JP2006005607A - Network system and mobile router - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the size of an IP header for capsulization which is added to an original packet not unnecessarily large when a terminal which is present outside merged mobile networks and a terminal inside the merged mobile networks send and receive packets while the transmission and reception of the packets are realized without an unnecessary overhead of packets. <P>SOLUTION: A representative mobile router is determined and other mobile routers request the representative mobile router to register positions to a home agent on their behalf. The representative mobile router acts to capsulize and decapsulize the packets as a proxy and merged mobile networks are regarded as one mobile network. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to tracking control of a mobile network when a plurality of mobile networks having mobile routers are merged.

  Although terminals such as notebook PCs and PDAs can be carried around, packet communication is performed using the home address (IP address assigned without depending on the current position of the terminal to identify the terminal). In this case, the terminal needs to be connected to a home link (a link having a network prefix to which the home address of the terminal belongs). Therefore, when the terminal is carried and connected to a link other than the home link (visit link), the terminal cannot continue packet communication using the home address. The link means an area having a common network prefix in the IP network. Packet communication between terminals in the same link is performed without using a router, and packet communication between terminals on different links is performed through a router.

  Mobile IP proposed by the IETF is known as a technique for solving the above problems (see Non-Patent Document 1 and Non-Patent Document 2). By using Mobile IP, even if the terminal moves from the home link and is connected to the visited link, the connection with the terminal on the Internet can be maintained using the home address. This mobile terminal is called a mobile terminal. When the mobile terminal moves from the home link and moves to the visited link, the temporary terminal necessary for communication while in the visited link is necessary. Assigned an address. This temporary address is called a care-of address, and the mobile terminal notifies the care-of address to the home agent. The home agent is a server responsible for managing the location of the mobile terminal and transferring packets to the mobile terminal, and is installed on the home link of the mobile terminal. The notification of the care-of address to the home agent is called location registration. When receiving the location registration, the home agent updates the correspondence table of the home address and care-of address of the mobile terminal managed by the home agent. Thereafter, the home agent captures the packet addressed to the mobile terminal that has reached the home link, and checks the current care-of address of the mobile terminal to which the packet is to be transferred from the correspondence table of the home address and care-of address. Forward the IP packet with an IP header with the destination address as its care-of address. The mobile terminal receiving it removes the IP header added by the home agent and takes out the original packet. In addition, such an action of adding or removing an IP header to a packet is called encapsulation or decapsulation, respectively.

  In addition, the IETF NEMO working group is discussing mobile routers that have expanded Mobile IP mobile terminals and provided router functions (see Non-Patent Document 3). The function of the mobile router is basically the same as that of the mobile terminal, and is to register its care-of address with the home agent. However, the home agent for the mobile router captures packets addressed to terminals in the mobile network managed by each mobile router in addition to packets addressed to the mobile router managed by the mobile router. Refer to the correspondence table and encapsulate the IP address to the mobile router's care-of address and transfer it. When receiving the message, the mobile router performs decapsulation, extracts the original packet, and transfers it by referring to the route table in the same manner as an ordinary router. As a result, the transferred packet reaches the target terminal. In order to realize the above mechanism, the home agent must recognize the correspondence of which mobile router manages which mobile network. For this purpose, the mobile router manages the method in which the home agent has a correspondence table in advance and the packet that the mobile router sends to the home agent for location registration. There is a method of adding information on a mobile network, and either method may be used.

  Conversely, when a packet is sent from a terminal that exists in a mobile network managed by the mobile router to a terminal in a fixed network (a fixed network outside the mobile network), the transmitted packet is moved. Reach the mobile router via each router in the network. When the mobile router forwards the packet normally, the packet reaches the target terminal. Alternatively, the mobile router may encapsulate the received packet addressed to the terminal in the fixed network with the IP header addressed to the home agent address of the mobile router itself. In this case, the packet encapsulated by the mobile router reaches the home agent of the mobile router, and the home agent performs decapsulation and extracts the original packet. After extracting the original packet, it is processed as a normal packet and transferred according to the routing table. In any of the above methods, the packet reaches the target terminal, but it is recommended to perform encapsulation by the mobile router for the following reason. There is a possibility that filtering by the source IP address is performed on each router that passes from the sending terminal to the receiving terminal. At this time, if the mobile router forwards the packet as it is, the packet is filtered by that filtering. There is a possibility of being destroyed. By encapsulating in the mobile router, the encapsulated packet looks like a packet transmitted from one of the visited link terminals, and is not discarded by the filtering.

In the following description, the method of encapsulating the mobile router will be described in the present specification. However, as long as the problem of the present invention can be solved, a method that does not encapsulate may be used.
Using a mobile router eliminates the need for location registration for each terminal in the mobile network when the mobile network moves. As a result, the amount of signal for location registration can be reduced, Each terminal has an advantage that it does not have to have a function as a mobile terminal.

IP Mobility Support for IPv4 (http://www.ietf.org/rfc/rfc3220.txt)

Mobility Support in IPv6 (http://www.ietf.org/internet-drafts/draft-ietf-mobileip-ipv6-24.txt) Nemo Basic Support Protocol (http://www.ietf.org/internet-drafts/draft-ietf-nemo-basic-support-02.txt)

Multiple mobile routers are physically connected to each other by wired or wireless media, and one of these mobile routers becomes a gateway to a fixed network (a fixed network outside the mobile network). A situation may occur where a terminal in a mobile network managed by the terminal and a terminal in a fixed network perform packet communication. In this way, when a plurality of mobile routers are connected to each other to form a nested structure, it is called “mobile networks merged”, and it is called a mobile network in which a set of mobile networks formed by merging is merged.
After mobile networks merge and form a merged mobile network, when a packet communication is performed between a terminal in the fixed network and a terminal in the mobile network merged, each is encapsulated via a plurality of home agents. As a result, the packet size becomes larger than before the merge, and the route becomes redundant. In addition, when a terminal existing in a mobile network managed by another mobile router transmits and receives packets, the packet passes through a home agent existing outside the merged mobile network, and the route becomes redundant. .
As described above, after the mobile networks are merged, each of them is encapsulated via a plurality of home agents. Therefore, there is a problem that the route becomes redundant and the packet size becomes larger than before the merge. As a result, Mobile IP functions such as encapsulation and decapsulation increase the amount of processing in the mobile router, reduce the throughput, and increase the packet size by the amount of the encapsulation header, making it difficult to effectively use the bandwidth. Hereinafter, these problems will be described in detail with reference to FIG.

