ITU-T H.460.24 PDF

This Recommendation defines the capability and procedures for enabling the direct point-to-point media flow between endpoints even if at least one device is behind a network address translator (NAT) or firewall (FW) device. If used in conjunction with [ITU-T H.460.23], this feature can be used to extend the scalability of [ITU-T H.460.19] to allow media, where determined, to flow directly between endpoints and avoid the requirement to proxy media.