Revisiting core traffic growth in the presence of expanding CDNs

Traffic growth forecasts announce a dramatic future for core networks, struggling to keep the pace of traffic augmentation. Internet traffic growth primarily stems from the proliferation of cloud services and the massive amounts of data distributed by the content delivery networks (CDNs) hosting these services. In this paper, we investigate the evolution of core traffic in the presence of growing CDNs. Expanding the capacities of existing data centers (DCs) directly translates the forecasted compound-annual-growth-rate (CAGR) of user traffic to the CAGR of carried core link traffic. On the other hand, expanding CDNs by building new geographically dispersed DCs can significantly reduce the predicted core traffic growth rates by placing content closer to the users. However, reducing DC-to-user traffic by building new DCs comes at a trade-off with increasing inter-DC content synchronization traffic. Thus, the resulting overall core traffic growth will depend on the types of services supported and their associated synchronization requirements. In this paper, we present a long-term evolution study to assess the implications of different CDN expansion strategies on core network traffic growth considering a mix of services in proportions and growth rates corresponding to well-known traffic forecasts. Our simulations indicate that CDNs may have significant incentive to build more DCs, depending on the service types they offer, and that current alarming traffic predictions may be somewhat overestimated in core networks in the presence of expanding CDNs. (C) 2019 The Authors. Published by Elsevier B.V.The research leading to these results has received funding from the European Commission for the H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727) and it has been partially funded by the Spanish national project ONOFRE-2(TEC2017-84423-C3-1-P, MINECO/AEI/FEDER, UE)

Scheduled virtual topology design under periodic traffic in transparent optical networks

This paper investigates offline planning and scheduling in transparent optical networks for a given periodic traffic demand. The main objective is to minimize the number of transceivers needed which make up for the main network cost. We call this problem ldquoScheduled Virtual Topology Designrdquo and consider two variants: non-reconfigurable and reconfigurable equipment. We formulate both problems as exact MILPs (Mixed Integer Linear Programs). Due to their high complexity, we propose a more scalable tabu search heuristic approach, in conjunction with smaller MILP formulations for the associated subproblems. The main motivation of our research efforts is to assess the benefits of using reconfigurable equipment, realized as a reduction in the number of required transceivers. Our results show that the achieved reductions are not very significant, except for cases with large network loads and high traffic variability.The work described in this paper was carried out with the support of the BONE-project ("Building the Future Optical Network in Europe”), a Network of Excellence funded by the European Commission through the 7th ICTFramework Programme, support of the MEC Spanish project TEC2007- 67966-01/TCM CONPARTE-1 and developed in the framework of "Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, de la Fundación Séneca (Plan Regional de Ciencia y Tecnología 2007/2010).

Virtual topology design and flow routing in optical networks under multi-hour traffic demand

This paper addresses the problem of finding a static virtual topology design and flow routing in transparent optical WDM networks under a time-varying (multi-hour) traffic demand. Four variants of the problem are considered, using fixed or dynamically adaptable (i.e., variable) flow routing, which can be splittable or unsplittable. Our main objective is to minimize the number of transceivers needed which make up for the main network cost. We formulate the problem variants as exact ILPs (Integer Linear Programs) and MILPs (Mixed ILPs). For larger problem instances, we also propose a family of heuristics based on the concept of domination between traffic matrices. This concept provides the theoretical foundations for a set of techniques proposed to reduce the problem complexity. We present a lower bound to the network cost for the case in which the virtual topology could be dynamically reconfigured along time. This allows us to assess the limit on the maximum possible benefit that could be achieved by using optical reconfigurable equipment. Extensive tests have been conducted, using both synthetically generated and real-traced traffic demands. In the cases studied, results show that combining variable routing with splittable flows obtains a significant, although moderate, cost reduction. The maximum cost reduction achievable with reconfigurable virtual topologies was shown to be negligible compared to the static case in medium and high loads.The work described in this paper was carried out with the support of the BONE project (“Building the Future Optical Network in Europe”); a Network of Excellence funded by the European Commission through the 7th ICT-Framework Program. This research has been partially supported by the projects from the Spanish Ministry Of Education TEC2007-67966-01/TCM CON-PARTE-1, and TEC2008-02552-E, and it is also developed in the framework of the projects from Fundación Seneca (Regional Agency of Science and Technology of Region of Murcia ) 00002/CS/08 (FORMA) and "Programa de Ayudas a Grupos de Excelencia de la Región. de Murcia”, F. Séneca (Plan Regional de Ciencia y Tecnología 2007/2010)."

