The present invention relates to a method of transmitting data at a time-variable data rate, to a connection control module for a network facility (SW1, SW2) therefor, and to a communications module for a user terminal (T1-T5) therefor. In the method, a user terminal (T1-T5) sends to a facility (SW1, SW2) of a network (NET) a request for a connection to a communication partner (T1-T5; CS1, CS2) with a guaranteed data rate (DVT1, DVT2, DVG1, DVG2). The network (NET) establishes the connection and makes the guaranteed data rate available therefor. The user terminal (T1-T5) performs a first data transfer on the connection to the communication partner. Then the connection is released. During the existence of the connection, the performance of the following steps is proposed: determining a portion (FVT1, FVT2, FVG1, FVG2) of the guaranteed data rate not currently used by the user terminal; releasing the unused portion for at least a second data transfer; and, if necessary, again making available the entire guaranteed data rate, including the previously released portion, to the user terminal.