Local area network with wireless client freedom of movement

Local area network with freedom of movement of wireless client

Background of the invention

FIELD The present invention relates to a local area network (LAN), and more particularly to a LAN with connected wireless devices.

Background technique

The Institute of Electrical and Electronics Engineers (IEEE) wireless protocol denoted as 802.11b is an Ethernet local area network (LAN) variant. Ethernet technology has shown an amazing ability to adapt to new requirements, from a simple 10Mb/s bus to a gigabit full-duplex switching network and wireless LAN. Ethernet is well known and has experienced many cost reductions and integration of Ethernet equipment. The retail price of some current Ethernet interface cards (10BaseT) is less than $10. 802.11b wireless LAN (WLAN) card technology is subject to the same economies of scale, and the price has fallen below 30% of its relatively recent original price. Assuming the track record of Ethernet, Ethernet is a low-risk, scalable technology, for example, suitable for solving the challenges of wide-area mobility.

Therefore, the WLAN technology has been characterized as a disruptive technology. In other words, WLAN technology can change the paradigm and cause unexpected and unpredictable market development. Past examples of interrupt technology are the telephone, personal computer (PC), and the Internet. Now, WLAN is becoming ubiquitous, providing cheap solutions for home and office networks. However, currently, there are three main limitations in WLAN technology: speed, range, and security.

The 802.11b standard supports speeds up to 11Mbs. However, 802.11a and 802.11g are promising to deliver much higher speeds. Although typically limited to the range of about fifty meters outdoors (50m), but tests have shown that the use of directional antennas can be reached to a range of 20 miles. Continue research to expand the coverage of wireless base stations. Wired Equivalent Privacy (WEP) for wireless networks has proven to be less secure than expected. The security restrictions of WEP are now well known, and research is underway to enhance these protocols to improve the security of wireless interfaces.

The IEEE 802.1Q virtual LAN (VLAN) protocol defines the interoperability operation of VLAN bridges. 802.1Q allows the definition, operation, and management of the VLAN topology within the bridged LAN infrastructure, so that all types of LANs can be connected together through a media access control (MAC) bridge.

To date, these Ethernet LAN variants have been relatively rigidly constructed. Once attached or connected, a device can freely communicate with other attached devices. However, if after sending a request, the connection is lost before the response is received, the response is also lost. Once reconnected to the same or different port, and even before the response arrives, the response is lost and the request must be re-sent. This is still true for prior art VLANs, and even for devices wirelessly connected to such VLANs. Therefore, if a wireless device connected to the VLAN through an access point leaves the receiving area of the access point, the wireless device must reestablish communication. Even if it never leaves the entire LAN reception area, that is, an area covered by all connected access points, and even if it remains in the reception area of another connected access point, communication must be re-established.

Therefore, there is a need for a wireless LAN in which wireless connection devices can freely roam around in the receiving areas of all connected access points through a wide area network.

Summary of the invention

An object of the present invention is to improve user mobility on a wireless network; another object of the present invention is to expand the availability of wireless device network connections; another object of the present invention is to freely allow network clients connected to the network wirelessly to maintain Roaming outside the range of the currently connected access point while the network is connected.

The present invention relates to a network having a wireless connection, a means of transportation connected to and including the network, and a method of managing network data flow. The network includes multiple wireless access points, and each wireless access point is connected to an Ethernet aggregation switch. Each Ethernet aggregation switch is virtual local area network (VLAN) aware, and matches the customer service from the connection access point with the access VLAN. The virtual network switch maintains an association table between the access VLAN and the core VLAN. The virtual network switch uses the association table to manage free-type client services between the mobile station on the access VLAN of the connected Ethernet aggregation switch and the appropriate core VLAN. The means of transportation including the network may be a train with an access point located at the trackside that connects train passengers to a public network such as the Internet. The wireless devices on the train can also be connected to this kind of network onboard.

