Osi Model

OSI Model

The OSI model is used to describe networks and network applications. The OSI model uses a layered approach which communication subsystem is broken down into seven layers. The seven layers in the OSI model which are application, presentation, session, transport, network, data link and physical layer. The application layer is used for file transferring, Presentation layer makes communication between two hosts possible. The Session layer is used for starting and ending a communication across a network. Transport layer is responsible for message delivery between hosts. The network layer is responsible for translating their logical network and names into their physical address. The data link layer is used to control errors between adjacent nodes and the physical layer is responsible for transmitting row bit stream over the physical cable. OSI Model is a set of protocols that try to identify and homogenize the data communication practices. Wan protocols function at the lower 3 levels but most WAN protocols function on the second layer which is the data link layer. Some Wan protocols frame relay, high-level data link control, and point to point protocol. Routers operate on the network layer which is layer 3 in the OSI model. In the OSI model switches operate on the data link layer which is the second layer. Routers do not reside at more than one layer routers route at layer 3 which is the network layer. Routers work on the network layer so they can filter data based on IP addresses. Routers do work on other layers but do not reside there the routers work on layer 2 when they switch packet interfaces and layer and put signals on layer 1.