102 research outputs found

    Virtualisation and resource allocation in MECEnabled metro optical networks

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    The appearance of new network services and the ever-increasing network traffic and number of connected devices will push the evolution of current communication networks towards the Future Internet. In the area of optical networks, wavelength routed optical networks (WRONs) are evolving to elastic optical networks (EONs) in which, thanks to the use of OFDM or Nyquist WDM, it is possible to create super-channels with custom-size bandwidth. The basic element in these networks is the lightpath, i.e., all-optical circuits between two network nodes. The establishment of lightpaths requires the selection of the route that they will follow and the portion of the spectrum to be used in order to carry the requested traffic from the source to the destination node. That problem is known as the routing and spectrum assignment (RSA) problem, and new algorithms must be proposed to address this design problem. Some early studies on elastic optical networks studied gridless scenarios, in which a slice of spectrum of variable size is assigned to a request. However, the most common approach to the spectrum allocation is to divide the spectrum into slots of fixed width and allocate multiple, consecutive spectrum slots to each lightpath, depending on the requested bandwidth. Moreover, EONs also allow the proposal of more flexible routing and spectrum assignment techniques, like the split-spectrum approach in which the request is divided into multiple "sub-lightpaths". In this thesis, four RSA algorithms are proposed combining two different levels of flexibility with the well-known k-shortest paths and first fit heuristics. After comparing the performance of those methods, a novel spectrum assignment technique, Best Gap, is proposed to overcome the inefficiencies emerged when combining the first fit heuristic with highly flexible networks. A simulation study is presented to demonstrate that, thanks to the use of Best Gap, EONs can exploit the network flexibility and reduce the blocking ratio. On the other hand, operators must face profound architectural changes to increase the adaptability and flexibility of networks and ease their management. Thanks to the use of network function virtualisation (NFV), the necessary network functions that must be applied to offer a service can be deployed as virtual appliances hosted by commodity servers, which can be located in data centres, network nodes or even end-user premises. The appearance of new computation and networking paradigms, like multi-access edge computing (MEC), may facilitate the adaptation of communication networks to the new demands. Furthermore, the use of MEC technology will enable the possibility of installing those virtual network functions (VNFs) not only at data centres (DCs) and central offices (COs), traditional hosts of VFNs, but also at the edge nodes of the network. Since data processing is performed closer to the enduser, the latency associated to each service connection request can be reduced. MEC nodes will be usually connected between them and with the DCs and COs by optical networks. In such a scenario, deploying a network service requires completing two phases: the VNF-placement, i.e., deciding the number and location of VNFs, and the VNF-chaining, i.e., connecting the VNFs that the traffic associated to a service must transverse in order to establish the connection. In the chaining process, not only the existence of VNFs with available processing capacity, but the availability of network resources must be taken into account to avoid the rejection of the connection request. Taking into consideration that the backhaul of this scenario will be usually based on WRONs or EONs, it is necessary to design the virtual topology (i.e., the set of lightpaths established in the networks) in order to transport the tra c from one node to another. The process of designing the virtual topology includes deciding the number of connections or lightpaths, allocating them a route and spectral resources, and finally grooming the traffic into the created lightpaths. Lastly, a failure in the equipment of a node in an NFV environment can cause the disruption of the SCs traversing the node. This can cause the loss of huge amounts of data and affect thousands of end-users. In consequence, it is key to provide the network with faultmanagement techniques able to guarantee the resilience of the established connections when a node fails. For the mentioned reasons, it is necessary to design orchestration algorithms which solve the VNF-placement, chaining and network resource allocation problems in 5G networks with optical backhaul. Moreover, some versions of those algorithms must also implements protection techniques to guarantee the resilience system in case of failure. This thesis makes contribution in that line. Firstly, a genetic algorithm is proposed to solve the VNF-placement and VNF-chaining problems in a 5G network with optical backhaul based on star topology: GASM (genetic algorithm for effective service mapping). Then, we propose a modification of that algorithm in order to be applied to dynamic scenarios in which the reconfiguration of the planning is allowed. Furthermore, we enhanced the modified algorithm to include a learning step, with the objective of improving the performance of the algorithm. In this thesis, we also propose an algorithm to solve not only the VNF-placement and VNF-chaining problems but also the design of the virtual topology, considering that a WRON is deployed as the backhaul network connecting MEC nodes and CO. Moreover, a version including individual VNF protection against node failure has been also proposed and the effect of using shared/dedicated and end-to-end SC/individual VNF protection schemes are also analysed. Finally, a new algorithm that solves the VNF-placement and chaining problems and the virtual topology design implementing a new chaining technique is also proposed. Its corresponding versions implementing individual VNF protection are also presented. Furthermore, since the method works with any type of WDM mesh topologies, a technoeconomic study is presented to compare the effect of using different network topologies in both the network performance and cost.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaDoctorado en Tecnologías de la Información y las Telecomunicacione

