Introduction to SIP Agreement and New IP Enterprise Communication Network Technology-Core SIP Technology Introduction -1


From this chapter, we will officially introduce the SIP protocol and knowledge related to its application. Before starting our SIP protocol and the introduction of the new IP communication network technology, in order to allow some basic users to comprehensively master the complete architecture of technology, we need to spend a little time discussing several basic core issues or understanding. These contents include from SIP The basic concepts and the advantages of using the SIP protocol, the module address of the SIP protocol, the server -side processing method, the SIP client configuration, and the necessary knowledge such as B2BUA, proxy, and routing. In the discussion below, the author will gradually start sharing these contents.


What is SIP protocol technology

The SIP protocol and related technologies involve the abstract level of the agreement to the very specific terminal products, the control logic of the server application scenarios and the business level. In addition to these contents, SIP technology also involves some other necessary attributes. Based on the length -based relationship, we need to introduce some very core content to the readers here, and simply introduce how to learn knowledge to share.


First, we need to understand what the SIP protocol is. The full name of the session initiation protocol (SIP) is the initial agreement of the session. We can split out its complete name to brief analysis:

Session Initiation Protocol (SIP):




The earliest official version of the SIP protocol was RFC2543 in 1999, and it was reached into RFC3261 in 2002. This specification has always been the basic standard official of the current SIP network. The core inventor of the SIP protocol is still active in the current business field. The well -known call center’s Five9 CTO Jonathan Rosenberg (SIP core author) is one of them. Another well -known is Henning Schulzrinne, a professor of Columbia University, focusing on SIP and RTP research. The author used to visit his school’s webpage, and further studied through some of his books. There are still many very valuable reference books and tools on its page. If readers are interested, they can access the reference link for further learning.

When we talk about the network protocol, it is basically very abstract. It does not involve each product of specific products, but it needs to be reflected through specific products. The specific products must abide by the rules of its agreement, so that other products can work with them. If we are a little rigorous to further explain its abstraction, we can explain it. We have never seen a car (because the car itself is a total abstraction of a car), but we have seen which model of Toyota Motors, Toyota Motors. In the discussion on SIP, we also face discussions. Everyone has basically seen the SIP phone or voice gateway, but you have never seen SIP. Therefore, when readers understand the SIP protocol and its technical application Introduction we discuss, many readers are more confused and especially need readers to repeatedly learn from abstraction to specific control.

From the basis of the SIP protocol, most of the network applications need to create management sessions when working, and to achieve control management of network protocols through session management. The session is the data exchange between participants. Because the SIP protocol is a agreement from the development of the HTTP protocol, the basic characteristics of the session can also be understood through the session of the HTTP protocol. The session realizes a data interaction. The data exchange of both parties includes at least the ID of the session, the life cycle, the timer, and the end of the management process. These basic features are also applicable to SIP -based sessions. Data that are interacted between the two or multi -party interaction is nothing more than videos, text, and voice, and of course, including some management needs in the interaction process. We will further say that if the SIP process is to perform session exchange, there must be a initial party to launch a task. It is necessary to know whether the two parties can work, whether they are willing to accept each other’s work requirements, etc. These are controlled by the agreement. After the initial process is started, until the data interaction is completed, the two parties stop work by ending control. These specific procedures also need to be agreed to manage. In the SIP protocol, many more specific details control through various definitions and naming. Therefore, from the whole, basically the SIP protocol needs to implement the control signaling protocol, media (audio and video text) session control, positioning user address, user online status and creation/modification/end session. We will further discuss in the subsequent chapters. I won’t go into details here.

The early learning SIP protocol and related technologies are very boring. If the reader can understand the SIP protocol from the abstract level, and at the same time, it can combine the specific SIP terminal or server -side architecture, and the reader basically understands the overall technical architecture implementation. If readers learn SIP and related technologies more than ten years ago, because of the limitations of various hardware environments and network use needs, it is difficult for general users to contact the complete test learning environment. With the development of open source soft switching and terminal technology, readers can test and learn in a very low cost way, and people can almost simulate most application scenarios. Through low -cost learning environment, some commercial products can complete the entire learning path from abstraction to specific learning.


Why use SIP

SIP technology is a technical trend, which is an inevitable result of a market choice. From the global hot word search, we can see that in recent years, the proportion of SIP search has been very high. Instead, H323 has been in the trend.

This picture and the following pictures come from Internet resources


If we look at the market statistics, the market for the SIP Trunk service has been increasing, and H323 has gradually been replaced by SIP TRUNK operators.

From the perspective of functional implementation, compared with H232 and SIP, certain functions can no longer meet modern network requirements. The following is a functional comparison of Cisco. Therefore, technology iteration is inevitable.

There are several reasons for users to choose to use SIP. Many authoritative research institutions and market research companies have published many articles about SIP technology. Readers can also refer to the author’s previous documents, analysis and release of the integration communication market: the latest model of the development of enterprise integration communication business

In addition to the content of the author’s previous discussion, there are still a few thought content to be added here.

