OSPF is a link-state routing protoocol which uses factors such as speed or the link’s shortest path to decide which route is the best.
Link state protocol routers maintain a common picture of the network and exchange link informantion during discovery and/or network changes.
OSPF is designed for large and scalable networks, becauses of the following advantages:
- Convergence speed
- OSPF sends only routing changes instead of the entire routing table. Because of the small routing changes, updates are flooded rapidly across the network
- Support for VLSM
- Network size
- Use of bandwidth
- OSPF uses multicast to advertertise the updates: LSU’s (link state updates) are small in packetsize
- path selection
- OSPF selects optimal routes using cost instead of hopcount (RIP)
- Member groupings
- OSPF uses areas: every network segment is cut into smaller areas of routers: less LSU’s are sent out and more efficient routing takes place. eh Every router in a area does have the same topology table.