* The five-layer model provides guidelines for the development of universally compatible networking protocols. * The physical, data link, and network layers are the network support layers. * The application layer is the user support layer. * The transport layer links the network support layers and the user support layer. * The physical layer coordinates the functions required to transmit a bit stream over a physical medium. * The data link layer is responsible for delivering data units from one station to the next without errors. * The network layer is responsible for the source-to-destination delivery of a packet across multiple network links. * The transport layer is responsible for the process-to-process delivery of the entire message. * The application layer enables the users to access the network.