JP2005045678A - Communication method between hosts through network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication method for enabling direct communication between hosts with each other without reworking a NAT (network address translator) of a router. <P>SOLUTION: A controller acquires IP (Internet protocol) addresses of first and second routers and transmits to first and second hosts the IP addresses of the routers of the opposite parties. The first and second hosts transmit a packet to the controller through their own routers. The controller detects transmission source ports in the both routers on the basis of the received packets, and further notifies one host of the transmission source port of the other router and notifies the other host of the transmission source port of the one router. Then, the first host transmits a packet to the transmission source port of the second router. This generates a mapping table of IP addresses and ports in the first host, the first router and second router. Then, the second host transmits a packet designating the IP address and port of the first router. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication method between hosts via a network.

  In order to effectively use the global IP address, recently, a router having a NAT function and an IP masquerade function has been used. The inside of this router (ie NAT) has a different network address space from its outside. NAT interconverts one outer network IP address (usually a global IP address) and an inner network IP address (usually a private IP address). Thereby, a host having no global IP address can connect to a network outside the router via the router.

  Even when there are a plurality of hosts inside the router, each host can be connected to the outside network by using the IP masquerade function. This function assigns a router port to a host when a packet is sent from the host to the external network. The assigned port is sent to the outside network as a source port. From the outside network, the IP address and destination port of the router are specified and the packet is sent to the router. At this time, the destination boat is set as the previously acquired transmission source port. The router can determine which host the packet is addressed by referring to the destination port, and can deliver the packet to the host.

By the way, when such an address translation function is used, the IP address inside the router is concealed from the outside of the router. Then, it is difficult to communicate directly from the outer host to the inner host. If an inside host can be statically assigned to a specific port of the router, direct communication from the outside network to the inside host via that port is possible. In order for hosts to communicate directly, it is necessary to make this assignment to both routers to which each host belongs. However, this method has the following problems.
(1) The user must be able to set the NAT of the router himself. This is possible if the NAT is in a node under its jurisdiction, such as a home router, but it is difficult to set up a NAT that is outside its jurisdiction, such as a router of a service provider. .
(2) The router must have an IP address that can communicate with the other router. If a router having a NAT function is further connected under a router connected to the outside network, and this router has only a private IP address, this router cannot communicate directly with the other router. That is, in such a case, direct communication is not possible.

  The present invention has been made in view of the above circumstances. An object of the present invention is to provide a communication method that enables direct communication between hosts without changing the NAT function of a router.

The communication method according to the present invention includes a first router, a first host connected to the network via the first router, a second router, and a second router connected to the network via the second router. A host and a controller connected to the network are used. The first and second routers have a NAT function and an IP masquerade function. The method further comprises the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination.

The communication method according to the present invention may be as follows. That is, the method includes a first router, a first host connected to the network via the first router, a second router, and a second host connected to the network via the second router. And a controller connected to the network. The first and second routers have a NAT function and an IP masquerade function. The method further comprises the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generate address and port mapping table,
Simultaneously or before and after this, by transmitting a packet from the second host to the source port of the first router, the second host, the second router, and the first router are transmitted to the second router. Generating an IP address and port mapping table with one router;
(6) By transmitting a packet specifying the IP address and the source port of the router to which the other host is connected as a destination from one of the first or second hosts, to the other host The step of delivering this packet.

The communication method according to the present invention may be as follows. The method includes a first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, A controller connected to a network is used. The first and second routers have a NAT function and an IP masquerade function. The method further comprises the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects the transmission source port of the first router based on the analysis of the packet transmitted in the step (3), and notifies the second host of data representing the transmission source port. Step to do;
(5) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination.

  The number of packets in steps (3) and (4) in each of the inventions can be plural.

  It is preferable that the TTL is adjusted so that the packet transmitted in the step (5) does not reach the destination router.

  The TTL is adjusted based on, for example, the number of hops from a router to a host connected to the inside of the router.

The communication method according to the present invention may be as follows. The method includes a first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, A controller connected to the network, a first client connected to the first host, and a second client connected to the second host are used. The first and second routers have a NAT function and an IP masquerade function. The method further comprises the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a transmission source port in the first and second routers based on analysis of the packet transmitted in the step (3), and further, one of the first and second routers Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) After the mapping table is generated, the second client transmits a packet designating the port of the first client as a destination to the second host;
(7) After the second host receives the packet in the step (6), a packet including all or part of the payload of the packet is transmitted to the IP address and the source port of the first router. Delivering the packet to the first host by sending it as a destination;
(8) The first host directs the packet including all or part of the payload of the packet transmitted in the step (7) to the port set as the destination in the step (6) in the first client. Sending.

