SIP (Session Initiation Protocol) is introduced by IETF, it is an application-layer control(signaling) protocol for creating, modifying, and terminating sessions with one or moreparticipants. These sessions include Internet telephone calls, multimedia distribution, andmultimedia conferences.
At the full of opportunities in the domestic and international environment, the traditional telephone industry in the United States will develop with mobile phone industry, the Internet telephone industry, cable television industry and the computer industry together for quite some time to achieve maximum benefits in the integration of the competitive market.
With the rapid development of Multimedia communication technology and Internet technology, Application of Digital speech Coding is more widely in recent years, especially in the area of Visible telephone, IP Internet telephone、 Digital cellular mobile communication、 Integrated server digital network、 Public Switched Telephone Network and packet transfer Voice System, etc.
The 4-port VoIP Terminal Substitute Equipment Series, phonic transmission through IP, is also named Internet Telephone HUB. The series involved in advanced flushbonding system design, RISC CPU and DSP twin platform and echo control &noise eliminating technology are mainly providing the customers equipped with appropriate IP net (such as government agencies, courts, police, and other groups) with high quality long distance telecom service.
These sessions include Internet multimedia conferences, Internet telephone calls and multimedia distribution.
In the 1990s, Internet telephone marks the latest step along this slow path to an all packet infrastructure.
In addition, if you sign up with an Internet telephone provider, you can use the Internet phone just as you would you normal phone line.
We firstly introduce what is Internet telephony and why we should connect the Internet telephony to PSTN in thispaper.Then,we compared several Internet telephone schemes available according to their solutions.After discussing some important characteristics that determine the QoS of the Internet telephone.Finally,we propose an Internet telephony gateway to the PSTN with both its hardware and software solution.