The goal of the SEASON project [1] is to design and validate a transport network infrastructure able to support beyond 5G and new emerging services, relying on the joint usage of Multi-Band and SDM, spanning the access, aggregation, and metro/long-haul segments, supporting the requirements for x-haul, further integrating the packet/optical and computing layers. The targeted SEASON architecture considers these innovations in addressing sliceable Bandwidth Variable Transceivers (S-BVTs) enabling Point-to-MultiPoint (P2MP) along with the integration of (coherent) pluggable optical modules on open packet/optical white boxes (open devices with hardware and software - referred to as the Network Operating System, - decoupling and providing open control and management interfaces), smart Network Interface Cards (NICs) or the latest generation Data Processing Units (DPU). In this paper, a multi-granular MBoverSDM modular and flexible Optical Switch architecture is presented, that can simplify the node design and enhance switching capabilities in SEASON high capacity packet transport network. Figure 1 displays the node architecture integrated with the RAN, which will be exploited to coordinate user-cell association and latency enforcement in the optical access based on achievable end-to-end latency. Such a node design is capable of dynamically route and add/drop traffic while potentially increasing the switching capacity in a flexible manner. Each layer can include different technology options such as WSSs and/or passive filters for band/spatial multiplexing and demultiplexing, which will offer different levels of flexibility. In the below figure, we depict a 3 rd order nodal degree, covering three directions (North, East, and West), in each of which three pairs of optical fibers and three spectral bands (S, C, and L) per fiber are rolled out. This design enables switching at the spectral band level as well as at the wavelength level, facilitated by individual-band WSSs. The node design integrates all essential optical components, including band filters (BF), amplifiers, spatial Optical Cross-Connector (S-OXC) switches, WSSs, and A/D modules. These components are interconnected to establish a modular colorless-directionless (CD) MBoverSDM node architecture, but a colorless-directionless-contentionless (CDC) architecture could be easily implemented by just removing the 1x20 WSS connected to the contentionless NxN WSS or substituting it with additional contentionless MxN WSS.

Power consumption of devices and network functionalities in optical infrastructures is reviewed. Then, possible short-, medium-, and long-term solutions to reduce and make energy consumption scalable are discussed.

This study investigates the use of a reconfigurable multi-functional reprogrammable silicon chip as an add/drop network device for a sliceable bandwidth variable transceiver. Software-Defined Networking (SDN) with NETCONF/YANG protocol is used for control and management, leveraging REST API to facilitate communication and coordination between the device local controller and the silicon chip-integrated device.

This special issue contains a collection of five research articles on the advances in multi-band optical networks, including the vision of vendors and telecom operators, the migration from single-band to multi-band, methods for quality of transmission, and the control of multi-band optical networks.

Next generation 5G services will require accurate service level verification including the packet-optical metro/aggregation segment. Network telemetry enables such accurate monitoring exploiting in-band and postcard telemetry technologies. However, the massive collection of telemetry data from the network and its processing represent a potential bottleneck subject to scalability issues. In this paper, we propose a two-stage telemetry collector by offloading the postcard telemetry reports processing and aggregation to a programmable P4 switch performing aggregation and correlation to be potentially per-formed at wirespeed. The experimental evaluation highlights the benefits in terms of reduced CPU and bandwidth requirements at the telemetry server.

The H2020 METRO-HAUL European project has architected a latency-aware, cost-effective, agile, and programmable optical metro network. This includes the design of semidisaggregated metro nodes with compute and storage capabilities, which interface effectively with both 5G access and multi-Tbit/s elastic optical networks in the core. In this paper, we report the automated deployment of 5G services, in particular, a public safety video surveillance use case employing low-latency object detection and tracking using on-camera and on-the-edge analytics. The demonstration features flexible deployment of network slice instances, implemented in terms of European Telecommunications Standards Institute (ETSI) network function virtualization network services. We summarize the key findings in a detailed analysis of end-to-end quality of service, service setup time, and soft-failure detection time. The results show that the round-trip time over an 80 km link is under 800 µs and the service deployment time is under 180 s.

Few Mode Fibers (FMF) and Space DivisionMultiplexing (SDM) are an attractive solution to offer high capacity in optical networks. Although transmission along FMF presents several issues mainly due to the cross-talk among modes, the use of Multiple Input Multiple Output (MIMO) coherent receivers permits to limit the impact of such physical impairment. However, the complexity of MIMO is not negligible (especially with a large number of modes) and the spatial modes must cover the same path, thus limiting network flexibility, e.g., routing modes along different paths is not admitted. In this paper we exploit the concept of Mode-Group Division Multiplexing (MGDM) and we investigate the network architecture and provisioning supporting MGDM. Modes are divided in groups: the modes within a group are co-routed and received with a reduced-complexity MIMO receiver, while the different groups can be routed along different paths. Different node architectures supporting MGDM are presented taking in account state-of-the-art components and devices, even commercially available on the market. A quality of transmission (QoT) model is also presented accounting to the inter mode group crosstalk, that cannot be neglected in the reach evaluation. QoT is exploited by a proposed connection provisioning scheme for MGDM. Simulations are carried out in metro/rural network scenarios with different link span lengths. Simulations show high throughput increase while limiting the complexity of receivers.