Description of the drawings

The above and other objects, aspects and advantages will be better understood from the following detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings, in which:

Figure 1 shows an example of a preferred embodiment of a free virtual local area network (FLAN); Figures 2A-B show a flowchart for FLAN switching packet processing, downstream packets on access ports, and upstream packets on core ports; Figure 3 is an example of the VLAN configuration of the Ethernet collective switch; Figure 4 shows an example of how the preferred FLAN switch pre-programmed with the default relationship relates to the VLAN/port; Figure 5 shows how to map the core VLAN to the logical interface An example; Figure 6 shows an example of the FLAN installed on the train to provide train passenger users with mobility on the train; Figure 7 is an example of a preferred trackside network; Figure 8 is between the access network and the FLAN switch An example of tunneling service.

detailed description

Figure 1 shows an example of the preferred embodiment network 100 with wireless access capability, namely, a free virtual local area network (FLAN) 100, in which clients on mobile stations roam freely in the wireless coverage area once they are connected , And they are seamlessly switched from one access point to another when they roam. A mobile station (MS) 102, 104, which may be a wireless client device, is connected to one of a plurality of access points (AP) 106, 108, 110, 112, 114, 116 through a wireless data link. Examples of such mobile stations 102, 104 or wireless client devices may include familiar personal digital assistants (PDAs), cellular phones (more specifically, cellular phones with Internet capabilities), notebook computers/wireless graphic input devices , A desktop computer or a vehicle, such as a train with an on-board network capable of wireless communication as described further below. Each AP 106, 108, 110, 112, 114, 116 is connected to an Ethernet aggregation switch 118. Each collective switch 118 aggregates all customer services from the connected APs 106, 108, 110, 112, 114, 116, and transmits it upstream to the preferred free-type virtual network switch or FLAN switch 120. Although not shown in this example, the preferred embodiment network may include more than one layer of collective switches 118 and/or FLAN switches 120.

The FLAN switch 120 can be connected to a typical Dynamic Host Configuration Protocol (DHCP) server 124 through a typical router 122 and to a public network, such as the Internet 126. For optional security, the router 122 is also externally connected through a typical gateway 128 that provides access control, network address translation (NAT), and firewalls. Each FLAN switch 120 may have multiple VLAN trunk interfaces 130, 132. The FLAN switch interface 130 connected to the collective switch 118 is referred to herein as an access port, and the packet arriving at the access port 130 is referred to as a downstream packet. The FLAN switch interface 132 connected to the router 122 is referred to herein as a core port, and the packet arriving at the core port 132 is an upstream packet.

A VLAN-aware switch refers to an Ethernet switch that associates each frame with a single VLAN, for example, the Ethernet aggregation switch 118. A typical VLAN-aware switch includes an association table, where each row contains MAC addresses, VLAN IDs, and ports. Therefore, the VLAN-aware switch forwards each frame to the MAC address based on that single related VLAN. In contrast, a preferred FLAN switch 120 associates each frame with two VLANs, one on the access port 130 and the other on the core port 132. To this end, each FLAN switch 120 maintains a port association table, where each row contains MAC addresses, access ports/VLAN pairs, and core port/VLAN pairs. In addition, the collective switch 118 is configured to statically map each access port to a different VLAN on its trunk port.

Alternatively, each collective switch 118 may share a VLAN among multiple APs 106, 108, 110, 112, 114, 116, and each AP is connected to a different port. VLAN sharing may be suitable to minimize the number of VLAN IDs used. However, because it has more available VLAN IDs (4094) than ports on any one collective switch 118, generally, the FLAN switch 120 can reuse the VLAN ID on a different collective switch 118, making sharing the VLAN ID unnecessary.

Preferably, the transmission/reception of each access point 106, 108, 110, 112, 114, 116 is such that the coverage area of each specific access point overlaps with other adjacent access points, which is predetermined The coverage area provides uninterrupted service. Therefore, the mobile stations 102, 104 connected to the network through one of the access points 106, 108, 110, 112, 114, 116 can pass between the access point receiving areas and remain unchanged from the rest of the FLAN 100 Communication. Moreover, the FLAN switch 120 seamlessly receives data transmitted from the connected mobile stations 102, 104, and from specific access points 106, 108, 110, 112, 114, 116, wirelessly receives the data from the collective switch 118, and passes The Internet 126 forwards the received data to the desired destination. Accordingly, when data is received from the Internet 126, the FLAN switch 120 directs it to an appropriate mobile station 102,104. The FLAN switch 120 manages seamless communication between the mobile stations 102, 104 and the Internet 126. When a mobile station 102, 104 moves from an access point receiving area such as 110 to another such as 116, the data to/from the specific mobile station 102, 104 is automatically transmitted through the rest of the FLAN 100 correctly without any Manual intervention.

