In Elastic Optical Network (EON), spectrum fragmentation refers to the existence of non-aligned, ... more In Elastic Optical Network (EON), spectrum fragmentation refers to the existence of non-aligned, smallsized blocks of free subcarrier slots in the optical spectrum. Several metrics have been proposed in order to quantify a level of spectrum fragmentation. Approximation methods might be used for estimating average blocking probability and some fragmentation measures, but are so far unable to accurately evaluate the influence of different sizes of connection requests and do not allow in-depth investigation of blocking events and their relation to fragmentation. The analytical study of the effect of fragmentation on requests' blocking probability is still under-explored. In this work, we introduce new definitions for blocking that differentiate between the reasons for the blocking events. We developed a framework based on Markov modeling to calculate steady-state probabilities for the different blocking events and to analyze fragmentation related problems in elastic optical links under dynamic traffic conditions. This framework can also be used for evaluation of different definitions of fragmentation in terms of their relation to the blocking probability. We investigate how different allocation request sizes contribute to fragmentation and blocking probability. Moreover, we show to which extend blocking events, due to insufficient amount of available resources, become inevitable and, compared to the amount of blocking events due to fragmented spectrum, we draw conclusions on the possible gains one can achieve by system defragmentation. We also show how efficient spectrum allocation policies really are in reducing the part of fragmentation that in particular leads to actual blocking events. Simulation experiments are carried out showing good match with our analytical results for blocking probability in a small scale scenario. Simulated blocking probabilities for the different blocking events are provided for a larger scale elastic optical link.
2016 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET), 2016
In this paper we have computed the blocking probability of dynamic traffic using statistical meth... more In this paper we have computed the blocking probability of dynamic traffic using statistical method for WDM networks. Here, the logical topology created for dynamic traffic is transformed by virtually connected static g-link topology. We have computed the blocking performance of dynamic traffic using Erlang B traffic loss model that is mapped with g-link topology.
This paper highlights the challenges faced by the current datacenter networks, where using photon... more This paper highlights the challenges faced by the current datacenter networks, where using photonic technology offers a numbers of obvious advantages. Some existing optical intra-datacenter network architectures will be presented along with new ideas allowing for reduction of energy consumption and required spectrum resources.
Joint scheduling and routing of data flows with deadline constraints in communication networks ha... more Joint scheduling and routing of data flows with deadline constraints in communication networks has been attracting research interest. This type of problem distinguishes from conventional multicommodity flows due to the presence of the time dimension. In this paper, we address a flow routing and scheduling problem with delivery deadline, where the assignment of link capacity occurs in discrete units. Discrete capacity allocation is motivated by applications in communication systems, where it is common to have a base unit of capacity (e.g., wavelength channel in optical communications). We present and prove complexity results of the problem. Next, we give an optimization formulation based on a time slicing approach (TSA), which amounts to a discretization of the time into time slices to enable to formulate the deadline constraints. We then derive an effective reformulation of the problem, via which a column generation algorithm (CGA) is developed. In addition, we propose a simple and ...
Abstract—This paper focuses on the impact that energy-efficient techniques have on the component ... more Abstract—This paper focuses on the impact that energy-efficient techniques have on the component lifetime in optical backbone networks. The study presented in the paper considers in particular the influence that green routing strategies have on the failure rate of Erbium Doped Fiber Amplifiers (EDFAs), i.e., if their lifetime is positively or negatively impacted when putting them into sleep mode in order to reduce their energy consumption. To this end, the paper proposes a model that estimates the failure rate acceleration factor as a function of: (i) for how long and how frequently a device is switched into sleep mode, and (ii) hardware parameters that characterize the device. The proposed model is then evaluated by considering an energy-efficient Routing and Wavelength Assignment (RWA) strategy that targets saving energy by putting EDFAs into sleep mode. The results presented in the paper show that energy-efficient techniques may have the potential to lower the failure rate of EDF...
In those networking scenarios (e.g., the stationary/mobile wireless paradigm) where limited energ... more In those networking scenarios (e.g., the stationary/mobile wireless paradigm) where limited energy storage capabilities is a limiting factor, power efficiency has been studied extensively for a long time. In the last few years, the steadily growing power consumption figures of ICT [1][2] along with a recent public awareness of the possible environmental effects, broadened the focus of the research efforts towards more power conscious solutions also for wired networks. One promising solution going in this direction is represented by transparent wavelength division multiplexing (WDM) networks, where all-optical circuits (or lightpaths) carry the network traffic from the source to the destination node in the optical domain, i.e. without any optical-to-electrical (O-E-O) conversion. To further improve network power efficiency, several approaches have been proposed in the literature attempting to reduce the power consumption in transparent WDM networks [3][4]. Among them, power aware (PA...
Abstract- Despite their intrinsic power efficiency, transparent wavelength division multiplexing ... more Abstract- Despite their intrinsic power efficiency, transparent wavelength division multiplexing (WDM) networks have additional potentials to save energy, and have attracted the interest of researchers with many power-aware (PA) routing and wavelength assignment (RWA) solutions being proposed in the literature. These approaches seem to have, however, an adverse effect on network blocking probability performance. This paper aims at providing a different insight to the PA-RWA problem. The idea is based on the intuition that power minimization and resource blocking can be jointly treated. The proposed approach, called Weighted Power-Aware RWA (WPA-RWA), has been tested using a continental core network and the performance evaluation confirms the presence of a trade-off between power saving and blocking probability. I.
Abstract—Improving the energy efficiency in telecom-munication networks has been one of the main ... more Abstract—Improving the energy efficiency in telecom-munication networks has been one of the main research topics of the past few years. As a result, many energy effi-cient algorithms have been proposed, some focusing on maximizing only the energy savings, others considering also the impact that green strategies have on other network performance metrics, e.g., delay, utilization of network re-sources, and blocking probability. The aim of this paper is to provide new insight on the impact of energy efficient strategies, i.e., investigating the trade-off between green network operations and the reliability performance of op-tical backbone devices. The study is motivated by the intu-ition that energy efficient strategies are usually based on putting unutilized devices in power saving (sleep) mode, which can have some side effects (e.g., frequent on/sleep switching, and/or high fiber link utilization) thatmay affect the working conditions of a device. To better understand these phenomena...
Energy consumption in telecommunication networks has become a significant problem during the last... more Energy consumption in telecommunication networks has become a significant problem during the last few years. Many energy efficient mechanisms have been proposed and evaluated with respect to their impact on the overall network performance (e.g., delay, blocking probability, quality of transmission). Most of these mechanisms are based on the sleep mode functionality, i.e., a “low power ” state of network devices that can be utilized in low traffic conditions. On the other hand, a frequent switching between a working and a sleeping state may increase the probability of failures in a device, which in turn makes the operational cost related to fault reparation higher. This paper discusses how sleep mode-based energy saving mechanisms can impact the reliability performance of network equipment by pointing out several physical phenomena that may lead to an increase of the failure rate. In order to quantify such effects we propose a methodology that estimates to what extent energy savings ...
The wireless internet access of the Kista - IT University network started out in October 1999 as ... more The wireless internet access of the Kista - IT University network started out in October 1999 as a research project - "The FlyingLinux project" - in the Telecommunication Systems Lab at the Department of Teleinformatics at KTH (Sweden).
2013 17th International Conference on Optical Networking Design and Modeling (ONDM), 2013
In this paper we propose a scheme tailored for WDM-PONs, which employs dozing mode in transceiver... more In this paper we propose a scheme tailored for WDM-PONs, which employs dozing mode in transceivers not only at the user side but also at the central office. The objective is to reduce the energy consumption while minimizing the impact on the total packet delay. The proposed scheme is able to take into account the diverse delay requirement of multiple traffic classes by adapting the wakeup time of the transmitter. Simulation results confirm that the proposed scheme can significantly improve the power efficiency in WDM-PONs while maintaining the maximum packet delay at an acceptable level, in particular in cases where multiple traffic classes are considered.
The energy consumption of communication networks is continuously growing. Many energy saving appr... more The energy consumption of communication networks is continuously growing. Many energy saving approaches have been proposed at the device, system, and network level. The most promising way to addres ...
This paper presents Comarch's work performed in the frame of Eureka/Celtic project MANGO - Ma... more This paper presents Comarch's work performed in the frame of Eureka/Celtic project MANGO - Management platform for Next Generation Optical networks, where we define and create a management platform for all-optical networks. The main issues considered within the project are (a) cross-layer automated fault and performance management, (b) complex Service Quality management and (c) management of optical connections with appropriate support from the management system. In this paper we describe how the optical services can be defined and monitored within the platform. We describe the data model including physical impairments to be used by Routing and Wavelength Assignment (RWA) algorithms performing optical path computation.
