(12) United States Patent
`Brockmann
`
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`US006487657Bl
`US 6,487,657 Bl
`Nov. 26, 2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) DATA COMMUNICATION NETWORK
`
`(75)
`
`Inventor: Ronald Alexander Brockmann,
`Utrecht (NL)
`
`(73) Assignee: No Wires Needed, B.V., Bitthoven
`(NL)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/252,308
`
`(22) Filed:
`
`Feb. 18, 1999
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 19, 1998
`
`(NL) ............................................. 1008351
`
`(51)
`
`Int. Cl.7 ............................. H04L 9/36; H04L 9/32;
`H04K 1/10; H04H 1/12
`(52) U.S. Cl. ....................... 713/154; 713/155; 713/201;
`380/33; 380/270; 380/271; 455/3.05
`(58) Field of Search .......................... 380/33, 270, 271,
`380/277, 279; 713/154, 155, 163, 201;
`455/3.01, 3.02, 3.05, 3.06
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5/1994 Takaragi et al. .............. 380/45
`5,309,516 A
`5,539,824 A * 7/1996 Bjorklind et al. ............. 380/21
`5,668,880 A * 9/1997 Alajajian ..................... 380/49
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`
`WO 95/12942 Al
`WO 96/04734 Al
`
`5/1995
`2/1996
`
`........... H04L/12/44
`........... H04L/12/28
`
`* cited by examiner
`
`Primary Examiner-Justin T. Darrow
`(74) Attorney, Agent, or Firm-St. Onge Steward Johnston
`& Reens LLC
`
`(57)
`
`ABSTRACT
`
`The invention relates to a data communication network
`suitable for the exchange of data between computers, which
`network comprises at least one substantially wireless LAN
`(Local Area Network) and access points distributed over an
`area of coverage for linking the computers comprised in the
`minimally one LAN, with the network. The minimally one
`wireless LAN is virtual and the data traffic with the com(cid:173)
`puters belonging to that particular LAN is individualized by
`encoding the data exchanged between the computers and the
`access points by using for each LAN a unique key.
`
`5,199,072 A
`
`3/1993 White et al. .................. 380/44
`
`7 Claims, 1 Drawing Sheet
`
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`U.S. Patent
`US. Patent
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`Nov. 26, 2002
`Nov. 26, 2002
`
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`US 6,487,657 Bl
`
`1
`DATA COMMUNICATION NETWORK
`
`FIELD OF THE INVENTION
`
`The invention relates to a data communication network
`suitable for the exchange of data between computers, which
`network comprises at least one substantially wireless LAN
`(Local Area Network) and access points distributed over an
`area of coverage for linking the computers comprised in the
`minimally one LAN, with the network.
`
`BACKGROUND OF THE INVENTION
`
`2
`wireless LAN is controlled by the control module and for
`each user module a unique identification number is
`employed, which information is stored in the memory of the
`control module. Prior to permitting network access the
`5 control module verifies the identification of the requesting
`user module. The users that are active in a certain geographi(cid:173)
`cal area, form part of a group sharing the same control
`module and when the mobile users are roaming, a transfer of
`the user concerned from one user group to the next is
`10 required, necessitating the assignment of a new password
`into the user module seeking access into the next user group.
`According to U.S. Pat. No. 5,199,072 a particular user is,
`however, not able to roam from one area to the other whilst
`maintaining membership to one particular virtual LAN.
`
`SUMMARY OF THE INVENTION
`
`It is the object of the invention to provide a system in
`which the data communication network can be used whilst
`being able to encompass several wireless LANs, without
`unduly aggravating the control problem with respect to the
`data traffic in the system, and without requiring concessions
`with regard to the mobility of the various computer users
`who are part of a wireless LAN.
`According to the invention the data communication net(cid:173)
`work is therefore equipped such that the minimally one
`wireless LAN is virtual and that the data traffic with the
`computers belonging to that particular LAN is individual(cid:173)
`ized by encoding the data exchanged between the computers
`and the access points by using for each LAN a unique key.
`In one preferred embodiment therefore every computer is
`provided with its own unique key. In this manner point-to(cid:173)
`point data links can be established between the various
`computers wirelessly encompassed in the network and the
`access points. To this end, data encoding techniques may be
`applied that are generally known from the literature. The
`only prerequisite being, that the keys applied are capable of
`distinguishing the individual data links between the respec(cid:173)
`tive computers and the access points. By providing said
`keys, the respective access points can be equipped such that
`they recognize to which virtual LAN or virtual LANs they
`belong and also, to which LAN the computers sending
`and/or receiving data to and from said access points, belong.
`The various keys may be determined beforehand for each
`LAN.
