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Routing algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network.
Using this map, each router independently determines the least-cost path from itself to every other node using a standard shortest paths algorithm such as Dijkstra's algorithm. The result is a tree graph rooted at the current node, such that the path through the tree from the root to any other node is the least-cost path to that node.
Many routers execute the following overall algorithm: First, determine an approximate course for each net, often by routing on a coarse grid. This step is called global routing, [21] and may optionally include layer assignment.
In link-state routing protocols, each router possesses information about the complete network topology. Each router then independently calculates the best next hop from it for every possible destination in the network using local information of the topology. The collection of best next hops forms the routing table.
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS).
The IP forwarding algorithm is a specific implementation of routing for IP networks. In order to achieve a successful transfer of data, the algorithm uses a routing table to select a next-hop router as the next destination for a datagram. The IP address of the selected router is known as the next-hop address. [1] The IP forwarding algorithm ...
This algorithm calculates the shortest paths using the number of optical routers as the cost function. The running time using Yen's algorithm [4] is ((+ )) where is the number of edges, is the number of routers, and is the number of paths. The running time is a constant factor if the paths are precomputed.
The RIPv1 enabled router will then perform what is known as equal-cost load balancing for IP packets. [4] RIPv1 enabled routers not only request the routing tables of other routers every 30 seconds, they also listen to incoming requests from neighbouring routers and send their own routing table in turn.