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Multiple Routing Configurations IP Fault-Tolerance using Multi-Topology Routing. Amund Kvalbein, Audun F. Hansen, Tarik Cicic , Stein Gjessing, and Olav Lysne 65th IETF, Dallas, TX, USA March 20 th , 2006. MRC: A Recently Proposed Recovery Scheme.
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Multiple Routing ConfigurationsIP Fault-Tolerance using Multi-Topology Routing Amund Kvalbein, Audun F. Hansen, Tarik Cicic, Stein Gjessing, and Olav Lysne 65th IETF, Dallas, TX, USA March 20th, 2006
MRC: A Recently Proposed Recovery Scheme • Guarantees single-fault tolerance for both links and nodes (100% coverage) • Supports near-instantaneous, local recovery • Need not the information on whether a link or a node has failed, even if the failed node is the egress
∞ 2 3 ∞ 1 4 6 5 Multi-Topology Routing • Main idea: use several IP topologies within an IGP cloud to achieve various TE goals: • load balancing • IPv6/Multicast • fault tolerance 2 3 1 4 6 5
MRC Design Summary • An algorithm creates backup configurations • We prohibit forwarding in parts of each backup configuration by two additional levels of link accessibility: • “isolated” links that do not carry traffic • “restricted” links that carry traffic only if no other path available • Description of forwarding functionality • [INFOCOM 2006]
Isolated link: infinite weight Isolated node: all adjacent links at least restricted (wr>|E|wmax) Combinations possible 2 3 1 4 6 5 2 3 1 4 6 5 2 3 1 4 Normal Isolated 6 5 Restricted Isolated Links and Nodes
1 2 3 4 5 6 7 8 1 2 3 1 2 3 4 5 4 5 6 7 8 6 7 8 Normal + 3 Backup Configurations 1 2 3 4 5 6 7 8 Restricted Normal Isolated
State Implications • Our research shows that only a limited number of configurations is needed, typically 3-6
Generic Forwarding Algorithm Switched configuration before? Packet arrives Yes Drop packet Normal lookup No Lookup in neighbor’s backup configuration Output link failed? Yes Failed link returned? Yes Lookup in own backup configuration No No Forward
Current Research • Load balancing • Multi-fault tolerance (SRG) • Multicast node-fault tolerance • Incremental topology changes • Loop-free convergence
MRC Summary • Guaranteed single-fault tolerance • Covers link and node failures • Need not know the root cause of failure • Rapid, local recovery • No show-stoppers so far, working on • SRG guarantees • Multihoming • Incremental changes • Multicast