Lucchina, Massimo G. (Villeneuve Loubet, FR)
Thubert, Pascal (La Colle Sur Loup, FR)
Plaque It!
Sponsored by: Flash of Genius |
What is claimed is:
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 IPv4, 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. associating with a particular wireless network from where an L2 data unit containing a particular L3 packet 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 packet.
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 IPv4, 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.
41. A method as recited in
42. A method as recited in
43. A method as recited in
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 IPv4.
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 IPv4, 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.
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 IPv4, 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. A carrier medium carrying computer readable code segments to instruct one or more processors to implement a method operating at the link layer (L2) of a multi-layer network protocol, the one or more processors in a wireless station, the station having a wireless network device, the device capable of providing a link-layer (L2) interface to a wireless network, the method comprising: 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 gathering information about the received L2 data units, including L2 information and L3 information, wherein 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. A carrier medium as recited in claim 61, wherein the method further comprises: 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. A carrier medium 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. A method as recited in claim 62, wherein the method further comprises: 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. A carrier medium 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. A carrier medium 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. A carrier medium 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. A carrier medium as recited in claim 67, wherein the method further comprises 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. A carrier medium as recited in claim 65, wherein the method further comprises periodically updating the database.
70. A carrier medium as recited in claim 62, wherein the method further comprises: accepting by L3 one or more L3 packets contained in the received L2 data units, the accepting by L3 prior to the station being associated with a wireless network.
71. A carrier medium as recited in claim 70, wherein the accepting by L3 accepts in an order according to one or more ordering criteria.
72. A carrier medium as recited in claim 70, wherein the accepting by L3 accepts at least one mobility agent advertisement.
73. A carrier medium as recited in claim 72, wherein the method further comprises: 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. A carrier medium as recited in claim 73, wherein the method further comprises: registering the station with the mobility agent by exchanging one or more L3 packets with the mobility agent.
75. A carrier medium 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 IPv4, 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. A carrier medium as recited in claim 72, 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.
77. A carrier medium as recited in claim 76, wherein the 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. A carrier medium as recited in claim 62, wherein the method further comprises: 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.
79. A carrier medium 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. A method as recited in claim 79, wherein the method further comprises: 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.
81. A carrier medium 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 IPv4, 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. A carrier medium 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. A carrier medium as recited in claim 72, wherein the accepting by L3 accepts in an order according to one or more ordering criteria, wherein the gathering information 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.
84. A carrier medium carrying computer readable code segments to instruct one or more processors to implement a method operating at the link layer (L2) of a multi-layer network protocol, the one or more processors in a wireless station, the 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 having a wireless network device, the device capable of providing a link-layer (L2) interface to a wireless network, the 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.
85. A carrier medium as recited in claim 84, wherein the first wireless network conforms to one of the IEEE 802.11 standards.
86. A carrier medium 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. A carrier medium 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. A carrier medium 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. A carrier medium as recited in claim 88, wherein the method further comprises: 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. A carrier medium as recited in claim 86, wherein the method further comprises: periodically updating the database.
91. A carrier medium as recited in claim 90, 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.
92. A carrier medium as recited in claim 91, wherein the wirelessly receiving receives L2 data units via the first wireless network device.
93. A carrier medium as recited in claim 91, wherein the station further includes a second wireless network device and wherein the wirelessly receiving receives L2 data units via the second wireless network device.
94. A carrier medium 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. A carrier medium 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 IPv4, 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. 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.
97. An apparatus as recited in claim 96, 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.
98. An apparatus 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.
99. An apparatus as recited in claim 97, 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.
100. An apparatus 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. An apparatus 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. An apparatus 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. An apparatus as recited in claim 102, 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.
104. An apparatus as recited in claim 100, further comprising means for periodically updating the database.
105. An apparatus as recited in claim 97, 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.
106. An apparatus as recited in claim 105, wherein the means for accepting by L3 accepts in an order according to one or more ordering criteria.
107. An apparatus as recited in claim 105, wherein the means for accepting by L3 accepts at least one mobility agent advertisement.
108. An apparatus as recited in claim 107, 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.
109. An apparatus as recited in claim 108, further comprising: means for registering the station with the mobility agent by exchanging L3 packets with the mobility agent.
110. An apparatus as recited in claim 108, 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 IPv4, 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.
111. An apparatus as recited in claim 107, 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.
112. An apparatus as recited in claim 111, 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.
113. An apparatus as recited in claim 97, 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.
114. An apparatus as recited in claim 113, 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.
115. An apparatus as recited in claim 114, 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.
116. An apparatus as recited in claim 115, 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 IPv4, 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.
