Bachar Wehbi

Timed Extended Invariants for the Passive Testing of Web Services

The service-oriented approach is becoming more and more popular to integrate highly heterogeneous systems. Web services are the natural evolution of conventional middleware technologies to support Web-based and enterprise level integration. Formal testing of such Web-based technology is a key point to guarantee its reliability. In this paper, we choose a non-intrusive approach based on monitoring to propose a conformance passive testing methodology to check that a composed Web service respects its functional requirements. This methodology is based on a set of formal invariants representing properties to be tested including data and time constraints. Passive testing of an industrial system (that uses a composition of Web services) is briefly presented to demonstrate the effectiveness of the proposed approach.

Events-Based Security Monitoring Using MMT Tool

MMT (Montimage Monitoring Tool) is a monitoring solution that combines: data capture, filtering and storage, events extraction, statistics collection, traffic analysis and reporting. In the context of the PIMI and DIAMONDS projects, Montimage is developing MMT-Security: a security analysis solution (part of MMT) that inspects network traffic against a set of security properties denoting both security rules and attacks. This tool has been applied to an industrial case study provided by Thales Group that consists of a QoS-aware ad-hoc radio communication protocol.

Estimation of video QoE from MAC parameters in wireless network: A Random Neural Network approach

Supporting real time video transmission over wireless networks is very challenging. The video flow characteristics can be vulnerable to the time-varying channel conditions and the unreliability of the MAC (Medium Access Control) can substantially degrade Quality of Experience (QoE) in wireless networks. QoE reflects the satisfaction level of a user towards a particular service or application. It can be a valuable input to service providers and help them to enhance the quality of the overall system. In this work, we present a methodology and a system based on Random Neural Network (RNN) to analyze the impact of different MAC-level parameters on video QoE over IEEE 802.11n wireless networks. At first, subjective tests are performed to correlate MAC-level parameters with users perceived video QoE. Secondly, we propose a RNN technique to estimate the impact of these parameters on video QoE. The experimental results show that the proposed method can effectively measure the impact of MAC-level parameters on video QoE. The acceptable correlation between subjective QoE and estimated QoE verifies the validity of the obtained results.

Light Client Management Protocol for Wireless Mesh Networks

The future of wireless networks evolves toward more simple ways for users to get connected while on the move. In this perspective, Wireless Mesh Networks constitutes one of the key technologies for next generation wireless networks. In this paper we present LCMP, a new protocol for client management in wireless mesh networks. LCMP performs on-demand path setup for clients and supports clients mobility by introducing new light mechanisms that take full advantage of the mesh architecture. The work on LCMP and mesh routing is still in progress at LOMNT laboratory. In this papel; we highlight some ongoing work.

Transmit and Reserve (TAR): A Coordinated Channel Access for IEEE 802.11 Networks

This paper considers the medium access problem in the IEEE 802.11 standard. Although the transmission bit rates have clearly increased, some MAC related problems remain yet unsolved. The random channel contention suffers from short term unfairness and from the considerable reduction of the effective throughput due to the collision probability that increases with the number of contending nodes in the network. Our objective is to define a coordinated access mechanism that improves the effective throughput and grants a fair sharing of network resources among the different nodes. We propose Transmit And Reserve (TAR), a novel packet based coordinated channel access mechanism that combines advantages of random access and channel assignment. The idea of TAR mechanism is simple: Prior to transmitting a packet, the sender node selects in advance the backoff value for its next packet and advertises this selection within the currently transmitted packet. The neighbor nodes avoid then choosing the same backoff value as the advertised one. The simulation results showed that TAR leads to higher throughput and fairness, and lower collision rate than IEEE 802.11. TAR adapts fast to the network load and to the number of active nodes.