The controller according to the present invention includes a first router, a first host connected to the network via the first router, a second router, and a second host connected to the network via the second router. And a controller connected to the network, and the first and second routers are used in a communication system having a NAT function and an IP masquerade function. This controller performs the following steps:
(1) obtaining IP addresses of the first and second routers themselves;
(2) transmitting the IP address of the second router to the first host and transmitting the IP address of the first router to the second host;
(3) receiving a packet transmitted from the first and second hosts and having a source address and a source port converted by the NAT function and IP masquerade function in the first and second routers, respectively;
(4) Based on the analysis of the packet transmitted in the step (3), a source port in the first and second routers is detected, and further, the router in one of the first and second routers Informing the host connected to the other router of the data representing the source port, and notifying the host representing the source port in the other router to the host connected to the one router.

The second host according to the present invention includes a first router, a first host connected to the network via the first router, a second router, and a second router connected to the network via the second router. Two hosts and the controller connected to the network are used, and the first and second routers are used in a communication system having a NAT function and an IP masquerade function. This second host performs the following steps:
(1) causing the controller to acquire an IP address of the second router itself by sending a packet to the controller;
(2) obtaining an IP address of the first router from the controller;
(3) receiving data representing a source port in the first router from the controller;
(4) After the IP address and port mapping table in the first host, the first router, and the second router is generated in the first router, the IP address and the source of the first router Sending a packet with the port as the destination.

The first host according to the present invention includes a first router, a first host connected to the network via the first router, a second router, and a first router connected to the network via the second router. Two hosts and the controller connected to the network are used, and the first and second routers are used in a communication system having a NAT function and an IP masquerade function. This first host performs the following steps:
(1) causing the controller to acquire an IP address of the first router itself by sending a packet to the controller;
(2) obtaining an IP address of the second router from the controller;
(3) transmitting a packet from the first host to the controller using the NAT function and the IP masquerade function in the first router;
(4) After receiving the information of the source port of the second router from the controller, by transmitting a packet to the source port of the second router, the first host is sent to the first router. Generating a mapping table of IP addresses and ports in the first router and the second router;
(5) A step of receiving, via the first router, a packet transmitted from the second host to the first router by specifying an IP address and a port of the first router.

  A communication system according to the present invention includes the controller according to the present invention, a first host, and a second host.

The communication system according to the present invention may be as follows. The communication system includes a first router, a first host connected to the network via the first router, a second router, and a second host connected to the network via the second router; And the controller connected to the network. The first and second routers have a NAT function and an IP masquerade function. The system performs the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of the data representing the source port in the router, and notifying the host connected to the one router of the data representing the source port in the other router Step to do;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination.

The communication system according to the present invention may be as follows. The system includes a first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, And a controller connected to the network. The first and second routers have a NAT function and an IP masquerade function. The system performs the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of the data representing the source port in the router, and notifying the host connected to the one router of the data representing the source port in the other router Step to do;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generate address and port mapping table,
Simultaneously or before and after this, by transmitting a packet from the second host to the source port of the first router, the second host, the second router, and the first router are transmitted to the second router. Generating an IP address and port mapping table with one router;
(6) By transmitting a packet specifying the IP address and the source port of the router to which the other host is connected from one of the first or second hosts as a destination, to the other host The step of delivering this packet.

The communication system according to the present invention may be as follows. The system includes a first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, And a controller connected to the network. The first and second routers have a NAT function and an IP masquerade function. The system performs the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects the transmission source port of the first router based on the analysis of the packet transmitted in the step (3), and notifies the second host of data representing the transmission source port. Step to do;
(5) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination.

The communication system according to the present invention may be as follows. The system includes a first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, A controller connected to the network, a first client connected to the first host, and a second client connected to the second host. The first and second routers have a NAT function and an IP masquerade function. The system performs the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a transmission source port in the first and second routers based on analysis of the packet transmitted in the step (3), and further, one of the first and second routers Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) After the mapping table is generated, the second client transmits a packet designating the port of the first client as a destination to the second host;
(7) After the second host receives the packet in the step (6), a packet including all or part of the payload of the packet is transmitted to the IP address and the source port of the first router. Delivering the packet to the first host by sending it as a destination;
(8) The first host directs the packet including all or part of the payload of the packet transmitted in the step (7) to the port set as the destination in the step (6) in the first client. Sending.

  The computer program according to the present invention is configured to cause a computer to execute one of the communication methods described above.

  Another computer program according to the present invention is configured to cause the controller according to the present invention to execute each step in the controller.

  Another computer program according to the present invention is configured to cause the second host according to the present invention to execute each step in the second host.

