24 research outputs found
Fundamental Limits on Communication for Oblivious Updates in Storage Networks
In distributed storage systems, storage nodes intermittently go offline for
numerous reasons. On coming back online, nodes need to update their contents to
reflect any modifications to the data in the interim. In this paper, we
consider a setting where no information regarding modified data needs to be
logged in the system. In such a setting, a 'stale' node needs to update its
contents by downloading data from already updated nodes, while neither the
stale node nor the updated nodes have any knowledge as to which data symbols
are modified and what their value is. We investigate the fundamental limits on
the amount of communication necessary for such an "oblivious" update process.
We first present a generic lower bound on the amount of communication that is
necessary under any storage code with a linear encoding (while allowing
non-linear update protocols). This lower bound is derived under a set of
extremely weak conditions, giving all updated nodes access to the entire
modified data and the stale node access to the entire stale data as side
information. We then present codes and update algorithms that are optimal in
that they meet this lower bound. Next, we present a lower bound for an
important subclass of codes, that of linear Maximum-Distance-Separable (MDS)
codes. We then present an MDS code construction and an associated update
algorithm that meets this lower bound. These results thus establish the
capacity of oblivious updates in terms of the communication requirements under
these settings.Comment: IEEE Global Communications Conference (GLOBECOM) 201
The Price of Updating the Control Plane in Information-Centric Networks
We are studying some fundamental properties of the interface between control
and data planes in Information-Centric Networks. We try to evaluate the traffic
between these two planes based on allowing a minimum level of acceptable
distortion in the network state representation in the control plane. We apply
our framework to content distribution, and see how we can compute the overhead
of maintaining the location of content in the control plane. This is of
importance to evaluate content-oriented network architectures: we identify
scenarios where the cost of updating the control plane for content routing
overwhelms the benefit of fetching a nearby copy. We also show how to minimize
the cost of this overhead when associating costs to peering traffic and to
internal traffic for operator-driven CDNs.Comment: 10 pages, 12 figure
A Lightweight Distributed Solution to Content Replication in Mobile Networks
Performance and reliability of content access in mobile networks is
conditioned by the number and location of content replicas deployed at the
network nodes. Facility location theory has been the traditional, centralized
approach to study content replication: computing the number and placement of
replicas in a network can be cast as an uncapacitated facility location
problem. The endeavour of this work is to design a distributed, lightweight
solution to the above joint optimization problem, while taking into account the
network dynamics. In particular, we devise a mechanism that lets nodes share
the burden of storing and providing content, so as to achieve load balancing,
and decide whether to replicate or drop the information so as to adapt to a
dynamic content demand and time-varying topology. We evaluate our mechanism
through simulation, by exploring a wide range of settings and studying
realistic content access mechanisms that go beyond the traditional
assumptionmatching demand points to their closest content replica. Results show
that our mechanism, which uses local measurements only, is: (i) extremely
precise in approximating an optimal solution to content placement and
replication; (ii) robust against network mobility; (iii) flexible in
accommodating various content access patterns, including variation in time and
space of the content demand.Comment: 12 page
Review on the Simulation of Cooperative Caching Schemes for MANETs
In this paper, a review of the main simulation parameters utilized to evaluate the performance of
cooperative caching schemes in Mobile Ad Hoc Networks is presented. Firstly, a taxonomy of twenty five
caching schemes proposed in the literature about Mobile Ad Hoc Networks is defined. Those caching schemes
are briefly described in order to illustrate their basis and fundamentals. The review takes into consideration the
utilized network simulator, the wireless connection standard, the propagation model and routing protocol, the
employed simulation area and number of data servers, the number of mobile devices and their coverage area, the
mobility model, the number of documents in the network, the replacement policy and cache size, the mean time
between requests, the document popularity distribution, the TTL (Time To Live) of the documents and the
simulation time. Those simulation parameters have been compared among the evaluation of the studied
cooperative caching schemes in order to obtain the most common utilized values. This work will allow to compare
the performance of the proposed cooperative caching schemes using a common simulation environment.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
Proactive seeding for information cascades in cellular networks
Abstract—Online social networks (OSNs) play an increasingly important role today in informing users about content. At the same time, mobile devices provide ubiquitous access to this content through the cellular infrastructure. In this paper, we exploit the fact that the interest in content spreads over OSNs, which makes it, to a certain extent, predictable. We propose Proactive Seeding– a technique for minimizing the peak load of cellular networks, by proactively pushing (“seeding”) content to selected users before they actually request it. We develop a family of algorithms that take as input information primarily about (i) cascades on the OSN and possibly about (ii) the background traffic load in the cellular network and (iii) the local connectivity among mobiles; the algorithms then select which nodes to seed and when. We prove that Proactive Seeding is optimal when the prediction of information cascades is perfect. In realistic simulations, driven by traces from Twitter and cellular networks, we find that Proactive Seeding reduces the peak cellular load by 20%-50%. Finally, we combine Proactive Seeding with techniques that exploit local mobile-to-mobile connections to further reduce the peak load. I