Divanilson R. Campelo

Sleep Mode for Energy Saving PONs: Advantages and Drawbacks

A common approach to reduce energy consumption in communication networks is to allow network elements to switch to sleep mode. While this technique has been widely utilized in wireless networks, recent studies have proposed to exploit sleep mode in wired networks to conserve energy as well. This paper focuses on some feasible implementations of sleep mode in passive optical networks (PONs). In particular, ONU sleep mode is considered. The paper first outlines the ONU wake-up process using current time division multiplexing (TDM) PON protocols. Current and novel optical network unit (ONU) architectures that selectively switch-off some elements are then described. Their advantages in terms of energy savings are analytically computed under different traffic scenarios. Using the proposed architectures, analytical results show more than 50% energy saving under realistic TDM traffic. Finally, possible drawbacks in terms of new scheduling challenges are also discussed and potential solutions are presented.

Energy Management Mechanism for Ethernet Passive Optical Networks (EPONs)

In the past few years, Ethernet Passive Optical Networks (EPONs) have rapidly gained large popularity in broadband access networks. However the current standard has no management protocols aiming at reducing power consumption. In this paper, we propose an Energy Management Mechanism (EMM) within the IEEE 802.3ah control scheme. The main idea is to switch Optical Network Units (ONUs) to sleep mode and determine a suitable wakeup time schedule at the Optical Line Terminal (OLT). In the proposed EMM there is a trade-off between maximizing the power saving and guaranteeing the network performance. We compare two types of downstream scheduling schemes, Upstream Centric Scheduling (UCS) and Downstream Centric Scheduling (DCS), which are different in the way they assign active and sleep states to ONUs. Simulation results in terms of energy consumption and queuing delay are shown for the EMM based EPON system.

Energy efficiency in passive optical networks: where, when, and how?

This article provides an overview of current efforts in reducing energy consumption in passive optical access networks. Both ITU-T and IEEE standardized PONs are considered. The current solutions proposed by standardization authorities, industry, and academia are classified based on the layer they address in the standardized architectures: physical layer, data link layer, and hybrid. Then, the article provides answers to major questions, such as where, when, and how to reduce PON energy consumption in TDM PONs by means of a quantitative evaluation. Results show that to reduce energy consumption, ONUs must be provided with physical devices that are not only power-efficient but also provide improved services (e.g., fast synchronization) to upper layers. For this latter purpose, novel physical ONU architectures are proposed to speed up the synchronization process and enable effective data link layer solutions. Finally, the feasibility of switching ONUs to low power mode in idle slots is assessed through a testbed implementation.

The watchful sleep mode: a new standard for energy efficiency in future access networks

The continuously increasing consumption of power to access the Internet has been a major concern for network operators and equipment vendors. Passive optical network (PON) systems are widely seen as the future of broadband access. In 2010, ITU-T standardized a protocol-based PON energy efficiency mechanism that is comprised of two main modes, the doze mode and the cyclic sleep mode, which promise to save significant amounts of energy. However, the use of these two standardized alternative modes requires extra signaling and wastes energy. In this article we present the watchful sleep mode, a new mode that unifies the doze and cyclic sleep modes into a single power management mode. The new mode eliminates the extra control signaling and maximizes the amount of energy saved by keeping only the necessary hardware ON. Recently, the watchful sleep mode has been included in the ITU-T G.984 (G-PON) and ITUT G.987 (XG-PON) recommendations. It is expected to be operated as the only power management mode in future PON systems.

Grid Reconfigurable Optical-Wireless Architecture for Large Scale Municipal Mesh Access Network

This paper presents a novel hierarchical and grid based reconfigurable optical-wireless network (GROW-Net) architecture. GROW-Net supports scalable and flexible integration of a large scale wireless mesh network in a municipal environment. Under the GROW-Net architecture, a joint evolution strategy is proposed to allow graceful upgrades in both optical backbone and wireless mesh network. To alleviate the known throughput bottleneck in mesh networks, a capacity enhancing technique based on flexible cell-splitting is proposed. The technique allocates wavelength resources to unutilized dark fibers using the unique structure of GROWNets reconfigurable and colorless access gateways. To analyze the effectiveness of the approach, throughput performance of the wireless mesh network is analyzed using a high fidelity simulator. The wireless mesh network in the simulation employs a distributed and cooperative medium access control protocol within a time division multiple access and time division duplex framework. Through the high fidelity simulation, results show the degree of throughput enhancement by using cell splitting method. The evolution strategy further enables the backbone to scale its bandwidth and adapt to future high throughput and very high throughput wireless technologies. The performance of the proposed backbone is demonstrated experimentally over the optical testbed.