  Another computer program according to the present invention is configured to cause the first host according to the present invention to execute each step in the first host.

  According to the present invention, it is possible to provide a communication method that enables direct communication between hosts without modifying the NAT function of the router.

(First embodiment)
(Network configuration)
A communication method according to the first embodiment of the present invention will be described below. First, an outline of a communication system used in this method will be described with reference to FIG. This system includes a network 1, a first router C, a first host A connected to the network 1 via the first router C, a second router D, and a network 1 via the second router D. And a controller 2 connected to the network 1.

  The network 1 only needs to use the Internet protocol (IP). As a transport protocol, for example, TCP or UDP can be used. There are no restrictions on the configuration of the physical layer. The communication path may be wired or wireless, and the communication medium may be light, electromagnetic waves, or other media.

  The first router C and the second router D have a NAT (Network Address Translator) function and an IP masquerade function. The NAT function is a function for converting a private IP address of a host located inside the router into an IP address for the outside of the router (for example, a global IP address). The IP masquerade function is also called a NAPT (Network Address Port Translator). This function enables communication from the outside network to the host by assigning the port of the router to the host when sending a packet from the host to the network outside the router. Since the NAT function and NAPT function itself are well known, further detailed description is omitted.

  The first router C and the second router D are routers having a NAT function (hereinafter referred to as “last router”) through which a packet sent from a host connected thereunder passes last.

  The first host A and the second host B are, for example, computers equipped with a CPU and a storage device. Further, the first host A and the second host B are provided with computer software for executing these functions (described later). The first host A and the second host B may be home appliances, PDA terminals, and mobile phones that can be connected to a network.

  In this embodiment, only one host is arranged under each router, but it is natural that a plurality of hosts may exist under the router.

  The controller 2 includes, for example, a CPU and a storage device. Further, the controller 2 includes computer software for executing the function (described later). In short, the controller 2 is a server that executes functions to be described later.

これらのＩＰアドレスは、例えば、３２ビットの２進数である（ＩＰｖ４の場合）。ただし、３２ビットのＩＰアドレスを８ビットずつ区切って１０進数で表記することもできる。具体的には、一つのＩＰアドレスは、１０進数を使って、192.168.0.1のように表せる。 Furthermore, in this embodiment, it is assumed that an IP address is assigned to each node (router, host, etc.) as follows.

These IP addresses are, for example, 32-bit binary numbers (in the case of IPv4). However, a 32-bit IP address can be divided into 8 bits and expressed in decimal numbers. Specifically, one IP address can be represented as 192.168.0.1 using a decimal number.

  In this embodiment, it is assumed that each host is assigned a private (that is, non-global) IP address, and each router and controller is assigned a global IP address.

(Communication method)
(Step 2-1 in FIG. 2)
Next, a communication method according to the present invention will be described with reference to FIGS. First, the first host A and the second host B send a packet to the controller 2 (see FIG. 3). For example, the packet sent from the second host B stores Ib as the source IP address. This source IP address is rewritten to the IP address Id of the second router by the NAT function when passing through the second router D. When this packet arrives at the controller 2, the controller 2 can acquire the IP address (source IP address) of the second router D itself. The acquired IP address is stored in a storage unit (for example, a memory or a hard disk) of the controller 2. Similarly, the controller 2 can acquire the IP address of the first router C itself and store it in the storage means. The IP address of each router obtained in this way is “the IP address of the last router”. In this embodiment, the IP address of the last router is acquired via the network. However, in special cases, such as when a global IP address is statically assigned to a router in advance, the router's IP address is obtained without going through the network (that is, using a database storing the IP address). It is theoretically possible.

(Step 2-2 in FIG. 2)
Next, the controller 2 sends the IP address of each router (last router) acquired as described above to each host on the other side (see FIG. 4). Therefore, the first host A acquires the IP address of the second router D. The second host B acquires the IP address of the first router C. Furthermore, the controller 2 sends the IP address of the last router on its own side to each host. These acquired addresses are stored in the storage means of each host.

(Step 2-3 in FIG. 2)
Next, both hosts A and B measure the number of hops to the router (the one having the NAT function) through which the packet from the host finally passed (see FIG. 5). This router is the last router in the path from the host to the outside network.

  The number of hops can be measured as follows using, for example, ICMP (Internet Control Message Protocol). This procedure is the same as the procedure in a tool well known as traceroute.

  First, a UDP packet is transmitted from the host to the router while increasing the TTL in order from 1. Each host acquires the IP address of its own router in the step 2-2. If an ICMP destination unreachable message (for example, ICMP port unreachable) having a router as a source is returned to the source host, the TTL at that time is the number of hops to the router. For example, if a destination unreachable message is returned from the router for a packet with TTL = 1, it is 1 hop.

