JP2018174409A - Relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make communication from a communication terminal on one network possible in a short time in a case where an IP address given to the own device by a DHCP server on the other network cannot be acquired, in a relay device that relays communication between different networks.SOLUTION: A relay device comprises: a first interface unit connected with a DHCP server on a first network; a second interface unit connected with a communication terminal on a second network; an address acquisition unit that acquires a first IP address and a DNS address from the DHCP server; a DHCP function unit that assigns a second IP address every predetermined time in response to a request of the communication terminal; a determination unit that determines whether or not the address acquisition unit acquires the DNS address from the DHCP server; and a communication controller that sets the predetermined time to a second time when the determination unit has determined that the DNS address is acquired, and sets the predetermined time to a third time when the determination unit has determined that no DNS address is acquired, and notifies the communication terminal.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a relay device that relays communication in a wired network and a wireless network.

  In general, in order to connect a large-scale network such as the Internet configured with a global IP address or a relatively large intranet to a small-scale network configured with a private IP address or the like, the subnet is different. For this purpose, a relay device such as a router is used.

  The relay apparatus allocates a private IP address to a small network constructed under its own, and manages the small network.

  Here, when a client terminal belonging to this small network accesses a specific host terminal belonging to a large network, a large-scale IP packet using a private IP address is configured with a global IP address or the like. Since it cannot be transmitted directly to the network, the client terminal connects to the host terminal using a global IP address or the like possessed by a router that manages a small network instead of its own private IP address.

  In order to enable such a connection from a plurality of client terminals belonging to a small network constructed under a router, network address translation techniques such as NAPT (Network Address and Port Translation) and IP masquerade may be used. It is known (see Patent Document 1).

If these technologies are used, a relay apparatus having a global IP address or the like can proxy access from a plurality of client terminals having a private IP address to a host terminal having a global IP address or the like. The relay device enables access to a host terminal having a global IP address or the like from a plurality of client terminals by separately assigning and managing port numbers corresponding to connection requests by IP addresses for each client.

  In addition, a DHCP (Dynamic Host Configuration Protocol) server that dynamically allocates and uses IP addresses prepared in advance is provided on the network, and the number of client terminals increases, which saves the user from having to register and manage IP addresses. Mechanisms that can be mitigated are also widely known. The DHCP server also notifies a usage period (also referred to as a lease period) when an IP address dynamically assigned to a client terminal is assigned. Based on this notification, when about half of the lease period has elapsed, the client terminal makes an update request to the DHCP server to update the lease period. At this time, if there is an update in IP address or DNS address information in DHCP, the client terminal is given them.

  Recently, in various facilities (education, offices, etc.), a relay device (hereinafter referred to as an I / F) having a wired I / F and a wireless I / F in its own interface (hereinafter also referred to as I / F). Simply called a relay device).

  Here, the relay device is connected to a local area LAN that can be connected to an external network (for example, the Internet) via a wired network, and connected to a plurality of communication terminals for teachers and students in a classroom via a wireless network, Communication can be performed between the external network and the communication terminal. When performing such communication, the communication terminal, via the relay device, in addition to the above-mentioned IP address, DNS (necessary for name resolution given from the DHCP server installed on the local LAN) Domain Name System) address needs to be obtained.

JP 2003-198587 A JP 2003-198585 A

  Here, the relay apparatus operating with the IP masquerade function enabled must distribute the DNS address to a plurality of communication terminals for teachers and students connected via a wireless network (between the relay apparatus and the communication terminal). However, before the relay device acquires the DNS address from the DHCP server on the wired network (between the relay device and the local LAN), an IP address acquisition request (hereinafter also referred to as a DHCP request) is sent from the communication terminal of the wireless network to the relay device. If there is, the relay device cannot determine the DNS address and cannot notify the communication terminal. Therefore, even if the user who uses the communication terminal makes an IP address acquisition request to the relay device, the user cannot connect to the external network until the DNS address can be acquired from the relay device.

  Japanese Patent Application Laid-Open No. H10-228707 describes that the time during which communication cannot be performed is shortened by allowing the DHCP server to immediately change the communication setting from the DHCP server.

  However, in this case, it is necessary to provide a mechanism capable of changing and controlling the communication settings in both the DHCP server and the DHCP client terminal.

  In addition, by setting the lease period from the DHCP server to the DHCP client extremely short, it may be possible to shorten the time during which communication is not possible. However, the DHCP requests always flow on the network, increasing the network load. However, it is possible that a non-communication time may occur.

