Method for authorizing the establishment of a peer-to-peer flow between two user terminals through a mobile telecommunications network, said method comprising the following steps implemented in a platform of the mobile telecommunications network: - receiving, from a server of a peer-to-peer service provider, a request to establish a peer-to-peer flow between a first user terminal (10.1) and a second user terminal (10.2), the establishment request comprising a flow identifier, the flow identifier comprising at least an identifier of the first user terminal and an identifier of the second user terminal; - deciding whether or not to authorize the establishment of the peer-to-peer flow between the first user terminal and the second user terminal; - transmitting a message authorizing or denying the flow to a network gateway responsible for controlling the flows transiting on the mobile telecommunications network, the authorization or denial message comprising the flow identifier, the method furthermore comprising the following steps, implemented in the network gateway responsible for controlling the flows transiting on the mobile telecommunications network when a packet of a flow between the first user terminal (10.1) and the second user terminal (10.2) is received: - if an authorization message comprising the identifier of said flow has been received by the network gateway, authorizing said data flow to transit in peer-to-peer mode between the first user terminal (10.1) and the second user terminal (10.2) via the mobile telecommunications network; - if a denial message comprising the identifier of said flow has been received by the network gateway or in the absence of reception of a flow authorization message comprising the identifier of said flow by the network gateway, forcing the data flow between the first user terminal and the second user terminal to transit via a media relay server. - receiving, from a server of a peer-to-peer service provider, a request to establish a peer-to-peer flow between a first user terminal (10.1) and a second user terminal (10.2), the establishment request comprising a flow identifier, the flow identifier comprising at least an identifier of the first user terminal and an identifier of the second user terminal; - deciding whether or not to authorize the establishment of the peer-to-peer flow between the first user terminal and the second user terminal; - transmitting a message authorizing or denying the flow to a network gateway responsible for controlling the flows transiting on the mobile telecommunications network, the authorization or denial message comprising the flow identifier, - if an authorization message comprising the identifier of said flow has been received by the network gateway, authorizing said data flow to transit in peer-to-peer mode between the first user terminal (10.1) and the second user terminal (10.2) via the mobile telecommunications network; - if a denial message comprising the identifier of said flow has been received by the network gateway or in the absence of reception of a flow authorization message comprising the identifier of said flow by the network gateway, forcing the data flow between the first user terminal and the second user terminal to transit via a media relay server.