A system for communication between a first computer terminal (1) in a private IP network (7) and a second computer terminal (5) in a public IP network includes a network boundary equipment (3). The communications system further includes a mediation system (2) in the private IP network that is associated with the first terminal (1) and is adapted to make an IP interface available to the second terminal (5), and a control server (4) in the public IP network able to control the mediation system 2 via a communications tunnel (6) through the network boundary equipment (3).