  An ICMP packet can also be used for measuring the number of hops. In this case as well, the ICMP Echo Request packet is transmitted to the router while increasing the TTL by one as in the case of using the UDP packet. When ICMP Echo Reply is returned for a packet, the TTL at that time is the number of hops to the router.

(Step 2-4 in FIG. 2)
Next, the second host B transmits a packet to a plurality of ports of the controller 2 from a single port. The transmitted packet is subjected to address conversion by the NAT function and the IP masquerade function in the second router D. This operation will be described in more detail with reference to FIG.

  For example, assume that a packet is sent from the transmission port Pb of the second host B to the port Ps of the controller 2. The transmission port Pb is designated in advance by the controller 2, for example. That is, it is assumed that the controller 2 knows the transmission port Pb of the second host B. At this time, the source IP address and the source port in the packet transmitted from the second host B toward the reception port Ps on the controller 2 side are Ib and Pb. Thus, in this specification, a set of an IP address and a port is represented as Ib and Pb.

  The source IP address and source port of this packet are rewritten to those of the router when passing through the second router D, and become Id and Pd. When this packet arrives at the controller 2, the controller 2 can know that the transmission source port Pb has been rewritten to Pd.

  Next, the second host B sends a packet from the transmission port Pb to the port Ps2 of the controller in the same manner as described above. Then, the controller 2 can know that the transmission port Pb has become Pd ′ (may be the same as or different from Pd). The number of attempts to transmit a packet from a single source port to a different destination port may be three or more.

  The first host A also transmits a plurality of packets to the controller 2 in the same manner as the second host B described above. As a result, the controller 2 can know that “the source port Pa has been rewritten to Pc, Pc ′,... By the NAT function of the first router C”.

  The packet transmission from each host to the controller described above may be performed first from either the second host B or the first host A, or at the same time.

(Step 2-5 in FIG. 2)
The controller 2 analyzes the packet received in step 2-4. Of course, the analysis itself may be performed by another computer. Based on this analysis, the controller 2 determines whether the first router C and the second router D have a single source port number by the IP masquerading (NAPT) function when the destination node is switched. Guess and detect whether it is converted to.

In other words, the controller 2 analyzes a port conversion rule when a packet transmitted from the port Pb of the second host B passes through the second router D. Specifically, for example,
(1) When the same port is used, that is, when Pd = Pd ′ = Pd ″, it is assumed that the attached port number Pd2 = Pd.
(2) When the port increases (or decreases), that is, when Pd + 2 = Pd ′ + 1 = Pd ″ holds, it is analyzed that the rule is Pd2 = Pd ″ +1.

  In this way, the controller 2 detects the “source port Pd2 attached by the second router to the next packet sent from the second host B”. A handling method when it cannot be detected will be described later as a second embodiment.

  The controller 2 also detects the source port attached by the first router C to the next packet sent from the first host A by the same analysis (estimation). That is, the transmission source port Pc2 in the first router C attached to the packet transmitted from the port Pa of the first host A is detected.

(Step 2-6 in FIG. 2)
The controller 2 notifies the first host A of data representing the port Pd2 detected in this way (information indicating the port, such as the port itself and its encrypted data). Similarly, the controller 2 notifies the second host B of data representing the port Pc2. That is, the controller 2 notifies one host of the source port used for the next packet transmission by the router (with the NAT function) through which the packet from the other (other party) host passes last. The first host A and the second host B store the notified ports in the storage means.

(Step 2-7 in FIG. 2)
Next, the packet is transmitted from the port Pa of the first host A toward the port Pd2 of the second router D (see FIG. 7). As a result, a mapping table of IP addresses and ports in the first host A, the first router C, and the second router D is generated in the first router C. In other words, the first router C has
Host A <Ia, Pa>,
Router C <Ic, Pc2>,
Router D <Id, Pd2>
Mapping between the two is completed. This means that if Ic and Pc2 are accessed from Id and Pd2, they are transferred to Ia and Pa.

  It is preferable that this packet does not reach the counterpart router. This is because, if a packet specifying the source port of the router arrives at the router before the mapping is formed at the partner router, the port may be prohibited by the NAT function.

  Packets that do not reach the other router can be generated by adjusting the TTL. The TTL is set using the number of hops from the host to the router (the last one in the route to the outside network) acquired in Step 2-6 described above. For example, if the number of hops from the host to the router is set equal to TTL, a packet that reaches the router but does not reach the other router can be generated.

