Given the exponential growth in telecommunication networks, more and more attention is being paid to their share in the global energy consumption. Reducing networks' power consumption has become a major concern. However, the often overprovisioned wired core network is still overlooked. In core networks, pairs of routers are typically connected by multiple physical cables that form one logical bundled link participating in the intra-domain routing protocol. To reduce the energy consumption of core networks with bundled cables, the authors propose a scheme to deactivate the maximum possible number of cables, and associated equipment, while considering hose-model traffic. A similar approach has been presented for the pipe model, where the exact traffic matrix is assumed to be known. Owing to traffic uncertainty, however, it is difficult for network operators to have exact knowledge of the traffic matrix. This traffic uncertainty can be avoided by using the hose model, which specifies only the upper bounds of the egress/ingress traffic from/to a node. They introduce a mixed integer linear problem formulation that yields the optimal solution and a more practical and near optimal heuristic algorithm for large networks. The author's performance evaluation results show that it offers up to 50% power reduction.
As the Internet takes an increasingly central role in the authors communications infrastructure, the slowness of routing convergence after network failure is becoming a significant problem in the current link-state-based routing protocol. There is an alternative approach, which is to compute backup routes that allow the failure to be repaired locally by the routers that detect the failure without informing other routers of the failure immediately. Failure insensitive routing (FIR) adopts this approach, in which packet forwarding is based on not only the destination but also the link it arrives from. However, FIR faces two problems. First, a packet may travel an unnecessary path, which degrades resource utilisation efficiency. Second, FIR may fail to set a reroute path even though an active path is available. This study proposes a resilient routing scheme that avoids these two problems by enhancing FIR. It is named smart FIR (S-FIR). Upon failure, S-FIR employs a backup routing table based on the unexpected link from which a packet arrives so that subsequent packets can be forwarded to a different next hop to avoid roll back, whereas the original FIR forwards every packet based on the current working routing table. Numerical results indicate that S-FIR reduces the path length significantly, compared with the original FIR. In addition, in case of any link failure, S-FIR is proven to guarantee that any packet reaches its destination as long as there is a valid path. S-FIR provides more robust routing than FIR.
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