Controlled relay of media streams across network perimeters

A method in a proxy engine for establishing a media session for sending media streams between a private client and a public client, the private client and the proxy engine being within a private address space with a firewall at a network boundary to a public address space, comprising:

• receiving by the proxy engine from the private client an invite request requesting to establish a media session with the public client, the request including a private address identifier of the private client, a public address identifier of the public client, and a private address identifier for a media stream of the private client;
• determining by the proxy engine from the invite request whether the media session is to cross the network boundary between the private address space and the public address space;
• and
• when it is determined that the media is to cross the network boundary,
• commanding by the proxy engine the media relay to reserve a media path through the firewall and return an indication of a reserved public address identifier of the media relay;
• modifying by the proxy engine the invite request to replace the private address identifier for a media stream of the private client with the reserved public address identifier of the media relay;
• sending by the proxy engine to the public client via the firewall the modified invite request;
• receiving by the proxy engine from the public client via the firewall a response to the invite request, the response including a public address identifier for a media stream of the public client;
• modifying by the proxy engine the response to replace the public address identifier for a media stream of the public client with a private address identifier of the media relay;
• sending by the proxy engine the modified response to the private client;
• and
• notifying by the proxy engine the media relay to relay a media stream received from the public client to the private client and to relay a media stream from the private client to the public client
• wherein
• when the private client sends to the media relay a media stream to the private address identifier of the media relay, the media relay relays that media stream to the public address identifier for a media stream of the public client, and
• when the media relay receives from the public client a media stream sent to the reserved public address identifier, the media relay relays the media stream to the private address identifier for a media stream of the private client.