Facing the Reality: Validation of Energy Saving Mechanisms on a Testbed

Two energy saving approaches, called Fixed Upper Fixed Lower (FUFL) and Dynamic Upper Fixed Lower (DUFL), switching off idle optical Gigabit Ethernet (GbE) interfaces during low traffic periods, have been implemented on a testbed. We show on a simple network scenario that energy can be saved using off-the-shelf equipment not explicitly designed for dynamic on/off operation. No packet loss is experienced in our experiments. We indicate the need for faster access to routers in order to perform the reconfiguration. This is particularly important for the more sophisticated energy saving approaches such as DUFL, since FUFL can be implemented locally

Facing the Reality: Validation of Energy Saving Mechanisms on a Testbed

Two energy saving approaches, called Fixed Upper Fixed Lower (FUFL) and Dynamic Upper Fixed Lower (DUFL), switching off idle optical Gigabit Ethernet (GbE) interfaces during low traffic periods, have been implemented on a testbed. We show on a simple network scenario that energy can be saved using off-the-shelf equipment not explicitly designed for dynamic on/off operation. No packet loss is experienced in our experiments. We indicate the need for faster access to routers in order to perform the reconfiguration. This is particularly important for the more sophisticated energy saving approaches such as DUFL, since FUFL can be implemented locally

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Energy Saving in IP over WDM Backbone Networks

The energy consumption of the Internet is exploding due to the increase of the number of devices connected to it as well as the increase of traffic volume that is estimated in about 50% per year fuelled by mobile data and video applications; consequently, it is crucial to improve network efficiency to prevent the Internet from being throttled by an energy bottleneck. This PhD dissertation deals with the energy efficiency of telecommunication networks and specifically faces the problem of saving energy in the backbone section of the network. The main contributions concern the definition of algorithms and mechanisms that integrate and exploit the knowledge of the network topology, the carried traffic and the power behaviour of network devices to achieve energy efficiency in the network. Three novel contributions are presented which are related to three different saving strategies. The first faced problem concerns the design of energy efficient virtual topologies in two-layers IP over WDM networks. The problem is formalized as a Mixed Integer Linear Programming (MILP) problem and a novel heuristic algorithm, named Start-Single Hop and ReRoute, is proposed and compared with the optimal solution and another heuristic solution proposed in the literature. Results obtained through extended simulations demonstrate that the proposed solution is able to reduce the network energy consumption with respect to other solutions and to perform close to the optimal solution. Another key aspect faced in the dissertation is related to the possibility of saving energy in presence of variable traffic exploiting traffic engineering strategies that aim at aggregating the traffic on a subset of network elements in order to put in sleeping unused devices. Concerning this point, an Energy Aware Traffic Engineering mechanism, named DAISIES, is proposed. Besides achieving good level of energy efficiency, the proposed solution overcome many practical issues rising from the adaptation of link switch-off mechanism, such as packet loss, out-of-order packet delivering and routing instabilities. The last faced problem concerns the energy efficiency of the optical network layer. In this area a two different solutions are proposed. The first one is based on an iterative greedy algorithm that a posteriori tries to aggregate lightpaths on a subset of optical fibres links, re-optimizing the network when the traffic decreases. The second one, instead, directly works on lightpaths provisioning, exploiting a Power Aware Routing and Wavelength Assignment (PA-RWA) algorithm that tries to set up lightpaths in such a way that the total consumed energy is minimized. Specifically, the performance of the proposed PA-RWA algorithm is evaluated and compared with other solutions proposed in the literature showing better performance both in terms of energy efficiency and blocking probability. In summary, this dissertation makes important contributions to the networking research community providing new methods and approaches for the definition of energy efficient networking techniques

Distributed and adaptive interface switch off for Internet energy saving

This work proposes a distributed and adaptive mechanism for saving energy in IP/MPLS over WDM networks by switching off router line cards according to the traffic variability in the network. The proposed mechanism optimizes the traffic routing and adapts the IP topology to the traffic that is actually carried in the network. This is done by re-computing the path of each traffic flow several times during a day when their requested capacity changes. The routing is performed by using a specific cost function, named V-Like, to compute link weights into the shortest path routing algorithm. The proposed solution is compared with a static energy-aware heuristic algorithm proposed in the literature; results show that it is possible to save from 35% up to 50% of energy with respect to the static case, depending on the traffic load. © 2011 IEEE

Dynamic Power-Aware Routing and Wavelength Assignment for Green WDM Optical Networks

This paper proposes a novel power-aware routing and wavelength assignment (PA-RWA) algorithm to be applied to a transparent wavelength division multiplexing (WDM) optical network. The proposed algorithm aims at improving the energy efficiency of the optical network by leaving unused optical fibres as much as possible in order to minimize the number of optical amplifiers kept active in the network. A dynamic lightpath establishment scenario is considered and results are compared with other routing algorithms showing that the proposed algorithm can drastically reduce the power consumption for any value of traffic load

Impact of Energy-Aware Topology Design and Adaptive Routing at Different Layers in IP over WDM networks

As the Internet expands in terms of users and exchanged traffic, its energy consumption is becoming a very important issue; in particular, the energy consumption of core networks is expected to be the most critical aspect in coming years. Different strategies and many solutions have been proposed in the last years to improve the energy efficiency of core networks. Specifically, three different strategies can be mainly distinguished: i) the Energy Minimized Virtual Topology Design (EM-VTD), which aims at designing the IP layer topology minimizing the peak power consumption of the network; ii) the Energy Aware Traffic Engineering (EA-TE), which acts on the traffic routing at the IP layer and aims at bringing the power consumption of the network nearly proportional to the actual offered load; iii) the Power Aware Routing and Wavelength Assignment (PA-RWA), which instead acts on the traffic routing at the optical layer. The present study considers these three energy saving strategies, adopting a specific solution for each of them, and evaluates the impact that each of them has on the power consumption of the whole network, considering both the IP and the WDM layers. Results show that a good design of the IP topology is a key aspect to improve the energy efficiency of the network with respect to other simpler strategies (e.g. the end-to-end or the link-by-link grooming strategy). Moreover, the combined use of adaptive routing solutions at both the IP and the WDM layers allows to achieve a better comprehensive power saving in any traffic load conditions, with IP-specific solutions being more important when the total traffic offered to the network grows. © 2012 IEEE

Energy-efficient routing and wavelength assignment in translucent optical networks

We study the energy-efficient routing and wavelength assignment (RWA) problem in translucent WDM networks, taking into account transmission limits of optical signals and the consequent need for signal regeneration. The problem is formulated through an integer linear programming model, and a heuristic algorithm called least regeneration first (LRF) is proposed to solve it in large networks. We first show that taking into account physical layer impairments and the consequent possible regeneration is mandatory to achieve satisfactory energy efficiency inRWA algorithms. In this respect, results show that LRF is much more efficient than “impairment unaware”RWA algorithms. Then, we assess the energy efficiency achievable with different modulation formats using the proposed LRF algorithm in single-line-rate networks. Finally, the case of mixed-line-rate networks is also considered, and a heuristic method is proposed to efficiently decide the set of connections, at different bit rates, to be assigned to each traffic demand, with the goal of minimizing the total consumed power. Results show that this method is able to achieve power saving up to 25%