For each ArrivalSequenceConsumer, the ArrivalSequenceProvider shall retain a not yet consumed (or delivered) ArrivalSequence message for at least MESSAGE_TTL period of time. MESSAGE_TTL indicates the message 'time to leave', i.e. the amount of time a message yet to be consumed is retained by the provider if such message has not been consumed yet by the service consumer. The ArrivalSequenceProvider shall provide a value for the MESSAGE_TTL parameter. The MESSAGE_TTL represents the time a given ArrivalSequence message must be kept by the ArrivalSequenceProvider if not consumed or delivered to the ArrivalSequenceConsumer before discarding.