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From: darrell@sdcsvax.UUCP
Newsgroups: mod.os
Subject: Re: Submission for mod-os; distributed computer systems
Message-ID: <2713@sdcsvax.UCSD.EDU>
Date: Thu, 12-Feb-87 23:52:13 EST
Article-I.D.: sdcsvax.2713
Posted: Thu Feb 12 23:52:13 1987
Date-Received: Sat, 14-Feb-87 12:48:43 EST
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Organization: NASA Ames Research Center, Moffett Field, Calif.
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John Mashey points out:
> I point out about distributed systems:
>>1) expensive, 2) hard, 3) lacking in pay-off, appreciation, etc....
>>....
>I'd agree with 1) & 2), but I'm surprised at 3): I'd bet that most technical
>shops have a wide variety of machines, and even if things aren't transparently
>distributed, but they're at least networked together.

I have come to believe we (Ames, Silicon Valley, Usenetter) are the
exception rather than the rule.  Ames is the ONLY NASA Center with a
complete network, and we have many machines not on any net for perceived
security reasons (owners believe in thousands of urchins....).  I think
this is because LANs are very political, not just technical (hence my
Martin comment).  BTW: if you want to know how Ames did it, send mail,
I could not get JPL to do this in three years, and there are halting
efforts right now.

>In the commercial world, there is substantial use of distributed systems;

I don't think this is by choice.  Single threads are much easier to
control (usual perception, not always).

>> Watson triangle.....
>Greg Chesson puts it, "If you think networking people do weird hacks for
>performance, they probably got that way by doing them as OS people beforehand."
>(or something like that)

Well Dave Clark came out here from MIT and gave a talk on why protocols
perform poorly, I'll drop his viewgraphs by John.  He blasted the OS
people for the "process-oriented" model of protocol implementation. (No
pun intended with the Blast protocol.

>It seems to me that there are many real-live distributed systems around,
>although the degree of transparency is low, except for a few homogeneous
	Agreed!
>systems.  Some heterogeneous nets are starting to show signs of load-balancing,
>but we have a long way to go.  Of course, the increasing prevalence of UNIX,
>even with all of its faults, may at least help this.  After all, it hasn't
>been all that many years since you not only could NOT do anything complex
>in a portable way, but it was even hard to get the same FORTRAN program
>to do the same thing on multiple vendors' machines.

I think your heterogeneous point is well taken.  Gerald Popek came
talking about LOCUS and other distributed systems.  I argued his system
did not have enough diversity.  I know others who would argue for more
STANDARDIZATION [I would disagree, but their views should be made obvious]
like a standardized instruction set. [Yes I know IBM, and also DOD h/w
efforts.]

To tell you the truth, other than physical separation of elements, I
don't know how I would define a distributed system.  Clark, BTW,
mentioned the satellite delay problem [protocols expecting shorter
delays because the networks were written for ground based communiation
systems, satellite signals would time out].

The people [or team] who solves the problems of distributed systems will
have to take an integrated view.  In 1946 in order to break the sound
barrier, a problem had to be overcome, a social one, not a technical one:
the airframe people were not talking to the power plant people.  The
powerplant people had jets which could literally tear wings off planes
(straight wings like the X-1).  Well, a guy who is now at Ames got the
idea to sweep wings back.  An aerodynamicist would have never swept
the wings back from a prop plane: too much lift lost.  The point is
the integration of these two technologies: swepted-wings and jet engines
puts us ahead (the combination being a resultant product which is better),
it's a gestalt thing.  I think the same thing will have to happen in this
area.  Are uniprocessors best designed by one man, or are
multiprocessors and distributed systems `camels' [horses designed by
committees, not quality desert animals] best designed by committee?
I don't know.

>From the Rock of Ages Home for Retired Hackers:

--eugene miya
  NASA Ames Research Center
  eugene@ames-aurora.ARPA
  "You trust the `reply' command with all those different mailers out there?"
  "Send mail, avoid follow-ups.  If enough, I'll summarize."
  {hplabs,hao,nike,ihnp4,decwrl,allegra,tektronix,menlo70}!ames!aurora!eugene