Catálogo de publicaciones - libros

Web Services is an XML-based technology that has attracted significant attention for building distributed Internet services. There have also been significant efforts trying to extend it to become a unifying management technology. An all-encompassing management technology needs to support efficient information retrieval, scalable event management, transaction support for configuration management and also security. Previous technologies, such as CMIP, SNMP and CORBA have addressed these aspects poorly, partially or at a high cost. This paper proposes an approach to address efficient information retrieval in terms of both bulk and selective data transfer. In order to achieve this, services modelling management information need to be organized in a hierarchy through service association. In order to achieve service association, information metadata are defined in secondary endpoints compared to the ones where services are deployed and accessed. We have defined a language for expressing arbitrarily complex information retrieval expressions and implemented a parser at the object level that evaluates these expressions, navigates arbitrary service associations and returns the results. We demonstrate the use and usefulness of the approach in an example usage scenario.

Management performance evaluation means assessment of scalability, complexity, accuracy, throughput, delays and resources consumptions. In this paper, we focus on the evaluation of management frameworks delays through a set of specific metrics. We investigate the statistical properties of these metrics when the number of management nodes increases. We show that management delays measured at the application level are statistically modeled by distributions with heavy tails, especially the Weibull distribution. Given that delays can substantially degrade the capacity of management algorithms to react and resolve problems it is useful to get a finer model to describe them. We suggest the Weibull distribution as a model of delays for the analysis and simulations of such algorithms.

There have been several attempts in the past to secure the Simple Network Management Protocol (SNMP). Version 3 of the SNMP protocol introduced a User-based Security Model (USM) which comes with its own user and key-management infrastructure. However, many operators are reluctant to introduce a new user and key management infrastructure just to secure SNMP. This paper describes how the Secure Shell (SSH) protocol can be used to secure SNMP and it provides a performance analysis of a prototype implementation which compares the performance of SNMP over SSH with other secure and insecure versions of SNMP.

With many organizations now employing multiple data centres around the world to share global traffic load, it is important to understand the effects of geographical distribution on service quality. The Domain Name Service is an important component for global load balancing. Using controllable simulations, we show that wide area sharing can play an important role in optimization of response times when traffic levels exceed that which can be supplied by a local infrastructure. We compute the probability of being able to meet Service Level Objectives as a function of DNS caching policy (Time To Live), so that service providers can account for DNS error margins in Service Level Agreements.

Load sharing in the data centre is an essential strategy for meeting service levels in high volume and high availability services. We investigate the accuracy with which simple, classical queueing models can predict the scaling behaviour of server capacity in an environment of both homogeneous and inhomogeneous hardware, using known traffic patterns as input. We measure the performance of three commonly used load sharing algorithms and show that the simple queueing models underestimate performance needs significantly at high load. Load sharing based on real-time network monitoring performs worst on average. The work has implications for the accuracy of Quality of Service estimates.

Enterprises and service providers are increasingly looking to process-based automation as a means of containing and even reducing the labor costs of systems management. However, it is often hard to quantify and predict the additional complexity introduced by IT service management processes before they actually have been deployed. Our approach consists in looking at this problem from a different, new perspective by regarding complexity as a surrogate for potential labor cost and human-error-induced problems: In order to effectively evaluate the benefits of IT service management processes – and to target the types of processes that contribute most to management complexity and cost – we need a set of metrics for quantifying the complexity and human cost of carrying out IT service management processes. This paper proposes such measures, and demonstrates how they can be applied to a typical service delivery process in order to assess its complexity hotspots as a basis for process re-engineering.

Self-governing systems need a reliable set of semantics and a formal theoretic model in order to facilitate automated reasoning. We present an ontology-based knowledge representation that will use data from information models while preserving the semantics and the taxonomy of existing systems. This will facilitate the decomposition and validation of high level goals by autonomous, self-governing components. Our solution reuses principles and standards from the Semantic Web and the OMG to precisely describe the managed entities and the shared objectives that these entities are trying to achieve by autonomously correlating their behavior. We describe how we created UML2, MOF, OCL and QVT ontologies, and we give a case study using the NGOSS Shared Information and Data model. We also set the requirements for integrating existing information models and domain ontologies into a unique knowledge base.

Web service technology has been proposed to implement management interfaces of managed resources. These web services can usually be combined to perform composite processes. These composite processes can be defined with service ontologies such as OWL-S, which allows their formal description. However, other technologies, including the Web Services Business Process Execution Language (WSBPEL), provide more mature execution engines. This paper presents an approach to define and execute composite network management processes with existing technology. For this, a use case is developed in which a set of web service interfaces are defined for a network probe, and a composite process is specified using OWL-S to monitor the network load. Then, this specification is later translated to WSBPEL and interpreted by a real execution engine.

This paper proposes an open, extensible control plane for a global event service, based on semantically rich messages. This is based on the novel application of control plane separation and semantic-based matching to Content-Based Networks. Here we evaluate the performance issues involved in attempting to perform ontology-based reasoning for content-based routing. This provides us with the motivation to explore peer-clustering techniques to achieve efficient aggregation of semantic queries. The clustering of super-peers using decentralized policy engineering will deliver the incremental deployment of new peer-clustering strategies.

How well can the Internet serve as a network carrying voice calls? To answer that question, we have been running a web site called TestYourVoIP where users can run tests of VoIP Quality from their PC. In this paper we describe how TestYourVoIP operates, the kinds of tests it performs, and the results we have found from those tests. Our findings indicate that while many users will get acceptable call quality, too many will not. We offer some insights as to the reasons for poor quality based on these real world experiences. Lastly, we note that over 2005, voice quality on the Internet has gotten worse.