64 research outputs found
Information diffusion on realistic networks
Prix du meilleur article étudiantNational audienceLes modèles de diffusion d'information mettent traditionnellement en jeu un réseau sous-jacent dont la topologie reproduit certaines propriétés observées dans les réseaux réels. Toutefois, la comparaison des phénomènes de diffusion observés sur des réseaux générés par des modèles classiques avec ceux se produisant au sein de réseaux réels reste peu étudiée. Dans une démarche empiriste, nous proposons dans cette étude d'évaluer l'écart de comportement induit par l'utilisation de divers modèles stylisés, dont notamment certains réseaux dits ``sans-échelle''
Generating Representative ISP Technologies From First-Principles
Understanding and modeling the factors that underlie the growth and evolution of network topologies are basic questions that impact capacity planning, forecasting, and protocol research. Early topology generation work focused on generating network-wide connectivity maps, either at the AS-level or the router-level, typically with an eye towards reproducing abstract properties of observed topologies. But recently, advocates of an alternative "first-principles" approach question the feasibility of realizing representative topologies with simple generative models that do not explicitly incorporate real-world constraints, such as the relative costs of router configurations, into the model. Our work synthesizes these two lines by designing a topology generation mechanism that incorporates first-principles constraints. Our goal is more modest than that of constructing an Internet-wide topology: we aim to generate representative topologies for single ISPs. However, our methods also go well beyond previous work, as we annotate these topologies with representative capacity and latency information. Taking only demand for network services over a given region as input, we propose a natural cost model for building and interconnecting PoPs and formulate the resulting optimization problem faced by an ISP. We devise hill-climbing heuristics for this problem and demonstrate that the solutions we obtain are quantitatively similar to those in measured router-level ISP topologies, with respect to both topological properties and fault-tolerance
The Internet AS-Level Topology: Three Data Sources and One Definitive Metric
We calculate an extensive set of characteristics for Internet AS topologies
extracted from the three data sources most frequently used by the research
community: traceroutes, BGP, and WHOIS. We discover that traceroute and BGP
topologies are similar to one another but differ substantially from the WHOIS
topology. Among the widely considered metrics, we find that the joint degree
distribution appears to fundamentally characterize Internet AS topologies as
well as narrowly define values for other important metrics. We discuss the
interplay between the specifics of the three data collection mechanisms and the
resulting topology views. In particular, we show how the data collection
peculiarities explain differences in the resulting joint degree distributions
of the respective topologies. Finally, we release to the community the input
topology datasets, along with the scripts and output of our calculations. This
supplement should enable researchers to validate their models against real data
and to make more informed selection of topology data sources for their specific
needs.Comment: This paper is a revised journal version of cs.NI/050803
Differentiating complex network models: An engineering perspective
AbstractNetwork models that can capture the underlying network’s topologies and functionalities are crucial for the development of complex network algorithms and protocols. In the engineering community, the performances of network algorithms and protocols are usually evaluated by running them on a network model. In most if not all reported work, the criteria used to determine such a network model rely on how close it matches the network data in terms of some basic topological characteristics. However, the intrinsic relations between a network topology and its functionalities are still unclear. A question arises naturally: For a network model which can reproduce some topological characteristics of the underlying network, is it reasonable and valid to use this model to be a test-bed for evaluating the network’s performances? To answer this question, we take a close look at several typical complex network models of the AS-level Internet as examples of study. We find that although a model can represent the Internet in terms of topological metrics, it cannot be used to evaluate the Internet performances. Our findings reveal that the approaches using topological metrics to discriminate network models, which have been widely used in the engineering community, may lead to confusing or even incorrect conclusions
Scalable Routing Easy as PIE: a Practical Isometric Embedding Protocol (Technical Report)
We present PIE, a scalable routing scheme that achieves 100% packet delivery
and low path stretch. It is easy to implement in a distributed fashion and
works well when costs are associated to links. Scalability is achieved by using
virtual coordinates in a space of concise dimensionality, which enables greedy
routing based only on local knowledge. PIE is a general routing scheme, meaning
that it works on any graph. We focus however on the Internet, where routing
scalability is an urgent concern. We show analytically and by using simulation
that the scheme scales extremely well on Internet-like graphs. In addition, its
geometric nature allows it to react efficiently to topological changes or
failures by finding new paths in the network at no cost, yielding better
delivery ratios than standard algorithms. The proposed routing scheme needs an
amount of memory polylogarithmic in the size of the network and requires only
local communication between the nodes. Although each node constructs its
coordinates and routes packets locally, the path stretch remains extremely low,
even lower than for centralized or less scalable state-of-the-art algorithms:
PIE always finds short paths and often enough finds the shortest paths.Comment: This work has been previously published in IEEE ICNP'11. The present
document contains an additional optional mechanism, presented in Section
III-D, to further improve performance by using route asymmetry. It also
contains new simulation result
Asymptotically-Optimal Incentive-Based En-Route Caching Scheme
Content caching at intermediate nodes is a very effective way to optimize the
operations of Computer networks, so that future requests can be served without
going back to the origin of the content. Several caching techniques have been
proposed since the emergence of the concept, including techniques that require
major changes to the Internet architecture such as Content Centric Networking.
Few of these techniques consider providing caching incentives for the nodes or
quality of service guarantees for content owners. In this work, we present a
low complexity, distributed, and online algorithm for making caching decisions
based on content popularity, while taking into account the aforementioned
issues. Our algorithm performs en-route caching. Therefore, it can be
integrated with the current TCP/IP model. In order to measure the performance
of any online caching algorithm, we define the competitive ratio as the ratio
of the performance of the online algorithm in terms of traffic savings to the
performance of the optimal offline algorithm that has a complete knowledge of
the future. We show that under our settings, no online algorithm can achieve a
better competitive ratio than , where is the number of
nodes in the network. Furthermore, we show that under realistic scenarios, our
algorithm has an asymptotically optimal competitive ratio in terms of the
number of nodes in the network. We also study an extension to the basic
algorithm and show its effectiveness through extensive simulations
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