References of "Kaafar, Mohamed Ali"
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See detailOn the Potential of Recommendation Technologies for Efficient Content Delivery Networks
Kaafar, Mohamed Ali; Berkovsky, Shlomo; Donnet, Benoît ULg

in Computer Communication Review (2013), 43(3), 74-77

During the last decade, we have witnessed a substantial change in content delivery networks (CDNs) and user access paradigms. If previously, users consumed content from a central server through their ... [more ▼]

During the last decade, we have witnessed a substantial change in content delivery networks (CDNs) and user access paradigms. If previously, users consumed content from a central server through their personal computers, nowadays they can reach a wide variety of repositories from virtually everywhere using mobile devices. This results in a considerable time-, location-, and event-based volatility of content popularity. In such a context, it is imperative for CDNs to put in place adaptive content management strategies, thus, improving the quality of services provided to users and decreasing the costs. In this paper, we introduce predictive content distribution strategies inspired by methods developed in the Recommender Systems area. Specifically, we outline different content placement strategies based on the observed user consumption patterns, and advocate their applicability in the state of the art CDNs. [less ▲]

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See detailPath Similarity Evaluation using Bloom Filters
Donnet, Benoît ULg; Gueye, Bamba,; Kaafar, Mohamed Ali

in Computer Networks (2012), 56(2), 858-869

The performance of several Internet applications often relies on the measurability of path similarity between different participants. In particular, the performance of content distribution networks mainly ... [more ▼]

The performance of several Internet applications often relies on the measurability of path similarity between different participants. In particular, the performance of content distribution networks mainly relies on the awareness of content sources topology information. It is commonly admitted nowadays that, in order to ensure either path redundancy or efficient content replication, topological similarities between sources is evaluated by exchanging raw traceroute data, and by a hop by hop comparison of the IP topology observed from the sources to the several hundred or thousands of destinations. In this paper, based on real data we collected, we advocate that path similarity comparisons between different Internet entities can be much simplified using lossy coding techniques, such as Bloom filters, to exchange compressed topology information. The technique we introduce to evaluate path similarity enforces both scalability and data confidentiality while maintaining a high level of accuracy. In addition, we demonstrate that our technique is scalable as it requires a small amount of active probing and is not targets dependent. [less ▲]

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See detailIP Geolocation Databases: Unreliable?
Poese, Ingmar; Uhlig, Steve; Kaafar, Mohamed Ali et al

in Computer Communication Review (2011), 41(2), 53-56

The most widely used technique for IP geolocation con- sists in building a database to keep the mapping between IP blocks and a geographic location. Several databases are available and are frequently used ... [more ▼]

The most widely used technique for IP geolocation con- sists in building a database to keep the mapping between IP blocks and a geographic location. Several databases are available and are frequently used by many services and web sites in the Internet. Contrary to widespread belief, geolo- cation databases are far from being as reliable as they claim. In this paper, we conduct a comparison of several current geolocation databases -both commercial and free- to have an insight of the limitations in their usability. First, the vast majority of entries in the databases refer only to a few popular countries (e.g., U.S.). This creates an imbalance in the representation of countries across the IP blocks of the databases. Second, these entries do not re- flect the original allocation of IP blocks, nor BGP announce- ments. In addition, we quantify the accuracy of geolocation databases on a large European ISP based on ground truth information. This is the first study using a ground truth show- ing that the overly fine granularity of database entries makes their accuracy worse, not better. Geolocation databases can claim country-level accuracy, but certainly not city-level. [less ▲]

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See detailA Survey on Network Coordinates Systems, Design, and Security
Donnet, Benoît ULg; Gueye, Cheikh Ahmadou Bamba ULg; Kaafar, Mohamed Ali

in IEEE Communications Surveys and Tutorials (2010)

During the last decade, a new class of large-scale globally-distributed network services and applications have emerged. Those systems are flexible in the sense that they can select their communication ... [more ▼]