    Design and protection algorithms for path level aggregation of traffic in WDM metro optical networks

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    Wavelength Division Multiplexing (WDM) promises to offer a cost effective and scalable solution to meet the emerging demands of the Internet. WDM splits the tremendous bandwidth latent in a fiber into multiple non-overlapping wavelength channels, each of which can be operated at the peak electronic rate. Commercial systems with 128 wavelengths and transmission rates of up to 40 Gbps per wavelength have been made possible using state of the art optical technologies to deal with physical impairments. Systems with higher capacities are likely to evolve in the future. The end user requirements for bandwidth, on the other hand, have been ranging from 155 Mbps to 2.5 Gbps. Dedicating a wavelength for each end user will lead to severe underutilization of WDM channels. This brings to forefront the requirement for sharing of bandwidth in a wavelength among multiple end users.;The concept of wavelength sharing among multiple clients is called grooming. Grooming can be done purely at the optical layer (optical grooming) or it can be done with support from the client layer (electronic grooming). The advantage of all optical grooming is the ease of scalability due to its transparency as opposed to electronic grooming which is constrained by electronic bottlenecks. Efforts towards enhancing optical grooming is pursued through increasing optical switching speeds. However, technologies to make optical switches with high speeds, large port counts and low insertion losses have been elusive and may continue to remain so in the near future.;Recently, there have been some research into designing new architectures and protocols focused on optical grooming without resorting to fast optical switching. Typically, this is achieved in three steps: (1) configure the circuit in the form of a path or a tree; (2) use optical devices like couplers or splitters to allow multiple transmitters and/or receivers to share the same circuit; and (3) provide an arbitration mechanism to avoid contention among end users of the circuit. This transparent sharing of the wavelength channel utilizes the network resources better than the conventional low-speed circuit switched approaches. Consequently, it becomes important to quantify the improvement in achieved performance and evaluate if the reaped benefits justify the cost of the required additional hardware and software.;The contribution of this thesis is two fold: (1) developing a new architecture called light-trails as an IP based solution for next generation WDM optical networks, and (2) designing a unified framework to model Path Level Aggregation of Traffic in metrO Optical Networks (PLATOONs). The algorithms suggested here have three features: (1) accounts for four different path level aggregation strategies---namely, point to point (for example, lightpaths), point to multi-point (for example, source based light-trails), multi-point to point (for example, destination based light-trails) and multi-point to multi-point (for example, light-trails); (2) incorporates heterogenous switching architectures; and (3) accommodates multi-rate traffic. Algorithms for network design and survivability are developed for PLATOONs in the presence of both static and dynamic traffic. Connection level dedicated/shared, segregated/mixed protection schemes are formulated for single link failures in the presence of static and dynamic traffic. A simple medium access control protocol that avoids collisions when the channel is shared by multiple clients is also proposed.;Based on extensive simulations, we conclude that, for the studied scenarios, (1) when client layer has no electronic grooming capabilities, light-trails (employing multi-point to multi-point aggregation strategy) perform several orders of magnitude better than lightpaths and (2) when client layer has full electronic grooming capabilities, source based light-trails (employing point to multi-point aggregation strategy) perform the best in wavelength limited scenarios and lightpaths perform the best in transceiver limited scenarios.;The algorithms that are developed here will be helpful in designing optical networks that deploy path level aggregation strategies. The proposed ideas will impact the design of transparent, high-speed all-optical networks.</p

    Smart Algorithms for Hierarchical Clustering in Optical Network

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    Network design process is a very important in order to balance between the investment in the network and the supervises offered to the network user, taking into consideration, both minimizing the network investment cost, on the other hand, maximizing the quality of service offered to the customers as well.Partitioning the network to smaller sub-networks called clusters is required during the design process inorder to ease studying the whole network and achieve the design process as a trade-off between several atrtributes such as quality of service, reliability,cost, and management. Under CANON, a large scale optical network is partitioned into a number of geographically limited areas taking into account many different criteria like administrative domains, topological characteristics, traffic patterns, legacy infrastructure etc. An important consideration is that each of these clusters is comprised of a group of nodes in geographical proximity. The clusters can coincide with administrative domains but there could be many cases where two or more clusters belong to the same administrative domain. Therefore, in the most general case the partitioning into specific clusters can be either a off-line or a on-line process. In this work only the off-line case is considered. In this Study, we look at the problem of designing efficient 2- level Hierarchical Optical Networks (HON), in the context of network costs optimization. 2-level HON paradigm only have local rings to connect disjoint sets of nodes and a global sub mesh to interconnect all the local rings. We present an Hierarchical algorithm that is based on two phases. We present results for scenarios containing a set of real optical topologies

    Evaluating the energy consumption and the energy savings potential in ICT backbone networks

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