Computer Networks · M2 · papers

Q3B · How OSPF chooses a path

Re-exam · 4 February 2026

Actual TEE paper · current-M2 matching parts; original marks

Actual PYQ. Summarize how OSPF determines the best path to a destination network. [5 marks]

Answer

Swipe across the diagram to read its labels ↔
Link-state routing: from local links to a shortest-path tree
Diagram: Link-state routing: from local links to a shortest-path tree. Labels: Link-state routing: from local links to a shortest-path tree | Link-state routing: from local links to a shortest-path tree | 1. Discover neighbours and costs | Each router measures or configures its local link information. | 2. Flood link-state information | Routers share topology information within the routing scope. | 3. Maintain the topology database | New information updates the shared view after convergence. | 4. Run Dijkstra from this router | Add link costs; install the resulting next hops.
Build the topology, then calculate the route.
  1. Discover/maintain neighbours and determine local link costs.
  2. Exchange link-state information and synchronize the database within the appropriate area.
  3. Run Dijkstra’s shortest-path algorithm with the current router as the root.
  4. Add outgoing link costs along candidate paths and select minimum-cost routes.
  5. Install next-hop information; recalculate when relevant topology information changes.