  FIG. 2 shows a diagram of the network when the mobile networks are merged. There are mobile networks 10, 20, and 30 having mobile routers 11, 21, and 31, respectively, and the mobile routers 11, 21, and 31 have radio antennas 13, 23, and 33, respectively. The home addresses of the mobile routers 11, 21, and 31 are HoA1, HoA2, and HoA3, and the network prefixes of the mobile networks 10, 20, and 30 are represented as MNW1, MNW2, and MNW3, respectively. A fixed network outside the mobile network is called a fixed network 40. Assume that home agents 41, 42, and 43 that are home agents of the mobile routers 11, 21, and 31 exist on the fixed network 40, and their IP addresses are HA1, HA2, and HA3. A plurality of routers and terminals exist in the mobile networks 10, 20, and 30, respectively, and one of the terminals existing therein is called a terminal 12, 22, and 32, respectively. The IP addresses of the terminals 12, 22, and 32 are MNN1, MNN2, and MNN3, respectively.

Here, mobile routers 11 and 21 are physically connected to mobile routers 21 and 31 by wired or wireless media, and either mobile router 11, 21, or 31 is fixed as a gateway to a fixed network. Assume packet communication with the network. This is said to be that these three mobile networks merged to form a merged mobile network 50. Here, it is assumed that the mobile router 21 receives a router notification from the mobile router 11 and uses the mobile router 11 as a default gateway, and the mobile router 31 receives a router notification from the mobile router 21 and uses the mobile router 21 as a default gateway. As a result, the mobile router 11 becomes a gateway between the mobile network 50 and the fixed network 40 merged.
When a packet is transmitted and received between a terminal existing in the mobile network 10 and a terminal existing in the fixed network 40, the mobile router 11 is the only mobile router through which the packet passes, whereas the mobile network 30 Assume that the mobile routers 11, 21, and 31 pass through the packets when packets are transmitted / received to / from terminals existing outside the mobile network merged with the terminals existing inside.

  In FIG. 2, a problem when the packet 80 is transmitted from the terminal 45 existing in the fixed network 40 to the terminal 32 will be described. Since the destination IP address of this packet is MNN3, which is an IP address in the mobile network 30, the packet reaches the home agent 43 that is the home agent of the mobile router 31. Since the home agent 43 maintains a list indicating that the terminal 32 exists in the mobile network 30 and the mobile router 31 is managing the mobile network 30, the packet 80 is referred to this list. Is encapsulated and transferred to the mobile router 31. Here, in order for the packet 80 that has passed through the HA 43 to reach the mobile router 31, it must pass through the mobile routers 11 and 21, so that it also passes through the home agents HA 42 and HA 41 of the mobile routers 11 and 21. It will be. For this reason, since the packet 80 once encapsulated by the HA 43 is further encapsulated by the HA 42 and HA 41, the packet size increases as indicated by the packet 81. This is a problem when the packet 80 is transmitted from the terminal 45 existing in the network 40 to the terminal 32. Note that CoA1, CoA2, and CoA3 in FIG. 2 are care-of addresses of the mobile routers 11, 21, and 31, respectively.

  Next, transmission of a packet from the terminal 12 to the terminal 32 will be described in order to illustrate problems in packet transmission / reception within the merged mobile network. Since the default gateway for the mobile network 10 is the mobile router 11, the packet transmitted from the terminal 12 is transferred to the mobile router 11. The mobile router 11 checks the destination IP address of the received packet. Since the IP address is MNN3 and does not belong to the mobile network 10 managed by the mobile router 11 itself, the destination IP address is encapsulated with the IP header of HA1 and transferred to its home agent 41. Receiving this, the home agent 41 takes out the original packet from the capsule and transfers it. Thereafter, the packets are encapsulated through the home agents 43, 42, 41 in exactly the same way as when packets are transferred from the terminal 45 to the terminal 32 described above. Thereafter, it reaches the terminal 32 via the mobile routers 11, 21, 31. As described above, when packets are transmitted / received between terminals in a mobile network originally managed by another mobile router in the merged mobile network, the packet must pass through a home agent outside the merged mobile network. Rather, the path becomes redundant. Further, when the medium between the mobile network and the ground access point is wireless, this wireless section becomes a bottleneck even when packets are transmitted and received within the combined mobile network. Further, when communication between the gateway and access point of the merged mobile network becomes impossible for some reason, communication becomes impossible even within the merged mobile network. Also, depending on the location of the mobile network to which the packet is sent within the merged mobile network, the size of the IP header added to the original packet by encapsulation becomes larger than before the mobile network merges, and the wireless bandwidth is compressed. In addition to the problem that occurs, there is also a problem that MTU changes.

  According to the present invention, transmission / reception of a packet between terminals existing in a mobile network managed by another mobile router in the merged mobile network is performed only by a normal routing table forwarding process in the merged mobile network. Thus, while realizing without unnecessary overhead of the packet, when the terminal in the mobile network merged with the terminal existing outside the merged mobile network transmits / receives the packet, it is used for the encapsulation added to the original packet. The purpose is not to unnecessarily increase the size of the IP header.

  When there are a plurality of mobile networks and the mobile networks are merged to form a merged mobile network, the representative mobile router among the plurality of mobile routers existing in the merged mobile network is It receives a notification from the mobile router, and possesses a correspondence table of home addresses of other mobile routers and home agent addresses in the merged mobile network. Here, mobile networks are merged when mobile routers in the mobile network are physically connected by some medium, and one of the mobile routers is connected to the fixed network for each mobile network managed by each mobile router. Say to be a gateway.

In the mobile network system described above, the representative mobile router acts as a proxy for location registration of other mobile routers in the merged mobile network, and the representative mobile router serves as the representative for the location registration. The location is notified in association with the home address of the other mobile router.
In the mobile network system configured as described above, the representative mobile router performs encapsulation of a packet transmitted from the mobile network managed by a mobile router other than the representative mobile router to the outside of the merged mobile network. It is characterized by that.

