Catálogo de publicaciones - libros

P2P networks provide a highly reliable way of sharing resources. But the peers have to manage the risk involved due to lack of knowledge about each other’s trustworthiness. Peers could provide different types of services. For the peers to behave honestly, trust needs to be incorporated. The trust framework should enable assessing the peers based on the services provided by them. This paper discusses the design and implementation of a trust framework for evaluating the trust of peers in a network. The trust framework incorporates self experience and reputation to calculate trustworthiness of a peer. Various strategies like Game Tree strategy, Tit for Tat strategy, Self Trust strategy, Dynamic strategy and Auditing strategy are proposed for selecting peers for doing job and the performance is analysed.

In this article we propose an approach which simplifies the task of DBAs in specifying the access constraints on a XML document. In the proposed methodology, for enforcing a security policy on a XML document, the DBA has to specify access constraints in terms of easy to understand Declarative Access Control Specification (DACS) language primitives. Once the constraints are specified, their corresponding security views are generated by the proposed implemented system. A working prototype based on above approach is also presented.

Confidentiality and authenticity are two important security services required for almost every WSN application. However, small memory, weak processor and limited battery power of the sensor nodes are the major obstacles to implement traditional security primitives in them. Owing to both, the requirement as well as the obstacles, this paper proposes a LIghtweight Security Algorithm (LISA) tailored to implement in resource restrained sensor nodes. The novelty of this scheme is that it achieves both, confidentiality and authenticity of data, without using traditional encryption algorithm.

Pricing is an effective tool to control congestion and achieve quality of service (QoS) provisioning for multiple differentiated levels of service. In this paper, we consider the problem of pricing for congestion control in the case of a network of nodes under a single service class and multiple queues, and present a multi-layered pricing scheme. We propose an algorithm for finding the optimal state dependent price levels for individual queues, at each node. The pricing policy used depends on a weighted average queue length at each node. This helps in reducing frequent price variations and is in the spirit of the random early detection (RED) mechanism used in TCP/IP networks. We observe in our numerical results a considerable improvement in performance using our scheme over that of a recently proposed related scheme in terms of both throughput and delay performance. In particular, our approach exhibits a throughput improvement in the range of 34 to 69 percent in all cases studied (over all routes) over the above scheme.

Virtual Network Operators lease bandwidth from different data carriers to offer well managed Virtual Private Networks. By using proprietary algorithms and leased resource diversity they can offer Quality of Service, at competitive prices, which is difficult to attain from traditional data network operators. In this paper, we describe a novel distributed resource management approach, based on an economic model, that allows continuous optimizing of the network profit, while keeping network blocking constraints. The approach integrates leased link capacity adaptations, based on measurements, with connection admission control and routing policies. This is done in the framework that applies decomposition of Markov Decision Process. Our numerical analysis validates the approach and shows the convergence and stability of the adaptation as functions of measurement parameters.

This paper proposes a centralized tree structure based routing protocol. It is based on a greedy heuristic to maximize wireless sensor network lifetime. The proposed heuristic results in greater lifetime has been compared with naive heuristic used earlier in literature. The proposed design uses residual energy for the construction of tree which makes high energy sensor nodes nearer to base station. Rigorously the algorithm is tested using simulation and found that the lifetime is improved significantly compared to the available well known greedy solutions respectively.

In this paper, we address the problem of building and maintaining dynamic overlay networks on top of physical networks for the autonomous scheduling of divisible load Grid applications. While autonomous scheduling protocols exist to maximize steady-state throughputs for given overlay networks, not much work has been done on building the most efficient overlay. In our work, nodes use the bandwidth-centric principle to select other nodes with which overlay edges must be formed dynamically. The node which has the entire dataset initially (the scheduler) starts forming the overlay and the nodes which receive tasks at rates greater than their task execution rates further expand it. We use simulation studies to illustrate the functioning of our overlay forming mechanism, and its robustness to changes in the characteristics of the system resources.

Commercial Content Delivery Networks (CDN) compete each other and are forced to set up costly infrastructure around the globe to effectively deliver Web content to the end-users. Huge financial cost involved in setting up commercial CDN compels the commercial CDN providers to charge high remuneration from their clients (the content providers). Academic models of peer-to-peer CDNs aim to reduce the financial cost of content distribution by forming volunteer group of servers around the globe. But their efficiency is at the mercy of the volunteer peers whose commitment is not ensured in their design. We propose a new architecture that will make use of the existing resources of common Internet users in terms of storage space, bandwidth and Internet connectivity to create a Distributed Content Delivery Network (DCDN). The profit pool generated by the infrastructure savings will be shared among the participating nodes (DCDN surrogates) which will function as an incentive for them to support DCDN.

Recent work has shown that the durability of large-scale storage systems such as DHTs can be predicted using a Markov chain model. However, accurate predictions are only possible if the model parameters are also estimated accurately. We show that the Markov chain rates proposed by other authors do not consider several aspects of the system’s behavior, and produce unrealistic predictions. We present a new analytical expression for the chain rates that is condiderably more fine-grain that previous estimations. Our experiments show that the loss rate predicted by our model is much more accurate than previous estimations.

This paper presents a new approach to provide fault tolerance in MPLS multicast networks. MPLS has been used to provide faster forwarding; combining with multicasting it further supports applications with improved service. Fault tolerance is therefore important for such networks. Our strategy for fault tolerance is to divide and encode the traffic into multiple disjoint trees using a modified () Threshold Sharing scheme. Our scheme can reconstruct the original traffic from any out of trees available. Therefore, in the event of node/link failure(s) of any () trees, our approach provides fault tolerance without introducing any recovery delay and packet loss. Moreover, our objective is also to minimize bandwidth utilization for protection purposes.