oriented half-duplex
   terminals, it was decided that all transmissions would end with the
   Multics EOL character (ASCII ).  To avoid duplicating much
   of the INCP in our experiment, the PDP-10 side of the connection was
   freed by convention from arbitrary bit-stream concatenation
   requirements and was permitted to associate logical message
   boundaries with network message boundaries (sic).  The 'polite
   conversation' was thus established and successful.

   Multics, then, connected the conversation to its command processor
   and the PDP-10 terminal suddenly became a Multics terminal.  But, not
   quite:

   First, in the resulting MITDG-Multics connection there was no
   provision for a remote QUIT, which in Multics is not an ASCII
   character.  This is a problem for Multics.  It would seem that an
   ASCII character or the network's own interrupt control message could
   be given QUIT significance.

   Second, our initial driver program did not provide for RUBOUT.
   Because the Multics network input stream bypassed the typewriter
   device interface module (TTYDIM), line canonicalization was not
   performed.  In a more elegant implementation, line canonicalization
   could be done at Multics, providing the type-in editing conventions
   familiar to Multics users.  We fixed this problem hastily by having
   our driver program do local RUBOUT editing during line assembly, thus
   providing type-in editing conventions familiar to MITDG users.  It is
   clearly possible to do both local type-in editing and distant-host
   type-in editing.

   Third, we found that because of the manner in which our type-in
   entered the Multics system under the current network interface (i.e.
   not through TTYDIM), our remotely controlled processes were
   classified 'non-interactive' and thus fell to the bottom of Multics
   queues giving us slow response.  This problem can be easily fixed.

The Harvard Connection

   Connecting MITDG terminals to Multics proved to be easy in that the
   character-oriented MITDG system easily assembled lines for the
   Multics line-oriented system.  We (Messrs. Barker, Metcalfe) decided,



Metcalff