An Extended Fault-Tolerant Link-State Routing Protocol in the Internet

Link state routing protocols such as OSPF and IS IS are widely used in the Internet today In link state routing protocols global network topology information is rst collected at each node A shortest path tree SPT is then constructed by applying the Dijkstra s shortest path algorithm at each node Link state protocols usually require the ooding of new information to the entire sub network after changes in any link state including link faults Narvaez et al proposed a fault tolerant link state routing protocol without ooding The idea is to construct a shortest restoration path for each uni directional link fault Faulty link information is distributed only to the nodes in the restoration path and only one restoration path is constructed It is shown that this approach is loop free However the Narvaez approach is ine cient when a link failure is bi directional because a restoration path is uni directional and routing tables of nodes in the path are partially updated In addition two restoration paths may be generated for each bi directional link fault In this paper we extend the Narvaez protocol to e ciently handle a bi directional link fault by making the restoration path bi directional Several desirable properties of the proposed extended routing protocol are also explored A simulation study is conducted to compare the traditional link state protocol the source tree protocol the Narvaez uni directional restoration path protocol and the proposed bi directional restoration path protocol