VOCAL（Vovida Open Communication Application Library）是一个开源代码通信软件，以ＩＰ网为核心，在Linux或Solaris操作系统上运行。提供VoIP电话服务，支持基于SIP的通信设备。本文介绍了VOCAL的系统架构，SIP基本呼叫流程和VOCAL的系统功能。-VOCAL ( Vovida Open Communication Application Library ) is an open source code software, using IP network as the core, in the Linux or Solaris operating system running on. VoIP to provide telephone service, support of communication equipment based on SIP. This paper introduces the VOCAL system architecture, SIP basic call process and VOCAL system function.