JPH11313109A - Asymmetric route utilizing communication system and asymmetric route utilizing communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an asymmetric route utilizing communication system capable of realizing asymmetric routing in a network system constructed on the assumption that the bidirectional communication of a packet is to be performed by using a bidirectional route. SOLUTION: A reception side gateway (RGW 10) provided in a satellite reception station transmits the packet transmitted from a PC 60 to a server 50 through an internet network 40 (bidirectional route) to a transmission side gateway (SGW 20) provided in a satellite transmission station after performing an address replacing processing and the SGW 20 transmits the packet to the server 50. In the meantime, the SGW 20 transmits the packet transmitted from the server 50 to the PC 60 through a communication satellite 30 (unidirectional route) to the RGW 10 and the RGW 10 transmits the packet to the PC 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an asymmetric communication system constructed by combining a one-way communication path and a two-way communication path.

[0002]

2. Description of the Related Art When communication is performed on an Internet system in which a plurality of different network systems are connected, a protocol for performing data communication between the different network systems and an application program which is located at a higher level between the application programs. 2. Description of the Related Art Hierarchical design of communication protocols such as a protocol for data communication is widely performed.

[0003] Currently widely used routing protocols for exchanging packets between different network systems are designed on the premise that bidirectional communication can be performed on the same path. Therefore, it is not possible to operate an application designed on the assumption that communication can be performed in two directions by using a one-way path such as satellite communication that performs one-way communication from a transmitting station to a receiving station.

One solution is to improve the routing protocol at the network layer so that it can handle one-way routes. In this case, the number of communication devices that need to be improved is a few. It is not realistic because it will be in the scale of 10,000 or more.

In order to perform asymmetric routing using a one-way route without changing a routing protocol based on a two-way route, a proxy server (Proxy server) for relaying an application layer protocol is provided. The proxy server performs a routing using a one-way route, thereby realizing the use of an asymmetric communication route.

[0006]

However, as the application layer protocol, many protocols such as telnet, ftp, http, etc. are standardized and used for each purpose. It is necessary to prepare a corresponding proxy server, and there are problems that the number of types of proxy servers to be prepared increases and that a newly standardized protocol cannot be immediately handled.

Therefore, an object of the present invention is to use a one-way route without changing an existing routing protocol in a network system built on the assumption that bidirectional communication is performed using a two-way route. An object of the present invention is to provide an asymmetric route communication system capable of realizing asymmetric routing and a communication device therefor.

[0008]

In order to achieve the above object, a communication device according to the present invention has a network system constructed on the assumption that bidirectional communication of packets is performed using a bidirectional path, and A communication device that is connected to a different local system from the network system and is provided at a receiving site of a one-way communication system that performs one-way communication of packets using a one-way path, and is transmitted from the local system. The source address of the received packet is replaced with an address (hereinafter, referred to as an "alternate address") previously assigned to the transmitting site of the one-way communication system in the network system, and then the address is replaced. First address replacement means for transmitting a subsequent packet onto the network system, and transmission from the one-way path. If the destination address of the received packet is the substitute address, the substitute address is replaced with the address of the communication device connected to the local system, and the packet after the address replacement is replaced with the local system. And a second address replacing means for transmitting the information to the above.

Further, the communication device of the present invention is connected to a network system constructed on the premise that bidirectional communication of packets is performed using a bidirectional route, and uses a one-way route to transmit packets in one direction. A communication device provided at a transmission site of a one-way communication system that performs communication,
The destination address of the packet transmitted from the network system is an address (hereinafter, referred to as an "alternative address") that is previously allocated in the network system to the transmitting site of the one-way communication system. In such a case, there is provided a routing means for transmitting the packet on the one-way path, and transmitting the packet on the network system when the packet is not the alternative address.

According to another aspect of the present invention, there is provided a network system constructed on the assumption that bidirectional communication of packets is performed using a bidirectional path. A one-way path for performing communication, a communication device (hereinafter, referred to as a “transmission-side gateway”) provided at the transmitting side site of the one-way path and connected to the network system, and The communication system (hereinafter, referred to as a “reception-side gateway”) provided at a reception-side site and connected to the network system and a local system different from the network system, wherein the reception-side gateway includes: The source address of the packet sent from the local system is sent to the sending site on the one-way route. First address replacement means for replacing the address with a pre-assigned address in the network system (hereinafter referred to as “alternate address”) and then transmitting the address-replaced packet to the network system; If the destination address of the packet transmitted from the directional route is the above-mentioned alternative address, the substitute address is replaced with the address of the communication device connected to the above-mentioned local system, and then the packet after the address replacement is replaced. Second address replacing means for transmitting the packet on the local system, wherein the transmitting side gateway transmits the packet if the destination address of the packet transmitted from the network system is the alternative address. If the packet is sent on a one-way route and is not the above alternative address, the packet is Provides an asymmetrical path based communication system characterized by having a routing means for transmitting over the network the system.

Thus, the communication device connected to the local system (hereinafter, referred to as “first type communication device”) and the communication device connected to the network system (hereinafter, referred to as “second type communication device”). When performing communication with the first type of communication device, the packet transmitted from the second type of communication device to the first type of communication device is transmitted using the one-way path. The packet transmitted from the first type of communication device to the second type of communication device is transmitted using the network system (bidirectional path), and the existing routing in the network system is performed. Communication using an asymmetric route can be performed without changing the protocol.

In the above aspect, the first address replacement means of the receiving gateway encapsulates the packet after the address replacement, and then transfers the encapsulated packet to the transmitting gateway via the network system. And when the packet transmitted from the network system is an encapsulated packet, the routing means of the transmission-side gateway can route the packet extracted from the capsule.

In the above aspect, the receiving gateway detects whether or not the one-way route is communicable, and notifies the transmitting gateway of the detection result via the network system. The transmitting gateway further includes a storage unit that stores a detection result notified from the receiving gateway, and the routing unit of the transmitting gateway is configured such that the one-way route cannot communicate. In some cases, the destination address of a packet to be transmitted on the one-way route is replaced with the alternative address, and the packet after the address replacement is transmitted to the receiving gateway via the network system. be able to.

It should be noted that one or more communication devices can be connected to the local system. When two or more communication devices are connected, the local system actually Is a local network system that connects these communication devices.

Further, the network system of the present invention comprises:
A network system that performs transmission and reception of packets between communication devices as basic communication processing, and performs routing on the premise that a route between routers for distributing packets can communicate bidirectionally. A one-way path for one-way communication, a transmitting gateway provided at the transmitting site of the one-way path, connected to the network system, and a transmitting gateway provided at the receiving site of the one-way path, And a network system having an asymmetric route, which further comprises a receiving gateway connected to another local system different from the network system, wherein the receiving gateway converts a packet transmitted from the local system into a packet. The protocol information in the header of If the condition is satisfied, the packet is transmitted as it is on the network system. If the packet does not satisfy the condition, the source address is previously assigned to the transmitting site of the one-way route in the network system. First address replacement means for replacing the replacement address with the alternative address on the transmitting station side and then transmitting the packet after the address replacement on the network system, and the destination address of the packet transmitted from the one-way path being the transmission address. If it is the station side substitute address, after replacing the transmitting station side substitute address with the address of the communication device connected to the local system,
Second address replacing means for transmitting the address-replaced packet to the local system, wherein the transmitting-side gateway is configured such that the destination address of the packet transmitted from the network system is the transmitting station-side alternative address. If the packet is not the alternative address, the packet is transmitted on the one-way route, and if not the routing address, the packet is transmitted on the network system.

