Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
However, this is not a correct approach in my viewpoint anymore. You see, many protocols are implemented as user-space programs, i.e. applications depending on the services provided by the application layer (the APIs, sockets, OS-specific issues). This would make them essentially application
Peter, oh my, perhaps not germane to network folk, but you're opening another "holy war" if you're going to classify things on what address space they occupy, i.e. what's really part of the OS vs. an application.
Back in the good olde days of monolithic spaghetti code, we didn't have to deal with such silly questions. 
Seriously, though, to the original poster, something to keep in mind, there's a reason why there's the word "model" in OSI Model. Real world can be a little more complex than the model and even the OSI Model isn't the only game in town. That's not to say your question is without merit, as it is, but I hope Peter's posting especially shows some of the difficultly in pigeon holing some things.
