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OSI consists of two environments; the OSI environment, which is made up of seven layers of OSI protocols and the local system environment, which is the end computer system. The reason for dividing the environment in this way was to avoid interfering with the innovation of the design and implementation of computer systems. OSI facilitates a vehicle to communicate between dissimilar or similar computer based systems. The local computer system environment has a closed operating system and performs its designed functions within these bounds. | The router can then consult the table to select the least costly most efficient route to a destination. It gathers information by watching for routing table broadcasts by other routers and updating its own table in the event that a change occurs. RIP routing tables has following minimum entries: IP destination address, A metric (1 to 15) indicative of the total cost in hops, of a particular route to a destination, IP address of a the next router that a datagram would reach , on the path to its destination, A maker signaling recent changes to a route, Timers, which are used to regulate performance, Flags, which indicate whether the information about the routers has recently changed, Hold-downs used to prevent regular update messages from reinstating a route that is no longer functional, Split horizon used to prevent routing loops. A poison reverse updates used to prevent routing loops. RIP sends out routing updates at regular intervals and whenever a network topology changes occurs. And uses the following timers to regulate its performance.