Basing on the distinction between the physical network and the virtual network, this paper defines an Internet reference model which has six layers: physical link, data link, physical network, virtual network, transport service and application layer. Comparing to the reference model used by most textbooks, one extra network layer is added to accommodate both the virtual and physical network layers. This paper gives clear definitions for every layers too. The goal of this paper is to present a correct and easy-to-understand reference model for Internet.Â