The Control Plane: Link State Routing
Explore the concepts of link state routing including neighbor discovery with HELLO messages, reliable flooding of link state packets, and how routers handle link and router failures to maintain accurate network topology.
-Another way to create a routing table with the most efficient path between two routers or ‘nodes’ is by using link-state routing.
Link state routing works in two phases: reliable flooding and route calculation. Let’s look at phase I now.
Phase I: Reliable Flooding
Neighbor Discovery
When a link-state router boots, it first needs to discover its neighbors. To do this:
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Each router sends a HELLO message every seconds on all of its interfaces. This message contains the router’s unique address.
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As its neighboring routers also send HELLO messages, the router discovers its neighbors.
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These HELLO messages are only sent to neighbors that are directly connected to a router, and a router never forwards the HELLO messages that they receive.
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HELLO messages are also used to detect link and router failures. A link is considered to have failed if no HELLO ...