Research And Development Of NAT Traversal Based On SIP Protocol

As intense competition between mobile operators and fixed operators, how to effectively reducing the maintenance costs of network, it's become the first condition of win the fierce competition. To telecom operators, they could use SIP core network with VoIP to reduce operating and maintenance costs. And they could provide advanced IP-BASE services, in order to maintain more users. To mobile operators, SIP could also be used as a solution. Therefore, both of mobile operators and fixed operators are pay attention to SIP.SIP is an IETF defined IP multimedia communication contro1 protoco1 and the key protocol of the next generation network (NGN).As a result of the inconsistency between the rapid development of SIP-based audio/video communication applications and the shortage of IPv4 addresses,the NAT traversal problem has been raised.The NATs caused the SIP END—to—END application to become extremely difficult. In this paper we analyzed several kinds of method of NAT traversal for SIP and their pitfalls。Proposed a solution for NAT traversal based Oil STUN and TURN methods.Its basic idea is that for SIP signaling.it takes different methodology to traverse the NAT by the NAT type·and for the associated media it traverses the NAT by the connectivity checks to all the media addresses available.This solution can traverse all NATs in the application layer not changing the existing NAT. And avoids the pitfalls of using any of the other methods alone.The production has run for testing with Alcatel-Lucent 5350 IMS Application Server, The results show that the system is good and stable and the requirement of the users has been satisfied. The design is a very good solution to the problem of the NAT traversal. It will play an important role in promoting the development of SIP.