The invention concerns a telecommunication system (10) and a computer-implemented method for transferring media data from a first RTC client (30) over a QoS-sensitive network (N1) using the real-time protocol (RTP) to a second RTC client (40), wherein the quality of service is based on different traffic classes and the media data contain a first media type with a first traffic class (QoS1) and a second media type with a second traffic class (QoS2), comprising the following steps: media data, which contain a first media type with a first traffic class (QoS1) and a second media type with a second traffic class (QoS2), are bundled by the first RTC client (30) into second packets (P2), in each second packet (P2), the traffic class (QoS1, QoS2) for each media type is marked in layer 4 and/or layer 5 of the real-time protocol (RTP), the second packets (P2) are transmitted in the direction of the second RTC client (40), either before or during the transfer to the network (N1), the second packets (P2) are unbundled using the markings in layer 4 and/or layer 5 of the real-time protocol (RTP) and then bundled into first packets (P1), each of which has only one of the traffic classes (QoS1, QoS2), and the first packets (P1) are transmitted over the network (N1) to the second RTC client (40).