117. An apparatus as recited in claim 114, 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.
118. An apparatus as recited in claim 107, 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.
119. 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.
120. An apparatus as recited in claim 119, wherein the first wireless network conforms to one of the IEEE 802.11 standards.
121. An apparatus as recited in claim 119, 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.
122. An apparatus as recited in claim 121, 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.
123. An apparatus as recited in claim 121, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.
124. An apparatus as recited in claim 123, 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.
125. An apparatus as recited in claim 121, further comprising: means for periodically updating the database.
126. An apparatus as recited in claim 125, 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.
127. An apparatus as recited in claim 126, wherein the means for wirelessly receiving receives L2 data units via the first wireless network device.
128. An apparatus as recited in claim 126, 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.
129. An apparatus as recited in claim 119, 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.
130. An apparatus as recited in claim 122, 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 IPv4, 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.
131. 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.
132. A wireless station as recited in claim 131, 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.
133. A wireless station as recited in claim 132, 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.
134. A wireless station as recited in claim 132, wherein the one or more wireless networks whose APs transmit L2 data units conform to one of the IEEE 802.11 standards.
135. A wireless station as recited in claim 132, 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.
136. A wireless station as recited in claim 135, 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.
137. A wireless station as recited in claim 135, wherein the database further stores an indication of which wireless network information is of the most recent association to a wireless network.
138. A wireless station as recited in claim 137, 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.
139. A wireless station as recited in claim 135 wherein the processor is programmed to periodically update the database.
140. A wireless station as recited in claim 132, 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.
141. A wireless station as recited in claim 140, wherein processor is programmed to accept at L3 at least one mobility agent advertisement via the L2 to L3 interface.
142. A wireless station as recited in claim 141, 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.
143. A wireless station as recited in claim 142, 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 IPv4, 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.
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to communication networks, and in particular to a wireless station of a wireless data network finding at L2 one or more access points that are in communication with a mobility agent, such that the wireless station can associate with such an access point to enable Mobile IP services.
[0003] 2. Background
[0004] Wireless networks such as wireless local area networks (WLANs) are known. In a WLAN, stations are able to communicate wirelessly within a local network. In an infrastructure network, all communication is via an access point that acts as a base station. Any entity on the WLAN can also communicate with a node on any other wired or wireless network that is connected to the WLAN, e.g., via the access point.
[0005] Mobile IP is a well known extension of the Internet Protocol (IP) that enables a node on an IP-based network to change its physical attachment point in the network, e.g., the Internet, while retaining the same IP address by which it is identified on its home network. Agents providing Mobile IP services send IP packets that include advertisements of the services they provide. Thus, determining IP services is a process that occurs at L3 of the communication protocol.
[0006] While WLANs typically enable a wireless node to move from place to place within a small area, e.g., at a LAN level, without disrupting communications, mobile IP provides IP address mobility across a global network such as the Internet.
[0007] A station in a WLAN is not guaranteed to function seamlessly as Mobile IP node. In particular, a prior art wireless station associates with an access point at L2. Because the availability of IP services is determined at L3, prior art wireless stations do not function seamlessly with Mobile IP.
[0008] It is desired for a station on a WLAN also to be able to communicate using Mobile IP. In particular, it is desired for the wireless station to determine what IP services, if any, are available to access points prior to attaching to an access point.
[0009] The following discussion provides a brief overview of Mobile IP and wireless LANs, including definitions. A review of the need for the invention follows the discussion.
[0010] Mobile IP
[0011] The purpose of Mobile IP is to enable a mobile node to retain its home IP address even when it is away from its home subnetwork of an overall network such as the Internet. This is accomplished by the addition of a mobility agent, a router known in MIPv4 as a foreign agent, that provides the node with a “care-of” address for the mobile node. MIPv6 provides a slightly different mechanism. The care-of address is part of the IP packet itself, so that foreign agents are not required. The mobile node's home network similarly adds a mobility agent, in this case a router known as a home agent, which forwards IP packets addresses to the mobile node's IP address to the node's care-of address on the foreign network.
