Michele Savi

3-Level Integrated Hybrid Optical Network (3LIHON) to Meet Future QoS Requirements

This paper presents a new hybrid network architecture including different transport technologies to support a wide range of services. In particular the proposed hybrid network provides three service levels, and a possible set of foreseeable services with different QoS needs is mapped into these levels to show the effectiveness of the hybrid networking in managing multi-service requests. In the switching nodes of the network, each service level is associated to a different switching technology, thus optimizing the switch implementation. In the nodes of the network, the service levels are distinguished based on optical encoding techniques, while an output collision stage manages the access to the output wavelengths. Performance studies show the effectiveness of the output collision mechanism.

Multifiber Shared-Per-Wavelength All-Optical Switching: Architectures, Control, and Performance

A new wavelength converter sharing strategy for multifiber optical switches, namely shared-per-wavelength (SPW), which employs wavelength converters with fixed input wavelengths is presented. The aim is to reduce switch costs by using simpler optical components and low complexity space switching matrices. Practical implementations of both the well-known shared-per-node (SPN) and the new SPW schemes are presented, as well as the related scheduling algorithms to manage optical packet forwarding in synchronous scenario. An analytical model to evaluate blocking performance of the SPN architecture is also provided. Results show the accuracy of the model in the range of interest for switch design. The proposed architectures are compared in terms of performance and number of optical components employed. The SPW approach is shown to save a large number of semiconductor optical amplifier gates with respect to the SPN one when the number of fibers per interface is suitably not too high. In these cases, the SPW architecture requires a number of wavelength converters higher than the SPN, but simpler, being their inputs tuned on a single wavelength.

Sharing wavelength converters in multistage optical packet switches

This paper describes a multistage switch based on the broadcast-and-select principle. It implements shared per node wavelength conversion for contention resolution in optical packet-switched networks. A novel scheduling algorithm is proposed to control packet forwarding in synchronous context. An analytical model is provided to calculate the packet loss probability related to the multistage configuration. Results show how the sharing of wavelength converters impacts on node performance, and provide a meaningful support for cost-performance benchmarking studies

Shared-per-wavelength asynchronous optical packet switching: A comparative analysis

This paper compares four different architectures for sharing wavelength converters in asynchronous optical packet switches with variable-length packets. The first two architectures are the well-known shared-per-node (SPN) and shared-per-link (SPL) architectures, while the other two are the shared-per-input-wavelength (SPIW) architecture, recently proposed as an optical switch architecture in synchronous context only, which is extended here to the asynchronous scenario, and an original scheme called shared-per-output-wavelength (SPOW) architecture that we propose in the current article. We introduce novel analytical models to evaluate packet loss probabilities for SPIW and SPOW architectures in asynchronous context based on Markov chains and fixed-point iterations for the particular scenario of Poisson input traffic and exponentially distributed packet lengths. The models also account for unbalanced traffic whose impact is thoroughly studied. These models are validated by comparison with simulations which demonstrate that they are remarkably accurate. In terms of performance, the SPOW scheme provides blocking performance very close to the SPN scheme while maintaining almost the same complexity of the space switch, and employing less expensive wavelength converters. On the other hand, the SPIW scheme allows less complexity in terms of number of optical gates required, while it substantially outperforms the widely accepted SPL scheme. The authors therefore believe that the SPIW and SPOW schemes are promising alternatives to the conventional SPN and SPL schemes for the implementation of next-generation optical packet switching systems.

Multistage Shared-Per-Wavelength Optical Packet Switch: Heuristic Scheduling Algorithm and Performance

This paper describes an optical switch architecture based on the shared-per-wavelength strategy for contention resolution in the wavelength domain. This strategy impacts on wavelength converters requirements and switch organization, by allowing to obtain cost saving. The general sharing concept is first introduced and the related practical solution as a multistage switch architecture is presented and thoroughly analyzed in terms of performance, control and cost perspectives. Heuristic scheduling to manage packet forwarding in a synchronous context is developed and discussed in terms of computational complexity. A simple accurate analytical model is developed and validated against simulation to numerically evaluate packet loss performance of the shared-per-wavelength switch. The main achievement of the work is represented by the proposal of a feasible approach which leads to remarkable cost saving in terms of optical gates and wavelength converters under the conditions outlined.

Standard-based approach to programmable hybrid networks

Programmable hybrid networks are considered in this article as a challenge to deploy flexible solutions for next-generation networks. A modular programmable router architecture, which takes advantage of emerging standards, is proposed to support dynamic management and configuration capabilities of network resources and services. The new node design concepts allow vendor-independent development of hybrid router functionalities and possible investigation of new standard interfaces. Validation of the proposed approach is proven in an open source software router context, emulating a hybrid circuit/packet service based on optical switching technology. The software emulator obtained allows programmable hybrid router functionalities to be tested at different levels of abstraction and with different modeling granularities, and is able to represent both logical and physical aspects.

Service-oriented multi-granular optical network testbed

This paper presents a service-oriented multi-granular multi-format network demonstrator. Service-oriented wavelength and sub-wavelengthnetwork connection establishment is being demonstrated by utilising SOON-JIT protocols to support VoD HD and Quad-HD multi-media applications.

Packet loss analysis of shared-per-wavelength multi-fiber all-optical switch with parallel scheduling

This paper discusses a multi-fiber all-optical switch which shares wavelength converters for contention resolution. The proposed switch architecture employs fixed-input/tunable-output wavelength converters (expected to be less complex than tunable-input/tunable-output ones). The space switching matrix is modular and simple with respect to switching architectures with different wavelength converters sharing schemes (i.e. shared-per-node architecture). A parallel scheduling algorithm is defined to control optical packet forwarding in a synchronous scenario as well as an analytical model to evaluate packet loss performance. The analytical model is validated against simulation and previous analysis and the results obtained show good accuracy in most cases of interest for optical switch design.

OPN06-2: Performance of Scheduling Algorithms in Multi-Stage Optical Packet Switches with Sparse Wavelength Converters

This paper describes the scheduling algorithms to control the optical packet forwarding in a multi-stage switch based on the broadcast-and-select principle. The aim of control algorithms is to fully exploit switch resources while avoiding contention in the wavelength and space domains. A multi-stage switch based on the shared per node wavelength conversion scheme is considered in a synchronous context. An analytical model is provided to calculate the packet loss probability in relation to different reference traffic scenarios. Results show how the sharing of wavelength converters impacts on node performance depending on the scheduling algorithm applied, and provide a meaningful support for optical packet switch design.

Data-plane architectures for multi-granular OBS network

This paper presents multi-granular OBS node architectures able to manage multiservice traffic according to the required Quality-of-Service (QoS). These nodes exploit fast and slow switching devices to obtain scalable and cost-effective network.