Communication control device and communication control method

Abstract

This communication control device for controlling a plurality of communication devices that perform communication with each other using a communication protocol having a hierarchical structure comprises: a detection unit that detects the start of path switching of the communication; and an update control unit that updates, when the start of the path switching is detected, a correspondence table that is for use in the communication devices to be subjected to the path switching and in which an upper-layer protocol and a lower-layer protocol are associated with each other.

Description

Communication control device and communication control method

[0001] The present invention relates to a communication control device and a communication control method.

[0002] In many communications, communication protocols (hereinafter simply referred to as "protocols") have a hierarchical structure. Therefore, a communication device converts the address of a higher-level protocol into the address of a lower-level protocol using, for example, a predetermined correspondence table, and communicates using the lower-level protocol. When a communication path is switched, if the address of the lower-level protocol is changed but the higher-level protocol is retained, it is necessary to update the correspondence table held by each communication device. The correspondence table here refers to a table in which the higher-level protocol and the lower-level protocol are associated with each other.

[0003] For example, Patent Document 1 describes a technology for controlling the updating of a layer 2 address cache that a communication device references when forwarding a layer 3 packet to an opposing device. The layer 2 address cache is a correspondence table that associates layer 3 addresses with layer 2 addresses.

[0004] JP 2012-175578 A

[0005] However, when a communication path is switched, there may be a case where a communication device is not notified of the switch. In such a case, the communication device attempts communication using an old correspondence table, which may result in communication being impossible or it may take a long time to detect an error. The technology described in Patent Document 1 is a technology aimed at preventing unnecessary update operations of the Layer 2 address cache, and it is difficult to prevent communication problems caused by the above-mentioned communication path switching.

[0006] Recently, in order to realize low-latency and low-power-consumption communications, APN (All Photonics Network) has been studied, which minimizes photoelectric conversion processing in the communication network and processes all communications between terminals using optical signals. For example, in a communication network such as APN, high-speed optical path switching is performed. However, there is a problem that the above-mentioned communication failures are more likely to occur, especially when such communication path switching is performed at high speed.

[0007] In view of the above circumstances, an object of the present invention is to provide a technique that enables faster switching of communication paths.

[0008] One aspect of the present invention is a communication control device that controls multiple communication devices that communicate with each other using a communication protocol having a hierarchical structure, and is equipped with a detection unit that detects the start of a route switch for the communication, and an update control unit that, when the start of the route switch is detected, updates a correspondence table used in the communication device that is the target of the route switch, in which upper protocols and lower protocols are associated.

[0009] Another aspect of the present invention is a communication control device that controls multiple communication devices that communicate with each other using a communication protocol having a hierarchical structure, and includes: a detection unit that detects the start of a route switch for the communication; and an erasure control unit that, when the start of the route switch is detected, erases information contained in a correspondence table used in the communication device that is the target of the route switch, in which upper protocols and lower protocols are associated with each other.

[0010] Another aspect of the present invention is a communication control method by a computer that controls multiple communication devices that communicate with each other using a communication protocol having a hierarchical structure, the communication control method including: a detection step that detects the start of a route switch for the communication; and an update control step that, when the start of the route switch is detected, updates a correspondence table used in the communication device that is the target of the route switch, in which upper protocols and lower protocols are associated with each other.

[0011] Another aspect of the present invention is a communication control method by a computer that controls multiple communication devices that communicate with each other using a communication protocol having a hierarchical structure, the communication control method having a detection step of detecting the start of a route switch for the communication, and an erasure control step of erasing information contained in a correspondence table used in the communication device that is the target of the route switch, when the start of the route switch is detected, in which a higher-level protocol and a lower-level protocol are associated with each other.

[0012] The present invention makes it possible to provide a technique that enables faster switching of communication paths.