Some mainstream operators abroad have begun to provide more services through SIP, such as AT & T, Verizon, Vodafone and other famous service providers. At present, the more famous call centers services and fusion communication service providers in the market, such as 8X8, Ringcentral, Five9 and other providers also provide their services through SIP. Some countries have clearly stopped operating the PSTN network and no longer provide PSTN services to users. Britain announced that by 2025, British operators will no longer provide PSTN services and provide services through SIP. Many countries will stop the operational services of PSTN networks.

In addition to some commercial institutions and the country clarified SIP as the main relay service, because the development of open source technology and Internet technology and the cross -platform characteristics of business models, cross -regional characteristics require the support of SIP technology. At the same time, SIP technology is just satisfied It has its service scenario. The open source -based SIP application platform is very rich. Users can choose the SIP soft switching server (Kamailio/OpenSips).


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Sofia sipsip.js


) Different tools such as clients to adapt to a variety of complex business models. The SIP terminal can fully deploy in various application scenarios, and has very good mobility, the Internet of Things access support, edge terminal integration support, voice data collection terminal support, and can be seamlessly compatible with embedded ARM products. We can not exaggerate the reason why the people and the SIP technology are very popular. Other technologies have not encountered such a good time, and some technologies themselves are also limited by the environment at that time, and it is normal to be abandoned by the market. At the same time, various software and hardware IP product manufacturers will not waste this opportunity. Everyone has launched their own SIP platform -based IP network devices and solutions, including Cisco, Microsoft, Avaya, Ribbon, SANGOMA, Oco, Aoko, Austri,, Okuke, Aoco, Austrian, Austrian, Austri,, NEC includes well -known domestic manufacturers Dingxin Tongda and Sanhui.

In addition to corporate integration communication, there are many dispatching systems and emergency command centers in the domestic market. The business processing of media flow is integrated through various SIP terminal devices and upstream server -side.

Another latest driving force about SIP further integrated into the actual voice application is WebRTC. WebRTC has been very hot in recent years and has been deployed in various user scenarios. It is perfectly combined with SIP. A video conference platform based on WebRTC is still a business such as other video call centers, and the SIP protocol is still required. Regarding the basic technical summary of WebRTC, readers can refer to: Complete WebRTC technology and application summary

From the perspective of the operator, the background of the service provider’s perspective and the development of surrounding technologies discussed the reason why SIP technology is so popular. Of course, the premise of technology popularity is that users have finally received benefits, and service providers or manufacturers have the motivation to develop. From a user perspective, several benefits of SIP are also very obvious:


Low cheap voice spending, rich SIP TRUNK resources

Rich service support, including voice conferences, video conference services, subscribing services, such as call centers, IPPBX

Rich various interface services can be connected with platforms such as voice recognition

Users can very clearly know the other party’s online status, which is convenient to communicate in a timely manner

With strong and flexible mobility support, satisfy the soft telephone terminal and physical terminal support, and at the same time realize the movement of the office environment. The corporate communication platform has the ability to provide employees with remote office, mobile office, office work and other working methods to realize a very good user experience

SIP -related products can realize local software and hardware deployment methods. At the same time, various deployment methods based on cloud platforms can be achieved, which meets the use scenarios of different user groups.



SIP protocol and related peripheral protocols

We know that the SIP is defined in the definition of RFC3261 that SIP is only responsible for SIP signaling negotiation, and the processing process other than signaling consultation requires other protocols to support. The following example briefly illustrates a SIP call through UDP or TCP for transmission, with the SDP description of the explanation of the media, and finally transmits various voice support through RTP.

Discuss the SIP protocol, we need to cooperate with other surrounding agreements to discuss. There are many signals around the peripheral, including

SIP core related agreement and concept definition


Session description related protocols


, Expansion Agreement, PSTN/3GPP protocol, service function and quality assurance protocol. Through a complete SIP vein legend, it helps users can fully understand the application of the entire SIP and related technologies, while establishing a complete technical architecture. If readers are interested in understanding all related SIP protocols and surrounding protocols, you can click the link below to read the specific content:

Graphical complete SIP protocol and related peripheral protocols

In the discussion of our basic introduction, the author hopes that the reader will first understand a few basic agreements:

RFC3261-SIP core specification








Although the author lists many related agreements, because of our limited time and knowledge background, we cannot have a deep understanding of all knowledge. In order to ensure that readers can understand their knowledge system through a knowledge architecture, it is still recommended that readers can properly involve some necessary agreements to deepen the further understanding of the SIP protocol and applications.



In this article, the author first introduced the basic content of the SIP protocol, and also introduced why the SIP protocol in the market has become the mainstream agreement and its development and growth. In the next chapter, the author will specifically introduce some of the core concepts of SIP and various server -side processing processes.

Reference materials:

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