Methods, apparatuses, and systems for improving utilization of a communications system (e.g., a satellite communications system) are provided, using delayed reliability techniques as part of a multicast transport protocol. Embodiments may operate in a client-server context, in which the server-side of the communication link multicasts data to requesting users and to users where the data is being speculatively prepositioned. Requesting users may implement reliability checks to verify receipt of complete data in response to the request while user systems where data is being speculatively prepositioned may receive multicast reliability information in response to reliability requests from other users, but may not request replacement of missing or corrupted data themselves until a request is made for the data by that system.