  The present invention has been made in order to solve a part of the above-described problems. When a communication terminal used by a user cannot obtain a DNS address from a relay device that relays to / from an external network or the like, The purpose is to shorten the time during which communication cannot be performed with a terminal that the user wants to connect to and to reduce the network load.

  A relay apparatus according to an aspect of the present invention is a relay apparatus that relays communication between a DHCP server on a first network and a communication terminal on a second network, and is connected to the DHCP server on the first network. A first interface unit that connects to a communication terminal on the second network, an address acquisition unit that acquires a first IP address and a DNS address from a DHCP server, and a predetermined time according to a request from the communication terminal A DHCP function unit that assigns a second IP address for each, a determination unit that determines whether the address acquisition unit has acquired a DNS address from a DHCP server, and a communication control unit that notifies a communication terminal of a predetermined time, When the DHCP function unit determines that the determination unit has acquired the DNS address, the DHCP function unit sets a predetermined time to the second time, If it is determined that not get DNS address, it sets the predetermined time in the third hour.

  According to this, in a situation where the relay device cannot communicate between the DHCP server and the relay device after the power is turned on, communication between the DHCP server and the relay device is performed while assigning an IP address to the communication terminal. If the relay device can acquire the IP address and DNS address of the own device, the user using the communication terminal can use the network to which the relay device is connected in a short time after the acquisition.

  Preferably, the third time is shorter than the second time.

  More preferably, in addition to the predetermined time, the communication control unit notifies the communication terminal of the second IP address and the DNS address when the determination unit determines that the DNS address has been acquired.

  The present invention provides a relay device that relays communication between different networks, when the IP address and DNS address assigned to the own device cannot be obtained from the DHCP server on one network, from the communication terminal on the other network. It is possible to communicate in a short time in response to the communication request.

FIG. 1 is an overall view of a communication system including a relay device according to an embodiment. FIG. 2 is a block diagram illustrating a hardware configuration of the relay device according to the embodiment. FIG. 3 is a block diagram illustrating a functional configuration of the relay apparatus according to the embodiment. FIG. 4 is a communication flow performed between the relay device and the communication terminal according to the embodiment. FIG. 5 is an overall communication sequence diagram of the communication system including the relay device according to the embodiment.

Hereinafter, embodiments will be specifically described with reference to the drawings.
Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment. In addition, the same code | symbol is attached | subjected to the same component and description may be abbreviate | omitted.

(Embodiment)
FIG. 1 is an overall view of a communication system 10 including a relay device 1 according to the present embodiment.

  As shown in FIG. 1, the communication system 10 includes a relay device 1, a communication terminal 2, a DHCP server 3, a DNS server 4, and an external network 5, which are connected by a LAN 1. In the present embodiment, LAN 1 is described as a wired network, but it may be a wireless network.

  The relay device 1 is a relay device that performs communication between the communication terminal 2 and a device (for example, the DHCP server 3) that exists on the LAN 1.

  The relay device 1 includes a wireless interface, establishes a communication link W1 with a communication terminal 2 or the like existing in a wireless communicable area, and wirelessly communicates with the communication terminal 2 and other communication terminals (not shown). Relay communication. Note that the wireless communication is realized by, for example, a wireless LAN (Local Area Network) conforming to the IEEE802.11a, b, g, and n standards.

  The relay apparatus 1 includes a wired interface, and transfers the communication frame toward the destination according to the destination of the communication frame (communication packet) used for wired communication. Note that the wired communication is realized by a wired LAN conforming to, for example, the IEEE 802.3 standard.

  The communication terminal 2 is a wireless communication terminal provided with a wireless interface. The communication terminal 2 performs wireless communication with the wireless interface of the relay device 1 via the communication link W1. The communication terminal 2 can communicate with other communication terminals and devices existing in the LAN 1 via the relay device 1.

  The DHCP server 3 is a device existing in the LAN 1 and can communicate with the relay device 1 through a wired LAN. The DHCP server 3 has a DHCP function inside.

  The DHCP server 3 receives an IP address assignment request from the relay device 1 and dynamically permits the use of an IP address from a plurality of IP addresses set in advance for a certain period (lease period) If there is no request for extension of IP address use permitted from the relay device 1 or an update request after the certain period has elapsed, the IP address permitted for use is released, and a request for IP address assignment from a new device is responded. It maintains a usable state as much as possible, and effectively utilizes a plurality of IP addresses preset in itself.

  The DNS server 4 includes information in which a domain name and an IP address are associated with each other, and has a function of performing name resolution. For example, in the present embodiment, when the communication terminal 2 accesses the domain existing on the external network 5, the communication terminal 2 sends the IP address associated with the domain via the relay device 1. It can be acquired from the DNS server 4 and connected to the domain.

