When talking about data communication, the OSI model is the golden reference model for how data is communicated between any two networked systems. OSI stands for Open Standards Interconnect model and was created by the International Standards Organization to overcome difficulties in interoperation between networking technologies. The OSI model specified the concept of layers and defined the function offered on each layer. These layers are broken into seven different segments. The layer go as followed; physical, data-link, network, transport, session, presentation, and application. The physical layer is the lowest layer in the model and is for the purpose of maintaining and transmitting bits about physical connections through mechanical, electrical and other functionalities. For example this may be something like optical signals (optic fiber), or electromagnetic waves (wireless networks).
The physical layer is the only layer that interacts with nature. After data has been processed by all other layers, it finally reaches the physical layer where the data hits the wire. Before the data reaches the network layer, it has to pass through the data-link layer. The main purpose of this layer is to send data between neighboring devices on the network through signaling service. The two primary functions are addressing and error-detection. A good example of the data-link layer in action is the internet. The data-link layer is the building block of the internet, so when you use the internet, information passes through many instances of the data-link layer before it reaches its final destination, each instance of the layer warrants that the data is safe to go to the next destination in the network.
The network-layer provides the functional and procedural means to transfer packets of data from a source computer to a destination computer through one or more networks. Its function is used for packet forwarding, managing quality of services, and forwarding local host domain messages to the transport layer. The standard protocol used by all networks at this layer is the Internet protocol (IP). IP designates an address to every device on a network. The function of this layer can be summarized by the term routing, which is the process of selecting a path on the internet that can be used to deliver data to a destination. Routing is performed by devices called routers which connect two or more networks and forward incoming packets to the appropriate connected network. Since an address is defined by IP, the sender adds the destination's IP address to the header of every data packet sent out on the network.
No lines are longer than 80 characters, TYVM. Other specified properties aren't being scored automatically at this time so this is not necessarily good news...