IP Fast Reroute techniques have been proposed for achieving fast failure recovery in just a few milliseconds. The basic idea of IP Fast Reroute is to reduce recovery time after failure by precomputing backup routes. A multiple routing configurations (MRC) algorithm has been proposed for obtaining IP Fast Reroute. MRC prepares backup configurations, which are used for finding a detour route after failure. On the other hand, requiring too many backup configurations consumes more network resources. It is necessary to recover more traffic flows with fewer backup configurations to ensure scalability. We propose a new backup configuration-creation algorithm for maximizing traffic flows which are fast recovered as much as possible under a limited number of backup configurations. The basic idea is to construct a spanning tree excluding failure links with higher link-loads in each backup configuration. We show that our algorithm has more robust on actual large IP networks.

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A backup topology design algorithm for avoiding congestion in IP Fast Reroute is presented. In IP Fast Reroute techniques, detour routes are computed by using backup topologies. Reducing the number of backup topologies is the main problem, but some links will become overloaded if the number of backup topologies is reduced. The proposed backup topology design algorithm splits the traffic on high load links to other links by considering network conditions, such as the traffic matrix or topology. The key idea of the algorithm is a new concept called the special node, which has a higher node degree in a backup topology, to handle the backup topology design problem. The effectiveness of the algorithm in terms of maximum link load reduction is quantitatively shown.

SUMMARYThis paper proposes an IP fast rerouting method which can be implemented in OpenFlow framework. While the current IP is robust, its reactive and global rerouting processes require the long recovery time against failure. On the other hand, IP fast rerouting provides a milliseconds-order recovery time by proactive and local restoration mechanism. Implementation of IP fast rerouting is not common in real systems, however; it requires the coordination of additional forwarding functions to a commercial hardware. We propose an IP fast rerouting mechanism using OpenFlow that separates control function from hardware implementation. Our mechanism does not require any extension of current forwarding hardware. On the contrary, increase of backup routes becomes main overhead of our proposal. We also embed the compression mechanism to our IP fast rerouting mechanism. We show the effectiveness of our IP fast rerouting in terms of the fast restoration and the backup routes compression effect through computer simulations.

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When a massive network disruption occurs, repair of the damaged network takes time, and the recovery process involves multiple stages. We propose a fast and traffic-balanced network recovery method that can determine an optimal recovery order of failed physical components reflecting the demand of a balance between maximizing total network flow and providing adequate logical path flows during transient recovery stages. The problem is formulated by mixed integer linear programming. The effectiveness of the proposed method was numerically evaluated, and the results show that with the proposed method, the pareto-optimal recovery order can be determined under the balance between total network flow and adequate logical path flows. In addition, the allocated minimum bandwidth of logical path is drastically improved while maximizing total network flow.