Routing algorithms

A routing algorithm is a procedure that lays down the route or path to transfer data packets from source to the destination.

The Link State Routing Algorithm is a fundamental approach used in computer networks for dynamic routing. It helps routers find the shortest path to each destination by sharing information about the network's topology. Unlike the distance vector routing approach, link state routing uses a global view of the network.

Key Features of Link State Routing:

1. Global Knowledge: Each router has a complete map of the network.
2. Shortest Path First (SPF): Routers use Dijkstra's algorithm to compute the shortest path tree to all destinations.
3. Efficient Updates: Routers only share updates when there's a change in the network topology.
4. Fast Convergence: The network adapts quickly to topology changes, minimizing downtime.

Steps in Link State Routing:

Initialization:

• Each router learns about its directly connected neighbors and their link costs.
• A Link State Packet (LSP) is generated containing the router's ID, list of neighbors, and link costs.

Flooding:

• Routers flood their LSPs to all other routers in the network using a reliable flooding mechanism.
• Each router ensures it processes each LSP only once, avoiding redundant data.

Building the Link-State Database (LSDB):

• Each router collects LSPs from all routers, building a complete topology map of the network.

Shortest Path Computation:

• Using Dijkstra’s algorithm, each router calculates the shortest path to every other router in the network.

Routing Table Construction:

• Based on the shortest path tree, each router updates its routing table with the next hop for each destination.

Example: