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Davide Cuda

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Papers by Davide Cuda

A Distributed Scheduling Algorithm for an Optical Switching Fabric

2008 IEEE International Conference on Communications, 2008

Designing switching architectures for network routers and switches needs to consider limits impos... more Designing switching architectures for network routers and switches needs to consider limits imposed by the electronic technology, like small bandwidth×distance factors, power density constraints, energy consumption and dissipation issues. Introducing optical technologies to implement switching functions can overcome several of the current design limits. We propose a cost-effective architecture implementing an optical switch without any need for optoelectronic conversion within the switching fabric. We further propose a distributed scheduling scheme, based on an extension of the Fasnet protocol, and we compare it to classical centralized scheduling algorithms, showing that a distributed scheduler can provide performance comparable to the ones offered by more complex centralized schedulers. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the ICC 2008 proceedings.

Multi-MetaRing Protocol: Fairness in Optical Packet Ring Networks

2007 IEEE International Conference on Communications, 2007

We focus on Metropolitan Area Networks operating in packet mode and exploiting a single-hop wavel... more We focus on Metropolitan Area Networks operating in packet mode and exploiting a single-hop wavelength division multiplexing (WDM) architecture. First, we briefly describe a specific slotted WDM optical network, based on a folded bus topology. Then, we address the fairness problem arising in this architecture and propose an extension of the MetaRing protocol to a WDM scenario. Two possible strategies are defined and analyzed. Finally, we show that both fair access and high aggregate network throughput can be achieved by properly handling node access through all WDM channels.

An Optical Interconnection Architecture for Large Packet Switches

2007 9th International Conference on Transparent Optical Networks, 2007

The design of switching architectures for today's telecommunication networks needs to consider th... more The design of switching architectures for today's telecommunication networks needs to consider the limits imposed by electronic technology; in particular, it must take into account power consumption and dissipation, as well as power supply and footprint requirements. Currently, optical technology is exploited mainly for transmission over optical links requiring large bandwidth-distance products; however, many researchers and switch architects believe that its introduction for switching functions can overcome most of the current design limits. Since many years, the research community has been studying not only solutions that make use of optics inside electronic switches but that also switching architectures that implement optical switching without any need of optoelectronic conversion. In this paper, we propose an optical switching architecture based on a WDM (Wavelength Division Multiplexing) optical bus, aiming at interconnecting electronic line cards inside packet switches. In particular, the use of distributed packet scheduling techniques is addressed and its performance is discussed.

Multi-Fasnet: a simple scheduling algorithm for a distributed optical switch

The design of classic switching architectures for today's telecommunication network needs to ... more The design of classic switching architectures for today's telecommunication network needs to consider the limits imposed by the electronic technology; like, power supply, con- sumption and dissipation. The introduction optical technology for switching functions can overcome the most of the current design limits. We propose a cost-effective architecture that implement optical switching without any need of optoelectronic conversion. Moreover, we

Optical interconnection architectures based on microring resonators

2009 International Conference on Photonics in Switching, 2009

Microring resonators are an interesting device to build integrated optical interconnects, but the... more

Getting routers out of the core: Building an all-optical network with “multipaths&#x201D

2012 16th International Conference on Optical Network Design and Modelling (ONDM), 2012

We propose an all-optical networking solution for an Internet core network based on the notion of... more We propose an all-optical networking solution for an Internet core network based on the notion of multipoint-to-multipoint lightpaths that, for short, we call multipaths. The multipath MAC protocol concentrates the traffic of a cluster of source nodes on a wavelength channel and multicasts this traffic to a cluster of destination nodes. The proposed network can be built using existing components

Short-term fairness in slotted WDM rings

Computer Networks, 2015

ABSTRACT Single-hop WDM ring networks are promising architectures for future broadband access and... more ABSTRACT Single-hop WDM ring networks are promising architectures for future broadband access and metro networks. However, ring networks exhibit significant fairness issues, which must be handled by a fairness enforcing protocol. Fairness is usually ensured over a time window of several network propagation delays. Thus, data flows might experience large access delays which might be not compatible to support time-sensitive applications. We solve this issue proposing the Multi-Fasnet protocol, which is able to enforce fairness in a relative short time scale, in the order of few propagation delays, without trading off the aggregated throughput network performance. We discuss Multi-Fasnet limitations and propose several novel strategies that achieve high and fair network throughput as well as low, bounded and fair access delays.

Traffic growth and network engineering in optical mesh networks

2008 34th European Conference on Optical Communication, 2008

Abstract: Backbone networks employing optical meshes require periodic upgrades to support increas... more

Crosstalk Limiting Schedulers in AWG Based Optical Switches

2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010

Optical switching fabrics are gaining interest as in multi Terabit switching devices; the advanta... more Optical switching fabrics are gaining interest as in multi Terabit switching devices; the advantages over their electronic equivalents are mainly their information density and power consumption. Arrayed Waveguide Gratings (AWGs) are promising optical devices proposed by the academic and industrial community to build optical switching fabrics. Because of their wavelength routing property, AWGs allow wavelength reuse over different ports introducing in-band crosstalk which strongly limits scalability of AWG-based backplanes. However, this effect can be mitigated or even completely avoided by means of proper scheduling algorithms. In this paper, we present several modified scheduling algorithms which limit the effect of coherent crosstalk in AWG-based switching fabrics and achieve good performance in terms of throughput and delay.

Asynchronous vs Synchronous Input-Queued Switches

2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010

Input-queued (IQ) switches are one of the reference architectures for the design of high-speed pa... more Input-queued (IQ) switches are one of the reference architectures for the design of high-speed packet switches. Classical results in this field refer to the scenario in which the whole switch transfers the packets in a synchronous fashion, in phase with a sequence of fixed-size timeslots, selected to transport a minimum-size packet. However, for switches with large number of ports and high bandwidth, maintaining an accurate global synchronization and transferring all the packets in a synchronous fashion is becoming more and more challenging. Furthermore, variable size packets (as in the traffic present in the Internet) require rather complex segmentation and reassembly processes and some switching capacity is lost due to partial filling of timeslots. Thus, we consider a switch able to natively transfer packets in an asynchronous fashion thanks to a simple and distributed packet scheduler. We investigate the performance of asynchronous IQ switches and show that, despite their simplicity, their performance are comparable or even better than those of synchronous switches. These partly unexpected results highlight the great potentiality of the asynchronous approach for the design of high-performance switches.

WONDER: A PON over a Folded Bus

IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008

Passive Optical Networks (PONs) represent a step forward in "first mile" networks; indeed, by usi... more Passive Optical Networks (PONs) represent a step forward in "first mile" networks; indeed, by using optical technologies, PONs can transfer a large amount of data, and by being completely passive, they reduce management costs and failure probabilities. Access network is logically a point-to-multipoint network and the tree topology emerged as the winning solution; however, it naturally lacks protection capability and requires local traffic to be processed by the Optical Line Terminal. In this paper, we present WONDER, a novel PON architecture based on a folded bus topology, which offers fault resilience and efficient local traffic support, and we discuss WONDER strengths and weaknesses. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE "GLOBECOM" 2008 proceedings.

Optics vs. electronics in future high-capacity switches/routers

2009 International Conference on High Performance Switching and Routing, 2009

The rapid growth of the Internet traffic demand is bringing the current electronic switches close... more The rapid growth of the Internet traffic demand is bringing the current electronic switches closer to their intrinsic technological limits, which may be overcome by optical technologies. Although optical packet switching has been widely studied in academia; the limited processing and buffering capabilities available in the optical domain makes the implementation of an all optical packet switch difficult in practice. We considered a hybrid (electro/optic) switching architecture, relying on an all-optical switching fabric, aiming to understanding the tradeoffs between current photonic and electronic technologies. We consider both the classical fixed-size synchronous paradigm and the asynchronous operation mode, which may suit better to the optical technologies. Buffers organized according to either an electronic FIFO (First Input First Output) paradigm or a photonic FDL (Fiber Delay Line) mechanism are analyzed and compared.

