Method for inter-IP-domain roaming across wireless networks

• US 6,473,413 B1
• Filed: 06/22/1999
• Issued: 10/29/2002
• Est. Priority Date: 06/22/1999
• Status: Expired due to Term

• Current Assignee: Institute For Information Industry
• Original Assignee: Institute For Information Industry
• Inventors: You, Ming-Young, Chiou, Jiann-Ching, Leu, Yuh-Rong
• Primary Examiner(s): Ngo, Ricky
• Assistant Examiner(s): Phan, Tri H.
• Application Number:
  US09/338,291
• Time in Patent Office: 1,225 Days
• Field of Search: 370/352, 370/331, 370/338, 370/401, 370/475, 370/328, 370/277, 370/310, 370/389, 370/392, 370/353, 370/356, 370/400, 709/227, 709/228, 455/432, 455/433, 455/434, 455/435, 455/436, 455/437, 455/438, 455/439, 455/442, 455/445, 455/422
• US Class Current: 370/331
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04W 36/0019 adapted for mobile IP [MIP]
• CPC Class Codes: H04W 36/12 Reselecting a serving backbone network switching or routing node
• CPC Class Codes: H04W 4/18 Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
• CPC Class Codes: H04W 40/36 due to handover
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 88/08 Access point devices
• CPC Class Codes: H04W 92/20 between access points

Abstract

A method involves in integrating the communication mechanisms of IAPP and mobile IP is provided for allowing a mobile station to roam among various APs in different IP subnets. When a mobile station roams to a new IP subnet, it will issue a reassociation request to an Access Point A in the new IP subnet. In response to the reassociation request, the Access Point A will need the IP address of the previous Access Point B in the previous IP subnet to send the handoff request to the Access Point B. So, the Access Point A can find the IP address of the Access Point B via the communication mechanism of mobile IP of IP layer and then send the handoff request frame to the Access Point B. In turn, upon receiving the handoff request frame, the Access Point B deletes the record of the mobile station in the association table and then sends the handoff response frame back to the Access Point A via the communication mechanism of mobile IR. The unicast handoff response frame will be forwarded to the Access Point A. Consequently, the Access Point A can complete the handoff procedure.

Claims

1. A method for routing datagrams across wireless networks, said wireless networks comprising a plurality of wireless LANs each located in a unique IP subnet, comprising the steps of:

providing a Home Agent and a Home Access Point for a mobile station at its initial wireless LAN;

providing a first Foreign Agent and a first Access Point for said mobile station at a first destination wireless LAN;

receiving a reassociation request frame from said mobile station when said mobile station roams directly from said initial wireless LAN to said first destination wireless LAN;

sending a handoff request frame from said first Access Point to said first Foreign Agent after finishing a reassociation procedure;

using the MAC address of said mobile station to lookup the IP address of said Home Agent in the registration table of said first Foreign Agent when said mobile station has successfully registered to said first Foreign Agent;

establishing a proxy IAPP table in said first Foreign Agent for said mobile station, said proxy IAPP table comprising the MAC address of said mobile station, and the source IP address of said handoff request frame;

forwarding said handoff request frame to said Home Agent according to said IP address of said Home Agent found in said registration table;

looking up the IP address of last Foreign Agent for said mobile station in said registration table of said Home Agent;

when said IP address of the last Foreign Agent is found, forwarding said handoff request frame to said last Foreign Agent;

when said IP address of said last Foreign Agent is not found, determining said last Foreign Agent being the same as said Home Agent;

looking up association table and when said MAC address of said mobile station is not in said association table, broadcasting said handoff request frame in said initial wireless LAN;

deleting a record of said mobile station from an association table of said Home Access Point, and then sending a unicast handoff response frame from said Home Access Point to said Home Agent in response to said broadcast handoff request frame;

sending a unicast handoff response frame from said Home Agent to said first Foreign Agent according to a source IP address recorded in said proxy IAPP table of said Home Agent;

sending said unicast handoff response frame from said first Foreign Agent to said first Access Point according to said source IP address recorded in said proxy IAPP table of said first Foreign Agent; and

deleting a record from the handoff list of said first Access Point when said mobile station has ever sent a handoff request frame, thereby to complete a handoff request procedure.

