What does VoIP mean?

Voice over Internet Protocol (VoIP) based on IP is a voice calling technology, which realizes voice calling and multimedia conference through Internet Protocol (IP), that is, communication through the Internet.

Other informal names are IP phone, Internet phone, broadband phone and broadband phone service.

VoIP can be used in many Internet access devices, including VoIP phones, smart phones and personal computers, to make calls and send short messages through cellular networks and Wi-Fi.

The basic principle of VoIP is to compress voice data by voice compression algorithm, then package these voice data according to TCP/IP standard, send data packets to the receiving place through IP network, then string these voice data packets together, decompress them and restore them to the original voice signal, so as to achieve the purpose of transmitting voice through the Internet. ?

The core and key equipment of IP phone is IP gateway, which maps the telephone area code of each region to the IP address of the gateway in the corresponding region. These information are stored in a database, and the data connection processing software will complete the functions of call processing, digital voice packaging, route management and so on. ?

When a user makes a long-distance call, the gateway determines the IP address of the corresponding gateway according to the telephone area code database data, and adds this IP address to the IP packet, at the same time, selects the best route to reduce the transmission delay, and the IP packet reaches the destination gateway through the Internet.

In some areas where there is no internet extension or gateway temporarily, you can set up a route, and the nearest gateway can transfer through the long-distance telephone network to realize communication services.

Internet Protocol

At present, the commonly used protocols are H.323, SIP, MEGACO and MGCP.

1、H.323

H.323 is a universal VoIP standard, which was proposed by ITU-T in 1996. It was originally used for video conferencing on local area network (LAN) and later applied to VoIP.

2. Session Initiation Protocol (SIP)

Is the protocol standard for IETF to create VoIP call connection. SIP is an application layer control protocol, which is used to create, modify and terminate sessions with one or more participants.

3. The structure of 3.SIP is similar to that of HTTP (Client-Server Protocol).

The client sends out requests and sends them to the server, and the server sends back responses to the client after processing these requests. The request and the response form a transaction.

4. Media Gateway Control Protocol (MGCP)

It is a VoIP protocol proposed by Cisco and Telcordia, which defines the communication service between the call control unit (call agent or media gateway) and the telephone gateway. MGCP is a control protocol that allows the central console to monitor IP phone and gateway events and notify them to send content to the specified address.

5. Media Gateway Control Protocol

Is IETF and ITU-T(ITU-T? H.248 Recommendation) * * * The result of joint efforts. Megaco/H.248 is a protocol for controlling protocol units of physically separated multimedia gateways, so that call control can be separated from media conversion.

Refer to the above? Baidu encyclopedia-VoIP