In the mobile network system of the present invention, when a merged mobile network is configured, packet transmission / reception within the merged mobile network uses only normal route information possessed by each router, and routers outside the merged mobile network are used. It can be realized without going through. Further, in the transmission / reception of packets between the inside and outside of the merged mobile network, the size of the IP header added to the original packet for encapsulation is the same as that before the merged mobile network.
Therefore, path redundancy can be prevented, the processing amount in the mobile router is reduced, and the throughput between the merged mobile network and the fixed network is improved. There is an advantage that wasteful use of bandwidth with the network can be kept small.

  When multiple mobile networks were merged, the amount of traffic that increased was less than before each mobile network merged.

A first embodiment according to the present invention will be described. In the network configuration shown in FIG. 3, it is assumed that the mobile networks 10, 20, and 30 operate as independent mobile networks at the beginning, and are each connected to the visited link by leaving the home link. While each mobile network is operating independently, each mobile router 11, 21, 31 is wirelessly connected to the nearest access point 48 using wireless antennas 13, 23, 33, respectively. It is assumed that a care-of address is allocated from the access router 46 bundled by DHCP (Dynamic Host Configuration Protocol), router notification, or the like.
During this time, each mobile router performs location registration with its own home agent. Further, packet communication between a terminal existing in a mobile network managed by itself and a terminal outside the mobile network is realized by performing encapsulation between the home agent and the mobile router.

  From the above state, as shown in FIG. 1, the mobile router 11 and the mobile router 21 are physically connected, and further, the mobile router 21 and the mobile router 31 are physically connected. Thereafter, communication with the fixed network 40 is performed using any one of the wireless antennas 13, 23, and 33. This is because when all of the wireless antennas 13, 23, and 33 are used, collisions occur more frequently and throughput is reduced than when only one of the wireless antennas is used. FIG. 1 shows an example in which the radio antenna 13 is used. As a result, the mobile router 11 connected to the radio antenna 13 becomes a gateway to the fixed network. Therefore, for example, when the terminal 32 in the mobile network 30 transmits a packet addressed to the fixed network, the access point is reached from the wireless antenna 13 via the mobile routers 31, 21, and 11. In this way, the fact that a plurality of mobile routers have a nested structure is referred to as the mobile networks 10, 20, and 30 being merged, and the mobile network 50 formed by merging a set of mobile networks formed by merging.

  At this time, FIG. 4 shows an outline of the operation between each terminal and the router when the present embodiment of the present invention is applied. First, mobile networks merge (FIG. 4: step 270). That is, the mobile routers 11 and 21 are physically connected, the mobile routers 21 and 31 are physically connected, and one of those mobile routers becomes a gateway to the fixed network and is connected to this mobile router. Packet communication is performed between the mobile network 50 and the fixed network 40 which are merged using a wireless antenna. Which mobile router is used as a gateway may be set manually by an administrator, or some automatic setting method may be used. In FIG. 1, the mobile router 11 serves as a gateway to the fixed network, the mobile router 21 receives a router notification from the mobile router 11 and uses the mobile router 11 as a default gateway, and the mobile router 31 receives a router notification from the mobile router 21. The mobile router 21 is the default gateway.

  In the present invention, from the merged mobile network 50 formed as described above, one mobile router manages the correspondence between the home address of the remaining mobile router and the address of the home agent. A mobile router that plays this role is called a representative mobile router. In the merging of the above mobile networks, the mobile router serving as a gateway between the fixed network 40 and the mobile network 50 merged becomes the representative mobile router. Accordingly, in FIG. 1, the mobile router 11 becomes the representative mobile router. The mobile router 11 forwards a packet (representative mobile router notification packet) for notifying that it has become the representative mobile router to other mobile routers in the merged mobile network. (Figure 4: Step 271-a). The mobile router 21 receives this packet and transfers it from all the interfaces other than the interface that received this packet. The mobile router 31 receives this packet (FIG. 4: Step 271-b).

As a result, since the mobile routers 21 and 31 can recognize that the representative mobile router 11 is in the merged mobile network, the mobile routers 21 and 31 themselves do not become representative mobile routers (hereinafter, these are referred to as non-representative mobile routers). Call it.) Thereafter, the mobile routers 21 and 31 which are non-representative mobile routers transmit IP packets requesting proxy for location registration (hereinafter referred to as registration proxy request packets) to the mobile router 11 which is the representative mobile router (FIG. 4). : Step 272-a, b). In response to this, the mobile router 11 transmits a packet for performing location registration on behalf of the home agents 42 and 43 of the mobile routers 21 and 31 (hereinafter referred to as proxy BU) (FIG. 4: Step 273). -a, b). Receiving this, the home agents 42 and 43 transmit BAs, which are packets for notifying that registration has been completed, to the mobile router 11 (FIG. 4: steps 274-a and b). Receiving this, the mobile router 11 transmits to the mobile routers 21 and 31 a packet notifying the completion of the registration proxy (FIG. 4: steps 275-a and b). Thereafter, when the terminal 45 in the network 40 transmits a (user) packet to the terminal 32 in the mobile network 30, it is encapsulated between the home agent 43 and the mobile router 11 (FIG. 4: step). 280-a, b, c). Conversely, a packet transmitted from the terminal 32 to the terminal 45 arrives after being encapsulated between the mobile router 11 and the home agent 43 (FIG. 4: steps 281-a, b, and c).
The above is the outline of the first embodiment. Details will be described below.

FIG. 5 is a functional block diagram of the mobile router of the present invention. In the mobile router 100, 101-1 to 101-n are network interfaces. Reference numeral 102 denotes a mechanism for determining a representative mobile router, which is called a representative mobile router determination processing unit. The representative mobile router determination processing unit has information 131 (referred to as representative mobile router information) regarding the current representative mobile router for itself. Reference numeral 103 denotes a route control unit having a route table 121. A location registration processing unit 104 has a management mobile router table 111 and a management mobile network table 112.
When the mobile network is not combined and operates as a normal mobile router, the route control unit 103 refers to the route table 121 and transfers the packet. In addition, for a packet that needs to be encapsulated, the encapsulation processing unit 105 performs an encapsulation process.

In addition, the location registration processing unit 104 performs location registration processing such as transmitting a packet called BU (Binding Update) to perform location registration to the home agent of the mobile router itself.
Now, as described above, it is assumed that the mobile networks 50 are formed by merging the mobile networks 10, 20, and 30. It is assumed that the mobile router 11 is responsible for the gateway to the fixed network 40 in the merged mobile network.

