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We propose QoS-based routing methods for multi-hop LEO satellite networks aiming at minimising the number of link handovers per connection, while at the same time satisfying the QoS requirements. For the representation of the network topology as well as for the minimisation of connection re-routing attempts due to the connectivity changes, a graph-theoretical approach is used, where a new metric for inter-satellite links, called lifetime, is introduced. In addition to a QoS-based routing strategy where the best feasible path is found under multiple constraints, e.g. lifetime and delay, we also propose a distributed QoS-routing strategy, where a choice between a number of selected paths can be made based on particular QoS requirements.

This work proposes a distributed method for wavelength channel provisioning in multi-service WDM networks, where subject to constraints on wavelength routing such as transmission quality or resource availability, the best of the multiple feasible paths can be found. The numerical examples and simulation study of multi-service wavelength-routed networks under dynamic traffic conditions have shown the applicability of our methods for the optical network services yet to emerge.

In the previous chapter we designed a set of optimisation algorithms for service-specific connection accommodation. Here, we will show how to adopt the simulationbased approach from which we collect statistics for blocking probability, restorability and service quality, and based on which the optimisation on particular network design can be performed. As it will be shown in the following sections, the proposed strategies are widely applicable and are not restricted to any specific model or assumption.

This chapter is dedicated to an overview of the existing network and node architectures for wavelength routing necessary to understand the novel, QoS-based approaches that will be taken. Obviously, a broad area of different issues for control, network architecture, resource allocation, and policies can be associated with QoS-based routing. However, rather than addressing single architectural aspects, we will try to justify the necessity for QoS-based consideration of network performance, which is expected to enter the networking market in the short term as a natural progressive step for wavelength-routed networks. Therefore, before going into the basics of optical node and optical network architectures (a subject so far treated by a number of excellent books, scientific papers and experimental trials), a few important introductory words will be dedicated to the notion of QoS, a feature that is still missing in the existing works on wavelength routing.

In designing multimedia applications over a multi-service network, we face the problem of supporting applications that have QoS requirements. Thanks to the fruitful research efforts in high-speed networking and multimedia applications, there has been, however, significant progress in understanding of how to deliver a data throughput (i.e. packets) above a certain rate and within delay bounds. It is now common agreement that for real-time traffic, the delivery of the data packets in a correct order over a logical association between users is likely to follow the connectionoriented principle. For such a connection establishment, the wavelength-routing circuits are the natural candidates. In this context, given a set of constraints for an end-to-end connection, the question arises: what subset of constraints regarding the “end-to-end” QoS requirements will be taken into account for wavelength-routed connection accommodation, if any? The best QoS agreement is certainly end-to-end. However, this requires co-ordination across many network devices, which is a big network design challenge, expensive to build and difficult to manage (Figure 3-1). We will see later on that instead of this co-ordination across the multi-layer stacks, the QoS parameters are translated into the client network requirements for links, paths or signal quality constraints in the wavelength domain.

In this paper, we apply different restoration strategies for different optical network services in multi-service optical WDM networks according to the user requirements and availability of network resources. For that purpose optical network services provided to the user networks like SDH or ATM are classified according to the quality degree and restorability required. In particular, the restoration means dynamical reestablishing of circuits, which are generally dynamically or statically assigned. The numerical results for networks with a random restorable topology and four classes of service quality degree as well as for service-specific restoration methods are presented and studied on their applicability.

In this paper, the restoration strategies with QoS-guarantee for optical network services are introduced. For that purpose optical network services in WDM networks are classified according to the quality degree and restorability required. In particular, the self-healing aspects of service restoration are studied. The simulation results for networks with arbitrary topology and service quality degree as well as for service-specific restoration methods are presented and studied on their applicability.

In this paper, a novel approach for service accommodation in WDM networks is proposed. It is based on the classification of optical network services according to Quality-of-Service (QoS) to be guaranteed for a client network (typically, SDH or ATM). This principle is applied to node architectures and node main functions as well as to wavelength assignment. Various resource management heuristics for WDM optical networks are presented, where shifting of physical and logical resources in dynamically routed optical networks is minimised. Simulation results for an example network are presented for a demonstration of applicability of the proposed methods.

