The Research Of SIP Security Under NAT And Firewall Deployment

In recent years the Voice over IP and the Multimedia over IP industries have been gradually moving from an experimental stage to real deployment. Multimedia over IP communications runs on the IP networks as other IP applications. Some VoIP services offer features and services that are not available with a traditional phone, or are available but only for an additional fee. With many advantages, VoIP technology is quickly developing and deploying.Looking at IP networks and VoIP, in particular, Session Initiation Protocol (SIP) is a text-based protocol, like HTTP or SMTP, used in multimedia (voice, video, instant messaging) applications to initiate, modify or terminate an interactive user session.However, almost all these IP networks deploy Firewalls and/or NAT devices, for the lack of IPv4 addresses. Unfortunately, the inherent characteristics of SIP protocol are in conflict with most current mechanisms employed by NAT/Firewall, resulting in complex deployment of Multimedia over IP communications. As a result of this trend there are a number of organizations and vendors have presented proposals and solutions to overcome the problem. There is no single solution. The complexity of the problem together with the diversity of existing topologies means that different solutions are needed for different cases. But in all this cases, the security consideration is not adequate. So SIP protocol under NAT/firewall will expose plenty of security vulnerabilities and face many security threats.This paper is aimed to research on the SIP security under NAT/firewall deployments. Firstly, studying the security vulnerabilities, threats and attacking methods. Secondly, analyze the security mechanisms weakness. And finally, improve the security methods to get used to the NAT/firewall deployment.