Routing Tuning


Topic Last Modified: 2005-05-10

This topic contains information about message routing on your servers.

Exchange 2003 includes functionality to automatically detect changes in the state of a link. This information can be used to inform other servers running Exchange 2003 that an alternative route should be used instead of the lowest-cost primary route. Link state information is broken down into major and minor changes. A major change occurs when the administrator changes the routing topology, such as the addition of a new connector or a cost change. Minor changes occur when the system automatically detects the failure or restoration of a link.

This feature works well in small to medium sized organizations. However, in large multisite environments, mass network fluctuation can cause link update floods for the minor version. To be truly effective, link state data must be broadcast to all the servers in the organization. Additionally, when state changes, the whole link state table is rebroadcast, which can cause significant data to be transmitted over the network. In these scenarios, it may be useful to suppress minor link state changes. You can do this by setting the SuppressStateChanges registry value to 1. For detailed instructions, see How to Set the SuppressStateChanges Registry Value.

In hub-and-spoke environments in which there is no alternative path between the spoke bridgehead and the hub, Exchange 2003 servers automatically suppresses link state changes for that connector. In this scenario, you do not have to set the SuppressStateChanges registry value to 1.

If Exchange Server 2003 tries to route a message to a heavily loaded external SMTP system such as a virus firewall, it can receive a Server Busy error. In these situations, the Exchange transport goes into a state known as 'glitch retry'. In this state, Exchange Server 2003 waits 60 seconds before attempting to resend the message, and it repeats this process three times before resorting to other actions. If external SMTP servers are consistently busy, reduce the glitch retry wait time to prevent mass message queuing.

For detailed instructions, see How to Configure Glitch Retry Interval in Exchange Server 2003.

After you create a routing group in Exchange System Manager, information about that group, contained servers, and any connectors associated with the group is broadcast through link state updates to all the other Exchange 2000 and Exchange 2003 servers in the organization. If the routing group is removed, the object becomes orphaned in the link state table; however, the data continues to be broadcast as part of the link state. Removing the group does not cause routing problems, but the link state table will be larger than it should be. The only way to permanently remove all orphaned routing groups from the link state table is to shut down all Exchange 2000 Server and Exchange Server 2003 computers in the organization at the same time. Therefore, you should keep the creation and deletion of routing groups in a production Exchange environment to a minimum.