Distributed Monitoring in Ad Hoc Networks: Conformance and Security Checking

Ad hoc networks are exposed more than traditional networks to security threats due to their mobility and open architecture aspects. In addition, any dysfunction due to badly configured nodes can severely affect the network as all nodes participate in the routing task. For these reasons, it is important to check the validity of ad hoc protocols, to verify whether the running implementation is conform to its specification and to detect security flows in the network. In this paper, we propose a formal methodology to collect and analyze the network traffic trace. Observers running on a set of nodes collect local traces and send them later to a global observer that correlates them into a global trace thanks to an adapted time synchronization mechanism running in the network. The global trace is then analyzed to study the conformance and the security of the running routing protocol. This analysis is performed using dedicated algorithms that check the collected trace against a set of functional and security properties specified in an adapted formal language.

TAR channel access mechanism for VANET safety-critical situations

Vehicular Ad-hoc Network (VANET) is among the most relevant forms of mobile ad-hoc networks. VANET helps improving traffic safety and efficiency. By exchanging information between each others, vehicles can warn drivers or even prepare for dangerous situation. These warnings can be about critical situations like vehicles merging in a highway. Detecting and warning about such situations require a reliable communication between vehicles increasing thus the need for an efficient medium access control (MAC) protocol. In this paper, we propose to apply Transmit And Reserve (TAR), an ad-hoc medium access protocol, to vehicular communications. We integrated TAR into NS-3 simulator and evaluated its performance compared to IEEE 802.11 DCF in a vehicular network context. The evaluation results show that TAR is an efficient medium access protocol for VANET critical situations as it increases the throughput reduces the medium access delays and provides close to optimal short term fairness.

Practical Experience Gained from Passive Testing of Web Based Systems

In recent years Web-based systems have become extremely popular and, nowadays, they are used in critical environments such as financial, medical, and military systems. As the use of Web applications for security-critical services has increased, the number and sophistication of attacks against these applications have grown as well. For this reason it is essential to be able to prove that the target Web-based system implements its designed security requirements avoiding known vulnerabilities in HTTP-based solutions. To reach this aim, we can rely on several testing techniques and mainly on security passive testing approach that is becoming increasingly important to security-relevant aspects into web based software systems. This article describes the application of the TestInv-P passive testing tool as part of the testing phase of TXT e-tourism Web application. TestInv-P is a passive testing tool that monitors communication traces of an application during run-time and verifies whether it satisfies certain security-related invariants derived from SHIELDS models.

TAR Channel Access Mechanism: A Study of a Highway Ramp Car Merge Case

Road critical situations like vehicles merging in a highway require a tight coordination between car drivers within a short time while vehicles are driving at high velocity. Any driver misbehavior or error may result in a car accident. Car communication offering information exchange in timely manner may drastically help drivers to accomplish this task and avoid incidents. Unfortunately, communication standard like 802.11p are not well dimensioned to guarantee the requirement of this kind of data exchange. In this paper we propose to use the Transmit And Reserve (TAR), an ad-hoc medium access protocol, for vehicular communications. We provide a study to demonstrate its adaptivity and short time fairness with regard to different highway car traffic conditions and we focus on a typical use case of a highway ramp car merge to show its efficiency.

An Effective Attack Detection Approach in Wireless Mesh Networks

Wireless Mesh Network (WMN) is a recent technology that is gaining significant importance among traditional wireless networks. WMN is considered a suitable solution for providing Internet access in an inexpensive, convenient, and rapid manner. Nonetheless, WMNs are exposed to various types of security threats due to their intrinsic characteristics such as open broadcast medium and decentralized architecture. For instance, a compromised node can generate malicious traffic in order to disrupt the network routing service, putting the entire mesh network at risk. In this paper, we provide an efficient method for detecting active attacks against the routing functionality of network. The approach is based on the analysis of the protocol routing behavior by processing the traces produced by each node using Mont image Monitoring Tool (MMT), which outputs routing events that are correlated between nodes to detect potential intrusions. We demonstrate the approach feasibility by using a virtualized mesh network platform that consists of virtual nodes executing Better Approach To Mobile Ad hoc Network (BATMAN) routing protocol. The experimental results show that the proposed method accurately identifies malicious routing traffic diffused by an attacker through the network.