Abstract: A process for establishing a session between a first node and a second node of a communications network, the process including receiving a first request addressed from the first node and addressed to the second node; sending, in response to receipt of the first request, a response addressed to the first node to cause the first node to send a second request addressed to the second node, the response including first validation data; receiving the second request sent by the first node, the second request including second validation data; and determining, on the basis of the second validation data, whether to establish the session.