A study of packet losses in the EuQoS network

As Internet usage grows, more efforts are put into analyzing its internal performance, usually such analysis comes through simulation using different models. While simulation can provide a good approximation of network behavior, modeling such a complex network as the Internet is very difficult if not impossible. This paper studies the network’s performance from an experimental point of view using the EuQoS project’s overlay network as a testbed. In the framework of the EuQoS project, many performance tests have been done for proving the reliability of the data transmission. The tests show some rough edges which need further analysis, the most important being random packet losses in UDP flows, and a great amount of out of order packets. This paper focuses on the study of such packet losses, searching for their causes, and more importantly, to show their effects on real-time traffic such as VoIP. As a basis for comparison, the paper also uses TCP traffic to relate the performance of bulk data transfer versus the sustained rate of UDP/RTP flows used for real-time applications. To achieve this goal, several applications are used to generate and capture such traffic and measure its behavior at network level.Peer ReviewedPostprint (author’s final draft

Distributed Sampling for On-line SLA Assessment

New business infrastructures over the Internet pose a new set of traffic constraints. In particular, multimedia and interactive contents require guarantees of bandwidth and delivery time. The broad deployment and real-time nature of this class of applications require the provisioning of specific resources in the network to guarantee a certain level of Quality of Service (QoS). QoS techniques need ways of obtaining feedback about the status of the QoS enabled paths, for example, for checking the fulfilment of Service Level Agreements (SLA). A possible technique for obtaining such feedback is by passively monitoring the network traffic. The issue with traffic monitoring is the additional bandwidth needed by the control traffic generated by the different collection points in order to synchronise its acquired QoS metrics. Moreover, passive monitoring at line speed is an expensive process both in terms of resource consumption and price. However, some of these requirements can be significantly reduced by using traffic sampling. This paper presents a novel methodology for intra-domain on-line distributed QoS monitoring, which makes an efficient use of the network resources by employing distributed sampling mechanisms. The proposal is validated by performing real tests on an European-wide testbed. Our results show that the sampling technique can significantly reduce the traffic overhead, while obtaining very accurate estimations of the One Way Delay performance metricPostprint (published version

Methodology definition for reliable network experimentation

©2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As researchers in the networking area keep adopting experimental network testing as a valid mechanism to develop, validate, and improve their research, it becomes more apparent that an overall framework supporting and assisting during the experimentation process is necessary. Particularly, this assistance is relevant in processes such as experiment preparation, or results validation. As a consequence, the goal, and thus the contribution, of this paper is twofold, on the one hand we propose a novel set of guidelines which establish the set of requirements any testbed for network experimentation should follow. On the other hand, as the other relevant contribution of this work, we propose a mechanism for generating meta-data information on the experiments that ease the publication of the obtained datasets. Finally, as a usecase, we present a particular implementation of this framework which we deploy in a real scenario to prove the capabilities of the proposed testing procedure.This work was partially funded by Spanish Ministry of Science and Innovation under contract TEC2009-07041, and the Catalan Government under contract 2009 SGR1508.Peer ReviewedPostprint (author's final draft

Reducing the effects of routing inaccuracy by means of prediction and an innovative link-state cost

The routing inaccuracy problem is one of the major issues impeding the evolution and deployment of Constraint- Based Routing (CBR) techniques. This paper proposes a promising CBR strategy that combines the strengths of prediction with an innovative link-state cost. The latter explicitly integrates a two-bit counter predictor, with a novel metric that stands for the degree of inaccuracy (seen by the source node) of the state information associated with the links along a path. In our routing model, Link-State Advertisements (LSAs) are only distributed upon topological changes in the network, i.e., the state and availability of network resources along a path are predicted from the source rather than updated through conventional LSAs. As a proof-of-concept, we apply our routing strategy in the context of circuit-switched networks. We show that our approach considerably reduces the impact of routing inaccuracy on the blocking probability, while eliminating the typical LSAs caused by the traffic dynamics in CBR protocols.Postprint (published version

A New Parametric Regenerator Allocation Scheme taking into account Inaccurate Physical Information

