scope:

This Recommendation enables ITU-T H.323 signalling to traverse NAT/FW installations. When used in conjunction with [ITU-T H.460.19], this allows ITU-T H.323 endpoints to communicate across NAT/FWs which would otherwise be an obstacle to multimedia communications.

The ITU-T H.460.18 architecture consists of a network which is divided into an internal and an external network by a NAT/FW. Typically, the internal network will be a private network, and may be managed by an organization or an individual. The external network will typically be a public network such as the Internet, but may alternatively be another private network.

The ITU-T H.323 internal endpoint and the ITU-T H.460.18 external traversal server (TS) work together to enable bidirectional communication across the NAT/FW and discover the transport addresses that have been modified by the NAT/FW.