Wireless network communication system and method with double packet filtering function

Wireless network communication system and method with dual packet filtering function

5-1 Invention Field and Background

A. Field of invention

The present invention is a system and method that integrates the communication mechanism of Mobile IP and IAPP, especially a communication system and method with packet filtering function, so that roaming hosts can roam between the capture points of different sub-domains, It can also reduce the transmission of broadcast packets on the network end of the night code.

B. Background of the invention

The current IEEE 802.11 Wireless LAN (Wireless LAN) standard only defines network protocols below the MAC layer, and has not formulated a communication mechanism at the network layer. The communication protocol between the access points must be based on the IAPP (Inter Access Point Protocol) to regulate the information exchange between the access points. Basically, IAPP is built on top of the UDP/IP layer and is based on the IEEE802.11 standard. According to the communication mechanism of IAPP, the capture point is to obtain the information of other capture points by broadcasting for the roaming host to use when roaming. When the capture point is activated for the first time, a broadcast "announce request packet" (announce request packet) is sent to the network. The capture point that receives the packet responds with an announce response packet, which contains the information of the capture point, such as the MAC address of the capture point. When the roaming host roams to the range served by another capture point, it will send a reconnection request (reassociation request) to the new capture point. At this time, the new capture point must find out the IP address of the capture point of the original service of the roaming host, so as to send a "handoff request" to the capture point to transfer the service to the roaming host To the new capture point.

However, if a roaming host roams between capture points distributed in different sub-domains, the communication mechanism of the conventional IAPP will be blocked by routers and cannot obtain the IP address of the capture point originally served by the roaming host. Therefore, the capture points located in different sub-domains will not be able to exchange messages through the broadcast communication type, so they will not be able to know each other's messages. In other words, when the new capture point receives a reconnection request from the roaming host, if the original capture point and the new capture point are in different IP sub-domains, the IP address of the original capture point cannot be obtained , So that the new capture point cannot send alternate request data frames to the original capture point, causing the roaming host to be unable to roam between the capture points distributed in different sub-domains, which seriously affects the application range of the wireless network. Moreover, if the capture point continuously broadcasts the relevant information of the capture point to the capture point in different subnet domains, it will cause bandwidth congestion on the wireless network end and affect the transmission performance.

On the other hand, Mobile IP is a wireless local area network communication protocol and technology. Mobile IP defines a communication protocol at the network layer so that mobile stations can roam in different sub-domains. Mobile IP mainly uses an agent module to record the current IP address of the mobile host. When the mobile host roams to another sub-domain, the proxy module will re-encapsulate the packet sent to the mobile host, and then forward it to the mobile based on its new IP address as the destination address. Host. In this way, the mobile host can roam in different sub-domains and still receive and transmit data normally.

At present, Mobile IP and IAPP have no integrated solutions because they deal with different network-level communication mechanisms separately. Therefore, in order to enable the mobile host to roam in different subnet domains, integrating the communication mechanism of Mobile IP and IAPP is an effective solution.

5-2 Purpose and summary of the invention

Based on the above-mentioned problems, the main purpose of the present invention is to provide a wireless network driver and IAPP management module with a packet filtering device to communicate between wired and wireless networks, and make the edge active host in the same subnet domain. Random roaming between different basic service sets (BSS) in.

Another object of the present invention is to provide a system and method that can integrate Mobile IP and IAPP mechanisms in the capture point, and enable the mobile host to roam between different sub-domains arbitrarily.

Another object of the present invention is to provide a communication system and method that can filter unnecessary packet transmission, so as to avoid waste of wireless bandwidth.

Based on the above objective, the present invention establishes an acquisition point according to the IAPP protocol to solve the problem of handoff between different basic service sets (BSS) of mobile hosts in the same subnet domain. The capture point of the present invention integrates the existing IAPP and Mobile IP technologies, so that the mobile host can also move arbitrarily in different subnet domains. When IAPP is integrated with Mobile IP technology, the present invention further utilizes a wireless network driver with packet filtering function and a bridge interface to reduce unnecessary or redundant packet transmission and increase the efficiency of wireless network transmission.

The communication system of the present invention mainly includes: an IAPP management module, located at the user level of the capture point, used to execute the IAPP processing program and maintain a corresponding table of the hardware address and IP address of the capture point; a wireless The driver of the network card is located at the core level of the capture point, and is used to execute the IAPP process according to the system call of the IAPP management module, and the driver of the wireless network card includes a package and, Used to determine whether to forward the received packet; a bridge interface to communicate between the wired network and the wireless network, and has a packet filtering module to control the packet forwarding of the wireless network; and a wired network Lucai's driver is used to forward packets from the wired network.