OPN03-1: Multi-Fasnet Protocol: Short-Term Fairness Control in WDM Slotted MANs

IEEE Globecom 2006, 2006

Single-hop wavelength division multiplexing (WDM) ring networks operating in packet mode are a pr... more Single-hop wavelength division multiplexing (WDM) ring networks operating in packet mode are a promising architecture for the design of innovate Metropolitan Area Networks. They allow a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metropolitan scenario. In this article, we address the fairness problem in a slotted WDM optical network. We introduce the Multi-Fasnet fairness protocol, we discuss its limitations and we propose an extension, based on a dynamic strategy, that achieves high aggregate network throughput, throughput fairness, and bounded and fair access delays.

Crosstalk Minimization in Microring-Based Wavelength Routing Matrices

2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011

Optical switching fabrics (OSF) are gaining interest because they promise to satisfy the higher i... more Optical switching fabrics (OSF) are gaining interest because they promise to satisfy the higher information densities demanded by each successive generation of high-end routers and switches. Silicon microring resonators (MRR) can be employed to perform switching operations directly in the optical domain. However, similarly to other devices used to build all-optical switching fabrics, such as Arrayed Waveguide Gratings (AWG), MRR-based switching fabrics might show a limited scalability in terms of port count due to the crosstalk accumulation caused by the spatial wavelengths reuse. We consider an OSF built on a Wavelength-Routing-Matrix (WRM) based on MRRs, we highlight its scalability issues and we propose a new design as well as two different strategies to limit the wavelength spatial reuse.

Optical Interconnection Networks Based on Microring Resonators

2010 IEEE International Conference on Communications, 2010

Optical microring resonators can be integrated on a chip to perform switching operations directly... more Optical microring resonators can be integrated on a chip to perform switching operations directly in the optical domain. Thus they become a building block to create switching elements in on-chip optical interconnection networks, which promise to overcome some of the limitations of current electronic networks. However, the peculiar asymmetric power losses of microring resonators impose new constraints on the design and control of on-chip optical networks. In this work, we study the design of multistage interconnection networks optimized for a particular metric that we name degradation index, which characterizes the asymmetric behavior of microrings. We also propose a routing control algorithm to maximize the overall throughput, considering the maximum allowed degradation index as a constraint.

The role of Arrayed Waveguide Gratings in energy-efficient optical switching architectures

Optical Fiber Communication Conference, 2010

The power consumption of large IP routers is increasing too fast with the increase of Internet tr... more The power consumption of large IP routers is increasing too fast with the increase of Internet traffic. This power consumption can be reduced if Optical Switching Fabrics (OSFs) are used instead of electronic backplanes and interconnects. And Arrayed Waveguide Gratings (AWGs) exhibit interesting properties for the design and implementation of OSFs. The paper studies how OSFs based upon AWGs scale

Belief-Propagation-Assisted Scheduling in Input-Queued Switches

by M. Pretti and Davide Cuda

IEEE Transactions on Computers, 2000

ABSTRACT We consider the problem of scheduling packets transmission across the switching fabric i... more ABSTRACT We consider the problem of scheduling packets transmission across the switching fabric in an input-queued switch. In order to achieve maximum throughput, scheduling algorithms usually employ the queue length as a parameter for determining the priority to serve a given queue. Unfortunately, optimal schedulers are too complex to be implemented directly in hardware, which is the only viable solution in high-end switches, since scheduling decisions must be taken in very short time, of order of ns. Conversely, implement able algorithms, based on parallel and greedy decisions, are inefficient in terms of throughput. In this work we do not propose any new scheduling algorithm or switching architecture, but a novel scheme to optimize the performance of a pre-existing scheduler. Indeed, we propose to assist the scheduling decision by considering &quot;message&quot; values instead of queue lengths. Such messages are obtained by running an iterative parallel algorithm (efficiently implement able in hardware and fully compatible with pre-existing schedulers), based on a rigorous Belief-Propagation approach. We show that BP-assisted scheduling is able to boost the performance of a given scheduler, reaching almost optimal throughput, even under critical traffic scenarios.

