WO2008028919A1

WO2008028919A1 - Connectable network equipment for wireless network in infrastructure mode

Info

Publication number: WO2008028919A1
Application number: PCT/EP2007/059259
Authority: WO
Inventors: Guillaume Bichot
Original assignee: Thomson Licensing
Priority date: 2006-09-05
Filing date: 2007-09-04
Publication date: 2008-03-13
Also published as: FR2905547A1

Abstract

An item of network equipment comprising or forming an access point AP3 of a wireless network WLAN4 comprises means potentially capable of instantiating a wireless network interface STA10-NIU, IS1NIU, IS2-NIU per client, terminal STA10 or intermediate IS1-NIU, IS2-NIU station of the wireless local network WLAN4. There can thus be as many network interfaces as there are wireless stations connected. The inter-network bridge function 30 manages each of these wireless network interfaces instantiated according to the invention as an ordinary network interface.

Description

CONNECTABLE NETWORK EQUIPMENT FOR WI RELESS NETWORK IN

INFRASTRUCTURE MODE

1. Technical Field. The present invention relates to the field of wireless local area networks WLAN, and more particularly the access point topology of such networks operating in infrastructure mode.

2. Technological background. Different wireless local area network WLAN technologies have been developed, notably including the WI-FI technology based on the IEEE 802.1 1 standard. Other technologies exist, such as WiMAX for example (IEEE802.16).

The infrastructure mode is an operating mode that enables stations equipped with an ad-hoc network card, a WI-FI card for instance, to be connected together via an access point. The access point is thus a necessary passage for communication.

An example of a wireless local area network WLANi in infrastructure mode according to the prior art is shown in figure 1a. It comprises an access point APi with a wireless network card 10 with a radio transmission/reception antenna in an area of coverage 1 1 and client stations

STA₁ , STA₂, STA₃, STA₄ located in this area of coverage.

For example, STAi is a laptop computer, STA₂ is a camera, STA₃ is a video monitor, and STA₄ is a telephone. In a business context, this could basically be computers and telephones.

In the rest of the document, the wireless local area network WLANi is merged with the set formed by the access point APi and its client stations STA₁ located in the area of coverage 1 1 . In the literature, this set is also called the Basic Service Set BSS, or cell. Similar architectures are disclosed in patent documents:

- US7, 099,295 B1 , that illustrates a bridging between a wired network and a wireless network, each radio interfaces being linked to several devices; - US5,546,397 that illustrates a reliable access point for a wireless LAN; and

- US2003/01 12820A1 that discloses a secure wireless LAN, wherein each port relays communications to the mobile units in a cell.

As shown in figure 1b, the access point APi comprises a corresponding wireless network interface unit WLAN-NIU for the WLANi network. This interface comprises in a usual manner the wireless network board 10, with its transmission/reception antenna and a driver or corresponding card "driver", and a bridge function 12 implemented in a software manner to transmit messages between the STA, client stations of the WLANi network.

In a known manner, bridge is understood to mean a function that provides the media access control, corresponding to the data link layer of the media.

If the example of a Wi-Fi network is taken, the well known standard 802.1 1 defines the low layers of the OSI model (Open Systems Interconnection), namely the physical layer of level 1 , and the data link layer of level 2, split into two sublayers the logical link control sublayer and the Media Access Control MAC sublayer. A bridge is a software or hardware function that handles data frames according to the source and destination MAC addresses specified in the header of the frames that it receives from source station, to the destination station.

The access point of a wireless network thus implements a function that allows the client stations of the wireless network considered to communicate with each other through the wireless network interface unit.

This wireless network bridge mechanism is specific to the wireless network.

Indeed in a wired local network (for example an Ethernet local network), two stations in a same wireline local network communicate with each other directly.

Originally, the client stations of a wireless local network were designed to be terminal stations ("end-user station"). This means that the stations were not intended to be connected to other network equipment irrespective of the means. As needs have changed, new technologies have been developed such as the WIMAX (Worldwide Interoperability for Microwave Access) technology based on the standard IEEE 802.16, enables other architectures to be considered, particularly with the purpose of extending the network communication coverage. We notably speak of an extended wireless network. These technologies enable different networks to be linked together by access points. A Wimax access point thus comprises, in addition to its wireless network interface, several other network interface units or NIUs. It also implements an inter-network bridge that can direct data from one port to another according to the MAC addresses.

