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2 messages
2 total messages Started by Howard C Berkowitz Tue, 22 Dec 1992 17:09
FAQ you were afraid to ask
#1257
Author: Howard C Berkowitz
Date: Tue, 22 Dec 1992 17:09
87 lines
4034 bytes
The Seven Deadly Layers

Among the most frequent questions I'm asked in OSI teaching 
is "do I need to know what all the layers do?"  This is 
especially true of management audiences, who _need_ to know 
the power centers.   They may not know what a layer is, but 
they know there are seven of them and they don't want a 
single one to go unsupervised. :-)

Over the years, I have found a useful analogy.  Educational 
theory suggests we should start with something that the 
student knows, and build from there.

Therefore, I ask management audiences to reflect not on 
theoretical network architecture, but on sin.  Specifically, 
I ask them to consider the Seven Deadly Sins.

These sins  have definite relevance to the OSI Reference 
Model.  The "most popular" deadly sins are analogies for the 
layers most important for non-developers to know about.

Audiences think of sins in a fairly consistent way.  
Approximately 75% immediately think of Lust.

Lust, clearly, relates directly to the Physical Layer.  It 
is essential to be aware of the function of the Lust Layer, 
for that defines how to Plug In.  [1]

Most of the remaining audience splits among Avarice and 
Gluttony.  These also are important in OSI.  

Avarice, or Greed, is often realized as the Bottom Line in 
business.  One is closer to understanding the Tao of OSI 
when one realizes that it places the Bottom Line (i.e., what 
OSI does for real user applications programs) on Top.  The 
top of the Avarice Layer is the Service Access Point to the 
Application, or Avarice, Layer. [Note 2]

Those members of the audience who thought first of Gluttony 
also have some understanding of OSI.  Gluttony deals with 
establishing a relationship between a mouth entity and a 
food entity; Network deals with the next course while 
Transport deals with the end goal of dessert.

Users really need to know the functions of Application, 
Transport/Network (as the distinction blurs here), and 
Physical.  International Standardized Profiles follow this 
model:  Application is the visible part of A-, B-, or 
Avarice Profiles; Transport and Network define T- and U-
profiles, and Physical deals with the bottom of T- and U-
profiles.  These four components also, for instructional 
purposes, nicely describe the major protocol levels of the 
Internet Protocol Suite:  application protocols, TCP and 
UDP,IP, and interface protocols.

There is always one in the audience, however, who thinks of 
Sloth.  

Sloth is a difficult sin. How does one confess it?  "Bless 
me, I have slothed?"  "Forgive me for committing sloth?  How 
can I commit not doing something?"

Since Sloth is a sin we really have trouble talking 
about,and involves not doing useful things, it is a relevant 
analogy to the Session Layer.  Both Sloth and Session are 
needed for theological completeness, but their relevance to 
the ordinary sinner or the OSI user is fairly limited.[Note 
3].

 
----- 

[Note 1]    When presenting these analogies at an IEEE 
conference in New York, a woman's clear voice rang out from 
the back of the room, "Well, I'm glad SOME standards body is 
defining how to plug in things correctly.  God knows most 
male engineers don't understand that at all."

[Note 2]  This part of the analogy can continue into 
Application Service Elements:  ACSE, the Avarice Control 
Service Element; ROSE, the Remote Organization Submission 
Element; etc.

[Note 3]  After their first reading of Presentation Context 
Negotionation and ASN.1 Basic Encoding Rules, some nominate 
the sin of Pride as the proper analogy for the Presentation 
Layer.
Re: FAQ you were afraid to ask
#1268
Author: Mark Boolootian
Date: Tue, 29 Dec 1992 19:28
128 lines
6240 bytes
In article <Bzo7oB.B7p@world.std.com> hcb@world.std.com (Howard C Berkowitz) writes:
>The Seven Deadly Layers

I posted the following message to the ietf mailing list some time ago.  I still
don't know who the originator of this version of the seven layer/seven sin
mapping is.