`In one particular embodiment, however, it is advanta(cid:173)
`geous that the data communication network is equipped to
`generate the unique key the moment that data traffic between
`one or more computers from a LAN and the network is
`established. This is advantageous with regard to controlla(cid:173)
`bility.
`One suitable embodiment endowed with the necessary
`guarantees regarding authentication of the data traffic, is
`characterized in that the generation of the unique key occurs
`with the public-key algorithm, which is known as such; see
`W. Diffie and M. E. Hellman, "New Directions in
`Cryptography", IEEE Transactions on Information Theory,
`v.IT-22, n. 6, November 1976, pp. 644-654.
`Advantageously, the access points are among themselves
`linked to wired network connections that are known as such.
`However, this is not a prerequisite; the network connections
`may also be wireless.
`In order to restrict the load constituted by the data traffic
`in the data communication network according to the
`invention, it is desirable that every access point possesses a
`filter unit for deleting data destined for a computer belong(cid:173)
`ing to a LAN other than the one present in the area of
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`PayPal Ex. 1039, p. 3
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`Such a data communication network has been known in
`practice for years. The wireless local area network (LAN)
`comprised in such a data communication network is
`designed to provide a great degree of flexibility, mobility
`and to lower the otherwise necessary costs for infrastructure
`and control. Such a wireless LAN may include a laptop
`computer equipped for wireless communication. In order to
`provide the communication function, the network is
`equipped with so-called access points which are set up in the
`geographical area served by the wireless LAN. Usually an
`access point serves a small area called Cell, having a radius
`of between 10 an 100 metres. Therefore, for serving a
`somewhat extensive area of coverage, the application of
`several access points is required. Among themselves, these
`access points are linked by means of network techniques
`which are known as such, and which may or may not be
`wired, such as for example, the ethernet infrastructure.
`The data communication network forming the object of
`the present invention, comprises at least one wireless local
`area network, and may otherwise be wired for linking with
`possibly further virtual local area networks, for example, in
`accordance with the IEEE 802.lQ standard for virtual LANs 35
`or, similarly, as known from W096/04734. When such a data
`communication network provides the possibility of applying
`several wireless local area networks, a problem arises that is
`intrinsic to the type of wireless communication. When
`computers from different local area networks operate in the 40
`same geographical area it is, in view of the fact that wireless
`communication takes place via the ether, very difficult to
`maintain the integrity of the data traffic in the respective
`local area networks according to the prior art.
`There are various solutions to this problem. On the one 45
`hand, the number of access points may be enlarged in
`concurrence with the number of local area networks present
`in a certain area of coverage; however, this is very costly and
`with respect to the utilization of the available transmitter
`frequencies, very inefficient. Another solution is not to 50
`increase the number of access points, but to restrict the
`mobility of the computers in local area networks. However,
`instead of solving a problem it merely avoids a problem.
`Another possibility is to abandon the idea of the smaller
`local area networks and to equip the system as one integral 55
`network. This would indeed avoid the indicated problem,
`but would create problems relating to the security of the data
`traffic, and will produce an exponential increase of the
`control problem. Accordingly, the performance of the sys(cid:173)
`tem will deteriorate because data which is destined for a 60
`limited number of computers, will be sent to every-one.
`U.S. Pat. No. 5,199,072 concerns wireless local area
`networks and means for restricting access within such
`networks. The wireless LAN according to this publication
`utilizes a control module to control communication with 65
`user modules that are linked with such devices as terminals,
`personal computers and similar equipment. Access to the
`
`

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`US 6,487,657 Bl
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`3
`coverage of that particular access point, or which stems from
`a computer of a first LAN while being destined for a
`computer of a second LAN. In addition, this guarantees the
`virtual star structure of the network.
`With a view to data traffic security it is desirable that the
`filter unit be equipped to delete from the data traffic prede(cid:173)
`termined types of data, for example, data that could be
`classified as infringing the security or integrity of a network
`or a part thereof. This may be of particular importance with
`regard to data exchange in a WINDOWS-NT environment.
`To further serve the controllability of the system, every
`computer in a wireless LAN is provided with a device for
`rejecting messages sent by other computers. This procedure
`effectively provides a star structure between the various
`access points and the computers communicating with said
`access points.
`It is further desirable that each computer be provided with
`one or more additional keys for encoding and decoding the
`data traffic destined for a group of computers, or for all
`computers in the same virtual LAN. In addition to the
`point-to-point data message communication on an indi(cid:173)
`vidual basis, the virtual LAN would then also provide the
`possibility of multipoint message communication and
`broadcast message communication.
