Articoli
RFC 0037 - Network Meeting Epilogue
In questo RFC viene fatto un resoconto delle tematiche affrontate nel network meeting ospitato da Crocker a UCLA: si discute sulla complessità dell'uso del protocollo ed altre particolari caratteristiche.
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.
[Page 1]
_
RFC 37 Network Meeting Epilogue, etc. 20 March 1970
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.
[Page 2]
_
RFC 37 Network Meeting Epilogue, etc. 20 March 1970
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."
[Page 3]
_
RFC 37 Network Meeting Epilogue, etc. 20 March 1970
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.
[Page 4]
_
RFC 37 Network Meeting Epilogue, etc. 20 March 1970
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 ]