Patent ID: 7085813

Claim:
A method for synchronizing user registration information in an interdomain having User Agents (UAs) corresponding to leaf nodes of a tree structure and functioning as entities for substituting for users, and Session Initiation Protocol (SIP) servers/registrars corresponding to a root node or intermediate nodes of the tree structure, comprising the steps of: registering current position information of a random user through a register message when the user moves from one User Agent (UA) to another; transmitting a up-sync message upstream of a tree structure and a down-sync message downstream of the tree structure when user registration information is created or changed; performing synchronization of the user registration information in upper and lower SIP servers/registrars having received the up-sync and down-sync messages, respectively. changing registrar information whenever a random user registers his current position information through a register message; comparing a “To” address of the register message with a “To” address of a registrar in a random SIP server having received the register message; if a record corresponding to the “To” address of the register message is not present in the registrar, creating a new record and storing the “To” address and the contact address of the register message in the record; if the record corresponding to the “To” address of the register message is present in the registrar and the contact address of the registrar is not identical to the contact address of the register message, changing the contact address of the registrar into the contact address of the register message; if the record corresponding to the “To” address of the is register message has been created or changed, determining whether register is requested from the same domain, and determining whether the record corresponding to the “To” address of the register message has been created or changed if register is requested from the same domain; if the record corresponding to the “To” address of the register message has been created or changed, determining whether an upper SIP address and an upper registrar are present, and requesting addition of newly created information or the change of information to the latest information by transmitting the up-sync message upstream if the upper SIP address and the upper registrar are present; and if the record corresponding to the “To” address of the register message has been changed, determining whether a lower SIP address and a lower registrar are present and their type is a server, and requesting deletion of information due to the change of previous information by transmitting the up-sync message upstream if the lower SIP address and the lower registrar are present and their type is a server.