TWI387264B - Network association method for public transportation system - Google Patents

Description

Network connection establishment method applied in mass transit system

The technical field is related to a pre-planned network link establishment method for use in a mass transit system.

With the maturity and rapid spread of wireless communication technology, anytime, anywhere (Anytime, Anywhere) has been connected to the Internet. Users can access the Internet not only in enterprises, schools, homes, and public venues. Users can also use the Internet devices (such as laptops, personal digital assistants, etc.) to access the Internet in public transportation vehicles that provide Internet services. Wireless LAN (WLAN) developed based on IEEE 802.11 has been widely used in various places. Due to the low usage rate, even free of charge, and easy deployment, the WLAN interface is now standard on notebook computers or handheld devices. However, the access point of the WLAN access point (AP) is relatively small, and the mobility support is not sufficient. The wireless local area network usually chooses to use hot spot network access (Shot Spot Access) as a short distance but high frequency. .

In addition, mobile phone operators also provide data services for users to access the Internet, such as 3G/3.5G/Wimax, etc., which can be regarded as a wireless wide area network (WWAN). WWAN's Base Station (BS) has a large coverage area and good mobility support, but its bandwidth is small. Considering the cost and service rates of WWAN-compliant network interface cards, it is standard equipment for general-purpose mobile devices.

Furthermore, during the driving process of the mass transit vehicle, the user or mobile router (MR) may switch to a network of different nature (for example, switching between WWAN and WLAN), but for now, re The time it takes to establish a network connection is lengthy. Users cannot connect to the Internet until the network connection is re-established. The longer the network connection is re-established, the greater the interference with the user.

Therefore, it is better to have a method for establishing a network connection for a mass transit vehicle, which can shorten the time for reestablishing the network connection.

The present disclosure relates to a pre-planned network link establishment method for a mass transit vehicle that implements a pre-scheduling action support mechanism based on the predictable mobile behavior characteristics of the mass transit vehicle to shorten the re-establishment of the network connection The time of the line.

An implementation example of a network connection establishment method applied in a mass transit system is proposed. The method is for establishing a mass transit vehicle, a network connection between a host network and a visited network; wherein the master network has a master agent, and the visited network has a visit agent. The method for establishing a network connection includes pre-establishing a first passage between the main agent and the mass transit vehicle before the mass transit vehicle is departed; before the public transport vehicle departs or travels but does not arrive at the visiting agent Responsible for the second channel before the station is pre-established between the main agent and the visiting agent; with the assistance of the main agent, the visiting agent does not arrive at the responsible station before the mass transit vehicle Or pre-authorize the mass transit vehicle before departure and assign a network resource available to the mass transit vehicle; with the assistance of the master agent, the mass transit vehicle is responsible for the departure or departure of the vehicle The network resource configured by the visiting agent is known in advance before the station, and the mass transit vehicle pre-completes a link setting to the visiting agent before reaching the responsible station; and when the mass transit carries When moving into the visited network, the public transportation vehicle establishes an internet connection with the visiting agent according to the connection setting pre-completed before arrival.

In order to make the above content of the present disclosure more obvious and understandable, an embodiment will be described below, and the following description will be made in detail with reference to the following drawings:

In the disclosed embodiment, the network link is pre-established before the vehicle is driven or before the predetermined position is utilized by using the expected travel path to pre-authorize the authentication (base station connection right, network usage right, key, etc.). ) and resource acquisition (bandwidth, IP, etc.). To reduce the link delay and packet loss caused by changing the connection point when the Mobile Router (MR) or Mobile Node (MN) changes. MR/MN knows which subnet to connect to and which resource to use in its current location. The Home Agent (HA) and the Visit Agent (FA) know which subnet to which the MR/MN is connected and which resources to use.

