RFC 91 (rfc91) - Page 1 of 12

Proposed User-User Protocol

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Network Working Group                                    George H. Mealy
Request for Comments: 91                              Harvard University
                                                       December 27, 1970


                     A PROPOSED USER-USER PROTOCOL

INTRODUCTION:

   There are many good reasons, and maybe one or two bad ones, for
   making it appear that communication over the Network is only a
   special case of input/output -- at least as far as user programming
   is concerned.  Thus, for instance, the Harvard approach toward
   implementing the HOST-HOST protocol and Network Control Program
   treats each link as a "logical device" in PDP-10 terminology.
   Setting up a connection is similar to local device assignment, and
   communication over a link will make use of the standard system
   input/output UUO's.  This makes it possible to use existing programs
   in conjunction with the Network without modification -- at least if
   other PDP-10's are being dealt with.

   This takes us only so far, however.  The notion of a "logical device"
   does not exist on the PDP-10; it does on the IBM 360 (I am speaking
   here at the level of the operating system -- user program interface).
   Furthermore, in the absence of a Network standard requiring fixed
   representations for integers, reals, etc. (which I would oppose), any
   pair of user processes must arrive at a local agreement, and one or
   both must assume the burden of data conversion where necessary.  Any
   standard protocol should allow such agreements to be given expression
   and should accommodate at least the minimum of control information
   that will allow such agreements to function in practice.  Finally, we
   must note that the IMP-IMP and HOST-HOST protocols do not provide for
   a check that an action requested by a user process is actually
   accomplished by the other processes; this type of issue has always
   been regarded as subject to treatment at the USER-USER protocol
   level.

   This proposal is intended to face the above three types of issue only
   to a certain extent.  I can best explain that extent by stating the
   criteria I would use to judge any USER-USER protocol proposal:











Mealy
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