Further, in the network system according to the present invention, the receiving-side gateway sets the start address of the packet transmitted from the local system when the protocol information included in the header of the packet satisfies a certain condition. Replaces the receiving site of the one-way route with the receiving station alternative address previously allocated in the network system, and if the packet does not satisfy the above conditions, replaces the source address with the transmitting station alternative address. First address replacement means for transmitting the address-replaced packet onto the network system, and the destination address of the packet transmitted from the one-way path being the receiving station side alternative address or the transmitting station side If it is an alternative address, the receiving station side alternative address or A second address replacement unit that replaces the transmitting station side substitute address with an address of a communication device connected to the local system, and then transmits the packet after the address replacement to the local system; The transmitting gateway transmits the packet on the one-way path if the destination address of the packet transmitted from the network system is the transmitting station side alternative address, and transmits the packet if the destination address is not the substitute address. It is characterized by having routing means for transmitting a packet onto the network system.

Further, in the network system according to the present invention, the receiving gateway replaces a source address of a packet transmitted from the local system with a transmitting station alternative address, and then encapsulates the packet after the address replacement. First address replacing means for transmitting the encapsulated packet to the transmitting gateway via the network system, and the destination address of the packet transmitted from the one-way path is the transmitting station side alternative address. In some cases, the second address replacement means for replacing the transmitting station side substitute address with the address of a communication device connected to the local system, and then transmitting the address-replaced packet to the local system. And the packet sent from the above network system If the packet is a packet that has been packetized, it has routing means for routing the packet taken out of the capsule, and the transmitting side gateway sets the destination address of the packet transmitted from the network system to the substitute of the transmitting station side. If the address is an address, if the protocol information included in the header of the packet satisfies a certain condition, encapsulate the packet and send it to the receiving gateway via the network system.If the condition is not satisfied, The packet is transmitted on a one-way route. If the packet is not the alternative address, the packet is transmitted on the network system. If the packet is an encapsulated packet, routing is performed again on the packet extracted from the capsule. Routing means Characterized in that it has.

[0018] In the network system of the present invention, the transmitting gateway may be configured such that a destination address of a packet transmitted from the network system is:
In the case of the transmitting station side alternative address, if the size of the packet is equal to or less than a specified value, the packet is encapsulated and transmitted to the receiving gateway via the network system, and the above condition is not satisfied. Transmits the packet on a one-way route. If the packet is not the alternative address, transmits the packet to the network system.If the packet is an encapsulated packet, re-route the packet extracted from the capsule. It is characterized by having routing means for performing.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

A communication system using an asymmetric route according to an embodiment of the present invention includes a satellite communication system that is a one-way communication system that performs one-way communication of packets using a one-way route, and a packet communication system that uses a two-way route. It is constructed by combining with the Internet network which is a network system constructed on the premise of performing the two-way communication.

FIG. 1 shows a configuration of a communication system using an asymmetric route according to an embodiment of the present invention. In the figure, 10 is a receiving side gateway (RGW), 11 is a satellite receiver (IR
D), 20 is a transmitting side gateway (SGW), 21 is an uplink station, 30 is a communication satellite, 40 is an Internet network, 50 is a server, and 60 is a personal computer (PC).

As shown in FIG. 1, in this embodiment, an SGW 20 is provided in a satellite transmitting station forming a satellite communication system in addition to an uplink station 21 provided similarly to a conventional satellite transmitting station. I have. Further, an RGW 10 is provided in a satellite receiving station forming a satellite communication system in addition to the IRD 11 provided similarly to a conventional satellite transmitting station.

Here, the RGW 10 is connected to the Internet network 40, and the SGW 20 is connected to the Internet network 40 and one or more PGWs.
The C60 is connected to the connected local network. On the Internet network 40, one or more servers 50 are connected.

Between the satellite transmitting station and the satellite receiving station, one-way communication from the satellite transmitting station side to the satellite receiving station side can be performed via the communication satellite 30, and the Internet network 4
0, two-way communication can be performed.

Further, these communication devices constituting the communication system using an asymmetric route according to the present embodiment may be operated by the same operating entity, or may be operated by separate operating entities. It may be an aggregate.

In this embodiment, the SGW 20 and the RGW 1
0 implements asymmetric routing. It should be noted that the RGW 10 can have a function of realizing asymmetric routing and a function of an IP firewall router.

In order to explain the route of an IP packet at the time of asymmetric routing, first, a normal routing route will be described.

Assuming that the PCa (60a) in the local network communicates with the server a (50a) on the Internet network 40, the start address of the PCa (60a) is “PCa” and the end address is “PCa”. The server a (50a) transmits an IP packet whose start address is "server a" and whose end address is "PCa".

The Internet network 40 is a collection of interconnected routers. The routers exchange route information with each other, dynamically select a route for transmitting a certain packet, and Send a packet. In the currently used routing information exchange protocol, since the route itself has no directionality, the PCa (60a) switches from the server a (5).
0a) and the server a (50)
The IP packet transmitted from a) to PCa (60a) is transmitted in the opposite direction on the same route.

When a one-way route is used in the Internet network 40, in principle, information indicating that the route is one-way exists in the route information used when the router determines a route. In this way, if a router is designed to determine the route in consideration of the direction information of the route, it is obvious that the one-way route can be used without special treatment, but this method works. Requires that all routers on the Internet network 40 be updated to understand route direction information.
It is hardly realistic in terms of cost and labor.

Therefore, the present embodiment discloses a communication system using an asymmetric route that can be realized only by having specific information on the one-way route only by the SGW 20 and the RGW 10 that are specific routers.

In this embodiment, the PCa (60a)
An IP packet transmitted from the server to the server a (50a)
"PCa (60a) → Local network → RGW10 → Internet network 40 → SGW20 → Internet network 40 →
Server a (50a) "and the server a (50a)
The IP packet transmitted from the PC to the PCa (60a) is
"Server a (50a) → Internet network 40 → SGW
20 → Uplink station 21 → Communication satellite 30 →
IRD11 → RGW10 → local network → PCa (60
a) ".

In this embodiment, when a packet is transmitted from the PCa (60a) to the server a (50a), first, in the PCa (60a), the start address is "PCa".
And creates an IP packet whose destination address is “server a” and transmits it to the RGW 10 via the local network. The IP packet at this point is as shown by 1801 in FIG.

