• Suppose there is a centra authority in charge of routing in an AS
  • It is called a controller
  • Routers do not make routing decisions
• If so, how would it interact with routers for intra-AS routing.

considerations

• Routing decisions are made by the controller
• How is a routing decision given to routers?
• How are costs of links given to the controller?

The routing controller queries all the routers and builds a network graph. It then computes optimum paths for all possible destinations and builds forwarding tables for each node and updates their table. Border Gateways advertise all their connected networks as possible routes.