The Research And Implementing Of Traversal Through NAT/FW Of H.323 PDUs Based Proxy

The article mainly introduces the research and implementing of traversal through NAT/FW of H.323 PDUs based proxy.First,The article represents the structure of H.323 protocols and NAT.With the popularization of internet, the fast development of network technology and the gradual maturing of wide band access,the scope of applying H.323 is transiting from LAN(local area network) to WAN(wide area network).And then,the problem comes out: how to traverse through NAT/FW? The appearance of the problem dues to two factors: the original design of H.323 for LAN and the inadequate public IP address relatively.The NAT was proposed to solve the inadequate IP address.On the one hand,when traversing through the NAT,the address information contained in H.323 PDUs can't be changed according the different environment of network,on the other hand, because of security limitation,Opening port dynamically is forbidden. The two aspects of fact holds back the traversal of H.323 PDUs successfully.Then, the article campares and analyzes the traversal solutions which are applied by the industry of telecom.Finally,the article puts forward the particular solution.The author adopts the solution of full proxy.and improves it: lightens the burden of proxy server in the public network,supportss three pairs or more H.323 terminals to communicate simultaneously.And the article deals with the implementing of the solution.The author made a great improvement on the basis of Gnu Gatekeeper released by OpenH.323 organization, and added the functions of proxy relay and multilevel registration and so on.At last,The article introduces the prospect and the fields for further study of traversal of H.323 PDUs through NAT/FW.