Open Shortest Path First (OSPF)

Open Shortest Path First (RFC 2328)
• Interior gateway protocol (so withinAutonomous Systems (AS, Networking))
• Shortest path calculation:
• Link State Routing
• Dijkstra’s Shortest Path Algorithm (Networking), RIP to calculate routing table
• Features:
• Multiple distance metrics
• Dynamic
• QoS
• Load Balancing
• Hierarchical (supports Areas – next slide)
• CIDR support

OSPF Hierarchical routing
• Supports an abstraction called Areas
• Allows for a AS to be further subdivided into areas
• Routers within an Area exchange routing information
with each other
• Routers external to Area only share routing
information with Area edge routers
• Allows for hierarchical routing within an AS