Optimizing Your Topology

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

Some strategies for optimizing your topology's performance are:

• Controlling the amount of traffic your system supports. For example, you can restrict the number of messages users can send or limit the size of messages. Factors that can affect traffic are the type and number of messages, the frequency of public folder replication and the size of replicated public folders, and the frequency of directory replication and the size of the directory changes.
• Making sufficient network bandwidth available to handle the amount of traffic your system needs to support. More traffic requires higher bandwidth connections.
• Balancing public folder replication traffic with network traffic. If many users need to access a public folder in another site, you should replicate the public folder to the local site to minimize traffic to the other site. However, if only a few users need to access a public folder in another site, users should connect to the public folder in the other site.
• Arranging your sites in a hub-and-spoke configuration with one central spoke and multiple satellite sites. Servers in the hub site can be dedicated to message switching functions and act as a messaging transfer agent (MTA) backbone.

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 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 your organization's traffic.

If you have a slow connection, you should consider placing the connection between two sites because communication between sites does not need to be as fast as communication within sites. Alternatively, if you don't want to administer two sites, you can connect clients to a central site over the slow connection. This configuration is most effective for a small number of clients. These two options are shown in the following illustration.