ed with a 2X burst. As you can see in the graph, as traffic exceeds the 2X burst threshold, it is discarded. A graph such as this indicates that the link is saturated and needs to be upgraded. A good rule of thumb is to order more bandwidth when your link reaches 70 percent utilization. This circuit should have been upgraded long ago. Port speed 1536 kbps All Frames in this Burst 1024 kbps range are discard-eligible 512 kbps 0 Mbps Figure 22-4. Frame-relay CIR and DE frames Frame-Relay Network Design Frame-relay links are more flexible than point-to-point links because multiple links can be terminated at a single interface in a router. This leads to design possibilities allowing connectivity to multiple sites at a significant cost savings over point-to- point circuits. Frame-Relay Network Design Figure 22-5 shows three sites networked together with frame relay. On the left, Router B and Router C are both connected to Router A, but are not connected to each other. This design is often referred to as a partial mesh or hub and spoke network. In this network, Router B can communicate to Router C only through Router A. Router B Router B Router A Router A Router C Router C Partial mesh or hub and spoke Full mesh Figure 22-5. Meshed frame-relay networks On the right side of Figure 22-5 is an example of a fully meshed network. The differ- ence here is that all sites are connected to all other sites. Router B can communicate directly with Router C in the fully meshed network. Meshed networks are not strictly the domain of frame relay. As you can see in Figure 22-6, a fully meshed network can easily be created with point-to-point T1s. Router B Router B Router A Router A Router C Router C Frame-relay Point-to-point full mesh T1 full mesh Figure 22-6. Frame-relay versus point-to-point T1 meshed networks Chapter 22: Frame Relay In a frame-relay network like the one shown on the left side of Figure 22-6, each location needs a router that can support a single T1. Each one of the PVCs can be configured as a separate virtual inte