SIP basic application
The SIP protocol is one of the main protocols of VoIP communications, which is gradually dominated in the field of VoIP communications in the field of simple, flexible, and openness. The main way of using SIP communication is as follows, the main equipment has a SIP terminal, a proxy / orientation server, a location server, a PSTN gateway and other devices. At present, the latest standards for the development of the SIP protocol are RFC3261, and the main network equipment providers can provide SIP communication devices such as Cisco. On Windows, UNIX and other operating systems, there are also many SIP software phones that can be used because we can see that the SIP phone will become more and more popular in future applications.
IP network
Proxy / Redirect Server
Location
Server
SIP
Terminals
SIP
Terminals
PSTN
Gateway
POTS
SS7
ISDN
PBX
The SIP protocol is a signaling control protocol that constitutes a complete communication system that requires additional SDP, RTP and other media control protocols and media communication protocols. SIP is responsible for the establishment, maintenance, and release of calls. SDP is responsible for the negotiation and control of the media, and RTP is responsible for transmitting communication media.
Enterprise network situation
The main application occasion of VoIP should be a corporate network, so we must enable the current VoIP system to adapt to corporate network conditions to fully play its role. It is generally an internal network, that is, the IP address used by corporate networks, the IP address used by the enterprise network, and the foreign communication, all through a NAT. Implement address conversion. This is because due to the lack of IP addresses, the enterprise network is difficult and ISP application to the global IP address, considering the internal security of the corporate network, companies do not want the outside world to directly access all devices on the enterprise network. Therefore, the internal network address can make the company's self-maintenance network, and the communication of Internet can be implemented by NAT. The internal special server can also map the internal special servers to the Internet through NAT. Users in the public network can access these servers. Such a network structure has a great impact on VoIP in the application of enterprise networks. For example, if the VoIP terminal within the enterprise network If you want to be accessed by an external world, you need to map all the VoIP terminals to the outside, and the maintenance of the network is very difficult. At the same time, this mapping is poor, and the H323, SIP application gateway is implemented in the NAT gateway. Most of the equipment does not support such functions, which thinks that companies will replace network devices, such applications, We believe that most companies are unacceptable.
Internet NetWork
Private network
SIP
Terminals
Private network
SIP
Terminals
SIP Business Network Plan
Considering the application of SIP in the enterprise network, we should provide a means that allows all SIP terminals to be accessed by the outside world, so that VoIP is meaningful in enterprise network applications. That is, the SIP terminal that uses private addresses within the enterprise network can be called called an external SIP terminal, and the IP address of the SIP terminal does not need to be mapped to the outside, and their IP addresses can be obtained by DHCP, or Static configuration.
In this system, considering that the enterprise network is NAT application. If the enterprise network does not have NAT, it is useful for the global network address, and that system can be used, the application mode, and NAT exists are the same.
Private network
SIP
Terminals
Private network
Internet NetWork
The system is mainly
SIP
Terminal and
SIP server consists.
SIP
Terminal and ordinary
SIP
Like the terminal, you can initiate calls, and accept calls, or communicate outside the enterprise network or outside, can be
IP
Telephone gateway,
IP
phone,
IP
Telephone software, etc.
SIP
The server is responsible for the system's call agents, registration services, location services, media services, etc. The premise of the system operation is
SIP
Server requires a global
IP
Address mapping, that is, the enterprise network
NAT
Gateway provides a global
IP
The address is mapped to the server.
The implementation of the SIP terminal and the general device are consistent, but the SIP terminal has a top-bearing server on the configuration, that is, all calls of the SIP must be completed by the SIP server, when initiating a call, first Go to the call server. End the call and the notification server ends this call. These operations are fully compliant with the IETF RFC3261 specification, in accordance with the consistency of the protocol. At the same time, the SIP terminal can be related to the protocol standard in subsequent SDP, RTP processing, and no special processing is required.
The main function of the system is to work on the SIP server, in addition to the RFC standard proxy server, registration server, and location server in addition to the RFC standard. It will also increase the function of media exchange, and the function of media exchange ensures that the system can send the internal network media information to the outside and ensure the external and internal media exchange. Specific implementation, design to the company's technical secrets will provide a detailed scheme after successful cooperation. The SIP server can be implemented on Windows, or UNIX as an application.
Internet NetWork
Private network
SIP
Terminals
Private network
SIP
Servers
SIP
Servers
SIP
Terminals
SIP
Terminals
The system mainly considers the following applications
Internal network call external network
1) Internal SIP terminal initiates a call, this call is sent to the internal SIP server
2) The internal SIP server will complete the function of positioning findings.
3) The internal SIP server sends a call to the external SIP terminal via the NAT gateway.
4) External SIP terminal notifies the internal SIP server call to establish and establish media channels with internal SIP servers
5) The internal server notifies the internal SIP terminal call setup and establishes an internal media channel.
6) Start communication, the SIP server exists as a media exchange server
External network call internal network
1) External SIP terminal initiates a call, call the internal SIP server, and specify an SIP terminal in the internal network in the SIP URI.
2) The internal SIP server determines the internal SIP terminal address according to the URI, call the internal SIP terminal
3) Internal SIP terminal response, establish a call through the internal SIP server and the outside SIP terminal
4) The internal SIP server separates the internal SIP terminal, and the external SIP terminal establishes a media channel.
5) Communication start, internal SIP server media exchange
Internal Network A Call internal network B
1) A Network SIP Terminal Call A Network SIP Server
2) A network SIP server lookup positioning, call to B network SIP server
3) B network SIP server lookup positioning, call B network SIP terminal
4) B network SIP terminal response, reverse notification to A network SIP terminal
5) Communication establishment, A network SIP server and B network SIP server establish media channel, and establish media channel 6 with respective internal networks 6) Communication start, A, B network SIP server runs as media exchange server
Description
What is mentioned in this system is the application of SIP in enterprise network, which can adapt to corporate networks in various situations, and play a great propulsive role in the popularity of VoIP in corporate network. At the same time, the system design is fully referred to the relevant specifications, and it can be fully interoperable with standard devices, and no modifications are required for existing network structures. Promoting to all VoIP protocols, for the application of H323, Megaco protocol, the company can also provide corresponding solutions to address the limitations of applications on enterprise networks.
