The scope of ED-137 is to define the rules for VoIP implementations to support ATM communications and their interoperability. ED-137 is composed of multiple Volumes, each of which is dedicated to a specific application. ED-137 Volume 4 proposes a profile standard for the use of RTSP to establish, terminate and control recording sessions of the Ground Telephone Service and the Radio Service in an Air Traffic Services Ground Voice Network (AGVN).