Federated VoIP is a form of packetized voice telephony that uses voice over IP between autonomous domains in the public Internet without the deployment of central virtual exchange points or switching centers for traffic routing.
Federated VoIP uses decentralized addressing systems, such as ENUM, for location and identity information of participants and implements secure, trusted communications (TLS) for identify verification.
Early Voice over IP deployments have copied this model, sending phone calls over SIP Trunking (a virtual equivalent of ISDN) to an Internet telephony service provider (ITSP) (a virtual telephone exchange).
Such paradigms have striven to emulate many of the aspects of traditional telephony, such as the telephone number.
Although the use of virtual exchanges (soft-switches) and ITSPs has reduced the cost of telephony, they have retained many constraints of traditional telephone systems.