Cristina Cervello-Pastor

On the optimal allocation of virtual resources in cloud computing networks

Cloud computing builds upon advances on virtualization and distributed computing to support cost-efficient usage of computing resources, emphasizing on resource scalability and on demand services. Moving away from traditional data-center oriented models, distributed clouds extend over a loosely coupled federated substrate, offering enhanced communication and computational services to target end-users with quality of service (QoS) requirements, as dictated by the future Internet vision. Toward facilitating the efficient realization of such networked computing environments, computing and networking resources need to be jointly treated and optimized. This requires delivery of user-driven sets of virtual resources, dynamically allocated to actual substrate resources within networked clouds, creating the need to revisit resource mapping algorithms and tailor them to a composite virtual resource mapping problem. In this paper, toward providing a unified resource allocation framework for networked clouds, we first formulate the optimal networked cloud mapping problem as a mixed integer programming (MIP) problem, indicating objectives related to cost efficiency of the resource mapping procedure, while abiding by user requests for QoS-aware virtual resources. We subsequently propose a method for the efficient mapping of resource requests onto a shared substrate interconnecting various islands of computing resources, and adopt a heuristic methodology to address the problem. The efficiency of the proposed approach is illustrated in a simulation/emulation environment, that allows for a flexible, structured, and comparative performance evaluation. We conclude by outlining a proof-of-concept realization of our proposed schema, mounted over the European future Internet test-bed FEDERICA, a resource virtualization platform augmented with network and computing facilities.

From Delay-Tolerant Networks to Vehicular Delay-Tolerant Networks

This paper provides an introductory overview of Vehicular Delay-Tolerant Networks. First, an introduction to Delay-Tolerant Networks and Vehicular Delay-Tolerant Networks is given. Delay-Tolerant schemes and protocols can help in situations where network connectivity is sparse or with large variations in density, or even when there is no end-to-end connectivity by providing a communications solution for non real-time applications. Some special issues like routing are addressed in the paper and an introductory description of applications and the most important projects is given. Finally, some research challenges are discussed and conclusions are detailed.

An ant-based algorithm for distributed routing and wavelength assignment in dynamic optical networks

Future optical communication networks are expected to change radically during the next decade. To meet the demanded bandwidth requirements, more dynamism, scalability and automatism will need to be provided. This will also require addressing issues such as the design of highly distributed control plane systems and their associated algorithms to respond to network changes very rapidly. In this work, we propose the use of an ant colony optimization (ACO) algorithm to solve the intrinsic problem of the routing and wavelength assignment (RWA) on wavelength continuity constraint optical networks. The main advantage of the protocol is its distributed nature, which provides higher survivability to network failures or traffic congestion. The protocol has been applied to a specific type of future optical network based on the optical switching of bursts. It has been evaluated through extensive simulations with very promising results, particularly on highly congested scenarios where the load balancing capabilities of the protocol become especially efficient. Results on a partially meshed network like NSFNET show that the ant-based protocol outperforms other RWA algorithms under test in terms of blocking probability without worsening other metrics such as mean route length.

With evolution for revolution: managing FEDERICA for future Internet research

Over the last two decades the importance of data networking for human beings and systems has increased beyond any expectation in size, complexity, and impact on society. Today, technology offers the ubiquitous and constant possibility of being connected to the Internet at a wide range of speeds. Traditional management solutions have up to now followed an evolutionary path, although the scale of the Internet and emerging novel architectures such as peer-to-peer, ad hoc networks, as well as virtualization-capable network infrastructures require focused and possibly revolutionary changes in management approaches. This article elaborates on challenges posed by the renaissance of virtualization as experienced in the planning, development, and operation of the FEDERICA infrastructure. The European Community cofunded project FEDERICA, like other worldwide initiatives such as FIND/GENI in the United States, NWGN in Japan, and the FIRE program in Europe, is supporting the development of the future Internet. FEDERICA extends the virtualization capabilities of the current hardware and software to provide a flexible infrastructure to host disruptive testing by networking researchers.

Time shared optical network (TSON): A novel metro architecture for flexible multi-granular services

This paper presents the TSON metro mesh network architecture for guaranteed, statistically-multiplexed services. It proposes tunable time-wavelength assignment, one-way tree-based reservation and node architecture. Results demonstrate high network efficiency, fast service delivery and guaranteed QoS.

