The EPOC project: Energy Proportional and Opportunistic Computing system

15397International audienceWith the emergence of the Future Internet and the dawning of new IT models such as cloud computing, the usage of data centers (DC), and consequently their power consumption, increase dramatically. Besides the ecological impact, the energy consumption is a predominant criteria for DC providers since it determines the daily cost of their infrastructure. As a consequence, power management becomes one of the main challenges for DC infrastructures and more generally for large-scale distributed systems. In this paper, we present the EPOC project which focuses on optimizing the energy consumption of mono-site DCs connected to the regular electrical grid and to renewable energy sources

The potential savings of SDN compliant sub-wavelength switching as a future carrier grade solution for the metropolitan network

International audienceMetropolitan area networks are currently challenged by a sharp increase of peak traffic demands, and would thus benefit from flexible network mechanisms able to ensure excellent Quality of Service (QoS) while limiting costs. In this paper, we evaluate the gain in CAPEX and OPEX brought by Time-domain Wavelength Interleaved Network (TWIN) thanks to a dynamic control plane implemented in a Software Defined Network (SDN) framework. The SDN compliant TWIN control plane attributes resources and activates the transmitters (Tx), receivers (Rx) and transceivers (TRx) according to traffic variations. The present paper first recaps how to dimension TWIN in terms of Tx, Rx or TRx to support a given traffic matrix. It is then shown that 20\% resource over-provisioning allows to meet the metro level QoS requirements set by the MEF. Then, taking into account this over-provisioning value, a comparative study, assessing the OPEX and CAPEX savings for different configuration periods' duration (varying between 5 mn and 6 hours) is carried out. The obtained results show that the dynamic network re-configuration approach can bring some CAPEX savings and highly significant OPEX savings in a realistic metropolitan network scenario, even for rather large configuration periods (e.g. 1 hour). Finally, using a control plane based on this configuration period, the CAPEX and OPEX for TWIN are compared with those for the current Optical Circuit Switching (OCS) transport technologies (both opaque and transparent). It is shown that TWIN CAPEX/OPEX savings are important even if the TWIN's Tx/Rx/TRx unit expenditure cost is many times more expensive than that of OCS

Rapid Protection Schemes in an All-Optical Packet Metro Ring

International audienceThis study adapts the two conventional protection methods, 1+1 and 1:1, to an all-optical, time-slotted packet ring designed for metropolitan area networks. The two correspond- ing protection schemes, Premium and Regular, rely on OAM messages that can be carried in each time slot. Each scheme offers packet level protection and maintains a congestion free and simple recovery mechanism in case of single failure. The upper bound for failure recovery time is very low as it is limited to the ring cycle time, which is about 2ms (much less than the 50ms SDH recovery time). The results suggest two very robust and efficient protection methods. In premium method network experiences no loss, whereas the loss period for Regular traffic is limited to a portion of the Round Trip Time. Preliminary dimensioning results are obtained under the assumption that the ring is dimensioned to support a single link failure. The difference between resources for Premium and Regular schemes depends on the traffic matrix and may be negligible for the very common concentration/distribution scenario. In the uniform traffic case, the cost of a dual ring with Regular protection is shown to be very close to the cost of a single, unprotected ring

Resilience in Transparent OPS Multi-Rings

International audienceThis paper presents a resilient multi-ring network architecture based on the ECOFRAME technology. Each ring network is made of two unidirectional transparent WDM optical packet switched rings, each with a separate control channel synchronized with one or several data channels. Two rings networks are interconnected by two adjacent nodes in order to ensure resilience. Such a multi-ring network is a good candidate for replacing the current SDH multi-ring metro networks as it presents many features of a Transport Network. Contrarily to existing Ethernet rings or RPR networks, it is fully optically transparent within one ring, and may not access the client layer at interconnecting nodes, which allows provisioning client layers only at the edges of this network. A multi-class label-based MAC is proposed, and resilience mechanisms for both unicast and multicast transport are proposed

Reliable Multicast on a WDM Optical Packet Ring

International audienceThe present paper addresses multicast protection in WDM Optical Packet Rings that are currently considered for future metro network architectures. The considered architecture is optically transparent for transit traffic, which drastically limits the number of OEO conversions compared to e.g. Ethernet Packet Rings. WDM Optical Packet Rings offer huge capacity while still retaining a packet based granularity, which is not the case for ROADM based networks. Metro networks now support multicast, as IPTV services are largely deployed. Two alternate methods for implementing the traditional 1+1 and 1:1 protection mechanisms are proposed. Both rely on using the time slotted control channel to deliver failure and recovery information. The performance of the two methods are thoroughly assessed and it is shown that the transient degradation durations are always bounded by the Ring Round Trip Time, which is at least an order of magnitude less than the usual 50ms target time for protection. Moreover, using a Multicast Drop-off Middle Point is shown to provide an almost loss free transport in case of single failure. Lastly the single ring protection schemes are extended to multi-ring architectures, relying on an MPLS-TP compatible operation mode of the WDM optical packet rings

