der Billing Management Customer Network Provisioning Sales Force Automation Gateway Trouble Administration Figure 24. "Spaghetti Architecture" 12.4 Enterprise Application Integration (EAI) As explained earlier, Enterprise Application Integration framework is constructed around a message bus or backplane. Applications plug into this bus using connectors or adapters. These connectors or adapters normalize the application interfaces into a common format. Information is transmitted among applications in the form of messages. A common approach to EAI is based on the publish/subscribe model. Applications can both publish messages onto the bus and subscribe to messages published by other applications. A "message broker" determines how to route the messages among applications. For example, the application Connector to Application A recognizes an event has occurred within the application (e.g. order completion) and wants to notify other interested applications (e.g, billing and The Ultimate Guide to Building and Delivering OSS/BSS network monitoring). In this case the connector publishes a message onto the bus. The message broker routes the message to applications that have subscribed to that type of message. The key differentiators of this approach over point-to-point are that a common bus connects all applications. All applications "talk" to each other via messages. The integration approach is common across all applications, and is thus easier to scale and maintain. EAI FUNCTIONAL COMPONENTS Figure 25 depicts the major functional components of a generic EAI framework. Connector Connector App A App B App A Protocol Session Protocol Session App B Conversion Management Conversion Management Translation Service Messages Messages Mapping Message Transport Publish/ Event Flow Fail-Over Subscribe Balancing Bus or Backplane Figure 25. EAI Functional Components Chapter 6 - Integrating the OSS Platform These major functional components are described in more detail below. Application. The above diagram depicts only two application