19. STUN Extensions

19.1. New Attributes

This specification defines four new attributes, PRIORITY, USE-CANDIDATE, ICE-CONTROLLED, and ICE-CONTROLLING.

The PRIORITY attribute indicates the priority that is to be associated with a peer reflexive candidate, should one be discovered by this check. It is a 32-bit unsigned integer, and has an attribute value of 0x0024.

The USE-CANDIDATE attribute indicates that the candidate pair resulting from this check should be used for transmission of media. The attribute has no content (the Length field of the attribute is zero); it serves as a flag. It has an attribute value of 0x0025.

The ICE-CONTROLLED attribute is present in a Binding request and indicates that the client believes it is currently in the controlled role. The content of the attribute is a 64-bit unsigned integer in network byte order, which contains a random number used for tie-breaking of role conflicts.

The ICE-CONTROLLING attribute is present in a Binding request and indicates that the client believes it is currently in the controlling role. The content of the attribute is a 64-bit unsigned integer in network byte order, which contains a random number used for tie-breaking of role conflicts.

19.2. New Error Response Codes

This specification defines a single error response code:

487 (Role Conflict): The Binding request contained either the ICE-CONTROLLING or ICE-CONTROLLED attribute, indicating a role that conflicted with the server. The server ran a tie-breaker based on the tie-breaker value in the request and determined that the client needs to switch roles.