Scalable link-state Internet routing

We present and verify the adaptive link-state protocol (ALP), a new link-state routing protocol that does not require the state of each link to be flooded to the entire internetwork, or to entire areas if hierarchical routing is used. A router in ALP disseminates link-state updates incrementally to its neighbors for only those links along paths used to reach destinations. Link-state updates are validated using time stamps and contain the same information used in other link-state protocols. For the case of neighbor routers connected through a broadcast medium, a designated router is distributedly elected for each link state reported over the medium, rather than requiring a designated router to report every topology change over the broadcast medium, like OSPF does. Simulation experiments illustrate that ALP is as efficient as the distributed-Bellman Ford algorithm when distances to destinations do not increase and resources do not fail, and more efficient than traditional link-state protocols based on flooding after distances increase or resources fail. ALP also outperforms the link-vector algorithm (LVA), which is the only prior routing algorithm based on selective dissemination of link states.