Methods and apparatus for synchronizing subnet mapping tables

• US 7,362,742 B1
• Filed: 01/28/2003
• Issued: 04/22/2008
• Est. Priority Date: 01/28/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Yu, Tai Y., Siddiqi, Waseem A., Thippeswamy, Arunkumar B.
• Primary Examiner(s): Yao; Kwang Bin
• Assistant Examiner(s): Tran; Tung Q.
• Application Number:
  US10/354,690
• Time in Patent Office: 1,911 Days
• Field of Search: 370/328, 370/350, 370/395.31
• US Class Current: 370/350
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04W 24/04 Arrangements for maintaining operational condition
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 88/005 Data network PoA devices
• CPC Class Codes: H04W 88/182 Network node acting on behalf of an other network entity, e.g. proxy

Abstract

Methods and apparatus for enabling mobility of a node that does not support Mobile IP through synchronization of access point information (e.g., subnet mapping tables) among AAPs are disclosed. In accordance with one embodiment, an authoritative access point (AAP) maintains access point information for all functioning access points (APs) and sends updates for all additions or other modifications to the continually changing access point information to other AAPs. This is accomplished by sending a copy of its local subnet mapping table to the other AAPs. The AAPs receiving the subnet mapping table then update their subnet mapping tables corresponding to the received subnet mapping table.

Claims

1. In a first authoritative access point, a method of synchronizing two or more subnet mapping tables maintained by two or more authoritative access points, comprising:

receiving one or more subnet mapping tables from one or more authoritative access points; and

updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points; and

determining whether information in the received subnet mapping table is current;

wherein updating is performed such that the first subnet mapping table includes the information from the received subnet mapping table that is determined to be current.

2. The method as recited in claim 1, further comprising:

notifying one or more additional authoritative access points to update their corresponding subnet mapping table corresponding to the updates performed on the first subnet mapping table.

3. The method as recited in claim 1, wherein receiving one or more subnet mapping tables is performed in response to a SYNC message sent by the first authoritative access point to the one or more authoritative access points.

4. The method as recited in claim 1, wherein updating comprises:

attempting to add an entry in the received subnet mapping table to the first subnet mapping table.

5. The method as recited in claim 1, wherein updating comprises:

adding an entry in the received subnet mapping table to the first subnet mapping table.

6. The method as recited in claim 1, wherein updating comprises:

determining whether an access point identified in an entry in the received subnet mapping table is alive;

when it is determined that the access point identified in the entry in the received subnet mapping table is alive, updating the first subnet mapping table such that the first subnet mapping table includes an IP address associated with the access point; and

when it is determined that the access point identified in the entry in the received subnet mapping table is not alive, updating the first subnet mapping table such that the first subnet mapping table does not include the IP address associated with the access point.

7. The method as recited in claim 1, further comprising:

determining whether an access point identified in an entry in the received subnet mapping table is alive;

when it is determined that the access point identified in the entry in the received subnet mapping table is alive, sending an ADD message to one or more additional authoritative access points indicating that the IP address should be added to their corresponding subnet mapping tables; and

when it is determined that the access point identified in the entry in the received subnet mapping table is not alive, sending a REMOVE message to one or more additional authoritative access points indicating that the IP address should be removed from their corresponding subnet mapping tables.

8. The method as recited in claim 6, further comprising:

when it is determined that the access point identified in the entry in the received subnet mapping table is not alive, determining whether a Home Agent identified in the entry is alive.

9. The method as recited in claim 1, further comprising:

determining whether a Home Agent identified in an entry in the received subnet mapping table is alive;

when it is determined that the Home Agent identified in the entry is not alive, updating the first subnet mapping table such that the first subnet mapping table does not include an entry associated with the Home Agent; and

when it is determined that the Home Agent identified in the entry is alive, updating the first subnet mapping table such that the first subnet mapping table includes an entry associated with the Home Agent.

10. The method as recited in claim 1, further comprising:

determining whether a Home Agent identified in an entry in the received subnet mapping table is alive;

when it is determined that the Home Agent identified in the entry is not alive, sending a REMOVE message to one or more additional authoritative access points to remove an entry associated with the Home Agent from their corresponding subnet mapping table.

11. The method as recited in claim 1, further comprising:

determining whether a Home Agent identified in an entry in the received subnet mapping table is alive;

when it is determined that the Home Agent identified in the entry is not alive, sending a REMOVE message to one or more additional authoritative access points to remove an entry associated with the Home Agent from their corresponding subnet mapping table.