We report the automated deployment of 5G services across a latency-aware, semi-disaggregated, and virtualized metro network. We summarize the key findings in a detailed analysis of end-to-end latency, service setup time, and soft-failure detection time.

Next generation networks are evolving towards multi-layer scenario, where packet and optical domains are coupled to provide high dynamicity and high throughput. Regarding the optical domain, the white-box concept (i.e., the disaggregated network approach) is promising to break the vendor lock-in for optical transmission solutions. At the packet domain, since standard OpenFlow-based SDN techniques showed limited functionalities (i.e., missing stateful capabilities pipelining), novel P4-based solutions are emerging as candidate framework, envisaging the dynamicity of the traffic and the hardware programmability paradigm. In this scenario, the telemetry functionality is becoming a promising solution for network monitoring, where data is efficiently streamed from network devices. In fact, in order to meet the service SLA requirements, next generation networks will leverage on advanced monitoring features, based on streaming techniques, allowing the control/management system to detect link failures and avoid traffic congestion. In this paper, we propose an experimental validation of a telemetry-based monitoring system in a multi-layer network. For the optical domain, we rely on an open-source implementation of an OpenConfig NETCONF agent enhanced with telemetry, in order to enable the sample data streaming of a number of key transmission parameters. For the packet layer, we exploit the P4 in-band telemetry, providing information on the end-to-end experienced latency and interfaces throughput. The monitoring system, enhanced with a proper GUI based on Grafana, is able to request the streaming of one or more selected parameter(s), on demand and with proper granularity, from different network domains. The implemented telemetry-based monitoring system has been experimentally validated over a multi-layer network encompassing EON and two P4 aggregation switches, highlighting the main functionalities and the effectiveness of the proposed solution.

A novel framework based on blockchain is proposed to provide trusted SLA accounting. Extensions to SDN ONOS controller successfully assess controversial SLA degradations responsibilities upon failure events in a multi-vendor OpenROADM-based white box scenario.

Traffic monitoring through in-band telemetry is extended up to the User Equipment (UE), providing accurate e2e latency measurement. The UE becomes aware of its experienced service performance, enabling autonomous operations for faster automatic source-based Edge-Cloud steering.

Highly accurate and reliable optical signal tracking is proposed that estimates sub-GHz laser drift failures by analyzing spectra acquired by cost-effective coarse-granular OSAs. Its application on PAM4 systems in filterless metro networks brings added robustness.

A first demonstration of P4-based virtual network function (VNF) for latency-critical services is presented. The VNF exploits P4 In-band telemetry to dynamically enforce per-packet QoS priority according to cumulated latency performance.

Operators' network management continuously measures network health by collecting data from the deployed network devices; data is used mainly for performance reporting and diagnosing network problems after failures, as well as by human capacity planners to predict future traffic growth. Typically, these network management tools are generally reactive and require significant human effort and skills to operate effectively. As optical networks evolve to fulfil highly flexible connectivity and dynamicity requirements, and supporting ultra-low latency services, they must also provide reliable connectivity and increased network resource efficiency. Therefore, reactive human-based network measurement and management will be a limiting factor in the size and scale of these new networks. Future optical networks must support fully automated management, providing dynamic resource re-optimization to rapidly adapt network resources based on predicted conditions and events; identify service degradation conditions that will eventually impact connectivity and highlight critical devices and links for further inspection; and augment rapid protection schemes if a failure is predicted or detected, and facilitate resource optimization after restoration events. Applying automation techniques to network management requires both the collection of data from a variety of sources at various time frequencies, but it must also support the capability to extract knowledge and derive insight for performance monitoring, troubleshooting, and maintain network service continuity. Innovative analytics algorithms must be developed to derive meaningful input to the entities that orchestrate and control network resources; these control elements must also be capable of proactively programming the underlying optical infrastructure. In this article, we review the emerging requirements for optical network management automation, the capabilities of current optical systems, and the development and standardization status of data models and protocols to facilitate automated network monitoring. Finally, we propose an architecture to provide Monitoring and Data Analytics (MDA) capabilities, we present illustrative control loops for advanced network monitoring use cases, and the findings that validate the usefulness of MDA to provide automated optical network management.

