I. de Miguel

Next-generation 100-gigabit metro ethernet (100 GbME) using multiwavelength optical rings

This paper investigates the challenges for developing the current local area network (LAN)-based Ethernet protocol into a technology for future network architectures that is capable of satisfying dynamic traffic demands with hard service guarantees using high-bit-rate channels (80...100 Gb/s). The objective is to combine high-speed optical transmission and physical interfaces (PHY) with a medium access control (MAC) protocol, designed to meet the service guarantees in future metropolitan-area networks (MANs). Ethernet is an ideal candidate for the extension into the MAN as it allows seamless compatibility with the majority of existing LANs. The proposed extension of the MAC protocol focuses on backward compatibility as well as on the exploitation of the wavelength domain for routing of variable traffic demands. The high bit rates envisaged will easily exhaust the capacity of a single optical fiber in the C band and will require network algorithms optimizing the reuse of wavelength resources. To investigate this, four different static and dynamic optical architectures were studied that potentially offer advantages over current link-based designs. Both analytical and numerical modeling techniques were applied to quantify and compare the network performance for all architectures in terms of achievable throughput, delay, and the number of required wavelengths and to investigate the impact of nonuniform traffic demands. The results show that significant resource savings can be achieved by using end-to-end dynamic lightpath allocation, but at the expense of high delay.

A Cognitive Quality of Transmission Estimator for Core Optical Networks

We propose a cognitive Quality of Transmission (QoT) estimator for classifying lightpaths into high or low quality categories in impairment-aware wavelength-routed optical networks. The technique is based on Case-Based Reasoning (CBR), an artificial intelligence technique which solves new problems by exploiting previous experiences, which are stored on a knowledge base. We also show that by including learning and forgetting techniques, the underlying knowledge base can be optimized, thus leading to a significant reduction on the computing time for on-line operation. The performance of the cognitive estimator is evaluated in a long haul and in an ultra-long haul network, and we demonstrate that it achieves more than 98% successful classifications, and that it is up to four orders of magnitude faster when compared with a non-cognitive QoT estimator, the Q-Tool.

Implementation of a PID controller for the bandwidth assignment in long-reach PONs

In this paper a proportional-integral-derivative (PID) controller to efficiently allocate bandwidth in high coverage passive optical networks (PONs) is presented. The novelty of this proposal relies on the fact that this is the first proposal to use a PID to control a network parameter in PONs. As the PID takes into account present, past and possible future errors in the bandwidth adjustment, this self-adapting technique results in a very robust process. Simulation results exhibit that not only is it faster and more stable than other algorithms, but also it auto-adapts the resources very efficiently when facing real time changes in the network parameters or in the bandwidth conditions. In fact, the standard deviation of the difference between the allocated and the guaranteed bandwidth is reduced by up to 50% and the convergence speed is up to four times quicker than other proposals.

Timescale analysis for wavelength-routed optical burst-switched (WR-OBS) networks

The relationship of three timing parameters in the WR-OBS network architecture has been identified and investigated, to quantify the limits on the operation of a dynamic network. An adaptive burst assembler at the network edge provides an accurate estimation of the maximum edge delay whilst preventing buffer overflow, depending only on the mean and variance of incoming traffic. The round-trip time defines the achievable wavelength re-use under dynamic network operation, which could be as large as 20 for the example shown. The processing and queueing latency in the network control node links all three parameters and imposes a lower bound to the edge delay for a given number of edge routers. The unlimited burst size (UBS) scheme not only overcomes the main limitation of many OBS approaches-excessive burst loss for high network loads, but also reduces latency with increasing load, potentially ensuring adaptive network operation over a wide range of loads.

A bandwidth assignment polling algorithm to enhance the efficiency in QoS long‐reach EPONs

A novel polling algorithm is proposed to provide subscriber differentiation at the upstream channel in long-reach EPONs. As operators and service providers prefer to operate at loads with no congestion and losses, the developed algorithm has been designed to improve the efficiency for those loads at which the network is likely to work. This new scheme permits to anticipate the transmission of some packets in order to take advantage of the wasted bandwidth between consecutive transmissions of ONUs. As a result, not only does this algorithm behave alike other polling algorithms for high loads, but it also improves the efficiency at low and medium loads, leading to a reduction in the mean packet delay. The new algorithm has been tested in different scenarios, motivated by the increasing interest in enlarging the long-reach EPON distances. Simulation results show that as the distance increases, the algorithm achieves a significant reduction of the mean packet delay for an extended range of loads. Copyright

Analysis of burst scheduling for dynamic wavelength assignment in optical burst-switched networks

We discuss the benefits and limitations of the dynamic RWA in a centralised optical burst-switched network architecture. We present systematic comparison between the performance of the dynamic and static RWA in terms of QoS provisioning and bandwidth utilisation. Additionally, we consider a new component in the WROBS architecture, namely the request scheduler. We demonstrate that its application to the dynamic RWA significantly improves the performance of the WROBS.

Cognition to design energetically efficient and impairment aware virtual topologies for optical networks

“Greening the Internet” is an important research topic in the last years. The Internet capacity and energy consumption have increased, and the utilization of design and operation techniques to reduce this consumption are a must. In this paper, we present a multiobjective genetic algorithm to design virtual topologies for reconfigurable wavelength-routed optical networks with the aim of reducing both the energy consumption and the network congestion while ensuring that the lightpaths of the virtual topologies fulfill quality of transmission requirements. Moreover, we also present another version of that method enhanced with cognitive techniques, and we show, by means of simulation, the performance advantages brought when introducing these cognitive techniques.

A control plane framework for future cognitive heterogeneous optical networks

Future optical networks are expected to provide an efficient infrastructure able to deliver a growing number of services, which have to meet various requirements in terms of quality of service. To achieve this objective the physical network is going through an evolution aimed at increasing its flexibility in terms of spectrum utilization and its level of heterogeneity in terms of supported services and technologies. In this context, cognitive optical networks represent a viable solution to fill the gap between the intelligence required by the future networks and the current optical technology. This paper proposes a control plane framework developed to coordinate the interactions among the elements of the future cognitive optical networks. The building blocks of the framework and the involved protocols are presented. Moreover, this paper provides an insight of the control plane issues related to the introduction of the flexible optical technology.

Multiobjective Genetic Algorithm to Design Cost-Efficient Wavelength-Routed Optical Networks

A new algorithm, GAPDELT, is presented to jointly design the resource provisioning and the logical topology of wavelength-routed optical networks. GAPDELT is based on genetic algorithms and uses Pareto optimality to reduce both the network congestion and the number of resources employed. By means of a simulation study, we show that GAPDELT designs a set of good alternatives that achieve up to 50% of reduction in terms of congestion or 75% of reduction in the number of transmitters and receivers required when compared with another well-known

Cognitive dynamic optical networks

Cognitive networks are a promising solution for the control of heterogeneous optical networks. We review their fundamentals as well as a number of applications developed in the framework of the EU FP7 CHRON project.