Demonstration of C/S based hardware accelerated QoT estimation tool in dynamic impairment-aware optical network

An enhanced version of hardware accelerated QoT estimation tool in impairment-aware optical network is demonstrated and evaluated against the different number of lightpaths and wavelengths per link. It outperforms the software version by 28 times in the order of millisecond.

Enabling future internet research: the FEDERICA case

The Internet, undoubtedly, is the most influential technical invention of the 20th century that affects and constantly changes all aspects of our day-to-day lives nowadays. Although it is hard to predict its long-term consequences, the potential future of the Internet definitely relies on future Internet research. Prior to every development and deployment project, an extensive and comprehensive research study must be performed in order to design, model, analyze, and evaluate all impacts of the new initiative on the existing environment. Taking the ever-growing size of the Internet and the increasing complexity of novel Internet-based applications and services into account, the evaluation and validation of new ideas cannot be effectively carried out over local test beds and small experimental networks. The gap which exists between the small-scale pilots in academic and research test beds and the realsize validations and actual deployments in production networks can be bridged by using virtual infrastructures. FEDERICA is one of the facilities, based on virtualization capabilities in both network and computing resources, which creates custom-made virtual environments and makes them available for Future Internet Researchers. This article provides a comprehensive overview of the state-of-the-art research projects that have been using the virtual infrastructure slices of FEDERICA in order to validate their research concepts, even when they are disruptive to the test beds infrastructure, to obtain results in realistic network environments.

Bundles fragmentation in Vehicular Delay-Tolerant Networks

Vehicular Delay-Tolerant Networks use the delay-tolerant architecture and protocols to overcome the disruptions in network connectivity. These concepts help in cases where the network is sparse or with large variations in density or there is no end-to-end connectivity, by providing a communications solution for non real-time applications. This paper presents data fragmentation techniques to optimize the efficiency of data delivery for the case of the short node contacts that characterize vehicle networks. The techniques were tested in a laboratory environment with portable digital assistants and Lego Mindstorm NXT robotic cars. If no fragmentation is used, only small messages are successfully transferred. Proactive fragmentation fragments messages to a predefined size in the source node. Reactive fragmentation adjusts the fragment sizes to the real duration of the contact when it is broken. Reactive fragmentation showed a good efficiency in adapting the fragmentation in real time to the contact duration. Proactive fragmentation can perform slightly better if the fragment sizes are carefully chosen as it requires less processing. As this choice is difficult, reactive fragmentation is more practical to use.

Analytical blocking probability model for hybrid immediate and advance reservations in optical WDM networks

Immediate reservation (IR) and advance reservation (AR) are the two main reservation mechanisms currently implemented on large-scale scientific optical networks. They can be used to satisfy both provisioning delay and low blocking for delay-tolerant applications. Therefore, it seems reasonable that future optical network provisioning systems will provide both mechanisms in hybrid IR/AR scenarios. Nonetheless, such scenarios can increase the blocking of IR if no quality-of-service (QoS) policies are implemented. A solution could be to quantify such blocking performance based on the current network load and implement mechanisms that would act accordingly. However, current blocking analytical models are not able to deal with both IR and AR. In this paper, we propose an analytical model to compute the network-wide blocking performance of different IR/AR classes within the scope of a multiservice framework for optical wavelength-division multiplexing (WDM) networks. Specifically, we calculate the blocking on two common optical network scenarios using the fixed-point approximation analysis: on wavelength conversion capable and wavelength-continuity constrained networks. Performance results show that our model provides good accuracy compared to simulation results, even in a scenario with multiple reservation classes defined by different book-ahead times.

Distributed contention avoidance in Optical Burst-Switched ring networks

Optical burst switching (OBS) is a promising technology for future optical networks. Due to its less complicated implementation using current optical and electrical components, OBS is seen as the first step towards the future optical packet switching (OPS). Regarding network topologies, the ring is extensively used on current metropolitan environments, and this does not seem it will change in the foreseeable future. In this paper we propose a new medium access protocol for optical burst-switched networks over metropolitan rings that enables the nodes to access the channel in a distributed way. This new protocol avoids burst blockings in transit nodes, turning itself into an efficient and simple burst contention avoidance mechanism. The use of this protocol maximizes the throughput of the network without deteriorating excessively other parameters such as end-to-end delay or ingress queues.