If figures 1 a and 1 b are considered, the access point AP₁ is thus an item of network equipment of the "WIMAX" type that performs an internetwork bridge function between at least the WLANi wireless network and another LANi local network. In the example shown, the local network LANi is a wired network, for example an Ethernet network, to which a station STA₅ is connected, for example a video server.

In a known manner, the access point AP-i comprises or implements for each network interface unit, a corresponding driver to control the hardware interface associated in a suitable manner and an inter-network bridge or inter-NIU bridge function between the different NIU network interface units. In the example, we therefore have an inter-network bridge 20, to manage the MAC frames between the wireless network interface WLAN- NIU and the LAN₁-NIU interface, through their respective drivers. This bridge 20 is implemented in a software manner by the operating system of the AP₁ equipment. In one example, if the operating system of the access point AP₁ is an open system such as for example the Linux or Windows system, namely which offers the possibility of implementing new functions, the bridge 20 is implemented in a typical manner by the kernel of the operating system, and implements for example the different functions contained in the standard IEEE 802.1 , and notably the STP protocol known as "Spanning Tree Protocol, by means of which a loop-free network topology as defined in the standard IEEE 802.1 D can be provided

The inter-NIU bridge 20 cannot provide the wireless network dedicated bridge function 12, owing to the management mechanism specific to the wireless network Indeed, as soon as the wireless network card is inserted into the APi equipment, the operating system opens or enables the corresponding wireless interface unit WLAN-NIU. This interface unit is common to all the client stations of the WLAN₁ network thus activated. Now, the inter-NIU bridge 20 only enables incoming messages to be forwarded on a network interface to another separate NIU interface. Indeed, this bridge function for managing the different network interfaces is based on a communication protocol of the wired networks. According to this well known protocol, all the stations of a same local network listen to the network. If one of them is recognised as being the destination of a message on the network (recognition of the destination MAC address), it shows itself. Therefore, if the message arrives at the access point via the interface of this network, this means that no station of this network is recognized and that the message is intended for a station of another network. Either the bridge knows to which network the destination station belongs by its routing table, and it transmits the message to the corresponding network interface, or it does not know, and it transmits the message on all the other network interfaces. But in no case does it send back the message on the interface from which it received the message. The inter-NIU bridge cannot therefore direct messages received from the WLAN-NIU interface on this same WLAN-NIU interface. For this reason and as shown in figure 1 b, the AP1 equipment must implement the inter-network bridge 20 at the system level, and the bridge 12 inherent to the wireless network, at the level of the wireless network interface WLAN-NIU. This "wireless" bridge 12 is exclusively dedicated to the wireless network interface WLAN-NIU and only relays the data on the basis of the MAC addresses between the client stations of the wireless network. Figure 2 shows the case of more complex infrastructures, in which terminal stations are connected to the wireless network by intermediate stations. To describe the infrastructure, pure convention considers that there is a descending hierarchy from the access point. With this convention, in the example illustrated in figure 2, a wireless local network WLAN₂ comprises an access point AP₂, and two intermediate stations IS1 and IS₂. The intermediate station IS₁ is an access point of another wireless network WLAN₃ to which two wireless stations STA₆ and STA₇ are attached. The intermediate station IS₂ is connected to a wired subnetwork LAN₂, to which other stations STAs and STAg are also connected. These stations ST AQ to STAg, are terminal or "end-user" stations. The intermediate stations implement a bridge function, for example by the kernel of their operating system, to relay the frames according to their MAC address between terminal stations.

