We evaluate the advantages of using the extra dimension introduced by space-division multiplexing (SDM) for dynamic bandwidth-allocation purposes in a flexible optical network. In that respect, we aim to compare spectral and spatial super-channel (Sp-Ch) allocation policies in an SDM network based on bundles of SMFs (to eliminate coupling between spatial dimensions from the study) and to investigate the role of modulation format selection in the blocking probability performance with an emphasis on the spectral efficiency (SE)/reach tradeoff for different multiline-rate scenarios, created either by changing the number of sub-channels (Sb-Ch), or by employing different modulation formats. Our network-performance results show that DP-8QAM -in a multichannel (MC) single-modulation-format system assuming ITU-T 50-GHz WDM Sb-Ch spectrum occupation-offers the best compromise between SE and optical reach for both spectral and spatial Sp-Ch allocation policies. They also reveal that an MC multimodulation-format system improves the network performance, particularly for spectral Sp-Ch allocation with Sb-Ch spectrum occupation of 37.5 GHz on the 12.5-GHz grid. Additionally, as another important contribution of the paper, we investigate, for spatial Sp-Ch allocation, the performance of several SDM switching options: independent switching (InS), which offers highest flexibility, joint-switching (JoS), which routes all spatial modes as a single entity, and fractional-joint switching, which separates out the spatial modes into sub-sets of spatial modes which are routed independently. JoS is proved to offer a similar performance to that of InS for particular network load profiles, while allowing a significant reduction in the number of wavelength-selective switches.

Volumetric distributed Denial-of-Service (DDoS) attacks have become one of the most significant threats to modern telecommunication networks. However, most existing defense systems require that detection software operates from a centralized monitoring collector, leading to increased traffic load and delayed response. The recent advent of Data Plane Programmability (DPP) enables an alternative solution: threshold-based volumetric DDoS detection can be performed directly in programmable switches to skim only potentially hazardous traffic, to be analyzed in depth at the controller. In this paper, we first introduce the BACON data structure based on sketches, to estimate per-destination flow cardinality, and theoretically analyze it. Then we employ it in a simple in-network DDoS victim identification strategy, INDDoS, to detect the destination IPs for which the number of incoming connections exceeds a pre-defined threshold. We describe its hardware implementation on a Tofino-based programmable switch using the domain-specific P4 language, proving that some limitations imposed by real hardware to safeguard processing speed can be overcome to implement relatively complex packet manipulations. Finally, we present some experimental performance measurements, showing that our programmable switch is able to keep processing packets at line-rate while performing volumetric DDoS detection, and also achieves a high F1 score on DDoS victim identification.

Flexi-grid technology has emerged as the evolution of fixed-grid DWDM core optical networks, enabling more efficient utilization of spectral resources and leading to higher overall network throughput. However, it suffers from an aggravated form of the spectrum fragmentation problem that affects fixed-grid networks. This work presents a novel path-based metric to better evaluate the fragmentation of spectral resources in flexi-grid optical networks, which considers that not all links of a path may contain enough free frequency slots and the likelihood that an end-to-end spectral void is large enough to house a connection. Furthermore, two families of heuristic routing and spectrum allocation (RSA) algorithms that preventively attempt to minimize the value of an input fragmentation metric are presented. These are used to evaluate the effectiveness of multiple metrics, both introduced in this work and from the existing literature, via simulations. We find that both proposed families can perform better, in terms of blocking probability and achievable network throughput, than the well-known $K$-shortest paths routing with a first fit spectrum allocation policy, with one of them trading performance for lower complexity, and that the proposed fragmentation metric outperforms the existing ones.

Space division multiplexing (SDM) is a promising approach to overcome the looming fiber capacity crunch. Joint and fractional joint switching (JoS and FJoS) architectures, which switch multiple spatial dimensions together as atomic units, have been proposed to reduce the cost of implementing SDM and cater to strongly coupled transmission media. However, they have been shown to impose significant penalties to overall network performance, at least when many relatively small connections are used in the context of uncoupled spatial dimensions, while performing nearly as well as the independent switching (InS) architecture if the average connection size is sufficiently large to efficiently exploit their increased granularity. In this work we tackle the performance penalty that JoS and FJoS architectures impose on SDM networks with uncoupled spatial dimensions compared to InS, by proposing two novel routing, space, and spectrum allocation (RSSA) heuristics that effectively share jointly switched resources, adapted to use different types of SDM reconfigurable optical add/drop multiplexer architectures requiring only a small additional cost. We investigate the performance of these new RSSA algorithms compared to an existing one under several traffic conditions and models using simulations. We find that our proposals can achieve significant improvements in the performance of SDM networks carrying large numbers of relatively small connections, up to parity of performance with InS designs, at a lower implementation cost, under all traffic conditions under study, including different average connection sizes and size diversity.

The capacity benefits of flexi-grid optical networks are limited by the finite amount of bandwidth of standard fibers, and will not be able to scale indefinitely. Space Division Multiplexing (SDM) has emerged as a promising technology to overcome this limitation. In this preliminary work we give an overview of current SDM technologies, covering coupled and non-coupled SDM networks, and of the possibilities and limitations they bring to the problem of Routing, Space and Spectrum Allocation (RSSA). We focus on the trade-offs between spectral efficiency and amount of transmission devices enabled by SDM technologies, presenting a number of preliminary heuristic policies to solve RSSA, and evaluating them in the context of dynamic traffic by means of simulations. We show that different heuristics can optimize different aspects of RSSA, and that one strikes a reasonable balance.

We describe two mixed-integer linear programming formulations, one a faster version of a previous proposal, the other a slower but better performing new model, for the design of Quantum Key Distribution (QKD) sub-networks dimensioned to secure existing core fiber plants. We exploit existing technologies, including non-quantum repeater nodes and multiple disjoint QKD paths to overcome reach limitations while maintaining security guarantees. We examine the models’ performance using simulations on both synthetic and real topologies, quantifying their time and resulting QKD network cost compared to our previous proposal.