5-4 Detailed description of the present invention

In order to integrate the communication mechanism of Mobile IP and IAPP, the present invention creates a capture point, and proposes a communication system and method applied to the capture point to integrate the communication mechanism of IAPP and Mobil IP, and solve the problem of mobile host In the same subnet domain, different basic service sets (BSS) are handoffs (handoff), so that the mobile host can roam freely in different subnet domains.

The system architecture diagram of the present invention is shown in FIG. 1. In the Internet 11, there are at least two different IP subnet domains A and B. Each subdomain has a unique agent module 12, 13, which can be a local agent module (homeagent) or a remote agent module (foreign agent) to be responsible for the network layer of the entire subdomain The mobile host 10 communicates. Each agent module 12, 13 uses the Mobile IP transmission protocol as the standard for communication with each other. At the same time, each sub-domain 12, 13 may also include one or more capture points 14, 15, 16 to cover the entire sub-domain. Each acquisition point is based on the IAPP transmission protocol as the standard for communication with each other. Moreover, the capture points 14, 16 of different sub-domains can also be directly communicated according to the IAPP communication protocol.

In order to solve the problem that when the mobile host 10 moves from the domain A to the domain B, the capture point 16 of the domain B cannot obtain the IP address of the capture point 14 of the domain A and cannot complete the handover process, the present invention The structure of the capture point 16 is shown in FIG. 2.

As shown in the figure, the present invention uses a personal computer as the capture point 21 and simultaneously uses two network cards, one of which is an Ethernet wired network card 22, and the other is a PCMCIA wireless network card 23, and use Linux as the operating environment. The wired network card 22 is connected to a wired network 24 and serves as a communication interface for the wired network 24, and the wireless network card 23 is connected to a wireless network 25 and serves as an interface for the wireless network 25. There is a bridge 26 between the two for communicating information from the wired network card 22 and the wireless network card 23.

The driver of the wireless network card 23 has the basic functions of processing the 802.11 mechanism, including processing the management frame sent by the mobile host, such as: association request (Association Request), reassociation request (Reassociation Request), and removal Disassociation Request, etc.

In addition, the present invention creates an IAPP management module in the communication system of each capture point to process the received IAPP packets according to the IAPP transmission protocol, and execute the processing procedures defined in the IAPP transmission protocol.

The IAPP management module uses UDP/IP to transmit data, which mainly includes two processing procedures: the Announce processing program and the handover processing program, as well as the processing of four different packet types: namely Announce Request, Announce Response, Handover Request and Handover Response.

The schematic diagram of the structure of the IAPP management module of the present invention is shown in FIG. 3. The IAPP management module 31 is a user-level management module, and can communicate with the driver 33 of the wireless network card through a system call. Since general user-level programs cannot directly access core-level data, the IAPP management module 31 uses system calls to obtain relevant information about the capture point from the wireless network card driver 33, such as hardware Body address, Station ServiceID, and related information of the mobile host, such as the hardware address, and the hardware address of the previously registered capture point.

In order to allow the user-level IAPP management module 31 to communicate and access data with the core-level wireless network card driver 33, the system call of the present invention includes the following types:

1. Acquisition point information acquisition module Get_AP_Inf(): used to obtain relevant information about the acquisition point and the registered hardware address of the mobile host.

2. Mobile host information acquisition module Get_MH_Inf(): used to obtain relevant information about the mobile host, such as the hardware address and the hardware address of the previously registered capture point.

3. Program number storage module Save_PID(): Used to store the process ID of the IAPP management module in the driver of the wireless network card.

4. Mobile host information removal module Del_MH_Tab(): Used to delete the mobile hosts related information when the mobile host roams to another new basic service set, the original IAPP management module of the mobile host.

On the other hand, when the wireless network card driver 33 of the capture point receives the ReassociationRequest packet sent by the mobile host, the wireless network card driver 33 uses signaling. To notify the IAPP management module 31 to execute the handover process.

The processing procedure of the IAPP management module 31 when processing an announcement request is shown in FIG. 4. The notification request processing program is mainly responsible for issuing an announcement request (announce request) 41 when a new capture point is first activated, and broadcasts across sub-domains and sub-domains in a broadcast manner.

The notification of the capture point requires that the packet is in the form of broadcast. Since the broadcast packet will be blocked when passing through the router, when the capture point is activated for the first time, the notification packet to be broadcast cannot be smoothly broadcast to the location. A capture point outside this subdomain. Therefore, when the capture point of the present invention is activated for the first time, the broadcast notification request packet (announce request packet) must be broadcast to this sub-domain, and it must also be broadcast to other sub-domains where the capture point exists. The other subdomains where the capture points are located are known in advance, or they can be set when the capture points are activated to determine which adjacent subdomains to broadcast to. After broadcasting directly to the subdomain where the capture point is located, the AnnounceResponse packet can be received from each capture point to obtain the IP address of the capture point, so the capture in the subdomain Point can smoothly generate a MAC address and IP address correspondence table 44 to record the MAC address and IP address of the captured point. In this way, it can provide the information needed when sending and receiving packets later.