The RGW 10 replaces the start address of the IP packet transmitted from the local network side, and as shown at 1802 in FIG.
"a" is rewritten to the alternative address "SNa". here,
As will be described later in detail, the alternative address "SNa" is uniquely assigned to the PCa (60a) at the satellite transmitting station site within the range of the IP address allocated to the satellite transmitting station site from the address management mechanism of the Internet network 40. Is the IP address assigned to. Internet network 4
0 indicates that the destination address is “SN” as described in detail later.
The IP packet “a” holds the route information indicating that the IP packet is delivered to the satellite transmitting station site (that is, the SGW 20).

Next, the RGW 10 transmits the IP packet with the rewritten start address to the SGW 20 via the Internet 40. At this time, the RGW10
, Encapsulates the IP packet to be transmitted in the IP packet and transmits it to the SGW 20. Thus, I
Transmission of an IP packet encapsulating a P packet is generally referred to as “tunneling”. The IP packet outside the capsule has the start address “RGW” and the end address “SGW” as indicated by 1803 in FIG.
W "and transmitted according to a normal routing path.

Now, the SGW 20 converts the encapsulated I
Upon receiving the P packet, the packet is released and transmitted to the Internet network 40. The IP packet transmitted here has a destination address of “server a” and reaches the server a (50a) according to a normal routing path, as indicated by 1804 in FIG.

When the SGW 20 transmits an IP packet having undergone address replacement from “RGW” to “server a”, the RGW 10 transmits the IP packet after the address replacement to the “server a” because the destination address of the IP packet is “server a”. Even if the IP packet after the address replacement is transmitted directly to the Internet network 40, there is a possibility that the IP packet will reach the server a (50a). In this case, the start address "SNa" of the IP packet transmitted from the RGW 10 is changed to the Internet network. Since the IP address is not the IP address assigned to the RGW 10 by the address management mechanism 40, it may be regarded as an invalid IP packet in the Internet network 40. Therefore, in the present embodiment, the SG is temporarily set by tunneling.
W20 to the Internet network 40 from the SGW 20.
, The start address of the IP packet matches the assigned address of the connection site when the IP packet is transmitted to the Internet network 40, and the illegal IP
They are not considered to be packets.

Next, from the server a (50a) to the PCa (6)
The flow of the IP packet transmitted to 0a) will be described. The server a (50a) returns some response to the received IP packet. The IP packet generated at this time has a start address “server a” and an end address as shown in 1901 in FIG. Is an IP packet that is “SNa”. The destination address “SNa” of this IP packet is assigned to the satellite transmitting station site by the address management mechanism of the Internet network 40.
Since the address is within the range of the address, the SGW 20 is routed through the Internet network 40 according to a normal routing path.
Arrives at

The SGW 20 transmits the IP packet to the uplink station 21. The uplink station 21 stores the IP packet as a payload of a satellite data packet and transmits the IP packet to the communication satellite 30.
Then, the data received from the communication satellite 30 is received by the IRD 11, transmitted to the RGW 10, and
Is the destination address "SN" as shown by 1902 in FIG.
"a" is replaced with "PCa" and then transmitted to the local network. This IP packet has the destination address “PC
a ", it is received by PCa (60a)
Communication between (60a) and server a (50a) is established.

The above is the operation at the time of asymmetric routing. Note that the IP address replacement processing and the tunneling processing are well-known techniques, and thus detailed description will be omitted.

In this embodiment, since the Internet network 40 is a network system built on the assumption that bidirectional communication is performed, the server a
Of course, the IP packet transmitted from (50a) to PCa (60a) is transmitted not using a one-way path in the satellite communication system but using a two-way path in the Internet network 40. It is possible.

That is, from server a (50a) to PCa
Explaining the flow of the IP packet transmitted to (60a), when the SGW 20 receives the IP packet transmitted from the server a (50a) via the Internet network 40, the SGW 20 converts the IP packet into the Internet network 4
0 to the RGW 10. At this time, SGW
20 encapsulates the IP packet to be transmitted and then transmits it to the RGW 10. The IP packet transmitted from the server a (50a) has a start address “server a” and an end address “SNa”, as indicated by 1901 in FIG. The IP packet outside the capsule of the IP packet encapsulated by the SGW 20 has the start address “SGW” and the end address “RGW” as shown by 1903 in FIG. Sent according to

Upon receiving the encapsulated IP packet, the RGW 10 releases the encapsulation and replaces the destination address, as shown at 1904 in FIG.
As shown by 1905 in FIG. 10, the destination address “SN”
"a" is rewritten to "PCa". And RGW10
Transmits the IP packet whose destination address has been rewritten to the local network. The IP packet transmitted here has a destination address of “PC” as shown by 1905 in FIG.
a ", it reaches PCa (60a).

In general, in the Internet network, routes are calculated dynamically and routing is performed. Therefore, in a portion where a plurality of routes exist between routers, even if some routes are disconnected, the route between end-to-end The communication can be continued as it is. Data communication using the communication satellite 30 is susceptible to the weather, and when it rains, the error rate is locally 10%.
It is known that it may be close to 0%, so when using a satellite data line, it is important to consider a temporary line break.

Therefore, in the present embodiment, in such a case, the RGW 10 detects the disconnection of the satellite data line, and transmits a request to the SGW 20 via the Internet 40, thereby transmitting the request from the SGW 20 to the RGW 10. The IP packet to be transmitted is transmitted not through the satellite line 30 but in FIG.
As described with reference to FIG. 0, by transmitting through the Internet 40 using the tunneling technique, the RG
One-way route between W10 and SGW20 (satellite data line)
Even if is disconnected, the communication between the PC 60 and the server 50 can be continued without disconnecting the line.

Here, the alternative address "SN" which is an IP address used when performing address replacement in the RGW 10 is described.
In order to describe “a”, first, an IP address system will be briefly described.

The IP address is a fixed-length numerical value for uniquely identifying a communication device that performs communication using the Internet protocol. In the “IP protocol version 4”, the IP address has a 32-bit binary number, In “IP protocol version 6”, the length is 128 bits in binary. The IP address is divided into a network address and a host address, and an IP address whose host address value is all “0” is defined as representing the network itself. Which part of the fixed-length IP address is used as the network address is variable.
The value indicating the delimiter is called a subnet mask value. IP
For details of the address system, refer to RFC (Request for Comments) which is an Internet document.

For successful communication using the IP protocol, it is necessary that different communication devices do not have the same IP address. Generally, the Internet network is operated as a set of networks operated by a plurality of operating entities. Therefore, in order to guarantee the uniqueness of an IP address, some type of address management mechanism is provided, and a certain operating entity has its own local network. Is connected to the Internet network, the address management mechanism assigns a network address capable of accepting a certain number of communication devices, and the IP address of each communication device in the network is assigned.
It is widely practiced that addresses are assigned responsibly so that the operating entity operating the local network is unique. When a certain Internet network is operated by a single operating entity, that operating entity also serves as an address management mechanism.