Scalability of Optical Interconnects Based on Microring Resonators

IEEE Photonics Technology Letters, 2010

This paper investigates the use of optical microring resonators as switching elements in large op... more This paper investigates the use of optical microring resonators as switching elements in large optical interconnection fabrics. We introduce a simple physical-layer model to assess scalability in crossbar-and Benes-based architectures. We also propose a new dilated switching element that improves scalability to build fabrics of several Tbps of aggregate capacity.

Design and control of next generation distribution frames

Computer Networks, 2012

In today's access networks, the permutation of circuits connecting the subscriber lines to Plain ... more In today's access networks, the permutation of circuits connecting the subscriber lines to Plain Old Telephone Service (POTS) and to Digital Subscriber Line Access Multiplexers (DSLAMs) occurs in the Main Distribution Frame (MDF) and is still manually configured. However, new market regulations and new policies adopted by operators require increasingly more frequent permutations, making the manual configuration activity particularly expensive. Very recently, Automated MDFs (AMDF) have been developed to provide inexpensive and almost real-time switching capability. Our study, based on more than 50 years of research activities on architectures for circuit switching, is focused on overcoming the limits of classical architectures. In fact, strictly non-blocking multistage networks are too expensive, as a consequence of the large number of ports they require (sometimes exceeding 100,000). In addition, rearrangeable multistage networks can temporarily interrupt active circuits, affecting the performance of ADSL subscriber lines. As a possible solution to these problems, we propose the design of AMDFs based on Non-Interruptive Rearrangeable (NIR) networks. We show how to optimize the routing control to minimize the setup time of a circuit and to exploit output grouping. We believe that the solution described above is not only relevant for the theory of multistage interconnection networks, but also for the design and operation of large AMDFs.

Getting routers out of the core: Building an optical wide area network with

A Distributed Scheduling Algorithm for an Optical Switching Fabric

2008 IEEE International Conference on Communications, 2008

Designing switching architectures for network routers and switches needs to consider limits impos... more Designing switching architectures for network routers and switches needs to consider limits imposed by the electronic technology, like small bandwidth×distance factors, power density constraints, energy consumption and dissipation issues. Introducing optical technologies to implement switching functions can overcome several of the current design limits. We propose a cost-effective architecture implementing an optical switch without any need for optoelectronic conversion within the switching fabric. We further propose a distributed scheduling scheme, based on an extension of the Fasnet protocol, and we compare it to classical centralized scheduling algorithms, showing that a distributed scheduler can provide performance comparable to the ones offered by more complex centralized schedulers. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the ICC 2008 proceedings.

Multi-MetaRing Protocol: Fairness in Optical Packet Ring Networks

2007 IEEE International Conference on Communications, 2007

We focus on Metropolitan Area Networks operating in packet mode and exploiting a single-hop wavel... more We focus on Metropolitan Area Networks operating in packet mode and exploiting a single-hop wavelength division multiplexing (WDM) architecture. First, we briefly describe a specific slotted WDM optical network, based on a folded bus topology. Then, we address the fairness problem arising in this architecture and propose an extension of the MetaRing protocol to a WDM scenario. Two possible strategies are defined and analyzed. Finally, we show that both fair access and high aggregate network throughput can be achieved by properly handling node access through all WDM channels.

An Optical Interconnection Architecture for Large Packet Switches

2007 9th International Conference on Transparent Optical Networks, 2007

The design of switching architectures for today's telecommunication networks needs to consider th... more The design of switching architectures for today's telecommunication networks needs to consider the limits imposed by electronic technology; in particular, it must take into account power consumption and dissipation, as well as power supply and footprint requirements. Currently, optical technology is exploited mainly for transmission over optical links requiring large bandwidth-distance products; however, many researchers and switch architects believe that its introduction for switching functions can overcome most of the current design limits. Since many years, the research community has been studying not only solutions that make use of optics inside electronic switches but that also switching architectures that implement optical switching without any need of optoelectronic conversion. In this paper, we propose an optical switching architecture based on a WDM (Wavelength Division Multiplexing) optical bus, aiming at interconnecting electronic line cards inside packet switches. In particular, the use of distributed packet scheduling techniques is addressed and its performance is discussed.

