Method, apparatus, and storage medium

A method includes: receiving a reservation, made by a user from a user terminal, regarding a bandwidth of a line; first determining whether or not a total bandwidth of a bandwidth demanded by the reservation in a time slot related to the received reservation and a guaranteed bandwidth to one or more reserved users exceeds a permissible upper limit value of the line; when the total bandwidth exceeds the permissible upper limit value, calculating a reducible bandwidth based on a bandwidth shortage produced by subtracting the permissible upper limit value from the total bandwidth and statistical information of a use bandwidth consumed by the one or more reserved users; second determining a reduction bandwidth reduced from the guaranteed bandwidth based on the calculated reducible bandwidth; and assigning, by a processor, the determined reduction bandwidth to the bandwidth demanded by the reservation.