The satellite transmitting station site receives a network address from an address management mechanism in order to connect to the Internet network 40. At this time, the operator of the satellite transmitting station site has to perform Have a network address large enough to accommodate the total number of alternative addresses needed at the satellite receiver site.

Then, each satellite receiving station site divides a part of its assigned network address and permits the use of an IP address in that range.
The RGW 10 selects an alternative address to be replaced with an address in the local network from an IP address range whose use is approved by the satellite transmitting station site.

The RGW 10 can know the available alternative address by assigning an alternative address to each RGW 10 in advance, or by communicating between the RGW 10 and the SGW 20 to dynamically determine the available alternative address in the RGW 10. Although a method of acquiring the information is conceivable, any method can be used. In this embodiment, each RGW is set in advance.
In this example, a method of assigning an alternative address every 10 is shown.

When realizing the asymmetric routing as described above, it is necessary to operate differently from the communication equipment on the normal Internet network 40 because the RGW 10 and the SG
Since it is W20, the details of these operations will be described below.

First, the RGW 10 will be described.

FIG. 2 shows a hardware configuration diagram of the RGW 10. As shown in FIG. The RGW 10 is a computer system that operates as a router on the Internet network 40. As shown in FIG. 2, the RGW 10 includes a CPU 1001, a memory 1002, a disk controller 1003, and a hard disk 110.
0, a console controller 1004, a console 1200, a network controller 1005, a network controller 1006, and an IRD controller 1007.

The CPU 1001 controls the operation of the entire RGW 10. The memory 1002 stores programs and data. The disk controller 1003 controls the hard disk 1100. Hard disk 1100
Stores programs and data. The console controller 1004 controls the console 1200. The console 1200 performs input and output with a user. The network controller 1005 performs communication with the Internet network 40. Network controller 1
006 performs communication with the local network. The IRD controller 1007 controls the IRD 11. IRD1
1 receives data transmitted from the communication satellite 30, extracts an IP packet from the received data,
Transmit to GW10.

Next, the operation of the RGW 10 will be described. The operation of the RGW 10 is realized by the CPU 1001 executing an RGW processing program described in detail later.

FIG. 4 is a data configuration diagram of the address replacement management table used in the processing by the RGW processing program. As shown in FIG. 4, the address replacement management table 17
00 is composed of an original address field 1701 and an alternative address field 1702.

The original address field 1701 stores the IP address of the PC 60 in the local network, and the alternative address field 1702 stores the value of an alternative IP address for address replacement that has been approved for use by the satellite transmitting station site. Is done.

FIG. 5 is a flowchart of the RGW processing program. As shown in FIG. 5, upon receiving an IP packet from one of the network controller 1005, the network controller 1006, and the IRD controller 1007 (step 1501), the RGW 10 determines whether or not the destination address of the IP packet is itself. Check (step 1502), if so, the protocol type of the IP packet is
It is checked whether the packet is a P packet (step 150).
3).

If the packet is an encapsulated IP packet (step 1503), the packet is an IP packet received from the SGW 20 via the Internet 40 (ie, an IP packet received according to the flow shown in FIG. 10). ), The RGW 10 extracts the encapsulated IP packet (step 1).
504), returning to step 1502, and
Performs processing on packets.

If the packet is not an encapsulated IP packet (step 1503), the RGW 10 proceeds to step 1505 and performs processing on the received IP packet. In this step 1505, various processes according to the Internet protocol are performed, but the process of this portion is not different from the packet process that can be placed in a normal router, and therefore detailed description is omitted. Step 1505
Next, the process proceeds to step 1514.

If the end point address is other than its own (step 1502), the RGW 10 refers to the address replacement management table 1700 to determine whether the start point address matches any of the values of the original address field 1701. Is checked (step 1506).

If they match (step 1506), P
It is an IP packet received from the C60 via the local network (that is, the IP packet received in the flow shown in FIG. 8).
RGW10
Replaces the start address with an alternative address in accordance with the contents of the address replacement management table 1700 (step 1507), and replaces the IP packet after the address replacement with the end address "SGW" and the start address "RG
After encapsulating the IP packet as "W" (step 1508), the encapsulated IP packet is transmitted (step 1511).

If they do not match (step 150)
6), the RGW 10 sets the address replacement management table 170
0, it is checked whether the destination address matches any of the values of the alternative address field 1702 (step 1509). If so, the IP address received from the SGW 20 via the communication satellite 30 is checked. This means that the packet is present (that is, it is an IP packet received in the flow shown in FIG. 9) or is an IP packet extracted in step 1504. , The destination address is replaced with the original address (step 151).
0), otherwise go directly to step 1511.

In step 1511, the RGW 10 sets the I
It checks whether the destination address of the P packet is within the address range assigned to the local network, and if so, to the network controller 1006 the IP address
Send a packet (step 1512); otherwise, send an IP to network controller 1005
The packet is transmitted (step 1513).

When the transmission of the IP packet is completed, RGW1
0 proceeds to step 1514, where the IRD controller 1
Via 007, the IRD 11 confirms whether or not the radio wave from the communication satellite 30 is normally received, and notifies the SGW 20 whether or not the IRD state is normal. In addition,
The notification of the IRD state to the SGW 20 can be performed using a UDP (User Datagram Protocol) packet in the Internet protocol. Also, the notification of the IRD state to the SGW 20 is performed at an appropriate interval (for example, 1 every 10 seconds).
Times).

When the processing of step 1514 is completed, RG
W10 returns to step 1501 to receive the next IP packet.

The above is the processing content of the RGW processing program executed by the RGW 10.

Next, the SGW 20 will be described.

FIG. 3 shows a hardware configuration diagram of the SGW 20. The SGW 20 is a computer system that operates as a router on the Internet network 40. As shown in FIG. 3, the SGW 20 has a CPU 2001, a memory 2002, a disk controller 2003, and a hard disk 210.
0, a console controller 2004, a console 2200, a network controller 2005, and a network controller 2006.

The CPU 2001 controls the operation of the entire SGW 20. The memory 2002 stores programs and data. The disk controller 2003 controls the hard disk 2100. Hard disk 2100
Stores programs and data. The console controller 2004 controls the console 2200. The console 2200 performs input and output with a user. The network controller 2005 performs communication with the Internet network 40. Network controller 2
006 performs communication with the uplink station 21. The uplink station 21 converts the IP packet into a data format used by the communication satellite 30, and transmits the data to the communication satellite 30.

Next, the operation of the SGW 20 will be described. The operation of the SGW 20 is realized by the CPU 2001 executing an SGW processing program described in detail later.