In such an infrastructure, the bridge function 12 of the access point AP₂ dedicated to the wireless network interface WLAN-NIU is more complex than the previous case shown in figure 1a, as it must process hidden nodes, namely the terminal stations STA₆ to STAg which are found behind the intermediate stations IS₁ and IS₂, and that cannot be seen directly by the access point AP₂. Moreover, in this case, the intermediate stations act as a link (node) between two local networks, in the example, between the WLAN₂ wireless network and the wired network LAN₂, or wireless WLAN₃, there is a known risk of loops, which could paralyse the network by a phenomenon known as "broadcast storm". For this reason, the bridge function 12 of the wireless interface of the access point AP₂, must itself implement the STP protocol specified above (standard IEEE1.D), implemented in the inter- network bridge 20.

The two examples of network infrastructure with WIMAX type access points that have just been described, show that the two-bridge structure, an inter-network system bridge 20 and a dedicated wireless bridge 12, that are implemented in the access point AP₂ (or in an item of network equipment comprising this access point) is not optimal and can even become complex in the case of a network hierarchy infrastructure, where the wireless network comprises intermediate stations. 3. Summary of the invention.

In the invention, an attempt is made to simplify the design of these extended network infrastructures. A technical solution that was simple to implement, evolutive and reliable was sought to manage within the access point all the examples of message direction by the same bridge function, including in the event of subnetworks attached to a wireless network, the idea being to remove the bridge function dedicated to the wireless network implemented in the wireless network interface and/or the associated driver. According to the invention, an item of network equipment comprising or forming an access point of a wireless network comprises means potentially capable of instantiating one wireless network interface per client, terminal or intermediate station of the wireless local network. There can thus be as many network interfaces as there are stations of the wireless network. The inter-network bridge function manages each of these wireless network interfaces instantiated according to the invention as an ordinary network interface. Notably, it can direct frames sent by one station of the wireless network to another station of this wireless network, as it sees them as two separate network interfaces. Through this mode of instantiation of a plurality of wireless network interfaces for a single wireless network, one thus resolves the contradictory operating mode of the two bridge functions according to the prior art.

Advantageously, a dynamic management of these network interfaces is implemented according to the connections and/or disconnections of the stations of the wireless network.

Moreover, each wireless network interface instantiated comprises a driver that can understand the functionalities specific to the client station. Particularly in the case of an intermediate station, the driver can understand the functionalities specific to this intermediate station. The invention therefore relates to network equipment connectable to local networks, at least two, forming at least one access point to a wireless local network, at least one first network interface port enabling a connection to a local network, characterized in that the said access point comprises a plurality of wireless network interface ports associated with the said wireless network, each one of the said wireless network interface ports being associated with at least one client station of the said wireless network, and an inter-network bridge associated with at least the said first network interface port and the said plurality of wireless network interface ports.

In one advantageous variant, the access point is a router and enables several IP subnetworks, one per client station, to be associated with the said wireless network. The invention also relates to a method of communication between corresponding local networks.

4. Brief description of the drawings.

Other advantages and characteristics of the invention are described in the following description in reference to the illustrated drawings of an embodiment of the invention, provided as a non-restrictive example. In these drawings:

- figures 1 a and 1 b already described show a wireless network topology in infrastructure mode with an access point enabling a connection to at least one other network according to the prior art, - figure 2 already described shows an extended wireless local network with an access point according to the prior art,

- figure 3 shows an extended wireless network topology with an access point according to the invention,

- figure 4 is a block diagram showing a method of dynamic instantiation of a wireless network interface according to the invention,

- figure 5 is a diagram showing an application of the invention to a system in which the subnetworks are IP networks and the connectable equipment forming or comprising the access point is a router, and

- figure 6 shows in a simplified manner an IP routing mechanism applicable to the invention.

5. Detailed description of the invention. Figure 3 shows an access point according to the invention in an extended wireless network topology.

In this example, the wireless local network WLAN₄ comprises an access point AP₃, a terminal station STA₁₀, for example a laptop computer, and two intermediate stations IS₁ and IS₂. For these intermediate stations, the example illustrated in figure 2 has been used with the same notations. Hence, the intermediate station IS₁ is an access point of a wireless subnetwork WLAN₃ to which the stations STA₆ and STA₇ are attached. The intermediate station IS₂ is connected to a wired subnetwork LAN₂, to which are attached the stations STA₈ and STA₉.

