JP2014049807A - Communication packet processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication packet processing device that has a proxy DNS server function and can transmit a DNS query packet to a WAN side by automatically connecting a LAN and a WAN if the device received the DNS query packet from a LAN side terminal when it was not yet connected with the WAN.SOLUTION: A ship-mounted communication device 10 includes a router 20 and a satellite line controller 30. The router 20 comprises: a packet transmission/reception unit 21 for receiving a DNS query packet destined to the router 20 from a PC 3 at a LAN side; and a proxy DNS server unit 22 for substituting for an Inmarsat network DNS server 42 at a WAN side. The satellite line controller 30 comprises a line connection establishing unit 31 for establishing line connection between the LAN and the WAN on the condition that the satellite line controller receives the DNA query packet in a state in which the LAN and the WAN are not yet connected.

Description

  The present invention relates to a communication packet transmitted and received between a local area network (LAN) provided on the ship and a wide area network (WAN) provided outside the ship via a communication satellite. The present invention relates to a communication packet processing device that processes

  Generally, in a network environment such as the Internet, for example, a domain name represented as “example.co.jp” and a corresponding IP (Internet Protocol) address exist. If an Internet user wants to access a server whose domain name is "www.example.co.jp" using a client terminal, for example, the IP address associated with the domain name "www.example.co.jp" In order to obtain the information, a DNS query packet for inquiring a DNS (Domain Name System) server is transmitted from the client terminal.

  For example, in the ISDN (Integrated Services Digital Network), the DNS server information is configured to be registered in advance as described in the conventional technology column of Patent Document 1. With this configuration, when the ISDN communication control unit receives a DNS query packet including the IP address of the DNS server from the client terminal, it automatically connects to the Internet, and sends the DNS query packet to the DNS server. An IP address associated with the name can be acquired.

  By the way, a ship navigating in the open ocean generally includes an FBB (Fleet Broadband) device that communicates with a communication satellite, such as an Inmarsat (registered trademark) satellite, and is provided with an FBB service. Conventionally, an IP address of a DNS server on the Internet, which is a WAN side, is set for a client terminal in a ship on the LAN side. When a conventional FBB device receives a DNS query packet including the IP address of a DNS server from a client terminal when not connected to a communication satellite, it automatically connects to the Internet and responds to the DNS query packet in the same manner as the ISDN described above. It was supposed to get a packet.

  Here, the FBB service using a communication satellite generally employs a pay-as-you-go fee system per unit data. For this reason, it is desired to reduce the communication charge by reducing the number of transmissions of the DNS query packet for the DNS server on the WAN side. For this purpose, a proxy DNS server function that represents the DNS server on the WAN side is provided as an FBB device. Is preferably provided.

JP 2001-325176 A

  However, if the FBB device is provided with the proxy DNS server function, the client terminal on the LAN side transmits a DNS query packet to the FBB device when not connected to the communication satellite, and the IP from the LAN side to the WAN side Since no packet is generated, the FBB device cannot automatically connect to the WAN, and there is a problem that a response to the DNS query packet cannot be obtained from the WAN side.

  The present invention has been made in order to solve the conventional problems, and has a proxy DNS server function. Even when a DNS query packet is received from a LAN side terminal when not connected to the WAN, the LAN and WAN It is an object of the present invention to provide a communication packet processing apparatus that can automatically connect and send a DNS query packet to the WAN side.

  The communication packet processing device of the present invention is a communication packet processing device that processes communication packets transmitted and received between a local area network provided on the ship and a wide area network provided outside the ship via a communication satellite. Requesting name resolution of the server device using the name resolution request packet addressed to the own device requesting name resolution of the server device using the domain name of the server device on the wide area network side and the address of the server device A name resolution request packet receiving means for receiving one of the name resolution request packets addressed to the local device from an inboard device connected to the local area network, and the name resolution on the wide area network side Proxy server means for proxying the name resolution server for performing the Line connection establishment means for establishing a line connection between the local area network and the wide area network on the condition that the name resolution request packet has been received when the area network and the wide area network are not connected. And a configuration provided with.

  With this configuration, the communication packet processing apparatus of the present invention includes proxy server means for proxying the name resolution server and line connection establishment means for establishing line connection, and the line connection establishment means is configured so that the LAN and the WAN are not connected. In the state, a line connection between the LAN and the WAN can be established on the condition that a DNS query packet has been received.