FIG. 6 is a data configuration diagram of the receiving station management table used in the processing by the SGW processing program. As shown in FIG. 6, the receiving station management table 2700 contains the RG
W address field 2701, receiving station address range field 2702, receiving station status field 2703
It is composed of

In the RGW address field 2701,
The IP address of the RGW 10 provided for a certain satellite receiving station is stored, the receiving station address range field 2702 stores the range of alternative IP addresses that can be used by the satellite receiving station, and the receiving station status field 2703 stores R
The value of the IRD state transmitted from the GW 10 is stored.

FIG. 7 is a flowchart of the SGW processing program. As shown in FIG. 7, upon receiving an IP packet from the network controller 2005 (step 2501), the SGW 20 checks whether or not the destination address of the IP packet is itself (step 2501).
2) If so, it is checked whether the protocol type of the IP packet is an encapsulated IP packet (step 2503).

If the packet is an encapsulated IP packet (step 2503), the packet is an IP packet received from the RGW 10 via the Internet 40 (that is, an IP packet received according to the flow shown in FIG. 8). ), The SGW 20 extracts the encapsulated IP packet (step 25).
04), returning to step 2502 to perform processing on the extracted IP packet.

If the IP packet is not an encapsulated IP packet (step 2503), the SGW 20 proceeds to step 2505, where the received IP packet is
UD indicating notification of IRD status transmitted from
It is determined whether the packet is a P packet (step 250).
5).

If the packet is a UDP packet indicating the notification of the IRD state (step 2505), the SGW 20
According to the IRD status signaled by the DP packet,
Receiving station status field 2 of receiving station management table 2700
The value of 703 is updated (step 2506); otherwise (step 2505), the process proceeds to step 2507 to perform processing on the received IP packet. In this step 2507, various processes according to the Internet protocol are performed in the same manner as in step 1505 in FIG. 5, but since the processing in this part is not different from the packet processing in a normal router, a detailed description will be omitted. Omitted.
After the processing in step 2506 or 2507, the process returns to step 2501 to receive the next IP packet.

If the destination address is other than its own (step 2502), SGW 20 determines whether or not the destination address is included in the network address assigned to the satellite transmitting station site (step 250).
8) If not included, proceed to step 2513; if included, receive station management table 2700
, It is checked whether or not the end point address is included in any of the receiving station address range fields 2702 (step 2509).

If it is not included in any of the receiving station address range fields 2702 (step 250)
9) In step 2510, if the address is included in any of the receiving station address range fields 2702 (step 2509), the server 50
0 means that the packet is an IP packet received through the SGW 20 (that is, an IP packet received in the flow shown in FIG. 9 or FIG. 10).
The value of the receiving station status field 2703 of the corresponding satellite receiving station is checked (step 2511). If the reception is normal, the IP packet is transmitted to the network controller 2006 in order to transmit the IP packet according to the flow shown in FIG.
(Step 2510). The IP packet transmitted from the network controller 2006 is received by the uplink station 21 and transmitted to the communication satellite 30.
Sent to

If the receiving station status of the corresponding satellite receiving station is not normally being received (step 2511), the SGW 20 transmits the IP packet according to the flow shown in FIG. The IP address of the RGW 10 is obtained from the value of the RGW address field 2701 of the 2700, and the IP packet is sent to the destination address "RG
W ”, and encapsulated in an IP packet having the start address“ SGW ”(step 2512), and then transmit the encapsulated IP packet to the network controller 2005 (step 2513) in step 2510 or step 2513. After the processing, S
The GW 20 returns to step 2501 and receives the next IP packet.

The above is the processing content of the SGW processing program executed by the SGW 20.

As described above, the RGW 10 and the SGW 10
By the function of the GW 20, an Internet communication system using the satellite data communication path can be constructed, and the user can access the Internet at high speed using the satellite data communication path.

For example, when an application program running on the PC 60 accesses the server 50, data transmitted from the PC 60 to the server 50 is
It is a small amount of data such as various instructions.
The data transmitted to the C60 is generally a large amount of data such as image data and programs. In such a case, by transmitting data transmitted from the server 50 to the PC 60 via a satellite data line capable of transmitting a much larger amount of data than the Internet network 40, Since the transmission time can be shortened, the merit of the user of the PC 60 becomes great.

In particular, in the present embodiment, since asymmetric routing is performed based on information in the network layer, an application program using the upper protocol can operate without any modification. . That is, once the RGW 10 and the SGW 20 are provided, even if the protocol is newly standardized, it can be immediately handled.

Further, according to the present embodiment, when communication using the communication satellite 30 which is a one-way route cannot be performed normally due to a disconnection of satellite data or the like, the communication is automatically performed.
Since communication is performed using the Internet network 40, which is a two-way route, communication can be continued without disconnection even if a temporary abnormality occurs in the satellite data line.

In this embodiment, the RGW 10
When performing the address replacement in the above, the address pair to be replaced is fixed, but it is clear that asymmetric routing can be performed without any problem even if the address pair is dynamically determined.

In this embodiment, the RGW 10
When the address replacement is performed, the one-to-one address replacement is performed between the address in the local network and the network address assigned to the satellite transmitting station site, but the N-to-one address replacement is performed. Obviously, asymmetric routing can be performed without any problem.

When dynamically determining an address pair at the time of address replacement or performing N-to-one address replacement, unless the communication is started from the PC 60 connected to the local network, the route control is properly performed. Although there is a limitation that it cannot be reached, this limitation is a limitation common to the local network where the firewall is installed, and is not a limitation inherent to the present embodiment.

In this case, in the RGW 10, a specific P
If the address of C60 is not replaced, the environment will be the same as that of a normal Internet connection without using a satellite data line. Therefore, a server that is accessed from the outside can coexist on the local network. It is.

In this embodiment, one satellite transmitting station and one satellite receiving station are provided. However, even if one or both of the satellite transmitting station and the satellite receiving station are present, a plurality of satellite transmitting stations and one or more satellite receiving stations are provided. , As it is.

Now, various applications are used on the Internet system, and the characteristics required for the communication path for each application are various. In the case of file transfer, the fastest transmission speed is most important, but t
In an application such as elnet, which requires a small amount of data (light weight) because of being character-based, and does not require much transmission speed, an application that performs interactive processing does not require much transmission speed. Therefore, when using such a lightweight and interactive protocol, it is desirable to use a communication path with low delay even at low speed.

An embodiment in which means for judging whether to use a satellite data line in accordance with a certain standard will be described below. In this embodiment, when the judging means judges that the satellite data line should be used, the PC 60-
When it is determined that the communication between the servers 50 uses one side of the two-way route in the Internet network 40 and the one-way route of the satellite communication system and the conventional Internet network 40 should be used without using the satellite data line, Communication between the PC 60 and the server 50 uses both sides of a bidirectional path in the Internet network 40. In the following embodiment, an example using whether or not a lightweight and interactive protocol is used will be described as the above criterion. This criterion is an example, and is not limited to this.

The system configuration of this embodiment is the same as that of FIG. 1, and the hardware configuration of the RGW is also the same as that of FIG. The hardware configuration of the SGW is the same as that of FIG.
The contents of the GW processing program are the same as those in FIG.

