multimedia over IP (MoIP)

Multimedia over IP (MoIP) is a real-time technology with which multimedia data is transmitted using the IP protocol. Due to the constant expansions and the available bandwidth, the Internet is also suitable for the transmission of multimedia and audiovisual data.

Several real-time protocols for multimedia applications have been developed for this purpose. Another aspect is that data and multimedia services integrated on the Internet can be integrated without additional hardware and further interfaces. However, the IP protocol and the Internet with its packet-switched structure are not necessarily ideal for real-time applications. In addition, multimedia applications are usually multicast transmissions where the same data stream - not copies - is transmitted to a group of receivers. For example, video conferencing requires video data to be transmitted simultaneously to all conference participants. Real-time video can even be sent to several thousand recipients.

Requirements for real-time transmission

As for real-time protocols, their development must take into account the reduction of traffic and, in addition, a certain bandwidth must be guaranteed during transmission. Thus, for real-time transmissions, some resource reservation mechanisms must be considered. Since the Internet is packet-switched, the different data packets are routed independently over the network, resulting in different propagation times. This aspect must also be taken into account in the real-time protocols and must not exceed 0.3 seconds for Internet telephony. The replay of the real-time data must be continuous with correct timing and synchronization.

If sufficient bandwidth is available, all the above requirements can be met using the best- effort principle. The solutions for Multimedia over IP (MoIP) lie in the classification of all traffic and the allocation of priorities to the various applications. For this purpose, the Internet Engineering Task Force( IETF) has developed a model for advanced Internet services, the Integrated Service Architecture( ISA), which includes the best-effort principle and real-time service and is addressed in RFC 1633.

The Realtime Transport Protocol( RTP), Resource Reservation Protocol( RSVP), Realtime Control Protocol( RTCP), and Realtime Streaming Protocol( RTSP) have been developed for real-time transmission.