Session Initiation Protocol: the most popular communication protocols are now mature (1)

Introduction

Communication providers and their partners and users are increasingly eager for a new generation of IP-based services. Now we have SIP (Session Initiation Protocol), which is a pressing problem. SIP was born less than a decade ago in the computer science laboratory.

It is the first protocol suitable for multi-user sessions in various media content. Now it has become the specification of the Internet Engineering Task Group (IETF.

Today, more and more carriers, CLEC (competing with local carriers), and ITSP (IP phone service providers) are providing SIP-based services, such as local and long-distance telephone technology, online information and instant messaging, IP Centrex/Hosted PBX, voice messaging, push-to-talk (key-press call), and Multimedia conferences. Independent software vendors (ISVs) are developing new development tools to build SIP-based applications and SIP software for carrier networks. Network equipment suppliers (NEV) are developing hardware that supports SIP signaling and services. Currently, many IP phones, user agents, network proxy servers, VOIP gateways, media servers, and application servers are using SIP.

SIP uses similar authoritative protocols, such as Web Hypertext Transfer Protocol (HTTP) formatting and Simple Mail Transfer Protocol (SMTP) email protocols-evolved and evolved into a new and powerful standard. However, although SIP uses its own unique user proxy and server, it does not work in an integrated manner. SIP supports integrated multimedia services and works with a large number of existing protocols for identity authentication, location information, and voice quality.

This White Paper provides a general introduction to SIP and its functions. It also introduces the process of SIP from lab development to market-oriented. This White Paper describes what services are provided by SIP and what development programs are being implemented. It also details the important features of different SIP protocols and describes how to establish a SIP session.

Next-generation services

SIP is flexible, scalable, and open. It inspires the power of a new generation of Services launched by the Internet and fixed and mobile IP networks. SIP can complete network messages on multiple PCs and phones and simulate Internet sessions.

Unlike the long-standing International Telecommunication Union (ITU) SS7 standard (for call establishment) and ITU H.323 Video protocol combination standard, SIP works independently of the underlying network transmission protocol and media. It specifies how terminal devices of one or more participants can establish, modify, and interrupt connections, regardless of voice, video, data, or Web-based content.

SIP is much better than some existing protocols, such as the Media Gateway Control Protocol (MGCP) that converts the PSTN audio signal into IP packets ). Because MGCP is a closed voice standard, it is complicated to enhance it through the signaling function. Sometimes, the message is damaged or discarded, which prevents the provider from adding new services. With SIP, programmers can add a small amount of new information to messages without affecting connections.

For example, a SIP service provider can create a new media that contains voice, video, and chat content. If the MGCP, H.323, or SS7 standard is used, the provider must wait for a new version of the protocol that supports this new media. If you use SIP, although the gateway and device may not be able to recognize the media, companies with branches on two continents can achieve media transmission.

In addition, because the message Construction Method of SIP is similar to HTTP, developers can easily use common programming languages (such as Java) to create applications. For carriers that want to use SS7 and advanced intelligent network (AIN) to deploy call wait, caller ID Recognition, and other services after several years, if you use SIP, deployment of advanced communication services takes only a few months.

This scalability has already achieved significant success in more and more SIP-based services. Vonage is a service provider for users and small business users. It uses SIP to provide users with over 20,000 digital city calls, long calls, and voice mail lines. Deltathree provides Internet telephone technology products, services and infrastructure for service providers. It provides a SIP-based PC-to-phone solution that enables PC users to call any phone number in the world. Denwa Communications wholesale voice services worldwide. It uses SIP to provide caller identification, voice mail, teleconference, Unified Communication, customer management, self-configuration, and Web-based personalized services from PC to PC and telephone to PC.

Some authority predict that the relationship between SIP and IP will develop into a relationship similar to SMTP and HTTP and Internet, but some people say that it may mark the end of AIN. So far, the 3G community has selected SIP as the next-generation mobile network session control mechanism. Microsoft has selected SIP as its real-time communication policy and deployed it in Microsoft XP, Pocket PC, and MSN Messenger. Microsoft also announced that the next version of CE.net will use the SIP-based VoIP application interface layer and promise to provide SIP-based voice and video calls to users' PCs.

In addition, MCI is using SIP to deploy advanced telephone technical services to IP users. The user will be able to notify the caller whether they are free and the preferred communication method, such as email, phone or instant message. With online information, users can also instantly establish chat sessions and hold audio meetings. Using SIP will continuously implement various functions.