Catálogo de publicaciones - libros

3sons is a distributed overlay network services framework based on hierarchal semi-structured topology. Its excellent characters include good scalability,high utilization rate of network resources and strong robustness. Every node of 3Sons maintains two static neighbors and dynamic neighbors, which can guarantee network connectivity and improve the success rate of fuzzy lookup. 3Sons can effectively reduce the average lookup length and improve transmission performance by adjusting dynamic neighbors and optimizing forward routes according to current traffic of network. The simulation results show that 3Sons can get higher lookup success rate with shorter average lookup length, and lower fuzzy lookup workload of network, so that it can better support large-scale overlay service.

A core challenge in peer-to-peer systems is efficient location of large numbers of nodes or data sources. This paper proposes a novel catalog search for the large distributed XML data sources based on consistent hashing, and the improved algorithm is given to speed the key location. Utilizing this model with data summary can quickly process queries for XML repositories. Results from performance simulation show that our approach has significant improvement.

In this paper, we study problem of impatient packets in multimedia multi-access communication channel. Impatient users generally mean the users who leave the system if their service is not started before their respective deadlines. Their characteristic is perfect match to that of the packets with hard delay bound in real-time communication. In real-time communication, one of the most critical performance measure is the percentage of packets that are transmitted within hard delay bound. We assume contention based reservation ALOHA type MAC protocol, which is basic framework in next generation multimedia wireless LAN, and develop analytical model for the performance evaluation of defection probability of impatient packets. Our results show that proposed model is strong tool to evaluate packet loss probability due to expiration of deadline in contention based MAC protocols, which matches well with the simulation results.

A home network may have various equipment such as home appliances, PCs and other small electronic devices. Current trend is to make these devices have Internet connectivity. NAT (Network Address Translation) is a short-term solution of IP depletion problem and is widely used to construct home networks. Most of the existing NAT techniques support only unidirectional communication, i.e., connections from a local network to the public network. Though AVES (Address Virtualization Enabling Service) technique provides a bidirectional communication service to the NAT network, it is restrictive in a sense that it requires application level gateways which not only degrades performance but also is vulnerable in security. In this paper, we propose FSL3/4 aware DNS server for supporting bidirectional communication between NEDIA and external network. We also analyze the proposed method by comparing it with other methods which support bidirectional communication.

Packet losses are bursty in nature since the dominant reason is temporary overload situations in the shared resources over networks. To increase the effectiveness of forward error correction (FEC) schemes, adaptive FEC schemes have been suggested, where the amount of redundancy is controlled according to current network status. In this paper, we propose a gap- based adaptive FEC scheme, which is motivated by the Markov gap model for packet losses, and show that the gap-based adaptive FEC scheme performs better than the adaptive FEC scheme based on the Gilbert model.

In a new optical hybrid switching environment which combined Optical Burst Switching (OBS) and Optical Circuit Switching (OCS), we propose flow-level service classification scheme for IP differentiated service. In particular, this classification scheme classifies incoming IP traffic flows into short-lived and long-lived flows for Quality of Service (QoS) provisioning according to traffic characteristics such as flow bandwidth, loss and delay. In this hybrid switching, the short-lived flows including delay sensitive traffic use OBS and the long-lived flows including loss-sensitive traffic use OCS. Therefore, optical hybrid switching network can take advantages of both switching technologies using the proposed flow classification scheme. The aim of proposed technique is to maximize network utilization while satisfying user’s QoS requirements

Differentiated services (DiffServ) has been widely accepted as the service model to adopt for providing quality-of-service (QoS) over the next-generation IP networks. There is a growing need to support QoS in mobile ad hoc networks. Supporting DiffServ in mobile ad hoc networks, however, is very difficult because of the dynamic nature of mobile ad hoc networks, which causes network congestion. The network congestion induces long transfer packet delay and low throughput which make it very difficult to support QoS in mobile ad hoc networks. We propose DiffServ module to support differentiated service in mobile ad hoc networks through congestion control. Our DiffServ module uses the periodical rate control for real time traffic and also uses the best effort bandwidth concession when network congestion occurs. Network congestion is detected by measuring the packet transfer delay or bandwidth threshold of real time traffic. We evaluate our mechanism via a simulation study. Simulation results show our mechanism may offer a low and stable delay and a stable throughput for real time traffic in mobile ad hoc networks.

We propose an extensible exploit framework for automation of penetration testing (or pen-testing) without loss of safety and describe possible methods for sanitizing unreliable code in each part of the framework. The proposed framework plays a key role in implementing HackSim a pen-testing tool that remotely exploits known buffer-overflow vulnerabilities. Implementing our enhanced version of HackSim for Solaris and Windows systems, we show the advantages of our sanitized pen-testing tool in terms of safety compared with existing pen-testing tools and exploit frameworks. This work is stepping toward a systematic approach for substituting difficult parts of the labor-intensive pen-testing process.

We describe the extended Hadamard matrices named Jacket in terms of combinatorial designs, and show that the center weighted Jacket matrices belong to a class of cocyclic matrices. Additionally, a simple public key exchange system on cocylcic Jacket matrices is proposed.

Session Initiation Protocol (SIP) is the Internet Engineering Task Force (IETF) standard for IP telephony. It is the most promising candidate as a signaling protocol for the future IP telephony services. Comparing with the reliability provided by the traditional telephone systems, there is an obvious need to provide a certain level of quality and security for IP telephony. The problem of security is tightly related to the signaling mechanisms and the service provisioning model. Therefore, there is a very hot topic in the SIP and IP telephony standardization for security support. In this paper, we propose a security mechanism for SIP-based voice over IP (VoIP) systems. Specifically, we focus on the design and implementation of SIP authentication for VoIP users. The performance issues for our secure SIP-based VoIP systems are also investigated. By means of a real testbed implementation, we provide an experimental performance analysis of our SIP security mechanisms, and compare the performance with the methods described in standardization.