Depending upon the parameters, each call might or might not result in new admission control calls, which could fail asynchronously.

If there is a synchronous error in this call, rapi_reserve() returns a RAPI error code; otherwise, it returns 0.

Applications measure success in the form of errors returned when making QoS requests. No final acknowledgment will occur.

An admission control failure (for example, refusal of the QoS request) is reported asynchronously by an upcall of type RAPI_RESV_ERROR. A RSVP_Err_NO_PATH error code indicates that RSVP state from one or more of the senders specified in FilterSpec_list has not (yet) propagated all the way to the receiver; it might also indicate that one or more of the specified senders has closed its API session and that its RSVP state has been deleted from the routers.