Geographically adjacent access router discovery and caching for mobile nodes

• US 20030087646A1
• Filed: 06/27/2002
• Published: 05/08/2003
• Est. Priority Date: 11/02/2001
• Status: Active Grant

• Current Assignee: Godo Kaisha IP Bridge 1 (IP Bridge, Inc.)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Williams, Carl, Takeshita, Atsushi, Funato, Daichi
• Granted Patent: US 7,545,754 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: H04L 12/2854 Wide area networks, e.g. public data networks
• CPC Class Codes: H04W 40/20 based on geographic position or location
• CPC Class Codes: H04W 40/246 Connectivity information discovery
• CPC Class Codes: H04W 40/30 for proactive routing
• CPC Class Codes: H04W 40/36 due to handover
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]

Abstract

A geographically adjacent access router discovery system discovers geographically adjacent access routers through a distributed process in which mobile node(s) associated with a current access router may receive beacon signals from geographically adjacent access points. A link layer ID included in the beacon signals may be used by the system to identify corresponding geographically adjacent access routers. Network layer addresses of geographically adjacent access routers may be mapped to corresponding link layer IDs and, cached by the system. The cache may be used to identify a network layer address from the link layer ID received in a beacon signal.

Claims

1. A method of discovering geographically adjacent access routers, the method comprising:

a) receiving a link layer ID of a geographically adjacent access point with a mobile node; and

b) identifying a network layer address of a geographically adjacent access router with the link layer ID, wherein the geographically adjacent access router is associated with the geographically adjacent access point.

2. The method of claim 1, wherein a) comprises entering the cell coverage area of the geographically adjacent access point.

3. The method of claim 1, further comprising the initial act of caching a mapped association of the link layer ID to the network layer address.

4. The method of claim 1, wherein b) comprises accessing a cache that includes a mapped association of the link layer ID to the network layer address.

5. The method of claim 1, wherein b) further comprises requesting the network layer address from an access router, wherein the access router provides the current point of attachment of the mobile node.

6. The method of claim 5, wherein b) comprises discovering the network layer address with the access router.

7. The method of claim 1, further comprising c) preparing for a handoff of the mobile node with the network layer address of the geographically adjacent access router, wherein the mobile node and an access router that provides the current point of attachment of the mobile node prepare for the handoff with network layer address.

8. A method of discovering geographically adjacent access routers, the method comprising:

a) receiving a link layer ID of a geographically adjacent access point from a mobile node;

b) identifying a network layer address of a geographically adjacent access router from the link layer ID, wherein the geographically adjacent access router is associated with the geographically adjacent access point;

c) caching a mapped association of the link layer ID to the network layer address; and

d) providing the mapped association to the mobile node.

9. The method of claim 8, wherein a) comprises generating a solicitation message with the mobile node that includes the link layer ID in response to receipt of a beacon signal that includes the link layer ID from the geographically adjacent access point.

10. The method of claim 8, wherein b) comprises querying a directory server with the link layer ID to identify the network layer address as a function of the link layer ID.

11. The method of claim 8, wherein b) comprises multicasting a service request message to a multicast group that includes the geographically adjacent access router to identify the network layer address, wherein the service request message includes the link layer ID.

12. The method of claim 8, wherein d) comprises transmitting the network layer address of the geographically adjacent access router to the mobile node with an advertisement message that includes the link layer ID.

13. The method of claim 8, further comprising e) preparing for a handoff of the mobile node to the geographically adjacent access router as a function of the network layer address, wherein the mobile node and an access router providing a current point of attachment of the mobile node prepare for the handoff.

14. A method of discovering geographically adjacent access routers, the method comprising:

a) providing a point of attachment to a mobile node with an access router;

b) downloading a cache from the access router to the mobile node, the cache including a plurality of link layer IDs each associated with at least one network layer address, wherein the at least one network layer address identifies a geographically adjacent access router;

c) receiving a beacon signal with the mobile node from a geographically adjacent access point, wherein the beacon signal includes a link layer ID of the geographically adjacent access point;

d) identifying a network layer address of a geographically adjacent access router associated with the geographically adjacent access point with the mobile node when the link layer ID is included in the downloaded cache; and

e) requesting identification of the network layer address from the access router when the link layer ID of the geographically adjacent access point is absent from the downloaded cache.

15. The method of claim 14, wherein e) comprises transmitting a solicitation message to the access router that includes the link layer ID.

16. The method of claim 14, further comprising f) the mobile node and the access router preparing for a handoff of the mobile node to the geographically adjacent access router with the network layer address.

17. The method of claim 14, further comprising f) transmitting the identified network layer address to the mobile node in an advertisement message.

18. The method of claim 14, wherein e) comprises querying a directory server with the access router to identify the network layer address as a function of the link layer ID.

19. The method of claim 14, wherein e) comprises multicasting a service request message to a multicast group that includes the geographically adjacent access router to identify the network layer address as a function of the link layer ID.

20. The method of claim 14, wherein e) comprises accessing the cache within the access router to identify the network layer address as a function of the link layer ID.

21. The method of claim 14, wherein logical adjacency of the access router and the geographically adjacent access router is created by the association of the link layer IDs with the at least one network layer address.

22. A system for discovering geographically adjacent access routers, the system comprising:

an access router in communication with the mobile node, wherein the access router is operable to download a cache to the mobile node, the cache comprising a plurality of link layer IDs each associated with at least one network layer address;

a geographically adjacent access point in communication with the mobile node, the geographically adjacent access point operable to transmit a link layer ID to the mobile node; and

a geographically adjacent access router in communication with the geographically adjacent access point, wherein the geographically adjacent access router is identified by a network layer address,

wherein the mobile node is operable to identify the network layer address of the geographically adjacent access router as a function of the link layer ID of the geographically adjacent access point when the link layer ID is included in the cache, and

the mobile node is operable to request identification of the network layer address from the access router when the cache does not include the link layer ID of the geographically adjacent access point.

23. The system of claim 22, further comprising a directory server, wherein the access router is operable to query the directory server for the network layer address as a function of the link layer ID.

24. The system of claim 22, wherein the access router is operable to multicast a service request to a multicast group that includes the geographically adjacent access router to identify the network layer address as a function of the link layer ID.

25. The system of claim 22, wherein the request for identification of the network layer address is a solicitation message, the solicitation message included in an IP protocol.

26. The system of claim 22, wherein the response to the request for identification of the network layer address is an advertisement message, the advertisement message included in an IP protocol.

27. The system of claim 22, wherein the mobile node comprises a GAARD mobile component and a local GAARD cache component, wherein the local GAARD cache component includes a local cache in which mapped associations of link layer ]Ds and network layer addresses are cached.

28. The system of claim 22, wherein the access router comprises a GAARD cache component, a GAAR discovery component and a GAARD cache distribution component, wherein the GAARD cache component includes a cache in which mapped associations of link layer IDs and network layer addresses are cached.

29. The system of claim 28, wherein the GAAR discovery component is operable to resolve the network layer address of geographically adjacent access routers for which mapped associations are absent from the cache.

30. A system for discovering geographically adjacent access routers, the system comprising:

a mobile node;

a first access router operable to provide a current point of attachment for the mobile node;

a second access router geographically adjacent to the first access router, wherein the first access router is unaware of the geographic adjacency of the second access router; and

a geographically adjacent access point associated with the second router, wherein the geographically adjacent access point is operable to transmit a link layer ID of the geographically adjacent access point to the mobile node,

wherein at least one of the mobile node and the first access router are operable to resolve a network layer address of the second access router from the link layer ID.