Iosif Ignat

Transparent Fault-Tolerance Based on Asynchronous Virtual Machine Replication

Fault-tolerance of services has received great attention for years, yet it is not clear how this can be done efficiently for different types of services. Current research focuses on finding strategies to provide fault-tolerance using commodity hardware and as independent of the service and transparent to clients as possible. We propose a replication system to provide fault-tolerance for any type of service by running the service instance into a virtual machine and replicate the entire virtual machine using an asynchronous replication strategy. The testing prototype was implemented using Xen hyper visor and an asynchronous replication strategy that gives better replication time than the synchronous one.

Verifying the Independence of Security Protocols

Determining if two protocols can be securely run alongside each other requires analyzing the independence of the involved protocols. In this paper we construct a canonical model of security protocols that allows us to conduct a syntactical analysis on the independence of multiple security protocols. By integrating participant knowledge in the model, we are able to detect subtle multi-protocol attacks, where the types of certain message components can not be checked, also known as type-flaw attacks. Of special interest is the construction of messages in the proposed model, which is made by mapping each message component from the regular specification to a type. We provide a theorem for analyzing the independence of security protocols and illustrate its applicability by analyzing two protocols.

Providing High Data Availability in MedioGRID

High data availability is an important requirement for any data provider system. Replication is the main approach used to improve data availability, which is an inherent method for any distributed infrastructure including grids. The Globus toolkit provides specialized tools and services for data replication in grid, though it is not so simple to know how to deploy, configure and make them work efficiently together in order to obtain the desired level of data availability. Based on our experiments with these tools, we designed an architecture of a data replication management system for the MedioGrid project. Our solution automates the replication process between data storage nodes in the system. We implemented and tested a prototype of our architecture

A value analysis model for measuring software reuse

Software reuse is probably the most elusive promise of OOP but achieving effective reuse requires a significant up-front effort, strict discipline and careful planning while its results are difficult to measure. The lack of clear measurements often hinder a company to measure the degree of success in applying systematic reuse and estimate the organizational gains. The current paper presents an integrated measurement model that allows practitioners to apply familiar project management techniques for measuring software reuse and to include software reuse metrics in the analysis of project performance indicators.

Benchmarking System for QoS Parameters

This paper presents the design and implementation of a benchmarking system for QoS (quality of service). The application generates traffic patterns, measures and computes the QoS parameters and stores and displays the results both in numerical and graphical form. The main advantages of this system are the traffic patterns complexity, the accuracy of the measurements and the user friendly interface. The application is developed in C# language for .NET platform and represents a part of a complex framework designed for developing QoS technologies such as traffic identification and marking, queue and congestion management, traffic shaping and policy, specific protocols.

OrcFS: Organized Relationships between Components of the File System for Efficient File Retrieval

The need for efficient organization of files grows with the computer storage capabilities. However, a classical hierarchical file system offers little help in this matter, excepting maybe the case of links and shortcuts. OrcFS proposes a solution to this problem. By redefining several file system concepts, it allows the user to set custom metadata, in the form of property-value pairs, that describes both files and folders. Using it, the system automatically creates a classified view of the components in which both classical navigation and query interrogation are possible. The enhanced system is compliant with the current applications. A prototype of the project was implemented in user-space using the FUSE library to reimplement system calls. The performed tests proved that even if introducing new data in the OrcFS implies some overhead, this is negligible compared with the gain obtained when searching for files in an immense file tree.

A Pragmatic Analysis Model for Software Reuse

Software reuse is probably the most elusive promise of object oriented programming. Under the current economic constraints achieving high quality software under severe cost constraints is fundamental for the success of software companies, and reuse is a very good way of achieving it. However, achieving effective reuse requires a significant up-front effort, strict discipline and careful planning while its results are difficult to measure. The lack of clear measurements often make it impossible for a company to measure the degree of success in applying reuse and to estimate the organizational gains from applying systematic software reuse. The current paper presents an integrated measurement model that allows practitioners to apply familiar project management techniques for measuring software reuse and to include software reuse metrics in the analysis of project performance indicators.

A self-adapting peer-to-peer logical infrastructure, to increase storage reliability on top of the physical infrastructure

In the case of distributed applications, designed to run for more days with no restart needed, there is a strong need for a self-adapting, even self-organizing, distributed infrastructure, to dynamically solve the issues that might arise, and to adapt the infrastructure to the needs of the distributed application than runs on top of it. A solution for such a distributed logical infrastructure, based on a peer-topeer system, is presented in this paper, in which we describe an enhanced Chord-based DHT, designed to manage the reliability for certain critical pieces of data. Our solution also includes means for self-extension of the application, by integrating new peers, when needed. A preliminary evaluation has been performed, assessing the self-extending feature of our peer-to-peer infrastructure and also the increased reliability that this enhanced DHT is able to provide, by being able to recover presumably lost keys. Future development for our prototype is discussed at the end of the paper, together with our conclusion concerning this work.

Automated composition of security protocols

Determining if two protocols can be securely composed requires analyzing not only their additive properties but also their destructive properties. In this paper we propose a new composition method for constructing protocols based on existing ones found in the literature that can be fully automatized. The additive properties of the composed protocols are ensured by the composition of protocol preconditions and effects, denoting, respectively, the conditions that must hold for protocols to be executed and the conditions that hold after executing the protocols. The non-destructive property of the final composed protocol is verified by analyzing the independence of the involved protocols, a method proposed by the authors in their previous work. The fully automatized property is ensured by constructing a rich protocol model that contains explicit description of protocol preconditions, effects, generated terms and exchanged messages. The proposed method is validated by composing 17 protocol pairs and by verifying the correctness of the composed protocols with an existing tool.

Informal specification-based performance evaluation of security protocols

We propose a performance evaluation method for security protocols. Based on the informal specification, we construct a canonical model which includes, alongside protocol messages, cryptographic operations performed by participants in the process of message construction. Each cryptographic operation is assigned a cost modeled as a function of the size of processed message components. We model not only the size of regular message components but also the size of ciphertext produced by various cryptographic operations. We illustrate the applicability of our method by comparatively analyzing the performance of the original CCITT X.509 protocol and a slightly modified version of the same protocol.