Considering that current end to end communication services are not adapted for supporting efficiently distributed multimedia application, this paper introduces a new family of generic transport protocols directly instantiated from application layer quality of service requirements. This Generic Transport Protocol (GTP) has been successfully tested for video on demand systems and is one of the major building block of the currently under development GCAP European project. GTP allows one to apply in the transport layer powerful adaptation mechanisms to the network behavior while preserving application requirements and alleviating network bandwidth and buffering needs