[0012] When a MIPv4 mobile node determines that it is not attached to its home network, it listens for router advertisements from a foreign agent. Such foreign agent advertisements contain one or more care-of addresses. After obtaining a care-of address, the mobile node then registers with the foreign agent, and subsequently, registers the care-of address with its home agent. Once these registrations are complete, the home agent intercepts IP packets containing the IP address of the mobile node and forwards them, via an IP tunnel, to the care-of address. When these IP packets reach the foreign network, the foreign agent redirects them to the mobile IP node at its care-of address. Thus the foreign agent removes them from the tunnel and the home agent together act as proxies for the mobile node's IP address, routing inbound and outbound traffic to and from the mobile node using its home IP address. When a mobile note again changes its attachment point to the Internet, it locates a new foreign agent, obtains a new care-of address, and re-registers with its home agent.
[0013] Note that the providing of Mobile IP services by foreign agents and home agents uses IP packets, and thus occurs at the network layer (layer-3).
[0014] According to RFC 3344, there is only one active care-of address for each foreign agent or access router, and therefore a single reverse tunnel to the Home Agent needs to be set up.
[0015] Wireless LANs
[0016] WLANs conform to one or more known protocols, such as the various versions of the IEEE 802.11 standard. An infrastructure WLAN includes an access point (AP) to act as a base station in the WLAN so that any wireless communication between stations in the WLAN occurs via the AP. Typically, the AP is connected to a wired network such as a LAN which in turn may be connected to a wide area network (WAN) such as the Internet. Any station in the WLAN can thus communicate with both the wired LAN or WAN via the AP.
[0017] According to the IEEE 802.11 standards, a station attempts to associate with an AP by scanning in “RF monitor mode” for signals, known as “beacon signals,” that periodically originate from an AP. Beacon signals, in addition to other functions, serve to uniquely identify the AP within the WLAN. When a station detects a beacon, it switches into send-receive mode and executes an association protocol with the AP. At the successful end of the association protocol, the station is said to be associated with the AP.
[0018] Once a station associates with an AP, the AP is responsible for delivering network traffic to the station (and other associated stations). While an AP may associate with multiple stations, a station may associate with only one AP at a time, even though there may be more than one AP that the station can physically communicate with. When an associated station loses communication with its AP, the station must re-associate, either with a different AP, or the same AP.
[0019] The association between a station and an AP is initiated by a station, not an AP. After receiving one or more beacon signals, the station selects an AP it can communicate with, e.g., after receiving a beacon signal, and begins the association protocol. The criteria for a station selecting one AP over another is not specified in the IEEE 802.11 standard, but in practice, at minimum it is based on the quality of the wireless signal from the available APs. As previously noted, once associated, the station does not directly wirelessly communicate with any station not associated with its AP.
[0020] Note that the associating of a station with an AP occurs at the link layer (layer-2) of the protocol. In contrast, the providing of Mobile IP services by foreign agents and home agents uses IP packets, and thus occurs at the network layer (layer-3). Because the association procedure occurs at a lower protocol layer than Mobile IP services, the association between an AP and a station occurs at a protocol layer wherein there is ignorance of Mobile IP services, and thus occurs without regard to whether the AP is in communication with any mobility agents.
[0021] Therefore, there is a need in the art for a method and apparatus that enables a station of a WLAN to discover, prior to association, whether one or more candidate APs for association that are in communication with Mobile IP agents, e.g. with home agents and/or foreign agents. There also is a need subsequently to select for association one of the APs in communication with a mobility agent so that the wireless station can benefit from and/or provide Mobile IP services.
[0022] Definitions
[0023] Some of the following definitions are applicable to a wireless local area network (WLAN) that conforms to one of the IEEE 802.11 standards. Other WLAN standards exist and future ones may be developed. The present invention is not restricted to working with IEEE 802.11 conforming networks.
[0024] Access Point (AP): In the IEEE 802.11 standards, an AP is a wireless base station through which communication is managed in an infrastructure network (see BSS). An AP may be in communication with other wired or wireless networks. When compared to functions in a wired network, it is analogous to an Ethernet hub with optional access control to other networks.
[0025] Access Router: A router that provides access between two or more networks, for example, between a WLAN and a LAN, or between a LAN and the Internet. See also Mobility Agent.
[0026] Ad Hoc Network: See IBBS.
[0027] Association: In the IEEE 802.11 standards, association is the procedure used to establish a binding between an access point and a station, to make the station part of the wireless network managed by the AP. Note that prior to association, a station may be in passive scanning mode, called RF monitor mode herein (see below), but while associated the station is in send-receive mode (see below), called “station” mode in the case of an IEEE 802.11 STA.
[0028] Associated station: In an IEEE 802.11 BSS (or ESS) WLAN, communications between stations and other networks is managed by an AP. A station becomes an associated station when it has been successfully accepted by the AP to be part of the wireless network managed by that AP.
[0029] Beacon: A periodic 802.11 frame transmitted by an AP that provides information required by stations for establishing and maintaining an association with the AP. The beacon contains the unique identifier called the Service Set Identifier (SSID) for the wireless network of the AP. See also SSID.
[0030] BSS: In the IEEE 802.11 standards, a Basic Service Set (BSS) is a single infrastructure wireless network in which all wireless communication occurs via a single access point. See also below under IBSS: an independent BSS.
[0031] ESS: An IEEE 802.11 Extended Service Set is a WLAN that includes two or more BSSs, the APs of which may provide service to overlapping physical areas. The APs behave as a single logical router for all nodes in the ESS.
[0032] Foreign Agent (FA): A type of Mobility Agent, specifically an IPv4 router on a mobile node's visited network that provides routing services to the mobile node while registered. The foreign agent detunnels and delivers IP packets that were tunneled by the mobile node's home agent to the mobile node. For IP packets sent by a mobile node, the foreign agent may serve as a default router for registered mobile nodes. Foreign agents do not exist in Mobile IPV6. The IP packets themselves include the care-of address and the services provided by a foreign agent in IPv4 is provided by an access router.
[0033] Foreign Agent Advertisement: A Mobility Agent advertisement sent by a foreign agent. See Mobility Agent advertisement.
[0034] Foreign Network: Any network other than the mobile node's Home Network.
[0035] Home Agent (HA): A type of mobility agent, specifically a Mobile IPv4 or Mobile IP version 6 router on a mobile node's home link that maintains current location information for the mobile node in the form of a current care-of address and, while the mobile node is away from home, intercepts packets on the home link destined to the mobile node's home address and tunnels packets for delivery to the mobile node's registered care-of address. A Home Agent is a mobility agent.
[0036] Home Address: In Mobile IP, an IP address that is assigned for an extended period of time to a mobile node. It remains unchanged, regardless of where the node is attached to the network.
[0037] Home Network: A network, possibly virtual, having a network prefix matching that of a mobile node's home address. Note that standard IP routing mechanisms will deliver IP packets destined to a mobile node's home address to the mobile node's home network.
[0038] IBSS: In the IEEE 802.11 standards, an Independent Basic Service Set (IBSS) is a WLAN with two or more wireless nodes that communicate directly without associating with an AP. Also referred to as an ad hoc wireless network in contrast to an infrastructure wireless network.
[0039] Infrastructure Network: A wireless network in which all STAs communicate via an AP. See BSS and ESS.
[0040] IETF: Internet Engineering Task Force, the standardization body for Internet related technology.
[0041] IP: the Internet Protocol, e.g., IP version 4 (IPv4) or IP version 6 (IPv6).
[0042] Interface: An interface is used herein in several contexts. In the context of the network layer, e.g., IP including mobile IP, an interface (also an L3 interface) is an L3 node's attachment to a link at L2. In this definition, a node is a device that implements IP, and an L2 link is a communication facility or medium over which nodes can communicate at the link layer (L2), such as a simple or bridged Ethernet. For example, a wireless network device provides a bi-directional interface to a WLAN after a station associates with the AP of the WLAN.
[0043] Interface Identifier: A number used to identify a node's interface on a link. In one embodiment, the interface identifier is the set of remaining low-order bits in the node's IP address after the subnet prefix.
[0044] Internet Router Discovery Protocol (IRDP): A protocol for routers on a network broadcast their presence to other nodes on the network. A router supporting this protocol periodically broadcasts an Internet Control Message Protocol (ICMP) IP packet containing a “router advertisement.” A node on the network may at any time invoke a router advertisement by broadcasting a “router solicitation.” Mobile IP defines (RFC 3344) extensions to this protocol that identifies the router advertisement as a “home agent advertisement” and/or a “foreign agent advertisement.” See Mobility Agent Advertisement below.
[0045] Mobility Agent (MA): In MIPv4, the Mobility Agents are foreign agents that receive data from home agents, and the home agents. In IPv6, the Mobility Agents are access routers and home agents. One aspect of the present invention is the discovery at L2 of mobility agents such as home agents, foreign agents and/or access routers. The term Mobility Agent is used herein as a general term encompassing foreign agents, home agents, and access routers.
[0046] Mobility Agent Advertisement: Mobility agent advertisements are transmitted by a mobility agent to advertise its services. Mobile nodes use these advertisements to determine their current point of attachment e.g., to the Internet. A mobility agent advertisement is an Internet Control Message Protocol (ICMP) IP packet that includes a Router Advertisement that has been extended to also carry a mobility agent advertisement Extension. The exact function of the advertisement—home agent, foreign agent, or access router—is identified by a FLAGS field in the extension header.
[0047] Mobile IP, IP Mobility: An IETF document (RFC 3344) that describes the infrastructure in which a mobile node may change its attachment point from one network or subnetwork to another without changing its home (IP) address.
[0048] Mobile IPv4: Mobile IP for IP version 4. Same as (RFC 3344).
[0049] Mobile IPv6: Mobile IP to work with IP version 6. See, for example, David B. Johnson, Charles E. Perkins, and Jari Arkko: “Mobility Support in IPv6” (document title “draft-ietf-mobileip-ipv6-18.txt”, available on the Internet at http://www.ietf.org/internet-drafts/draft-ietf-mobileip-ipv6 -18.txt. In Mobile IP for IP version 6, the care-of-address is included in the IP packet itself. Therefore, in Mobile IPv6, foreign agents do not exist. The only Mobile IP requirement placed upon the foreign network is to provide an access router capable of routing packets to the Mobile IP node's home address.
[0050] Mobile Network: A network that moves together with a Mobile Router. See also Mobile Router.
[0051] Mobile Node: In Mobile IP, a node in a network, e.g., a host or router that changes its point of attachment from one network or subnetwork to another. A mobile node may change its location without changing its IP address; it may continue to communicate with other Internet nodes at any location using its (constant) IP address, assuming link-layer connectivity to a point of attachment is available. Mobile nodes may remain at a stationary location or be in motion. For purposes of the present invention, mobile stations and portable stations as defined in IEEE 802.11 can also be mobile nodes if they support Mobile IP.
[0052] Mobile Router: A mobile node that is a router. A mobile router provides for the mobility of one or more networks moving together, for example, on an airplane or a ship. The nodes connected to a network served by the Mobile Router may themselves be mobile nodes or routers. Using the present invention, a STA of an infrastructure wireless network that provides routing may be a mobile router.
[0053] Mobile Station: In the IEEE 802.11, a type of station that is able to use network communications while in motion. A mobile station is a type of mobile node when Mobile IP enabled. See also portable station.
[0054] Portable Station: In the IEEE 802.11 standards, a type of station that may be moved from location to location, but that is only able to use network communications while stationary at a fixed location (i.e., not in motion). A portable station is a type of mobile node when Mobile IP enabled. See also mobile station.
[0055] Re-association: In the IEEE 802.11 standards, The process whereby a station associated with an AP transfers association to another-possibly the same-AP. Also commonly referred to as a “hand-off.”
[0056] RF Monitor Mode: As used herein, a mode for a station during which a wireless network device listens to all MAC frame types (control, management and data) regardless of the AP from where the frames originate or belong to. This means that, if the radio module is in an area covered by more than one AP, it will listen to the traffic broadcast in each AP or wireless network. The purpose of this mode is essentially to enable a wireless station to “scan” for broadcasts from APs, e.g., the broadcast of beacons in the IEEE 802.11 standard, in order to locate an AP with a good enough signal strength with which to associate. It is assumed that one or more of the wireless network device or devices used in embodiments of the invention have an RF monitor mode or equivalent. Note that the process of listening for-beacons is called “passive scanning” in the IEEE 802.11 standard. IEEE 802.11 beacons contain information about the access point, including the service set identifier (SSID) of the WLAN of the AP, supported data rates, and so forth. In a normal IEEE 802.11 scan, the wireless network device provides this information along with the signal strength to compare access points and decide upon which one to associate with. A wireless network device in RF monitor mode can receive from more than one AP, but not transmit information. Other modes include send-receive mode, also called station mode.
[0057] Router: A router is a device implementing IP that forwards IP packets not explicitly addressed to itself.
[0058] Router Advertisement: An IP packet, in particular an ICMP IP packet periodically broadcasts to all nodes on the network served by a router. In the Mobile IP support provided by IPv4, extensions to the advertisements, referred to as to Agent Advertisements, carry information identifying the router as a foreign agent and/or a home agent.
[0059] Send-Receive Mode: In the IEEE 802.11 standard, the communication state wherein a station is able to communicate bidirectionally with its associated AP. Also called station mode. See also RF Monitor mode.
[0060] SSID: In the IEEE 802.11 standards, a Service Set Identifier of a wireless local area network. In a simple infrastructure network (BSS), the SSID also identifies the AP. The SSID is sometimes called the wireless network identifier. Many wireless network devices for the IEEE 802.11 standard give a special meaning to a SSID with zero length, called the broadcast SSID. If requested to associate with the broadcast SSID, the station will go to RF monitor mode and scan for all the 802.11 broadcast beacons containing an SSID. In the prior art, the station may then associate with the first AP it finds independent of any L3 information such as whether or not the AP is in communication with a mobility agent.
[0061] Station (STA): A node of a wireless network conforming to one of the IEEE 802.11 standards, in particular, a device that contains an IEEE 802.11 conformant medium access control (MAC) and physical layer (PHY) interface to the wireless medium. In the context of the present invention, a station includes a wireless network device that, after associating with an access point of a wireless network, provides a bi-directional interface to that wireless network.
[0062] Visited Network: In Mobile IP, a network other than a mobile node's home network, to which the mobile node is currently attached. When attached to a foreign network, the node is said to be “visiting” that network.
[0063] Wired Equivalent Privacy (WEP): An 802.11 security protocol for wireless networks. The WEP encryption method is designed to provide security.
[0064] Wireless Network device: A device that includes a wireless transceiver, i.e., a wireless receiver and a wireless transmitter, and capable of bi-directional wireless communication. For purposes of the invention, a wireless network device can operate in RF Monitor mode prior to the station containing the wireless network device associating with a wireless network. A wireless network device after associating with an access point of a wireless network, provides a bi-directional interface to that wireless network.
[0065] WLAN: Wireless Local Area Network, e.g. a wireless network conforming to one of the IEEE 802.11 standards.
[0066] Note that Mobile IP and 802.11 use different terminology and nomenclature for similar network components. For example, Mobile IP refers to a Mobile IP-enabled network node as a “Mobile Node.” IEEE 802.11 defines two types of stations: a “mobile” station, able to communicate while in motion, and a “portable” station able to communicate only while at a fixed location. The term Mobile Node when referring to a wireless station means a wireless station that is Mobile IP enabled and that is either an IEEE 802.11 “mobile station” or an IEEE 802.11 “portable station” in the case the station conforms to one of the IEEE 802.11 standards.
SUMMARY OF THE INVENTION
[0067] Described herein is a method operating in a wireless station having a wireless network device capable of providing a link-layer interface to a wireless network. The method operates at the link layer (L2) of a multi-layer network protocol and includes, 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 of one or more wireless networks that the station can hear. The method further includes gathering information about the received L2 data units, including L2 information and L3 information. The L3 information gathered at L2 includes 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. In one embodiment, the method further includes storing information about the wireless networks that the station can hear in a database, including L3 information from the one or more mobility agents. In one embodiment, the one or more wireless networks whose APs transmit L2 data units conform to one of the IEEE 802.11 standards. The information stored about each wireless network includes one or more of 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.
[0068] One apparatus embodiment described herein is a wireless station that includes having a wireless network device capable of providing a link-layer interface to a wireless network and the implements the method described above in this Summary section.
[0069] One carrier medium embodiment described herein is a carrier medium carrying one or more computer readable code segments that when executed on a processor implement the method described above in this Summary section.
DESCRIPTION OF THE DRAWINGS
[0070]
[0071]
[0072]
[0073]
[0074]
[0075]
[0076]
[0077]
DETAILED DESCRIPTION
[0078] The present invention provides a mechanism for a station of a wireless network to gather information at L2, prior to associating with an AP, about APs it can “hear,” including both L2 information and such L3 information as whether or not an AP is forwarding one or more mobility agent advertisements. This information can be used to emulate, at L2, one or more interfaces to one or more WLANs as if the station was associated to the WLAN, without there necessarily being any association with any WLAN, e.g., prior to associating with any WLAN, where an interface in this context means the STA's attachment at L2 to a WLAN. Such an emulated interface is also called a floating interface herein because there is not necessarily any association yet.
[0079] In one aspect of the invention, a floating interface can be presented to L3 in the same manner as an actual interface, so that L3 can perform such functions as mobility agent discovery in the same manner with floating interfaces as with actual interfaces. For example, the gathered information can be provided to the network layer (L3) of the STA. L3 can decide to respond at L3 with another entity that provides mobile IP services. Such a response can then cause the STA to associate with an AP that can communicate with that other entity, for example so that the STA can provide or benefit from mobile IP services. The STA's associating with such an AP converts the emulated interface to an actual interface to a selected WLAN.
[0080] In one application, a STA that provides routing can be a mobile router by being associated with an access point that is in communication with one or more foreign agents or MIPv6 access routers. Similarly, a STA can be a foreign agent if it is associated with an access point that is in communication with one or more home agents.
[0081]
[0082] Network
[0083] Also connected to network
[0084] Foreign agent traffic to and from FA1 and FA2 to WLAN1 is via the link
[0085] The dotted lines
[0086] The following scenarios describe various outcomes of association and re-association for a prior-art system.
[0087] Case 1
[0088] To illustrate a positive case, assume that a Mobile IP-enabled STA at location A1 seeks to associate with an AP, and is scanning for beacons. In this example, location A1 is within the coverage area of AP1, but outside the coverage areas of AP2 and AP3. Thus, the STA detects the beacon from AP1, and associates with it. Eventually, L3 at the STA detects foreign agent advertisements from either FA1 or FA2 sent via AP1, which triggers the STA's Mobile IP capabilities, enabling it to register with either foreign agent FA1 or FA2. If the STA is a router with Mobile IP capabilities is can then be a wireless mobile router.
[0089] Case 2
[0090] Assume a Mobile IP-enabled STA at location A2 seeks to associate with an AP, and is scanning for beacons. In this example, the STA is within the coverage area of both AP1 and AP2. Assume that the STA is just as likely to hear the beacon from AP1 as from AP2. If the STA hears the beacon from AP1 first, events proceed as in case #1. However, if the STA hears the beacon from AP2 first, it associates with AP2. Because local router
[0091] Case 3
[0092] Assume a Mobile IP-enabled STA at location A3 seeks to associate with an AP, and is scanning for beacons. In this example, the STA is within the coverage area of AP1, AP2, and AP3. Assume that the STA is just as likely to hear the beacon from any one of the these APs. If the STA hears the beacon from AP1 or AP3 first, because these two APs send FA advertisements from FA1 and/or FA2, events proceed similar to case 1. However, if the STA hears the beacon from AP2 first, it associates with AP2. Because local router
[0093] Case 4
[0094] Assume that a Mobile IP-enabled STA at location A1 has established an association with AP1, and is currently enjoying the benefits of Mobile IP services of FA1 or FA2. Now assume that the STA physically relocates to any of the other indicated positions. Since the STA will re-associate with the first AP whose beacon it receives, it will re-associate with AP2 roughly 40 percent of the time, thus losing its communication with a foreign agent.
[0095] The resulting behaviors in cases
[0096] In a prior art system, the criteria by which a station selects an AP for association and re-association occurs entirely at the STA's link layer (L2). There is a need to intercept this process and pass information to the station's L3 so that the station may select an AP for association and re-association based upon network-layer requirements instead of merely link-layer logic.
[0097] Providing Floating Interfaces
[0098] One embodiment of the invention includes the station, in RF monitor mode, screening all the frames the station can hear, examining the beacons that contain the AP's SSID, extracting from the PHY sublayer the RSSI (Received Signal Strength Indicator), and building a list of the available APs. In one embodiment, this screening is implemented as a module of the protocol stack operating for the wireless network device and in another embodiment by a user-level computer program. The program accesses and configures the protocol stack via a command line interface (CLI). For example, in the case of the STA operating under a networked operating system, such as the Cisco Internetworking Operating System (IOS®) (Cisco Systems, Inc., San Jose, Calif.), IOS provides a command line interface (CLI) for carrying out many network management functions.
[0099] The program or module operates at L2. For example, in the case the process forms part of the L2 layer of the stack, the process reads L3 packets in the L2 frames, and can pass the L3 contents of MAC level broadcasts, such as IP IRDP packets used to advertise a foreign agent, to the L3 layer.
[0100] Thus, one embodiment of the invention is a method for a station to identify and gather information about the APs that its wireless network device can hear on the WAN prior to association with any AP. In one embodiment, the information is available to any process at the station, e.g., L3 at the station. The information includes IP mobility information, e.g., whether the AP is sending mobility agent advertisement. In one embodiment, the information is used to build a set of one or more floating interfaces to available WLANs, in the form of APs for association. An L3 process can then select from among the available APs using one or more criteria. For example, the L3 process can then select an AP that is in communication with one or more Mobility Agents or an AP that meets some signal strength criterion or a combination of criteria.
[0101] An illustrative example of a network topology in which the invention can operate is shown in
[0102]
[0103]
[0104] If the event is a new frame arriving, the new MAC frame arriving is read at L2 in a step
[0105] Included in each MAC frame is additional information, for example the SSID of the WLAN, i.e., the identifier of the AP that originated the packet. Also provided, for example by the wireless network device as ancillary information, is an indication of the quality of the wireless signal at the time the MAC frame was received. The L2 frames may have L3 information encapsulated, e.g., in the form of IP packets. For example, the IP packet may include a mobility agent advertisement such as a foreign agent advertisement or a home agent advertisement.
[0106] Without benefit of the present invention, the link layer prior to association of the STA, e.g., while in RF monitor mode would not concern itself with any encapsulated L3 information such as mobile IP information. In one aspect of the present invention an L2-level process “peeks” inside the payload portion of each just-received L2-frame in order to collect L3 information such as Mobile IP information. In one embodiment, the collecting of L3 information includes ascertaining whether the frame encapsulates information from a mobility agent, and, if so, whether that information contains a mobile agent advertisement.
[0107] In one embodiment of the invention, information about the AP that transmitted the received L2 packet is stored as a record in a data structure stored in the memory
[0108] Each record in the WLAN database includes a set of fields on information about an AP from which an L2 packet was received. In one embodiment, the information in the record includes L2 information and also L3 information that would not normally be available until after the station was associated with the AP. Each record in the WLAN database thus provides a floating interface to the WLAN via one of the APs that the station can hear. Associated with each floating interface is the WLAN and the station's wireless network device that the interface can use to establish an actual interface to the WLAN. The floating interface can be provided to the network layer (L3) at the station as if it was an actual interface to a WLAN even though there may not be association to that WLAN.
[0109] In one embodiment, each record includes an indication of the state of the floating interface from the states shown in Table 1 below.
TABLE 1 State Description of State Interface down The AP of the WLAN is not found in the wireless medium Interface up, protocol down The AP of the WLAN is found but cannot be associated with. Protocol up (mimicked) The AP of the WLAN is found and is available for association. Protocol up (real) The WLAN is currently associated with the station.
[0110] One embodiment includes the following fields in each record of the WLAN database: an identifier of the WLAN in the form of the SSID of the WLAN of the AP the frame was received from, the IP packet from the received L2 frame, a time stamp of when the frame was received, an indication of the signal strength of the frame from the AP, the state of the floating interface to the WLAN. In one embodiment, each record also includes an indication of any mobility information contained in any IP packet in the received L2 frame, e.g., of any mobility advertisement from a mobility agent.
[0111] In one embodiment, each record in the WLAN database includes a flag field that when set indicates that the record is the Most-Recently-Used-Association (MRUA) record. The MRUA always holds the record for the AP that was used for the most recent association or re-association. The MRUA record is never evicted from the WLAN database, for example to create space for more records.
[0112] In an alternate embodiment, the WLAN database includes a field that indicates the N-last associations with APs that wirelessly transmitted mobility information from different mobility agents.
[0113] The WLAN database is searchable and orderable by one or more fields, including the time stamp and one or more of the headers in the stored L2 frame.
[0114]
[0115] In one embodiment, the STA's memory
[0116] One station embodiment includes more than one wireless device (or a device with several channels that can simultaneously provide interfaces to different WLANs) each capable of association with a WLAN, so each capable of providing an interface to a WLAN. In such an embodiment, each record in the WLAN database further includes an identifier of the wireless device that would provide the actual interface after association with the WLAN of the floating interface, and information on one or more capabilities of the actual interface to the WLAN, such as speed, latency, and so forth.
[0117] In the embodiment corresponding to the flow chart of
[0118] Returning to
[0119] If it is ascertained that the MAC frame is not a beacon and does not include a mobility agent advertisement, the process returns to wait state
[0120] Once it is ascertained that a received MAC frame contains mobility agent information, the WLAN database is updated with this information (step
[0121] In one embodiment, the ordering criteria (and/or interface selection criteria) include ordering (and/or selecting) according to one or more quality of service parameters, such as required quality of service. One aspect of the invention is that the ordering criteria (and/or interface selection criteria) include L3 information such as what mobility agent information is included. In an embodiment that further includes more than one wireless device, the ordering criteria (and/or interface selection criteria) include the capabilities of the physical interface to the WLAN, such as speed, latency, and so forth).
[0122] Thus, in one embodiment, records that include a mobility agent advertisement are given priority. In one embodiment, the ordering criteria include ordering according to received signal quality. One embodiment orders according to a combination of more than one ordering criteria, such as giving priority to those records that include mobility agent information, and further ordering such prioritized, i.e., mobility-agent-related records according to signal strength.
[0123] One embodiment of step