Abstract-This paper reports on a novel ring-based data center architecture composed of multidimensional switching nodes. The nodes are interconnected with multicore fibers and can provide switching in three different physical, hierarchically overlaid dimensions (space, wavelength and time). The proposed architecture allows for scaling in different dimensions while at the same time providing support for connections with different granularity. The ring topology reduces the number of different physical links required, leading to simplified cabling and easier link management, while optical bypass holds the prospect of low latency and low power consumption. The performance of the multidimensional switching nodes has been investigated in an experimental demonstration comprising three network nodes connected with multicore fibers. Both high capacity wavelength connections and time-shared subwavelength connections have been established for connecting different nodes by switching in different physical dimensions. Error-free performance (BER<10 -9 ) has been achieved for all the connections with various granularity in all the investigated switching scenarios. The scalability of the system has been studied by increasing the transmission capacity to 1 Tbit/s/core equivalent to 7 Tbit/s total throughput in a single 7-core multicore fiber. The error-free performance (BER<10 -9 ) for all the connections confirms that the proposed architecture can meet the existing demands in data centers and accommodate the future traffic growth.Index Terms-Data center networks, optical switching, space division multiplexing, wavelength division multiplexing, time division multiplexing. This work was supported by the ECFP7 grant no. 619572, COSIGN and Innovations Fonden grant 0603-00514B, E-SPACE. We would like to thank OFS for fabricating and providing the spliced fan-in/fan-out multicore fiber and Polatis for providing the 48x48 beam-steering fiber switch.
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Our society nowadays is governed by complex networks, examples being the power grids, telecommunication networks, biological networks, and social networks. It has become of paramount importance to understand and characterize the dynamic events (e.g. failures) that might happen in these complex networks. For this reason, in this paper, we propose two measures to evaluate the vulnerability of complex networks in two different dynamic multiple failure scenarios: epidemic-like and cascading failures. Firstly, we present epidemic survivability (ES), a new network measure that describes the vulnerability of each node of a network under a specific epidemic intensity. Secondly, we propose cascading survivability (CS), which characterizes how potentially injurious a node is according to a cascading failure scenario. Then, we show that by using the distribution of values obtained from ES and CS it is possible to describe the vulnerability of a given network. We consider a set of 17 different complex networks to illustrate the suitability of our proposals. Lastly, results reveal that distinct types of complex networks might react differently under the same multiple failure scenario.
Abstract-This paper presents a successful test-bed implementation of a multi-vendor transport network interconnection via open WDM interfaces. The concept of applying Alien Wavelengths (AWs) for network expansion was successfully illustrated via deployment of multi-domain/multi-vendor end-to-end OTN services. We evaluate the impact of AW service establishment on both native and other alien services. Our experience confirms the technical feasibility of the concept in the context of transparent network-to-network interconnection at the optical layer. Furthermore, main operational challenges are discussed.
In this paper, routing optimizations based on energy sources are proposed in dynamic GMPLS controlled optical networks. The influences of re-routing and load balancing factors on the algorithm are evaluated, with a focus on different re-routing thresholds. Results from dynamic network simulations show that re-routing strategies can lower CO 2 emissions compared to the basic energy source routing scheme, and a lower re-routing threshold achieves more savings. The increased blocking probability brought by using re-routing schemes can be compensated by applying load balancing criteria. A trade-off between blocking probability and obtained CO 2 savings is studied. Keywords: GMPLS, optical networks, energy-efficient, re-routing. INTRODUCTIONWith the rapid growth of the network bandwidth demand in the past years, concerns have arisen due to the accompanied growing energy consumption. The network components (routers, transponders, ROADMs, amplifiers, etc.) are becoming significant contributors to the greenhouse gas emissions. As an example, a 1 kW router powered by a coal power plant can contribute to 8.6 tons of CO 2 emissions per year [1]. Thus, if the network traffic can be monitored to go through green routes (routes which use green energy sources such as wind or solar), the CO 2 emissions can be greatly reduced. The recent development in Smart Grid technology has made it possible to select the type of energy sources (solar, wind, fuel, coal, etc.) used for network components, and some research has been done to employ green energy sources to reduce the network energy consumption, as in [2][3] [4]. Ideas regarding re-routing strategies are also mentioned in [5], where the author focuses on turning off links in the network. The results are given in a static environment. Similar work done in [6] also aims at turning off unused links. However, the majority of the work done in the optical networking field is for a static network environment, with time-consuming optimization methods, such as linear programming. In this paper, a pure energy source aware (ESA) routing algorithm (routing decision based on the path with most green energy sources) is implemented to solve such issues in Generalized Multi-protocol Label Switching (GMPLS) [7] controlled dynamic optical core networks. Open Shortest Path First -Traffic Engineering (OSPF-TE) [8] is used as routing protocol, and Resource Reservation Protocol -Traffic Engineering (RSVP-TE) [9] is used as signalling protocol. In the considered environment, it is difficult to use the traditional optimization methods for improving the sub-optimal results, due to the unpredictability of the traffic pattern, the dynamically changing energy sources and the need for a fast convergence routing protocol. In this paper, besides presenting the results of ESA routing algorithm, with randomly changing energy sources (green and dirty), several optimization criteria are exploited under different energy source changing intervals, such as applying re-routing policies when a energy source has ...
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