During the last decade, a new class of large-scale globally-distributed network services and applications have emerged. Those systems are flexible in the sense that they can select their communication path among a set of available ones. However, ceaselessly gathering network information such as latency to select a path is infeasible due to the large amount of measurement traffic it would generate. To overcome this issue, Network Coordinates Systems (NCS) have been proposed. An NCS allows hosts to predict latencies without performing direct measurements and, consequently, reduce the network resources consumption. During these last years, NCS opened new research fields in which the networking community has produced an impressive amount of work. We believe it is now time to stop and take stock of what has been achieved so far. In this paper, we survey the various NCS proposed as well as their intrinsic limits. In particular, we focus on security issues and solutions proposed to fix them. We also discuss potential future NCS developments, in particular how to use NCS for predicting bandwidth. [less ▲]

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See detailCertified Internet Coordinates
Kaafar, Mohamed Ali; Mathy, Laurent ULg; Barakat, Chadi et al

in ICCCN '09 Proceedings (2009, August)

We address the issue of asserting the accuracy of coordinates advertised by nodes of Internet coordinate systems during distance estimations. Indeed, some nodes may lie deliberately about their ... [more ▼]

We address the issue of asserting the accuracy of coordinates advertised by nodes of Internet coordinate systems during distance estimations. Indeed, some nodes may lie deliberately about their coordinates to mount various attacks against applications and overlays. Our proposed method consists in two steps: 1) establish the correctness of a node’s claimed coordinate (which leverages our previous work on securing the coordinates embedding phase using a Surveyor infrastructure); and 2) issue a time limited validity certificate for each verified coordinate. Validity periods are computed based on an analysis of coordinate inter-shift times observed on PlanetLab, and shown to follow a long-tail distribution (lognormal distribution in most cases, or Weibull distribution otherwise). The effectiveness of the coordinate certification method is validated by measuring the impact of a variety of attacks on distance estimates. [less ▲]

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See detailDetecting Triangle Inequality Violations in Internet Coordinate Systems
Kaafar, Mohamed Ali; Cantin, François ULg; Gueye, Cheikh Ahmadou Bamba ULg et al

in Future Networks 2009 (2009, June 18)

Internet Coordinate Systems (ICS) have been proposed as a method for estimating delays between hosts without direct measurement. However, they can only be accurate when the triangle inequality holds for ... [more ▼]

Internet Coordinate Systems (ICS) have been proposed as a method for estimating delays between hosts without direct measurement. However, they can only be accurate when the triangle inequality holds for Internet delays. Actually Triangle Inequality Violations (TIVs) are frequent and are likely to remain a property of the Internet due to routing policies or path inflation. In this paper we propose methods to detect TIVs with high confidence by observing various metrics such as the relative estimation error on the coordinates. Indeed, the detection of TIVs can be used for mitigating their impact on the ICS itself, by excluding some disturbing nodes from clusters running their own ICS, or more generally by improving their neighbor selection mechanism. [less ▲]

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See detailDetecting Triangle Inequality Violations in Internet Coordinate Systems by Supervised Learning
Liao, Yongjun ULg; Kaafar, Mohamed Ali; Gueye, Bamba et al

in Lecture Notes in Computer Science (2009, May 12), 5550

Internet Coordinates Systems (ICS) are used to predict Internet distances with limited measurements. However the precision of an ICS is degraded by the presence of Triangle Inequality Violations (TIVs ... [more ▼]

Internet Coordinates Systems (ICS) are used to predict Internet distances with limited measurements. However the precision of an ICS is degraded by the presence of Triangle Inequality Violations (TIVs). Simple methods have been proposed to detect TIVs, based e.g. on the empirical observation that a TIV is more likely when the distance is underestimated by the coordinates. In this paper, we apply supervised machine learning techniques to try and derive more powerful criteria to detect TIVs. We first show that (ensembles of) Decision Trees (DTs) learnt on our datasets are very good models for this problem. Moreover, our approach brings out a discriminative variable (called OREE), which combines the classical estimation error with the variance of the estimated distance. This variable alone is as good as an ensemble of DTs, and provides a much simpler criterion. If every node of the ICS sorts its neighbours according to OREE, we show that cutting these lists after a given number of neighbours, or when OREE crosses a given threshold value, achieves very good performance to detect TIVs. [less ▲]

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