Regenerator allocation consists on selecting which of the already installed regenerators in a translucent network may be used according to the dynamic traffic requests in order to maximize the quality of the optical signal while minimizing the opaqueness of the network. A recent study has shown that the performance of the regenerator allocation techniques strongly depends on the accuracy of the physical-layer information. The reason of this physical inaccuracy is the drift suffered by the physical-layer parameters during the operation of the optical network. In these conditions, the performance of the Impairment Aware-Routing and Wavelength Assignment (IA-RWA) process might drop sharply when allocating regenerators inappropriately. In this paper, we propose new regenerator allocation schemes taking into account the inherent and unavoidable inaccuracy in the physical-layer informationPostprint (published version

Cross-layer multimedia quality enforcement through user aware information in wireless networks

Quality assessment of multimedia traffic is a hot topic. In this paper we present a Multimedia Management System, which can be used on-line to assess and guarantee the quality of multimedia traffic in a wired and wireless network. The proposed platform uses both network and application layer metrics to build up a scalable quality assessment framework. The core of this framework provides means for traffic provisioning capabilities by coordinating the network access and usage both from the wireless node and from the network access point. These two combined features permit our platform to guarantee a satisfactory multimedia user experience. We evaluate our proposal by issuing an experimental deployment in a testbed and performing a series of tests under different network situations to demonstrate the Quality of Experience guaranties of our system. The results show that the quality of video perceived by endusers is considerably improved compared to the typical wireless network.Postprint (author’s final draft

Quality of experience based provisioning for service providers

Nowadays Network Operators (NOs) are providing service guaranties to customers by largely overprovisioning their networks, but as the Internet keeps growing, this approach is unveiling important issues in terms of cost and management of the network. To optimize the resource usage, and to reduce the existing overprovisioning, in this paper we present a Cross-layer Autonomic Network Management System that permits Service Providers to perform cost-effective network resource reservation with their NOs. In our novel approach, we use the end-user satisfaction level as the metric used to perform the resource provisioning. We show that our system is capable of achieving a high reduction in operational costs for the Service Providers, while keeping proper bounds in the end-user satisfaction for the offered services.Postprint (author’s final draft

Simple network management provisioning based on quality of experience feedback

This paper presents a promising Autonomic Network Management System (ANMS) that allows Service Providers (SPs) to perform efficient network resource provisioning with their Network Operators (NOs). The novelty of our ANMS is that it offers an starting point to use the end-users perceived quality as a metric to manage the network resources. We show that our system is capable of achieving considerable reductions in the operational costs of SPs, while keeping proper bounds in the end-user satisfaction for the offered multimedia services.Peer ReviewedPostprint (author’s final draft

Quality of experience aware multimedia provisioning with cross-layer network management

This paper presents a Cross-layer Network Management System (NMS) that allows Service Providers (SPs) to perform cost-effective network resource reservations with their Network Operators (NOs). The novelty of our NMS is that it offers a fresh and promising approach to use the endusers satisfaction level as the metric to perform the resource management. We show that our system is capable of achieving considerable reductions in the operational costs of SPs, while keeping proper bounds in the end-user satisfaction for the offered multimedia services.Peer ReviewedPostprint (published version

Improving learning automata-based routing in Wireless Sensor Networks

©2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Recent research in the field of Wireless Sensor Networks (WSNs) has demonstrated the advantages of using learning automata theory to steer the routing decisions made by the sensors in the network. These advantages include aspects such as energy saving, energy balancing, increased lifetime, the selection of relatively short paths, as well as combinations of these and other goals. In this paper, we propose a very simple yet effective technique, which can be easily combined with a learning automaton to dramatically improve the performance of the routing process obtained with the latter. As a proof-of-concept, we focus on a typical learning automata-based routing process, which aims at finding a good trade off between the energy consumed and the number of hops along the paths chosen. In order to assess the performance of this routing process, we apply it on a WSN scenario where a station S gathers data from the sensors. In this typical WSN setting, we show that our combined technique can significantly improve the decisions made with the automata; and more importantly, even though the proof-of-concept particularizes somehow the automata and their behavior, the technique described in this paper is general in scope, and therefore can be applied under different routing methods and settings using learning automata.This work was supported in part by the Spanish Ministry of Science and Innovation under contract TEC2009-07041, and by the Catalan Government under contract 2009 SGR1508.Peer ReviewedPostprint (author's final draft