ribe the methods implemented to enable the Frame quality, the delay of voice packets across the network Relay network to carry voice as well as data. In particular, must be minimal and fixed. Due to the shared nature some of the common voice-enabling techniques in- of the packet/cell-switching network, it might take corporated into VFRADs are described in the following time for transmissions to travel across the network. A sections. transmission can be delayed because of network con- gestion. For example, it might "get stuck" behind The nature of the data network and its a long data transmission that delays other packets. implications for voice Network congestion can also result in dropped packets, Frame Relay is known as packet-switching technologies. which also detrimentally affects the integrity of voice This is in contrast to the public telephone network, transmissions. which is a circuit-switching technology, designed to carry voice transmissions. Frame Relay inserts data into vari- Voice-enabling the data network able-sized frames or packets. Unlike most data applications, voice is very sensitive to The packet-switching and cell-switching networks delay. Good voice quality provides a faithful recreation of perform statistical multiplexing. That is, they dynami- the conversation, with the inflection, pauses, and in- cally allocate bandwidth to various links based on their tonation used by the speakers. Long and variable delays transmission activity. Because bandwidth is not reserved between packets result in unnatural speech and interfere for any specific path, the available bandwidth is allotted with the conversation. Dropped packets result in clipped according to network needs at any particular time. speech and poor voice quality. Fax transmissions are even Compare this to the traditional voice (or more sensitive to the quality of the transmission and are circuit-switching) network, in which a path is dedicated less tolerant of dropped packets than voice. to the transmission for the duration of the call, w