Frame relay is a high-speed, packet-switching WAN protocol that connects geographically dispersed LANs. Frame relay (FR) is usually offered by a public network provider; however, private organizations can acquire and manage their own frame relay networks as well. You can configure frame relay on any WAN interface on the gateway.
Frame relay is a connection-oriented protocol, which means that it relies on end-to-end paths between devices connected across the network. It implements these connections using permanent virtual circuits (PVCs) or switched virtual circuits (SVCs). Contivity Secure IP Services Gateway supports PVCs.
The Contivity Secure IP Services Gateway functions as a frame relay access device (FRAD) in a frame relay network. In frame relay, there are multiple virtual point-to-point connections (virtual circuits) on a single physical interface. Each virtual circuit has a unique local IP/remote IP point-to-point connection.
Each PVC on the Contivity Secure IP Services Gateway is a separate IP address. With frame relay, IP addresses are assigned to virtual circuits, and the virtual circuit is in turn associated with a physical interface. Also, there may be multiple PVCs on a single physical interface, and hence multiple IP interfaces on a single physical interface. In PPP, there is only a single IP address per physical interface.
Figure 27 shows a single public interface to an ISP. In this scenario, a frame relay PVC is configured between Contivity 1 and the ISP for Contivity 2 and 3. The PVC replaces a dedicated PPP connection. The frame relay PVC is generally less expensive than the dedicated PPP link.
Figure 27 Frame relay single public interface to ISP
Figure 28 shows three frame relay PVCs (logical connections) running over a single interface on Contivity 1. These logical connections would not be possible using PPP. The connections in this example do not have to be branch office tunnels. They could also be unsecure, clear text connections over the secure frame relay private network.
Figure 28 Frame relay multiple public interfaces
Figure 29 shows a gateway between an existing frame relay network and a new IP VPN network. Contivity 1 acts as a gateway between the newer unsecure public network (Internet) and the older, secure frame relay private network. Contivity 1 is connected to Contivity 2 and 3 using a branch office tunnel over a frame relay PVC. Contivity 1 is also connected to the BayRS router using a clear text WAN connection over another frame relay PVC, which takes advantage of the WAN as secure interface.
Figure 29 Gateway between frame relay network and VPN network