  Therefore, the communication packet processing apparatus of the present invention has a proxy DNS server function, and automatically connects the LAN and the WAN even when the DNS query packet is received from the LAN side terminal when not connected to the WAN. DNS query packets can be sent to

  Further, in the communication packet processing device of the present invention, the proxy server means transmits, to the inboard device, a name resolution request response packet that responds to the name resolution request packet on condition that the name resolution is completed. On condition that name resolution could not be performed, after establishing the line connection, rewrite the address addressed to its own device included in the name resolution request packet to the address of the name resolution server and send it to the name resolution server, The name resolution request response packet acquired from the name resolution server is transmitted to the inboard device.

  With this configuration, in the communication packet processing apparatus of the present invention, the proxy server means receives a name resolution request response packet from the name resolution server on the WAN side if the proxy server means cannot resolve the name on its own device after establishing the line connection. Can be sent back to the inboard device.

  The present invention has a proxy DNS server function, and when a DNS query packet is received from a LAN side terminal when not connected to the WAN, the LAN and WAN are automatically connected to transmit the DNS query packet to the WAN side. Therefore, it is possible to provide a communication packet processing apparatus having an effect that it can be performed.

It is a block diagram which shows the structure of the packet communication system in one Embodiment of this invention. It is a flowchart which shows operation | movement of the packet communication system in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration will be described.

  As shown in FIG. 1, a packet communication system 1 in this embodiment includes an inboard communication network 2, a personal computer (hereinafter referred to as “PC”) 3 and a ship-mounted communication device 10 on the LAN side, and Inmarsat on the WAN side. A line 40, the Internet 4, and a WWW server 5. Here, the WWW server 5 constitutes a server device on the wide area network side according to the present invention. In FIG. 1, the gateway is not shown.

  The PC 3 and the ship-mounted communication device 10 are mounted on the ship and are connected by the ship communication network 2. Although a plurality of PCs can be connected to the inboard communication network 2, in the present embodiment, one PC 3 is connected to the inboard communication network 2.

  The PC 3 includes a web browser, and can acquire various contents included in, for example, the WWW server 5 connected to the Internet 4 so that the contents can be displayed on the screen and played back. For example, when the PC 3 wants to acquire the contents of the WWW server 5, the DNS query packet for requesting an IP address is transmitted to the router 20 using the domain name of the WWW server 5 as key information. The PC 3 constitutes an inboard device according to the present invention.

  The ship-mounted communication device 10 includes a router 20 that relays communication packets, a satellite line control device 30 that performs line control with the Inmarsat line 40 based on a predetermined communication protocol, and a communication line selection unit 11 that selects a communication line. And an external line control device 12 that performs line control on the external line. Although not shown, the ship-mounted communication device 10 is configured by a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is a program stored in advance in the ROM. Is supposed to work according to. The ship-mounted communication device 10 constitutes a communication packet processing device according to the present invention.

  The router 20 includes a packet transmitting / receiving unit 21 and a proxy DNS server unit 22, and relays communication packets.

  The packet transmitting / receiving unit 21 determines the destination and type of the communication packet received from the inboard communication network 2, the satellite line control device 30, and the external line control device 12, and transmits the packet to a predetermined destination based on the determination result. Yes. The packet transmitting / receiving unit 21 constitutes a name resolution request packet receiving unit according to the present invention.

  The proxy DNS server unit 22 acts as a proxy for an Inmarsat network DNS server 42 (described later) connected to the Inmarsat IP network 43 and a DNS server (not shown) connected to the Internet 4. That is, the proxy DNS server unit 22 stores information that associates a domain name with an IP address. When a DNS query packet is received, the proxy DNS server unit 22 obtains an IP address from the domain name or obtains a domain name from the IP address. You can do that.

  Specifically, the proxy DNS server unit 22 receives, from the PC 3 via the packet transmission / reception unit 21, for example, a DNS query packet addressed to the router 20 that requests an IP address inquiry using the domain name of the WWW server 5 as key information. In this case, name resolution is performed to respond to the IP address corresponding to the domain name, and the IP address information is returned to the PC 3.

