Joaquín Salvachúa

Adaptive Provisioning of Stream Processing Systems in the Cloud

With the advent of data-intensive applications that generate large volumes of real-time data, distributed stream processing systems (DSPS) become increasingly important in domains such as social networking and web analytics. In practice, DSPSs must handle highly variable workloads caused by unpredictable changes in stream rates. Cloud computing offers an elastic infrastructure that DSPSs can use to obtain resources on-demand, but an open problem is to decide on the correct resource allocation when deploying DSPSs in the cloud. This paper proposes an adaptive approach for provisioning virtual machines (VMs) for the use of a DSPS in the cloud. We initially perform a set of benchmarks across performance metrics such as network latency and jitter to explore the feasibility of cloud-based DSPS deployments. Based on these results, we propose an algorithm for VM provisioning for DSPSs that reacts to changes in the stream workload. Through a prototype implementation on Amazon EC2, we show that our approach can achieve low-latency stream processing when VMs are not overloaded, while adjusting resources dynamically with workload changes.

VaaS: Videoconference as a service

Internet is a place nowadays where interoperating services are offered which can be integrated or mashed up in order to fulfill user demands. This paper proposes a way to offer videoconference as a Web service over an interface which can be used by third parties to enrich their applications. This interface includes a security mechanism supporting delegated authorization to allow integration into third partys environments. Via this interface virtual rooms are provided where users can collaborate with audio, video, shared applications, IM, etc. An implementation of these concepts is described, including performance figures and validation results. We would finally like to stress that this architecture has been defined to support a scalable cloud computing service over the Internet.

Tool support to implement LOTOS formal specifications

Abstract LOTOS is a specification language that aims to describe the dynamic behavior of complex systems. To a large extent, LOTOS semantics is operational, which gives an opportunity to execute the specifications. There may be several targets in specification execution, three of which are considered in the paper: rapid prototyping, system testing, and real product derivation. The outstanding problem is to map abstract entities onto real entities, both to effectively act on the environment, and to allow the environment to influence specification behavior. For a final product, performance must be assessed too, as well as other non-functional requirements. The paper describes the opportunities provided by TOPO, a compiler from LOTOS into either C or Ada code. Supported features are described and wrapped into a method. Performance figures are provided too, in order to make estimates on realization performance after the specification style.

Testing a Cloud Provider Network for Hybrid P2P and Cloud Streaming Architectures

The number of online real-time streaming services deployed over network topologies like P2P or centralized ones has remarkably increased in the recent years. This has revealed the lack of networks that are well prepared to respond to this kind of traffic. A hybrid distribution network can be an efficient solution for real-time streaming services. This paper contains the experimental results of streaming distribution in a hybrid architecture that consist of mixed connections among P2P and Cloud nodes that can interoperate together. We have chosen to represent the P2P nodes as Planet Lab machines over the world and the cloud nodes using a Cloud providers network. First we present an experimental validation of the Cloud infrastructures ability to distribute streaming sessions with respect to some key streaming QoS parameters: jitter, throughput and packet losses. Next we show the results obtained from different test scenarios, when a hybrid distribution network is used. The scenarios measure the improvement of the multimedia QoS parameters, when nodes in the streaming distribution network (located in different continents) are gradually moved into the Cloud provider infrastructure. The overall conclusion is that the QoS of a streaming service can be efficiently improved, unlike in traditional P2P systems and CDN, by deploying a hybrid streaming architecture. This enhancement can be obtained by strategic placing of certain distribution network nodes into the Cloud provider infrastructure, taking advantage of the reduced packet loss and low latency that exists among its datacenters.