  At this time, since the mobile router 11 plays the role of the representative mobile router, the representative mobile router determination processing unit 102 of the mobile router 11 sends a packet for notifying that it is the representative mobile router (representative mobile router notification packet). ) From all interfaces. A format example of the representative mobile router notification packet is 300 in FIG. Here, the source address 301 must be set to the IP address assigned to the interface that transmits this packet, and the destination address 302 must be set to a multicast address that represents all mobile routers on the link. . The home address of the mobile router 11 must be stored in the field 303 for the home address of the representative mobile router. The following fields (304, 305, 306) that indicate the priority of the designated mobile router, the cost to the designated mobile router, and the expiration date of this designated mobile router notification packet are not required. You may use it when you want to be notified.

The operation of the mobile router when it receives the representative mobile router notification packet transmitted as described above will be described with reference to FIG. 14-A. When the mobile router receives the representative mobile router notification packet (step 370), the representative mobile router determination processing unit 102 changes the home address 303 of the representative mobile router stored in the packet into the representative mobile router information held by itself. Record (step 371). Then, the process shifts to operate as a non-representative mobile router (step 372). Thereafter, the same packet as the received representative mobile router notification packet (excluding the transmission source address) is transmitted from all interfaces other than the reception interface (step 373).
The mobile router 21 receives the representative mobile router notification packet transmitted by the mobile router 11, recognizes that it is a non-representative mobile router by the operations of steps 371 and 372 in FIG. Record the mobile router's home address HoA1. Further, by 373, this packet is transmitted toward the link where the mobile router 31 exists. The mobile router 31 also receives this, performs the operation of FIG. 14-A, recognizes that it is a non-representative mobile router, and records the home address HoA1 of the representative mobile router.

  After this, the routing protocol is operated between the routing controller of the representative mobile router and the non-representative mobile router (Fig. 5: 103) and between the routing controllers of the non-representative mobile routers (Fig. 5: 103). Exchanges route information of the managed mobile network and home address of each mobile router. As a result, it is not necessary to use the Mobile IP function for transfer in the merged mobile network 50, and transfer is performed according to normal route control.

  Thereafter, the location registration processing units (FIG. 5: 104) of the mobile routers 21 and 31 that are non-representative mobile routers transmit registration proxy request packets to the mobile router 11 that is the representative mobile router (FIG. 4: Step 272). -a, b). A packet format example of the registration proxy request packet is shown in 200 of FIG. 6-A. In the registration proxy request packet, the home address of the non-representative mobile router itself is designated as the source IP address 201, the address of the representative mobile router is designated as the destination IP address 202, and the home agent address of the non-representative mobile router is further stored. 203 is required. In addition, when a packet from a mobile network to a fixed network is encapsulated to a mobile router and a home agent, a field 204 for storing all prefixes of the mobile network managed by the mobile network is necessary. Further, if necessary, a field 205 for storing the expiration date of the registration proxy request packet may be included.

  The location registration processing unit (FIG. 5: 104) of the mobile router 11 that has received the registration proxy request packet creates a table of non-representative mobile routers managed by itself. This is called a management mobile router table and is used by the location registration processing unit 104 of the mobile router as indicated by 111 in FIG. Based on the received registration proxy request packet, the designated mobile router stores a field 221 for storing the home address of the non-representative mobile router in the management mobile router table shown in FIG. 222 must be registered. If the registration proxy request packet includes the expiration date of the registration proxy request, it is registered in the field 223. The expiration date is effective to prevent a useless entry from remaining indefinitely, and an entry whose expiration date has expired is deleted. Using the managed mobile router table, the representative mobile router 11 manages the correspondence between the non-representative mobile router managed by the mobile router 11 itself and the address of its home agent.

  Now, since the mobile router 11 has received the registration proxy request packet from the mobile routers 21 and 31, entries 224 and 225 corresponding thereto are added. In addition, if the received registration proxy request packet includes the prefix of the mobile network of the non-representative mobile router, at the same time, the address of the mobile network managed by each non-representative mobile router and the non-representative mobile router's Create a table that maps home agent addresses. This is called a management mobile network table, and is used by the location registration processing unit 104 of the mobile router as indicated by 112 in FIG. Based on the received registration proxy request packet, the representative mobile router includes a field 231 for storing the mobile network prefix and a field 232 for storing the home agent address of the mobile router in the management mobile network table shown in FIG. 7-B. Must register. If the registration proxy request packet includes the expiration date of the registration proxy request, it is registered in the field 233. Entries 235 and 236 are added by registration proxy request packets from the mobile routers 21 and 31, but the entry 234 of the mobile network 10 which is a mobile network managed by the mobile router 11 itself is also registered from the beginning.

  After that, the location registration processing unit of the mobile router 11 performs the location registration on behalf of the mobile router 21 and the mobile router 31, so that the proxy BU is directed to the home agents 42 and 43 of the non-representative mobile routers 21 and 31. (FIG. 4: Steps 273-a and b). An example of the format of this packet is 210 in FIG. 6-B, where the source IP address field 211 stores the care-of address of the mobile router 11 and the destination IP address field 212 stores the address of the home agent of the non-representative mobile router. The home address field 213 of the representative mobile router, the home address field 214 of the non-representative mobile router, and the validity period field 216 need to store appropriate values. If the prefix of the mobile network managed by the non-representative mobile router is necessary, it may be stored in the field 215.

When the home agent 42, which is the 21 home agent of the non-representative mobile router, receives this proxy BU packet, the packet addressed to the mobile router 21 and the terminal in the mobile network 20 is encapsulated for the care-of address CoA1 of the mobile router 11. The route table of the home agent 42 itself is set so as to be transferred. (Note that the care-of addresses of the mobile routers 21 and 31 are similarly represented as CoA2 and CoA3.) Thereafter, the home agent 42 transmits a BA (Binding Acknowledgment) to the mobile router 11 (FIG. 4: Step 274-). a, b). However, this BA includes the home address of the non-representative mobile router. When the mobile router 11 receives this BA, it sends a packet notifying that the registration proxy has been completed to an appropriate non-representative mobile router (FIG. 4: steps 275-a and b). This packet format may be the same as normal BA. The home agent 43 performs the same operation.
Thereafter, as long as the mobile routers 21 and 31 are non-representative mobile routers, the mobile routers 11 and 31 continue to transmit registration proxy request packets to the mobile router 11 periodically. A proxy BU for location registration of each mobile router is transmitted.

