ransmission. Other- cessful data/voice converged network. The VFRADs' wise, the long data frames are sent intact. prioritization schemes "tag" different applications according to their sensitivity to delay, assigning higher Controlling variable delay on VoFR priority to voice and other time-sensitive data such as Variation in the arrival times between voice or data SNA. The VFRADs let the higher-priority voice packets packets, also called jitter, causes unnatural-sounding go first, keeping the data packets waiting. This has no voice instead of a smooth voice stream. If a packet does negative effect on data traffic, as voice transmissions are not arrive in time to fit into the voice stream, the Frame Header Information Field 1 Octet 2 Octets User Data Variable Length 2 Octets 1 Octet (IP, SNA, or X.25 Are Typical Examples of Payload Format) DLCI (High-order) DLCI (Low-Order) Format of a typical Frame Relay data packet Figure 3.2-5 A typical Frame Relay data packet. CHAPTER 3.2 Network infrastructure previous packet is replayed. This can seriously detract Minimal number of virtual links (DLCIs) between from voice quality. To avoid the effect of jitter, VFRADs sites detain each packet in a jitter buffer, giving subsequent Voice, signaling, and data over a single DLCI packets time to arrive and still fit into a natural voice flow. Efficient switching of compressed voice Because the jitter buffer adds to the overall delay of voice Support and conversion of signaling methods transmissions, the optimal jitter buffer should fit the Transparent physical interfaces network's differential delay. Also some advance access Integrated fax support devices in the market employ adaptive jitter buffering, which continuously monitors the network delay and ad- In addition, the VFRAD should offer the following ad- justs the queuing period accordingly. vanced PBX features: Programmable out-of-service indication Voice compression Digit manipulation and DTMF generation (storing and Voice compression allows the packet switching network fo