sorry for that question, but i've searched about that topic, and it's not really clear, they say that internet uses tcp/ip but sometimes they say that osi also is used! for example, UDP application, they dont use tcp/ip since it's not a tcp?!
please, can someone make it clear? mean; where is "exactly" OSI is used, and where is "exactly" TCP/IP is used!
The internet is based on TCP/IP which is a "simplified" implementation of the theoretical OSI model. Maybe it's even better to say TCP/IP was inspired by the OSI model, since it does not really match up on closer review.
More info here:
http://en.wikipedia.org/wiki/OSI_model#Comparison_with_TCP.2FIP_model
and here:
http://en.wikipedia.org/wiki/TCP/IP_model#OSI_and_TCP.2FIP_layering_differences