Message oriented middleware

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Message-Oriented Middleware
Edward Curry National University of Ireland, Galway, Ireland

1.1 Introduction
As software systems continue to be distributed deployments over ever-increasing scales, transcending geographical, organizational, and traditional commercial boundaries, the demands placed upon their communication infrastructures will increase exponentially. Modern systems operate in complex environments with multiple programming languages, hardware platforms, operating systems and the requirement for dynamic flexible deployments with 24/7 reliability, high throughput performance and security while maintaining a high Quality-of-Service (QoS). In these environments, the traditional direct Remote Procedure Call (RPC) mechanisms quickly fail to meet the challenges present. In order to cope with the demands of such systems, an alternative to the RPC distribution mechanism has emerged. This mechanism called Message-Oriented Middleware or MOM provides a clean method of communication between disparate software entities. MOM is one of the cornerstone foundations that distributed enterprise systems are built upon. MOM can be defined as any middleware infrastructure that provides messaging capabilities. A client of a MOM system can send messages to, and receive messages from, other clients of the messaging system. Each client connects to one or more servers that act as an intermediary in the sending and receiving of messages. MOM uses a model with a peer-to-peer relationship between individual clients; in this model, each peer can send and receive messages to and from other client peers. MOM platforms allow flexible cohesive systems to be created; a cohesive system is one that allows changes in one part of a system to occur without the need for changes in other parts of the system. 1.1.1 Interaction Models Two interaction models dominate distributed computing environments, synchronous and asynchronous communication. This section introduces both interaction models; a