Despite the success of the Internet in replacing all the previous
attempts to build a global computer communication system, some
engineers haven't updated their thinking from old descriptions of
networks. Instead, they still cling to the outdated 7-layer reference
model that was invented by ISO instead of the 5-layer reference model
that was invented for the Internet. Interestingly, engineers who
insist on using the older model cannot identify single protocol at
layers 5 and 6. But... because they learned the model somewhere in
school, they desperately hope that the extra layers must be
useful. As a result, they incorrectly classify applications
as layer 7 instead of layer 5.
Researchers have begun looking into the origins and uses of the OSI
7-layer reference model to determine why a cumbersome and inaccurate model
has had such staying power. They have recently uncovered some surprising
facts. We have known for a long time that the model was the work of a
group. We did not know, however, that the group met late one night in a
bar and began making fun of American pop culture. As it turns out, they
started scribbling names of the seven dwarfs from the Disney movie on a
paper cocktail napkin, and somebody joked that seven was a really good
number for network layers. The next morning at the standards committee
meeting, the group passed around the cocktail napkin and generally
agreed that that they had discovered something fundamental the previous
night while they were drunk. By the end of the day, they had renamed
the seven layers (with names that sounded more scientific), and produced
the basic model. Here's the lineup and a bit of explanation:
|
Layer |
Dwarf |
Name |
Explanations |
|---|---|---|---|
|
|
|
|
|
|
1 |
Sleepy |
Physical |
The group new that physical connections are boring, and
figured it might as well assign the
physical layer to dwarf ``Sleepy''. As it
happens, a Layer 1 protocol specification does
indeed put everyone to sleep (just try reading
one late at night).
|
|
2 |
Sneezy |
Link |
If you monitor a network and watch the pattern
of packets emitted by a computer, you'll
immediately understand the relationship between
link-layer protocols and ``Sneezy''.
|
|
3 |
Happy |
Network |
Everyone's happy with the network layer.
Well... to be honest, the only network layer
protocol that makes everyone's happy is the
Internet Protocol. Unfortunately, the Internet
protocol isn't part of OSI, and wasn't really
built to follow the OSI model (the model
didn't include internetworking). But, the
designers had good intentions.
|
|
4 |
Doc |
Transport |
This one's obvious -- it definitely takes a
Ph.D. to understand the subtleties of a
transport layer protocol.
|
|
5 |
Dopey |
Session |
Yep, even the designers realized that having a
separate session layer is a dopey idea. They
decided to follow Disney's approach of adding
comic relief, so they stuck in a completely
unnecessary layer and laughed about it.
|
|
6 |
Bashful |
Presentation |
Another little joke. The designers realized that
sooner or later someone would create a presentation
layer protocol. However, the group decided to
classify such protocols as too ``bashful'' to
appear in public. So, even if a presentation
protocol is produced, no one gets to see it.
|
|
7 |
Grumpy |
Application |
Programmers who design network applications are
incredibly grumpy -- they complain about the
efficiency of other layers, the fundamental
abstractions of the network, the long hours,
the difficulty of debugging, and the API they
are forced to use. And users add to the
grumpiness because users never complain about
protocols at other layers; they only complain
about applications.
|
Moral of the story: If you're an engineer working on a standards committee,
avoid drinking with colleagues -- a bad joke you hatch late one night in the
bar could turn out to haunt the industry for decades.