Patent ID: 8838771

Claim:
A method of supporting Voice Over Internet Protocol (VoIP) calls on a first network, said method being performed in a device addressable by a first IP address, said method comprising: detecting, in said device addressable by said first IP address, an access information of a first terminal from a registration request generated by said first terminal and directed to a call server, wherein said call server is addressable by a second IP address, and wherein said registration request has a destination address equaling said second IP address, wherein said access information specifies a third IP address of said first terminal such that said first terminal can be accessed on said first network using said third IP address in a destination field of corresponding packets; storing said access information of said first terminal in a memory, said access information specifying that said first terminal is addressable by said third IP address; determining whether said call server is unavailable; receiving a call setup request with a destination address equaling said second IP address such that said call setup request is directed to said call server, wherein said call setup request is from a second terminal and requests said access information of said first terminal, wherein said call server is provided external to said device; forwarding said call setup request to said call server if said call server is determined to be available; if said call server is determined to be unavailable: retrieving said access information from said memory upon receiving of said call setup request; and sending said access information retrieved from said memory to said second terminal, whereby said second terminal communicates with said first terminal by using said third IP address contained in the received access information, thereby establishing a call between said second terminal and said first terminal using said retrieved access information whereby said first terminal is required to register only with said call server, and whereby said second terminal is required to direct call setup requests to only said call server to establish calls with said first terminal even if said call server is unavailable.