`Application of the invention is possible by using the
`standard IEEE 802.11 technology for wireless local area
`networks. By applying the invention, the respective wireless
`virtual local area networks are distinguished and separated
`from each other, without the risk of data traffic arriving at
`any other than the intended destination. The invention
`enables the computer users within the various local area
`networks to move about freely within the area served by the
`various access points.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The FIGURE is a representative block diagram of a data
`communication network in accordance with the invention.
`The invention will now be further elucidated with refer(cid:173)
`ence to a single drawing which schematically shows the data
`communication network according to the invention.
`The data communication network shown is suitable for
`data exchange between computers, each of which is indi(cid:173)
`cated by the term "station". The data communication net(cid:173)
`work shown comprises, at least in the portion shown, two
`virtual local area networks indicated by VLAN 1 and VLAN
`2. The virtual local area networks VLAN 1 and VLAN 2 are
`linked with the network via data traffic through the ether,
`taking place with the aid of an access point, indicated as such
`in the FIGURE. According to the invention, the data traffic
`between such an access point and the computers "station" is
`encoded by means of a key code which, in the case
`illustrated, is unique for each computer, whereby an indi(cid:173)
`vidualized link is provided between each computer "station"
`and the respective access point. Another possibility is to
`apply such a unique key code only per LAN, so that all
`computers of that particular LAN are able to participate in
`the data traffic. The unique key is, for example, determined
`for each LAN or computer before-hand. Another possibility
`is to postpone the determination of the unique key until the
`moment that data traffic between one or more computers
`from a LAN and the network is imminent. Generation may
`then be effected by means of a public-key algorithm. Such
`public-key algorithms are known to the expert and require
`no further explanation.
`The FIGURE shows further that the respective access
`points are interlinked by means of wired network links
`which are known as such, and called "wired backbone". To
`make effective use of the data communication network
`
`30
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`4
`without over-loading by excessive data traffic, each access
`point is provided with a filter unit for deleting any data
`destined for a computer of LAN VLAN 1 or VLAN 2
`respectively, other than the one present in the respective area
`5 of coverage (Cell Aor Cell B) of that particular access point.
`The filter unit is also equipped to delete data sent from a first
`LAN and destined for a computer of a second LAN. The
`result is a logical separation of the VLANS. Said filter unit
`can also delete specific types of data. Furthermore, every
`computer "station" is equipped with an element for rejecting
`10 data sent by another computer "station". In this manner the
`data network acquires a star structure.
`Thanks to the virtual and wireless character of the local
`area networks applied in the network according to the
`invention, a computer station forming part of local area
`15 network VLAN 2, may be moved from the one area of
`coverage Cell A to an area of coverage Cell B, served by
`another access point, without losing the integrity of a local
`area network. Thus the advantage of the invention is that,
`despite the use of wireless computers "station" together with
`20 virtual local area networks, the advantages associated with
`said latter technique, namely improved controllability of the
`data traffic in the data communication network is realized
`without conceding anything to the mobility of the computers
`used in the network. Thanks to the filter units provided in the
`25 various access points forming part of the network, the speed
`of the data traffic in this network, and the logical separation
`of the LANs is guaranteed.
`What is claimed is:
`1. A data communication network suitable for the
`exchange of data between computers, which network com(cid:173)
`prises at least one substantially wireless LAN (Local Area
`Network) and access points distributed over an area covered
`by the network for linking the computers with the network,
`wherein the data traffic with the computers belonging to the
`wireless LAN is individualized by encoding data exchanged
`35 between a computer and its access point with a unique data
`key that defines the wireless LAN within the network,
`characterized in that the wireless LAN is virtual, and that
`every access point possesses a filter unit applied to unique
`keys associated with data traffic for excluding data destined
`40 for a computer belonging to a LAN other than computers
`that are a part of the virtual LAN accessible through the
`particular access point associated with the filter unit.
`2. A data communication network according to claim 1,
`characterized in that the filter unit is equipped to delete from
`45 the data traffic predetermined types of data.
`3. A data communication network according to claim 1,
`characterized in that every computer in a wireless LAN is
`provided with a device for rejecting messages sent by other
`computers.
`4. A data communication network according to claim 1,
`characterized in that each computer is provided with one or
`more additional keys for encoding and decoding the data
`traffic destined from a group of computers, or for all
`computers in the same virtual LAN.
`5. A data communication network according to claim 1,
`55 characterized in that every computer is provided with its
`own unique key for data communication with an access
`point.
`6. Adata communication network according to claim 1 or
`2, characterized in that the data communication network is
`60 equipped to generate the unique key at a time when data
`traffic between one or more computers from a LAN and the
`network is established.
`7. A data communication network according to claim 6,
`characterized I that the generation of the unique key occurs
`65 with a public key algerithm.
`
`50
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`* * * * *
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`PayPal Ex. 1039, p. 4
`PayPal v. IOENGINE
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