Research And Implementation Of NAT Traversing Based On SBC

With the rapid development of network applications, VoIP technology has been widely applied. However, Network Address Translation (NAT) and Firewall technology brought the end-to-end VoIP communications problem which raised in order to solve the shortage of IP addresses and network security issues. How to effectively solve the signaling, media streaming NAT/firewall traversing problem? This will be the key technology of promoting the wider applocation of VoIP business. This paper deeply researches in NAT/Firewall traversal method and then introduces a concrete realization of solutions.This article is based on the above background, which passed through NAT/FW in view of the SIP signaling to do the following work:(1) Bring out of the thinking of NAT/FW traversing by SBC-CBM. In this paper, althought the current study of signaling travesing the NAT/ FW primarily used in several ways, the study found that they have the same problem which is the need for existing software, or equipment upgradation to support the functionality required. For this problem, on the base of in-depth study of the working mechanism of NAT and the network architecture, we bring out one new method which called SBC-CBM to solve the NAT/FW travesing problems. SBC generally placed in the network side of the core switching equipment. SBC after all the signaling and media flow through the coordination and revision of SBC may be in the system right-side and user side transmission. User side NAT / Firewall to accept this revised signaling and media streams and send them to the user within the network side.(2) SBC-CBM implementation. Because the majority of NAT is a non-symmetric NAT, therefore the use of TURN as a method traversing the firewall/ NAT is only under special circumstances. And in most cases we the use of the Pinhole and the STUN technology. Therefore, this paper uses two types of SBC-CBM approach to design traversing technology: Pinhole way belong with STUN. According to SBC's thinking of NAT travesing, this paper discussed in detail with SBC travesing solutions which based on Pinhole and STUN/TURN methods; expatiate its principle technology combined with a comprehensive description of the signaling flow; design and realization of SBC-CBM client and server which combined with control server, STUN/TURN server, Pinhole Address mapping and SIP messages and the media message transfering; and then realize the prototype system which can travesing the NAT.(3) Finally we test the system. The test result had indicated that these two method union had the good traversing effect; which had reflected fully SBC NAT traversing's superior; which could satisfy the signaling and the multimedia traversing requests; which is covert to the client side that has guaranteed the data transfer confidentiality. The practical application indicated that method of this paper is strong operational. It can utilize in NAT traversing problems and has the widespread application value.