A defense of GOSIP


Karl Auerbach (AUERBACH@CSL.SRI.COM)
Thu 12 Mar 87 18:48:01-PST


I think GOSIP is a good idea. I support it.

I have read GOSIP. I have read, indeed participated in, the NBS
Implementors' workshops. I have read, and believe I understand many,
if not most of the ISO and CCITT specifications. I have been
implementing one of the larger parts (X.400).

1. As for GOSIP mandating a universal government wide requirement: No
matter how one reads the express language of the document, does anyone
really think that agencies will abandon SNA? If SNA is an implicit
exception why not TCP, XNS, ... ?

2. The entire validity of the ISO protocol suite has been called into
question because some of the standards have changed as they progressed
through the standardization process. So what? Couldn't the same
reasoning be applied to the TCP suite because new RFC's are issued?

Yes, the ISO protocols and services are changing. Our own X.400
implementation will be, in part, invalidated due to changes which will
be "approved" next year.

And is ISO missing important parts? Yes. For instance its protocols
for handling routing between intermediate systems ("gateways" in TCP
terms) are still being developed. But can one really say that the
Internet has done a really good job of inter-gateway routing?

Does MAP/TOP contain some really incredibly dumb ideas? Yes. For
example, network level addresses (NSAPs) contain the PHYSICAL media
addresses (e.g. the 48 bit Ethernet address). This can become a
management nightmare, especially as the NSAP is a necessary component
of higher level addresses and will be stored by the various
application level directory services. But this oddity is NOT a
necessary part of ISO, only a temporary expedient reasonably adopted
by the MAP folks to defer inventing ARP and routing protocols. GOSIP
places a high priority on resolving this issue. And answers are
presently being considered, just read for example, RFC 995.

Does this mean that one should not "go ISO". Perhaps, if you are
measuring costs over a short term. But, if you take a long view, and
believe that ISO will, in fact, mature, then perhaps you ought to
invest now, grow-up with the technology, and avoid a conversion
expense.

3. The ISO protocols and services contain many, many good ideas. They
are in many respects superior to TCP services. There has been
criticism that the ISO work is bloated. I believe this is a valid
objection. But if you look at the Implementors' Agreements you will
find many portions of the full ISO specifications which have been
chopped off or limited. In addition, as I have worked with ISO my
viewpoint has changed. For example, at first I considered most of the
session synchronization functions to be questionable. Why should I
pay their cost when I am never going to use them? It turns out that
they are extremely useful. And, in practice, they don't seem to cost
much. I remember similar arguments being raised by assembler language
programmers against "the terrible waste of high level languages."

               --karl-- Karl Auerbach
                         Epilogue Technology Corporation
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