Server Services and Routing Nodes

Now that you understand the contents of the OrgInfo packet, this section explains routing nodes, which are the components that are involved in propagating this information within an Exchange organization. Three types of routing nodes can exist on an Exchange server:

• Master service node

• Subordinate service node

• Client node

Only one type of service node can exist on a server: either the master service node (if the server is the routing group master) or the subordinate service node (if the server is a routing group member). Client nodes consist of various processes, which are consumers of routing information, running on the server. Examples of these processes are SMTP (inetinfo.exe), the Message Transfer Agent (emsmta.exe), the Information Store (store.exe), and the Windows Management Instrumentation (WMI) service (wmiprvse.exe). Two DLLs implement the routing functionality in these components: resvc.dll for the services nodes and reapi.dll for the client nodes.

The following figure illustrates the routing nodes and server services.

Routing services nodes

Client nodes communicate directly with their corresponding server services. This communication never occurs outside of any one individual host, for instance, a client node communicates only with other components on the same server. Member and master service nodes within the same routing group communicate with each other over TCP port 691.