Quality of ServicesCore Issues

This short introductory chapter discusses the core issues associated with building quality Java EE .NET interoperable applications, and identifies the relevant standards and technologies that address these issues.

Quality of Services is extremely important in managing successful business operations. Availability, scalability, and security are service-level characteristics that determine Quality of Service requirements. These characteristics are highly desirable for business services such as video on-demand or music downloading, which require resources and capacity to be dynamically allocated based on user request. With Quality of Services, businesses can provide differential business services and capacity on-demand. This is also one of the key objectives in Utility Computing.

The term "Quality of Services" (QoS) has been widely used in the telecommunications and data center communities to refer to treating different network packets or infrastructure services differentlyand not with the same best-effort service. Applying the QoS concept to software engineering, QoS usually refers to the systemic quality of reliability, availability, scalability, manageability and security for developing and deploying business applications and services. It is important to design and deploy Java EE and .NET business applications with this systemic quality, particularly Java EE .NET interoperable solutions. Managing the QoS for network services and infrastructure is very different from managing the QoS for Java EE .NET interoperable software applications.

To illustrate the difference, architects and developers might find some common issues in managing service-level objectives for their Java EE .NET interoperable applications:

• Individual Java EE or .NET applications seem to be reliable and scalable. Once they exchange service requests and business data, the performance degrades. It is difficult to easily tell whether the Java EE or .NET applications have any QoS issues.

• You cannot manage QoS of the other parties outside your domain if the QoS problem lies at the other end.

• The QoS design strategy that works for the Java platform does not necessarily apply in .NET, and vice versa.

• There is no standard mechanism to measure and manage QoS.

In a telecommunications context, managing QoS is specific to the network layer and does not need to take into consideration individual business applications (components or factors) within the application layer. Besides, managing QoS does not need to regard the dependencies (for example, a Java EE application function aggregates business data from another Java EE application and a .NET business component) or the integration points (such as the interoperability bridge) inside the application layer. Handling different business applications or components on heterogeneous platforms (particularly when they have dependencies) is rather complex.

This short introductory chapter defines four key attributes of achieving QoS in Java EE .NET interoperable applicationsreliability, availability, scalability and performance (RAS) and manageability. These Quality of Services issues are common to both Java EE and .NET applications, as well as to Java EE .NET interoperable solutions. The chapter also introduces some metrics and technology that can help in implementing the Quality of Services attributes. Chapter 14, "Java EE .NET Reliability, Availability, and Scalability," discusses some design strategies for addressing the RAS requirements. Chapter 13, "Java EE .NET Security Interoperability" discusses the details of security requirements and design strategies, and Chapter 15, "Managing Java EE .NET Interoperability Applications," discusses the manageability aspect in detail.