For handling signals in optical networks transparently, two different approaches for quality-of-service routing are proposed. The features of these approaches are discussed and simulation results for an example network with various kind of services with/without wavelength shifting are given.

PHOTON is one of the ACTS projects which aims at the development of selected concepts for the future transport network and at the implementation of its key functionalities in a field trial for demonstration of the feasibility and validation of the networking ideas. Within the project PHOTON the design of the all-optical nodes for the optical transport network will be demonstrated and verified in the PHOTON field trial called PHOTONET. In PHOTONET, a border crossing star network between Munich and Vienna via Passau will be implemented demonstrating transmission and cross- connection of optical frequency division multiplexed signals over already installed single mode fiber, spanning a distance of 524 km. The optical cross connect (OCC) builds the inner node of the network, connecting several FDM links (multichannel ports) and a number of single channel ports. The latter ones are used for adding local add/drop functionality to the OCC. The principal functions of an OCC are to perform all-optical cross-connecting, optical signal supervision, optical signal regeneration and add/drop functionality. The optical terminal multiplexer (OTMX) builds the interface between the client network and the optical transport network. The basic functions of the OTMX are the provision of the interface to the existing transport networks and to the novel leased optical channel service. The OCC and OTMX architectures are modular, so that any new requests for improvement of their functionality (as frequency conversion or fiber protection switching) can be easily achieved.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The emerging high-speed Ethernet is expected to take full advantage of the currently deployed optical infrastructure, i.e., optical transport network over wavelength division multiplexing (OTN/WDM) networks. Parallel transmission is a viable option towards this goal, as exemplified by several IEEE and ITU-T standards. The optical virtual concatenation protocol in the OTN layer defined in ITU-T G.709 enables high-speed Ethernet signals to be decoupled into low rate virtual containers. The multiple lane distribution layer defined in IEEE 802.3ba facilitates the optical parallel transmission by stripping Ethernet signals into multiple low rate lanes which can be mapped onto optical channels. In this paper, we propose a new optimization framework for parallel transmission in OTN/WDM networks to support high-speed Ethernet. We formulate the parallel transmission optimization as an integer linear programming problem encompassing three sub-problems: parallel wavelength routing and assignment, usage of electronic buffering for skew compensation, and bufferless parallel transmission. To reduce computational complexity, we deploy multi-objective evolutionary optimization. The numerical results show that parallel transmission in OTN/WDM networks is feasible, and optimal solutions can be obtained with minimum resource consumption and bufferless system design.

Load adaptive energy saving schemes for backbone IP networks use dynamic transport circuit services to adapt the active network resources to the current traffic demand in order to reduce the network's energy consumption. Recently, several approaches, categorized as Switch-off schemes, have been proposed which attempt to reduce the energy consumption of already existing networks by switching off IP ports and links during periods of low traffic. Although it has been shown that these schemes can notably decrease the network's energy consumption, they are prone to instabilities in the IP routing service and decreased resilience due to reduced connectivity, and they may induce monitoring reconfigurations. To address these challenges, we propose the Switch-On scheme in an IP-over-WDM network, where the network is designed so that the essential IP connectivity is maintained during low traffic periods while dynamic circuits are switched on in the optical layer to boost network capacity during periods of high traffic demand. Switching on the optical links during peak network loads can address some of the challenges associated with switching off IP ports and links during the low traffic periods. In this paper, we provide a comparative analysis of load adaptive energy saving schemes and present a discussion of the trade-off between energy efficiency and routing stability. The performance results and analytical study show that the multilayer approaches in IP-over-WDM networks carry significant potential for improvement in energy efficiency.

There is a wide consensus among service providers, operators, equipment vendors, and academics that the next decade will see highly evolving Internet and network transport architectures. Both circuit and packet switching technologies will be used in hybrid networks that will offer both IP packet and dynamic circuit services. A variety of switching technologies, such as multiprotocol label switching (MPLS), carrier Ethernet based switching, and wavelength-division multiplexed (WDM) optical switching, will be used to offer dynamic (virtual) circuit services, while IP routers will continue to be used for IP packet services. Integrated systems that offer both IP-layer forwarding and MPLS switching, or other combinations, will be used in these hybrid networks.

