Sun Java System Communications Services uses a two-tiered messaging architecture that provides the optimum design for scalability and reliability. Instead of having a single host run all the components of a messaging system, a two-tiered architecture separates the components onto different machines. These separate components perform specific specialized functions. As the load for a particular functional component increases—for example, more Message Storage is required, or more outbound relaying is needed—you can add more servers to handle the larger loads.
The two-tiered architecture consists of an access layer and a data layer. The access layer is the portion of the architecture that handles delivery, message access, user login, and authentication. The data layer is the portion of the architecture that holds all the data. This includes the LDAP master servers and Messaging Server machines that are configured to store user messages.
To promote understanding of the Sun Java System Communications Services architecture, Sun created the Sun Enterprise Messaging Reference Architecture (SEMRA), which simulates a corporate Microsoft Exchange site consisting of 5,000 users. This reference architecture proved the concept that migration from Microsoft Exchange to a new Java Enterprise System target deployment works from a functional point of view.
Figure 1 illustrates the SEMRA logical architecture.
In this figure, Tiers 0 through 2 represent the logical architecture for the SEMRA. The User Tier represents communications services users who utilize Microsoft Outlook or web clients.
In this architecture:
Tier 0 contains the load balancer (software or switch).
Tier 1 acts as the front end that provides access to the messaging applications.
Tier 2 forms the layer where the messaging data is handled by the applications.
You can obtain more information about the Sun Enterprise Messaging Reference Architecture here: