Neither the OSI model and its protocols nor the TCP/IP model and its protocols are perfect. Quite a bit of
criticism can be, and has been, directed at both of them. In this section and the next one, we will look at some of
these criticisms. We will begin with OSI and examine TCP/IP afterward.
At the time the second edition of this book was published (1989), it appeared to many experts in the field that the
OSI model and its protocols were going to take over the world and push everything else out of their way. This did
not happen. Why? A look back at some of the lessons may be useful. These lessons can be summarized as:
1. Bad timing.
2. Bad technology.
3. Bad implementations.
4. Bad politics.
Bad Timing
First let us look at reason one: bad timing. The time at which a standard is established is absolutely critical to its success. David Clark of M.I.T. has a theory of standards that he calls the apocalypse of the two elephants,
This figure shows the amount of activity surrounding a new subject. When the subject is first discovered, there is a burst of research activity in the form of discussions, papers, and meetings. After a while this activity subsides, corporations discover the subject, and the billion-dollar wave of investment hits.
It is essential that the standards be written in the trough in between the two ''elephants.'' If the standards are
written too early, before the research is finished, the subject may still be poorly understood; the result is bad
standards. If they are written too late, so many companies may have already made major investments in
different ways of doing things that the standards are effectively ignored. If the interval between the two elephants
is very short (because everyone is in a hurry to get started), the people developing the standards may get
crushed.
It now appears that the standard OSI protocols got crushed. The competing TCP/IP protocols were already in widespread use by research universities by the time the OSI protocols appeared. While the billion-dollar wave of investment had not yet hit, the academic market was large enough that many vendors had begun cautiously offering TCP/IP products. When OSI came around, they did not want to support a second protocol stack until they were forced to, so there were no initial offerings. With every company waiting for every other company to go first, no company went first and OSI never happened.
A Critique of the OSI Model and Protocols
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Oleh
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