2A-B show a flow chart for packet processing of a FLAN switch according to a preferred embodiment of the present invention. In the flow chart 140, downstream packets on the access port are shown, and in the flow chart 160, the core port is shown. Upstream grouping on. In FIG. 2A, in step 142, downstream packets are received on the access port. If the downstream packet is a DHCP request, the router (122 in FIG. 1) acts as a DHCP relay agent and passes the packet to the DHCP server 124. In addition to functioning as a normal DHCP server, the DHCP server 124 also returns an address to the client, thereby configuring the client (for example, MS 102, 104), and switching to deliver services. The DHCP server 124 can reassign the clients 102, 104 to a subnet that does not match the default VLAN assigned by the FLAN switch. When MS 102, 104 is assigned to a non-default subnet, the DHCP response is directed to the appropriate DHCP relay agent and continues to be directed to the correct VLAN.

Therefore, in step 144, continue to check the port association table to determine whether the frame includes the MAC address of the currently connected MS 102, 104. If the packet does not originate from the current connection, then in step 146, a new connection is configured by entering the source MAC address, access port/VLAN, and default core port/VLAN information in the port association table. The default core port/VLAN is related to the incoming access port/VLAN. In step 148, the appropriate VLAN tag is changed to reflect the new default core VLAN for downstream packets. Then, in step 150, the packet is switched to the default core port. However, if in step 144, the MAC address is identified as the currently connected MS 102, 104, then in step 1 52. Check the port association table to determine whether the access port/VLAN has been changed. When a mobile station (e.g., 102) roams between the AP reception area, e.g., from the first wireless access point 110 to another wireless access point 116 in FIG. If the access port/VLAN has not changed, then proceed to step 148, the packet is updated with the appropriate VLAN tag, and is switched to the appropriately identified core port in step 150. Otherwise, if the access port/VLAN is changed in step 152; then the port association table is updated in step 154, and the VLAN tag is changed in step 148. Then, in step 150, the packet is switched to the appropriately identified core port.

Similarly, in step 162 of FIG. 2B, when a packet is received on the core port, in step 164, for a known destination, the packet frame is checked. If the upstream packet is not sent to a known destination, then it is not intended for any currently connected MS (for example, MS 102 or 104), and at step 166, the packet is discarded. However, if the frame includes the destination MAC for the connected MS 102 or 104, the packet is for a known destination. Then, in step 168, the association table is checked to determine whether the client association has been changed from the most recent communication with that client. The association table may have changed because the identified core VLAN may have been changed in the DHCP response, or because the MS 102, 104 has been assigned to a VLAN other than its incoming port by default. If there is a failure to the backup router, the VLAN and port may also change. If the client affinity has not changed, then in step 170, the VLAN tag is changed to reflect the correct access VLAN for the packet. If the port association has changed, then in step 172, the port association table is updated before the VLAN tag is changed in step 170. Then, in step 174, the packet is switched to its access port.

Therefore, for a packet from mobile stations 102, 104 that propagates on layer 2 of the access network on the access side of the FLAN switch 120 in FIG. 1, based on the physical location of the mobile station in the network, the packet is allocated to VLAN, that is, the port used for the access point 106, 108, 110, 112, 114, 116 to which it is connected. Based on the logical location of the mobile station in the network or equivalently the mobile station's IP subnet, a packet transmitted to the mobile station on the core side of the FLAN switch 120 is assigned to a VLAN.