2017 9th International Workshop on Resilient Networks Design and Modeling (RNDM), 2017
High reliability performance of network is essential to minimize the possible network service int... more High reliability performance of network is essential to minimize the possible network service interruption time, particularly in optical backbone networks where a large amount of data can be affected by a single failure. The existing studies on improvement of network reliability performance assume that failures of network devices are not related to the traffic load, which on the other hand, is not always true. For example, the lifetime of erbium doped fiber amplifier (EDFA) depends on the number of amplified lightpaths passing through. Encouraged by this observation, in this paper, we investigate the impact of used routing and wavelength assignment (RWA) algorithm on the number of failures in the network, and as a consequence on the network operational cost related to the failure reparation. We propose and evaluate a novel RWA approach, referred to as reliability performance aware RWA (RA-RWA), taking into account particular EDFA reliability performance characteristics with the goal...
In communication networks, a device failure is never a desired event, as it can interrupt multipl... more In communication networks, a device failure is never a desired event, as it can interrupt multiple connections and disturb transmission of large amount of data and thus decrease connection reliability performance. The approaches used to ensure high connection reliability performance focus mainly on minimizing the impact due to a device failure by using backup resources. These approaches commonly assume the reliability performance of a device to be constant. However, it is known that the device reliability performance is related to its level of occupancy. In this article we leverage on this relation and propose a novel routing algorithm referred to as: device reliability performance aware routing (RAR) that allows for significant reduction of the number of device failures and connection reconfigurations in the network. The proposed RAR algorithm is evaluated using simulations and compared to the shortest path (SP) approach. Evaluation results show that RAR can provide significant ben...
This paper describes our work with the design and deployment of a tangible user interface for con... more This paper describes our work with the design and deployment of a tangible user interface for controlling an interactive workspace. Our intention was to design a user interface that makes it possible to use the room without focusing on the technology behind. We found that the problems are especially at the beginning of a work session when a group enters a totally shut-down workspace and have to spend valuable time starting and configuring every device before they are able to start working. The Magic Bowl makes it possible to quickly start the interactive workspace with a personalized configuration.
This paper presents a hierarchical interconnect architecture for optical data center networks com... more This paper presents a hierarchical interconnect architecture for optical data center networks composed of specially designed couplers allowing for significant reduction of required spectral resources.
In Elastic Optical Network (EON), spectrum fragmentation refers to the existence of non-aligned, ... more In Elastic Optical Network (EON), spectrum fragmentation refers to the existence of non-aligned, smallsized blocks of free subcarrier slots in the optical spectrum. Several metrics have been proposed in order to quantify a level of spectrum fragmentation. Approximation methods might be used for estimating average blocking probability and some fragmentation measures, but are so far unable to accurately evaluate the influence of different sizes of connection requests and do not allow in-depth investigation of blocking events and their relation to fragmentation. The analytical study of the effect of fragmentation on requests' blocking probability is still under-explored. In this work, we introduce new definitions for blocking that differentiate between the reasons for the blocking events. We developed a framework based on Markov modeling to calculate steady-state probabilities for the different blocking events and to analyze fragmentation related problems in elastic optical links under dynamic traffic conditions. This framework can also be used for evaluation of different definitions of fragmentation in terms of their relation to the blocking probability. We investigate how different allocation request sizes contribute to fragmentation and blocking probability. Moreover, we show to which extend blocking events, due to insufficient amount of available resources, become inevitable and, compared to the amount of blocking events due to fragmented spectrum, we draw conclusions on the possible gains one can achieve by system defragmentation. We also show how efficient spectrum allocation policies really are in reducing the part of fragmentation that in particular leads to actual blocking events. Simulation experiments are carried out showing good match with our analytical results for blocking probability in a small scale scenario. Simulated blocking probabilities for the different blocking events are provided for a larger scale elastic optical link.
2016 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET), 2016
In this paper we have computed the blocking probability of dynamic traffic using statistical meth... more In this paper we have computed the blocking probability of dynamic traffic using statistical method for WDM networks. Here, the logical topology created for dynamic traffic is transformed by virtually connected static g-link topology. We have computed the blocking performance of dynamic traffic using Erlang B traffic loss model that is mapped with g-link topology.
This paper highlights the challenges faced by the current datacenter networks, where using photon... more This paper highlights the challenges faced by the current datacenter networks, where using photonic technology offers a numbers of obvious advantages. Some existing optical intra-datacenter network architectures will be presented along with new ideas allowing for reduction of energy consumption and required spectrum resources.