-- begin include text --


Date: Fri, 15 May 92 09:54:09 PDT
From: booloo@framsparc.ocf.llnl.gov (Mark Boolootian)
Message-Id: <9205151654.AA00940@framsparc.ocf.llnl.gov.ocf>
To: ietf@isi.edu
Subject: Seven layers, seven sins, seven dwarfs, seven days, etc...

Some time ago, someone  posted a message stating the relationship between the 
seven OSI layers and the seven deadly sins (I apologize profusely for not 
recalling the author's name, and even more so if this was posted to another 
list and not ietf).  The chap in the office next door to me, John Fletcher, has
been compelled to add his commentary, which I am posting for him and here
follows:



                                Seventh Heaven

    The opposition to Galileo consisted primarily of those who believed that 
all knowledge could be arrived at deductively from first principles of a 
presumedly compelling nature.  Some of the opponents would not even look at 
Jupiter through Galileo's telescope, because they had already deduced the 
impossibility of there being any moons to be seen.  A sample of their reasoning
is here quoted in translation:

    There are seven windows in the head, two nostrils, two eyes, two ears, and 
a mouth; so in the heavens there are two favorable stars, two unpropitious, 
two luminaries, and Mercury alone undecided and indifferent.  From which and 
many other similar phenomena of nature, such as seven metals, etc., which it 
were tedious to enumerate, we gather that the number of planets is necessarily 
seven.

    Among the unenumerated sevens known at that time one can think of days of 
the week, wonders of the ancient world, and deadly sins.  From our modern 
vantage point we can list even more, including dwarves visited by Snow White 
and, of course, layers of OSI protocol.

   The quotation indicates that there is a natural correspondence from one 
seven to the next, such as the mouth with the planet Mercury and (one may 
infer) also with the metal quicksilver and the day Wednesday.  So now that we 
have some insight into the origins of the sevenness of the OSI layering, it 
would seem that our understanding and appreciation in regard to each of those 
layers might be enhanced considerably if we were able to establish its 
correspondence with the members of the other sevens.  Work in this direction 
has already begun.  A recent correspondence, which I here append, has matched 
the layers with the deadly sins.  I also include a result of my own 
investigations.


                           The Seven Deadly Layers


ISO Layer        Corresponding Sin              Rationale


Application      Wrath                  Application is forever angry at the
                                        mess it sees below (it should point
                                        fingers?).

Presentation     Sloth                  Presentation is too lazy to do 
                                        anything productive itself.

Session          Lust                   Session always lusted after what 
                                        truly was Application functionality.

Transport        Avarice                Transport always wanted all of the 
                                        end-to-end functionality (of 
                                        course, it deserved it, but life 
                                        ain't fair).

Network          Gluttony               Network, more precisely Connection-
                                        Oriented Network, was always overweight
                                        and overbearing, the result of trying 
                                        too often to eat Transport's lunch.

Data Link        Envy                   Poor DLL is always starved for 
                                        attention (with ATM, maybe it is 
                                        finally feeling less neglected).

Physical         Pride                  Phy roundly averted much of the 
                                        controversy and nearly all of the 
                                        embarrassment.




                        Snow White and the Seven Layers


ISO Layer        Corresponding Dwarf            Rationale


Application      Doc                    is acting as if it is in charge, but 
                                        sometimes muddling its syntax.

Presentation     Sleepy                 is behaving in accord with its sin of 
                                        Sloth.

Session          Dopey                  is confused because its charter is not 
                                        very clear.

Transport        Grumpy                 is irritated because Network has 
                                        encroached onto its turf.

Network          Happy                  is smiling for the same reason that 
                                        Transport is irritated.

Data Link        Sneezy                 is making loud noises in the hope of 
                                        attracting attention.

Physical         Bashful                is quietly going about its work, 
                                        unnoticed by the others.

-- end included text --


-- 
Mark Boolootian		booloo@llnl.gov		+1 510 423 1948
Disclaimer:  My fingers type for me alone.
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