Optimizing Your Topology

Several aspects of your organization's topology, including how your sites and servers are laid out, the amount of traffic your system supports, and the network bandwidth, can have a significant effect on overall system performance. Optimizing the topology of your system includes planning server locations, site boundaries, and replication settings to increase the speed of directory and public folder replication and also the speed of message delivery.

These are some strategies for optimizing system topology:

• Control the amount of traffic your system supports. For example, you can restrict the number of messages users can send or you can limit the size of the messages. Factors that can affect traffic are the type and number of messages, the frequency of public folder replication, the size of replicated public folders, the frequency of directory replication, and the size of the directory changes.
• Make sufficient network bandwidth available to handle the amount of traffic your system has to support. The more traffic you have, the higher the bandwidth connections must be.
• Balance public folder replication traffic with network traffic. If many users need access to a public folder in another site, minimize traffic to the other site by replicating the public folder to the local site. However, if only a few users need access to a public folder in another site, configure the system so that these users connect to the public folder in the other site.
• Arrange your sites in a hub-and-spoke configuration, with one central site and multiple satellite sites. Servers in the hub site can be dedicated to message-switching functions and act as the messaging transfer agent (MTA) backbone of the system.

The bandwidth between servers in different sites is not as critical as the bandwidth between clients and servers. Network connections between clients and servers should have a high bandwidth to ensure the fastest client/server response times possible. Tests performed by the Microsoft Exchange Server Performance Team have shown that 56K per second throughput is the threshold for communication within a site; however, this threshold can vary depending on the traffic in your organization.

If you have a connection that is slow, consider placing it between two sites because communication between sites does not have to be as fast as communication within sites. However, if you don't want to administer two sites, connect clients to a central site over the slow connection; this configuration is most effective when you have only a small number of clients. The two connection options are shown in the following illustration.