L2 method for a wireless station to locate and associate with a wireless network in communication with a Mobile IP agent

• US 7,257,105 B2
• Filed: 10/03/2002
• Issued: 08/14/2007
• Est. Priority Date: 10/03/2002
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Molteni, Marco, Lucchina, Massimo G, Thubert, Pascal
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US10/263,632
• Publication Number:
  US 20040066757A1
• Time in Patent Office: 1,776 Days
• Field of Search: 370/328, 370/338, 370/469
• US Class Current: 370/338
• CPC Class Codes: H04L 41/048 mobile agents
• CPC Class Codes: H04L 41/5009 Determining service level performance parameters or violations of service level contracts, e.g. violations of agreed response time or mean time between failures [MTBF]
• CPC Class Codes: H04L 63/029 Firewall traversal, e.g. tunnelling or, creating pinholes
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 8/02 Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A wireless station having a wireless network device capable of providing a link-layer interface to a wireless network, a method operating at the link layer (L2) in the wireless station, and a carrier medium carrying computer readable code segments that when executed on a processor in the wireless station implement the method. The method includes, prior to the station being associated with a wireless network, wirelessly receiving L2 frames transmitted from one or more wireless access point of one or more wireless networks that the station can hear. The method further includes gathering information about the received L2 frames, including L2 information and L3 information. The L3 information includes whether an AP is sending an IP packet from a mobility agent, such that the station may associate with a wireless network that is in communication with the mobility agent. The method further includes storing information about the wireless networks that the station can hear in a database. The information stored about each wireless network includes one or more of an identifier of the wireless network, the L3 information in the L2 frame received from the AP of the wireless network, a time stamp of when the L2 frame was received from the AP, and an indication of the signal strength of the L2 frame from the AP.

Claims

1. In a wireless station having a wireless network device, the device capable of providing a link-layer (L2) interface to a wireless network, a method operating at the link layer (L2) of a multi-layer network protocol, the method comprising:

prior to the station being associated with a wireless network via the wireless network device, wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear; and

gathering information about the received L2 data units, including L2 information and L3 information,

the L3 information gathered at L2 including whether an AP is sending one or more L3 packets from one or more mobility agents,

such that the station may associate with a wireless network that is in communication with a mobility agent.

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

storing information about the wireless networks that the station can hear in a database, including L3 information from the one or more mobility agents.

3. A method as recited in claim 2, wherein the one or more wireless networks whose APs transmit L2 data units conform to one of the IEEE 802.11 standards.

4. A method as recited in claim 2, wherein the information stored about each wireless network includes an identifier of the wireless network, the L3 information in the L2 data unit received from the AP of the wireless network, a time stamp of when the L2 data unit was received from the AP, and an indication of the signal strength of the L2 data unit from the AP.

5. A method as recited in claim 4,

wherein the station includes a plurality of wireless network devices each capable of providing an interface to a wireless network, and

wherein the information stored about each wireless network further includes an indication of which wireless network device received the L2 data unit.

6. A method as recited in claim 4, wherein the information stored about each wireless network includes an indication of any mobility information contained in any L3 information in the received L2 data unit from the AP of the wireless network.

7. A method as recited in claim 4, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.

8. A method as recited in claim 7, further comprising:

periodically updating the database,

wherein the database includes a record for each wireless network, and wherein the record of the most recently associated wireless network is not evicted from the database.

9. A method as recited in claim 4, further comprising:

periodically updating the database.

10. A method as recited in claim 2, further comprising:

prior to the station being associated with a wireless network, L3 accepting one or more L3 packets found in the gathering step.

11. A method as recited in claim 10, wherein the accepting by L3 is in an order according to one or more ordering criteria.

12. A method as recited in claim 2, further comprising:

associating with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

13. A method as recited in claim 10, wherein at least one of the L3 packets accepted by L3 is a mobility agent advertisement.

14. A method as recited in claim 13, further comprising:

associating with a particular wireless network from where an L2 data unit containing a particular mobility agent advertisement was received,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular mobility agent advertisement.

