Another way to implement a private-networking solution while capitalizing on an ISP's backbone is to create a private-network using frame-relay PVCs. Frame-relay PVC is a technology available to homogeneous frame-relay networks; the ISP must be able to implement the frame relay–networking protocol across its entire network.

A PVC is a way to logically create a separate independent circuit within the same physical circuit. Figure 3 illustrates three separate PVCs within the same physical interface. Each PVC acts logically as a private circuit, similar to a traditional WAN–dedicated circuit.

Figure 3. Subinterface Model

Frame-relay PVCs offer the advantages of high security because sensitive corporate data is not transmitted to the public Internet. Instead it is only transmitted down a customer's own PVC, which remains logically separate from the public Internet. A frame-relay PVC private-network implementation is also not as susceptible to network congestion, as each PVC only carries data for one customer.

Figure 4 illustrates a private network utilizing frame-relay PVCs. No additional encryption devices are necessary. Each branch office or partner company is connected to the homogeneous network of a selected ISP.

Figure 4. Frame-Relay PVC Networking Technology