Patent ID: 6873849

Claim:
A method in a telecommunications system, the telecommunications system comprising at least a call originating network and at least a call destination classical network with ported subscribers, the method providing a number portability service in origin for calls to ported subscribers at the destination classical network, beginning with the step of: a) Issuing a DNS-query from the call control entity of the call originating network toward a hierarchical DNS structure in order to resolve addressing for the ported called subscriber, the method characterized in that it further comprises the steps of: b) Receiving at said call control entity from the hierarchical DNS structure addressing data including: an indicator of inter-working with a external database containing ported called subscriber data; a first parameter indicating the Global Title address of the external database that must be further inquired; and a second parameter indicating the protocol required for accessing said external database; c) Inquiring said external database about routing data for the ported called subscriber, said external database being addressed by the Global Title indicated in said first parameter at step (b), and said external database being accessed by the protocol indicated in said second parameter at step (b), both first and second parameters included in previous DNS answer; and d) Mapping the ported called subscriber routing data received from the external database to an appropriate DNS answer indicating routing of an originating call, for further determining the appropriate gateway to proceed with the call toward the called subscriber at a classical network.