Question

Which routing algorithm requires each router to inform all other routers in the network about its entire set of links and their current costs?

• A. Distance Vector Routing
• B. Link State Routing
• C. Path Vector Routing
• D. Flooding

Hint:

Key difference: Distance Vector tells neighbors about the world. Link State tells the whole world about its local neighbors.

Answer 1

The Correct Option is B

Concept:
Routing protocols are classified by how they discover the network topology. Link State routing is a sophisticated approach where every router possesses a complete and identical map of the entire network's connectivity.

Step 1: The "Link State Advertisement" (LSA) process.
In this algorithm, each router identifies its direct neighbors and the cost (delay, bandwidth, etc.) of the links connecting to them. It then creates a packet called a Link State Packet (LSP) and "floods" it to every other router in the network. Unlike Distance Vector, it doesn't just talk to neighbors; it informs the whole network about its local status.

Step 2: Building the Topology Database.
Once a router receives LSPs from every other router, it assembles them into a comprehensive Link State Database (LSDB). This database acts as a full "road map" of the network. Every router in a Link State area has the exact same database.

Step 3: Calculating the Best Path.
After the map is built, each router independently runs Dijkstra's Shortest Path First (SPF) algorithm. It places itself at the "root" and calculates the least-cost path to every other node. This makes Link State protocols like OSPF very fast to converge and free from the routing loops common in Distance Vector protocols.