  Here, the proxy DNS server unit 22 does not store the information of the IP address corresponding to the domain name (when name resolution is not possible), and after the line connection with the Inmarsat line 40, the DNS query The destination address of the packet is rewritten to the address of the Inmarsat network DNS server 42 and output to the packet transmitting / receiving unit 21. The proxy DNS server unit 22 constitutes proxy server means according to the present invention.

  The satellite line control device 30 includes a line connection establishment unit 31 that establishes a line connection with the Inmarsat line 40 based on a predetermined communication protocol when the connection with the Inmarsat line 40 is not connected.

  Specifically, the line connection establishment unit 31 receives a DNS query packet addressed to the own device when the router 20 is not connected, or the router 20 receives a communication packet including an IP address for the Internet 4. In this case, line connection with the INMARSAT line 40 is established based on a predetermined communication protocol. Then, after the line connection is established by the line connection establishing unit 31, the satellite line control device 30 performs line control with the Inmarsat line 40 based on a predetermined communication protocol. The line connection establishing unit 31 constitutes line connection establishing means according to the present invention.

  The communication line selection unit 11 selects a communication line according to a predetermined priority order based on, for example, communication speed, communication cost, communication quality, and the like. In this embodiment, it is assumed that the communication line selection unit 11 has selected the Inmarsat line 40.

  The external line control device 12 performs line control with an external line based on various communication protocols. Examples of the external line include a mobile phone line, a PHS (Personal Handy-phone System) line, and a wireless LAN (Local Area Network) line compliant with the IEEE 802.11 standard.

  The Inmarsat line 40 includes an Inmarsat satellite 41, an Inmarsat network DNS server 42, and an Inmarsat IP network 43. In FIG. 1, the Inmarsat network DNS server 42 is set to one for simplicity of explanation, but a plurality of Inmarsat network DNS servers 42 may be used.

  The Inmarsat satellite 41 is an FBB communication satellite, and can relay a radio signal between the ship-mounted communication device 10 mounted on a ship and a ground station (not shown) provided on land. It is like that.

  The Inmarsat network DNS server 42 is connected to the Inmarsat IP network 43 and has information in which a host name and an IP address are associated with each other for a predetermined domain. This Inmarsat network DNS server 42 constitutes a name resolution server according to the present invention.

  The Inmarsat IP network 43 is connected to the Inmarsat satellite 41 and the Internet 4 and relays IP packets transmitted and received between them.

  Next, the operation of the packet communication system 1 according to the present embodiment will be described with reference to the block diagram shown in FIG. 1 and the flowchart shown in FIG. In the following description, in a state where the connection between the ship-mounted communication device 10 and the INMARSAT line 40 is not connected, the user of the PC 3 as the LAN-side client terminal displays a web page including the content of the WWW server 5 An example will be described.

  When the user of the PC 3 operates the PC 3 to request the display of the web page of the WWW server 5, the PC 3 sends a DNS query packet for requesting an IP address query using the domain name of the WWW server 5 as key information. It transmits to address (step S11).

  The packet transmitting / receiving unit 21 of the router 20 receives the DNS query packet from the PC 3 (step S12).

  The packet transmitting / receiving unit 21 transmits the received DNS query packet to the proxy DNS server unit 22, and the proxy DNS server unit 22 receives the DNS query packet and performs name resolution for responding with an IP address corresponding to the domain name. It is determined whether or not it can be performed (step S13).

  In step S13, when the proxy DNS server unit 22 determines that name resolution is possible, that is, by referring to the correspondence table between the domain name and the IP address stored therein, the domain name included in the received DNS query packet If the IP address corresponding to the IP address can be retrieved, a packet including the IP address information (hereinafter referred to as “DNS query response packet”) is generated (step S19). The proxy DNS server unit 22 generates a DNS query response packet in the same manner even when the IP address corresponding to the corresponding domain name is stored in its own cache.

  On the other hand, if the proxy DNS server unit 22 does not determine that the name can be resolved in step S13, the proxy DNS server unit 22 outputs a line connection establishment instruction signal with the Inmarsat line 40 to the line connection establishment unit 31 of the satellite line control device 30. Then, the line connection establishment unit 31 establishes line connection according to a predetermined communication protocol (step S14). If it is determined that name resolution is not possible, the proxy DNS server unit 22 searches for an IP address corresponding to the domain name included in the DNS query packet received by referring to the correspondence table stored by itself. This is a case where the IP address corresponding to the corresponding domain name is not stored in its own cache.