1 is a schematic diagram showing a mass transit system and its network connection moving according to a predetermined itinerary according to an embodiment. As shown in Fig. 1, the mass transit vehicle 100 is, for example, a high-speed rail, a bus, a MRT, and a general railway, and has exclusive road rights and stations. The mass transit vehicle 100 travels according to the established route 105 and the flight schedule. Moreover, the mass transit vehicle 100 can access the subnetworks 120, 130, 140, 150, and 160 while traveling. The location information of the mass transit vehicle 100 can be known by any feasible method, such as a global address system (GPS), a position sensor disposed on the route, and a high-speed rail car position signal. Alternatively, the current position of the mass transit vehicle 100 can be derived from the travel time of the mass transit vehicle 100.

The mass transit vehicle 100 can provide network access services to mobile nodes (MNs) 110A and 110B to allow mobile nodes 110A and 110B to access the Internet. On the Internet, a node, if it often changes its point of attachment to the network, is called a mobile node. The contacts may change even if the network is communicating. In addition, the mobile node can access the Internet in wired or wireless mode. For example, in Figure 1, mobile nodes 110A and 110B access the Internet in wired and wireless manner, respectively.

A mobile router (MR) 101 is disposed in the mass transit vehicle 100. The MR 101 has at least two or more wireless network interface cards, with multiple interface management and heterogeneous network access capabilities, and can be connected to the Internet. MR's WWAN interface card can be connected to a WWAN (Wireless Wide Area Network); its WLAN interface card can be connected to a WLAN (Wireless Local Area Network).

WWAN refers to the data network provided by the telecom operators. The connection rate is low, but the coverage area of the base station is large. In addition, the WWAN has a small bandwidth but can be connected to the network at any time through its service network. It can also be called an Access Access (AA) network. A wireless network interface card that can be connected to the WWAN, such as a 3G/3.5G network card. In Figure 1, subnets 140, 150, and 160 are WWANs, and base stations 141, 151, and 161 are base stations for telecommunications carriers.

WLAN refers to a network that conforms to the IEEE802.11 technical specification, and has a high connection rate, but the coverage area of the base station is small. In addition, the WLAN has a large bandwidth but can access the network only at certain fixed times or places, called Spot Access (SA). An example of a wireless network interface card that can be connected to a WLAN is an IEEE 802.11a/b/g/n WLAN network card. In Figure 1, subnetworks 120 and 130 belong to the WLAN, while symbols 121 and 131 represent the access point (AP, Access Point) of the WLAN.

Additionally, stations 122 and 132 are, for example, stations of high-speed rail, and access points 121 and 131 can be disposed within stations 122 and 132, respectively. Further, in the present embodiment, the setting position of the access point is not necessarily limited to the inside of the station, and may be set at any position of the traveling route 105 so that the MR 101 can be connected to the WLAN.

In addition, the MR 101 can provide network access services for internal users (ie, MNs 110A and 110B) using any network interface, such as a wired Ethernet or WLAN network, such that the MNs 110A and 110B can pass MR 101. And connect to the internet.

Because the MR 101 is located within the mass transit vehicle 100, the MR 101 has predictable movement behavior that moves regularly in accordance with both the schedule and the route (e.g., route 105).

In addition to being connected to the AA network (WWAN network) at any time, the MR 101 can be connected to the SA network (WLAN network) for a short time at a known station. To connect the MR 101 to the SA network, the SA network (i.e., sub-networks 120 and 130) is provided with access points (i.e., access points 121 and 131) for the MR 101 to connect. The connection parameters are preferably planned in advance so that the MR 101 can successfully connect to the SA network. Connection parameters such as, but not limited to, a wireless network identifier ( SSID , Service Set Identifier), channel, authentication method, and password.

The home address of the MR 101 is pre-planned. The IP address of the MR 101 located in the SA network and the IP address of the Visit Agent (FA) connected to the MR 101 are also known in advance.

As can be seen from Figure 1, during travel of the mass transit vehicle 100, the MR 101 can be connected to the network via a widely covered but narrow bandwidth AA network (140, 150 and 160). When the mass transit vehicle 100 enters and stops at the stations 121 and 131 for a short time, the MR 101 can be connected to the network via a small but high frequency wide SA network (120 and 130).

An embodiment discloses a pre-scheduled mobility supporting mechanism, and an example of a specific embodiment thereof will be described below.

