when the end stations are on-hook. NON-ATM network VoATM addressing ATM standards support private and public addressing schemes. Both schemes involve addresses that are 20 bytes in length (shown in Figure 3.2-2). The Authority and Format Identifier (AFI) identifies network the particular addressing format employed. Three iden- tifiers are currently specified: data country code (DCC), non-ATM for voice signaling international code designator (ICD), and E.164. A stan- dard body administers each one. The second part of the NON-ATM address is the initial domain identifier (IDI). This ad- network dress uniquely identifies the customer's network. The E.164 scheme has a longer IDI that corresponds to the 15-digit ISDN network number. The final portion, the domain-specific part (DSP), identifies logical groupings and ATM end stations. In a transport model, you don't need to be aware of the underlying addressing used by the voice network. Telephone However, in the translate model, the capability to com- municate from a non-ATM network device to an ATM Figure 3.2-1 The VoATM signaling transport model describes the transport method, in which voice signaling is carried through network device implies a level of address mapping. For- the network transparently. tunately, ATM supports the E.164 addressing scheme that is employed by telephone networks throughout the world. VoATM signaling VoATM routing Figure 3.2-1 describes the transport method in which voice signaling is carried through the network trans- ATM uses a private network-to-network interface parently. PVCs are created for both signaling and voice (PNNI), a hierarchical link-state routing protocol that is transport. First, a signaling message is carried trans- scalable for global usage. In addition to determining parently over the signaling PVC from end station to end reachability and routing within an ATM network, it is also station. Second, coordination between the end systems capable of call setup. allows the selection of a PVC to carry the voice com- A virtual cir