In this embodiment, a packet is transmitted from the second host B to the first host A in the same manner as described above. Thereby, also in the second router D,
Host B <Ib, Pb>,
Router D <Id, Pd2>
Router C <Ic, Pc2>,
A mapping between can be generated. Of course, either mapping may be generated first.

  In many routers, there is a time limit for sessions in TCP and UDP. In particular, the UDP timer is shorter than the TCP timer and is generally 30 seconds. If UDP is used to generate the mapping table, the table is deleted if there is no UDP communication for 30 seconds. Therefore, in order to maintain a long-time connection between the first host A and the second host B, it is necessary to perform communication (UDP communication) for maintaining the connection at an interval shorter than the session time limit. There is.

(Step 2-8 in FIG. 2)
Next, the IP address and port of the partner router are specified, and the packet is transmitted from the host. That is, for example, the second host B transmits a packet in which the IP address and port of the first router C are specified as Ic and Pc2. The second router D changes the source IP address and source port of the packet to <Id, Pd2> by its NAT function and IP masquerade function. This transmission source port Pd2 has been estimated in step 2-5. The first router C that has received this packet delivers this packet to the first host A according to the mapping already formed. Similarly, a packet can be delivered to the second host B by transmitting a packet in which the IP address and port of the second router D are designated as Id and Pd2 from the first host A.

  Therefore, according to the communication method of this embodiment, there is an advantage that direct communication between hosts is possible without modifying the NAT function of the router.

  Further, in the communication method of the present embodiment, even if there is another router in the network path from the host to the last router (the above-described router C or router D), direct communication between the hosts is possible. This is because the packet can be delivered to the inner host by designating the IP address and port of the last router. The inner router may have a NAT function or an IP masquerade function.

(Second Embodiment)
Next, a communication method according to the second embodiment of the present invention will be described with reference to FIGS. In the description of this method, the same parts as those in the first embodiment are referred to above, and the different parts are described.

  The communication method of the second embodiment is used when the transmission source port cannot be detected in step 2-5. For example, some routers assign a random port to the source port for each communication. In such a case, it is difficult to detect the source port. In this case, the steps of FIG. 8 are performed instead of steps 2-5 to 2-8 of FIG.

(Step 8-1 in FIG. 8)
First, the controller detects whether the first or second router C or D has a random port assignment. This detection procedure may be substantially the same as the procedure of step 2-5 in FIG. However, it is determined that the allocation is random when the port detection is unsuccessful. If it is not random assignment, the method of the first embodiment may be performed.

(Step 8-2 in FIG. 8)
When the first or second router C or D has assigned a random port, it is determined whether or not only one router performs such assignment. This can be performed based on whether or not the detection in step 8-1 (detection of random assignment) has been performed in both routers.

  If the router that performs random port assignment is only one of the first and second routers, the controller 2 stores the fact that one router performs the random port assignment using, for example, a predetermined flag. Furthermore, the controller 2 stores the source port Pn of the packet received from the other router in the source port estimation (step 8-1).

  If both routers that perform random port assignment are used, communication by this method becomes difficult.

(Step 8-3 in FIG. 8)
If only one router assigns a random port, then it is determined whether the other router detects a port collision. Port collision detection in the router will be described with reference to FIG.

For example, when communication is performed between host X and host Y, a mapping between host X (Ix, Px), router (In, Pn), and host Y (Iy, Py) is generated on the NAT of the router. . Here, it is assumed that communication other than the host Y (host Z) is addressed to the IP address and port (In, Pn) of the router. Then, the NAT function of the router
(A) Detect that Pn is being used for mapping between host X and Y,
(B) For the communication between the hosts X and Z, the mapping between the host X (Ix, Px) and the router (In, Pn), which is a part of the mapping between the hosts X and Z, is not used.
The operation is performed.

  As a result, the router prevents the host Z from communicating with the host X via the router's IP address and port (In, Pn). This is port collision detection in the router.

(Collision detection procedure)
A procedure for determining whether or not a router is to detect collision will be described with reference to FIG. The controller 2 transmits the packet from the port other than the port that received the packet to the port Pn of the other router obtained in Step 8-2 (Step 10-1).

  The host confirms whether or not this packet has been received (step 10-2). If it can be received, it can be determined that the other router does not detect collision (step 10-3). If it cannot be received, it is determined that the router performs collision detection. At this time, communication by this method becomes difficult.

  A series of operations from step 8-1 to collision detection in step 8-3 may be performed a plurality of times.

(Step 8-4 in FIG. 8)
Next, communication is performed from the host on one router (router to which the random port is assigned) to the source port Pn of the other router (router that does not perform collision detection) (see FIG. 11). When this communication starts, a transmission port in one router is also determined, and as a result, direct communication between both hosts becomes possible.