The access point AP₃ has a network interface LAN-i-NIU with a local network LAN₁, which is wired in the example, to which a station STA₅ is connected.

The access point AP₃ also has a plurality of wireless interface units with the WLAN₄ network. In the example, there are N= 3 wireless network interface units, instantiated in a software manner, each one associated with a terminal STA-io or intermediate IS-i, IS₂, station directly in view of the access point AP₃. A station directly in view of the access point AP₃, is understood to mean the stations of the wireless network WLAN₄, such as STA₁0, IS₁ and IS₂ in the example. The stations attached indirectly to the access point AP₃, via an intermediate station, like the stations STAβ to STAg in the example, are invisible for this access point and do not cause the instantiation of a corresponding wireless interface unit in this access point.

In the example, three virtual interfaces can be instantiated: the interface STA₁₀-NIU associated with the terminal station STA₁₀, the interface IS-i-NIU associated with the intermediate station IS-i, and the interface IS₂- NIU associated with the intermediate station IS₂- Each of these virtual interfaces STA₁₀-NIU, IS₁-NIU, IS₂-NIU, is processed by the inter-network bridge 30 as a separate network interface, as soon as it is declared. Each of these network interfaces comprise notably its driver and share with the other interfaces, the wireless network card 10. The drivers D₀, D-i, D₂ of these interfaces STAi₀-NIU, IS₁-NIU and IS₂-NIU have a common part A relating to the control of the wireless network card 10 that these interfaces all share in common. Each driver can also comprise a specific part, respectively Bo, Bi, B₂, of the WLAN₄ network station corresponding to the interface considered, that is respectively STA₁₀, IS-i, IS2. This specific part of the driver advantageously exploits the special functionalities of the station with which it is associated. This is advantageously the case for the intermediate stations IS₁ and IS₂ that are each attached to another local network. For example, the intermediate station IS₁ could support a protection mechanism that is specific to it. The specific part B1 of the driver D1 of the associated interface will then comprise the corresponding functionalities. These specific parts can be enriched if necessary by new functionalities, according to the development of the stations, particularly intermediate stations. There is therefore an advantageously adaptable access point structure that can be modified according to the development of the infrastructures. In the case where the access point is a router, it is possible according to one particularity of the invention explained further on, to associate an IP address with each virtual interface and therefore each station of the wireless network. In this case, the associated driver, for example D1 comprises a specific part B1 , at least for enabling the switching of packets exclusively via the said associated client station, and possibly for implementing specific functionalities of the associated station.

Potentially, one can have at a given moment as many wireless network interface units and associated drivers as terminal and/or intermediate stations directly in view of the wireless card 10 of the access point AP₃. Advantageously, you have as many wireless interface units as stations directly in view, that are effectively connected. This functionality is advantageous as it enables at a given moment only to manage the wireless network interfaces actually used, which frees up the memory space and CPU power. This functionality is obtained simply by using the standard functionalities of the access points combined with the wireless network cards, which are capable of detecting the data sent by each of the wireless stations, indicating their active presence. In practice, when the wireless network card is activated (inserted, powered up), there is an association phase during which the stations connected to the access point are detected and the corresponding information recorded such as their MAC address. When a station exits the network, this is also detected.

The instantiation means then use this connection/disconnection information to manage the wireless network interface units dynamically: remove the units corresponding to stations that have become disconnected and/or instantiate new ones for station that have become connected. The access point AP₃ becomes comparable to a wireless dynamic switch, namely that is acts as a multi-port Ethernet switch ("multi-port bridging"), by which the ports (interfaces) are dynamically added or removed according to changes in the topology of the network.

Figure 4 diagrammatically shows the instantiation mechanism of a wireless network interface according to the invention, for a client station STA_k of the wireless network.