RG describing operation of RGW in this embodiment
FIG. 11 shows a flowchart of the W processing program. In this flowchart, steps 1506 and 150
7 is the same as the flowchart in FIG.

In step 1521, it is determined whether or not the upper layer protocol of the received IP packet is a lightweight / interactive protocol (details will be described later). If YES, the process directly proceeds to step 1511 to perform no replacement of the start address. If the answer is NO, the process proceeds to step 1507 as in the past, where the start point address is replaced. As a result of not performing the address replacement, this packet is sent to the server without passing through the SGW, and the return from the server also reaches the RGW without passing through the one-way route.

The determination of the upper layer protocol is performed as follows.
A lightweight and interactive protocol is a protocol that requires a relatively small amount of data and requires the user to respond directly.
If the transmission delay is large, the user waits for the next response to arrive, and as a result, the usability becomes very poor. The TELNET protocol is a typical example.

The IP packet has information indicating the type of the upper layer protocol in the header. TCP and UDP are widely used as upper protocols of the IP protocol.

As shown in FIG. 16, the TCP protocol has information called a start port number and an end port number in a TCP header, and these values specify an application program using this packet. . By the way, there is a regularity in the assignment of the port number, and a well-known port (well known port) is used.
The numbers 1 to 1023 called t) are defined so as to be used by a specific application protocol, and cannot be used by other applications. For example, the TELNET protocol uses No. 23, and the FTP protocol uses No. 21. For details of the port number assignment in the Internet, refer to RFC.

Therefore, whether a certain IP packet is an IP packet used in the TELNET protocol is determined by determining that the upper protocol type of the IP packet is TCP, and
It can be determined from the fact that either the start port number or the end port number in the CP header is 23.

Therefore, a port number registration table 3100 in which the port numbers of the lightweight and interactive protocol such as TELNET shown in FIG. 17 are registered is prepared in the memory 1002 or the hard disk 1100. In step 1521, the start port in the TCP header is set. Either the port number or the end point port number is the port number.
It is determined that the upper layer protocol is lightweight and interactive based on whether the port number is registered in 00.

According to the present embodiment, a system for performing asymmetrical routing using a one-way route having a high speed but a large delay using RGW and SGW in a network using the Internet protocol is used. By controlling the packet to not pass through a one-way route with a large delay, the speed of the one-way route can be used in non-interactive processing, and the effect of the magnitude of the one-way route delay can be avoided in interactive processing. System can be realized. In addition, since the determination process of the upper layer protocol is performed on the RGW, a system having a plurality of RGWs has a feature that the determination process is dispersed as compared with the case where the determination is performed on the SGW, and the load required for the determination is small.

In the above embodiment, since the address conversion of the packet sent from the PC 60 is not performed at the time of the lightweight / interactive protocol, the PC 60 needs to have a global IP address. Generally, the local network of a satellite receiving station uses a private IP address widely, but in that case, the above-mentioned invention cannot be used. Therefore, an embodiment of the invention applicable to the case where the PC 60 has a private IP address will be described below.

Next, the operation of the RGW according to an embodiment of the present invention for switching a path on the RGW according to application characteristics when the local network of the satellite receiving station has a private IP address will be described.

The system configuration of this embodiment is the same as that of FIG. 1, and the hardware configuration of the RGW is also the same as that of FIG. The hardware configuration of the SGW is the same as that of FIG.
The contents of the GW processing program are the same as those in FIG.

RG describing operation of RGW in this embodiment
FIG. 12 shows a flowchart of the W processing program. In this flowchart, steps 1506 and 151 are performed.
1 is different from the flowchart of FIG. 5, and the other processes are the same as those of the flowchart of FIG.

FIG. 13 shows an address replacement management table 3000 used in the processing by the RGW processing program of this embodiment.
FIG. 4 is a data configuration diagram of FIG. Address replacement management table 30
00 includes an original address field 1701, an alternative address field in the transmitting station 1702, and an alternative address field in the receiving station 1703, and is the same as the address replacement management table 1700 in FIG. 4 except that an alternative address field 1703 in the receiving station is added.

The original address field 1701 contains the PCs 60a, 60b,. . . In the IP address of the transmitting station, an alternative address field 1702 in the transmitting station stores the value of an alternative IP address for address replacement recognized by the satellite transmitting station for substitution, and the alternative address field 17 in the receiving station.
03 stores the value of an alternative IP address for address replacement that is approved for use in the network to which the satellite receiving station belongs. This alternative IP address needs to be a global IP address.

As shown in FIG. 12, if the start address does not match the value of the original address field in step 1506, the end address is changed to one of the alternative address field 1702 in the transmitting station and the alternative address field 1703 in the receiving station in step 1534. It is checked whether or not the destination address matches the value of the destination address. If the values match, the process proceeds to step 1535, where the destination address is replaced with the value of the corresponding original address field.

If the values match in step 1506, the flow advances to step 1531 to determine whether the upper layer protocol is a lightweight and interactive protocol. The processing content of this step is the same as the content of step 1521 in FIG. 11 of the previous embodiment. If the determination result is YES, the process proceeds to step 1533, where the start point address is replaced with the value of the corresponding alternative address field in the receiving station 1703, and the process proceeds to step 1511.

If the decision result in the step 1531 is NO, the process proceeds to a step 1532, where the start address is replaced with the value of the substitute address field 1702 in the transmitting station. The processing in this step is the same as the processing in step 1507 in FIG. Then, encapsulation is performed for the SGW (step 1508 (same as in FIG. 5)), and the process proceeds to step 1511.

As described above, in the RGW 10 of the present embodiment, when the packet transmitted from the PC 60 is a packet belonging to the lightweight and interactive protocol, the source address is not the address in the satellite transmitting station network, but the address of the satellite receiving station. The packet is replaced with an address in the network to which it belongs and sent to the Internet
Server 5 without going through W and therefore without using a one-way route.
It is exchanged with 0.

According to the present embodiment, a system for performing asymmetric routing using a one-way path having a high speed but a large delay using RGWs and SGWs in a network using the Internet protocol. When using a private IP address, RGW
However, by controlling the packet of the lightweight and interactive protocol so that it does not pass through the one-way path with a large delay, the speed of the one-way path can be used in the non-interactive processing, and the delay of the one-way path can be reduced in the interactive processing. A system that can avoid the influence of size can be realized. In addition, the judgment processing of the upper layer protocol is performed by RGW
As described above, in a system having a plurality of RGWs, S
The determination process is dispersed compared to the case where the determination is performed on the GW,
It has the characteristic that the load required for the judgment is small.

Next, a description will be given of an embodiment of the present invention in which a route is changed according to a protocol type in the SGW instead of the RGW.

The system configuration of this embodiment is the same as that of FIG. 1, the hardware configuration of the RGW is the same as that of FIG.
The contents of the GW processing program are the same as those in FIG. Also,
The hardware configuration of the SGW is also the same as in FIG.