To achieve a pre-scheduled mobile support mechanism, in one embodiment, a pre-architected data structure, called a Care-of Table, is used. The transfer form is established in advance according to the schedule of the train, and the manager sets the fields of the transfer form according to the network parameters. The transfer form records the primary address (MR_HoA) of the MR and the WLAN address (MR_MAC) of the WLAN on each shuttle (ie, the mass transit vehicle 100). The MR's primary address MR_HoA is pre-planned. .

In addition, SA networks (sub-networks 120 and 130) and visiting agents (Foreign Agents, FA) are built in each station where the train is scheduled to stay (for example, stations 122 and 132 in FIG. 1). . The IP address (FA_CoA) of this visited agent is also recorded in the transfer form. Moreover, the MAC address (FA_MAC) of the AP in the SA network is also recorded in the handover form, where the AP is connected to the MR. What's more, the connection parameters (such as SSID), the authentication key (key), the AP information under the jurisdiction of the FA, and the network information (such as bandwidth, service server, etc.) required by the MR can also be recorded in the handover form. Inside.

Table 1 below shows an example of a referral form:

In Table 1 above, Rt represents the station (ie, route information) expected to stay in the itinerary of the Volkswagen Transportation Vehicle.

In one embodiment, the referral form can be manually set by the administrator or automatically set using the following methods. Reference is now made to Fig. 2, which shows a schematic diagram of an automatic setting of a handover form in accordance with an embodiment.

In Figure 2, the primary agent (HA) 210 is a host located on the home network. Via the HA 210, other hosts on the network will feel that the MN or MR is accessible at all times. The primary network refers to a network that has administrative rights to the mobile node/MR. For other hosts on the Internet, regardless of the current address of the mobile node and/or MR, the mobile node and/or MR appear to be connected to the primary network. The master agent (HA) provides a fixed primary address (HoA: Home Address) to the mobile node and/or MR. When other hosts on the Internet transmit data to the mobile node and/or MR, they only need to know the primary address and do not need to know the current temporary address of the mobile node and/or MR.

The Visiting Agents (FA) 220, 230, and 240 are hosts located on the Foreign Network, and can proxy the packets sent by the MN/MR. For mobile nodes and/or MRs, in addition to the main network, other networks that can be connected are called visited networks. When the mobile node and/or the MR are not on the primary network (ie, it is located on the visited network), the IP address of the mobile node and/or the contact of the MR on the network is called the care-of address (CoA, Care-of). -Address). In addition, when the mobile node and/or MR are not on the primary network (ie, it is located on the visited network), the mobile node and/or MR will use the IP of the FA as its own care-of address.

The mobile node and/or the MR need to inform the master agent of the care-of address that it is currently using. This action is called registration.

In addition, the Access Point (AP) that the Visiting Agent (FA) can manage may be one or more. As shown in FIG. 2, the visiting agents 220 and 240 manage the access points 222 and 242, respectively, and the visiting agent 230 manages the two access points 232 and 233.

In addition, pre-set referral forms are recorded in the main agent, all visiting agents along the line, the mobile node, and/or MR. As shown in FIG. 2, the handover forms 211, 221, 231, 241, and 251 are recorded in the main agent 210, the visit agents 220, 230, 240, and the MR 101, respectively.

It will now explain how to automatically set the referral form. Figure 3 shows a flow diagram of an automatic setup of a handover form in accordance with an embodiment. In this embodiment, before the departure of the mass transit vehicle 100 or before the mass transit vehicle 100 reaches the next FA along the line, a referral form is established in advance (ie, the master agent and the mass transit vehicle are pre-established). a channel between the main agent and the visiting agent; the visiting agent pre-authorizes the mass transit vehicle and allocates the network resources available to the mass transit vehicle; the mass transit vehicle knows the visiting agent in advance The configured network resources, and the mass transit vehicle pre-completes the connection settings to the visiting agent). The following is an example of pre-establishing a transfer form before the departure of the mass transit vehicle 100, and it is to be understood that the present invention is not limited thereto.