  Packet transmission from the terminal 45 existing in the network 40 to the terminal 32 in the mobile network 30 in a state where the location registration is completed will be described. At this time, the packet transmitted from the terminal 45 is transferred to the home link of the mobile router 31 by normal route control and is captured by the home agent 43. After receiving this packet, the home agent 43 refers to the correspondence table between the home address and the care-of address, checks the care-of address to be transferred, encapsulates it with the address, and transfers it. Here, the captured packet is encapsulated with an IP header addressed to the care-of address of the mobile router 11 and transferred. The operation of the home agent at the time of packet encapsulation is exactly the same as that of the conventional home agent.

  Upon receiving this, the mobile router 11 decapsulates and takes out the original packet, and thereafter, this packet is transferred according to normal route control. This operation will be described with reference to FIG. FIG. 13 is a flowchart showing the operation when the representative mobile router receives a packet. The mobile router 11 receives the packet encapsulated by the home agent (step 501), and the route control unit (FIG. 5: 103) searches the route table (FIG. 5: 121) (step 502). From the routing table search result, it is known whether or not this packet is addressed to the mobile router 11 itself (step 503). Since this packet is addressed to the mobile router, it is next determined whether or not the packet is an encapsulated packet (step 504). Since this packet is encapsulated, the encapsulation processing unit (FIG. 5: 105) performs decapsulation (step 505), and the route obtained by the decapsulation is routed again by the route control unit. A table search is performed (step 502). As a result, if it is a packet addressed to the mobile router 11 itself, it is passed to an upper layer (TCP layer, UDP layer, etc.) (step 506). Since this packet is addressed to the terminal 32, it is not addressed to itself and is not addressed to the fixed network (step 508), so it is transferred from an appropriate interface shown in the route table (step 507).

The transferred packet reaches the terminal 32 via the mobile routers 21 and 31 and each router in the mobile network 30 (FIG. 4: steps 280-a, b, and c). At this time, the encapsulation of the packet is performed by the home agent 43, and only the IP header with the destination address of CoA1 is added to the original packet. The size of the encapsulated packet 85 is merged by the mobile network. It is exactly the same as the previous size when encapsulated directly from the home agent 43 toward the mobile router 31.
Conversely, it is assumed that a packet is transmitted from a terminal 32 existing in the mobile network 30 to a terminal existing in the network 40. At this time, the packet is transferred to the mobile router 11 via each router in the mobile network 30 and the mobile routers 31 and 21 in accordance with normal route control. The operation of the mobile router 11 that has received this packet will be described with reference to FIG. After the mobile router 11 receives the packet (step 501), the route control unit (FIG. 5: 103) searches the route table (FIG. 5: 121) (step 502). Since this packet is not addressed to the mobile router 11 itself (step 503) and further to the fixed network (step 508), it is encapsulated and transferred to the home agent. The encapsulation processing unit (FIG. 5: 105) refers to the management mobile network table (FIG. 5: 112) to determine the address of the home agent to which this packet is to be transferred (step 509), and performs encapsulation ( Step 510) and transfer to the home agent (Step 507).

Here, since the transmitting terminal belongs to the mobile network 30, it is encapsulated by the IP header addressed to the home agent 43 of the mobile router 31 and transferred. When the home agent 43 receives this packet, it decapsulates and extracts the original packet. The home agent 43 refers to the routing table and transfers this packet. The operation of the home agent at the time of packet decapsulation is exactly the same as the operation of the conventional home agent.
The transferred packet reaches the terminal 45 (FIG. 4: steps 281-a, b, c). At this time, the size of the packet formed by being encapsulated by the mobile router 11 is exactly the same as the size when encapsulated from the mobile router 31 to the home agent 43 before the mobile networks are merged.

  Next, as a communication in the merged mobile network, a case where a packet is transmitted from the terminal 12 in the mobile network 10 to the terminal 32 in the mobile network 30 will be described. When the mobile routers 21 and 31 become non-representative routers, the routing protocol is operating between the mobile routers 11, 21, and 31, and the mobile routers 11, 21, and 31 exist in the merged mobile network. It has already learned where to transfer the packet addressed to the terminal. Therefore, the packet addressed to MNN3 transmitted from MNN1 arrives via these routers according to the route table possessed by each router in mobile network 20, mobile routers 21 and 31, and each router in mobile network 30. On the way, there is no transfer overhead such as Mobile IP encapsulation.

  Next, the operation when changing the access point to which the merged mobile network 50 is connected will be described (hereinafter, the change of the access point is called handover). Assume that the network 50 moves, switches the connection to the access point 49, and a new care-of address is allocated from the new access router 47. FIG. 8 shows a sequence diagram of the handover at this time. When the mobile router 11 acquires a new care-of address at step 250, the location registration processing unit of the mobile router 11 transmits a BU to re-register the new care-of address with the home agent 41 (step 251). In addition to this, the managed mobile router table 111 is referred to, and a new BU is sent to the home agent of the non-representative mobile router in order to re-register a new care-of address with respect to the non-representative mobile router managed by itself (step (step)). 252-a, b). The format example of the packet transmitted at this time is the same as 210 in FIG. 6-B. The home agent 41 sends the BA back to the mobile router 11 after the location registration is updated (step 253). The home agents 42 and 43 also transmit BA to the mobile router 11 (steps 254-a, b). In the above handover method, since the representative mobile router transmits a proxy BU after acquiring a new care-of address, the handover process can be realized at a high speed (compared to a second embodiment to be described later).

  A second embodiment of the present invention will be described. FIG. 9 is a sequence diagram during handover in the second embodiment. Regarding handover processing, the location registration processing unit of the representative mobile router 11 does not voluntarily transmit the proxy BU of the non-representative mobile router managed by itself, but refers to the management mobile router table 111 and Transmits a packet for requesting transmission of a registration proxy request packet to all non-representative mobile routers currently managed by the node (steps 260-a and b). The location registration processing unit of the non-representative mobile routers 21 and 31 that has received this transmits a registration proxy request packet to the representative mobile router (steps 261-a and b), and the location of the representative mobile router 11 that has received it. As in the first embodiment, the registration processing unit transmits the proxy BU to the home agent of each non-representative mobile router. When the mobile router 11 receives the BA from the home agent of the non-representative mobile router, the mobile router 11 sends a packet notifying that the registration proxy has been completed to the appropriate non-representative mobile router (steps 262-a and b). When the target non-representative mobile router receives it, the handover operation ends. According to the present embodiment, at the time of handover, it is ensured that the representative mobile router transmits the proxy BU of the non-representative mobile router even though the non-representative mobile router does not already exist in the merged mobile network. Can be prevented.