The operation steps are as follows: First, when the IAPP management module is started for the first time, it is necessary to obtain the hardware address of the wireless network card of the acquisition point through the system call of the acquisition point information acquisition module Get_AP_Inf, as the Capture the basic service set number (BSSID) formed by the point, and fill the basic service set number in the notification request packet, and broadcast the notification request packet to this sub-domain by broadcasting. Take the broadcast of the existing subdomain, and then wait for the response.

Later, if the IAPP management module 31 receives the notification reply packet 42 from the existing capture point on the other network, it will not only send the notification reply packet 43 to other capture points, but also the received In the notification reply packet, read the hardware address and IP address of the wireless network card of the capture point, and create a corresponding table 44 of the hardware address and IP address of the capture point for handover (Handover) Used when transmitting packets in the program.

The main purpose of creating the correspondence table 44 between the hardware address and the IP address is to facilitate the query of the IP address of the capture point previously registered by the mobile host. When the mobile host roams from one basic service set (BSS) to another new basic service set (BSS), the mobile host must register with the new capture point, and the new capture point must inform the mobile host of the previous registration The acquisition point of the mobile host has moved the message, and according to the IP address of the previously registered acquisition point, a handover request packet (Handover request packet) is sent to the originally registered acquisition point. However, the reconnection request packet (reassociation request packet) sent by the mobile host only contains the hardware address of the capture point previously registered by the mobile host, and the IP address is not known. Therefore, through the corresponding form 44, the IAPP management module 31 can query the IP address of the capture point previously registered by the mobile host according to the hardware address of the registered packet, and send a handover request packet (Handover request packet).

In addition, the handover processing program is the most important core part of the entire IAPP management module 31. When the driver 33 of the wireless network card of the capture point receives the reconnection request packet (reassociation request) sent by the mobile host, the driver 33 of the wireless network card informs IAPP through signaling. The management module 31 is used to handle the roaming related procedures of the mobile host.

The operation schematic diagram of the handover processing program of the IAPP management module 31 of the present invention is shown in FIG. 5. When the IAPP management module 51 receives the signal 51 sent by the driver 54 of the wireless network card, it indicates that a new mobile host has roamed into the basic service set formed by this capture point. At this time, the IAPP management module 51 must notify the mobile host of the previously registered capture point 53 about the information that the mobile host has roamed. First, the IAPP management module 51 uses the system call of the mobile host information obtaining module Get_MH_Inf to obtain the hardware address of the capture point previously registered by the mobile host. Then, according to the hardware address of the previously registered capture point, query the corresponding table 44 to find the corresponding IP address, that is, the IP address of the capture point previously registered by the mobile host, as the handover request packet (Handover Requestpacket) The destination address of the transmission. After that, the IAPP management module 51 can send the handover request packet to the capture point registered by the original mobile host according to the destination address, and wait for a response.

At this time, in addition to the IAPP management module 51 that needs to send the handover request packet, the driver 54 of the wireless network card of the capture point must also add the relevant information of the newly registered mobile host to the driver 54 of the wireless network card. Inside the packet filter module 55 (packet filter). In this way, all mobile hosts registered in this subnet domain are recorded in the packet filtering module 55. Therefore, when a packet from the wired network is received, the registry in the packet filtering module 55 can be queried first to see if there is any mobile host data that records the destination address of the packet. If not, it does not need to be sent to On the wireless network side, unnecessary packet transmission can be reduced in this way.

On the other hand, the capture point that receives the handover request packet (that is, the capture point previously registered by the mobile host), in addition to its IAPP management module 53 must send a handover response packet (Handover Response paeket), it must also use the mobile host The system call of the information deletion module Del_MH_Tab communicates with the driver 56 of its wireless network card to delete the record of the roaming mobile host from the registry in its packet filtering module 57. In this way, as long as the record of the packet filtering module 57 is inquired, it can be known whether the mobile host is still within the service range of the capture point. If the mobile host has roamed to other basic service sets, when the wired network end of the capture point receives the packet to be sent to the mobile host, the packet will not be sent to the wireless network end, so it is effective Reduce unnecessary packet transmission traffic on wireless networks.

Since the IAPP mechanism mainly deals with the roaming problem of mobile hosts in the same subnet domain, when the mobile host moves to a different subnet domain, it must rely on the existing Mobile IP technology to handle the roaming problem.

