Listen to H.323 experts to elaborate on VoIP standards (1)

China officially opened its IP phone service in April 1. To this end, the Ministry of Information Industry has officially promulgated the General Technical Requirements for IP Phone/fax services, the technical requirements for IP Phone gateway equipment, and the technical specifications for IP Phone gateway device interconnectivity. other IP phone standards are being developed. To stay consistent with international standards, the IP standards research group recently invited ITUT H.323 standard editors, Cisco VoIP experts Richard Bowen and Paul E. mr. Jones came to Beijing to attend the China standards seminar and asked them to give a brief introduction to ITUT H.323 version 4th. Afterwards, the reporter had the honor to interview the two experts.

H.323 has the characteristics of a telecom-grade large network.

Two experts said that version 3rd of H.323 has been completed and version 4th will be finalized in May. Versions 2nd and 3rd have enhanced and improved the features of building a telecom-grade IP telephone network, the solution focuses on the stability, redundancy, and scalability of IP address telephone networks to ensure the quality of calls. It can be said that H.323 is a mature protocol and has the characteristics of a telecom-grade large network.

The two experts explained some hot questions about VoIP standards. Currently, there are two standards for building an IP Phone architecture: H.323 recommendations and SIP protocol. The two are completely parallel, and they achieve the same purpose-to build an IP address telephone network, but they use different methods, so they cannot be compatible with each other, but there is only a problem of intercommunication between the two. H.323 is proposed for Multimedia conference systems, not for IP phones, but for IP phones, especially those through the gateway, we recommend that you use the H.323 protocol to complete the required work. Therefore, we recommend that you use the "borrow" protocol as the IP Phone Number Standard. For IP phones, it not only uses H.323 recommendations, but also uses a series of recommendations, including H.225, H.245, H.235, H.450, and H.341. We only recommend that you set "General Technical Requirements" for H.323. Therefore, IP phones in this mode are usually called H.323 IP phones. The H.323 recommendation is a relatively complete proposal, which provides a centralized processing and management mode. This work mode is adapted to the management of telecommunication networks, especially for the construction of IP telephone networks from telephone to telephone. Both theory and practice show that H.323 is capable of making an IP Phone System of any scale.

The SIP protocol proposes another architecture of IP phones, which is a parallel protocol with H.323. The SIP protocol is simple, scalable, and closely related to existing Internet applications.

The starting point of the SIP protocol is to build an IP telephone service network based on the existing Internet. Therefore, SIP has a completely different design concept from H.323. It is a distributed protocol that pushes the complexity of network devices to the edge of the network, compared with IP Phones Based on the H.323 protocol, the SIP protocol requires relatively smart terminals. When a user terminal is a non-Smart terminal, the SIP protocol can also be used as call signaling, but this will greatly weaken the unique advantages of the SIP protocol. Therefore, the SIP protocol is more suitable for smart user terminals. In addition, you can consider adding a front-end server to the user's phone to replace the gateway device. The cost of this operation is to increase the overhead of the user's purchase of the front-end server.

The other two Protocols, MGCP and H.248, are not at the same level as the previous two. They do not involve the architecture of IP phones, but only involve gateway decomposition issues, therefore, they can be used not only in the H.323 IP phone system, but also in the sip ip phone system. H.248 is recommended to be consistent with MGCP in terms of basic ideas, but H.248 has greatly promoted MGCP. It should be said that the proposed H.248 has replaced MGCP and become the protocol standard between MGC and MG. Splitting a gateway into a media gateway (MG) and a media gateway controller (MGC) is required to develop a large-scale telecom-grade IP Phone gateway.