If the station STA_k connects, this is detected (step 100.1 a), and the corresponding information is sent to the instantiation means 100.2 of the operating system, that creates a corresponding wireless network interface unit (step 100.3a): instantiation of the port and association of the station STA_k to this port. The inter-network bridge 30 must be updated (step 100.4). An ADD command is thus sent to add this inter-network bridge 30. For example, in an access point (or connectable network equipment implementing this access point) with a Linux operating system, by using the notation "brO" to designate the inter-network bridge 30, and by assuming that the two wireless network interface units are already instantiated, noted wmaxO and wmaxi , and added to the bridge 30 (FIG.4), the ADD command will be of the type: Brctl brO addif wmax2.

The new wireless network interface unit wmax 2 is then added to the bridge 30.

If the station STA_k becomes disconnected, this is detected (step 100.1 b), and the corresponding information is sent to the instantiation means 100 2, which removes the interface unit that was associated with it (step 103 b) A DEL command is sent to remove this port from the inter-network bridge 30 (step 100 4) The DEL command will be of the type Brctl brO dellif wmax2 It will be noted that with an instantiation of virtual wireless network interface units according to the invention, if no wireless network station is effectively connected to the network, no interface unit is created One can therefore have at a given moment for the wireless network WLAN₄ 0 instantiated wireless network interface units, or n instantiated wireless network interface units, n non-null integer In practice, the number of wireless network interface units that can be instantiated at a given moment can be limited, basically according to the data processing and memory capacities of the access point In this case, at step 100 2, the access point can check the current number n of instantiated ports and if the limit is reached, refuse the request In this case, the station STA_k is refused its connection to the wireless network WLAN₄

The invention advantageously offers the possibility of IP routing (Internet Protocol) within a same wireless local network where the access point AP₃ is a router, namely that is able to carry out the IP routing of data between the different stations attached to this wireless network This particularly interesting aspect of the invention enables an IP subnetwork to be associated with each wireless interface unit instantiated and associated with a station of the wireless network WLAN₄ It is thus possible to share this wireless network WLAN₄ in several IP subnetworks In particular, there can be one IP subnetwork per intermediate station of the wireless network

This aspect of the invention is more particularly described below in relation to figure 5

The access point AP₄ comprises a router bridge 3OR in addition to the inter-network bridge functions, it implements the functions 200 of IP packet switching between the different interface unit instantiated in the access point To be able to create a corresponding IP routing, an IP address is attached to each of the intermediate or terminal stations of the network WLAN₄ at the level of the access point AP₄.

It is recalled that an IP address is formed by an IP network or subnetwork address and a MAC machine identification part.

The router access point AP₄ associates an IP subnetwork identifier with each instantiated port and in particular with each new wireless interface unit instantiated for the network WLAN₄. For these wireless interface units instantiated for the WLAN₄ network, the machine identification is the machine identification MAC-WLAN₄, of the wireless network card 10 that manages the WLAN₄ network.

For each incoming packet in the access point AP_4, the router bridge 3OR analyses the destination IP address in each packet that enters, and according to the network or subnetwork identifier part, sends the packet to the corresponding interface unit.

Hence, in the example illustrated in figure 5, the following situation arises. An IP subnetwork, IP-O, corresponds to the intermediate station ISi as well as the terminal stations ST₆ and ST₇ that are attached to it.

An IP subnetwork, IP-1 , corresponds to the intermediate station IS₂ as well as the terminal stations STs and STg that are attached to it. Each station associated with the IP subnetwork considered IP-O or IP-1 has a corresponding IP address in this network. For example, the station STA₆ has the address IP-00.

The LANi network is associated with an associated IP subnetwork, IP-2 and the station STA₅ with the address IP-20 in this subnetwork IP2.

An IP address, IP-3, corresponds to the station STA₁₀.

An example of IP routing illustrates diagrammatically in figure 6 a management of the IP layer by the inter-network router bridge 3OR. In a step 200. a implemented by the routing functions 200, the inter-network router bridge 3OR detects the destination IP address, for example the IP-10 address, in each packet of data transiting by the access point AP₄, for example in an data packet entering through the wireless network interface unit IS1 -NIU. In a next step 200. b, it searches, for example in a routing table IP TAB that it keeps up to date, for what IP subnetwork and hence what network interface this IP address corresponds to, in order to send it to this interface (step 200c). In the example, it finds that the address IP-10 belongs to the subnetwork IP-1 , and send the data packet to the corresponding network interface unit, IS2-NIU in the example.