  After the line connection with the Inmarsat line 40, the proxy DNS server unit 22 acquires the IP address of the Inmarsat network DNS server 42 from the Inmarsat satellite 41 (step S15).

  The proxy DNS server unit 22 rewrites the destination of the DNS query packet to the IP address of the Inmarsat network DNS server 42 (step S16), and outputs it to the satellite channel control device 30 via the packet transmitting / receiving unit 21.

  The satellite line control device 30 transmits a DNS query packet to the Inmarsat network DNS server 42 (step S17).

  The Inmarsat network DNS server 42 receives the DNS query packet through the Inmarsat satellite 41 and the Inmarsat IP network 43 to perform name resolution (step S18), and generates a DNS query response packet in step S19. The generated DNS query response packet is transmitted to the proxy DNS server unit 22. If name resolution cannot be performed by the Inmarsat network DNS server 42, name resolution is performed by another DNS server (not shown) connected to the Inmarsat IP network 43 or a DNS server (not shown) connected to the Internet 4. Is planned.

  The proxy DNS server unit 22 stores the IP address corresponding to the domain name included in the DNS query response packet in its own cache, and transmits the DNS query response packet to the PC 3 (step S20). As a result, the PC 3 can acquire the IP address of the WWW server 5, acquires various contents by accessing the WWW server 5, and displays the web page of the WWW server 5 on the screen (step S21).

  As described above, the ship-mounted communication device 10 in the present embodiment includes the proxy DNS server unit 22 that acts as a proxy for the name resolution server and the line connection establishment unit 31 that establishes line connection. The line connection between the LAN and the WAN can be established on the condition that the DNS query packet is received in a state where the LAN and the WAN are not connected.

  Therefore, the ship-mounted communication device 10 according to the present embodiment has a proxy DNS server function, and automatically connects the LAN and the WAN even when the DNS query packet is received from the LAN side terminal when not connected to the WAN. A DNS query packet can be transmitted to the WAN side.

  As described above, the communication packet processing apparatus according to the present invention has a proxy DNS server function and automatically connects a LAN and a WAN even when a DNS query packet is received from a LAN side terminal when not connected to the WAN. The DNS query packet can be transmitted to the WAN side, and the communication packet transmitted / received between the LAN provided on the ship and the WAN provided outside the ship is processed via the communication satellite. It is useful as a communication packet processing device.

1 Packet Communication System 2 Inboard Communication Network 3 PC (Inboard Device)
4 Internet 5 WWW server (server device on the wide area network side)
10 Shipboard communication device (communication packet processing device)
DESCRIPTION OF SYMBOLS 11 Communication line selection part 12 External line control apparatus 20 Router 21 Packet transmission / reception part (Name resolution request packet receiving means)
22 Proxy DNS server part (proxy server means)
30 Satellite link control device 31 Line connection establishment unit (line connection establishment means)
40 Inmarsat line 41 Inmarsat satellite (communication satellite)
42 Inmarsat Network DNS Server (Name Resolution Server)
43 Inmarsat IP network

Claims (2)

A communication packet processing device that processes communication packets transmitted and received between a local area network provided onboard and a wide area network provided outside the ship via a communication satellite,
The name resolution request packet addressed to its own device that requests name resolution of the server device using the domain name of the server device on the wide area network side and the server device that requests name resolution using the address of the server device. Name resolution request packet receiving means for receiving one of the name resolution request packets addressed to the device from the inboard device connected to the local area network;
Proxy server means for proxying a name resolution server that performs the name resolution on the wide area network side;
Line connection for establishing a line connection between the local area network and the wide area network on condition that the name resolution request packet is received in a state where the local area network and the wide area network are not connected. Establishing means;
A communication packet processing device comprising: The proxy server means includes
Sending a name resolution request response packet in response to the name resolution request packet to the inboard device on condition that the name resolution has been completed,
After the establishment of the line connection on the condition that the name resolution could not be performed, the address addressed to the device included in the name resolution request packet is rewritten to the address of the name resolution server and sent to the name resolution server, The communication packet processing device according to claim 1, wherein the name resolution request response packet acquired from the name resolution server is transmitted to the inboard device.

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