IMDEA Networks Institute Digital Repository
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Alta Scuola Politecnica: Innovation, Multi-disciplinarity and Passion
No full textAlta Scuola Politecnica (www.asp-poli.it, (ASP 2009)) was founded in 2004 by the Politecnico di Milano and Politecnico di Torino. It annually selects 150 talented students solely on the basis of merit, from among the applicants to the Master of Science in Engineering, Architecture and Design at the two universities. The resulting community is made up of very motivated and qualified students with a passion for innovation. These students follow an additional track, completely in English, based on ad hoc courses and the development of multidisciplinary projects; the ASP program administrates 30 credits (CFU) to be achieved in parallel to the regular 120 credits of the Master program, 15 from courses and 15 from projects; thus, it consists of an addition to the Master program of about one-fourth of its total workload. The mission of ASP is to provide society with high-profile graduates combining in-depth disciplinary knowledge with interdisciplinary, horizontal skills that are needed to work in a truly multidisciplinary environment.TRUEpu
The Adblocking Tug-of-War
Get PDFOnline advertising subsidizes a majority of the “free” services on the Web. Yet many find this approach intrusive and annoying, resorting to adblockers to get rid of ads chasing them all over the Web. A majority of those using an adblocker tool are familiar with messages asking them to either disable their adblocker or to consider supporting the host Web site via a donation or subscription. This is a recent development in the ongoing adblocking arms race which we have explored in our recent report, “Adblocking and Counter Blocking: A Slice of the Arms Race” [1]. For our study, we used popular adblockers, trawled the Web and analyzed some of the most popular sites to uncover how many are using anti-adblockers. Our preliminary analysis found that anti-adblockers come from a small number of providers, are widely used, and that adblockers also often block anti-adblockers.pu
Challenges and solutions for networking in the millimeter-wave band
No full textOne of the most promising options to significantly increase data rates in future wireless networks is to vastly increase the communication bandwidth. Such very high bandwidth channels are only available in the extremely high frequency part of the radio spectrum, the millimeter wave band (mm-wave). Upcoming communication technologies, for example IEEE 802.11ad, are already starting to exploit this part of the radio spectrum to achieve data rates of several GBit/s. mm-wave communication is also discussed as key technology for 5G mobile networks. However, communication at such high frequencies also suffers from high attenuation and signal absorption, often restricting communication to line-of-sight scenarios and requiring the use of highly directional antennas. This in turn requires a radical rethinking of wireless network design. On the one hand side, such channels experience little interference, allowing for a high degree of spatial reuse and potentially simpler MAC and interference management mechanisms. On the other hand, such an environment is extremely dynamic and channels may appear and disappear over very short time intervals, in particular for mobile devices. It is essential to take these characteristics into account to design efficient wireless architectures. The talk will highlight main challenges and possible solutions for networking in the mm-wave band.TRUEpu
Privacy in the Cloud: Anonymous Tax Preparation
No full textDOI: 10.1109/BigDataSecurity-HPSC-IDS.2016.33We present a distributed tax preparation application as an example of anonymous processing in the cloud where processing units are interconnected anonymously via intermediaries. This example uses the double-locked box which was used in the anonymous credit card in the 1990s. However, unlike the anonymous credit card our application automates the distribution of the double-locked boxes and the connection of involved participants with minimal user interaction. We also introduce an entropy-based metric. As processing units are compromised, loss of anonymity is measured using this entropy metric.TRUEpu
On Demand Elastic Capacity Planning for Service Auto-Scaling
Get PDFCloud computing allows on demand elastic service
scaling. The capability of a service to predict resource requirements for the next operational period defines how well it will exploit the elasticity of cloud computing in order to reduce operational costs. In this work, we consider a capacity planning process for service scale-out as an online pricing model. In particular, we study the impact of buffering service requests on revenues in various settings with allocation and maintenance
costs. In addition, we analyze the incurred latency implied by buffering service requests. We believe that our insights will allow to significantly simplify predictions and mitigate the unknowns of future demands on resources.TRUEpu
Heterogeneous Packet Processing in Shared Memory Buffers
Get PDFPacket processing increasingly involves heterogeneous requirements. We consider the well-known model of a shared memory switch with bounded-size buffer and generalize it in two directions. First, we consider unit-sized packets labeled with an output port and a processing requirement (i.e., packets with heterogeneous processing), maximizing the number of transmitted packets. We analyze the performance of buffer management policies under various characteristics via competitive analysis that provides uniform guarantees across traffic patterns [10]. We propose the Longest-Work-Drop policy and show that it is at most