  A third embodiment of the present invention will be described. Among the mobile routers in each mobile network, regarding the packet received from the interface connected to the mobile network managed by the mobile router itself, the source IP address of the packet is stored in the mobile network. If it is different from what it should be, there may be a filtering rule that discards the packet without forwarding it. When the mobile router to which such a filtering rule is applied constitutes a merged mobile network, the filtering rule is appropriately changed. When the mobile router possessing the filtering rule becomes a non-representative mobile router, the filtering rule is temporarily released. That is, it sets so that the packet received from the interface connected to the mobile network is not filtered by the source IP address. As a result, a packet transmitted from a terminal in the mobile network toward the fixed network is transferred to the representative mobile router without being discarded by the non-representative mobile router.

  On the other hand, it is assumed that the mobile router to which the filtering rule based on the source address is applied becomes the representative mobile router. At this time, with reference to the management mobile network table 112 possessed by the representative mobile router itself, the mobile network managed by the other mobile routers in the other mobile networks merged should be discarded. Temporarily rewrite the filtering rules so that they are forwarded. As a result, when the terminal in the merged mobile network transmits a packet, if the transmission source address is appropriate, the packet reaches the representative mobile router, and the representative mobile router forwards the packet appropriately. Conversely, even if a terminal existing in the merged mobile network spoofs an address outside the merged mobile network as a source address and sends a packet to a terminal other than the merged mobile network, it is sent by the representative mobile router. Discarded and not transferred outside the merged mobile network.

  As a fourth embodiment, a procedure for automatically determining a mobile router serving as a gateway between a fixed network and a mobile network when the mobile networks are merged will be described. Since the mobile router serving as a gateway becomes a representative mobile router in the merged mobile network as a result, this procedure is called a representative mobile router determination procedure. Packets for determining the representative mobile router are exchanged between the physically connected mobile routers to determine the representative mobile router. A packet for this purpose is called a representative mobile router determination packet, and transmission and reception processing of this packet is performed by a representative mobile router determination processing unit (FIG. 5: 102) possessed by the mobile router of the present invention. The representative mobile router determination processing unit manages information as indicated by 131 in FIG. 11 called representative mobile router information. The representative mobile router information includes the home address (FIG. 11: 311) of the representative mobile router at that time for the mobile router, and the priority of the representative mobile router (FIG. 11: 312. Hereinafter, referred to as priority). The cost from the mobile router having this representative mobile router information to the representative mobile router (FIG. 11: 313, hereinafter referred to as cost), the expiration date of the representative mobile router (FIG. 11: 314, hereinafter referred to as the expiration date). ) Is included. Among them, the home address and the expiration date are essential, but the priority and the cost are not necessarily required. Since priority and cost are used to determine a representative mobile router from a plurality of mobile routers, other determination criteria may be used when these are not used.

  In this embodiment, each mobile router recognizes itself as a representative mobile router before the mobile routers are physically connected. Therefore, the representative mobile router information of the mobile router 11 is initially as 320 in FIG. Since the mobile router 11 initially recognizes itself as the representative mobile router, the home address of the representative mobile router is set to the home address HoA1 of the mobile router 11. The priority is used for determining the representative mobile router, and is set for each mobile router according to some standard. For example, it is conceivable to use the performance of the mobile router, the power intensity of radio waves from the base station, etc. manually set by the administrator. Here, the priority of the mobile router 11 is 3. The cost is a cost from the mobile router to the representative mobile router. For example, a metric used by the routing protocol may be used. At this time, since the representative mobile router of the mobile router 11 is itself, the cost is zero. An appropriate value is set for the expiration date. Similarly, representative mobile router information in the initial state of the mobile routers 21 and 31 is shown as 321 and 322 in FIG.

  The representative mobile router periodically transmits a representative mobile router determination packet from all the interfaces that it has. However, the non-representative mobile router does not periodically transmit the representative mobile router determination packet. The packet format of the representative mobile router determination packet may be the same as the mobile router notification packet indicated by 300 in FIG. In this IP header, the source IP address 301 of the IP header stores an IP address assigned to the interface to be transmitted, and the destination IP address 302 stores a multicast address that means all mobile routers on the link. This packet includes a field 303 for storing the home address of the representative mobile router, a field 304 for storing the priority of the representative mobile router, a field 305 for storing the cost up to the representative mobile router, and the validity of the representative mobile router. A field 306 for storing a time limit is included. At the time of transmitting the representative mobile router determination packet, a representative mobile router determination packet is generated according to the following procedure based on the representative mobile router information. First, the home address, priority, and expiration date (FIG. 11: 311, 312 and 314) of the representative mobile router information possessed by the mobile router are directly used in the corresponding fields (FIG. 10: 303 and 304) of the representative mobile router determination packet. , 306). Finally, the cost of the representative mobile router information (FIG. 11: 313) added to the cost assigned to the interface that transmits this representative mobile router decision packet is added to the field for storing the packet cost (FIG. 10: 305). ).

  Next, the operation when a mobile router receives a representative mobile router determination packet transmitted by another mobile router will be described with reference to FIG. 14-B. When the mobile router receives the representative mobile router decision packet (step 350), the home address of the representative mobile router in the packet (FIG. 10: 303) and the home address of the representative mobile router in the representative mobile router information held by itself (see FIG. 10). 11: 311) are inspected to be identical (step 351). If the results are equal, it is checked whether the cost in the representative mobile router decision packet (FIG. 10: 305) is smaller than the cost in the representative mobile router information (FIG. 11: 313) (step 352). If this result is false, the processing for this packet is finished (step 358). If the result of step 352 is true, each item of the representative mobile router information is updated (step 353). At this time, the value of each item is updated to the value stored in the corresponding item of the representative mobile router determination packet. At this time, it is set to the sender of the representative mobile router determination packet that has received the default gateway in its own route table. In addition, if the mobile router of the packet receiver is operating as a representative mobile router, it will become a non-representative mobile router thereafter (step 354). Finally, representative mobile router determination information is newly generated from the representative mobile router information currently owned by itself, and the representative mobile router determination packet newly generated from all the interfaces other than the interface that received the representative mobile router determination packet in step 350. Is transmitted (step 355), and the processing for this packet is terminated.

