在传统电话系统中，一次通话从建立系统连接到拆除连接都需要一定的信令来配合完成。同样，在IP电话中，如何寻找被叫方、如何建立应答、如何按照彼此的数据处理能力发送数据，也需要相应的信令系统，一般称为协议。目前在国际上，比较有景响的IP电话方面的协议包括ITU-T提出的H.323协议和IETE提出的SIP协议，本节主要介绍目前用得最广泛H.323协议。-In the traditional telephone system, a call from the establishment of systems to connect to dismantle connection with the completion of signaling. Likewise, IP telephony, how to find the called party, how to create a response, how to send data to each other s data processing capabilities, signaling systems, commonly known as the Agreement. Internationally, more King loud IP telephony protocols, including ITU-T H.323 and SIP protocol IETE, this section introduces the most widely used H.323 protocol.