Catálogo de publicaciones - libros

This paper presents a method for the distribution of video flows through several paths of an IP network. We call the approach focusing on the fact that, from the receiver’s point of view, the stream is obtained from several different sources. A typical use of our procedure is in the design of a P2P network for streaming applications. We implemented a tool in VLC which can send video streaming from multiple sources. In this paper, we describe the method together with the design decisions and the operation characteristics of the tool. Finally we consider, at the receiver side, the perceived quality, automatically measured using the PSQA methodology. We illustrate the work of the tool by means of some tests.

This paper presents a full video delivery network monitoring suite. Our monitoring tool offers a new view of a video delivery network, a view based on the quality perceived by final users. We measure, in real time and automatically, the perceived quality at the client side by means of the recently proposed PSQA technology. Moreover, we improve PSQA’s efficiency and robustness for video analysis by studying the flows at the frame level, instead of the packet level previously considered in the literature. The developed monitoring suite is a completely free-software application, based on well-known technologies such as the Simple Network Management Protocol or the Round Robin Databases, which can be executed in various operating systems. In this paper we explain the tool implementation and we present some of the first experimental measurements performed with it.

It is by now widely accepted that the arrival process of aggregate network traffic exhibits self-similar characteristics which result in the preservation of traffic burstiness (high variability) over a wide range of timescales. This behaviour has been structurally linked to the presence of heavy-tailed, infinite variance phenomena at the level of individual network connections, file sizes, transfer durations, and packet inter-arrival times. In this paper, we have examined the presence of fractal and heavy-tailed behaviour in a number of performance aspects of individual IPv6 microflows as routed over wireless local and wide area network topologies. Our analysis sheds light on several questions regarding flow-level traffic behaviour: whether burstiness preservation is mainly observed at traffic aggregates or is it also evident at individual microflows; whether it is influenced by the end-to-end transport control mechanisms as well as by the network-level traffic multiplexing; whether high variability is independent from diverse link-level technologies, and whether burstiness is preserved in end-to-end performance metrics such as packet delay as well as in the traffic arrival process. Our findings suggest that traffic and packet delay exhibit closely-related Long-Range Dependence (LRD) at the level of individual microflows, with marginal to moderate intensity. Bulk TCP data and UDP flows produce higher Hurst exponent estimates than the acknowledgment flows that consist of minimum-sized packets. Wireless access technologies seem to also influence LRD intensity. At the same time, the distributions of intraflow packet inter-arrival times do not exhibit infinite variance characteristics.

Several analytical models have been developed for both 802.11 Distributed Coordinated Function (DCF) and 802.11e Enhanced Distributed Channel Access (EDCA). However, none of these models considers the 802.11e Contention Free Burst (CFB) mode which allows a given station to transmit more than one frame for each access to the channel. In order to develop a new and complete analytical model including all the differentiation parameters and able to be applied to all network conditions, we first need to know the time occupied by the transmission of a flow belonging to a given AC. The main objective of the current work is to analyze the TXOP bursting procedure and to propose a simple model allowing us to calculate the transmission time occupied by a particular AC when using the CFB mode. CFB performance analysis as well as the proposed model are discussed, demonstrated and validated by means of simulations.

We present a framework of cognitive network management by means of an autonomic reconfiguration scheme. We propose a network architecture that enables intelligent services to meet QoS requirements, by adding autonomous intelligence, based on reinforcement learning, to the network management agents. The management system is shown to be better able to reconfigure its policy strategy around areas of interest and adapt to changes. We present preliminary simulation results showing our autonomous reconfiguration approach successfully improves the performance of the original AODV protocol in a heterogeneous network environment.

This paper proposes an architecture of source-end DDoS protection system on IXP2400 network processor, which monitors traffic from the source network and polices traffic at the source without affecting the traffic from other network. The proposed architecture includes usual IPv4 forwarder with additional modules for source filtering, packet classification and flow control, and uses modified non-parametric CUSUM algorithm. We analyze the major shortcomings of previous approaches, and present basic performance analysis. The proposed system can handle 65,000 aggregated flows, and can operate at OC-48 line rate.

Industrial process control IP networks support communications between process control applications and devices. Communication faults in any stage of these control networks can cause delays or even shutdown of the entire manufacturing process. The current process of detecting and diagnosing communication faults is mostly manual and limited to post-reaction of user complaints which are followed by noticeable process malfunctioning. This paper identifies control network specific failures and their symptoms for early detection.

This short paper presents OSPF-AN protocol, an extension for OSPF protocol aiming for working in Ambient Networks. OSPF-AN adds services information in its database and messages, and as the original OSPF, will be applied in structured networks. This protocol could be applied together with other routing protocols in a scenario of dynamic networks. OMNet++ simulator was used to conduct simulation experiments, thus validating OSPF-AN.

In integrated WLAN and cellular networks, a downward vertical handover (DVHO) causes an abrupt change so that packets which are transmitted through both networks can be out of ordered. Reordering problem triggers unnecessary fast retransmission causing throughput degradation. Thus, we propose a TCP reordering mechanism for DVHO, that suppresses unnecessary retransmissions due to the duplicate acknowledgements (dupacks). The simulation shows that the proposed TCP achieves better performance compared with nodupack with SACK.

This work proposes a XML-based model for the specification of service level agreements (SLA). The model has XML elements to define a semantic to represent key performance indicators (KPI) and key quality indicators (KQI) and the relationship between them. and thresholds are associated to the indicators in order to indicate warnings or errors conditions. The relationship between the indicators is expressed by reusable functions which are evoked by the XML-based model. An example of reusable function for calculating the KQI service availability based on KPI indicators is also presented in this paper.