AMZ International has a multimedia application server, which facilitates video conferencing and instant messaging within an enterprise network. With multimedia services the setup of a multiparty video conference, between pre registered participants, should be feasible with a few mouse clicks, and collaborative working between remote offices is greatly improved by the sharing of Web sites, files, visuals, and electronic whiteboard.
While IP, at layer 3, defines the addressing and routing rules for data packets, at layer 4 there are three other relevant protocols: user datagram protocol (UDP), Real-Time Transport Protocol (RTP), and transmission control protocol (TCP). UDP is a connectionless protocol, with an emphasis on the minimizing of packet transit time, which is ideal for the interactions that are essential to voice and video traffic. TCP is the connection-oriented protocol that provides confirmation of a packet’s receipt at its destination, if necessary after retransmission and without concern about delay. With a Voice or Video-Conferencing over Internet Protocol (VoIP) session, it is usual to employ TCP/IP for the call setup, any in-progress signaling, and teardown, while UDP/IP is better suited to the real-time transmission of the voice or video conversations.
The bandwidth, or bit rate, requirements for VoIP depend on the type of encoding/decoding (i.e., codec) technique that is used in the digital signal processor (DSP) in the end stations. A reasonably good guideline, with current technology, is to allow 20 Kbps in the network or the access link for each simultaneous voice conversation, or 200 Kbps for a small-group video conference session.