A robust SDN network architecture for service providers

Large scale networks, such as those deployed by Service Providers (SPs), employ robust architectures, capable of supporting large volumes of traffic with very different characteristics. Their network equipment has significant processing load, being responsible for building both a routing logic and the routing of traffic itself. By having the network control implemented in a distributed manner and being built with a limited number of vendors, these networks have limitations of control and traffic engineering, hindering the differentiation among SPs. Additionally, the network intelligence is hidden in the network equipment, making innovations very slow and conditioned to the vendors interests. As an alternative option, this work proposes a Software Defined Networking (SDN)-OpenFlow network architecture that attempts to improve the previously mentioned problems, and, at the same time, to solve the arising difficulties related to the SDN network centralized feature. With the proposed architecture, a robust SP SDN-OpenFlow network is created to support high controller response times and controller outages, without additional delays in the creation of flows and with significant reduction of the controller load. A prototype has been built using Open vSwitch as a virtualization software for OpenFlow clients, Mininet for the topology construction and Ryu as the controller, all with OpenFlow 1.3 support. The obtained results are general and can be extended to other types of networks.

Energy efficiency analysis of the Watchful Sleep mode in next-generation passive optical networks

Energy efficiency has become a salient element in the design and operation of modern telecommunications networks. To support energy efficiency in passive optical network (PON) systems, the ITU-T has recently standardized a new power management technique, namely the Watchful Sleep mode, which unifies the two previously standardized techniques (i.e., Doze and Cyclic Sleep modes). The new mode can emulate each of the Doze and Cyclic modes, and it outperforms them in terms of energy efficiency and reduced network signaling. In this paper, we present the first analytical model for numerically measure the performance of the Watchful Sleep mode. Specifically, the new model estimates the ONUs energy efficiency under different network scenarios given a set of quality-of-service constraints. To validate our model, we perform comparisons with simulation results. These comparisons demonstrate that the proposed model can accurately capture the energy efficiency of PON systems.

Connected OFCity: Technology innovations for a smart city project [Invited]

Around the world, municipalities have been making substantial investments into broadband access infrastructure to accelerate the build-out of an urban phenomenon that has become known as a smart or connected city. At the 2016 Optical Fiber Communications Conference, a team contest, the Connected OFCity Challenge, was held to discuss the technological innovations and to examine dependencies and intricacies of a connected city project. The participants, four teams of experts coming from a cross-section of the industry, presented and defended their visions of future applications and innovative architecture and technologies to realize the interconnection. This paper provides a synthesis of the four competitive proposals offered for the contest and their ensuing discussions.

An Efficient IA-RMLSA Algorithm for Transparent Elastic Optical Networks

Abstract This paper proposes a new Routing, Modulation Level and Spectrum Assignment (RMLSA) algorithm that considers the effects of physical layer in transparent elastic optical networks. The goal of the algorithm is to reduce the circuit blocking probability caused by the transmission quality degradation in the establishment of new circuits. The proposed algorithm is compared with two other Impairment-Aware RMLSA (IA-RMLSA) algorithms: Modified Dijkstra Path Computation (MD-PC) and K-Shortest Path Computation (KS-PC). The IA-RMLSA algorithms are evaluated under three different composition of bandwidth request for EON and NSFNet network topologies. Besides, we also evaluated the performance of IA-RMLSA algorithms using First-Fit and Best-Fit to spectrum assignment. Simulation results show that the proposed algorithm exhibits better performance than the MD-PC and KS-PC algorithms with regard to i) the circuit blocking probability, ii) the bandwidth blocking probability, iii) the fairness of service to different source-destination pairs, and iv) the fairness of service to different bandwidths. In general, regarding the circuit blocking probability, our algorithm achieved the best performance working with First-Fit (FF). Our algorithm using the FF has a minimum gain of 78.10% and 55.75% compared to the KS-PC-FF and MD-PC-FF algorithms, respectively, when the network attends 7 different values of bandwidth. Regarding the bandwidth blocking probability, the proposed algorithm using the FF has a minimum gain of 71.96% and 41.89% compared to the KS-PC-FF and MD-PC-FF algorithms, respectively. In general, regarding fairness, the proposed algorithm exhibits superior performance compared to the KS-PC and MD-PC algorithms.

An efficient architecture for dynamic middlebox policy enforcement in SDN networks

Abstract Middleboxes are widely deployed devices that play crucial roles in today’s networks. Their behavior is commonly determined by policies that are manually set by network administrators, what may be a burden for networks whose connectivity dynamically changes. Recently, with the advent of Software-Defined Networking (SDN), a number of possibilities for handling middlebox policy enforcement have emerged. Even though there have been some contributions in this area, none of them eliminate the necessity of manual configuration of middleboxes for policy enforcement. In this paper, we propose an SDN-based architecture for dynamic middlebox policy enforcement that is able to respond to network events without any manual intervention from the network administrator. The architecture is also based on an interface proposed in this paper that enables the communication between an SDN controller and any middlebox. To evaluate the policy enforcement architecture, a prototype with two types of middleboxes, a firewall and an Intrusion Prevention System (IPS), was implemented in a virtual machine. Hypothesis tests were performed in order to validate the experimental results obtained with the prototype. Results show that the architecture is able to dynamically enforce middlebox policies, allowing network applications to run appropriately with no impact on network performance.