On the other hand, if they are not equal as a result of the inspection in step 351, it is checked whether the priority in the representative mobile router determination packet (FIG. 10: 305) is higher than the priority in the representative mobile router information (FIG. 11: 312). (FIG. 14: Step 356). If this result is true, steps 353, 354, and 355 are executed, and the processing for this packet is terminated. If the result of step 356 is false, representative mobile router information is generated, transmitted from the interface that received the representative mobile router determination packet in step 350 (FIG. 14: step 357), and the process ends.

  Based on the above operation, an example of the operation when the representative mobile router is determined in FIG. 1 will be described. However, the costs between the mobile routers 11 and 21 and between the mobile routers 21 and 31 are both 1. Initially, since the mobile routers 11, 21, and 31 recognize themselves as the representative mobile routers, the representative mobile router information held by the mobile routers 11, 21, and 31 is 320, 321, and 322 in FIG. Each of them periodically generates and transmits a representative mobile router determination packet. Now, it is assumed that the mobile router 21 happens to transmit the representative mobile router determination packet first among the three mobile routers. This packet is transmitted to both links where the mobile routers 11 and 31 exist. Receiving this, the mobile router 31 updates its representative mobile router information as shown at 323 in FIG. 11 at step 353, and becomes a non-representative mobile router at step 354. Further, when receiving this, the mobile router 11 generates a representative mobile router determination packet in step 357 and transmits it to the link where the mobile router 21 exists. Upon receiving this, the mobile router 21 updates its representative mobile router information as shown by 324 in FIG. 11 at step 353, becomes a non-representative mobile router at step 354, and newly generates a mobile router information determination packet at step 355. To the link where the mobile router 31 exists. Receiving this, the mobile router 31 updates its representative mobile router information as shown at 325 in FIG. As a result, only the mobile router 11 remains as the representative mobile router, and the remaining mobile routers 21 and 31 become non-representative mobile routers. Further, the mobile routers 21 and 31 can recognize the home address of the mobile router 11, which is a representative mobile router that manages itself. The example in which the representative mobile router 21 first transmitted the representative mobile router determination packet has been described above. However, regardless of the order in which the representative mobile router determination packet is exchanged, the result finally converges to the same result.

  A fifth embodiment of the present invention will be described. From the state in which the mobile networks 10, 20, and 30 in FIG. 1 are merged, the physical connection between the mobile router 11 and the mobile router 21 is disconnected, and the mobile network including only the mobile network 10 and the mobile networks 20, 30 The operation when the mobile network is merged into two networks is described. After that, the mobile router 11 continues to receive an address assignment from the access router through the nearest access point and continues to operate as a representative mobile router. However, since the mobile routers 21 and 31 are disconnected from the physical connection to the mobile router 11 and do not receive the registration proxy request packet from the mobile routers 21 and 31, the mobile router 11 possesses the management mobility. The entries 224 and 225 of the mobile routers 21 and 31 are deleted from the router table 111. If it is necessary at this time, before deleting the entry, by sending a packet for requesting transmission of the registration proxy request packet to the mobile router, it is confirmed whether the mobile routers 21 and 31 really exist. (FIG. 9: 260-a, b and 261-a, b). If a registration proxy request packet is returned, the deletion of the entry is stopped. Further, the entries 235 and 236 of the mobile networks 20 and 30 are deleted from the management mobile network table 112. Thereafter, even if the mobile router 11 moves between base stations, the mobile router 11 does not perform location registration on the home agents 42 and 43 on behalf of the mobile routers 21 and 31. Also, due to the operation of the routing protocol, the entries of the mobile networks 20 and 30 in the route table possessed by the mobile router 11 are deleted. Thereafter, the mobile router 11 does not send packets addressed to terminals existing in the mobile networks 20 and 30. When received, it will be forwarded to the default gateway. In other words, since the mobile router 11 currently exists on the external link instead of the home link, when the mobile router 11 receives a packet addressed to a terminal existing in the mobile networks 20 and 30, it encapsulates it with an IP header addressed to HA1. Transfer with.

  On the other hand, in the mobile network in which the mobile networks 20 and 30 are merged, the mobile router 21 is assumed to be a mobile router that acts as a merged mobile network and a gateway outside the mobile network. At this time, the mobile router 21 is assigned a care-of address from the access router through the nearest access point. The mobile router 21 becomes a representative mobile router, sends a BU similar to that of a normal mobile router to the home agent 42 in order to register its own location, and a bidirectional tunnel between the home agent 42 and the mobile router 21. Hang. Furthermore, the mobile router 21 transmits a representative mobile router notification packet to notify other mobile routers that it has become the representative mobile router. The mobile router 31 receives this and continues to be a non-representative mobile router. However, after that, the representative mobile router of the mobile router 31 is changed to the mobile router 21.

  A sixth embodiment of the present invention will be described. Now, as shown in FIG. 12, it is assumed that trains 410 and 420 have mobile networks 413 and 423, respectively, in the vehicle. In the mobile networks 413 and 423, there are mobile routers 412 and 422, respectively, and their home agents 402 and 403 are responsible for location management of each mobile router and packet transfer to the mobile network. Further, it is assumed that the mobile routers 412 and 422 are connected to the ground network 400 via the ground wireless antenna 401 using the wireless antennas 411 and 421, respectively. Thereafter, the trains 410 and 420 are connected. At this time, when a highly directional wireless medium such as a millimeter wave is used, the reception sensitivity of some antennas on the train side may deteriorate due to the connection of the train. Further, when both the wireless antennas 411 and 421 are used, it is conceivable that the throughput is lowered due to the influence of interference and the increase of collision. Accordingly, here, it is assumed that the mobile network 423 also maintains the connection with the terrestrial network 400 by using only the wireless antenna 411 and connecting the mobile routers 412 and 422 to each other.