2. The method as claimed in claim 1, further comprising the steps of:

providing a second Foreign Agent and a second Access Point for said mobile station at a second destination wireless LAN;

when said mobile station roams directly from said first destination wireless LAN to said second destination wireless LAN, said second Access Point looking up its AP table and determining said first Access Point not existing in said AP table;

broadcasting said handoff request frame from said second Access Point to said second Foreign Agent;

using the MAC address of said mobile station to lookup the IP address of said Home Agent of said mobile station in the registration table of said second Foreign Agent when said mobile station has successfully registered to said second Foreign Agent;

establishing a proxy IAPP table in said second Foreign Agent for said mobile station, said proxy IAPP table comprising the MAC address of said mobile station, and the source IP address of said handoff request frame;

forwarding said handoff request frame to said Home Agent according to said IP address of said Home Agent found in said registration table;

looking up the registration table of said Home Agent to find the IP address of the Last Foreign Agent;

establishing a proxy IAPP table for said Home Agent, said proxy IAPP table comprising said MAC address of said mobile station, and the source IP address of said handoff request frame;

sending a unicast handoff request frame to said first Foreign Agent according to said IP address of the Last Foreign Agent of said mobile station recorded in said registration table of said Home Agent;

said first Foreign Agent looking up its association table and broadcasting said handoff request frame in said first destination wireless LAN when determining said MAC address of said mobile station not existing in said association table;

deleting a record of said mobile station from an association table of said first Access Point and then sending a unicast handoff response frame from said Home Access Point to said first Foreign Agent in response to said broadcast handoff request frame;

forwarding said unicast handoff response frame from said first Foreign Agent to said Home Agent according to said IP address of the Home Agent recorded in said proxy IAPP table of said first Foreign Agent;

forwarding said unicast handoff response frame from said Home Agent to said second Foreign Agent according to the IP address of the second Foreign Agent recorded in said proxy IAPP table of said Home Agent;

sending said unicast handoff response frame from said second Foreign Agent to said second Access Point according to said source IP recorded in said proxy IAPP table of said first Foreign Agent; and

deleting a record from said handoff list of said first Access Point when said mobile station has ever sent a handoff request frame, thereby to complete a handoff request procedure.

3. The method as claimed in claim 1, further comprising the steps of:

when said mobile station roaming directly from said second destination wireless LAN to said initial wireless LAN, looking up said AP table of said Home Access Point and determining the record of said second Access Point not existing in said AP table after a reassociation procedure being complete,

broadcasting a handoff request frame from said Home Access Point to said Home Agent;

using the MAC address of said mobile station to lookup the IP address of said Last Foreign Agent in the registration table of said Home Agent when said mobile station has successfully registered to said Home Agent;

forwarding said handoff request frame from said Home Agent to said second Foreign Agent according to said IP address of said Last Foreign Agent of said mobile station found in said registration table of said Home Agent;

establishing a proxy IAPP table for said mobile station in said Home Agent and said proxy IAPP table comprising said MAC address of said mobile station, and a source IP address of said handoff request frame,

broadcasting said handoff request frame in said second destination wireless LAN when the MAC address of said mobile station not recorded in the association table of said second Foreign Agent;

deleting the record of said mobile station in said association table of said second Access Point in response to said handoff request frame and sending a unicast handoff response frame to said second Foreign Agent;

sending a unicast handoff response frame from said second Foreign Agent to said Home Agent according to a source address recorded in said proxy IAPP table of said second Foreign Agent;

sending said unicast handoff response frame from said Home Agent to said Home Access Point according to said destination IP address of said handoff response frame recorded in said proxy IAPP table of said Home Agent; and

deleting a record from said handoff list of said first Access Point when said mobile station has ever sent a handoff request frame, thereby to complete a handoff request procedure.

4. The method as claimed in claim 1, wherein said Home Agent communicates with network layer protocols, and said Home Access Point communicates with MAC layer protocols.

5. The method as claimed in claim 1, wherein said first Foreign Agent communicates with network layer protocols, and said Home Access Point communicates with MAC layer protocols.

6. The method as claimed in claim 2, wherein said second Foreign Agent communicates with network layer protocols, and said second Access Point communicates with MAC layer protocols.

7. The method as claimed in claim 1, wherein said Home Access Point comprising an AP table, an association table and a handoff list.

8. The method as claimed in claim 1, wherein said first Foreign Agent comprising a registration table, said registration table comprising a MAC address of a mobile station, and the IP address of the Home Agent of the corresponding mobile station.

9. The method as claimed in claim 1, wherein said Home Agent comprising a registration table, and said registration table comprising a MAC address of a mobile station, an IP address of a Last Foreign Agent for said mobile station, and an IP address of a current Foreign Agent of a current wireless LAN.

10. The method as claimed in claim 2, wherein said second Foreign Agent comprises a registration table, and said registration table comprising a MAC address of a mobile station, and the IP address of the Home Agent of the corresponding mobile station.

11. The method as claimed in claim 1, wherein said Home Agent and said first Foreign Agent follows mobile IP communication mechanism.

12. The method as claimed in claim 2, wherein said second Foreign Agent follows mobile IP communication mechanism.

13. The method as claimed in claim 1, wherein said Home Access Point and said Home Access Point follows Inter Access Point Protocol communication mechanism.

14. The method as claimed in claim 2, wherein said second Access Point follows Inter Access Point Protocol communication mechanism.