Sun Java Communications Suite 5 Deployment Planning Guide

Distributed Topology

In a distributed topology, most or all system components and messaging processes are distributed across multiple sites, usually at each remote site. Figure 12–2 shows a distributed topology.

Figure 12–2 Distributed Topology

This diagram shows a distributed topology with Messaging
Server hosts at the Tokyo, London, and New York sites.

You should consider a distributed topology for your site when:

There are advantages to implementing a distributed topology. Users at regional sites have faster access to their messages because they do not have to retrieve messages over the WAN. Furthermore, messages sent within a regional location will incur less messaging traffic than in a central topology. However, satellite offices still rely on the WAN. Therefore, if lots of message traffic is generated in a satellite office, the WAN might need to be upgraded.

The disadvantages of implementing a distributed topology are that typically you will have higher hardware costs and higher support costs as you maintain more hardware at more locations. Support costs are also higher because of the complexity of the distributed topology. For example, failover in a distributed topology is more difficult to implement than in a central topology. In addition, it is much slower to initially deploy Messaging Server because there are multiple servers spread across multiple sites.

Because Messaging Server accesses the LDAP directory, the LDAP server is a critical link in the mail delivery process. If you don’t use remote LDAP replicas, and the central LDAP is down, the messaging service will not be usable.