s via non-facility-associated signaling (NFAS). An orga- nization with six PRI trunks might have four of them equipped with 24 channels for voice and data. Two of the six would have 23 channels for user data and one signaling channel each with NFAS to support all six PRI trunks. Having two PRI circuits with signaling provides a backup in case one signaling channel fails. PRI lines don't work without a signaling channel. Frame Relay Frame relay is an older, slower Virtual Private Network (VPN) that has largely been replaced by Multi-Protocol Label Switching (MPLS). Frame relay is a public network offering with which customers can transmit data between LANs at multiple locations. It also is used to access the Internet. Frame relay was first promoted as a lower-priced substitute for private lines. By using frame relay, organizations do not have to plan, build, and maintain their own duplicate paths to each of their sites. Multiple users share the frame relay networks. Frame relay requires defining links between sites in advance. This can be cumber- some for large organizations that want to connect each of their many sites to every other site. Falling prices on MPLS service and frame relay's unsuitability for voice are other reasons why organizations have largely migrated to MPLS. In addition, carriers do not want the expense of supporting separate frame relay networks. MPLS operates over a provider's private IP data networks. Appendix APPENDIX Table 5-2 An Overview of Broadband Network Services Network Service Places Typically Used How Used Commercial Internet access, connec- 24 voice or data channels organizations tions to long-distance and 1.54Mbps local telephone companies for voice and data, private 30 voice or data channels, lines between company 2Mbps plus one channel for sites. signaling and one for fram- Each channel = 64Kbps. ing and remote maintenance E1 is the European ver- sion of T1. Large and midsize Access to long-distance 672 voice or data channels, organizations companies, Internet equivalent to 28 