Method and system for support of overlapping IP addresses between an interworking function and a mobile IP foreign agent

A method for identifying two different mobile nodes that are connected to the same visited data network and have overlapping home (IP) addresses, comprising the steps of:

• providing to said visited data network, for each mobile node, a mobile node address identifier (Network Address Identifier or NAI) that uniquely identifies one of said mobile nodes across said visited data network;
• storing said NAIs in a Mobile Identity lookup table associated with an Interworking Function communicating with said mobile nodes and in a Visitor List lookup table associated with a Foreign Agent routing entity providing network access to said mobile nodes;
• creating composite data packets each of which includes one of said NAIs bound to a data packet whose origin or destination is one of said mobile nodes which corresponds to said bound NAI;
• exchanging said composite packets between said Interworking Function and said Foreign Agent for both forward Mobile IP traffic and reverse Mobile IP traffic;
• extracting said NAIs from said composite packets at said Foreign Agent for said composite packets moving in the reverse Mobile IP traffic direction, and at said Interworking Function for said composite packets moving in the forward Mobile IP traffic direction;
• and
• using one of said extracted NAIs to identify a unique route to either a Home Agent corresponding to the mobile node associated with said NAI for reverse Mobile IP traffic or the mobile node associated with said NAI for forward Mobile IP traffic.

A system for identifying two different mobile nodes that are connected to the same visited data network and have overlapping home (IP) addresses, comprising:

• a mobile node address identifier (Network Address Identifier or NAI) that is provided for each of said mobile nodes and that uniquely identifies one of said mobile nodes across said visited data network;
• means for storing said NAIs in a Mobile Identity lookup table associated with an Interworking Function communicating with said mobile nodes and in a Visitor List lookup table associated with a Foreign Agent routing entity providing network access to said mobile nodes;
• composite data packets, each of which includes one of said NAIs bound to a data packet whose origin or destination is one of said mobile nodes which corresponds to said bound NAI;
• means for exchanging said composite packets between said Interworking Function and said Foreign Agent for both forward Mobile IP traffic and reverse Mobile IP traffic;
• means for extracting said NAIs from said composite packets at said Foreign Agent for said composite packets moving in the reverse Mobile IP traffic direction, and at said Interworking Function for said composite packets moving in the forward Mobile IP traffic direction;
• and
• means for using one of said extracted NAIs to identify a unique route to either a Home Agent corresponding to the mobile node associated with said NAI for reverse Mobile IP traffic or the mobile node associated with said NAI for forward Mobile IP traffic.

In a visited wireless data network wherein data packets are sent in both directions over a communications pathway that includes, in succession, a visiting mobile wireless node, a Radio Access Network (RAN), an Interworking Function (IWF), and a Foreign Agent routing entity, routing said data packets between said visiting mobile wireless node and a Home Agent routing entity in said visiting mobile wireless node's home data network, a method for correctly routing said data packets by distinguishing between said visiting mobile node and another mobile node in said visited wireless data network having the same home address as said visiting mobile wireless node, comprising the steps of:

• acquiring, for each mobile node registered on said visited wireless data network, a mobile node identifier (Network Address Identifier or NAI) uniquely identifying one of said registered mobile nodes by performing a CHAP protocol during PPP establishment under Basic Mobile IP or by sending a registration message under Enhanced Mobile IP;
• storing said NAI, along with a home (IP) address and a link identifier that correspond to a mobile node identified by said NAI in a Mobile Identity table associated with said IWF during the CHAP or registration phase of Mobile IP service, wherein each entry in said Mobile Identity table contains a unique combination of said NAI and said home address of said mobile node;
• storing said NAI, along with a home (IP) address and a Home Agent IP address that correspond to a mobile node identified by said NAI, in a Visitor List table associated with said Foreign Agent during the registration phase of Mobile IP service, wherein each entry in said Visitor List table contains a unique combination of said mobile node home address and said Home Agent IP address;
• retrieving, when reverse Mobile IP traffic arrives at said IWF, one of said stored NAIs by using a link identifier from said mobile node and a home address contained in said data packet's header, either in combination in a single lookup or successively in two lookups in said Mobile Identity table;
• retrieving, when forward Mobile IP traffic arrives at said Foreign Agent, one of said stored NAIs by using home addresses of said mobile node and said Home Agent, either in combination in a single lookup or successively in two lookups in said Visitor List table;
• appending said retrieved NAI to data packets exchanged between said IWF and said Foreign Agent, thereby creating composite packets;
• extracting said NAI from said composite packets upon receipt thereof at said IWF and said Foreign Agent;
• determining said Home Agent's IP address when reverse Mobile IP traffic arrives at said Foreign Agent by using said extracted NAI and said mobile node's home address either in combination in a single lookup or successively in two lookups in said Visitor List table;
• determining said mobile node's link identifier when forward Mobile IP traffic arrives at said IWF by using said extracted NAI in a lookup in said Mobile Identity table;
• and
• routing each of said data packets to a correct destination at said Home Agent by using said Home Agent IP address or at said mobile node by using said mobile node's link identifier.