2-competitive and at least p2-competitive. Second, we consider another generalization, posed as an open problem in [19], where each unit-sized packet is labeled with an output port and intrinsic value, and the goal is to maximize the total value of transmitted packets. We show first results in this direction and define a scheduling policy that, as we conjecture, may achieve constant competitive ratio. We also present a comprehensive simulation study that validates our results.pu
Brief Announcement: Oh-RAM! One and a Half Round Read/Write Atomic Memory
Get PDFEmulating atomic read/write shared objects in a message-passing system is a fundamental problem in distributed computing. Considering that network communication is the most expensive resource, efficiency is measured first of all in terms of the communication needed to implement read and write operations. It is well known that two communication round-trip phases involving in total four message exchanges are sufficient to implemented atomic operations. In this work we present a comprehensive treatment of the question of when and how it is possible to implement atomic memory where read and write operations complete in three message exchanges, i.e., we aim for One and half Round Atomic Memory, hence the name Oh-RAM! We present algorithms that allow operations to complete in three communication exchanges without imposing any constraints on the number of readers and writers. We present an implementation for the single-writer/multiple-reader (SWMR) setting, where reads complete in three communication exchanges and writes complete in two exchanges. Then we pose the question of whether it is possible to implement multiple-writer/multiple-reader (MWMR) memory where operations complete in at most three communication exchanges. We answer this question in the negative by showing that an atomic memory implementation is impossible if both read and write operations take three communication exchanges, even when assuming two writers, two readers, and a single replica server failure. Motivated by this impossibility result, we provide a MWMR atomic memory implementation where reads involve three and writes involve four communication exchanges. In light of our impossibility result these algorithms are optimal in terms of the number of communication exchanges.TRUEpu
Packet Mass Transit: Improving Frame Aggregation in 60 GHz Networks
Get PDFThe impact of frame aggregation on wireless network performance increases dramatically with higher data rates. The key problem is that the transmission time of packets decreases while the medium access, preamble and packet header overhead remain the same. Recent 802.11 standards address this issue using frame aggregation, i.e., grouping multiple data frames in a single transmission to reduce the overhead. This already provides substantial efficiency gains in networks operating in the 2.4 GHz and 5 GHz bands, and for future 60 GHz networks such as 802.11ad, gains are even more pronounced due to the order of magnitude higher data rates. In 802.11ad, frame aggregation becomes crucial to achieve the multi-gbps data rates that are possible in theory, since medium access overhead can be 20x larger than the time required to transmit a single packet. While frame aggregation is essential, it very much depends on the traffic patterns present in the wireless network, and a node may not always have enough packets in the transmit queue to achieve a sufficiently large aggregated frame size. In this paper, we investigate in which case nodes should wait to construct a larger aggregated packet before starting the channel access procedure. We present a simple waiting policy for the uplink case that either waits for a minimum number of packets or for a maximum amount of time, whichever comes first. For the downlink case, we utilize a maximum weight scheduling policy with a maximum waiting time. Our results show that both policies significantly improve medium utilization, thus increasing throughput and reducing end-to-end delay.TRUEpu
Implementation and Evaluation of a WLAN IEEE 802.11ad Model in ns-3
Get PDFThe IEEE 802.11ad amendment to the 802.11 standard for
multi-gigabit communication at 60 GHz was published sev-
eral years ago, but to date, no precise simulation model
for networking in this band is available. In this paper, we present a model for IEEE 802.11ad implementated in the
network simulator ns-3. We model new techniques that are
essential for IEEE 802.11ad operation such as beamform-
ing training and steering, relay support, and fast session transfer. We then evaluate by simulation the performance of IEEE 802.11ad as well as the gains obtained through the aforementioned techniques. The code for our simulation model is publicly available.TRUEpu
Analyzing the Impact of Using Optional Activities in Self-Regulated Learning
Get PDFSelf-regulated learning (SRL) environments provide students with activities to improve their learning (e.g., by solving exercises), but they might also provide optional activities (e.g., changing an avatar image or setting goals) where students can decide whether they would like to use or do them and how. Few works have dealt with the use of optional activities in SRL environments. This paper thus analyzes the use of optional activities in two case studies with a SRL approach. We found that the level of use of optional activites was low with only 23.1 percent of students making use of some functionality, while the level of use of learning activities was higher. Optional activities which are not related to learning are used more. We also explored the behavior of students using some of the optional activities in the courses such as setting goals and voting comments, finding that students finished the goals they set in more than 50 percent of the time and that they voted their peers’ comments in a positive way. We also found that gender and the type of course can influence which optional activities are used. Moreover, the relations of the use of optional activities with proficient exercises and learning gains is low when taking out third variables, but we believe that optional activities might motivate students and produce better learning in an indirect way.pu