Multi-Fasnet: a simple scheduling algorithm for a distributed optical switch

The design of classic switching architectures for today's telecommunication network needs to ... more The design of classic switching architectures for today's telecommunication network needs to consider the limits imposed by the electronic technology; like, power supply, con- sumption and dissipation. The introduction optical technology for switching functions can overcome the most of the current design limits. We propose a cost-effective architecture that implement optical switching without any need of optoelectronic conversion. Moreover, we

Optical interconnection architectures based on microring resonators

2009 International Conference on Photonics in Switching, 2009

Microring resonators are an interesting device to build integrated optical interconnects, but the... more

Getting routers out of the core: Building an all-optical network with “multipaths&#x201D

2012 16th International Conference on Optical Network Design and Modelling (ONDM), 2012

We propose an all-optical networking solution for an Internet core network based on the notion of... more We propose an all-optical networking solution for an Internet core network based on the notion of multipoint-to-multipoint lightpaths that, for short, we call multipaths. The multipath MAC protocol concentrates the traffic of a cluster of source nodes on a wavelength channel and multicasts this traffic to a cluster of destination nodes. The proposed network can be built using existing components

Short-term fairness in slotted WDM rings

Computer Networks, 2015

ABSTRACT Single-hop WDM ring networks are promising architectures for future broadband access and... more ABSTRACT Single-hop WDM ring networks are promising architectures for future broadband access and metro networks. However, ring networks exhibit significant fairness issues, which must be handled by a fairness enforcing protocol. Fairness is usually ensured over a time window of several network propagation delays. Thus, data flows might experience large access delays which might be not compatible to support time-sensitive applications. We solve this issue proposing the Multi-Fasnet protocol, which is able to enforce fairness in a relative short time scale, in the order of few propagation delays, without trading off the aggregated throughput network performance. We discuss Multi-Fasnet limitations and propose several novel strategies that achieve high and fair network throughput as well as low, bounded and fair access delays.

Traffic growth and network engineering in optical mesh networks

2008 34th European Conference on Optical Communication, 2008

Abstract: Backbone networks employing optical meshes require periodic upgrades to support increas... more

Crosstalk Limiting Schedulers in AWG Based Optical Switches

2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010

Optical switching fabrics are gaining interest as in multi Terabit switching devices; the advanta... more Optical switching fabrics are gaining interest as in multi Terabit switching devices; the advantages over their electronic equivalents are mainly their information density and power consumption. Arrayed Waveguide Gratings (AWGs) are promising optical devices proposed by the academic and industrial community to build optical switching fabrics. Because of their wavelength routing property, AWGs allow wavelength reuse over different ports introducing in-band crosstalk which strongly limits scalability of AWG-based backplanes. However, this effect can be mitigated or even completely avoided by means of proper scheduling algorithms. In this paper, we present several modified scheduling algorithms which limit the effect of coherent crosstalk in AWG-based switching fabrics and achieve good performance in terms of throughput and delay.

Asynchronous vs Synchronous Input-Queued Switches

2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010

Input-queued (IQ) switches are one of the reference architectures for the design of high-speed pa... more Input-queued (IQ) switches are one of the reference architectures for the design of high-speed packet switches. Classical results in this field refer to the scenario in which the whole switch transfers the packets in a synchronous fashion, in phase with a sequence of fixed-size timeslots, selected to transport a minimum-size packet. However, for switches with large number of ports and high bandwidth, maintaining an accurate global synchronization and transferring all the packets in a synchronous fashion is becoming more and more challenging. Furthermore, variable size packets (as in the traffic present in the Internet) require rather complex segmentation and reassembly processes and some switching capacity is lost due to partial filling of timeslots. Thus, we consider a switch able to natively transfer packets in an asynchronous fashion thanks to a simple and distributed packet scheduler. We investigate the performance of asynchronous IQ switches and show that, despite their simplicity, their performance are comparable or even better than those of synchronous switches. These partly unexpected results highlight the great potentiality of the asynchronous approach for the design of high-performance switches.

