Media Connectivity Objects
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Media connectivity refers to the establishment and maintenance of audio/video sessions between endpoints behind firewalls. Firewall traversal requires network address translation (NAT) between internal and external transport addresses (IP address and port).
Unified Communications Client API supports the network address translation using the Interactive Connectivity Establishment (ICE) methodology. A supported media relay server using the ICE methodology supports any combination of the following protocols:
TURN: Traversal Using Relay NAT.
HTTP Proxy: This is also known as HTTP tunneling.
The application that implements Unified Communications Client API must be able to provide configuration information for three aspects of media connectivity:
The location and protocol types supported by the organization media relay server. The location is comprised of the address of the media relay server and the server port configured for media. The transport mode of the server and the protocol type used by the server must also be configured.
The local computer port range to be made available to the media stack for audio/video. Setting a range restricts the number and location of ports the media stack can use for audio/video. When IP security is enabled for a local computer, it is best to set this port range to match the range of ports set aside by IP security as non-secure ports.
Credentials. Required if the media relay server has implemented the Shared Secret protocol.
If the users of your application is participating in audio/video conference sessions with users outside of a firewall, you need to be sure your organization has installed a media relay server in your network and your application is properly configured to use it. Communication between users within a firewall does not require the media relay server but can benefit from restricting the local port range.
To enable firewall traversal, a Unified Communications Client API application simply adds TURN or HTTP proxy servers, also known as the connectivity servers, that are configured to work with the underlying SIP server (for example, Microsoft Office Communications Server.) The application can do so using the IUccMediaEndpointSettings interface. The application can disable ICE by setting the DisableMediaConnectivity flag. A connectivity server is encapsulated by the IUccMediaConnectivityServer interface.
The following diagram illustrates the object model for media connectivity in Unified Communications Client API.