ber-which can ensure that the data is diverted to the protect fiber within a 50-millisecond time frame. SDH/SONET is now being replaced with WDM-based networks, but while early Chapter 7 Wide Area Networking WDM systems did not provide for network restoration, the new generation of products do address this critical feature. (See Chapter 11 for discussion of optical networking technologies and trends.) Recent introductions of VoIP services and streaming media have exposed two other limitations of IP networks: latency and jitter. IP doesn't provide a way to con- trol latency and jitter. For a packet-based IP network to successfully support voice services, minimum transit delay must be achieved, and SO must minimum packet loss. High-quality voice demands less than 100 milliseconds for total one-way latency, including all processing at both ends, which implies digitization, compres- sion, decompression, queuing, playback, and so on-and that must also include the network delay. Voice compression and decompression alone normally take about 30 to 50 milliseconds. Network latency must be tightly controlled to support these services properly. One immediate solution to the problems of latency and jitter is to increase the amount of available bandwidth. If there's no congestion, there's no problem. And technologies such as DWDM provide relief initially, but history has taught us that the amount of data continues to increase significantly and rapidly, and while throwing bandwidth at the problem provides a quick fix, it does not address the growing need for detailed traffic and network management. Increasing bandwidth also does not provide the control mechanisms necessary for providing, tracking, and accounting for multiple and granular levels of service that the service provider can offer and guarantee for the customer. Therefore, simply providing more band- width is a short-term relief measure but not a long-term solution that addresses the need to differentiate traffic and its requirements on a very granular level. Hence t