Some existing authorization schemes in VoIP systems are too complex and inconvenient to be used to handily manage the systems, so it needs a new session and media authorization model in IP Video Phone Systems.

• 在IP电话系统中也有一些专有授权方案,但是这些针对IP电话的授权方案存在着授权过程复杂,消息交换繁琐,以及需要过多预信任关系的缺点,因此需要一种新的会话和媒体授权方案。