It looks like the days of operating multiple networks for various services may be coming to an end. Granted, we've all heard about network convergence before. Meanwhile, most carriers continue to operate separate networks for voice and various flavors of data.
Overlay networks are expensive to build from scratch.
Many competitive carriers began their expansion of data services by offering IP services. In anticipation of an expected deluge of IP traffic into the network, carriers have ramped up investments in IP networks. Supplementing IP with other services will accelerate the payback. For example, offering frame relay service over IP represents a significant opportunity. The optical Internet is being embraced by virtually all large communication carriers.