Catálogo de publicaciones - libros

The Domain Name System Security Extensions (DNSSEC) architecture is based on public-key cryptography. A secure DNS zone has one or more keys and signs its resource records with these keys in order to provide two security services: data integrity and authentication. These services allow to protect DNS transactions and permit the detection of attempted attacks on DNS.

The DNSSEC validation process is based on the establishment of a chain of trust between zones. This chain needs a secure entry point: a DNS zone whose at least one key is trusted. In this paper we study a critical problem associated to the key rollover in DNSSEC: the trusted keys rollover problem. We propose an algorithm that allows a resolver to update its trusted keys automatically and in a secure way without any delay or any break of the DNS service.

Network security is considered one of the obstacles that prevent the wide deployment of ad-hoc wireless networks. Among many security problems, authentication is the most fundamental problem that has to be solved before any others. Some previous solutions requiring centralized entities were not scalable and others requiring physical encounter took a long time. We propose a new architecture, called the Secure Overlay Network (SON), for fully distributed authentication. The SON has scalability because it is constructed in a self-organizing manner. The SON also has NPC-reachability which makes the SON robust against Sybil attacks, and guarantees authentication service between any two nodes in the SON. Both NPC-reachability and simulation results confirm the effectiveness of our architecture.

We propose multilevel transmit power allocation (MTPA) scheme and outer-loop control scheme to increase bandwidth efficiency and to guarantee a required bit error rate (BER). The system considered is orthogonal frequency-code division multiplexing (OFCDM) under slowly-varying frequency-selective Rayleigh fading channels. In the proposed schemes, modulation level and transmit power for each subcarrier is simultaneously controlled corresponding to channel condition to maximize transmitted bits per symbol (BPS) while keeping both total transmit power and BER constant. Computer simulations elucidate that our proposed schemes are effective in terms of throughput and complexity.

This paper proposes a transient(predictive) connection admission control(CAC) scheme using the transient quality of service(QoS) measure for vertical handover between cdma2000 and WLAN. We derive the transient outage probability as the QoS measure using the fluid flow model. We need an approximate approach using fluid flow model for real-time CAC applications. Based on the outage measure, we compare soft QoS-based transient outage performance against traditional hard QoS-based transient outage performance. Numerical results show that the predictive CAC is a promising approach for vertical handover between cdma2000 and WLAN.

In this paper, we propose a new distributed Mobility Prediction based Weighted Clustering Algorithm based on an on-demand distributed clustering algorithm for multi-hop packet radio networks. These types of networks, also known as networks (MANETs) are dynamic in nature due to the mobility of the nodes. The association and dissociation of nodes to and from perturb the stability of the network topology, and hence reconfiguration of the system is often unavoidable. However, it is vital to keep the topology stable as long as possible. The nodes called form a and determine the topology and its stability. Simulation experiments are conducted to evaluate performances of our algorithm and compare them to those of the weighted clustering algorithm (WCA), which does not consider prediction. Results show that our algorithm performs better than WCA, in terms of of the dominant set, of a node between two clusters and in a dominant set.

This paper investigates the problem of resource allocation for quality of service (QoS) support in Orthogonal Frequency Division Multiple Access (OFDMA) based WiBro systems. We identify the key QoS parameters as data rate and bit error rate (BER), which are used to determine the individual traffic demands. We propose a resource allocation algorithm to provide dual-service, Guaranteed Performance (GP) and Best Effort (BE) differentiated on the basis of required QoS. Subcarrier assignment and power allocation are carried out sequentially to reduce the complexity, and GP users are given priority over BE users in assigning subcarrier and allocating power. We present the simulation results of the proposed algorithms applied to frequency selective Rayleigh fading channel with additive white Gaussian noise (AWGN) and OFDMA.

IEEE 802.11 prohibits an exposed node from transmitting any packet until the end of its NAV (Network Allocation Vector). Some trials have been proposed to enable an exposed node, called secondary sender, to transmit its packets in parallel with a primary sender which reserved a wireless channel in advance through RTS/CTS exchange. However, they did not cope with the existence of interference ranges, while they considered only that of transmission ranges. We therefore propose our P-MAC (Parallel MAC) protocol to enable an exposed node to determine whether or not it can succeed in transmitting its data without any collision. Simulation study proves that P-MAC is superior to other schemes in terms of performance metrics.

Recently, it has become possible to collect large amounts of trajectory data of moving objects by using sensor networks. To manage such trajectory data, we have developed a distributed trajectory database composed of a server and many sensor nodes deployed over wide areas. The server manages the trajectory data of each moving object by using indices. However, since each sensor node cannot send trajectory data to the server all the time, the server does not always manage indices for the current trajectory data. In other words, the server is delayed in answering queries for current data because it has to forward each query to the sensor nodes to answer them. This is defined as a . To avoid this problem, we propose a pattern-based predictive indexing method for the database to answer queries in real time. This method uses past motion patterns of moving objects to predict the future locations of moving objects. In this paper, we describe the method and evaluate it with practical trajectory data. We conclude that the technique can predict the future locations of moving objects well enough in real time and show optimal parameters for prediction.

Mobile IP(MIP) and SIP have been proposed to support mobility in the wireless internet working at different layers of the protocol stack. However MIP has some problems such as triangle routing, the need of each host’s home address, the overhead of tunneling and the lack of wide deployment. Thus we proposed a scheme for supporting mobility based on SIP in this research. A novel SIP system to provide a hierarchical registration has been designed according to this scheme. Our SIP system has been established by implementing JAIN technologies which follow next generation network standards to support the mobility of wireless terminal. This system successfully satisfied ITU-T recommandation.

The Web is rapidly increasing its reach beyond the desktop to various devices and the transcoding proxy is appeared to support web services efficiently. Recently, the cooperative transcoding proxy architecture is proposed to improve the system performance to cope with the scalability problem of a stand-alone transcoding proxy. However, because of the multiple versions, the communication protocol of the cooperative caches is very complex and causes additional delay to find best version for a requested object.

In this paper, we propose efficient cooperative transcoding proxy architecture which uses the content-aware caching. The main purpose of the proposed system is simplifying the communication protocol of cooperative caches. We associates a home proxy for each URL and the home proxy is responsible for transcoding and maintaining multiple version of an URL. This mechanism reduces the amount of messages exchanged and communication latency involved. To prevent the hot-spot problem, each proxy cache has the private cache which stores the recently requested objects. We examine the performance of the proposed system by using trace based simulation with Simjava and show the effective enhancement of the cooerative transcoding proxy system.