基于Vocal的私网穿透的SBC(Session Border Controller)设计

随着技术的成熟，VoIP技术以更加迅猛的势头得到发展和普及，但是在这个过程中电不可避免的碰到一些困难和问题，VoIP应用如何穿越NAT的问题就是其中之一。VOCAL是完全摹于SIP的VoIP开放源代码方案。如何穿越NAT也是用VOCAL系统开发VoIP服务必须解决的问题。研究了NAT技术给VoIP服务带来的问题，并且就当前主流的NAT穿透方案进行探讨，然后在此基础上选择一个无须对现有设备进行任何改动的VOCAL系统穿越NAT方案——SBc。并以VO—CAL系统为对象，研究SBC在VOCAL系统中的设计。

The Design of Session Border Controller for Traversing Network Address Translation on VOCAL

With the accomplishment of its technical maturation,VoIP has been more rapidly developed and spread.However,somedifficulties and problems also arise unavoidably and the problem,howVoIP applications traverse NATor Firewall is one of them.VO-CAL is an open-source code program that provides a SIP-based VOIP communication.Therefore,NAT traversal problem must be re-solved when developing VoIP services with VOCAL.This thesis analyzes the issues brought by NATin VoIP services and discusses themain solutions for traversing NAT.And then a solution over the VOCAL system named SBC is brought forward,which can do withoutchanging any the present device.ASBC is located at the border of VOCAL system.SBCs manipulate SIP messages and transmit mediapackets so as to provide traversal of NAT/Firewalls.The design of SBC on VOCAL has been done in this thesis.