This study is focus on SIP of VoIP, and simulated and analysised by NS2. In addition, because of the security issues are the main factor to affect its popularization, and the DDOS attack has become one of the most serious issues in the VoIP network security. Therefore this research carries on the simulation analysis to various types attack by NS2, and further discusses under the DDoS attack between each kind of Queue regarding the attack comparison of bearing capacity.