As shown in FIG. 3, first, the master agent 210 obtains information in the handover table of the MR 101, for example, MR_CoA, MR_MAC, connection parameters, authentication key, and IP address of each stop (ie, each FA). (FA_CoA) and MAC address (FA_MAC), etc. Next, the master agent 210 assigns the primary address of the MR 101 and informs the MR 101 of the assigned primary address. Next, MR 101 will launch its AA interface (for example, 3G/3.5G/Wimax network interface card) to get its transfer address (AA_CoA) on the AA subnet and prepare it with the AA subnet. After the connection, MR 101 registers the AA subnet care-of address (AA_CoA) with the master agent 210. A tunnel between the MR 101 and the master agent 210 is established via the AA network. The communication between MR 101 and master agent 210 is as shown in step 310.

Then, from the starting station to the destination station, since the master agent 210 has learned the IP address (FA_CoA) and the MAC address (FA_MAC) of each of the stopping stations (ie, each FA), the master agent 210 is The MR 101 pre-establishes a passage between a number of FAs (e.g., FAs 220, 230, and 240) before driving or while traveling but not yet reaching the predetermined position. The communication between the master agent 210 and the FAs 220, 230, and 240 is as shown in steps 320A-320C.

Thereafter, the master agent 210 notifies each FA of related information (such as MR_CoA and MR_MAC) in the handover table of the MR 101, as shown in steps 330A-330C. In this way, each FA is pre-authorized and set the network resources available to the MR.

Thereafter, the master agent 210 notifies the MR 101 of the FA_CoA and FA_MAC of each of the docking stations, as shown in step 340. Thereby, the MR 101 can obtain the authorization of the FA in advance and know the network resources allocated by the FA to the MR 101, and the MR 101 can complete the connection setting of the FA in advance.

At this point, the transfer form has been pre-completed before the MR101 enters the stop, and the channel is established in advance (the passage between the main agent and the mass transit vehicle, and the passage between the main agent and the visit agent); Authorizes the mass transit vehicle and allocates the network resources available to the mass transit vehicle; the mass transit vehicle knows in advance the network resources configured by the visiting agent, and the mass transit vehicle pre-completes the link to the visiting agent set up.

Below, it will explain how to set up the network connection during the train operation phase.

When the mass transit vehicle 100 enters the station, the MR 101 and the FA in the station quickly establish an SA network connection according to the previously obtained MR_MAC and FA_MAC. The data transmission between the MR 101 and the FA in the station can be directly forwarded using the layer 2 layer without IP routing.

In addition, the channel between the over-the-air FA and the master agent can be deactivated. For example, when the mass transit vehicle is routed to the FA 230 via the FA 220, the passage between the FA 220 and the main agent 210 can be deactivated.

The main agent will add a channel to the next FA in the direction of travel as required.

In addition, if the MR's AA subnet forwarding address (AA_CoA) changes, the MR needs to re-register the new AA_CoA with the master agent and re-establish the channel between the two parties.

Before the next FA on the arrival path of the MR/MN (ie the mass transit vehicle), the MR/MN already knows the information of the next FA (eg FA_CoA, FA_MAC, etc.), and the MR/MN also knows the next FA configuration. Give the MR/MN resources and complete the network settings. Moreover, the next FA also knows the information of the MN and its resources to be allocated to the MR/MN.

In addition, when the itinerary of the mass transit vehicle 100 changes, for example, the mass transit vehicle 100 has to go through a new station (this new station includes a new visiting agent and a new AP), here, "new field "Station" means a station that was not originally in the itinerary planning. In this embodiment, the channel between the master agent and the new agent is pre-established according to the above-mentioned method; the new agent is pre-authorized to the mass transit vehicle, and the network resources available for the mass transit vehicle are allocated; The transport vehicle knows in advance the network resources configured by the new visit agent, and the mass transit vehicle pre-completes the connection settings for the new visit agent. In this way, when the mass transit vehicle stops (or passes) the new station, a network connection can be quickly established between the mass transit vehicle and the new visiting agent.

According to an embodiment of the pre-scheduling action support mechanism, a plurality of channels are established for the transfer between the HA and the MR; wherein one of the channels is via the AA network and the remaining channels are via the SA network. The transfer path of the FA in the SA network is not instantaneous until the mass transit vehicle has arrived, and the MR cannot be connected at the same time.

