What's being coined a Service Delivery Platform (SDP) brings together two disparate environments—data-oriented Web applications and real-time Session Initiation Protocol (SIP)-based communications applications—into a unified environment for developing, deploying and managing converged applications.

Service Delivery Platforms serve as a service development environment s for Web applications and databases, incorporating real-time elements such as multimedia sessions into Web applications. Service Delivery Platforms can also serve as a combined, integrated environment to create data/non-real-time services and enrich them with real-time services to facilitate features such as voice conferencing and other SIP-based capabilities.

In a Service Oriented Architecture (SOA), you can use an SDP for the development, deployment, and management of everyday data-oriented Web Services and Web-based applications, as well as those applications that incorporate cutting-edge real-time communications capabilities. For example, you can create an application using Web Services that enable a Blackberry phone-based application to launch a network-based conference call based on the recipients of an email to identify the parties to be involved in the conference call. Let's say you receive an email on which Bob, Ted, Carol and Alice are copied. Using an intelligent communications application executing on an SDP, you can easily invoke an on-demand conference call to all the email recipients with a single action, thereby combining data oriented services (email) with real-time voice communications capabilities.

This emerging trend toward a unified execution environment allows you to use your familiar development environment and existing Web application servers and platforms, as well as create interactive multimedia communications using Web Services, without a huge learning curve. The integrated development environment (IDE) can be used not only to create and validate applications, but to deploy them, including its data model and presentation elements, across multiple tiers. You can then manage all of these elements from a common place.

New SIP application servers, like the Avaya SIP Application Server, use the SIP Servlet API, and add an additional layer on top of the SIP Servlet Container that supports Web Services. This enables the SIP Application Server to be readily used in SOA environments. The inclusion of a SOA based development environment on top of the SIP Servlet container promotes a high degree of reuse of Services built within this environment. The software elements that compose the SDP can be replicated, deployed in separate physical hardware platforms or locations.

To better understand this emerging Service Delivery Platform concept, let's take a refresher course in Web Services as well as SIP, as both are key components in merging development of real-time and non-real-time services and applications. Then, we'll take a closer look at an emerging SDP, the Avaya SIP Application Server (SIP A/S).

Web Services 101
Web Services are frequently just Web application programming interfaces (APIs) that can be accessed over a network, typically the Internet, and can be executed on a remote system that hosts the requested services. The role of Web Services in general is to accelerate application development. They are called services because they perform functions people consider a service, such as filling out an online application for an account. Protocols have been defined that describe how one or more services communicate. Using Web Services, clients and servers communicate using XML messages that follow the Simple Object Access Protocol (SOAP) standard.

Web Services mark a shift from application development to application assembly (or mash-ups), which is a cornerstone of Web 2.0. A typical traditional development and deployment environment for applications that employ the use of Web Services probably looks like this: You have your development environment, be it Eclipse for Java applications or Microsoft Visual Studio for .NET applications that you use to develop non-real-time applications. These apps then are deployed on a separate Web server, such as WebSphere Application Server (WAS), Red Hat's JBOSS or Microsoft's Internet Information Server (IIS). These applications often use the data tier for database and information storage elements.

Service Delivery Platforms enable rapid development and deployment of new converged multimedia services. The applications you can create on an SDP converges telecom and IT capabilities to enhance basic business applications with telecommunications. SDPs provide a service control environment, a service creation environment, a service orchestration and execution environment, and low-level communications capabilities for media control, location, and integration, among other capabilities.

One key advantage of SDPs is its use of shared services, which allows you to share and reuse code, following the typical 80/20 rule where 80 percent of your code is reusable. Often the last 20 percent can take the form of scripts, which greatly reduces the development time. Thus SDP-based applications can be quickly created using Web Services using shared services. With this greater set of fundamental shared services, developers can quickly create complex, robust, feature-rich applications by continually re-using these Web Services at different levels of abstraction—from individual Web Services, to previously constructed sets of processing or business logic.

SOAs as a framework rely on Web and software services is a specific implementation of a SOA. As such, services are a fundamental building block to build applications. The SDP approach exposes more fundamental elements as individual Web Services. SDP provides more fine-grained flexibility in building new applications by using these more fundamental elements, as opposed to being restricted by major blocks of functionality. Some of the benefits of Web Services have been to simplify application design by encapsulating more functionality, such as error handling and validations, into a Web service.