SG describing operation of SGW in this embodiment
FIG. 14 shows a flowchart of the W processing program. In this flowchart, steps 2509 and 251 are performed.
The point that Step 2521 is added during 0 is different from the flowchart of FIG. 7, and the processing of the other parts is the same as that of the flowchart of FIG.

As shown in FIG. 14, in the SGW processing program of this embodiment, after it is determined in step 2509 that the end point address is within the range of the receiving station address, step 2509 is executed.
At 521, it is determined whether or not the upper layer protocol of the packet is a lightweight / interactive protocol. If YES, the process proceeds to step 2512 to encapsulate the packet toward the RGW, and NO
In the case of, the process proceeds to step 2510, and the packet is directly transmitted to the one-way route. Note that the upper-layer protocol determination procedure in step 2521 is the same as step 1521 in FIG.

By operating the SGW in this manner, the packet of the lightweight and interactive protocol does not pass through a one-way path, but is transmitted between the SGW and the RGW after being encapsulated in both directions.

According to the present embodiment, a system for performing asymmetrical routing using a one-way route having a high speed but a large delay using RGW and SGW in a network using the Internet protocol. By controlling the packet to not pass through a one-way route with a large delay, the speed of the one-way route can be used in non-interactive processing, and the effect of the magnitude of the one-way route delay can be avoided in interactive processing. System can be realized. Further, since the determination process of the upper layer protocol is performed on the SGW, it is not necessary to prepare an additional global IP address on the satellite receiving station side even when a private IP address is used for the local network of the satellite receiving station. Has features.

Next, another embodiment in which the SGW changes the route according to the protocol type will be described. The system configuration of this embodiment is the same as that of FIG. 1, the hardware configuration of the RGW is the same as that of FIG. 2, and the content of the RGW processing program is also the same as that of FIG. Also, the hardware configuration of the SGW is the same as that of FIG.

SG describing operation of SGW in the present embodiment
FIG. 15 shows a flowchart of the W processing program. In this flowchart, steps 2509 and 251 are performed.
The point that step 2531 is added during 0 is different from the flowchart of FIG. 7, and the processing of the other parts is the same as the flowchart of FIG.

As shown in FIG. 15, in the SGW processing program of this embodiment, after it is determined in step 2509 that the end point address is within the range of the receiving station address, step 2509 is executed.
At 521, it is determined whether or not the size of the packet is equal to or smaller than a specified value. If the determination is YES, the process proceeds to step 2512 to encapsulate the packet toward the RGW.
Proceeding to 10, the packet is transmitted as it is to the one-way route.

By operating the SGW in this way, packets whose size is equal to or smaller than the specified value do not pass through the one-way route,
The transmission between the GW and the RGW is encapsulated in both directions.

In the present invention, means for estimating based on the packet size is used instead of using the information in the header to determine whether the upper layer protocol is lightweight and interactive.

In a lightweight / interactive application, since the importance of interactivity is given, it can be observed that data is transmitted in small-sized packets instead of being transmitted to some extent as a large packet. Therefore, it is expected that the response of a lightweight and interactive application will be improved as a result of not using a path with a large delay for a small packet such as 50 bytes or less.

By changing the route for each packet,
The order of arriving IP packets may differ from the order of transmission, but there is no particular problem since the IP protocol is originally a protocol that does not guarantee the order of arrival of packets.

According to the present embodiment, a system for performing asymmetric routing using a one-way route with high speed but large delay using RGW and SGW in a network using the Internet protocol. By controlling the packet to not pass through a one-way route with a large delay, the speed of the one-way route can be used in non-interactive processing, and the effect of one-way route delay can be avoided in interactive processing. The system can be realized.

Further, since the judgment processing of the upper layer protocol is not a judgment based on a predetermined port number but an indirect judgment based on a packet size, the judgment processing is changed even if a lightweight and interactive protocol is newly developed. There is no need to do this.

As described above, according to the present invention, in a communication system using an asymmetric route using a one-way route, whether or not to use a one-way route is switched according to the type of a higher-level protocol. Thus, a system can be realized in which the speed of a one-way path is utilized and the effect of the magnitude of the delay of the one-way path can be avoided in interactive processing.

[0130]

According to the present invention, in a network system constructed on the assumption that bidirectional communication of packets is performed using a bidirectional path, one-way transmission of packets can be performed without changing an existing routing protocol. A communication system using an asymmetric route that can realize asymmetric routing using a one-way route for communication can be constructed.

At this time, since asymmetric routing is performed based on information in the network layer, asymmetric routing transparent to the application layer can be realized without making any modifications to the application programs operating on the network system. This has the effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an asymmetric route utilization communication system according to an embodiment of the present invention.

FIG. 2 is a hardware configuration diagram of an RGW according to the embodiment of the present invention.

FIG. 3 is a hardware configuration diagram of an SGW according to the embodiment of the present invention.

FIG. 4 is a data configuration diagram of an address replacement management table in the embodiment of the present invention.

FIG. 5 is a flowchart of an RGW processing program according to the embodiment of the present invention.

FIG. 6 is a configuration diagram of a receiving station management table in the embodiment of the present invention.

FIG. 7 is a flowchart of an SGW processing program according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a flow of an IP packet in the embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a flow of an IP packet in the embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a flow of an IP packet in the embodiment of the present invention.

FIG. 11 is a flowchart of an RGW processing program according to another embodiment.

FIG. 12 is a flowchart of an RGW processing program according to another embodiment.

FIG. 13 is a data configuration diagram of an address replacement management table in another embodiment.

FIG. 14 is a flowchart of an SGW processing program according to another embodiment.

FIG. 15 is a flowchart of an SGW processing program according to another embodiment.

FIG. 16 is a diagram showing a TCP packet format in another embodiment.

FIG. 17 is a data configuration diagram of a port number registration table in another embodiment.

[Explanation of symbols]

10: receiving side gateway (RGW), 11: satellite receiver (IRD), 20: transmitting side gateway (SGW),
21: Uplink station, 30: Communication satellite, 4
0: Internet network, 50: Server, 60: Personal computer (PC), 1001: CPU, 1002
... Memory, 1003 ... Disk controller, 1004
... Console controller, 1005 ... Network controller, 1006 ... Network controller, 1
007: IRD controller, 1100: Hard disk, 1200: Console, 1700: Address replacement management table, 2001: CPU, 2002: Memory, 2
003: disk controller, 2004: console controller, 2005: network controller,
2006: network controller, 2100: hard disk, 2200: console, 2700: receiving station management table.

