Share via

Routing Updates

  • Article

 

The section discusses the types of updates that the routing group master receives and distributes to its routing group members. Exchange servers and domain controllers may communicate about the following types of information in the context of routing topology and link state updates:

  • Major   When routing topology updates occur, such as connector configuration, which includes adding or deleting a connector, adding or deleting an address space on a connector, or a when a new server is designated as the routing group master.

  • Minor   When information about connector or virtual server availability changes, for example, a connector state changes from up or down.

  • User   When services have been started or stopped on an Exchange server (used in the implementation of the 'Status' node in Exchange System Manager), or when another server has been added to the routing group, or a server loses its connectivity to the routing group master.

Major Updates

A domain controller informs routing group masters of major changes in the routing topology for their particular routing group, according to the standard Lightweight Directory Access Protocol (LDAP) change notification process. When the routing group master starts, it registers with the directory using DSAccess for change notifications that pertain to its routing group.

A routing group master accepts major routing information updates pertaining to its routing group only from the domain controller with which it communicates. When a routing information update is sent to a routing group from another routing group, for example, the receiving routing group master always ignores the information pertaining to its routing group that is within the OrgInfo packet. For minor and user updates that pertain to its routing group, the routing group master accepts changes from its local client nodes or any subordinate services (routing group members) within its routing group.

A domain controller sends notifications to the routing group master in the following situations:

  • A new connector has been added to the routing group, or any attribute changes have been made to an existing connector.

  • When changes have been made to the routing group object itself, for example, the routing group master changes.

After the change notification process is complete, the routing group master communicates the change in topology to all of the servers in the local routing group and any servers that act as a remote bridgehead for one of the connectors in this routing group.

Minor Updates

Minor updates consist of link state changes in the environment such as a connector changing from a state of "up" to "down." This change in link state may be detected by any client node in the environment. In Exchange 2000 Server, when a client node detects a change, it communicates this change to its server services nodes at 5-minute intervals. In general, whenever a link state update is received by a master or subordinate service node, the server is forced to requeue all messages and inform the routing group master of the link state change. For unreliable connections that cause frequent state changes (oscillating connections), the communications cause excessive and often conflicting communications.

In Exchange Server 2003, if no alternate path exists for a link in a leaf-node routing group, the link state is always marked as available. Exchange does not change the link state to unavailable if no alternate path exists. Exchange queues mail for delivery and sends it when the route becomes available again. This change enhances performance because it reduces the propagation of link state information.

As for oscillating connections, Exchange 2003 views the link state queue and if there are multiple conflicting state changes in a given interval for a connector, the connector is considered an oscillating connection and its link state remains as available. It is better to leave an oscillating connector in an available state than to continually change the link state. This approach reduces the amount of link state traffic that is replicated between servers.

User Updates

User updates consist of minimal changes such as when the routing group master has changed, when services have been started or stopped on an Exchange server, when another server has been added to the routing group, or when a member server loses connectivity to the routing group master.