The Mobile IP standard stipulates that each agent module (agent must unicast regularly unicast relevant information about itself in its own subnet domain. When the capture point receives the broadcast packet, it also It will be broadcast to the wireless network. Under the wireless network architecture of infrastructure, each capture point will also broadcast information related to itself regularly. In this case, the broadcast packet of the wireless network will be There are two types. However, as far as the mobile host is concerned, when roaming, the mobile host mainly uses the notification signal (beacon) broadcast by the capture point itself to identify the basic service set (BSS) where it is currently located, instead of using The packet broadcasted by the proxy module, so the capture point of the present invention does not need to periodically broadcast the packet for the proxy module, but chooses an appropriate time to broadcast the message sent by the proxy module to avoid occupying the wireless network. The bandwidth of the road. Because if the capture point does not broadcast the packets sent by the proxy module at all, the mobile host cannot tell whether it has roamed to a different sub-domain.

In order to reduce unnecessary wireless network packet traffic, the present invention also adds a packet filtering module to the bridge interface to analyze the received broadcast packets. If it is determined that the broadcast packet is sent by the proxy module, the bridge interface does not need to send the packet to the wireless network. Only when the mobile host registers with the capture point, the bridge interface will send the packets broadcast by the proxy module to the wireless network. In this way, the mobile host can know whether it has roamed to a different subnet domain and can execute the processing mechanism of Mobile IP. After the mobile host completes the registration process of Mobile IP, the bridge interface on the capture point will stop transmitting the packets broadcast by the proxy module. This way of processing can avoid occupying too much wireless network bandwidth.

The operation flow chart of the packet filtering module on the capture point and the bridge interface of the present invention is shown in Figure 6:

Step 661: Receive the packet.

Step 602: Read the destination address in the header content of the packet.

Step 608: From its destination address, it can be determined whether the packet is a packet broadcast by the proxy module of MobileIP? If not, proceed to step 604; otherwise, proceed to step 605.

Step 604: Send the packet to the wireless network.

Step 605: Query the registry of the mobile host to determine whether there is a mobile host registered with the capture point at this time? If not, proceed to step 606; otherwise, proceed to step 607.

Step 606: Limit the transmission range of the packet so that the packet will not be transmitted to the wireless network.

Step 607: If the mobile host is registered with the capture point, the packet is sent to the wireless network.

Step 608: End.

In order to smoothly send the information required by the announcement protocol, each capture point must have the following information: When sending an announce request packet (announce request packet), the host service ID (Station Service ID, SSID) is required To indicate the basic service set, basic service set, and physical transmission type of the mobile host to explain the wireless transmission method used by the mobile host, including direct sequence number (directsequence) or frequency hopping (Frequency Hopping) two types, channel number (channel ) To explain the frequency used by the capture point, etc.

When sending an announce response, the host service number (SSID), basic service set, entity transmission type, and announcement period are required to record the interval of each announcement response sent by the capture point. Its basic value is 120s, the notification signal (Beacon) cycle, to record the interval of each transmission of the notification signal (Beacon) by the capture point, and the handover timeout (Handover Timeout) to indicate that the handover must be completed within this time. The basic The value is 50Oms, the channel number, and the relevant information of the previously registered mobile host.

In order to smoothly transmit the data required by the handover protocol, each capture point must have the following data. That is, when the handover request packet is transmitted, the host service ID (SSID), basic service set, The original basic service set number (BSSID), the hardware address of the mobile host, and the message number are used to distinguish different messages and avoid repeated transmission of messages.

When sending a handover response, the required data is the same as when sending a handover request packet.

The above are only the preferred embodiments of the present invention, and have achieved a wide range of practical effects. All the equivalent changes and modifications made in accordance with the scope of the patent application of the present invention are still within the scope of the patent of the present invention.

<p>10: Mobile host 11: Internet</p><p>12: Local agent module 13: Remote agent module</p><p>14, 15, 16: capture point 21: capture point</p><p>22: Wired network card 23: Wireless network card</p><p>24: Wired network 25: Wireless network</p><p>31: IAPP management module 32: bridge interface</p><p>33: Wireless network card driver 41: Receive notification request packet</p><p>42: Notification reply packet received 43: Notification reply packet sent</p><p>44: Corresponding form 51: New capture point</p><p>52: Signal transmission 53: Previous acquisition point</p><p>54: Wireless network card driver 55: Packet filtering module</p><p>56: Wireless network card driver 57: Packet filtering module</p>

Figure 1 is a system architecture diagram of the present invention.

FIG. 2 is one of the embodiments of the capture point of the present invention.

3 is a schematic diagram of communication between the IAPP management module of the present invention and the driver of the wireless network card.

4 is a schematic diagram of the operation of the IAPP management module of the present invention and the IAPP management module of other capture points when processing notification requests.

5 is a schematic diagram of the operation of the IAPP management module and the driver of the wireless network card on the capture point of the present invention when a handover request is received.

6 is a flow chart of the operation of the packet filtering module on the capture point and the bridge interface of the present invention.