However, in this embodiment, the data (packet) can be transmitted to the FA in advance, and once the MR is moved into the SA network, the MR can quickly acquire the data. Reference is now made to Fig. 4, which shows a schematic diagram of packet transmission in accordance with an embodiment. As shown in FIG. 4, after the HA 210 receives the packet required by the MR 101, the HA 210 can send the packet to some FAs (such as FA 220, 230, and 240) through the channel, as in steps 410A-410C. Show. Next, the FA performs a packet de-tunnel to know which MR (such as MR 101) the packet is to be sent, as shown in step 420. Next, after the MR 101 moves into the SA network governed by a certain FA (such as FA 220), the MR 101 notifies the FA as shown in step 430. Next, the FA will send the packet to the MR 101, as shown in step 440.

As the train travels, the passage between the HA and the FA will be pre-built, and the passage between the over-the-go FA and the main agent can be closed. These transfer channels mean that the data originally intended to be transmitted to the MR is first transmitted to the FA by the HA, and the FA can recognize and transfer it to the MR. Transfer channels such as IP in IP tunnel, Routing Header, etc. In this embodiment, although there are multiple transfer channels, these transfer channels can maintain transparency, that is, the IP address of the MR and the IP address of the contact are not changed by the transfer.

In summary, because both WLAN and WWAN are based on IP network architecture, MR has multiple and multi-style wireless network interface cards, and the part that is connected to the Internet via wireless wide area network (WWAN) can be connected by WWAN interface card. The mobile phone's data network forms a ready-to-use access channel for MR, called AA, but its bandwidth is narrow. However, the WLAN interface of the MR can be connected to a high-bandwidth SA network during a short inbound stop time. Therefore, most of the time MR has only a low-frequency wide AA network available. In addition, in other embodiments, the FA (SA network) may not be set only in the station, that is, the FA (SA network) may also be placed at other locations other than the station.

In this embodiment, in view of the numerous and diverse service demands in the mass transit vehicle 100, in addition to considering the integration problem of the heterogeneous network (Heterogeneous Network), it is also necessary to consider the quality of the Internet service.

During the driving process, the connection of the MR to the SA network is not continuous. Therefore, in the present embodiment, the delay caused by re-establishing the connection between the MR and the SA network is reduced by the pre-scheduling action support mechanism. .

In an embodiment, the Mobile Node (MN) or MR may always use a fixed IP address (ie, a Primary Address (HoA)), regardless of which wireless communication interface it is in that domain. In this way, the problem of handoff and roaming can be solved. Since the IP does not change, when the MN/MR switches between different wireless network interfaces, all IP connections are not interrupted, and the upper application is not affected. The operation of the program.

However, in the case of mass transit vehicles, there may be many users accessing the Internet at the same time. In this case, if each user (ie, each MN) registers separately (that is, changes hands), there will be a lot of burden. Therefore, in the present embodiment, the hand is changed by the MR. Thereby, the embodiment can solve the problem of handoff.

In addition, since the mass transit vehicle 100 will briefly enter (122 or 132) during travel, the mass transit vehicle 100 can effectively utilize the need for a short-lived high-bandwidth SA network. This is because: (1) the delay to enable WLAN has been shortened; (2) MR has the ability to mediate different needs. Its detailed explanation is as follows.

(1) The WLAN-enabled delay has been shortened: since it has been pre-scheduled, the MR WLAN interface has been registered with the host agent in advance to access the network (for example, the SA network) before the departure. The obtained IP address (ie, the Care-of-Address (CoA)), thus reducing the activation delay time of the link layer and the network layer.

(2) MR has the ability to mediate different needs: the needs of users within the mass transit vehicle 100 (such as MN 110A and 110B) vary. When there is a heavy demand, for example, when a user is in the ftp file, the bandwidth of the AA network will be limited, which will affect all users. Therefore, in the present embodiment, these weight type requirements are delivered when the SA network is available. Since the delay of the network backend has been reduced in this embodiment, users with heavy-duty requirements can effectively use the short-lived high-bandwidth SA network.

