Research and Implementation of NAT Traversal for SIP in Softswitch

SIP (Session Initiation Protocol) plays a very important role in softswitch which is the core technology of the NGN (Next Generation Network). NAT (Network Address Translator) traversal for SIP has been the exchange of operational impact on the rapid popularization of softswitch service. In this paper, we introduce SBC (Session Border Controller) and ALG (Application Level Gateway), which are recognized as very suitable solutions for the current softswitch network environment, to solve this problem. Further more, we propose an implementation of ALG. Our proposed solution has been adopted in our high-end firewall and put into the market.