12. The method as recited in claim 1, wherein each subnet mapping table comprises a plurality of entries, each of the entries including a Home Agent address, subnet mask, and one or more IP addresses of one or more Access Points that the Home Agent supports.

13. The method as recited in claim 12, wherein each of the plurality of entries further indicates a number of Access Points that the Home Agent supports.

14. The method as recited in claim 13, wherein updating the first subnet mapping table comprises:

removing a Home Agent entry in the first subnet mapping table when the number of Access Points is zero and it is determined that the Home Agent is down.

15. The method as recited in claim 13, further comprising:

decrementing the number of Access Points that the Home Agent supports when an IP address associated with an Access Point is removed from the entry in the first subnet mapping table.

16. The method as recited in claim 1, wherein determining whether information in the received subnet mapping table is current comprises:

querying an Access Point identified in an entry in the received subnet mapping table to determine whether the Access Point is alive.

17. The method as recited in claim 1, wherein determining whether information in the received subnet mapping table is current comprises:

querying a Home Agent identified in an entry in the received subnet mapping table to determine whether the Home Agent is alive.

18. The method as recited in claim 6, wherein determining whether an access point identified in an entry in the received subnet mapping table is alive comprises:

sending an ALIVE packet to the access point identified in the entry; and

receiving an ALIVE ACK packet from the access point that indicates a subnet address and Home Agent address associated with the access point.

19. The method as recited in claim 18, further comprising:

updating an entry in the first subnet mapping table to include the subnet address, Home Agent address, and IP address associated with the access point.

20. The method as recited in claim 19, further comprising:

incrementing the number of access points within the entry of the first subnet mapping table.

26. The method as recited in claim 1, further comprising:

determining whether a Home Agent identified in an entry in the received subnet mapping table is alive;

when it is determined that the Home Agent identified in the entry is not alive, removing an entry associated with the Home Agent from the first subnet mapping table.

21. A computer-readable medium storing thereon computer-readable instructions for synchronizing two or more subnet mapping tables maintained by two or more authoritative access points in a first authoritative access point, comprising:

instructions for receiving one or more subnet mapping tables from one or more authoritative access points; and

instructions for updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points;

determining whether the access points in each of the subnet mapping tables are alive;

wherein updating is performed in accordance with whether the access points in each of the subnet mapping tables are determined to be alive.

22. A first authoritative access point adapted for synchronizing two or more subnet mapping tables maintained by two or more authoritative access points, comprising:

means for receiving one or more subnet mapping tables from one or more authoritative access points; and

means for updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points;

determining whether information in the received subnet mapping table is current;

wherein updating is performed such that the first subnet mapping table includes the information from the received subnet mapping table that is determined to be current.

23. A first authoritative access point adapted for synchronizing two or more subnet mapping tables maintained by two or more authoritative access points, comprising:

a processor; and

a memory, at least one of the processor or the memory being adapted for;

receiving one or more subnet mapping tables from one or more authoritative access points; and

updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points;

determining whether the access points in each of the subnet mapping tables are alive;

wherein updating is performed in accordance with whether the access points in each of the subnet mapping tables are determined to be alive.

24. In a first authoritative access point, a method of synchronizing two or more subnet mapping tables maintained by two or more authoritative access points, comprising:

receiving one or more subnet mapping tables from one or more authoritative access points; and

updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points;

wherein updating is performed such that the first subnet mapping table incorporates at least a portion of the information from the received subnet mapping table.

25. The method as recited in claim 24, wherein each subnet mapping table comprises a plurality of entries, each of the entries including a Home Agent address and one or more IP addresses of one or more Access Points that the Home Agent supports.

27. In a first authoritative access point, a method of synchronizing two or more subnet mapping tables maintained by two or more authoritative access points, comprising:

receiving one or more subnet mapping tables from one or more authoritative access points; and

updating a first subnet mapping table maintained by the first authoritative access point corresponding to the one or more subnet mapping tables received from the one or more authoritative access points;

wherein the first authoritative access point and the one or more authoritative access points each maintains access point information for a plurality of active access points and is responsible for sending information to the plurality of active access points regarding modifications to the access point information;

wherein each of the subnet mapping tables that have been received identifies one or more access points;

determining whether the access points in each of the subnet mapping tables are alive;

wherein updating is performed in accordance with whether the access points in each of the subnet mapping tables are determined to be alive.