  In this embodiment, the port of the mapping table generated in the other router in step 8-2 is used. However, after detecting that the other router does not detect the collision in step 8-3, a mapping table may be newly created on the other router. The mapping table can be created, for example, by transmitting a packet from a host connected to the other router to an arbitrary port of one router.

  Next, a communication system and a communication method according to the third embodiment of the present invention will be described with reference to FIG. In the description of this embodiment, parts common to the first embodiment are denoted by the same reference numerals, and the description is simplified. In the description of this embodiment, operations different from those of the first embodiment will be mainly described with reference to FIG.

  In the method of the first embodiment, direct communication can be performed between the first host A and the second host B. Here, the destination of the packet transmitted by each host during communication is a value different from the initial destination in the packet, such as (Id, Pd2) and (Ic, Pc2). However, for example, when performing L2TP communication, the port used in the L2TP function normally mounted on the host is fixed to 1701. In the method according to the first embodiment, it is difficult to perform communication in which the use port is fixed as described above. Of course, communication is possible if the implementation program is modified, but this is not realistic.

  In the third embodiment, by placing a proxy host between a router (NAT) and a host (client in the following description), an arbitrary port and a specific port (for example, 1701) are converted, and a direct port using a specific port is used. Communication is possible. This will be described in detail below.

In the following description, each node is defined as follows.

(Step 2-1)
In this embodiment, as shown in Table 1, the first client E is connected under the first host A (see FIG. 12). Similarly, a second client F is connected under the second host B (see FIG. 12). The first and second clients E and F are configured by a computer in the same manner as the host. In this embodiment, the first host A and the second host B function as proxy servers.

  In the method of this embodiment, first, the second client F requests the second host B to communicate with the destination port Pe of the first client E using the transmission source port Pf. Specifically, the second client F sends information including the transmission port Pf used by itself and the reception port (destination port) Pe of the first client E as the destination to the second host B. The second host B stores these pieces of information (including the IP address If of the second client F). On the other hand, the first client E transmits to the first host A that its standby port is Pe, and the first host A stores this information. It is assumed that the first and second clients E and F know the reception port Pe of the first client E.

  Next, the first host A and the second host B send a packet to the controller 2 (see FIG. 3). For example, the packet sent from the second host B stores Ib as the source IP address. This source IP address is rewritten to the IP address Id of the second router by the NAT function when passing through the second router D. When this packet arrives at the controller 2, the controller 2 can acquire the IP address (source IP address) of the second router D itself. The acquired IP address is stored in a storage unit (for example, a memory or a hard disk) of the controller 2. Similarly, the controller 2 can acquire the IP address of the first router C itself and store it in the storage means. The IP address of each router obtained in this way is “the IP address of the last router”. In this embodiment, the IP address of the last router is acquired via the network. However, in special cases, such as when a global IP address is statically assigned to a router in advance, the IP address of the router is acquired without going through the network (that is, using a database that stores the IP address). It is theoretically possible. Since step 2-2 to step 2-7 are the same as those in the first embodiment, description thereof will be omitted. Step 2-8 is as follows.

(Step 2-8)
Next, the second client F transmits a packet having the source of the port Pf to the port Pe of the second host B (the same port as the port Pe of the first client E, for example, 1701). The second host B receiving the packet, based on the information (source IP address If, source port Pf, destination port Pe) received from the second client F in step 2-1, determines that the packet is the first client E. It is determined that the packet is addressed, and the IP address and port of the packet are replaced with the values used for generating the mapping table in step 2-7. That is, the second host B replaces the packet of the transmission source (If, Pf) destination (Ib, Pe) from the second client F with the transmission source (Ib, Pb) destination (Ic, Pc2). At this time, the second host B stores the replacement information.

  Next, the second host B transmits the previous packet to the first router C. The second router D changes the packet source IP address and source port to (Id, Pd2) by its NAT function and IP masquerade function. This transmission source port Pd2 has been estimated in step 2-5. The first router C that has received this packet delivers this packet to the first host A according to the mapping already formed.

