Distributed Universal Number Discovery (DUNDi) is a peer-to-peer system for translating phone numbers and internal extensions to voice over IP (VoIP) addresses. DUNDi provides directory services that may be accessed by VoIP protocols like Session Initiation Protocol (SIP) and H.323 to help route calls from their initiators to their proper recipients.
Each DUNDi client has a database that contains its own extension number, at a minimum, but usually contains other extension numbers. A client can populate its database by requesting extensions from other clients, which may be remote. When a client within the path responds with the extension, the requesting client stores the information in its database. Each client must be aware of at least one other DUNDi client, and one of the peers must know how to reach the desired extension or number. DUNDi facilitates the dynamic lookup of extension numbers but does not place the call.
DUNDi was originally developed for use on the public switched telephone network (PSTN). It is now used most often on private networks that employ an Asterisk PBX system to ease administration of extension numbers. It is essentially a peer-to-peer protocol for sharing and propagating extension numbers and related information.