IMDEA Networks Institute Digital Repository
Not a member yet
1915 research outputs found
Sort by
Power Management and TCP Congestion Control: Friends or Foes?
Get PDFhttp://www.itcspecialistseminar22.com
co-located with Australasian Telecommunication Networks and Applications Conference (ATNAC) (http://www.atnac.org/)Optimizing the trade off between power saving and Quality of Service(QoS)in the current Internet is a challenging research objective, whose difficulty stems also from the dominant presence of TCP traffic, and its elastic nature. In a previous work we have shown that an intertwining exists between capacity scaling approaches and TCP congestion control. In this paper we investigate the reasons of such intertwining, and we evaluate how and how much the dynamics of the two algorithms affect each other's performance. More specifically, we will show that such an interaction is essentially due to the overlap of the two closed loop controls, with different time constants.TRUEpu
QoS-aware greening of interference-limited cellular networks
Get PDFPrint ISBN: 978-1-4673-5827-9
INSPEC Accession Number: 13712822
Digital Object Identifier: 10.1109/WoWMoM.2013.6583396We consider the problem of minimizing the energy consumed in a cellular access network, under loads that slowly vary over space and time, while guaranteeing quality of service (QoS). In particular, we formalize the problem of jointly optimizing the base stations (BS) power levels and the association of users to BSs, while guaranteeing a minimum throughput to each user, and a target value of blocking probability. We propose abstractions that enable tracking of long-term spatial load distributions, and a practical algorithm for energy efficient user association and base station power allocation. Our algorithm is applicable to arbitrary (planar) BS layouts, to settings with interference, to different BS energy models, and to arbitrary user distributions over the service area. Through extensive simulations using measured data, and realistic BS deployments, we show that our algorithm leads to substantial energy savings both with traditional BS designs and with energy-proportional equipment, and we demonstrate the potential of BS sleep modes to achieve network-level energy proportionality.TRUEpu
Virtual Induction Loops Based on Cooperative Vehicular Communications
Get PDFInduction loop detectors have become the most utilized sensors in traffic management systems. The gathered traffic data is used to improve traffic efficiency (i.e., warning users about congested areas or planning new infrastructures). Despite their usefulness, their deployment and maintenance costs are expensive. Vehicular networks are an emerging technology that can support novel strategies for ubiquitous and more cost-effective traffic data gathering. In this article, we propose and evaluate VIL (Virtual Induction Loop), a simple and lightweight traffic monitoring system based on cooperative vehicular communications. The proposed solution has been experimentally evaluated through simulation using real vehicular traces.pu
Segment Routing Use Cases
Get PDFNetwork Working Group
Internet-Draft
Intended status: Standards Track
Expires: April 24, 2014Segment Routing (SR) leverages the source routing and tunneling paradigms. A node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. A segment can represent any instruction, topological or service-based. SR allows to enforce a flow through any topological path and service chain while maintaining per-flow state only at the ingress node of the SR domain.
The Segment Routing architecture can be directly applied to the MPLS dataplane with no change on the forwarding plane. It requires minor extension to the existing link-state routing protocols. Segment Routing can also be applied to IPv6 with a new type of routing extension header.pu
Design and Implementation of a Learning Analytics Module for the Khan Academy Platform
No full textThe learning process is changing due to the possibilities offered by the new technologies in education. One of these possibilities is the exhaustive collection of data. Currently, most e-learning platforms are able to collect large data set of students’ interactions as events. However, these low level data are difficult to be interpreted directly by learning stakeholders. A major challenge is how to transform these low level data into intelligent information, and show them to teachers and students in an understandable way. Learning analytics, which is the science that deals with this problem, has emerged strongly in recent years. Khan Academy is one of the pioneering platforms to show relevant information about the learning process. However, Khan Academy’s learning analytics module can be greatly improved to include new intelligent information that is useful to enhance the learning process. In this work, we have designed and implemented a learning analytics module for the Khan Academy platform, which extends the Khan Academy learning analytics support by default. In this way, we propose a set of interesting parameters in order to learn more about the learning process, and we establish a way to process them from the low level data. Furthermore, these parameters have been implemented, as well as individual and class visualizations based on these parameters. We have used technologies like the Python programming language, Google App Engine infrastructure, Datastore based on Big Data, or Google Charts. Finally, we show how this module and the defined parameters can be used to evaluate the learning process. We apply this evaluation to undergraduate remedial courses at Universidad Carlos III de Madrid, where the Khan Academy platform and the module developed in this master thesis have been used.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