In an embodiment, the delay of the SA network on the connection can be reduced and the high frequency width of the SA network can be fully utilized to meet the weight requirement and improve the service quality of the MR.

In the present embodiment, by using the handover form, the presence of each other and the connection parameters of the upcoming MR are known in advance between the MR, the HA, and the respective FAs. When the MR moves between FAs (or SA networks), the Agent Discovery and Registration procedures can be omitted. Each channel is established before use or even before departure. In addition, the track of the train can be mastered, so the time course of the train entering and leaving the station and the time course of connecting with the FA are known, so the complex timeout mechanism used by the prior art is not necessary, regular The Binding Update can also be omitted.

This embodiment can greatly reduce the delay of the MR connected to the SA network for three reasons:

(1) Use the hand-over form to simplify the management and control procedures, as long as the channel for transferring data is established.

(2) Since the primary address of the MR can be planned and set in advance, there is no need to perform Duplicate Address Detection (DAD) of the IP layer.

(3) The handover form not only helps to shorten the connection delay of the network layer (layer 3), but also provides the connection parameters of the layer 2 layer, which can also reduce the connection delay of the link layer. In addition, the FA can know the main address of the MR and the MAC address of the WLAN interface in advance. When the FA transmits the data to the MR, the two can directly perform the forwarding of the link layer (Forwarding), and no need to perform the ARP query procedure.

In addition, this embodiment has the following advantages: (1) no search delay: MR has no need to find AP and FA because it has been planned in advance; (2) no authorization, authentication delay: authorization is completed before departure, no It is not authorized until the train station enters the station, so there is no delay caused by authorization and authentication. (3) There is no network layer delay: the network layer delay is caused by the HA to dynamically specify the IP address of the MR. In the example, the IP address of the MR is fixed; (4) there is no location update delay: the MN actively informs the current location of the HA; (5) reduces the packet transmission delay: since the HA sends the packet to the FA in advance, waits until the MR enters After FA's jurisdiction, FA can immediately send the packet to MR, so it can reduce the packet transmission delay; (6) shorten the connection time: because many types of delay have been reduced, the connection time between MR and FA can be It is shortened, so that the MR can make good use of the network bandwidth of the FA; (7) simple implementation and low cost: the implementation of the embodiment does not require additional hardware costs, so the embodiment is simple to implement and low cost; ) can be combined with the planning of the application layer.

In summary, although the above has been disclosed by way of example, it is not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100. . . Mass transit vehicle

105. . . route

101. . . Mobile router

110A, 110B. . . Action node

120, 130, 140, 150, 160. . . Subnet

121, 131. . . Access point

122, 132. . . Depot

141, 151, 161. . . Base station

210. . . Master agent

220, 230, 240. . . Visiting agent

211, 221, 231, 241, 251. . . Transfer form

222, 232, 233, 242. . . Access point

310, 320A~320C, 330A~330C, 340, 410A~410C, 420, 430, 440. . . step

Figure 1 shows a schematic diagram of a mobile network moving according to a given itinerary according to an embodiment.

Figure 2 shows a schematic diagram of an automatic setting of a handover form in accordance with an embodiment.

Figure 3 shows a flow diagram of an automatic setup of a handover form in accordance with an embodiment.

Figure 4 shows a schematic diagram of packet transmission in accordance with an embodiment.

100. . . Mass transit vehicle

101. . . Mobile router

110A, 110B. . . Action node

210. . . Master agent

220, 230, 240. . . Visiting agent

211, 221, 231, 241, 251. . . Transfer form

222, 232, 233, 242. . . Access point

Claims (16)

