In a scenario of restoration from massive failures, a network is repaired through multiple restoration stages because availability of repair resources is limited. In a practical case, a network operator should assure the reachability of important traffic in transient stages, even as risks and/or operational overheads caused by stage transitions are suppressed. We discuss the novel problem of optimizing both traffic recovery ratio and transition risks caused by paths switching operation. We formulate our problem as linear programming, and show that it obtains pareto-optimal solutions of traffic recovery versus transition risks. We also propose a heuristic algorithm for applying networks consisting of a few hundred nodes, and it could produce sub-optimal solutions within 4% difference from optimal solutions.

Content transfer, e.g. video transfer, is now becoming major traffic in the current Internet. Content transfer originally has a content oriented feature of “wherever content is retrieved, users only take care of what content they obtain”. Conventional traffic engineering aims to obtain optimal routes for traffic between ingress and egress router pairs, which has “location oriented feature, i.e. where to connect”. With content oriented feature of user demand for content traffic, traffic engineering can be changed towards content oriented routing design. In this paper, we propose a novel content oriented traffic engineering, named CAR (Content Aware Routing). In CAR, routes are designed for content and egress router pair, i.e. content traffic towards a receiver-side router. Content demand can be flexibly distributed to multiple servers(repositories) providing the same content, which means content can be obtained from anywhere. With numerical examples by linear programming formulation, we comparatively evaluate CAR with comparing with combination of CDN and traffic engineering, i.e. location oriented designs. Numerical results show that CAR improves maximum link utilization significantly with slight increase of network resource usage.

We constructed a rack-mounted prototype photonic ATM switch based on the FRONTIERNET architecture. The advantages of the architecture are that its output-buffering scheme overcomes the bottlenecks that can occur when receiving and storing concurrent high-speed cells, and that there is no need to deal with contention resolution between input highways. The prototype has 16 input/output ports and 2.5 Gb/s transmission speed. Actually, six input ports and one output port are mounted in two racks. We demonstrated successful cell routing and buffering, and its stable operation, with 24-h bit-error-free switching operation. We also discussed problems to be solved in increasing the throughput of FRONTIERNET.

This paper describes large-capacity photonic ATM switching systems being developed that use FDM (or WDM) techniques. Our system is based on a simple star architecture with a modular structure. We show that it is possible to obtain a 320-Gb/s system that has enough S/N margin and can tolerate the polarization and frequency dependencies of optical devices. Our experiments using rack-mounted prototype modules to demonstrate the feasibility of our system, as well as successful 10-Gb/s 4/spl times/4 broadcast-and-select and 2.5-Gb/s 16/spl times/16 frequency-routing switch operations.