  The LAN 1 is a communication network (local area network) connected to the relay device 1, the DHCP server 3, the DNS server 4, the external network 5, and the like.

  The external network 5 is an external communication network connected to the LAN 1. The communication network corresponds to, for example, an access network in a telecommunications carrier or the Internet.

FIG. 2 is a block diagram showing a hardware configuration of relay apparatus 1 according to the present embodiment.
As shown in FIG. 2, this apparatus includes a CPU (Central Processing Unit) 20, a ROM (Read Only Memory) 21, a RAM (Random Access Memory) 22, a storage device 23, a WNIC (Wireless Network Interface CardNW 24 IC) (Interface Card) 25, and an internal bus 26 for connecting each component.

  The CPU 20 is a processor that executes a control program stored in the ROM 21.

  The ROM 21 is a read-only storage area that holds a control program and the like.

  The RAM 22 is a storage area used as a work area used when the CPU 20 executes a control program.

  The storage device 23 is a storage area for storing control programs, control information, device information, or various information related to communication for temporary storage.

  The WNIC 24 includes a wireless communication interface that performs wireless communication. For example, a wireless LAN communication interface conforming to the IEEE802.11a, b, g, n, and ac standards.

  The NIC 25 includes a wired communication interface that performs wired communication. For example, a wired LAN communication interface conforming to the IEEE 802.3 standard or the like.

  The internal bus 26 is a bus that electrically connects the CPU 20, ROM 21, RAM 22, storage device 23, WNIC 24, and NIC 25 to exchange signals.

  FIG. 3 is a block diagram showing a functional configuration of relay apparatus 1 according to the present embodiment.

  As shown in FIG. 3, the relay device 1 includes a first interface unit 31, a second interface unit 32, an address acquisition unit 33, a determination unit 34, a DHCP function unit 35, and a communication control unit 36. Prepare.

  The first interface unit 31 performs wired communication with the DHCP server 3 existing on the LAN 1 by using a wired IP address (hereinafter also referred to as a first IP address) assigned from the DHCP server 3 to the relay device 1. I do. Here, LAN1 corresponds to the first network. The first interface unit 31 is realized by the CPU 20, the ROM 21, the RAM 22, the storage device 23 and the like (hereinafter also referred to as the CPU 20 and the like), and the NIC 25.

  The second interface unit 32 uses an IP address (hereinafter also referred to as a second IP address) assigned to each communication terminal such as the communication terminal 2 existing in the wireless communicable area from the DHCP function unit 35 of the relay device 1, using the communication terminal. 2 and wireless communication. Note that the second interface 32 unit has a wireless-side IP address set in its own device, and performs wireless communication with the communication terminal 2 via the communication link W1. Here, the communication link W1 corresponds to a second network. The second interface unit 32 is realized by the CPU 20 or the like and the WNIC 24.

  After the relay device 1 is powered on, the address acquisition unit 33 requests the DHCP server 3 to give its own wired IP address to the DHCP server 3 based on the initial settings relating to the stored network such as the storage device 23, and the DHCP server. 3 receives the response through the first interface.

  In addition, the address acquisition unit 33 receives the first IP address and the DHCP3 server from the DHCP server 3 for each lease period (hereinafter also referred to as a first time) preset in the DHCP server 3 via the first interface. The DNS address acquired from the DNS server 4 is acquired. Note that the first time (for example, 10 days) may be set by the administrator of the DHCP server 3 using a setting tool, or may be set in advance at the time of factory shipment. The address acquisition unit 33 is realized by the CPU 20 or the like.

  The determination unit 34 determines whether the address acquisition unit 33 has acquired a DNS address. When the address acquisition unit 33 has acquired the DNS address, the determination unit 34 notifies the DHCP function unit 35 of the DNS address. The acquired DNS address may be stored in a memory (for example, realized by the RAM 22, the storage device 23, etc.). On the other hand, when the address acquisition unit 33 has not acquired the DNS address, the determination unit 34 notifies the DHCP function unit 35 that the DNS address has not been acquired.

  Whether the determination unit 34 has received a request (DHCP Discover) or a DHCP request transmitted from the communication terminal 2 to the device having the DHCP function by broadcast communication from the communication terminal 2 via the second interface unit 32. It is determined whether or not, and the determination result is notified to the DHCP function unit 35. The determination unit 34 is realized by the CPU 20 or the like.

  The DHCP function unit 35 receives a notification indicating that a DHCP Discover or DHCP request has been received from the determination unit 34, and notifies the communication control unit 36 of the DNS address based on the notification of the address acquisition unit 33 together with the second IP address. .