Joint scheduling and routing of data flows with deadline constraints in communication networks ha... more Joint scheduling and routing of data flows with deadline constraints in communication networks has been attracting research interest. This type of problem distinguishes from conventional multicommodity flows due to the presence of the time dimension. In this paper, we address a flow routing and scheduling problem with delivery deadline, where the assignment of link capacity occurs in discrete units. Discrete capacity allocation is motivated by applications in communication systems, where it is common to have a base unit of capacity (e.g., wavelength channel in optical communications). We present and prove complexity results of the problem. Next, we give an optimization formulation based on a time slicing approach (TSA), which amounts to a discretization of the time into time slices to enable to formulate the deadline constraints. We then derive an effective reformulation of the problem, via which a column generation algorithm (CGA) is developed. In addition, we propose a simple and ...
Abstract—This paper focuses on the impact that energy-efficient techniques have on the component ... more Abstract—This paper focuses on the impact that energy-efficient techniques have on the component lifetime in optical backbone networks. The study presented in the paper considers in particular the influence that green routing strategies have on the failure rate of Erbium Doped Fiber Amplifiers (EDFAs), i.e., if their lifetime is positively or negatively impacted when putting them into sleep mode in order to reduce their energy consumption. To this end, the paper proposes a model that estimates the failure rate acceleration factor as a function of: (i) for how long and how frequently a device is switched into sleep mode, and (ii) hardware parameters that characterize the device. The proposed model is then evaluated by considering an energy-efficient Routing and Wavelength Assignment (RWA) strategy that targets saving energy by putting EDFAs into sleep mode. The results presented in the paper show that energy-efficient techniques may have the potential to lower the failure rate of EDF...
In those networking scenarios (e.g., the stationary/mobile wireless paradigm) where limited energ... more In those networking scenarios (e.g., the stationary/mobile wireless paradigm) where limited energy storage capabilities is a limiting factor, power efficiency has been studied extensively for a long time. In the last few years, the steadily growing power consumption figures of ICT [1][2] along with a recent public awareness of the possible environmental effects, broadened the focus of the research efforts towards more power conscious solutions also for wired networks. One promising solution going in this direction is represented by transparent wavelength division multiplexing (WDM) networks, where all-optical circuits (or lightpaths) carry the network traffic from the source to the destination node in the optical domain, i.e. without any optical-to-electrical (O-E-O) conversion. To further improve network power efficiency, several approaches have been proposed in the literature attempting to reduce the power consumption in transparent WDM networks [3][4]. Among them, power aware (PA...
Abstract- Despite their intrinsic power efficiency, transparent wavelength division multiplexing ... more Abstract- Despite their intrinsic power efficiency, transparent wavelength division multiplexing (WDM) networks have additional potentials to save energy, and have attracted the interest of researchers with many power-aware (PA) routing and wavelength assignment (RWA) solutions being proposed in the literature. These approaches seem to have, however, an adverse effect on network blocking probability performance. This paper aims at providing a different insight to the PA-RWA problem. The idea is based on the intuition that power minimization and resource blocking can be jointly treated. The proposed approach, called Weighted Power-Aware RWA (WPA-RWA), has been tested using a continental core network and the performance evaluation confirms the presence of a trade-off between power saving and blocking probability. I.
Abstract—Improving the energy efficiency in telecom-munication networks has been one of the main ... more Abstract—Improving the energy efficiency in telecom-munication networks has been one of the main research topics of the past few years. As a result, many energy effi-cient algorithms have been proposed, some focusing on maximizing only the energy savings, others considering also the impact that green strategies have on other network performance metrics, e.g., delay, utilization of network re-sources, and blocking probability. The aim of this paper is to provide new insight on the impact of energy efficient strategies, i.e., investigating the trade-off between green network operations and the reliability performance of op-tical backbone devices. The study is motivated by the intu-ition that energy efficient strategies are usually based on putting unutilized devices in power saving (sleep) mode, which can have some side effects (e.g., frequent on/sleep switching, and/or high fiber link utilization) thatmay affect the working conditions of a device. To better understand these phenomena...