NetIDE: First steps towards an integrated development environment for portable network apps
Get PDFNowadays, while most of the programmable network apparatus vendors support OpenFlow, a number of fragmented control plane solutions exist for proprietary Software–Defined Networks. Thus, network applications developers are forced to re-implement their solutions every time they encounter
a new network controller. Moreover, different network developers adopt different solutions as control plane programming language (e.g. Frenetic, Procera), severely limiting code sharing and reuse. Despite having OpenFlow as candidate standard interface between the controller and the network infrastructure, interoperability between different controllers and network devices is hindered and closed ecosystems are emerging. In this paper we present the roadmap toward NetIDE, an integrated development environment which aims at supporting the whole development
lifecycle of vendor–agnostic network applications.TRUEpu
Unbounded Contention Resolution in Multiple-Access Channels
Get PDFA frequent problem in settings where a unique resource must be shared among users is how to resolve the contention that arises when all of them must use it, but the resource allows only for one user each time. The application of efficient solutions for this problem spans a myriad of settings such as radio communication networks or databases. For the case where the number of users is unknown, recent work has yielded fruitful results for local area networks and radio networks, although either a (possibly loose) upper bound on the number of users needs to be known (Fernández Anta and Mosteiro in Discrete Math., Algorithms Appl. 2(4):445–456, 2010), or the solution is suboptimal (Bender et al. in ACM 17th Annual Symposium on Parallel Al- gorithms and Architectures, pp. 325–332, 2005), or it is only implicit (Greenberg and Leiserson in Adv. Comput. Res. 5:345–374, 1989) or embedded (Farach-Colton et al. in Theor. Comput. Sci. 472:60–80, 2013) in other problems, with bounds proved only asymptotically. In this paper, under the assumption that collision detection or information on the number of contenders is not available, we present a novel protocol for contention resolution in radio networks, and we recreate a protocol previously used for other problems (Greenberg and Leiserson in Adv. Comput. Res. 5:345–374, 1989, Farach-Colton et al. in Theor. Comput. Sci. 472:60–80, 2013), tailoring the constants for our needs. In contrast with previous work, both protocols are proved to be opti- mal up to a small constant factor and with high probability for big enough number of contenders. Additionally, the protocols are evaluated and contrasted with the previ- ous work by extensive simulations. The evaluation shows that the complexity bounds obtained by the analysis are rather tight, and that both protocols proposed have small and predictable complexity for many system sizes (unlike previous protocols).pu
Connectivity Properties of Real BitTorrent Swarms
Get PDFBitTorrent is one of the most important applications in the current Internet. Despite of its interest, we still have little knowledge regarding the connectivity properties of real BitTorrent swarms. In this paper we leverage a dataset including the connectivity information of 250 real torrents and more than 150k peers to carefully study the connectivity properties of peers. The main topology parameters of the studied swarms suggest that they are significantly less resilient than random graphs. The analysis of the peer level connectivity properties reveals that peers continuously change more than half of their neighbours. Furthermore, we also find that a leecher typically keeps stable connections with a handful of neighbours with which it exchanges most of its traffic whereas seeders do not establish long-term connections with any peer so that they can homogeneously distribute chunks among leechers. Finally, we have discovered that a significant portion of the studied peers (45%) have an important locality-biased neighbourhood composition.pu
Graceful Router Updates in Link-State Protocols
Get PDFManageability and evolvability are crucial needs for IP networks. Unfortunately, planned topological changes may lead to transient forwarding loops in link-state routing protocols commonly used in IP networks. These lead to service unavailability, reducing the frequency at which operators can adapt the network topology.
Prior works proved that the state of a given link can be modified while avoiding forwarding inconsistencies without changing protocol specifications. In this paper, we study the more general problem of gracefully modifying the state of an entire router, while minimizing the induced operational impact. As opposed to a single-link modification, the router update problem is k-dimensional for a node of degree k. Moreover, we show that the interplay between operations applied at the router granularity can lead to loops that do not occur considering a single-link modification. In this paper, we present an efficient algorithm that computes minimal sequences of weights to be configured on the links of the updated node. Based on real IP network topologies, we show that the size of such sequence is limited in practice.TRUEpu