  Further, the DHCP function unit 35 extends the lease period (also referred to as a predetermined period) of the second IP address in response to a request for extension of use of the second IP address or a request for renewal from the communication terminal 2. Here, the lease period of the second IP address differs depending on whether or not the DNS address has been acquired. The lease period when the DNS address is acquired is the second time (preset lease period), while the lease period when the DNS address is not acquired is set to a third time shorter than the second time.

Further, the DHCP function unit 35 performs the following notification to the communication control unit 36 based on the notification from the determination unit 34 in addition to the lease period of the second IP address described above.
(1) When the notification of the determination unit 34 is notified that the DNS address has not been acquired, the communication control unit 36 is notified of only the second IP address.
(2) The notification of the determination unit 34 notifies the communication control unit 36 of the second IP address and DNS address based on the acquisition of the DNS address. The DHCP function unit 35 is realized by the CPU 20 or the like.

  Based on the notification of the DNS address from the determination unit 34, the communication control unit 36 notifies the communication terminal 2 of the second time (a preset lease period) together with the second IP address and the DNS address. On the other hand, based on the notification that the DNS address has not been acquired, the third time is notified to the communication terminal 2 together with the second IP address. Note that the second time (for example, two hours) may be set by the administrator of the relay apparatus 1 using a setting tool, or may be set in advance at the time of factory shipment. In addition, the third time (for example, 1 minute) may be set by the administrator of the relay device 1 using a setting tool, or may be set in advance at the time of factory shipment. The communication control unit 36 is realized by the CPU 20 or the like.

  Next, a communication flow performed between the relay device 1 and the communication terminal 2 according to the embodiment shown in FIG. 4 will be described.

  The processing shown in FIG. 4 is an operation from when the relay device 1 is turned on until a DHCP Discover or DHCP request is received from the communication terminal 2 and the lease period is notified to the communication terminal 2 along with the provision of the second IP address. Is shown.

  In step S <b> 401, the determination unit 34 determines whether a DHCP Discover or DHCP request has been received from the communication terminal 2 via the second interface unit 32 from the communication terminal 2. If the determination unit 34 determines that this has been received, the process proceeds to step S402 (Yes in step S401). On the other hand, if it is determined that it has not been received, step S401 is repeated every time the second time elapses (No in step S401).

  In step S402, the determination unit 34 determines whether the address acquisition unit 33 has acquired a DNS address. When the address acquisition unit 33 has acquired the DNS address, the determination unit 34 proceeds to step S404 (Yes in step S402). On the other hand, when the address acquisition unit 33 has not acquired the DNS address, the determination unit 34 proceeds to step S403 (No in step S402).

  In step S403, the DHCP function unit 35 receives the notification of the determination unit 34 in step S402 and notifies the communication control unit 36 of the second IP address. Then, the communication control unit 36 notifies the communication terminal 2 of the third time together with the second IP address. The third time is preferably shorter than the second time. This is because the relay device 1 notifies the DNS address to the communication terminal 2 as soon as possible after the DNS address is acquired together with the first IP address.

  In step S404, the DHCP function unit 35 receives the notification of the determination unit 34 in step S402, and notifies the communication control unit 36 of the second IP address and DNS address. Then, the communication control unit 36 notifies the communication terminal 2 of the second time together with the second IP address and the DNS address. Until the relay device 1 acquires the DNS address together with the first IP address, as a result of passing through step S403 from step S402, the communication terminal 2 tries to acquire the DNS address based on the third time. If it can be acquired, the lease period is returned to the preset second time, which is longer than the third time, in order to reduce the load on the network.

  The above-described series of processing in FIG. 4 is repeated until the relay device 1 is powered off or stopped due to a failure.

  The process shown in FIG. 5 shows the sequence process of the entire communication system 10 in the present embodiment. Hereinafter, in the communication system 10 according to the embodiment, after the relay apparatus 1 is turned on, the communication terminal 2 makes an IP address and DNS address acquisition request to the relay apparatus 1 and acquires the IP address and DNS address. Will be described in order along the steps shown in FIG. Here, the processing shown in FIG. 5 assumes that the relay apparatus 1 cannot acquire its own wired IP address from the DHCP server 3 immediately after the power is turned on. That is, this situation is a situation where communication between the DHCP server 3 and the relay device 1 is not possible in the first network. For example, there may be various causes such as a physical failure such as a cable not being connected between the DHCP server 3 and the relay device 1, a problem in the network settings, and inability to communicate.

  In step S501, the communication terminal 2 notifies the relay device 1 of DHCP Discover, and waits for a response from the device having the DHCP function.