15. A method as recited in claim 14, further comprising:

at L3 of the station, registering with the mobility agent by exchanging L3 packets with the mobility agent.

16. A method as recited in claim 15, further comprising:

after the associating, determining that a re-association is necessary;

selecting for re-associating a wireless network according to one or more re-association criteria; and

re-associating with the selected wireless network.

17. A method as recited in claim 16, wherein the re-association criteria include that the selected wireless network is in communication with the mobility agent that the station was registered with at the time of the determining that a re-association is necessary.

18. A method as recited in claim 14,

wherein the mobility agent that sent the particular mobility agent advertisement is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent that sent the particular mobility agent advertisement, the station is mobile router.

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

after the association with an AP in communication with the mobility agent, locking the association.

20. A method as recited in claim 13, wherein the gathering information prior to associating includes:

emulating one or more interfaces to one or more wireless networks that the station can hear, each said emulated interface thus forming a floating interface that after association can become an actual interface to a wireless network that is in communication with a mobility agent.

21. A method as recited in claim 20,

wherein the reporting of a particular L3 mobility agent advertisement to L3 is via a floating interface to the particular wireless networks from where the L2 data unit containing the particular mobility agent advertisement was received,

such that the particular reported L3 packet appear to L3 as if from an actual interface even though the station is not yet associated with the particular wireless network of the floating interface.

22. A method as recited in claim 21, further comprising:

associating with the particular wireless network from where the L2 data unit containing the particular L3 mobility agent advertisement was received,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 mobility agent advertisement.

23. A method as recited in claim 2, further comprising:

selecting a wireless network for association whose AP the station can hear, the selecting according to one or more selection criteria,

wherein at least one of the selection criteria uses at least some of the gathered information.

24. A method as recited in claim 23, wherein the selection criteria include that the L2 data unit received from the AP of the selected wireless network includes a mobility agent advertisement, such that after association, the station is in communication with a mobility agent.

25. A method as recited in claim 24, further comprising:

associating with a particular selected wireless network from where an L2 data unit containing a particular mobility agent advertisement was received,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular mobility agent advertisement.

26. A method as recited in claim 25, further comprising:

at L3 of the station, registering with the mobility agent by exchanging L3 packets with the mobility agent.

27. A method as recited in claim 26, further comprising:

after the associating, determining that a re-association is necessary;

selecting for re-associating a wireless network according to one or more re-association criteria; and

re-associating with the selected wireless network.

28. A method as recited in claim 27, wherein the re-association criteria include that the selected wireless network is in communication with the mobility agent that the station was registered with at the time of the determining that a re-association is necessary.

29. A method as recited in claim 25,

wherein the mobility agent that sent the particular mobility agent advertisement is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent that sent the particular mobility agent advertisement, the station is mobile router.

30. A method as recited in claim 2,

wherein the station includes one or more wireless network devices each capable of providing a link-layer interface to a wireless network, and

wherein the receiving is of L2 data units from APs that each of the wireless network devices can hear,

the method further comprising:

based on the gathered information, emulating at L2 one or more interfaces to one or more wireless networks whose APs the one or more wireless network devices can hear as if the station was associated to the wireless network via the device, without there necessarily being any association with any wireless network, each emulated interface thus forming a floating interface to a wireless network via a wireless network device that after association can become an actual interface to the wireless network via the wireless network device,

L3 accepting one or more L3 packets that were in L2 data units from one or more APs via one or more of the floating interfaces as if the station was associated with the one or more APs whose L2 data units included the L3 packets.

31. A method as recited in claim 30, wherein the accepting by L3 is in an order according to one or more ordering criteria.

32. A method as recited in claim 1,

wherein the station includes one or more wireless network devices each capable of providing a link-layer interface to a wireless network, and

wherein the receiving is of L2 data units from APs that each of the wireless network devices can hear,

the method further comprising:

based on the gathered information, emulating at L2 one or more interfaces to one or more wireless networks whose APs the one or more wireless network devices can hear as if the station was associated to the wireless network via the device without there necessarily being any association with the wireless network, each emulated interface thus forming a floating interface to a wireless network via a wireless network device that after association can become an actual interface to the wireless network via the wireless network device; and

storing information about the floating interfaces in a database.

33. A method as recited in claim 32, wherein the information stored about each floating interface includes an identifier of the wireless network of the floating interface and one or more of the L3 information in the L2 information received from the AP of the wireless network, a time stamp of when the L2 information received was received from the AP, an indication of the signal strength of the L2 information from the AP, and the state of the floating interface to the wireless network.

34. A method as recited in claim 33,

wherein the station includes a plurality of wireless network devices each capable of providing an interface to a wireless network, and

wherein the database further includes an indication of which wireless network device the floating interface is for.

35. A method as recited in claim 33, wherein the information stored about each floating interface includes an indication of any mobility information contained in any L3 information in the received L2 information.

36. A method as recited in claim 33, wherein the database further stores an indication of which floating interface was the most recently used association to a wireless network.

37. A method as recited in claim 36, further comprising:

periodically updating the database of floating interfaces,

wherein the database includes a record for each floating interface, and wherein the record of the floating interface most recently used in an association is not evicted from the wireless network database.

38. A method as recited in claim 36, further comprising:

periodically updating the database of floating interfaces.

39. A method in a wireless station having a wireless network device, the method operating at the link layer (L2) of a multi-layer communication protocol that includes the link layer and a network layer (L3), the method comprising:

prior to the station being associated with a wireless network, wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks;

prior to the station being associated with a wireless network, analyzing said received L2 data units to identify the AP and to ascertain whether any of said L2 data units contains an L3 advertisement from a mobility agent,

prior to the station being associated with a wireless network, if it is ascertained that an L2 data unit contains an advertisement from a mobility agent, reporting the advertisement to L3 at the station as if the station was associated with the network of the AP that transmitted the L2 data unit containing the L3 advertisement;

in the case that L3 at the station responds to the L3 advertisement by passing to the station'"'"'s L2 an L3 response to the L3 advertisement addressed to the mobility agent that sent the L3 advertisement, accepting the L3 response from L3 at the station prior to the station being associated with a wireless network, and

after said analyzing L2-data units, reporting to L3, and accepting the L3 response, associating the station to the AP that transmitted the L2 data unit containing the L3 advertisement,

such that the wireless station associates with an AP that is in communication with a mobility agent.

40. A method as recited in claim 39, wherein the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6.

44. A method as recited in claim 39, wherein the received L2 data unit includes an indication of signal quality, wherein the reporting includes,

selecting one or more data units that include an L3 packet, the selecting according to one or more selection criteria;

and

for each selected L2 data unit, passing the L3 packet contained in the selected L2 data unit to the network layer as if the station was associated with the AP that transmitted the selected data unit,

the passing being according to an order based on one or more ordering criteria,

and wherein the analyzing further includes examining the signal quality of a data unit from any identified AP.

45. A method as recited in claim 44,

wherein the one or more selection criteria include that the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6.

46. A method as recited in claim 45,

wherein analyzing includes examining the signal strength of the received L2 data units, and

wherein the one or more ordering criteria include the signal strength of the received L2 data units,

such that L3 packets in L2 data units with higher received signal quality and that include a FA or access router mobility advertisement are reported to L3 before L3 packets with lower wireless signal quality.

47. A method as recited in claim 39,

wherein the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent, the station is mobile router.

48. A method as recited in claim 47, further comprising:

after association with an AP in communication with the mobility agent, locking the association.

41. A method as recited in 40, wherein the analyzing includes:

ascertaining whether that said L2 data unit contains an IP packet whose protocol field identifies it as an ICMP packet; and

if it is ascertained that the L2 data unit includes an ICMP packet, verifying that the ICMP packet contains an ICMP extension with a TYPE field identifying said IP packet as a router advertisement.

42. A method as recited in 41, wherein the mobility agent is a foreign agent conforming to IPv4, and wherein the analyzing includes:

verifying that the IP packet is an IPv4 packet, and

if it is ascertained that the IP packet is a router advertisement, ascertaining whether the ICMP packet contains an ICMP extensions with a TYPE field identifying the router advertisement as a foreign agent advertisement.

43. A method as recited in 41, wherein the mobility agent is an access router conforming to IPv6, and wherein the analyzing includes:

verifying that said IP packet is an IPv6 packet.

49. In a wireless station registered with a first mobility agent and associated with a first wireless network that is in communication with the first mobility agent, the station having a first wireless network device providing a link-layer (L2) interface to the first wireless network, a method operating at the link layer (L2) of a multi-layer network protocol, a method comprising:

determining that a re-association is necessary;

selecting for re-associating a wireless network that the station could hear, the selecting according to one or more re-association criteria at least one of which uses L3 information, the L3 information provided in a stored database of information gathered at the station by an L2 data gathering process; and

re-associating with the selected wireless network,

wherein the L2 data gathering process includes;

wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear while the station is not necessarily associated with any wireless network; and

examining the received L2 data units.

50. A method as recited in claim 49, wherein the first wireless network conforms to one of the IEEE 802.11 standards.

51. A method as recited in claim 49, wherein the information stored in the database about each wireless network includes an identifier of the wireless network, the L3 information in the L2 data unit received from the AP of the wireless network, a time stamp of when the L2 data unit was received from the AP, and an indication of the signal strength of the L2 data unit from the AP.

52. A method as recited in claim 51, wherein the information stored about each wireless network includes an indication of any mobility information contained in any L3 information in the received L2 data unit.

53. A method as recited in claim 51, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.

54. A method as recited in claim 53, further comprising:

periodically updating the database,

wherein the database includes a record for each wireless network, and wherein the record of the most recently associated wireless network is not evicted from the database.

55. A method as recited in claim 51, further comprising:

periodically updating the database.

56. A method as recited in claim 55, wherein the updating includes:

wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear while the station is not associated with any wireless network used for the wirelessly receiving; and

updating the database using the wirelessly received L2 data units.

57. A method as recited in claim 56, wherein the wirelessly receiving L2 data units of the updating is via the first wireless network device.

58. A method as recited in claim 56, wherein the station further includes a second wireless network device and wherein the wirelessly receiving L2 data units of the updating is via the second wireless network device.

59. A method as recited in claim 49, wherein the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6.

60. A method as recited in claim 52,

wherein the first mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station includes a router that provides Mobile IP services when the station is registered at L3 with the first mobility agent,

such that prior to determining a re-association is necessary and after the re-associating, the station is mobile router.

61. In a wireless station having a wireless network device, the device capable of providing a link-layer (L2) interface to a wireless network, an apparatus operating at the link layer (L2) of a multi-layer network protocol, the apparatus comprising:

means for wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear, the receiving being prior to the station being associated with a wireless network via the wireless network device; and

means for gathering information about the received L2 data units, including L2 information and L3 information,

the L3 information gathered at L2 including whether an AP is sending one or more L3 packets from one or more mobility agents,

such that the station may associate with a wireless network that is in communication with a mobility agent.

62. An apparatus as recited in claim 61, further comprising:

means for storing information about the wireless networks that the station can hear in a database, the information including L3 information from the one or more mobility agents.

63. An apparatus as recited in claim 62, wherein the one or more wireless networks whose APs transmit L2 data units conform to one of the IEEE 802.11 standards.

64. An apparatus as recited in claim 62, further comprising:

means for associating with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

65. An apparatus as recited in claim 62, wherein the information stored about each wireless network includes an identifier of the wireless network, the L3 information in the L2 data unit received from the AP of the wireless network, a time stamp of when the L2 data unit was received from the AP, and an indication of the signal strength of the L2 data unit from the AP.

66. An apparatus as recited in claim 65, wherein the information stored about each wireless network includes an indication of any mobility information contained in any L3 information in the received L2 data unit from the AP of the wireless network.

67. An apparatus as recited in claim 65, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.

68. An apparatus as recited in claim 67, further comprising

means for periodically updating the database,

wherein the database includes a record for each wireless network, and wherein the record of the most recently associated wireless network is not evicted from the database.

69. An apparatus as recited in claim 65, further comprising

means for periodically updating the database.

70. An apparatus as recited in claim 62, further comprising:

means for accepting by L3 one or more L3 packets found in the gathering step, the accepting by L3 prior to the station being associated with a wireless network.

71. An apparatus as recited in claim 70, wherein the means for accepting by L3 accepts in an order according to one or more ordering criteria.

72. An apparatus as recited in claim 70, wherein the means for accepting by L3 accepts at least one mobility agent advertisement.

73. An apparatus as recited in claim 72, further comprising:

means for associating with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

74. An apparatus as recited in claim 73, further comprising:

means for registering the station with the mobility agent by exchanging L3 packets with the mobility agent.

75. An apparatus as recited in claim 73,

wherein the mobility agent that sent the particular mobility agent advertisement is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent that sent the particular mobility agent advertisement, the station is mobile router.

76. An apparatus as recited in claim 72, wherein the means for gathering information prior to associating includes:

means for emulating one or more interfaces to one or more wireless networks that the station can hear, each said emulated interface thus forming a floating interface that after association can become an actual interface to a wireless network that is in communication with a mobility agent.

77. An apparatus as recited in claim 76,

wherein the means for reporting reports particular L3 mobility agent advertisement to L3 via a floating interface to the particular wireless networks from where the L2 data unit containing the particular mobility agent advertisement was received,

such that the particular reported L3 packet appear to L3 as if from an actual interface even though the station is not yet associated with the particular wireless network of the floating interface.

78. An apparatus as recited in claim 62, further comprising:

means for selecting a wireless network for association whose AP the station can hear, the selecting means selecting according to one or more selection criteria,

wherein at least one of the selection criteria uses at least some of the gathered information.

79. An apparatus as recited in claim 78, wherein the selection criteria include that the L2 data unit received from the AP of the selected wireless network includes a mobility agent advertisement, such that after association, the station is in communication with a mobility agent.

80. An apparatus as recited in claim 79, further comprising:

means for associating with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

81. An apparatus as recited in claim 80,

wherein the mobility agent that sent the particular mobility agent advertisement is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent that sent the particular mobility agent advertisement, the station is mobile router.

82. An apparatus as recited in claim 79, wherein the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6.

83. An apparatus as recited in claim 72,

wherein the means for accepting by L3 accepts in an order according to one or more ordering criteria,

wherein the means for gathering information includes means for examining the signal strength of the received L2 data units, and

wherein the one or more ordering criteria include the signal strength of the received L2 data units,

such that L3 packets in L2 data units with higher received signal quality and that include a FA or access router mobility advertisement are reported to L3 before L3 packets with lower wireless signal quality.

84. In a wireless station registered with a first mobility agent and associated with a first wireless network that is in communication with the first mobility agent, the station having a first wireless network device providing a link-layer (L2) interface to the first wireless network, an apparatus operating at the link layer (L2) of a multi-layer network protocol, an apparatus comprising:

means for determining that a re-association is necessary;

means for selecting for re-associating a wireless network that the station could hear, the selecting means selecting according to one or more re-association criteria at least one of which uses L3 information, the L3 information provided in a stored database of information gathered at the station by an L2 data gathering process; and

means for re-associating with the selected wireless network,

wherein the L2 data gathering process includes;

wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear while the station is not necessarily associated with any wireless network; and

examining the received L2 data units.

85. An apparatus as recited in claim 84, wherein the first wireless network conforms to one of the IEEE 802.11 standards.

86. An apparatus as recited in claim 84, wherein the information stored in the database about each wireless network includes an identifier of the wireless network, the L3 information in the L2 data unit received from the AP of the wireless network, a time stamp of when the L2 data unit was received from the AP, and an indication of the signal strength of the L2 data unit from the AP.

87. An apparatus as recited in claim 86, wherein the information stored about each wireless network includes an indication of any mobility information contained in any L3 information in the received L2 data unit.

88. An apparatus as recited in claim 86, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.

89. An apparatus as recited in claim 88, further comprising:

means for periodically updating the database,

wherein the database includes a record for each wireless network, and wherein the record of the most recently associated wireless network is not evicted from the database.

90. An apparatus as recited in claim 86, further comprising:

means for periodically updating the database.

91. An apparatus as recited in claim 90, wherein the means for updating includes:

means for wirelessly receiving L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear while the station is not associated with any wireless network used for the wirelessly receiving; and

means for updating the database using the wirelessly received L2 data units.

92. An apparatus as recited in claim 91, wherein the means for wirelessly receiving receives L2 data units via the first wireless network device.

93. An apparatus as recited in claim 91, wherein the station further includes a second wireless network device and wherein the means for wirelessly receiving receives L2 data units via the second wireless network device.

94. An apparatus as recited in claim 84, wherein the mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6.

95. An apparatus as recited in claim 87,

wherein the first mobility agent is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein the station includes a router that provides Mobile IP services when the station registered at L3 with the first mobility agent,

such that prior to determining a re-association is necessary and after the re-associating, the station is mobile router.

96. A wireless station comprising:

a wireless network device capable of providing a link-layer (L2) interface to a wireless network, the wireless network device to wirelessly receive L2 data units transmitted from one or more wireless access point (APs) of one or more wireless networks that the station can hear, the receiving being prior to the station being associated with a wireless network via the wireless network device; and

a processor coupled to the wireless network device to gather information about the received L2 data units, including L2 information and L3 information;

the L3 information gathered at L2 including whether an AP is sending one or more L3 packets from one or more mobility agents,

such that the station may associate with a wireless network that is in communication with a mobility agent.

97. A wireless station as recited in claim 96, further comprising:

a memory coupled to the processor, the memory to store information about the wireless networks that the station can hear in a database, the information including L3 information from the one or more mobility agents.

98. A wireless station as recited in claim 97, wherein the processor is programmed associate with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

99. A wireless station as recited in claim 97, wherein the one or more wireless networks whose APs transmit L2 data units conform to one of the IEEE 802.11 standards.

100. A wireless station as recited in claim 97, wherein the information stored about each wireless network includes an identifier of the wireless network, the L3 information in the L2 data unit received from the AP of the wireless network, a time stamp of when the L2 data unit was received from the AP, and an indication of the signal strength of the L2 data unit from the AP.

101. A wireless station as recited in claim 100, wherein the information stored about each wireless network includes an indication of any mobility information contained in any L3 information in the received L2 data unit from the AP of the wireless network.

102. A wireless station as recited in claim 100, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.

103. A wireless station as recited in claim 102,

wherein the processor is programmed to periodically update the database, and

wherein the database includes a record for each wireless network, and wherein the record of the most recently associated wireless network is not evicted from the database.

104. A wireless station as recited in claim 100 wherein the processor is programmed to periodically update the database.

105. wireless station as recited in claim 97, further comprising:

an L2 to L3 interface coupled to the processor for an L3 process running on the processor to accept one or more L3 packets found in the gathering, the accepting by L3 prior to the station being associated with a wireless network.

106. A wireless station as recited in claim 105, wherein processor is programmed to accept at L3 at least one mobility agent advertisement via the L2 to L3 interface.

107. A wireless station as recited in claim 106, wherein processor is further programmed to associate with a particular wireless network from where an L2 data unit was received that contains a particular L3 packet containing a mobility agent advertisement,

such that after the associating, the wireless network interface of the station provides an interface to the particular wireless network that is in communication with the mobility agent that sent the particular L3 packet.

108. A wireless station as recited in claim 107,

wherein the mobility agent that sent the particular mobility agent advertisement is a Mobile IP foreign agent sending IP packets conforming to IPV4 or an access router sending IP packets conforming to IPv6, and

wherein said station is a router that provides Mobile IP services,

such that after association with an AP in communication with the mobility agent that sent the particular mobility agent advertisement, the station is mobile router.