Differences between H.323 and sip

The development of VoIP technology has two major directions: one is to follow the ITU H.323 standard, and the other is to follow the IETF's SIP protocol.

ITU's H.323 is basically a mature open standard system that combines the traditional call process and the characteristics of the IP network, representing the trend of VoIP. In particular, it draws on many experiences in the networking, interconnection and operation of telecommunication networks, and can interwork with the PSTN network and other data services and application networks. This is an important reason why the H.323 standard has been widely used around the world since 1995. Using the H.323 technical system, VoIP operators can basically inherit the management and O & M modes of traditional operators-this is especially important for establishing a large VOIP network in China and Southeast Asian countries. In China, all the VOIP networks set up by operators are large nationwide networks with extremely high requirements on network scalability and stability. The network must be deployed in multiple layers and regions, covering up to 400 cities, the monthly traffic is more than several hundred million minutes. The adoption of H.323 technology is an appropriate choice for building such a large network. Some new technologies may be better at combining data with speech, but they do not have much to consider about networking, operation, and management.

Another development trend of VoIP technology is following the SIP protocol proposed by IETF. The SIP protocol is very popular in the United States and has developed rapidly recently. This is because:

① Internet technology in the United States has developed rapidly.

② The implementation conditions at the early stage of SIP technology development are relatively simple.

In the fully open telecommunications environment in the United States, "Simplicity" can bring great creative temptations and imagination, in addition, it attracted a number of domestic equipment manufacturers in the United States, as well as emerging operators and service providers to invest a lot of money and energy. The SIP technology is basically based on the dynamic Internet mode. Its network is not a multi-layer network, but a flat single-layer network. The call process is different from that of the PSTN network. For example, if a user calls Shanghai region no. 021, the user first considers how to send the call to Shanghai and then to the destination over a VOIP network established Based on H.323. Its addressing and networking methods are extremely similar to those of traditional telephone networks. However, on the SIP network, dynamic databases are used for addressing, and there can be no long-distance or short-distance connection. The advantage of the SIP mode is that it is closely integrated with the Internet and is suitable for developing new voice applications that are integrated with the Internet. Its disadvantage is that it still needs to be mature in terms of networking, management, operation, and billing, in terms of intercommunication with the traditional PSTN network, the handling of some abnormal situations still needs to be improved, and experience needs to be accumulated in establishing a large VOIP network.

It should be said that it is appropriate to select the H.323 technical standard in China and Southeast Asian countries to form a VOIP network. This is because the telephone penetration rate in these countries is not high and the demand for basic call services is growing rapidly. This means that for a long period of time, the voice service will still run according to the traditional operation and management system, this requires the VOIP network to have a call process and processing mechanism close to the traditional telecom network, with good scalability, manageability, and operation, and good interconnectivity with the existing PSTN network. Different from China's national conditions, the US's telephone penetration rate has reached 90%, and the Internet is growing rapidly. Therefore, the VoIP strategy focuses more on value-added applications of the Internet. You must know that the concept of creating an Internet value-added service network and a telecom-class VOIP network is different. Currently, the largest basic business VOIP network is in China.

Softswitch Technology

So what is Softswitch technology and soft switch? Broadly speaking, all the telecom-level voice service solutions based on packet switching technology can be classified as Softswitch technology. In terms of technical implementation, both H.323 and SIP can be classified as Softswitch technologies. The Softswitch technology and concept come from the "hard" technology and concept of traditional TDM. Therefore, the concept of Softswitch is growing and mature along with the development of VoIP technology. H.323 and SIP represent two relatively independent and parallel development trends. They are two relatively complete systems with voice service signaling systems. VOIP gateways can be divided into pure media gateway mg and media gateway controller MGC for centralized control and management. The control protocol is MGCP.

MGCP is only a Device Control Protocol and is not an independent VoIP Signaling System technology. MGCP only exists as a supplementary protocol for the two systems of H.323 and sip.

Soft switches are a specific implementation of Softswitch technology. In a narrow sense, people will become accustomed to calling proxy or soft switch after slightly expanding the MGC function of the Media Gateway controller using MGCP as the control means. MGCP has added some new integrated services, such as billing and Configuration Service Management, to the original media gateway controller. Therefore, MGCP has not brought about a technological revolution. In fact, this is only a manifestation of Softswitch technology and practices. MGCP-Based Soft switches must also clearly support the VoIP "Inter-board" signaling system for interconnection and networking. The use of non-open standard MGCP soft switches is not suitable for forming a carrier-class VOIP network. Therefore, strictly speaking, the available Standard MGCP soft switches can also be referred to as H.323/MGCP soft switches or SIP/MGCP soft switches.

In addition, the soft switch can use H.323 and SIP to control the smart VoIP gateway with calls, resulting in the generation of H.323 soft switches and SIP Soft switches, however, due to the distribution of H.323 and sip and the characteristics of multi-host architecture, we generally call it a softswitch system. MGCP soft switches are called monolithic soft switches.

The advantage of MGCP is that the software structure of MGCP devices tends to be traditional switches, which facilitates centralized management. Its weakness is that it does not push intelligence to the edge like H.323/sip, but is highly centralized. The high concentration brings about the performance of the soft switch, and the functions and prices will pose great challenges in the practice of large networks. It is worth noting that its value-added services and networking depend on soft switches and are not suitable for Internet applications. Based on this, MGCP soft switches are only suitable for local applications. If MGCP soft switches are fully used to build a telecom-grade large network, the possibility of networking with a soft switch as the center is possible, its flexibility, scalability, business consistency, and performance-to-price ratio cannot meet the actual requirements of Chinese operators. To this end, Cisco has proposed a networking principle for next-generation VoIP networks in China, with distributed Softswitch networks as the core, supplemented by Softswitch systems and soft switches.

Practices of Softswitch networks

At present, China Unicom's VoIP network, the world's largest VOIP network, is based on H.323. Cisco's next-generation distributed softswitch network technology was developed. Not long ago, China Unicom officially announced that it would continue to use cisco's IP-based VoIP and telecom-level solutions to expand its IP phone network coverage to 350 cities nationwide, as a result, China Unicom became the world's first carrier to provide voice transmission services nationwide on the data network. Phase III of the expansion of China Unicom uses Cisco GSR, 7500 series routers, telecom-grade Voice Gateway as5800, as5300, 7200 gatekeeper, network service function server FS, catalyst series switches, and pix firewalls.. China Unicom's VoIP network adopts Cisco's unique networking idea with multi-domain, layer-3, full-service, distributed softswitch network as the core, construct a second-level VoIP management system and a multi-application value-added business platform. China Unicom's VoIP physical network is compatible with H.323, MGCP, and SIP traffic. This VOIP solution not only guarantees the unlimited scalability of the network, but also ensures the high reliability of the core application platform for fault tolerance and disaster tolerance from the system mechanism. More importantly, this networking solution integrates the characteristics of the Softswitch technology and the limitations of the Cross-hop single-host soft switch.

Cisco VoIP telecom-level solutions support a national-level traffic network system to fully meet the business development needs of enterprises. This solution features high interface density, good voice quality, flexible configuration, and convenient management and maintenance. Especially in terms of voice quality, it ranks first among the evaluations of international third-party organizations, it has been widely used by many business providers around the world.