RT info:eu-repo/semantics/doctoralThesis
T1 Virtualisation and resource allocation in MECEnabled metro optical networks
A1 Ruiz Pérez, Lidia
A2 Universidad de Valladolid. Escuela Técnica Superior de Ingenieros de Telecomunicación
K1 Redes ópticas
K1 Tecnología MEC
K1 33 Ciencias Tecnológicas
AB The appearance of new network services and the ever-increasing network traffic and numberof connected devices will push the evolution of current communication networks towards theFuture Internet.In the area of optical networks, wavelength routed optical networks (WRONs) are evolvingto 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 inthese networks is the lightpath, i.e., all-optical circuits between two network nodes. Theestablishment of lightpaths requires the selection of the route that they will follow and theportion of the spectrum to be used in order to carry the requested traffic from the source tothe 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 sliceof spectrum of variable size is assigned to a request. However, the most common approach tothe 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 offlexibility with the well-known k-shortest paths and first fit heuristics. After comparing theperformance of those methods, a novel spectrum assignment technique, Best Gap, is proposedto overcome the inefficiencies emerged when combining the first fit heuristic with highlyflexible networks. A simulation study is presented to demonstrate that, thanks to the use ofBest Gap, EONs can exploit the network flexibility and reduce the blocking ratio.On the other hand, operators must face profound architectural changes to increase theadaptability and flexibility of networks and ease their management. Thanks to the use ofnetwork function virtualisation (NFV), the necessary network functions that must be appliedto offer a service can be deployed as virtual appliances hosted by commodity servers, whichcan be located in data centres, network nodes or even end-user premises. The appearance ofnew computation and networking paradigms, like multi-access edge computing (MEC), mayfacilitate the adaptation of communication networks to the new demands. Furthermore, theuse 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, butalso 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 nodeswill 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: theVNF-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 toestablish the connection. In the chaining process, not only the existence of VNFs with availableprocessing capacity, but the availability of network resources must be taken into account toavoid the rejection of the connection request. Taking into consideration that the backhaul ofthis scenario will be usually based on WRONs or EONs, it is necessary to design the virtualtopology (i.e., the set of lightpaths established in the networks) in order to transport the tra cfrom one node to another. The process of designing the virtual topology includes deciding thenumber of connections or lightpaths, allocating them a route and spectral resources, and finallygrooming the traffic into the created lightpaths.Lastly, a failure in the equipment of a node in an NFV environment can cause thedisruption of the SCs traversing the node. This can cause the loss of huge amounts of dataand affect thousands of end-users. In consequence, it is key to provide the network with faultmanagementtechniques able to guarantee the resilience of the established connections when anode fails.For the mentioned reasons, it is necessary to design orchestration algorithms which solvethe VNF-placement, chaining and network resource allocation problems in 5G networkswith optical backhaul. Moreover, some versions of those algorithms must also implementsprotection techniques to guarantee the resilience system in case of failure.This thesis makes contribution in that line. Firstly, a genetic algorithm is proposed to solvethe VNF-placement and VNF-chaining problems in a 5G network with optical backhaul basedon star topology: GASM (genetic algorithm for effective service mapping). Then, we proposea modification of that algorithm in order to be applied to dynamic scenarios in which thereconfiguration of the planning is allowed. Furthermore, we enhanced the modified algorithmto 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 andVNF-chaining problems but also the design of the virtual topology, considering that a WRONis deployed as the backhaul network connecting MEC nodes and CO. Moreover, a versionincluding individual VNF protection against node failure has been also proposed and theeffect of using shared/dedicated and end-to-end SC/individual VNF protection schemes arealso analysed.Finally, a new algorithm that solves the VNF-placement and chaining problems andthe 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 technoeconomicstudy is presented to compare the effect of using different network topologies inboth the network performance and cost.
YR 2020
FD 2020
LK http://uvadoc.uva.es/handle/10324/43645
UL http://uvadoc.uva.es/handle/10324/43645
LA eng
NO Departamento de Teoría de la Señal y Comunicaciones e Ingeniería Telemática
DS UVaDOC
RD 22-dic-2024