[0013] FIG. 1 is a diagram showing an example of a processing sequence for generating / updating a layer 2 address cache using the conventional ARP / NDP protocol. FIG. 2 is an example of a configuration diagram of a conventional network device 100. FIG. 3 is an example of a flowchart of a conventional layer 2 address cache update control method. FIG. 4 is an overall configuration diagram of a communication system 1 in a first embodiment of the present invention. FIG. 5 is a diagram showing an example of communication control by a control device 30 in the first embodiment of the present invention. FIG. 6 is a sequence diagram showing the operation of the communication system 1 in the first embodiment of the present invention. FIG. 7 is a diagram showing an example of connection destination information stored in a connection source communication device 10 in the first embodiment of the present invention. FIG. 8 is a diagram showing an example of connection destination information stored in a connection destination communication device 10 in the first embodiment of the present invention. FIG. 9 is a sequence diagram showing the operation of the communication system 1 in a second embodiment of the present invention.

[0014] A communication control device and a communication control method according to an embodiment of the present invention will be described in detail below with reference to the drawings. For ease of understanding, an example of a process for creating and updating a Layer 2 address cache using a conventional ARP (Address Resolution Protocol) / NDP (Neighbor Discovery Protocol) will be described first for comparison.

[0015] 1 shows an example of a processing sequence for creating and updating a Layer 2 address cache using the conventional ARP / NDP protocol, where network devices (such as user terminals, home routers, or network operator devices) are connected via Layer 2 links of Ethernet (registered trademark).

[0016] When a network device (its own device) needs to forward (relay) an IPv4 (Internet Protocol version 4) unicast packet to a remote network device (remote device) without an ARP cache entry for that device, it sends an ARP request packet to the remote device and receives an ARP response packet from the remote device, thereby creating an ARP cache entry for the remote device (see Figure 1A).After that, it sends and receives similar ARP packets to and from the remote device at regular intervals, updating the ARP cache entry.

[0017] However, if an ARP response packet is not received from the other device within a certain period of time, the creation / update of the ARP cache entry for the other device will fail, and it will become impossible to forward IPv4 unicast packets to the other device (see Figure 1 (B)).

[0018] The above processing flow is also the same when an ND (Neighbor Discovery) cache entry is generated / updated using the NDP protocol when transferring an IPv6 (Internet Protocol version 6) unicast packet to a peer device.

[0019] FIG. 2 is a diagram showing an example of the configuration of a conventional network device 100. As shown in FIG.

[0020] The network device 100 is a router at the end of a layer 2 section, and has a layer 2 address cache, which is a layer 3 address-layer 2 address correspondence table that is referenced when transferring a layer 3 packet to a peer device.

[0021] Furthermore, the network device 100 includes a layer 2 address cache creation / update / deletion unit 130 , an interconnection topology determination unit 140 , and a layer 2 address cache update control unit 150 .

[0022] The Layer 2 address cache generation / update / deletion unit 130 generates / updates Layer 2 address cache entries for opposing devices using protocols such as ARP / NDP, and in parallel with this process, deletes old Layer 2 address cache entries as appropriate to prevent the number of entries in the Layer 2 address cache 131 from increasing.

[0023] The interconnection topology determination unit 140 determines the topology of interconnection with the opposing device. The interconnection topology includes a connection between user terminals, a connection between a user terminal and a home router, a connection between a user terminal and a network operator device, a connection between a home router and a network operator device, and a connection between network operator devices.

[0024] The layer 2 address cache update control unit 150 selects an update method for when the layer 2 address cache creation / update / deletion unit 130 updates a layer 2 address cache entry for a remote device, depending on the interconnection topology determined by the interconnection topology determination unit 140. Update methods include a method of updating according to a default setting or a preset update period / update retry timer, and a method of statically maintaining the address without periodically updating it.

[0025] FIG. 3 is an example of a flowchart of a conventional layer 2 address cache update control method.