Major research activities carried out over the past ten years have succeeded in generating efficient routing methods for wavelength provisioning in optical wavelength-division-multiplexing (WDM) networks, where a centralized database was assumed to provide network-wide routing information. Although this is a valid assumption for some network applications, an attractive alternative is the ability to handle routing information in a decentralized fashion. This is of particular importance in the case of large multiservice networks, where the need for service-specific attributes may significantly affect the amount, type, and state of routing information. Here a new service-differentiated path-selection method with local routing information is proposed and used to analyze service guaranties in WDM networks with heterogeneous switching architectures, such as selectively regenerative. With our method, the routing information, related to transmission quality, reliability, and traffic conditions, is updated following a connection request, based on a local, autonomous, and service-differentiated characterization of the optical network elements. We present results for mesh networks consisting of transparent, short-reach networking segments interconnected by long-reach WDM links with electronicaly regenerative gateways, where different link types show different signal-to-noise degradation, reliability, and delay. We also discuss new perspectives to decentralized on-demand provision of wavelength channels in multiservice WDM networks with quality constraints.

The wide spread deployment of smart edge devices and applications that require real-time data processing, have with no doubt created the need to extend the reach of cloud computing to the edge, recently also referred to as Fog or Edge Computing. Fog computing implements the idea of extending the cloud where the "things" are, or in other words, improving application performance and resource eciency by removing the need to processing all the information in the cloud, thus also reducing bandwidth consumption in the network. Fog computing is designed to complement cloud computing, paving the way for a novel, enriched architecture that can benet from and include both edge(fog) and cloud resources. From a resources perspective, this combined scenario requires resource continuity when executing a service, whereby the assumption is that the selection of resources for service execution remains independent of their physical location. This new resources model, i.e., resource continuity, has gained recently signicant attention, as it carries potential to seamlessly providing a computing infrastructure from the edge to the cloud, with an improved performance and resource eciency. In this paper, we study the main architectural features of the managed resource continuity, proposing the foundation of a coordinated management plane responsible for resource continuity provisioning. We study an illustrative example on the performance benets in relationship to the size of databases with regard to the proposed architectural model.

The recent advances in cloud services technology are fueling a plethora of information technology innovation, including networking, storage, and computing. Today, various flavors have evolved of IoT, cloud computing, and so-called fog computing, a concept referring to capabilities of edge devices and users’ clients to compute, store, and exchange data among each other and with the cloud. Although the rapid pace of this evolution was not easily foreseeable, today each piece of it facilitates and enables the deployment of what we commonly refer to as a smart scenario, including smart cities, smart transportation, and smart homes. As most current cloud, fog, and network services run simultaneously in each scenario, we observe that we are at the dawn of what may be the next big step in the cloud computing and networking evolution, whereby services might be executed at the network edge, both in parallel and in a coordinated fashion, as well as supported by the unstoppable technology evolution. As edge devices become richer in functionality and smarter, embedding capacities such as storage or processing, as well as new functionalities, such as decision making, data collection, forwarding, and sharing, a real need is emerging for coordinated management of fog-to-cloud (F2C) computing systems. This article introduces a layered F2C architecture, its benefits and strengths, as well as the arising open and research challenges, making the case for the real need for their coordinated management. Our architecture, the illustrative use case presented, and a comparative performance analysis, albeit conceptual, all clearly show the way forward toward a new IoT scenario with a set of existing and unforeseen services provided on highly distributed and dynamic compute, storage, and networking resources, bringing together heterogeneous and commodity edge devices, emerging fogs, as well as conventional clouds. Introduction: The Scenario

We address the issues of inter-domain optical service provisioning with carrier-grade Ethernet and propose a multi-layer PCE based control plane architecture to implement adaptive advance reservation, which can significantly improve resource utilization and reduce blocking.