Energy consumption in telecommunication networks has become a significant problem during the last... more Energy consumption in telecommunication networks has become a significant problem during the last few years. Many energy efficient mechanisms have been proposed and evaluated with respect to their impact on the overall network performance (e.g., delay, blocking probability, quality of transmission). Most of these mechanisms are based on the sleep mode functionality, i.e., a “low power ” state of network devices that can be utilized in low traffic conditions. On the other hand, a frequent switching between a working and a sleeping state may increase the probability of failures in a device, which in turn makes the operational cost related to fault reparation higher. This paper discusses how sleep mode-based energy saving mechanisms can impact the reliability performance of network equipment by pointing out several physical phenomena that may lead to an increase of the failure rate. In order to quantify such effects we propose a methodology that estimates to what extent energy savings ...
The wireless internet access of the Kista - IT University network started out in October 1999 as ... more The wireless internet access of the Kista - IT University network started out in October 1999 as a research project - "The FlyingLinux project" - in the Telecommunication Systems Lab at the Department of Teleinformatics at KTH (Sweden).
2013 17th International Conference on Optical Networking Design and Modeling (ONDM), 2013
In this paper we propose a scheme tailored for WDM-PONs, which employs dozing mode in transceiver... more In this paper we propose a scheme tailored for WDM-PONs, which employs dozing mode in transceivers not only at the user side but also at the central office. The objective is to reduce the energy consumption while minimizing the impact on the total packet delay. The proposed scheme is able to take into account the diverse delay requirement of multiple traffic classes by adapting the wakeup time of the transmitter. Simulation results confirm that the proposed scheme can significantly improve the power efficiency in WDM-PONs while maintaining the maximum packet delay at an acceptable level, in particular in cases where multiple traffic classes are considered.
The energy consumption of communication networks is continuously growing. Many energy saving appr... more The energy consumption of communication networks is continuously growing. Many energy saving approaches have been proposed at the device, system, and network level. The most promising way to addres ...
This paper presents Comarch's work performed in the frame of Eureka/Celtic project MANGO - Ma... more This paper presents Comarch's work performed in the frame of Eureka/Celtic project MANGO - Management platform for Next Generation Optical networks, where we define and create a management platform for all-optical networks. The main issues considered within the project are (a) cross-layer automated fault and performance management, (b) complex Service Quality management and (c) management of optical connections with appropriate support from the management system. In this paper we describe how the optical services can be defined and monitored within the platform. We describe the data model including physical impairments to be used by Routing and Wavelength Assignment (RWA) algorithms performing optical path computation.
2017 9th International Workshop on Resilient Networks Design and Modeling (RNDM), 2017
High reliability performance of network is essential to minimize the possible network service int... more High reliability performance of network is essential to minimize the possible network service interruption time, particularly in optical backbone networks where a large amount of data can be affected by a single failure. The existing studies on improvement of network reliability performance assume that failures of network devices are not related to the traffic load, which on the other hand, is not always true. For example, the lifetime of erbium doped fiber amplifier (EDFA) depends on the number of amplified lightpaths passing through. Encouraged by this observation, in this paper, we investigate the impact of used routing and wavelength assignment (RWA) algorithm on the number of failures in the network, and as a consequence on the network operational cost related to the failure reparation. We propose and evaluate a novel RWA approach, referred to as reliability performance aware RWA (RA-RWA), taking into account particular EDFA reliability performance characteristics with the goal...
In communication networks, a device failure is never a desired event, as it can interrupt multipl... more In communication networks, a device failure is never a desired event, as it can interrupt multiple connections and disturb transmission of large amount of data and thus decrease connection reliability performance. The approaches used to ensure high connection reliability performance focus mainly on minimizing the impact due to a device failure by using backup resources. These approaches commonly assume the reliability performance of a device to be constant. However, it is known that the device reliability performance is related to its level of occupancy. In this article we leverage on this relation and propose a novel routing algorithm referred to as: device reliability performance aware routing (RAR) that allows for significant reduction of the number of device failures and connection reconfigurations in the network. The proposed RAR algorithm is evaluated using simulations and compared to the shortest path (SP) approach. Evaluation results show that RAR can provide significant ben...
This paper describes our work with the design and deployment of a tangible user interface for con... more This paper describes our work with the design and deployment of a tangible user interface for controlling an interactive workspace. Our intention was to design a user interface that makes it possible to use the room without focusing on the technology behind. We found that the problems are especially at the beginning of a work session when a group enters a totally shut-down workspace and have to spend valuable time starting and configuring every device before they are able to start working. The Magic Bowl makes it possible to quickly start the interactive workspace with a personalized configuration.
This paper presents a hierarchical interconnect architecture for optical data center networks com... more This paper presents a hierarchical interconnect architecture for optical data center networks composed of specially designed couplers allowing for significant reduction of required spectral resources.
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