Cyril Rabat

Grid of Security: A New Approach of the Network Security

Network security is in a daily evolving domain. Every day, new attacks, virus or intrusion techniques are released. Hence, network devices, enterprise servers or personal computers are potential targets of these attacks. Current security solutions like firewalls, intrusion detection systems (IDS) and virtual private networks (VPN) are centralized solutions which rely mostly on the analyze of inbound network connections. This approach notably forgets the effects of a rogue station, whose communications cannot be easily controlled unless the administrators establish a global authentication policy using methods like 802.1x to control all network communications among each device. To the best of our knowledge, a distributed and easily manageable solution for the global security of an enterprise network does not exist. In this paper, we present a new approach to deploy a distributed security solution where communication between each device can be control in a collaborative manner. Indeed, each device has its own security rules, who can be shared and improved through exchanges with others devices. With this new approach, called grid of security, a community of devices ensures that a device is trustworthy and that communications between devices progress in respect of the control of the system policies. To support this approach, we present a new communication model that helps structuring the distribution of security services among the devices. Like this, we can secure both ad-hoc, local-area or enterprise networks in a decentralized manner, preventing the risk of a security breach in the case of a failure.

A random walk topology management solution for grid

GRID computing is a more and more attractive approach. Its aim is to gather and to share the resources of a network like the content, the storage or CPU cycles. A computational distributed system like SETI@home produces a power up to 70 TFlops whereas the current best parallel supercomputer BlueGene produces a power of 140 TFlops. Such a supercomputer costs very much contrary to a system like SETI@home. But the use of many computers to increase the global computational power involves several communication problems. We must maintain the GRID communication in order to make any type of computation even though the network is volatile. In this paper, we present a model to represent GRID applications and networks in order to show faults impacts. We present a fully distributed solution based on a random walk to manage the topology of the GRID. No virtual structure needs to be maintained and this solution works on asynchronous networks. We also present some simulations of our solution.

Decentralized resources management for grid

Among all components of a grid or peer-to-peer application, the resources management is unavoidable Indeed, new resources like computational power or storage capacity must be quickly and efficiently integrated This management can be achieved either by a fully centralized way (BOINC) or by a hierarchical way (Globus, DIET) In the latter case, there is a greater flexibility and a greater scalability But the counterpart is the difficulty to design and to deploy such a solution, particularly if the resources are volatile. In this article, we combine random walks and circulating word to derive a fully distributed solution to the resources management Random walks have proved their efficiency in distributed computing and are well suited to dynamical networks like peer-to-peer or grid networks There is no condition on nodes lifetime and we need only one application for each node.

Simulation of large scale WSN for medical care

The aim of this study is to perform a simulation of large scale Wireless Sensor Networks (WSN) working on medical diagnosis. The main feature of this WSN is its density and the fact that all sensors are in the same radio range. Our approach helps medical staff to diagnose diseases in an automatic way. In this context, each patient is equipped to a set of sensors. Each sensor is connected to a transducer dedicated to measure a specific health parameter. This WSN will perform some computations and run an alarm when some diseases are suspected. This technique is based on the population protocol to handle data exchanged between sensors. This approach is in fact an efficient distributed algorithm which implies that the diagnose may be done by any sensor dealing with the disease detection. The main result of this paper is the approach supports large scalability which proves its practicability for real cases.

Fully Distributed Active and Passive Task Management for Grid Computing

The task management is a key point in grid applications and can highly influence their efficiency. There are many solutions that we can classify according to their centralization degree: fully centralized, semi-distributed and fully distributed. A fully distributed approach leaves the nodes in charge of the scheduling: the schedule is performed thanks to the local view of the system. Such a local treatment reduces the communication cost but it must not impact on the computational power devoted to applications. This kind of solution seems to be more scalable and flexible than a centralized one, especially in a highly volatile environment like peer-to-peer networks. In this article, we propose two fully distributed solutions for the task management based on random walks. We choose to maximize the computational power of nodes by reducing the maintenance cost of an underling structure (a spanning structure). So, it reduces the number of control message exchanges that is a critical point in networks with a low bandwidth or in which the energy of nodes must be saved. We analyze two methods called passive and active and we present some simulation results.

Integrated tool for testing timed systems

Some new protocols handle time constraints to model important aspects (delays, timeouts, ..). This issue has to be taken into account in every step during its development life cycle, in particular in the testing step. This paper presents an integrated tool which permits to specify a timed system in various models (RT-LOTOS, IF, Timed automata) and then generates test sequences using a new efficient algorithm. Illustrated examples show the differents steps of this new test generation method.

A self-adaptive structuring for P2P-based grid

Grids that use the concept of services are generally based on highly centralized hierarchical architectures. The main issue of this centralization is the unified management of resources, but it is difficult to react rapidly against failure that can affect grid users. Therefore, in our previous works, we proposed a specification called P2P4GS for services management in a grid-computing environment based on peer-to-peer paradigm. In this approach, all nodes can participate to the deployment and the discovery processes for a given service. In addition, each node maintains a table called “Service Registry”, which lists the services owned by this node, as well as the other services located inside the grid and learned during a discovery process. However, the growth of the distributed systems size, in terms of number of nodes, services and users, raises the question of scalability. In this paper, we propose to limit the knowledge about the location of grid services on some nodes that we call ISP (Information System Proxy). Around each ISP, we form a community constituted by a set of nodes of the grid. In order to reduce the ISP overload, on the one hand, we delegate invocation and execution services tasks for nodes called IP (Invocation Proxy). On the other hand, we memorize information about the location of frequently requested services on LP (Location Proxy) nodes.

Fully Distributed and Fault Tolerant Task Management Based on Diffusions

The task management is a critical component for the computational grids. The aim is to assign tasks on nodes according to a global scheduling policy and a view of local resources of nodes. A peer-to-peer approach for the task management involves a better scalability for the grid and higher fault tolerance. But some mechanisms have to be proposed to avoid the computation of replicated tasks that can reduce the efficiency and increase the load of nodes. In the same way, these mechanisms have to limit the number of exchanged messages to avoid the overload of the network.In previous work, we have proposed two methods for the task management called active and passive. These methods rebased on a random walk: they are fully distributed and fault tolerant. Each node owns a local tasks states set updated thanks to a random walk and each node is in charge of the local assignment. Here, we propose three methods to improve the efficiency of the active method. These new methods are based on a circulating word. The nodes local tasks states sets are updated thanks to periodical diffusions along trees built from the circulating word. Particularly, we show that these methods increase the efficiency of the active method: they produce less replicated tasks. These three methods are also fully distributed and fault tolerant. On the other way, the circulating word can be exploited for other applications like the resources management or the nodes synchronization.