The first host A that has received the packet replaces the packet of the transmission source (Id, Pd2) destination (Ia, Pa) with the transmission source (Ia, Pa) destination (Ie, Pe). At this time, the first host A stores this replacement information. This replacement process is
(1) The first host A communicates with the first client E from the IP address of the last router on the partner host side received in step 2-2 and the source port of the partner router received in step 2-6. It is recognized from which port of which IP address the packet is received, and (2) which port of the first client E the packet is received from the information of the standby port received from the first client E in step 2-1. This is possible because we are aware of whether or not

Next, the first host A transmits the previous packet to the first client E. As a result, the second client F can deliver the packet to the port Pe of the first client E via the second host B, the second router D, the first router C, and the first host A.
When returning from the first client E to the second client F, the first client E returns to the transmission source port Pa of the first host A. The first host A that has received the packet sends the packet of the transmission source (Ie, Pe) destination (Ia, Pa) to the transmission source (Ia, Pa) destination (Id, Pd2) based on the stored replacement information. And is transmitted to the second router D. The first router C that has received this packet delivers this packet to the second router D according to the already formed mapping. The second router D receiving this packet delivers this packet to the second host B according to the mapping already formed. The received second host B replaces the packet of the transmission source (Ic, Pc2) destination (Ib, Pb) with the transmission source (Ib, Pb) destination (If, Pf) based on the stored replacement information. , Can be delivered to the second client F.

  Thus, according to the method and system of this embodiment, communication with a fixed port is also possible.

  Note that the description of each of the embodiments is merely an example, and does not indicate a configuration essential to the present invention. The configuration of each part is not limited to the above as long as the gist of the present invention can be achieved.

  In addition, the constituent elements (including the host, router, and controller) in each of the above-described embodiments may be present as functional elements. One functional element may be integrated with another element, or one element may be realized by a plurality of components or computer software. Furthermore, as a method for realizing the functional elements, hardware or computer software may be used. Furthermore, the connection form between the functional elements may be via a network. That is, a plurality of functional elements may exist at positions separated from each other. For example, the controller described above may be composed of a plurality of servers.

It is a block diagram which shows the schematic structure of the system used for the communication method which concerns on 1st Embodiment of this invention. It is a flowchart for demonstrating the communication method in 1st Embodiment. It is a block diagram for demonstrating the communication method in 1st Embodiment. It is a block diagram for demonstrating the communication method in 1st Embodiment. It is a block diagram for demonstrating the communication method in 1st Embodiment. It is a block diagram for demonstrating the communication method in 1st Embodiment. It is a block diagram for demonstrating the communication method in 1st Embodiment. It is a flowchart for demonstrating the communication method in 2nd Embodiment. It is a block diagram for demonstrating the port collision detection used as the premise of the communication method in 2nd Embodiment. It is a flowchart for demonstrating the communication method in 2nd Embodiment. It is a block diagram for demonstrating the communication method in 2nd Embodiment. It is a block diagram for demonstrating the communication method in 3rd Embodiment.

Explanation of symbols

A 1st host B 2nd host C 1st router D 2nd router E 1st client F 2nd client 1 network 2 controller

Claims (19)