WONDER: A PON over a Folded Bus

IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008

Passive Optical Networks (PONs) represent a step forward in "first mile" networks; indeed, by usi... more Passive Optical Networks (PONs) represent a step forward in "first mile" networks; indeed, by using optical technologies, PONs can transfer a large amount of data, and by being completely passive, they reduce management costs and failure probabilities. Access network is logically a point-to-multipoint network and the tree topology emerged as the winning solution; however, it naturally lacks protection capability and requires local traffic to be processed by the Optical Line Terminal. In this paper, we present WONDER, a novel PON architecture based on a folded bus topology, which offers fault resilience and efficient local traffic support, and we discuss WONDER strengths and weaknesses. This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE "GLOBECOM" 2008 proceedings.

Optics vs. electronics in future high-capacity switches/routers

2009 International Conference on High Performance Switching and Routing, 2009

The rapid growth of the Internet traffic demand is bringing the current electronic switches close... more The rapid growth of the Internet traffic demand is bringing the current electronic switches closer to their intrinsic technological limits, which may be overcome by optical technologies. Although optical packet switching has been widely studied in academia; the limited processing and buffering capabilities available in the optical domain makes the implementation of an all optical packet switch difficult in practice. We considered a hybrid (electro/optic) switching architecture, relying on an all-optical switching fabric, aiming to understanding the tradeoffs between current photonic and electronic technologies. We consider both the classical fixed-size synchronous paradigm and the asynchronous operation mode, which may suit better to the optical technologies. Buffers organized according to either an electronic FIFO (First Input First Output) paradigm or a photonic FDL (Fiber Delay Line) mechanism are analyzed and compared.

OPN03-1: Multi-Fasnet Protocol: Short-Term Fairness Control in WDM Slotted MANs

IEEE Globecom 2006, 2006

Single-hop wavelength division multiplexing (WDM) ring networks operating in packet mode are a pr... more Single-hop wavelength division multiplexing (WDM) ring networks operating in packet mode are a promising architecture for the design of innovate Metropolitan Area Networks. They allow a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metropolitan scenario. In this article, we address the fairness problem in a slotted WDM optical network. We introduce the Multi-Fasnet fairness protocol, we discuss its limitations and we propose an extension, based on a dynamic strategy, that achieves high aggregate network throughput, throughput fairness, and bounded and fair access delays.

Crosstalk Minimization in Microring-Based Wavelength Routing Matrices

2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011

Optical switching fabrics (OSF) are gaining interest because they promise to satisfy the higher i... more Optical switching fabrics (OSF) are gaining interest because they promise to satisfy the higher information densities demanded by each successive generation of high-end routers and switches. Silicon microring resonators (MRR) can be employed to perform switching operations directly in the optical domain. However, similarly to other devices used to build all-optical switching fabrics, such as Arrayed Waveguide Gratings (AWG), MRR-based switching fabrics might show a limited scalability in terms of port count due to the crosstalk accumulation caused by the spatial wavelengths reuse. We consider an OSF built on a Wavelength-Routing-Matrix (WRM) based on MRRs, we highlight its scalability issues and we propose a new design as well as two different strategies to limit the wavelength spatial reuse.