[0026] First, a layer 2 address cache entry for a remote device is created / updated using the ARP / NDP protocol or the like (step S1), and at that time, the interconnection type with the remote device is determined (step S2), and then a method for updating the layer 2 address cache entry for the remote device is selected according to the determined interconnection type (step S3). Thereafter, the layer 2 address cache entry for the remote device is updated according to the selected update method (step S4).

[0027] As such, the layer 2 address cache generation / update process using the conventional ARP / NDP exemplified above is configured to prevent unnecessary layer 2 address cache update processes from occurring, but does not take into consideration preventing logical network inconsistencies that occur when switching communication paths at high speed.

[0028] Therefore, when the above-described conventional technology is applied to a communication network that requires high-speed switching of optical paths, such as an APN, it is conceivable that a logical network inconsistency will occur when switching optical paths. In this case, it is expected that the communication outage will continue until the logical network inconsistency is resolved (i.e., until the communication outage is detected and each communication device updates information about the connection destination).

[0029] Hereinafter, a description will be given of a communication control device and a communication control method according to an embodiment of the present invention, which can prevent the occurrence of the above-mentioned communication interruption state even when optical paths are switched at high speed.

[0030] First Embodiment A first embodiment of the present invention will be described below.

[0031] [Overall Configuration of Communication System] The overall configuration of the communication system will be described below. Fig. 4 is an overall configuration diagram of a communication system 1 in a first embodiment of the present invention. As shown in Fig. 4, the communication system 1 is configured to include communication devices 10-1 to 10-3, an optical path switching device 20, and a control device 30. In the following description, when it is not necessary to distinguish between the communication devices 10-1 to 10-3, they may be simply referred to as "communication devices 10."

[0032] For ease of explanation, the communication system 1 of this embodiment has been described as including only three communication devices 10, but may include four or more communication devices 10. In practice, it is expected that more communication devices 10 will be used. Similarly, the communication system 1 of this embodiment has been described as including only one optical route switching device 20, but may include two or more communication devices 10.

[0033] The communication device 10-1 is a device that performs optical communication with either the communication device 10-2 or 10-3 via the optical path switching device 20. The communication devices 10-2 and 10-3 are also devices that perform optical communication with the communication device 10-1 via the optical path switching device 20. Each of the communication devices 10 stores destination information that is information about other communication devices 10 with which the communication device 10 is connected for communication.

[0034] The optical path switching device 20 is a device that is connected to a plurality of communication devices 10 and relays optical communications between the communication devices 10. The optical path switching device 20 can switch the optical path X connecting the communication devices 10-1 and 10-2 to the optical path Y connecting the communication devices 10-1 and 10-3, or conversely, switch the optical path Y connecting the communication devices 10-1 and 10-3 to the optical path X connecting the communication devices 10-1 and 10-2. The optical path switching device 20 is, for example, an optical switch.

[0035] The control device 30 is a device that controls the operations of the communication devices 10 and the optical path switching device 20. The control device 30 rewrites the connection destination information stored in each of the communication devices 10 as needed. The control device 30 also causes the optical path switching device 20 to switch the optical path as needed. The control device 30 is an example of a communication control device of the present invention.

[0036] 5 is a diagram showing an example of communication control by the control device 30 in the first embodiment of the present invention. For example, the communication devices 10-2 and 10-3 are web servers, and the communication device 10-1 is a terminal device that acquires information from the web server. However, the present invention is not limited to the case where communication is performed between such a web server and a terminal device.

[0037] For example, assume that the control device 30 controls the optical path switching device 20 to configure an optical path X. In this case, the communication devices 10-1 and 10-2 are communicatively connected as shown in Fig. 5. Here, when the control device 30 switches from the optical path X to the optical path Y, the connection destination of the communication device 10-1 is switched from the communication device 10-2 to the communication device 10-3.