  At this time, in the conventional mobile router, when a packet is transmitted / received between the terminal 414 in the mobile network 413 and the terminal 424 in the mobile network 423, or when a packet is transmitted from the terminal 404 in the ground network 400 to the terminal 424. The problem of path redundancy and multiple encapsulation arises. For example, there is a problem that a packet transmitted and received between the train 410 and the train 420 passes through the ground network 400 once. For this problem, using the mobile router of the present invention, the mobile router 412 becomes the representative mobile router, so that in the communication between the ground and the train, the route is made redundant via a plurality of home agents, the packet A wasteful increase in size can be prevented. Further, in packet communication in a train, it is possible to avoid the redundancy of the route that the packet passes through the home agent on the ground, thereby effectively using the radio band and improving the throughput of the mobile router.

  It can be applied to trains. A mobile router is arranged in the network for each organization, and when a plurality of organizations are connected to form one organization, the mobile router that directly performs radio communication with the ground is set as the representative mobile router. All transmission and reception of packets in a train can be realized without using a route table on the ground and without going through a router on the ground, and a terminal in a mobile network managed by a mobile router that hangs on a mobile router of another train When communicating with an external terminal, the increase in packet size due to encapsulation can be kept the same as before connection. Of course, besides the train, various applications are possible within the scope of the technical idea of the present invention.

It is a figure which shows the operation | movement of the packet in the merged mobile network in this invention. It is a figure which shows the operation | movement of the packet in the conventional merged mobile network. It is a figure which shows a mode that several mobile networks are moving independently. In this invention, it is a sequence diagram after transmission / reception of a packet starts between CN and MNN3 after a mobile network merges. It is a functional block diagram of a representative mobile router (representative mobile router) in the present invention. It is a figure which shows the packet format of the packet used at the time of registration agency in this invention. (A: Registration proxy request packet, B: Proxy BU) It is the figure which showed the table used for the representation mobile router registration agency in this invention. (A: Managed mobile router table, B: Managed mobile network table) It is a sequence diagram when the merged mobile network performs a handover in the present invention. (Example 1) It is a sequence diagram when the merged mobile network performs a handover in the present invention. (Example 2) It is a figure which shows the packet format exchanged in order to notify and determine the representative mobile router between the mobile routers in the merged mobile network in this invention. It is a figure which shows the representative mobile router information which the representative mobile router determination process part in this invention possesses. It is a figure showing the example at the time of applying this invention to a railway. It is a flowchart which shows operation | movement when the mobile router of this invention receives a (user) packet. In this invention, it is a flowchart which shows operation | movement of a mobile router when a representative mobile router receives a notification packet (A) and a representative mobile router determination packet (B).

Explanation of symbols

10, 20, 30 Mobile network 11, 21, 31 Mobile router 12, 22, 32, 45 Ordinary terminal 13, 23, 33 Radio antenna 40 Fixed network 41, 42, 43 Home agent 46, 47 Access router 48, 49 Access point 50 Merged mobile network.

Claims (16)

Multiple mobile routers,
A network system having a home agent connected to the plurality of mobile routers via a network and managing location information of the mobile routers,
The representative mobile router of the plurality of mobile routers includes a memory that holds a table in which home addresses of one or more non-representative mobile routers and home agent addresses of the plurality of mobile routers are associated with each other. A network system characterized by The network system according to claim 1, wherein the plurality of mobile routers have a function of determining the representative mobile router from the plurality of mobile routers. The plurality of mobile routers are
A transmission unit for transmitting route information of a mobile network managed by each mobile router to other mobile routers in the plurality of mobile routers;
The network system according to claim 1, further comprising a memory that holds route information of a mobile network managed by another mobile router in the plurality of mobile routers. The network system according to claim 1, wherein the representative mobile router performs location registration of the non-representative mobile router. 5. The network system according to claim 4, wherein the representative mobile router registers the position of the representative mobile router as the position of the non-representative mobile router. The one or more non-representative mobile routers include a transmission unit that transmits an address of a mobile network managed by the mobile router to the representative mobile router,
The representative mobile router includes a memory that holds a table of correspondence between the non-representative mobile router and the mobile network managed by the non-representative mobile router for each of the non-representative mobile routers. 1. The network system according to 1. Encapsulation of packets transmitted from a mobile network managed by one or a plurality of non-representative mobile routers to a network other than the mobile network managed by the representative or non-representative router via the representative mobile router, The network system according to claim 1, wherein the representative mobile router acts as a proxy. Each of the one or more non-representative mobile routers has an interface connected to the mobile network managed by the mobile router,
2. The input packet is transferred even when the source address of the packet input from the interface is an address of a device outside the mobile network managed by the mobile router. Network system. A mobile router connected to a home agent via a network and further connected to one or more other mobile routers;
A transmitting unit that transmits a packet for determining a representative router to at least one of the other mobile routers;
A receiving unit that receives a packet for determining a representative router from at least one other mobile router among the other mobile routers;
A mobile router comprising a representative router determining unit that determines whether or not the own mobile router is a representative router based on the received packet. The transmission unit can transmit route information of a mobile network managed by the mobile router to at least one other mobile router among the other mobile routers,
9. The mobile router according to claim 8, further comprising a memory for holding route information of a mobile network managed by at least one other mobile router among the other mobile routers. When the representative router determining unit determines that the mobile router is the representative router, the representative router determining unit includes a memory that holds a table in which the home address of the other mobile router is associated with the address of the home agent. The mobile router according to claim 8. 10. The mobile router according to claim 9, wherein when the representative router determining unit determines that the mobile router is a representative router, the mobile router performs location registration of the other mobile router. 11. The mobile router according to claim 10, wherein when the representative router determining unit determines that the own mobile router is a representative router, the position of the own mobile router is registered as the position of the other mobile router. When the representative router determining unit determines that the mobile router is a representative router, for each of the other mobile routers, the correspondence between the other mobile router and the mobile network managed by the other mobile router The mobile router according to claim 10, further comprising a memory that holds a table of the following. When the designated router determining unit determines that the own mobile router is the designated router, the own mobile router or the other is sent from the mobile network managed by any of the other mobile routers via the own mobile router. 11. The mobile router according to claim 10, wherein encapsulation of a packet transmitted to a network other than the mobile network managed by the mobile router is performed on behalf of the other mobile router. It has an interface connected to the mobile network managed by its own mobile router,
When the representative router determination unit determines that the mobile router is the representative router, the source address of the packet input from the interface is the address of a device outside the mobile network managed by the mobile router 11. The mobile router according to claim 10, wherein said input packet is transferred.

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