SIPTrunk--Network Address Translation Traversal For The Session Initial Protocol

With the rapid development of Internet technology in today’s society, and continuous integration of telecommunications networks, VOIP technology is becoming increasingly important on the Internet, while the demand on the transmission of voice and video data in the network continuously increases. The rapid development of the Internet has accelerated the shortage of IPv4addresses, so the NAT(Network Address Translation) technology comes. NAT technology solves the problem of insufficient Internet IPv4address, but at the same time NAT brings new challenges to VOIP technology.Because we have new multimedia protocols (e.g., SIP is a application layer protocol), the routing of multimedia resources will be divided into the network layer routing and application layer session routing two parts. Usually within the network are deployed NAT devices, common NAT device can only be converted to the IP address of the network layer, the application layer protocol is not perceived, and therefore lead to inconsistent application layer and network layer address information, resulting in the communication can’t be established.How to solve this problem is becoming a key part of that the VOIP can be successfully applied to the Internet. This paper studies how to make voice and video data transmission, how to establish communications through the NAT network, and how to design and implement a viable SIPTrunk application and test it, and finally summarize the results.