Algorithms for virtual topology reconfiguration under multi-hour traffic using Lagrangian relaxation and Tabu Search approaches

Periodic reconfiguration of the virtual topology in transparent optical networks has been recently investigated as a mechanism to more efficiently adapt the network to predictable periodic traffic variations along the day or week. The scheduling of periodic reconfigurations should consider the trade-off between a lower network cost obtained through better resource allocation, and the undesired traffic disruptions that these reconfigurations may cause. This paper presents and compares two algorithms for planning virtual topology reconfiguration suitable for exploring this trade-off. The first is based on a Lagrangian relaxation of the planning problem, and the second is based on a Tabu Search meta-heuristic. The merits of both algorithms are compared

Heuristički algoritmi za planiranje virtualnih topologija, usmjeravanje i dodjeljivanje valnih duljina u WDM mrežama

This thesis investigates the problem of designing virtual topologies in wavelength routed WDM (Wavelength Division Multiplex) optical networks. In such networks, a virtual topology is created over the physical optical network by establishing all-optical connections, called lightpaths, between pairs of nodes. Transport via a lightpath is entirely in the optical domain. A virtual topology can also be composed of a set of light-trees which optically connect a subset of nodes in the network. In order to establish a virtual topology, it is necessary to determine a set of lightpaths/light-trees, find for them corresponding paths in the physical topology and assign wavelengths to them. Finally, packet-switched traffic is routed over the virtual topology. The thesis focuses on the problem of routing and assigning wavelengths to lightpaths and light-trees, and the virtual topology design problem in WDM networks. These problems are NP-complete so heuristic algorithms are needed to help solve them. Proposed are efficient heuristic algorithms for the Routing and Wavelength Assignment (RWA) of static and scheduled lightpath demands. Furthermore, developed is a heuristic for multicast routing and algorithms for static multicast RWA. Virtual Topology Design is investigated considering various objective criteria, and an additional objective criterion is proposed. Efficient heuristic algorithms are developed to help solve this problem. To assess the quality of the solutions obtained by the proposed algorithms, new analytical lower bounds for the corresponding problems are developed.Doktorska disertacija istražuje problem planiranja virtualnih topologija u optčkim WDM (Wavelength Division Multiplex) mrežama temeljenim na valnom usmjeravanju. U takvim mrežama, gradi se virtualna topologija nad fizičkom optičkom mrežom uspostavom sve-optičkih kanala, ili svjetlosnih putova, između parova čvorova. Transport po svjetlosnim putovima odvija se isključivo u optičkoj domeni. Virtualna topologija se također može sastojati od skupa svjetlosnih stabala koji sve-optički povezuju skup čvorova. Kako bi se uspostavila virtualna topologija, potrebno je odrediti skup zahtjeva za svjetlosnim putovima/stablima, naći njima odgovarajuće putove u fizičkoj topologiji te im dodijeliti valne duljine. Paketski promet se potom usmjerava kroz uspostavljenu virtualnu topologiju. Istraživanja su fokusirana na problem usmjeravanja i dodjeljivanja valnih duljina svjetlosnim putovima i stablima, te općeniti problem planiranja virtualnih topologija u WDM mrežama. Ovi problemi su NP-potpuni optimizacijski problemi, te su potrebni heuristički algoritmima za njihovo rješavanje. Predloženi su efikasni heuristički algoritmi za probleme usmjeravanja i dodjeljivanja valnih duljina statičkim te raspoređenim zahtjevima za svjetlosnim putovima. Nadalje, razvijen je efikasan heuristički algoritam za višeodredišno usmjeravanje, te heuristike za problem statičkog višeodredišnog usmjeravanja i dodjeljivanja valnih duljina. Istraženo je planiranje virtualnih topologija uzimajući u obzir više ciljeva, te je predložen dodatan kriterij pri planiranju virtualnih topologija. Razvijeni su efikasni heuristicki algoritmi za rješavanje ovog problema. Kako bismo utvrdili kvalitetu rješenja dobivenih predloženim algoritmima, razvijene su nove analitičke donje granice za navedene probleme