Francis Tam

Service Availability: Principles and Practice

Our society increasingly depends on computer-based systems; the number of applications deployed has increased dramatically in recent years and this trend is accelerating. Many of these applications are expected to provide their services continuously. The Service Availability Forum has recognized this need and developed a set of specifications to help software designers and developers to focus on the value added function of applications, leaving the availability management functions for the middleware. A practical and informative reference for the Service Availability Forum specifications, this book gives a cohesive explanation of the founding principles, motivation behind the design of the specifications, and the solutions, usage scenarios and limitations that a final system may have. Avoiding complex mathematical explanations, the book takes a pragmatic approach by discussing issues that are as close as possible to the daily software design/development by practitioners, and yet at a level that still takes in the overall picture. As a result, practitioners will be able to use the specifications as intended.

Comparing Robustness of AIS-Based Middleware Implementations

To enable the interoperability of high availability (HA) middleware systems the Service Availability Forum has released a set of open specifications. The benefit of having open specifications is the choice of implementations available from different vendors. When one chooses a product, one of the selection criteria (besides performance) is the robustness of the implementation, as the crashing or hanging of such a HA middleware causes the failure of the whole system. The challenge is to develop the appropriate technology for measuring and comparing robustness of HA middleware implementations. Based on our earlier results, we present a set of automatic testing tools and a benchmark suite constructed using these tools. We demonstrate the robustness testing approach by comparing the results of benchmarking carried out on three HA middleware implementations.

On the development of an open standard for highly available telecommunication infrastructure systems

With the advent of end customers in the telecommunications market wanting more new services at an increasing rate, and the dependability level of such services as high as the traditional ones, network infrastructure equipment manufacturers and application developers are faced with the challenge of delivering such services in ever-shorter cycles. By standardising programming interfaces for developing and deploying highly available applications, the Service Availability Forum attempts to tackle the issue of reducing development time and costs for highly available services. In this paper, we discuss the mission and activities of the Service Availability Forum. We also outline our vision for an application interface that has the potential as the much needed solution.

The emerging SAF software management framework

This paper describes the emerging Software Management Framework of the Service Availability Forum (SAF). It defines the steps required for a software upgrade in a high availability system. Although the orchestration of the upgrade is an important task of the Framework, it is not the only one. It is essential that the software to be upgraded is made available to a target node and that there is some bookkeeping about which versions of software are available, on which nodes they are installed and which entities are configured to deploy them. This necessitates the definition of an information model for software management. The Software Management Framework takes on the software upgrade issue from the perspective of SAF: SAF has defined the Availability Management Framework (AMF) and therefore the Software Management Framework assumes only AMF entities as highly available and uses AMF to handle the high availability issues of their upgrade. At the same time it is also suitable for controlling the upgrade of software which does not make use of AMF, however with no availability guarantees for them.

On engineering standards based carrier grade platforms

The remarkable pace of advancement in communications technologies and the exponential growth of the market have pressured network equipment providers into producing more features in products in a much faster rate at lower costs. The strategy of buying constituent components instead of building ones own has shown promises in achieving these goals. In this paper, we articulate the needs for following standards, and discuss the impact and the required changes for engineering a standards based carrier grade platform. The focus is on the introduction of an availability management middleware, in the form of an off-the-shelf component, and its impact on the product life cycle. By applying and adapting a selection of research results from the dependability community, we show that the telecommunications industry can benefit and achieve its target of reducing development costs.

First experience of conformance testing an application interface specification implementation

This paper describes our first attempt of conformance testing an implementation of the Service Availability Forum Application Interface Specification on a carrier-grade service platform for mobile communications applications. The requirements and guidelines of the IEEE Standards for measuring conformance to POSIX® have been adapted for the Application Interface Specification. The Test Method Specification structure is explained and assertions of the component registration function is shown as an example. A description of the Implementation Under Test is included, together with an explanation of the Test Method Implementation. Our experience suggests that this approach is indeed feasible and repeatable. The thorough level of testing appears to have the right balance of confidence and manageability for test cases. The intermediate test results also unexpectedly provide the developers with some useful insight into future implementations.