  In step S502, the relay apparatus 1 notifies the communication terminal 2 of a response because the own apparatus has the DHCP function (step S502).

  The communication terminal 2 that has received the response in step S502 notifies the relay apparatus 1 of a DHCP request in order to obtain an IP address (second IP address) (step S503).

  Here, since the relay device 1 has not yet been given the first IP address from the DHCP server 3 (situation (A)), the relay device 1 notifies the communication terminal 2 of the second IP address and the third time (for example, one minute). (Step S504).

  Thereafter, when the communication terminal 2 reaches the relay device 1 at a time when half of the third time has elapsed (for example, 30 seconds have elapsed), the communication terminal 2 extends or updates the use period of the second IP address, and the relay device 1 receives the information from the DHCP server 3. Check if the IP address is assigned. Therefore, the communication terminal 2 notifies the relay apparatus 1 of a DHCP request and receives a response notification until the relay apparatus 1 is given an IP address from the DHCP server 3 (steps S505 to S509).

  On the other hand, in step S521, the relay device 1 notifies the DHCP server 3 of the DHCP request, and in step S522, the relay device 1 responds to step S521 with the first IP address and DNS of its own device given from the DHCP server 3. Suppose you have an address. In this case, the relay apparatus 1 changes the lease period from the third time to the second time, and notifies the second IP address, DNS address, and second time (for example, two hours) as a response to the DHCP request of the communication terminal 2. (Step S510).

  Thereafter, the communication terminal 2 extends or updates the use period of the second IP address to the relay device 1 when a time (for example, 1 hour) after half of the second time has passed (steps S511 and S512).

  In this way, the communication terminal 2 in the embodiment extends the IP address through the second network while the IP address is not given to the relay device 1 from the DHCP server 3 on the first network of the relay device 1. Alternatively, by making an update request to the relay device 1, the communication terminal 2 can acquire a DNS address in a short time (at least half of the third time) if the relay device 1 acquires an IP address from the DHCP server 3. .

(Summary)
As described above, the relay apparatus according to the embodiment of the present invention receives the DHCP request from the communication terminal while the IP address and DNS address of the own apparatus cannot be obtained from the DHCP server on the connected network. If there is a communication terminal under the control of the device, the relay device notifies the assignment of an IP address that can be used by the communication terminal and resets the lease period (initial lease period) preset in the relay device to be shortened. After the IP address and DNS address of the own apparatus can be acquired from the DHCP server, the initial lease period is restored. In this way, communication between the DHCP server and the relay device can be performed while assigning an IP address to the communication terminal in a situation where communication between the DHCP server and the relay device cannot be performed after the relay device is turned on. If the relay device can acquire the IP address and DNS address of the own device, a user using the communication terminal can use a network (for example, the Internet) to which the relay device is connected in a short time after the acquisition. It becomes like this.

  In the present invention, the communication terminal may be an existing communication terminal having a function of requesting an IP address from the DHCP server, and can be realized only by improving the relay device.

  The present invention is useful when a communication terminal is connected under its own device in a situation where the IP address and DNS address cannot be obtained from the DHCP server at the time of startup such as after the power is turned on.

1 Relay device 2 Communication terminal 3 DHCP server 4 DNS server 5 External network (Internet etc.)
LAN1 Local area network 10 Communication system 20 CPU
21 ROM
22 RAM
23 storage device 24 WNIC
25 NIC
26 Internal Bus 31 First Interface Unit 32 Second Interface Unit 33 Address Acquisition Unit 34 Judgment Unit 35 DHCP Function Unit 36 Communication Control Unit

Claims (3)

A relay device that relays communication between a DHCP server on a first network and a communication terminal on a second network,
A first interface unit connected to the DHCP server on the first network;
A second interface unit connected to the communication terminal on the second network;
An address acquisition unit for acquiring a first IP address and a DNS address from the DHCP server;
A DHCP function unit that assigns a second IP address at predetermined intervals in response to a request from the communication terminal;
A determination unit that determines whether the address acquisition unit has acquired a DNS address from the DHCP server;
A communication control unit for notifying the communication terminal of the predetermined time,
The DHCP function unit sets the predetermined time to the second time when the determination unit determines that the DNS address has been acquired, and sets the predetermined time when the determination unit determines that the DNS address has not been acquired. Set the time to 3rd time,
Relay device.
The relay device according to claim 1, wherein the third time is shorter than the second time.
The communication control unit according to claim 1 or 2, wherein, in addition to the predetermined time, when the determination unit determines that the DNS address has been acquired, the communication control unit notifies the communication terminal of the second IP address and DNS address. Relay device.