There is described a transmission of user data from a source communications device provided with a first encoder for encoding users data to a target communications device provided with a first decoder for decoding said user data via a communication network which is provided with several converting devices comprising additional encoders and additional decoders for carrying out a verification of the converting devices. Via the verification it is determined, whether the first encoder is compatible with the decoder of a given converting device and, whether the first decoder is compatible with the encoder of said converting device. One of the converting devices for which the compatibility is ascertained by the verification is selected for transmitting user data. During transmission of the user data, said user data encoded with the aid of the first encoder is decoded with the aid of the compatible decoder of the converting device and the user data decodable with the aid of the first decoder is encoded with the aid of the compatible encoder of the selected converting device.