RFC37

Network Working Group S. Crocker Request for Comments: 37 UCLA

                                                      20 March 1970

                 Network Meeting Epilogue, etc.

The Meeting

---

 On Tuesday, March 17, 1970, I hosted a Network meeting at UCLA.
 About 25 people attended, including representatives from MIT, LL,
 BBN, Harvard, SRI, Utah, UCSB, SDC, RAND and UCLA.  I presented a
 modification of the protocol in NWG/RFC #33; the modifications are
 sketchily documented in NWG/RFC #36.  The main modification is the
 facility for dynamic reconnection.

 The protocol based on sockets and undistinguished simplex
 connections is quite different from the previous protocol as
 documented in NWG/RFC #11.  The impetus for making such changes came
 out of the network meeting on December 8, 1969, at Utah, at which
 time the limitations of a log-in requirement and the inability to
 connect arbitrary processes was seriously challenged.  Accordingly,
 the primary reason for the recent meeting was to sample opinion on
 the new protocol.

 Recollections may vary, but it is my opinion that the protocol was
 widely accepted and that the criticism and discussion fell into two
 categories:

 1.  Questioning the complexity and usefulness of the full protocol,
  especially the need for dynamic reconnection.

 2.  Other topics, particularly character set translation, higher
  level languages, incompatible equipment, etc.

 Notably lacking was any criticism of the basic concepts of sockets
 and connections.  (Some have since surfaced.)  The following
 agreements were made:

 1.  By April 30, I would be responsible for publishing an
  implementable specification along lines presented.

 2.  Any interested party would communicate with me (at least)
  immediately if he wished to modify the protocol.

 3.  If major modifications come under consideration, interested
  parties would meet again.  This would happen in two to three
  weeks.

 4.  Jim Forgie of Lincoln Labs tentatively agreed to host a meeting
  on higher level network languages, probably near Spring Joint
  time.

Mailing List Changes

---

 Paul Rovner of LL is replaced by

               James Forgie
               Mass. Institute of Technology
               Lincoln Laboratory C158
               P.O. Box 73
               Lexington, Mass. 02173

               telephone at (617) 862-5500 ext. 7173

 Professor George MEaly is added

               George Mealy
               Rm. 220
               Aitken Computation Lab.
               Harvard University
               Cambridge, Massachusetts 02138

               telephone at (617) 868-1020 ext. 4355

Process

---

 In all of our writing we have used the term process, to mean a
 program which has an assigned location counter and an address space.
 A program is merely a pattern of bits stored in some file.  A new
 process is created only by an already existing process.  The
 previous process must execute an atomic operation (forc, attach,
 etc.) to cause such a creation.  Processes may either cause their
 own demise or be terminated by another (usually superior) process.

 The above definition corresponds to the definition given by
 Vyssotsky, et al on pp.  206, 207 of "Structure of the Multics
 Supervisor" in the FJCC proceedings, 1965.

 Because a process may create another process, and because in general
 the two processes are indistinguishable when viewed externally, I
 know of no reasonable way for two processes to request connection
 directly with each other.  The function of sockets is to provide a
 standard interface between processes.

The Days After

---

 In the time since the meeting I have had conversations with Steve
 Wolfe (UCLA-CCN), Bill Crowther (BBN), and John Heafner and Erick
 Harslem (RAND).  Wolf's comments will appear as NWG/RFC #38 and fall
 into a class I will comment on below.

 Crowther submitted the following:

 "A brief description of two ideas for simplifying the host protocol
 described at the March meeting.  These ideas have not been carefully
 worked out.

 Idea 1. To Reconnect.
 --------------------

 "A NCP wanting to Reconnect tells each of his neighbors "I want to
 reconnect".  They wait until there are no messages in transit and
 respond "OK".  He then says "Reconnect as follows" and they do it.
 In the Rare condition, the NCP gets back an "I want to reconnect
 instead of an "OK", then one must go and one must stop.  So treat a
 "reconnect" from a higher Host user etc. as an ok and from a lower
 as a "No-wait until I reconnect you" and do the connection.

 Idea 2
 ------

 "Decouple connections and links.  Still establish connections, but
 use any handy link for the messages.  Don't send another message on
 a connection until a FRNM comes back.  Include source and
 destination socket numbers in the packet.

 "To reconnect, say to each of neighbors "please reconnect me as
 follows...".  Hold onto the connect for a short time (seconds) and
 send both packets and connection messages along toward their
 destinations.  I haven't worked out how to keep the in-transit
 messages in order, but probably everything works if you don't send
 out a reconnect when RFNM's are pending."

 Bill's first idea does not seem to me to be either decisively better
 or (after some thought) very different, and I am considering it.  I
 have no strong feelings about it yet, but I am trying to develop
 some.

 Bill's second idea seems contrary to my conception of the role of
 links.  An argument in favor of decoupling connections and links
 that the number of connections between two hosts might want to
 exceed 255, and that even if not, it is sounder practice to isolate
 dependancies in design.  On the other hand, the newly provided Cease
 on Link facility* (page 22 of the soon to be released BBN report
 #1822 revised Febuary 1970) becomes useless.  (Bill, who just put
 the feature in, doesn't care.)  Another objection is that it seems
 intuitively bad to waste the possibility of using the link field to
 carry information.  (Note the conflict of gut level feelings).

 In a conversation with John Haefner and Eric Harslem of RAND, the
 pointed out that the current protocol makes no provision for error
 detection and reporting, status testing and reporting, and expansion
 and experimentation.  Error detection and status testing will
 require some extended discussion to see what is useful, and I expect
 that such discussion will take place while implementation proceeds.
 Leaving room for protocol expansion and experimentation, however, is
 best done now.

 I suggest that two areas for expansion be reserved.  One is that
 only a fraction of the 256 links be used, say the first 32.  The
 other area is to use command codes from 255 downward, with permanent
 codes assigned from the number of links in use to 32, I feel that it
 is quite unlikely that we would need more than 32 for quite some
 time, and moreover, the network probably wouldn't handle traffic
 implied by heavy link assignment.  (These two things aren't
 necessarily strongly coupled:  one can have many links assigned but
 only a few carrying traffic at any given time.)

 Some of Heafner's and Harslen's other ideas may appear in NWG/RFC
 form.

 Immediate Interaction
 ---------------------

 During the next several days, I will still be interested in those
 editicisms of current protocol which might lead to rejection or
 serious modification of it.  Thereafter, the focus will be a
 refinement, implementation, extension, and utilization.  I may be
 reached at UCLA through my secretary Mrs. Benita Kristel at (213)
 825-2368.  Also, everyone is invited to contribuet to the NWG/RFC
 series.  Unique numbers are assigned by Benita.

 * The Cease on Link facility is a way a receiving host modifies
RFNM's so as to carry a flow-quenching meaning.  An alternative
proceedure is to use a host-to-host control command.

   [ This RFC was put into machine readable form for entry ]
    [ into the online RFC archives by Ron Fitzherbert 1/97 ]