Next-generation edge nodes interfacing innovative IT clusters, 5G fronthaul, and internet of things (IoT) gateways to the optical metro/core network will require advanced and dynamic online quality of service (QoS) per-flow traffic treatment, assuring ultra-low latency requirements. However, current software-defined networking (SDN) implementations (e.g., OpenFlow) do not support forwarding procedures based on the network state, profile variations, and the history of flow statistics at the node level. Currently, such procedures require intervention by the SDN controller, leading to scalability issues and additional latency in data plane forwarding. Moreover, severe security challenges are expected to affect such nodes and threaten IT resources. Thus, increasing bandwidths will require direct deep packet inspection to avoid involvement of the SDN controller, as performed currently, or dedicated and costly security systems. This paper leverages on the potential of the programming protocol-independent packet processors (P4) open source language, recently introduced by the inventors of OpenFlow, to program the data plane structure and behavior of an SDN switch. P4 is able to instantiate custom pipelines and stateful objects, enabling complex workflows, user-defined protocols/headers, and finite state machines enforcement. Moreover, P4 allows portable implementations over different hardware targets, thus opening the way to open source fully programmable devices. Special effort is dedicated to motivate and apply P4 within a multilayer edge scenario, proposing the architecture and the applicability of an SDN P4-enabled packet-over-optical node. Moreover, three specific multilayer use cases covering dynamic traffic engineering (TE) (e.g., traffic offload and optical bypass) and cybersecurity (e.g., distributed denial of service port scan) are discussed and addressed through P4-based solutions. Experimental evaluations have been conducted over a multilayer SDN network exploiting reference P4 software switches (i.e., the behavioral model version 2, or BMV2) and field-programmable gate arrays (FPGAs) at 10 gigabit Ethernet optical interfaces. Extensive results report effective dynamic TE and cybersecurity mitigation enforcement at P4 switches without any controller intervention, showing excellent scalability performance and overall latencies practically in line with current commercial OpenFlow switches.

We propose the use of blockchain for the ratification of QoT performance in multi-domain networks, where a transparent lightpath traverses several domains. End-to-end QoT is guaranteed by transferring “OSNR blocks” among domains' controllers. Experimental demonstration shows the feasibility of the method and its scalability.

We propose an approach based on local reconfigurations for restoration in disaggregated SDN optical networks. The approach is innovative since it does not involve the controller during the failure without requiring distributed path computation intelligence.

The recent interest in the upgrade and enhancements of metro transport networks and the availability of transponder cards with coherent receivers is opening the way to filterless solutions employing only passive splitters/couplers and optical amplifiers, potentially achieving significant capital expeditures and operating expenditures savings. However, the filterless option suffers from inefficiencies, mainly due to the broadcasting constraint and the reduced optical reach. To overcome such limitations, this paper proposes three complementary strategies to upgrade optical filterless metro networks (FMN). First, the number of supported channels is incremented by exploiting the full C + L -band. To this end, two design architectures (i.e., Single and Dual Region) are proposed and evaluated, targeting double capacity with respect to the standard C-band and an upgrade to cost reduction. Second, we investigate a dual-architecture solution, extending metro deployments with a low-cost filterless and unamplified L-band system. Its design trade-offs are evaluated to determine its suitability in providing direct low-latency connectivity between metro-access nodes with the aim of supporting edge-computing platforms. Finally, the flexibility of the FMN is extended by introducing disaggregated transponders with different bitrates (i.e., 100 Gbps and 400 Gbps) and configurable transmission parameters, such as the modulation format and the forward error correction). Such flexibility is exploited through the extension of the OpenConfig YANG model of the optical line system, thus enabling automatic spectrum and transmission parameter assignment by means of a centralized software-defined-network controller and achieving better resource utilization. Simulation and experimental results are provided, showing the effectiveness and the potential impact of filterless metro solutions in future deployments and low-cost network upgrades supporting edge/fog clusters and 5G.

The advent of softwarization implies a re-thinking of network design and management that positively impacts on service provisioning and maintenance efficiency. In particular, Software Defined Networking and Network Function Virtualization introduce abstraction techniques that are suitable for an easy and efficient deployment of service chain and for the use of general purpose hardware devices. The introduction of these paradigms in the railway domain is challenging due to its strict service and safety requirements, however it represents a promising approach enabling a disruptive improvement of the management systems and paving the way for next-generation railway control systems.This paper discusses and proposes the adoption of SDN/NFV (Software Defined Networks/Networks Function Virtualization) framework in railway control networks. In particular, some possible promising directions of investigation are drawn considering service orchestration and edge-based NFV services. Furthermore, two different applications are described focusing on SDN and NFV, respectively. An improved SDN failure recovery mechanism is proposed and evaluated showing the improvement in terms of recovery time. Instead, the introduction of configurable orchestration systems aiming to dynamically instantiate required services on Virtual Machines directly in the railway peripheral places by means of edge computing solutions for maintenance operations of peripheral assets is described and discussed.