In one aspect, communication link established from a communication unit to a communications system. A request message is transmitted from a communication unit to the work connection computer and checked with the aid of a user profile of the communication unit, to verify whether the communication unit has log-on authorization. If the verification of the request message is positive, the request message is forwarded from the network connection computer to the connection handling computer in the form of a modified request message. The modified request message is analyzed by the connection handling computer with the aid of an authentication profile of the network connection computer. Once the modified request message has been positively analyzed and the communication unit has been successfully registered, a response message is transmitted from the connection handling computer to the communication unit.