Thread View: comp.protocols.iso
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Started by Howard C Berkowitz
Tue, 22 Dec 1992 17:09
FAQ you were afraid to ask
Author: Howard C Berkowitz
Date: Tue, 22 Dec 1992 17:09
Date: Tue, 22 Dec 1992 17:09
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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
Author: Mark Boolootian
Date: Tue, 29 Dec 1992 19:28
Date: Tue, 29 Dec 1992 19:28
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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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