Abstract: Network video conference system is a collection of audio, video, data exchange as one method, audio and video for traversing firewall technology is one of the key technology of the realization of network video conference system. Audio and video firewall traversal techniques are to solve the port mapping problem between public and private network, in the limited test conditions without additional hardware and auxiliary equipment, efforts is mode to seek a solution and simulation test, finally, this paper proposes the firewall traversal trace method and successfully applies to the network video conference system. In heterogeneous network, it can realize the audio and video NAT firewall traversing, hold the vido conference with desktop level and large screen in the condition of lacking the bandwith resource, and achieves the effect of HD. It is successfully applies to a certain group video conferencing project, the operation effect is good.

Key words: video conference, NAT traversing, trace method