Transmission of compressed voice over integrated services frame relay networks: priority service and adaptive buildout delay

Voice packets must be delivered within a time constraint to be played out at the receiver, and the simplicity of frame relay (FR) protocols makes this difficult to achieve with a low loss rate for integrated traffic. Highly compressed voice is more sensitive to losses than uncompressed voice and also changes the nature of the traffic in a FR network because of the short length of the voice frames. Priority for voice is shown to be highly desirable to achieve high voice performance where low-speed access links may be used for integrated service traffic. Packetised voice transmission also requires that the receiver compensate for the random queuing delays experienced by each voice packet. The packetised voice protocol (PVP) achieves this by using delay stamps created in packet switching nodes at the packet level, but this is not possible in FR networks because they have no packet level. The authors propose an adaptive buildout delay mechanism which requires no action by the switching nodes, meets the requirements of random delay compensation with acceptable loss rates, and achieves shorter end-to-end voice delay than the PVP.