Apparatus of dynamically assigning external home agent for mobile virtual private networks and method for the same

A method of dynamically assigning external home agent (x-HA) for mobile Virtual Private Networks (VPNs), the method establishing VPN between at least one external network and an internal network and enabling at least mobile node (MN) roam in the external networks with security, the method comprising the steps of:

• the MN sending a Registration Request (Reg-Req) message to an external foreign agent (x-FA) when the MN roams to the external network for the first time, wherein the Reg-Req message comprises fields including an external home address (x-HoA) request, and an external home agent (x-HA) address request;
• the x-FA sending an AA-Mobile-Node-Request (AMR) message to a foreign AAA (AAAF) server, the AAAF server filling the Network Access Identifier (NAI) of a candidate x-HA in AMR message and sending the AMR message to a home AAA (AAAH) server;
• the AAAH server establishing security associations (SAs) among the candidate x-HA, the x-FA and the MN and generating a Home-Agent-MIP-Request (HAR) message for sending to the x-HA;
• the x-HA allocating an external home address (x-HoA) for the MN and filling the x-HoA and its address thereof in the Home-Agent-MIP-Answer (HAA) message, the x-HA then sending the HAA message to the AAAH server;
• the AAAH sever using the pre-configured VPN-TIA as the internal CoA of the MN for registration to the i-HA, the i-HA authorizing the AAAH server to send an AA-Mobile-Node-Answer (AMA) message to the x-FA;
• and
• the x-FA obtaining a Reg-Reply message from the AMA message and containing x-HoA and HA address;
• and sending the Reg-Reply message to the MN;
• when the MN roams in the external network, the MN uses the x-HoA for registration to the assigned x-HA with the x-HA address.