Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!nrl-cmf!ames!lll-winken!uunet!cos!howard
From: howard@cos.com (Howard C. Berkowitz)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Some alternatives to OSI
Summary: Theology
Message-ID: <17459@cos.com>
Date: 1 May 89 16:26:20 GMT
References: <3489@robin.cs.nott.ac.uk> <12486384267.18.PADLIPSKY@A.ISI.EDU> <17344@cos.com>
Organization: Corporation for Open Systems, McLean, VA
Lines: 63



I am often asked by audiences new to OSI, "Why are there seven layers?"
The most accurate answer to this, of course, is "because there are."

[If I wanted to be REALLY accurate, I would comment that seven
layers are an arbitrary decomposition done long before any OSI
implementations; equally good cases could be made for five or
eleven, or other numbers.  Would the Bill of Rights be more
or less useful if the same material were covered in nine or
eleven Amendments].

Of course, the real question being asked is, "Do I need to know what
all seven layers do?"  Now, if the questioner is a typical MIS
manager or other end user, the answer is "no, only developers really
need to know."

Since this answer makes many people suspicious of Secret Mysteries,
I appeal to their experience.  Most MIS managers, while unfamiliar
with the esoteric theology of network architecture, are reasonably
familiar with Sin.

Audiences exhibit reasonably consistent behavior when asked to
consider the Seven Deadly Sins.  Approximately 75% of the audience,
asked to consider these sins, immediately thinks of Lust.

This is entirely appropriate to the OSI Reference Model, because
Lust is clearly the Physical Layer.  The mechanisms associated
with male and female connectors clearly are instantiations of 
Lust architecture.

In general, the rest of the audience (with key exceptions) has
thought of Avarice and Gluttony.  These, also, have their OSI
counterparts.  If one thinks of Avarice in a business context,
one thinks of The Bottom Line; OSI architects simply put the
Bottom Line on top, and named it Application.  One should know
what the Bottom Line is, even when it is on top.

Gluttony deals with Reaching Out and Touching, Ingesting, etc.
These are clearly functions of the Network and Transport
Layers (i.e., Network being associated with the adjacent course
of the meal, while Transport is more concerned with eventual
dessert), and all OSI users need to be nourished.

In any audience, however, there is always one (and usually
only one) who thinks of Sloth.  

Sloth is analogous to the Presentation Layer.  No one knows
exactly what Sloth is or even how to confess it (bless me, for
I have committed Sloth?  or, I have slothed...?).  Nevertheless,
it is necessary for theological completeness of the Sin Reference
Model. 
 
In like manner, no one really knows why presentation is there,
other than for theological completeness of the OSI Reference
Model.   MIS users may safely ignore it; only implementors in
the parishes need be concerned with it.   

-- 
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