From: ketil@edb.tih.no (Ketil Albertsen,TIH)
Subject: Re: Info wanted on TCP/IP vs OSI 7 layer
Organization: T I H / T I S I P 
Posting-Front-End: Winix Conference v 92.05.15  1.20 (running under MS-Windows)
Date: Thu, 28 Jan 1993 11:53:30 GMT

In article <1993Jan28.073137.7195@novell.com>, donp@novell.com (don provan) writes:

>Actually, what they usually show is how dismal the OSI model is for
>analysis.  Even the OSI protocols don't "fit" the OSI model in any
>significant analytical sense, with most of the layers turned sideways
>to allow functions to slip up or down at will.

Sorry, I don't understand what you mean by "layers turned sideways".
Could you explain? (Preferably with examples)

>Ironically, it's the OSI protocol suite itself which has the most drastic 
>examples of non-layering, although any competent network expert will tell 
>you that that, in itself, is not a deficiency.

Sure. The protocols came first, before a good taxonomy had been developed.
So the OSI guys had to face a decision: Should the taxonomy, the RM,
describe the world in the current messy state, or should we make an
attempt to be systematic, create a goal to work towards? They chose the
latter, and I think that was a good idea.

(A sidetrack: If your statement was intended to say that TCP/IP is well
layered, I think most datacomm people would protest! One thing is that
organizing 2/7 of the problem areas is much easier than organizing the
entire problem solution, another is that several textbooks make an
issue out of TCP/IP not being layered, but "hierarchical", in the sense
that the functionality of both levels is available to the programmer)

I think you could day that the more recent OSI protocols are generally 
closer to the model, but there are certainly some problems even in the
newer ones.

I do believe that in ten years, we will smile at the current low layers
in OSI (and that is NOT because IP will take over... :->). The coming of
ATM (and ISDN) will turn around a lot of the ways we think of network
problems. Of course we will still use both IP and X.25, but the trends
will be in quite a different direction.


>>>I am posting on behalf of a friend who needs to compare the layers of
>>>the internet protocol suite with the OSI seven layer model as part of
>>>his course assignment.
>
>Your friend would probably find it easier to do his homework himself.
>It doesn't take a significant amount of information about TCP/IP and
>the OSI model to do this analysis.  I doubt that cribbing the answer
>from some other source will acheive the educational goal that your
>friend's instructor had in mind.  And it's certainly not the kind of
>thing worth bothering thousands of people about.

I do not feel "bothered" by a discussion of Internet vs. OSI protocols,
even if what started the discussion was a question from a student.

As a college lecturer, I consistently urge the students to find information
in other sources, to search for non-textbook arguments and solutions.
"The real world" certainly looks different from the textbook image, and
I would say it is a good idea for a student to ask professionals in the
field how they feel about the Internet/OSI alternatives.

Ketil Albertsen, college lecturer