### Call Routing

Once the server and client have taken all the necessary steps to set up server and client side relationships, the call mechanism can use them to construct a complete binding and call routing when the call is made. When the client makes a call with a binding that lacks an endpoint (typically the case for bindings imported from the name service), the endpoint is acquired from the endpoint mapper on the target host. The endpoint mapper finds a suitable endpoint by searching the local endpoint map for a binding that provides the requested interface UUID, and if requested, object UUID.

The endpoint map interface and protocol information must match in order for an endpoint to be found, but an object UUID match may not be required. A server can provide a default UUID match by registering the nil UUID. Calls with a nil or unmatched object UUID will get the default endpoint.

Once an endpoint is selected, a call can be routed to one of the endpoints being used by a compatible server instance. The server can unambiguously select the correct interface and operation by using the interface identifier and operation number contained in the call. Recall, however, that the RPC mechanism makes it possible for a server to implement multiple managers for an interface. Hence it may be necessary to select the correct manager. Manager selection is based on the object UUID contained in the call. The selection mechanism depends on two of the relationships established by the server: the object UUID/type UUID mapping and the interface ID/type UUID/manager UUID mapping.

For routing, the server provides a default path by registering a default manager for the nil type UUID. Calls containing the nil object UUID, or any UUID for which the server has not set another type UUID, will be directed to the default manager.

Once the manager is selected, the call is dispatched via the selected manager EPV using the operation number contained in the call.

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