Claims (8)

[Claims] 1. A network system constructed on the premise of performing bidirectional communication of packets using a bidirectional path, a one-way path for performing one-way communication of packets, and transmission of the one-way path. A transmission gateway provided at the side site and connected to the network system; and a reception system provided at the reception site on the one-way path and connected to a local system different from the network system and the network system. And a receiving gateway, wherein the receiving gateway sets a starting address of a packet transmitted from the local system to an alternative address previously allocated in the network system to the transmitting site of the one-way path. After the replacement, the packet after the address replacement is First address replacement means for transmitting the packet to the local system, if the destination address of the packet transmitted from the one-way path is the substitute address, the substitute address is connected to the local system. Second address replacement means for transmitting the address-replaced packet to the local system after replacing the address with the address of the communication device, wherein the transmission-side gateway is configured to transmit the packet transmitted from the network system. When the destination address is the alternative address, the packet is transmitted on the one-way route, and when the destination address is not the alternative address, the packet is transmitted on the network system. An asymmetric route communication system. 2. The communication system using an asymmetric route according to claim 1, wherein the first address replacement means of the receiving gateway encapsulates the packet after the address replacement, and then converts the encapsulated packet into the packet. When the packet transmitted from the network system is an encapsulated packet, the packet is transmitted to the transmission gateway via the network system, and the routing means of the transmission gateway routes the packet extracted from the capsule. A communication system using an asymmetric route. 3. The communication system using an asymmetric route according to claim 1, wherein the receiving-side gateway detects whether or not the one-way route is communicable, and determines a detection result as the network system. Communication means for notifying the transmission-side gateway of the transmission-side gateway, and storage means for storing the detection result notified from the reception-side gateway, and routing means of the transmission-side gateway. When the one-way route cannot communicate, the destination address of the packet to be transmitted on the one-way route is replaced with the alternative address, and the packet after the address replacement is transmitted via the network system. A communication system using an asymmetric route, wherein the communication is transmitted to the receiving side gateway. 4. A network system constructed on the assumption that bidirectional communication of packets is performed using a bidirectional path at a receiving site and a transmitting site of a one-way path for performing one-way communication of packets. A communication device connected to a local system different from the network system, wherein the receiving gateway provided at the receiving site on the one-way path is connected to the local system. A communication method for performing communication between a first type communication device connected to the network system and a second type communication device connected to the network system, wherein the communication method is provided at the transmission side site of the one-way path. The transmitted gateway transmits the packet transmitted from the second type of communication device to the first type of communication device through the one-way path. And by sending to the receiving gateway, the receiving gateway, the packet transmitted through the one-way path from the transmitting gateway,
Transmitting the packet to the first type of communication device, the receiving side gateway transmits a packet transmitted from the first type of communication device to the second type of communication device,
The transmission-side gateway transmits the packet transmitted through the network system to the transmission-side gateway via the network system, and the reception-side gateway transmits the packet transmitted through the network system to the second-type communication device. Communication method using an asymmetric route. 5. A network system which performs transmission and reception of packets between communication devices as basic communication processing, and performs routing on the premise that a route between routers for distributing packets is capable of bidirectional communication. A one-way route for communicating packets in one direction, a sending gateway provided at the sending site of the one-way route and connected to the network system, and a sending gateway provided at the receiving site of the one-way route. A network system having an asymmetric route, comprising the network system, and a receiving gateway connected to a local system different from the network system, wherein the receiving gateway has been transmitted from the local system. Packet
If the protocol information included in the header of the packet satisfies a certain condition, the packet is transmitted as it is on the network system. First address replacing means for replacing the address with a transmitting station-side alternative address previously assigned in the network system, and then transmitting the packet after the address replacement on the network system; If the destination address of the received packet is the above-mentioned substitute address of the transmitting station, the substitute address of the transmitting station is replaced with the address of the communication device connected to the local system. Second address replacement means for transmitting a packet to the local system. The transmitting side gateway transmits the packet on the one-way path when the destination address of the packet transmitted from the network system is the transmitting station side alternative address, and when the destination address is not the substitute address, And a routing means for transmitting the packet on the network system. 6. The communication system using an asymmetric route according to claim 5, wherein the receiving side gateway transmits a packet transmitted from the local system.
If the protocol information included in the header of the packet satisfies a certain condition, the source address is replaced with a receiving station side alternative address pre-assigned in the network system to the receiving site of the one-way path,
If the packet does not satisfy the above condition, first address replacement means for replacing the source address with a substitute address on the transmitting station side and then transmitting the packet after the address replacement on the network system; If the destination address of the packet transmitted from the above is the receiving station side substitute address or the transmitting station side substitute address, the receiving station side substitute address or the transmitting station side substitute address is connected to the local system. With the address of the communication device
Second address replacing means for transmitting the address-replaced packet to the local system, wherein the transmitting-side gateway is configured such that the destination address of the packet transmitted from the network system is the transmitting station-side alternative address. Wherein the routing means transmits the packet on the one-way path, and if the packet is not the alternative address, transmits the packet on the network system. 7. The communication system using an asymmetric route according to claim 5, wherein the receiving side gateway replaces a starting point address of a packet transmitted from the local system with a transmitting station side alternative address, and after address replacement. First address replacing means for encapsulating the packet of the above, and transmitting the encapsulated packet to the transmitting gateway via the network system, and the destination address of the packet transmitted from the one-way path is transmitted to In the case of the station side substitute address, the transmitting station side substitute address is replaced with the address of the communication device connected to the local system, and then the packet after the address replacement is transmitted to the local system. Address replacement means, and a password transmitted from the network system. When the packet is an encapsulated packet, the transmitting gateway includes a routing unit that performs routing for the packet taken out of the capsule, and the transmission-side gateway determines that the destination address of the packet transmitted from the network system is the transmission station. In the case of the side alternative address, if the protocol information included in the header of the packet satisfies a certain condition, the packet is encapsulated and transmitted to the receiving gateway via the network system, and the condition is not satisfied. If the packet is not the alternative address, the packet is transmitted to the network system. If the packet is an encapsulated packet, the packet is re-routed. Do lute Asymmetric route based communication system characterized by having a ring means. 8. The communication system using an asymmetric route according to claim 5, wherein said receiving gateway replaces a starting point address of a packet transmitted from said local system with an alternative address of a transmitting station, and after address replacement. First address replacing means for encapsulating the packet of the above, and transmitting the encapsulated packet to the transmitting gateway via the network system, and the destination address of the packet transmitted from the one-way path is transmitted to In the case of the station side substitute address, the transmitting station side substitute address is replaced with the address of the communication device connected to the local system, and then the packet after the address replacement is transmitted to the local system. Address replacement means, and a password transmitted from the network system. When the packet is an encapsulated packet, the transmitting gateway includes a routing unit that performs routing for the packet taken out of the capsule, and the transmission-side gateway determines that the destination address of the packet transmitted from the network system is the transmission station. If it is a side alternative address, if the size of the packet is less than or equal to a specified value, encapsulate the packet and send it to the receiving gateway via the network system. If the above condition is not satisfied, unidirectional Routing means for transmitting the packet on the route, if the packet is not the alternative address, transmitting the packet to the network system, and if the packet is an encapsulated packet, re-routing the packet extracted from the capsule Characterized by having Asymmetric route-based communication system that.