es exist in the network, nine local links will run from each site to every other site (10 X (10 - 1) / = 45). This enhances the speed of connectivity, but the network costs are much higher. Further, depending on the nature of the data traffic, the bursty data needs of a LAN- to-LAN or LAN-to-WAN connection are not required full time. We, there- fore, spend significantly more of the organization's money to support the meshed leased-line network. A Frame Relay access from each site is provided into the network cloud, requiring only a single connection point rather than the nine of the earlier network, as shown in Figure 9-8. Data transported across the network will be interleaved on a frame-by-frame basis. Multiple sessions can run on the same link concurrently. Communications from a single site to any of the other sites can be easily accommodated using the predefined network con- nections of the virtual circuits. In Frame Relay, these connections use Per- manent Logical Links (PLLs), more commonly referred to as PVCs. Each of the PVCs connects two sites just as a private line would, but in this case, the bandwidth is shared among multiple users rather than being dedicated to the one site for access to a single site. Using this multiple-site connectiv- ity on a single link reduces the costs associated with CPE, such as CPU ports, router ports, or other connectivity arrangements. Because fewer ports Figure 9-7 The meshed network. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. PCUSN-to-SGSN Interface (Gb) Chapter 9 Figure 9-8 The Frame Relay solution. are required, fewer connection devices are required; therefore, the customer (in this case, the GPRS operator) saves money. Because the PVCs are predefined for each in a pair of end-to-end con- nections, a network path is always available for the customer's application to run and transport data ac