ISABEL: A CSCW Application for the Distribution of Events

Introduction Many activities which in the past have required physical presence and direct interaction among participants can be performed in a distributed fashion with the help of advanced information technologies such as, CSCW [1,2] (Computer Supported Cooperative Work), interactive multimedia services and broadband communications. Technologies aiming at supporting the collaboration among individuals or groups are identified under the term groupware technologies. Asynchronous interactions which do not require physical presence of interacting persons have matured during the last years. Very successful examples of asynchronous groupware exist. LOTUS Notes [3] is considered probably the most successful commercial product in this area. The Internet and many of its application can be considered as groupware technologies to some extend. Technology can support today also synchronous interaction where real time contact among individuals is required. We mean by synchronous interaction the exchange of verbal, visual, ... messages or information, like the exchanges of information carried out typicaly in meetings, conversations or other activities where several participants collaborate in physical presence. Remote synchronous interaction is not new, the plain old telephone is a very good example of an old technology supporting a simple but very effective form of synchronous interaction. POTS is today by far the most demanded synchronous service. This service has evolved into N to N audioconference or videoconference facilities. Computers in general and the Internet have also had primitive types of character oriented synchronous interactive services for a long time, like TALK, IRC, ... Today low quality voice and video over the Internet is also common practice with applications like, CU-SeeMe, IVS, VAT, ... Audiovisual broadcasting is also a highly demanded type of remote synchronous interaction which has been done since many years. Although broadcasting has really no interaction because the flow of information is unidirectional, it is nevertheless being addressed in the experiments performed for creating new synchronous services. One of the most popular services on the multicast backbone of the Internet, also known as the MBONE, is the conference broadcasting for which a Session Directory (SD) exists where the list of broadcast conferences is displayed in real time. Sophisticated forms of remote synchronous interaction requiring good quality telepresence demand more bandwidth and more reliable communications to achieve a proper interaction. Therefore for setting up large sacle experiments like the RACE/ACTS Summer Schools [2,5,6,9] a complex collaboration among a large number of organizations has been needed. In addition, the availability of large …

A Web Collaboration Architecture

Computer supported collaborative work (CSCW) has typically been bound within organizations. Groupware applications are designed with organizational structures in mind, in a top-down approach that predicts communication and collaboration interactions between people. With Internet adoption in society, CSCW overflows organizational borders towards Internet supported collaborative work (ISCW), where the organization of work becomes decentralized, centered on individual interests and pretty dynamic. This paper proposes a Web collaboration architecture for the new Web environment. The article reviews common groupware problems and reflects recent organizational changes. It presents Web 2.0 features and technical state-of-the-art. Then, it describes the architecture proposed, to finish with conclusions and future research lines

Isabel: an application for real time collaboration with a flexible floor control

Isabel is a P2P like multipoint group collaboration tool for the Internet, which implements an innovative service concept for synchronous collaborations based on a flexible and programmable floor control. This approach leads to a more natural and effective management of collaboration sessions. The flexible and programmable floor control incorporates the experience gained in many years of service trials with real users in distributed conferences, classrooms or meetings. The main conclusion after all those trials is that services should use more or less the same media components (audio, video or application sharing), but differ in the floor control model used. The flexible floor control is especially well suited for multipoint audience interconnection in distributed classrooms, conferences, meetings, etc. The development of Isabel started in 1993 for the distribution of the RACE Summer Schools on Advanced Broadband Communication (ABC93-6) where the early versions of this service concept were developed and tuned. The effectiveness of the Isabel service concept has been proven and enhanced since then in many other distributed events, such as Global360x, IDC9x, Global IPv6 Summitts, Telecom I+D, etc. The adaptation of Isabel to the broadband Internet (including VPNs, IPv4/IPv6 transition scenarios, mixtures of unicast and multicast) has reached maturity recently

ISABEL - Experiment Distributed Cooperative Work Application over Broadband Networks

Users are looking towards ATM technology as a suitable solution for specific applications in the new field of distributed multimedia. The aim of ISABEL is to take benefit of the new broadband technology in order to provide a good access to new distributed multimedia facilities. The application has been developed to cover two main fields: distance learning activities between two or more real conference rooms and a flexible framework to configure many different computer support cooperative work (CSCW) scenarios. The paper describes the functionality of ISABEL and its use to support real experiments.

Educanext: a framework for sharing live educational resources with isabel

EducaNext is an educational mediator created within the UNIVERSAL IST Project which supports both, the exchange of reusable educational materials based on open standards, as well as the collaboration of educators over the network in the realization of educational activities. The Isabel CSCW application is a group collaboration tool for the Internet supporting audience interconnection over the network, such as distributed classrooms, conferences or meetings. This paper describes the conclusions and feedback obtained from the integration of Isabel into EducaNext, its use for the realization of collaborative educational activities involving distributed classrooms, lectures or workshops, as well as the general conclusions obtained about the integration of synchronous collaboration applications into educational mediators.

Improving LOM-Based Interoperability of Learning Repositories

This paper analyses the use of LOM Application Profiles for learning object repository interoperability. Based on an exemplifying use case the paper presents a case study, which aims at developing a LOM Application Profile to realized Smart Spaces for Learning. Finally, a schema is designed which selects the necessary LOM elements and makes a LOM-conformant extension to represent usage conditions and learning activities. This work is part of the Elena project, which focuses on integrating advanced educational mediators in a network of federated services.