FIG. 3 is an example of the VLAN configuration of the Ethernet aggregation switch 118 according to the preferred embodiment of the present invention. Preferably, the FLAN switch cooperates with the VLAN configuration of the Ethernet aggregation switch 118 and the router 122 through the VLAN trunk interface 130. In this example, if appropriate, the AP 180 is grouped, and each group 182, 184, 186 is connected through a hub 182h, 184h. The hubs 182h, 184h and individual APs (ie, a single AP group 186) are connected to the Ethernet aggregation switch ports 188, 190, 192. Each of these Ethernet switch ports 188, 190, 192 is mapped to each VLAN 194, 196, 198 on the VLAN trunk 200 connected to the FLAN access port. Each AP group 182, 184, 186 is mapped separately; there is no layer 2 connection between the AP groups 182, 184, 186 in the Ethernet aggregation switch 118.

Fig. 4 shows an example of how the FLAN switch 120, which is pre-programmed with the default relationship, is related to the access port 212 of the FLAN switch 120 and the VLAN 194, 196, 198, 202, 204, 206, 208, 210 on the core port 214 . The default association table 216 provides default VLAN pairs and fixed core VLAN assignments for the FLAN switch 120. The MAC address in the association table 218 is used to allocate devices that access a special network or devices that require a fixed IP address. These relationships can be stored in a clear text configuration file and modified with any appropriate text editor.

In this example, as shown in the association table 218, the FLAN switch 120 knows three mobile stations with MAC addresses ABC, XYZ, and 456 that are all on port 6. The VLAN ID number (for example, 1, 2, 3, 4, 21, 22, 23, 24) is unique, but the port/VLAN byte group identifies the source and destination of a packet. Therefore, for all interfaces, the VLAN ID number is free and reusable. In this example, as shown in the default association table 216, devices ABC and 456 are in their default VLAN associations. In contrast, device XYZ is not in the default VLAN association for port 6. Instead, its association connects it to VLAN 204. Thus, for this example, the device XYZ has moved from one access point group to another.

FIG. 5 shows an example in which connection core VLANs (for example, 204, 206, 208, and 210 in FIG. 4) are mapped to logical interfaces 220, 222, 224, and 226 on the router 122. In this example, each logical interface 220, 222, 224 226 is configured to provide a DHCP relay; the DHCP server 124 uses the relay agent IP address (ie, the giaddr field in the DHCP message body) to determine the appropriate IP subnet . Different sub-interfaces (each corresponding to a different input VLAN) 220, 222, 224, 226 in the router 122 can be configured using different rules, for example, for Internet access. For example, the management user can be assigned to an independent management VLAN with access to servers that are not available to general users. The DHCP server can be modified to respond on different VLANs, so that the DHCP server can control the VLAN assignment on the core side of the FLAN switch.

FIG. 6 shows an example of a LAN 230 installed on a train. The LAN may be a FLAN to provide on-train mobility for train passenger users. The LAN 230 installed on the train can be connected to the trackside AP (corresponding to the APs 106, 108, 110, 112, 114 and 116 in Figure 1) using the customer WLAN/Ethernet bridge 234 through the existing small Ethernet router 232 Local station.

Preferably, the customer wireless LAN bridge 234 provides a bridging connection between the train router port and the trackside Ethernet infrastructure. The customer WLAN bridge 234 is connected to a dielectric gain omnidirectional antenna system that can be installed outside the train. The standard small router 232 can provide DHCP and basic connections on the train at a very low cost. In addition, although the train is moving between stations, only the train router MAC address can be seen on the upstream side of the FLAN switch (not shown in this figure). In this way, when the train moves between APs, the train passenger users are not affected by the movement event. Optionally, back-to-back dielectric gain directional antennas aligned from start to end can be installed on the train. According to the antenna position, power and electrical noise, each car can be equipped with standard 802.1lb access points 236, 238, 240, 242, 244. Daisy-chained Ethernet hubs 246, 248, 250, 252, and 254 connect clients in the train to each other. Hubs 246, 248, 250, 252, and 254 can also provide wired Ethernet connections on passenger seats. Preferably, all train networking hardware is existing, but the antenna and power system are modified as needed for use by the airborne train.