[0038] If, during this optical path switching, a high-speed switch is executed so as not to cause a communication interruption in each of the communication devices 10, the connection destination of communication device 10-1 switches from communication device 10-2 to communication device 10-3 without changing the connection destination information stored in communication device 10-1, resulting in an inconsistency in the connection destination information. Specifically, because the connection destination information is generally updated after ARP learning or the like is performed, it takes a certain amount of time from the switching of the optical path until the connection destination information is updated. This results in a communication interruption.

[0039] Therefore, when switching the optical path, the control device 30 in this embodiment rewrites the connection destination information stored in each of the communication devices 10 to connection destination information that represents the state after the optical path is switched. This allows the control device 30 in this embodiment to switch the optical path without causing inconsistencies in the connection destination information, thereby shortening the time during which communication is interrupted.

[0040] [Operation of the Communication System] Hereinafter, a description will be given of an example of the operation during the optical path switching process of the communication system 1. Fig. 6 is a sequence diagram showing the operation of the communication system 1 in the first embodiment of the present invention.

[0041] First, the control device 30 transmits request signals requesting transmission of setting information to the communication device 10 (here, communication device 10-1) that is the connection source, the communication device 10 (here, communication device 10-3) that will be the connection destination after switching the optical path, and the optical path switching device 20. The control device 30 then receives response signals including the setting information from the communication devices 10-1, 10-3, and the optical path switching device 20, respectively, thereby collecting the setting information of these devices (steps S101 to S103).

[0042] The setting information here includes connection destination information stored in each communication device 10, setting information related to the optical path set by the optical path switching device 20, and the like.

[0043] Next, the control device 30 starts switching the optical path connection. The control device 30 transmits the connection destination information after the optical path switching to the communication device 10-1, which is the source communication device. Then, the control device 30 overwrites and updates the connection destination information currently stored in the communication device 10-1 with the transmitted connection destination information (step S104).

[0044] The communication device 10-1, which is the source communication device, overwrites and updates the connection destination information stored in itself with the received connection destination information under the control of the control device 30. When the communication device 10-1 has completed rewriting the connection destination information, it transmits a completion notification indicating completion to the control device 30 (step S105).

[0045] Next, upon receiving the completion notification transmitted from the communication device 10-1, the control device 30 transmits the connection destination information after the optical path switching to the communication device 10-3, which is the connection destination communication device. Then, the control device 30 overwrites and updates the connection destination information currently stored in the communication device 10-3 with the transmitted connection destination information (step S106).

[0046] The communication device 10-3, which is the destination communication device, overwrites and updates the destination information stored in itself with the received destination information under the control of the control device 30. When the communication device 10-3 has completed rewriting the destination information, it transmits a notification indicating the completion to the control device 30 (step S107).

[0047] Next, upon receiving the completion notification transmitted from the communication device 10-3, the control device 30 transmits instruction information to the optical path switching device 20 to instruct the optical path switching device 20 to execute optical path switching (step S108). The optical path switching device 20 receives the instruction information and executes optical path switching in accordance with the control of the control device 30. Upon completion of the optical path switching, the optical path switching device 20 transmits a completion notification to the control device 30 (step S109).

[0048] Next, the control device 30 completes the implementation of the optical path connection switching when it receives the completion notification transmitted from the optical path switching device 20. This completes the operation of the communication system 1 when switching the optical path shown in the sequence diagram of FIG.

[0049] [Configuration of connection destination information] An example of the configuration of connection destination information will be described below. Fig. 7 is a diagram showing an example of connection destination information stored in communication device 10-1, which is the connection source communication device in the sequence diagram of Fig. 6, for example. As shown in Fig. 7, the connection destination information stored in the connection source communication device is tabular data in which information relating to the items "connection destination IP address," "connection destination MAC address," and "own device interface" are associated with each other.

[0050] The IP address of the destination is, for example, the IP address of the communication device 10-3, which is the destination communication device in the sequence diagram of Fig. 6. The MAC (Media Access Control) address of the destination is, for example, the MAC address of the communication device 10-3, which is the destination communication device in the sequence diagram of Fig. 6. The host interface is, for example, the communication interface of the communication device 10-1 (i.e., the host device), which is the source communication device in the sequence diagram of Fig. 6.

