1. Physical layer
2. Link layer
3. Network layer
4. Transport layer
5. Application layer
Layer 1 is the physical layer defines electrical aspects of activating and maintaining physical links in networks. The physical layer represents the basic network hardware, such as switches and routers.
Layer 2, the link layer, provides a reliable synchronization and transfer of information across the physical layer for accessing the transmission medium. Layer 2 specifies how packets access links and is attached to additional headers to form frames when entering a new networking environment, such as a LAN.
Layer 3, the network layer (IP) specifies the networking aspects. This layer handles the way that addresses are assigned to packets and the way that packets are supposed to be forwarded from one end point to another.
Layer 4, the transport layer, is just above the network layer and handles the details of data transmission. Layer 4 is implemented in the end-points but not in network routers and acts as an interface protocol between a communicating host and a network.
Layer 5, the application layer, determines how a specific user application should use a network. Among such applications are the Simple Mail Transfer Protocol File Transfer Protocol and the World Wide Web.