1引言IP电话是互联网上最早冲击电信市场的应用。迄今, IP电话已经经历了10年的发展,跨过了三个阶段。从最早的通过公用互联网连接、无质量保证的互联网电话(Internet Phone),到后来的在公用互联网或独立IP网上传送的具有一定质量的VoIP,再到最近的利用宽带接人的宽带VoIP(VoBB)。在技术上也从软件电话发展到网关、软交换,目前正在向IMS进军。 1 Introduction IP telephony is the earliest impact on the Internet telecommunications market applications. To date, IP telephony has gone through 10 years of development, spanning three phases. From the earliest Internet Phones with public Internet connections, without quality assurance, to later VoIP with some quality delivered over the public Internet or standalone IP networks, to the recent wideband VoIP (VoBB ). Technically also from the development of software phones to gateways, softswitch, IMS is currently marching into.