A network link establishment method for use in a mass transit system for establishing a mass transit vehicle, a network connection between a host network and a visited network, the master network having a master agent, the master network The visited network has a visiting agent, and the network connection establishing method comprises: pre-establishing a first channel between the main agent and the mass transit vehicle before the mass transit vehicle is departed; Having a second channel between the master agent and the visiting agent before the departure or during the journey to the responsible station of the visiting agent; the visit is assisted by the master agent The agent pre-authorizes the mass transit vehicle and assigns a network resource available to the mass transit vehicle; with the assistance of the master agent, the mass transit vehicle travels before the departure of the mass transit vehicle Before reaching the responsible station of the visiting agent, the network resource configured by the visiting agent is known in advance, and before the public transportation vehicle arrives at the responsible station of the visiting agent, First completing a connection setting to the visiting agent; and when the mass transit vehicle moves into the visiting network, establishing a network connection between the mass transit vehicle and the visiting agent according to the pre-completed connection setting . The method for establishing a network connection according to claim 1, wherein the step of pre-establishing the first channel between the master agent and the mass transit vehicle comprises: obtaining, by the master agent, the mass transit Have one of the first transfer information. The network link establishing method of claim 2, wherein the step of pre-establishing the first channel between the master agent and the mass transit vehicle further comprises: the master agent setting the mass transit A primary address of the vehicle. The method for establishing a network link according to claim 1, wherein the step of pre-establishing the first channel between the master agent and the mass transit vehicle further comprises: obtaining the first part of the mass transit vehicle Transmitting the address and preparing the first connection with the primary network; and the mass transit vehicle registers the first transfer address with the primary agent to establish the primary agent and the public Transport the first passage between the carriers. The network link establishing method of claim 3, wherein the step of pre-establishing the second channel between the master agent and the visiting agent further comprises: the master agent knowing the visiting agent One of the IP addresses and one NIC address. The network link establishing method of claim 2, wherein the step of the visiting agent pre-authorizing the mass transit vehicle and setting the network resource available to the mass transit vehicle comprises: the master The agent informs the visiting agent of the first forwarding information of the mass transit vehicle such that the visiting agent pre-authorizes the mass transit vehicle and sets the network resource available to the mass transit vehicle. The network link establishing method of claim 1, wherein the mass transit vehicle knows in advance the network resource configured by the visiting agent and the mass transit vehicle pre-completes the visiting agent The step of setting the link includes: before the departure of the mass transit vehicle or during the travel without reaching the responsible station of the visiting agent, the master agent of the IP address of the visiting agent and The network card address informs the mass transit vehicle such that the mass transit vehicle is pre-authorized by the visiting agent. The method for establishing a network connection according to claim 1, wherein the step of establishing a network connection between the mass transit vehicle and the visiting agent comprises: the mass transit vehicle and the visiting agent The data is transferred using the link layer. The method for establishing a network connection as described in claim 1, further comprising: deactivating the second channel between the master agent and the visiting agent after the mass transit vehicle leaves the visited network. The method for establishing a network connection as described in claim 1, further comprising: after the public transportation vehicle leaves the visited network, adding a third channel between the main agent and the next visiting agent. . The method for establishing a network link as described in claim 1, further comprising: when the first transfer address of the mass transit vehicle changes, the public transport vehicle re-registers with the master agent The first care-of address; and reconstructing the first channel between the mass transit vehicle and the master agent. The method for establishing a network connection according to claim 5, wherein the visited network is a hotspot access wireless network. The method for establishing a network connection according to claim 12, wherein the mass transit vehicle comprises a mobile router, the mobile router comprising: a first wireless network interface card for connecting to the constant access a wireless network; and a second wireless network interface card for connecting to the hotspot access wireless network. The method for establishing a network connection according to claim 1, wherein the mass transit vehicle accesses the wireless network through a constant access when the mass transit vehicle is not within the coverage of the visited network. And online. The method for establishing a network connection according to claim 12, wherein the first transfer information of the mass transit vehicle comprises: the main address of the mobile router of the mass transit vehicle and the second wireless network a network card address of the road interface card; the IP address of the visiting agent and the network card address; a connection parameter; an authentication key; and information about a thermal access point under the jurisdiction of the visiting agent; And a network information required by the mobile router. The method for establishing a network link as described in claim 1, further comprising: the master agent receiving a packet; the master agent sending the packet to the visiting agent; the visiting agent performing the packet Decapsulation; the visitor agent sends the packet to the mass transit vehicle.