Patent ID: 8032638

Claim:
A calling method for use by a first endpoint within a first zone to initiate calls across zones in an Internet Protocol (IP) network system, comprising: Sending, at the first endpoint, a prefixed alias of a second endpoint within a second zone to a second gatekeeper of the second zone via a first gatekeeper of the first zone; the prefixed alias of the second endpoint comprising a combination of a unique alias within the second zone and a prefix identifying the second gatekeeper in the IP network system, and the first gatekeeper being configured to receive the prefixed alias of the second endpoint from the first endpoint of the first zone, locate the second gatekeeper according to the prefix and send the prefixed alias of the second endpoint to the second gatekeeper; receiving, at the first endpoint, an address of the second endpoint from the second gatekeeper through the first gatekeeper; the second gatekeeper being configured to receive the prefixed alias from the first gatekeeper, obtain the address of the second endpoint according to the prefixed alias, and send the address of the second endpoint to the first gatekeeper; the first gatekeeper being further configured to send the address of the second endpoint to the first endpoint; wherein the address of the second endpoint obtained by the second gatekeeper according to the prefixed alias is an IP address of the second endpoint; and initiating a call directly to the second endpoint using the address of the second endpoint.