A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network The first and second routers have a NAT function and an IP masquerade function, and further include the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network The first and second routers have a NAT function and an IP masquerade function, and further include the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generate address and port mapping table,
Simultaneously or before and after this, by transmitting a packet from the second host to the source port of the first router, the second host, the second router, and the first router are transmitted to the second router. Generating an IP address and port mapping table with one router;
(6) By transmitting a packet specifying the IP address and the source port of the router to which the other host is connected from one of the first or second hosts as a destination, to the other host The step of delivering this packet. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network The first and second routers have a NAT function and an IP masquerade function, and further include the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects the transmission source port of the first router based on the analysis of the packet transmitted in the step (3), and notifies the second host of data representing the transmission source port. Step to do;
(5) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination.   The communication method according to claim 1, wherein there are a plurality of packets in the steps (3) and (4).   The communication method according to claim 1 or 2, wherein the TTL is adjusted so that the packet transmitted in the step (5) does not reach a destination router.   6. The communication method according to claim 5, wherein the TTL adjustment is performed based on the number of hops from the router to the host connected to the inside of the router. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network And a first client connected to the first host and a second client connected to the second host, and the first and second routers have a NAT function and an IP masquerade function. And further comprising the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a transmission source port in the first and second routers based on analysis of the packet transmitted in the step (3), and further, one of the first and second routers Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) After the mapping table is generated, the second client transmits a packet designating the port of the first client as a destination to the second host;
(7) After the second host receives the packet in the step (6), a packet including all or part of the payload of the packet is transmitted to the IP address and the source port of the first router. Delivering the packet to the first host by sending it as a destination;
(8) The first host directs the packet including all or part of the payload of the packet transmitted in the step (7) to the port set as the destination in the step (6) in the first client. Sending. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network And the first and second routers are used in a communication system having a NAT function and an IP masquerade function, and further execute the following steps: :
(1) obtaining IP addresses of the first and second routers themselves;
(2) transmitting the IP address of the second router to the first host and transmitting the IP address of the first router to the second host;
(3) receiving a packet transmitted from the first and second hosts and having a source address and a source port converted by the NAT function and IP masquerade function in the first and second routers, respectively;
(4) Based on the analysis of the packet transmitted in the step (3), a source port in the first and second routers is detected, and further, the router in one of the first and second routers Informing the host connected to the other router of the data representing the source port, and notifying the host representing the source port in the other router to the host connected to the one router. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network The first and second routers are the second host used in a communication system having a NAT function and an IP masquerade function, and further execute the following steps: Second host:
(1) causing the controller to acquire an IP address of the second router itself by sending a packet to the controller;
(2) obtaining an IP address of the first router from the controller;
(3) receiving data representing a source port in the first router from the controller;
(4) After the IP address and port mapping table in the first host, the first router, and the second router is generated in the first router, the IP address and the source of the first router Sending a packet with the port as the destination. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network The first and second routers are the first host used in a communication system having a NAT function and an IP masquerade function, and further execute the following steps: First host:
(1) causing the controller to acquire an IP address of the first router itself by sending a packet to the controller;
(2) obtaining an IP address of the second router from the controller;
(3) transmitting a packet from the first host to the controller using the NAT function and the IP masquerade function in the first router;
(4) After receiving the information of the source port of the second router from the controller, by transmitting a packet to the source port of the second router, the first host is sent to the first router. Generating a mapping table of IP addresses and ports in the first router and the second router;
(5) A step of receiving, via the first router, a packet transmitted from the second host to the first router by specifying an IP address and a port of the first router.   A communication system comprising the controller according to claim 8, the first host according to claim 10, and the second host according to claim 9. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network A communication system comprising the controller,
The first and second routers have a NAT function and an IP masquerade function,
Furthermore, a communication system that performs the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of the data representing the source port in the router, and notifying the host connected to the one router of the data representing the source port in the other router Step to do;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network A communication system comprising a controller,
The first and second routers have a NAT function and an IP masquerade function,
Further communication system for performing the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a source port in the first and second routers based on the analysis of the packet transmitted in the step (3), and further detects one of the first and second routers. Notifying the host connected to the other router of the data representing the source port in the router, and notifying the host connected to the one router of the data representing the source port in the other router Step to do;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generate address and port mapping table,
Simultaneously or before and after this, by transmitting a packet from the second host to the source port of the first router, the second host, the second router, and the first router are transmitted to the second router. Generating an IP address and port mapping table with one router;
(6) By transmitting a packet specifying the IP address and the source port of the router to which the other host is connected from one of the first or second hosts as a destination, to the other host The step of delivering this packet. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network A communication system comprising a controller,
The first and second routers have a NAT function and an IP masquerade function,
Further communication system for performing the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects the transmission source port of the first router based on the analysis of the packet transmitted in the step (3), and notifies the second host of data representing the transmission source port. Step to do;
(5) A step of delivering the packet from the second host to the first host by transmitting a packet designating the IP address of the first router and the source port as a destination. A first router, a first host connected to the network via the first router, a second router, a second host connected to the network via the second router, and connected to the network A communication system comprising a controller, a first client connected to the first host, and a second client connected to the second host,
The first and second routers have a NAT function and an IP masquerade function, and further perform the following steps:
(1) The controller obtains IP addresses of the first and second routers themselves;
(2) The first host acquires the IP address of the second router from the controller, and the second host acquires the IP address of the first router from the controller;
(3) the first and second hosts transmitting packets to the controller using the NAT function and the IP masquerade function in the first and second routers, respectively;
(4) The controller detects a transmission source port in the first and second routers based on analysis of the packet transmitted in the step (3), and further, one of the first and second routers Notifying the host connected to the other router of data representing the source port in the other router, and sending the data representing the source port in the other router to the host connected to one router Notifying step;
(5) By transmitting a packet from the first host toward the transmission source port of the second router, the IP address in the first host, the first router, and the second router is transmitted to the first router. Generating an address and port mapping table;
(6) After the mapping table is generated, the second client transmits a packet designating the port of the first client as a destination to the second host;
(7) After the second host receives the packet in the step (6), a packet including all or part of the payload of the packet is transmitted to the IP address and the source port of the first router. Delivering the packet to the first host by sending it as a destination;
(8) The first host directs the packet including all or part of the payload of the packet transmitted in the step (7) to the port set as the destination in the step (6) in the first client. Sending.   A computer program that causes a computer to execute the method according to claim 1.   A computer program for causing the controller to execute each step according to claim 8.   The computer program which makes each said 2nd host perform each step of Claim 9. The computer program which makes the said 1st host perform each step of Claim 10.

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