Optical Interconnection Networks Based on Microring Resonators

2010 IEEE International Conference on Communications, 2010

Optical microring resonators can be integrated on a chip to perform switching operations directly... more Optical microring resonators can be integrated on a chip to perform switching operations directly in the optical domain. Thus they become a building block to create switching elements in on-chip optical interconnection networks, which promise to overcome some of the limitations of current electronic networks. However, the peculiar asymmetric power losses of microring resonators impose new constraints on the design and control of on-chip optical networks. In this work, we study the design of multistage interconnection networks optimized for a particular metric that we name degradation index, which characterizes the asymmetric behavior of microrings. We also propose a routing control algorithm to maximize the overall throughput, considering the maximum allowed degradation index as a constraint.

The role of Arrayed Waveguide Gratings in energy-efficient optical switching architectures

Optical Fiber Communication Conference, 2010

The power consumption of large IP routers is increasing too fast with the increase of Internet tr... more The power consumption of large IP routers is increasing too fast with the increase of Internet traffic. This power consumption can be reduced if Optical Switching Fabrics (OSFs) are used instead of electronic backplanes and interconnects. And Arrayed Waveguide Gratings (AWGs) exhibit interesting properties for the design and implementation of OSFs. The paper studies how OSFs based upon AWGs scale

Belief-Propagation-Assisted Scheduling in Input-Queued Switches

by M. Pretti and Davide Cuda

IEEE Transactions on Computers, 2000

ABSTRACT We consider the problem of scheduling packets transmission across the switching fabric i... more ABSTRACT We consider the problem of scheduling packets transmission across the switching fabric in an input-queued switch. In order to achieve maximum throughput, scheduling algorithms usually employ the queue length as a parameter for determining the priority to serve a given queue. Unfortunately, optimal schedulers are too complex to be implemented directly in hardware, which is the only viable solution in high-end switches, since scheduling decisions must be taken in very short time, of order of ns. Conversely, implement able algorithms, based on parallel and greedy decisions, are inefficient in terms of throughput. In this work we do not propose any new scheduling algorithm or switching architecture, but a novel scheme to optimize the performance of a pre-existing scheduler. Indeed, we propose to assist the scheduling decision by considering &quot;message&quot; values instead of queue lengths. Such messages are obtained by running an iterative parallel algorithm (efficiently implement able in hardware and fully compatible with pre-existing schedulers), based on a rigorous Belief-Propagation approach. We show that BP-assisted scheduling is able to boost the performance of a given scheduler, reaching almost optimal throughput, even under critical traffic scenarios.

Scalability of Optical Interconnects Based on Microring Resonators

IEEE Photonics Technology Letters, 2010

This paper investigates the use of optical microring resonators as switching elements in large op... more This paper investigates the use of optical microring resonators as switching elements in large optical interconnection fabrics. We introduce a simple physical-layer model to assess scalability in crossbar-and Benes-based architectures. We also propose a new dilated switching element that improves scalability to build fabrics of several Tbps of aggregate capacity.

Design and control of next generation distribution frames

Computer Networks, 2012

In today's access networks, the permutation of circuits connecting the subscriber lines to Plain ... more In today's access networks, the permutation of circuits connecting the subscriber lines to Plain Old Telephone Service (POTS) and to Digital Subscriber Line Access Multiplexers (DSLAMs) occurs in the Main Distribution Frame (MDF) and is still manually configured. However, new market regulations and new policies adopted by operators require increasingly more frequent permutations, making the manual configuration activity particularly expensive. Very recently, Automated MDFs (AMDF) have been developed to provide inexpensive and almost real-time switching capability. Our study, based on more than 50 years of research activities on architectures for circuit switching, is focused on overcoming the limits of classical architectures. In fact, strictly non-blocking multistage networks are too expensive, as a consequence of the large number of ports they require (sometimes exceeding 100,000). In addition, rearrangeable multistage networks can temporarily interrupt active circuits, affecting the performance of ADSL subscriber lines. As a possible solution to these problems, we propose the design of AMDFs based on Non-Interruptive Rearrangeable (NIR) networks. We show how to optimize the routing control to minimize the setup time of a circuit and to exploit output grouping. We believe that the solution described above is not only relevant for the theory of multistage interconnection networks, but also for the design and operation of large AMDFs.

Getting routers out of the core: Building an optical wide area network with