In a railway application embodiment, the wireless client devices 256, 258 are connected to the FLAN on the train, and the core FLAN AP is located beside the track. The local APs 236, 238, 240, 242, 244 on the train are hidden behind the mobile station or "customer equipment" router 232. The router 232 serves as a gateway for all passenger users on the train, and the router MAC address is appended to all outgoing packets. Preferably, the train router 232 uses the layer 3 address to direct traffic to the clients on the train. In addition, the core FLAN switch next to the track sees all arriving train traffic with the same MAC address. A single MAC address means a single table update whenever there is a movement event due to the movement of the train.

In another railway application embodiment, each railway car has an internal network, including wired Ethernet hubs for wired connections, internal wireless access points, and external wireless client bridges connected to wireless access points next to the track. In this way, as described above, each railway car has an independent network, and services can be bridged to the trackside network and the FLAN switch. Advantageously, this embodiment avoids the cost and complexity of wired networks between railway cars. Optionally, the customer bridge can also provide communication between railway cars.

Therefore, a preferred railway FLAN provides 2-10 megabits per second Internet connection for passenger Internet access, train data service and for security. Passengers can use a standard wireless LAN network card or wired Ethernet connection to connect to the onboard FLAN. An independent dedicated wireless FLAN connection moves data between the train and the trackside AP. FLAN provides mobility between APs beside the track. The application of the invention in a very large railway network allows hundreds of trains on thousands of kilometers of track to be connected to the same network.

Figure 7 is an example of a preferred trackside or FLAN 260. In this example, the trackside 802.1lb AP 262, 264 usually coexists with the existing trackside system, in this example, the trackside Global System for Mobile Communications-Railway Basic Receiving Station (GSM-R BTS). The AP 262, 264 utilizes directional WLAN antennas 266, 268 directed along the track to obtain a range of 5-10 kilometers. If the GSM-R BTS location does not provide complete coverage, additional AP 262, 264 can be installed between the transceiver locations. Additionally, trackside copper telephone lines 270 and symmetrical digital subscriber line (sDSL) modems 272 can be included to transmit data back to the GSM-R location.

Figure 8 is an example of a preferred FLAN 280 tunneling service between the FLAN switch 282 and the access network 284. Because FLAN 280 is based on a standard Ethernet protocol, it can be easily configured to tunnel Ethernet frames on most typical existing networks such as SONET, ATM, or IP networks. In this example, the access network 284 includes a set of APs 286, 288, 290 connected to a hub 292. The hub 292 is connected to the router 294, and the router 294 is connected to the router 296 through the Internet. The router 296 is connected to the FLAN switch 282 through the Ethernet aggregation switch 298. When it is otherwise impossible to share bandwidth with, for example, GSM-R BTS, tunnel transmission managed by routers 294 and 296 can be used. Optionally, for example, using Cable Modem (cable modem), xDSL or TDM, the tunneled service can be transmitted back to the FLAN switch 282 through a conventional Internet connection.

Advantageously, the present invention facilitates the creation of a large free-type wireless data network, that is, a FLAN that allows end users to move. FLAN can be established anywhere, for example, airports, coffee shops, dense urban areas, and on trains and buses. In addition, the present invention uses industry standard wireless data technologies such as 802.1lb and 802.1la to provide free wireless access. Typical available equipment for wireless access, such as a laptop computer with an 802.1lb card, enables clients to connect to the FLAN using Internet Protocol (IP), regardless of location, whether in the office, at home, or in the country by rail Range travel. FLAN is a simple and easy-to-manage network, in which existing client devices can be "turn on and go" and move freely between AP receiving areas without loading additional software or configuring client devices. A preferred FLAN embodiment can use standard existing equipment, and if customization is required, such customization can be limited to a single location in the network, the FLAN switch. In addition, if required, authorization and accounting (AAA) and other wireless security features can be included, just like any other prior art network.

The present invention utilizes a layer-two Ethernet network to provide all these advantages to interconnect these wireless access points. The general scalability problem of such a network is avoided by IEEE802.1 Q virtual LAN (VLAN) to effectively divide the network into many smaller networks, so that the broadcast service and spanning tree are used to avoid the problem.

Although the present invention has been described in the form of preferred embodiments, those skilled in the art will recognize that within the spirit and scope of the appended claims, the present invention can be practiced with modifications.