IMDEA Networks Institute Digital Repository
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The Playground of Wireless Dense Networks of the Future
Get PDFThis poster presents the key ideas behind the ICT CROWD (Connectivity management for eneRgy Optimised Wireless Dense networks) project, funded by the European Commission. The project moves from the observation that wireless traffic demand is currently growing exponentially. This growing demand can only be satisfied by increasing the density of points of access and combining different wire- less technologies. Mobile network operators have already started to push for denser, heterogeneous deployments; however, current technology needs to steer towards effi- ciency, to avoid unsustainable energy consumption and network performance implo- sion due to interference. In this context, CROWD pursues four key goals: (i) bringing density-proportional capacity where it is needed, (ii) optimising MAC mechanisms operating in very dense deployments by explicitly accounting for density as a resource rather than as an impediment, (iii) enabling traffic-proportional energy consumption, and (iv) guaranteeing mobile user’s quality of experience by designing smarter con- nectivity management solutions.TRUEpu
Improving Network Agility With Seamless BGP Reconfigurations
Get PDFThe network infrastructure of Internet Service Providers (ISPs) undergoes constant evolution. Whenever new requirements arise (e.g., the deployment of a new Point of
Presence, or a change in the business relationship with a
neighboring ISP), operators need to change the configuration
of the network. Due to the complexity of BGP and to the lack of methodologies and tools, maintaining service availability during reconfigurations that involve BGP is a challenge for operators. In this paper, we show that the current best practices to reconfigure BGP do not provide guarantees with respect to traffic disruptions. Then, we study the problem of finding an operational ordering of BGP reconfiguration steps which guarantees no packet loss. Unfortunately, finding such an operational ordering, when it exists, is computationally hard. To enable lossless reconfigurations, we propose a framework that extends current
features of carrier-grade routers to run two BGP control planes in parallel. We present a prototype implementation and we show the effectiveness of our framework through a case study.TRUEpu
Power-efficient Assignment of Virtual Machines to Physical Machines
Get PDFMotivated by current trends in cloud computing, we study a version of the generalized assignment problem where a set of virtual processors has to be implemented by a set of identical processors. For literature consistency we say that a set of virtual machines (VMs) is assigned to a set of physical machines (PMs). The optimization criteria is to minimize the power consumed by all the PMs. We term the problem Virtual Machine Assignment (VMA). Crucial differences with previous work include a variable number of PMs, that the VMs cannot be implemented fractionally (i.e., each VM must be assigned to exactly one PM), and a parametric minimum power consumption for each active PM. We show that the VMA problem is NP-hard in the strong sense and we present a VMA offline approximation algorithm. For this VMA protocol, we show the trade-off between the running time and the approximation ratio achieved. Furthermore, restricting the VMA problem to realistic applications, we observe that such protocol is a PTAS5 for the VMA problem, while there is no FPTAS6. Moving to online VMA algorithms, we show upper and lower bounds on the competitive ratio when only 2 PMs are available, lower bounds when some arbitrary number m of PMs are available, and an upper bound when the number of machines is unbounded. We also carry extensive simulations using real-world input such as Google cluster data. To the best of our knowledge, this is the first time the VMA problem is studied for this cost function.TRUEpu
Streaming 3D Meshes over Thin Mobile Devices
No full textWe are witnessing a significant growth in applications using thin mobile devices, such as social networks, virtual walkthrough, massively multiplayer online gaming (MMOG), and augmented reality (AR), just to mention a few. Virtual environments (VE) based class of applications have recently attracted a large number of users. Applications that applied the conventional client-server architecture require the VE to be stored on the client, which is not very feasible due to the client's memory constraints. To address this issue, 3D streaming techniques have been designed and are widely used nowadays. However, several challenges exist and affect the user's Quality of Experience (QoE). By all means, these challenges need to be resolved before the 3D streaming technology over thin mobile devices becomes a commodity. In this paper, we provide a survey on the existing 3D streaming techniques by classifying them based on the nature of the application, and we centralize our attention on methods applied to adapt 3D streaming techniques to the changes in the wireless network conditions. Therefore, we discuss the challenges that the 3D streaming techniques face from a network point of view, as well as the approaches and solutions proposed.TRUEpu
Crowd computing as a cooperation problem: an evolutionary approach
Get PDFCooperation is one of the socio-economic issues that has received more attention from the physics community. The problem has been mostly considered by studying games such as the Prisoner’s Dilemma or the Public Goods Game. Here, we take a step forward by studying cooperation in the context of crowd computing. We introduce a model loosely based on Principal-agent theory in which people (workers) contribute to the solution of a distributed problem by computing answers and reporting to the problem proposer (master). To go beyond classical approaches involving the concept of Nash equilibrium, we work on an evolutionary framework in which both the master and the workers update their behavior through reinforcement learning. Using a Markov chain approach, we show theoretically that under certain – not very restrictive – conditions, the master can ensure the reliability of the answer resulting of the process. Then, we study the model by numerical simulations, finding that convergence, meaning that the system reaches a point in which it always produces reliable answers, may in general be much faster than the upper bounds given by the theoretical calculation. We also discuss the effects of the master’s level of tolerance to defectors, about which the theory does not provide information. The discussion shows that the system works even with very large tolerances. We conclude with a discussion of our results and possible directions to carry this research further.TRUEpu
CROWD: An SDN Approach for DenseNets
Get PDFTraffic demands in mobile networks are expected to grow substantially in the next years, both in terms of total traffic volume and of bit-rate required by individual users. It is generally agreed that the only possible solution to overcome the current limitations is to deploy very dense and heterogeneous wireless networks, which we call DenseNets. However, simply scaling down existing networks by orders of magnitude, as required to fulfill traffic forecasts, is not possible because of the following constraints: i) the bottleneck would shift from the Radio Access Network (RAN) to the backhaul; ii) control overhead, especially related to mobility management, would make the network col- lapse; iii) operational costs of the network would be unbearable due to energy consumption and maintenance/optimisation. In this paper, Software Defined Network (SDN) for mobile networks is claimed as the paradigm shift necessary to tackle adequately the above challenges. A novel architecture is proposed, which supports DenseNets made of overlapping LTE and WLAN cells connected to the core network via a reconfigurable backhaul.TRUEpu