CAPEX and OPEX Saving in SDN-Compliant Sub-Wavelength Switching Solution

International audienceThe present paper attempts to answer the question "is it worth implementing dynamic resource allocation in a metropolitan network ?". Our study evaluates the gain (CAPEX and OPEX) to expect in a Time-Domain Wavelength Interleaved Network (TWIN) when the number of active Tx/Rx changes, over the day, according to the traffic matrix. We assume that TWIN is implemented in an SDN framework in which burst emission schedules can be periodically recomputed thus taking into account traffic matrix changes. A comparative study is carried out to assess, for different values of the computation period, the OPEX and CAPEX savings on the basis of the number of active Tx/Rx. Results show that such a dynamic network reconfiguration approach can bring some CAPEX savings and more significant OPEX savings in a realistic metropolitan network scenario, even for rather large configuration periods

Fully transparent design of a hybrid optical packet/circuit metropolitan area network

International audienceWe present a new method to design a regional network based on optical hybrid packet and circuit switching. Our approach aims at providing packet-level grooming only where it is profitable. The method relies on splitting the original traffic matrix in two parts, which will be transported either through optical packets or through circuits, according to a maximum wavelength capacity threshold. The network dimensioning can be then performed for circuit and packet traffic matrices separately. As the circuit WDM network design problem is well documented, we put the emphasis on the optical packet network dimensioning. This later is performed in the context of Packet OADM (POADM) technology, involving fast tuneable emitters and receivers dedicated to specific wavelengths. First, candidate sets of rings are identified. Then, the resources needed for each ring of a given set are evaluated by taking into account both receiver and wavelength costs. The "wavelength cost" depends on the considered ring, as it is proportional to its circumference. A linear programing formulation, previously established for unidirectional rings, is adapted to bi-directional ones with shortest distance routing and 1+1 protection. The proposed method is applied to a 7 nodes network by considering different scenarios in terms of content-delivery node positions, wavelength capacity threshold or network geographical extension. Even if most of the traffic is carried by circuits, POADM technology is widely used as a grooming technique across the network. The benefits of using POADM technology are achieved without necessitating O/E/O conversions at packet ring interconnections and alleviating inter-ring synchronization issues, resulting in a fully transparent network

The Cost of Traffic Protection in Bidirectional Optical Packet Switching Rings

International audienceIn this paper we present a method for optimal planning of bidirectional optical packet-switched rings, with synchronized work of ring stations and an out-of-band control channel. The network stations are equipped with tunable transmitters and fixed single-wavelength receivers that can be shared by different destinations and without a limit on their number per destination. Optimal planning method that is proposed here is based on linear programming, and provides an optimal network design with minimum transportation cost per network link and receiver, for the preferred method of traffic protection. We considered 1+1 protection ("premium"), which consist in doubling the capacity of each operational connection in the ring and 1:N protection ("regular"), in which the protection capacity is shared between multiple connections, as it is not supposed to be used until an unwanted event, i.e., a failure in the network. Enabling protection in such packet ring is a novel problem and here is solved for the first time, to the best authors' knowledge. By detailed simulations we studied the impact of different protection models on the cost of the network and its configuration, and the mutual interaction between protection methods and their effectiveness. The results suggest that the cost of premium protection is up to 40 % higher than the price of regular protection, and even up to 60 % higher than the cost of the network without any protection

An optical packet metro architecture for Fixed Mobile Convergence in the cloud era

International audienceThe present paper addresses future network architectures considered for Fixed Mobile Convergence, where users can access resources transparently either through fixed access technologies or through the mobile RAN. Optical technologies rely on Wavelength Division Multiplexing (WDM) to meet continuously growing bandwidth demands. However, although in the core network optical circuit switching may efficiently support huge traffic aggregates, closer to the access, in future Metropolitan Area Networks (MAN), it is necessary to provide a finer granularity, and a dynamical bandwidth control, to very heterogeneous traffic demands. This is supported by Optical Packet Switching (OPS) relying on WDM slotted Add/Drop Multiplexing (WSADM). A flow-based transfer mode, compatible with SDN control is first specified, and applied to bi-directional MAN rings. This mode is shown to provide several methods for supporting both local and global repair in case of failure. Mathematical models are derived to assess optical packet insertion performance and are used to illustrate how WSADM rings can support MAN performance requirements. Lastly the impact of locating the IP edge, and Data Centres closer to the users than in legacy architectures, within the MAN is addressed

Scheduling Aware Dimensioning for Time-Domain Wavelength Interleaved Network

International audienceIn this paper, we present a novel approach for resource provisioning in Time-Domain Wavelength Interleaved Network (TWIN), an optical burst switching solution available for transport in regional networks, with nodes equipped with transponders composed of a fast tunable transmitter and a fixed-wavelength receiver. The approach consist in allocating the number of transponders to satisfy the traffic demand, providing at the same time an optimal slot schedule for the transport of optical bursts. Apart from calculating the optimal schedule, the solution also allocates the additional slots to sources, in order to improve the level of QoS latency experienced by individual network flows during the pre-insertion queueing process. This functionality is achieved by original QoS constraints. The dimensioning method is optimal, formulated as Mixed Integer Linear Program (MILP), and it allows a trade-off between the amount of network resources allocated and the QoS performances of the optimal solution. By simulations we studied the impact of the proposed dimensioning solution on the network performances and the total network capacity achievable by TWIN.We show that our proposed latency constraint mechanism leads to insertion latency limited to few time slots only at no additional network resource cost, in a 6- node mesh network. We also show that non-uniform network traffic decreases TWIN capacity efficiency (i.e., wastes resources) compared with deterministic traffic