Errors can be detected synchronously or asynchronously.

When an error is detected synchronously, a RAPI error code is returned in the Errnop argument of rapi_session(), or as the function return value of rapi_sender(), rapi_reserve(), rapi_release(), or rapi_dispatch().

When an error is detected asynchronously, it is indicated by a RAPI_PATH_ERROR or RAPI_RESV_ERROR event. An RSVP error code and error value are then contained in the ErrorCode and ErrorValue arguments of the event_upcall() function. In case of an API error (RSVP error code 20), a RAPI error code is contained in the ErrorValue argument.

A description of RSVP error codes and values can be found in RFC 2205. See Related protocol specifications for information about accessing RFCs.