Every member knows how to communicate with the other members, and within the group a peer-group leader knows how to correspond with the level above. PNNI can be scaled effectively no matter how many switches are on your network, but it requires careful planning. Instead of tunneling Layer 3 over ATM, it adds router-type functionality to the concentrator to determine the path to an endpoint for the packet and sends it on its way. LANE and MPOA are helpful additions to an ATM network because they provide expected IP services. Despite all the talk of converging on ATM, frame relay is not dead.
Many networks are still firmly entrenched in the technology.
If your network is among them, you'll need to decide what to do with frame relay and choose a concentrator that supports your decision. If you'll be running voice on your ATM backbone, the first thing to look for in a concentrator is the voice-interface modules. Digitized voice can be compressed using various methods. There are several standards for voice compression, and all are subjective. If your network is carrying interoffice voice traffic where quality is less of a concern than bandwidth, high compression can be used.