In this context, it will be noted that each of the virtual interfaces instantiated for the wireless network WLAN₄, and attached to a station of this network, for example ISi-NIU thus comprises in its driver D1 , in addition to the part A common to all the instantiated ports for the wireless network WLAN₄, a specific part B1 of the said station, at least to enable the switching of the IP packets from or to this station. Reference should be made to what has been described above concerning the drivers of the virtual interfaces. The invention applies to all the network topologies comprising one or more wireless networks in infrastructure mode, without being restricted to specific network standards.

It enables extended network topologies to be considered, to which it brings flexibility and adaptability. It applies especially to the WIMAX technology.

Claims

1. Network equipment connectable to at least two local networks, said network equipment forming at least one access point (AP3) to a wireless local network (WLAN₄) and comprising at least one first network interface unit (LAN₁-NIU) enabling a connection to a local network (LANi), characterized in that the said access point comprises a plurality of wireless network interface units (STA-io-NIU, IS₁-NIU, IS2- NIU) associated with the said wireless network (WLAN₄), each one of the said wireless network interface units being associated with one client station of the said wireless network, and an inter-network bridge (30) associated with at least the said first network interface unit and the said plurality of wireless network interface units.

2. Network equipment according to claim 1 , characterised in that the said inter-network bridge (30R) implements IP routing functions

(200), and wherein the said wireless network (WLAN₄) comprises a plurality of IP subnetworks (IP-O, IP-1 , IP-3), one IP subnetwork being associated with each client station of the wireless network and with the corresponding wireless network interface unit.

3. Network equipment according to any one of the aforementioned claims, characterized in that it comprises instantiation software means (100.2) to instantiate each wireless network interface unit associated with the said wireless network.

4. Network equipment according to claim 3, characterized in that the said instantiation means are dynamic means for opening or closing wireless network interface units according to information of client station connections (100.1 a) to the said wireless network and/or client station disconnections (100.1 b) from the said wireless network.

5. Network equipment according to any one of claims 1 to 4, in which each wireless network interface unit (STA₁₀-NIU, IS₁-NIU, IS₂-

NIU) instantiated for an associated client station comprises a specific driver (DO, D1 , D2), the said driver comprising at least one part (A) specific to the wireless network card (10) of the said access point

(AP₃)

6 Network equipment according to claim 5, characterized in that the said driver also comprises a specific part (BO, B1 , B2) corresponding to functionalities specific to the said associated client station

7 Network equipment according to claim 5 in combination with claim 2, characterized in that the said driver also comprises a specific part (BO, B1 , B2) corresponding to IP routing functionalities for the said associated client station

8 Network equipment according to any one of the aforementioned claims, in which the said wireless network (WLAN₄) is a WIMAX network

9 Method of communication in an access point (AP₃) by means of an inter-network bridge (30), between at least two local networks of which one at least is a wireless local network (WLAN₄), via associated network interface units, characterized in that it comprises a step (100 3a) for instantiating and associating with each client station (ISi IS₂) of the said wireless local network, a wireless network interface unit (ISi-NIU IS₂-NIU), and an update step (100 4) of the network interface units available in the said inter-network bridge (30)

10 Method of communication according to claim 9, characterised in that the said instantiation step (100 3a) is triggered by the detection (100 1 a) of a client station connection to the wireless network 1 1 Method of communication according to claim 9, characterised in that it comprises a deletion step (100 3b) of a wireless network interface unit, triggered by detection of a disconnection (100 1 b) of the associated client station 12 Method of communication according to any one of claims 9 to 1 1 , in a router type access point (AP₄), in which the said inter-network bridge (30R) comprises IP routing functions (200), characterized in that the said instantiation step (100 3a) of a wireless network interface unit (ISrNIU_, IS₂-NIU), a wireless network interface unit is associated with a single client station, and in that the said method comprises a step (200) the association with each of the said wireless network interface units instantiated for the said wireless network (WLAN₄), of an IP subnetwork, the said IP subnetwork being associated with the corresponding client station.