more extensions than really are connected, so it is no guarantee the extension can be reached. In order to prevent the network from overloading and at the same time keep the responses as quick as possible, the involved peers will cache the lookups they see. Because the used keys may become invalid after some period, each lookup has some expiry date. This defaults to one hour. When no context is given with a lookup, DUNDi defaults to the E.164 context. This means you are looking for normal (international) phone-numbers, like 0031201234567 (some bogus number in Amsterdam, The Netherlands) In order to do so, you have to peer with at least one other peer in the E164 trust group. The peers in this group are bound to the Digium GPA (Digium General Peering Agreement) (PDF) External links DUNDi Home Page Internet-Draft that expired in 2005 VoIP and ENUM Telephone numbers Network protocols VoIP protocols