[0051] 7, for example, before switching of the optical path, the communication device 10-1 is connected to the communication device 10-2, and therefore the IP address and MAC address of the communication device 10-2 are set in the connection destination information stored in the communication device 10-1, which is the connection source communication device. In addition, information indicating a specific communication interface of the device itself is also set as the transmission destination.

[0052] When switching the optical path, this connection destination information is rewritten (overwritten) by the control device 30, and the IP address and MAC address of the communication device 10-3 are set as the values ​​of the connection destination IP address item and the connection destination MAC address item. In addition, information indicating a specific communication interface of the communication device itself is also set as the destination.

[0053] 8 is a diagram showing an example of destination information stored in communication device 10-3, which is the destination communication device in the sequence diagram of FIG. 6. As shown in FIG. 8, the destination information stored in the source communication device is table-format data in which information relating to the items "destination IP address," "destination MAC address," and "own device interface" are associated with each other. In other words, the data format of the destination information stored in the source communication device is the same as the data format of the destination information stored in the destination communication device.

[0054] The IP address of the destination is, for example, the IP address of the communication device 10-1, which is the communication device that is the connection source in the sequence diagram of Fig. 6. The MAC address of the destination is, for example, the MAC address of the communication device 10-1, which is the communication device that is the connection source in the sequence diagram of Fig. 6. The interface of the own device is, for example, the communication interface of the communication device 10-3 (i.e., the own device), which is the communication device that is the connection destination in the sequence diagram of Fig. 6.

[0055] 8, for example, when switching the optical path, this connection destination information is rewritten (newly added or overwritten) by the control device 30, and the IP address and MAC address of the communication device 10-1 are set as the values ​​of the connection destination IP address item and the connection destination MAC address item. In addition, information indicating a specific communication interface of the communication device itself is also set as the destination.

[0056] In this example, the correspondence table is an ARP cache table. As described above, when the correspondence table is an ARP cache table, the upper protocol corresponds to an IP address, and the lower protocol corresponds to a MAC address (Ether).

[0057] The correspondence table may be, for example, a DNS resolver cache or a MAC address table. When the correspondence table is a DNS resolver cache, the upper protocol corresponds to HTTP, and the lower protocol corresponds to an IP address. When the correspondence table is a MAC address table, the upper protocol corresponds to a MAC address (Ether), and the lower protocol corresponds to a physical interface. In this way, the present invention can be applied to any protocol that has a hierarchical structure.

[0058] As described above, in the communication system 1 according to the first embodiment of the present invention, the control device 30 controls a plurality of communication devices 10 that communicate with each other using a hierarchical protocol, and the optical route switching device 20 that switches the optical route of the communication. When the control device 30 detects the start of a communication route switch, the control device 30 updates a correspondence table (connection destination information) used in the communication devices 10 that are the target of the route switch (i.e., the connection source communication device 10 and the connection destination communication device 10), in which upper protocols and lower protocols are associated, thereby changing the association between the upper protocols and lower protocols. The control device 30 then has a configuration that causes the optical route switching device 20 to perform the route switch.

[0059] By having such a configuration, the communication system 1 in the first embodiment of the present invention can quickly perform route switching and prevent communication interruptions, even when route switching is performed at high speed, because the correspondence table (connection destination information) is updated in advance to the correct information after route switching.

[0060] <Second Embodiment> A second embodiment of the present invention will be described below. In the communication system 1 in the first embodiment described above, the control device 30 is configured to rewrite the connection destination information stored in each of the communication devices 10 when switching the optical path. On the other hand, in a communication system in a second embodiment described below (hereinafter referred to as a "communication system 1a"), a control device (hereinafter referred to as a "control device 30a") is configured to erase the connection destination information stored in the source communication device 10 when switching the optical path. The control device 30a is an example of a communication control device of the present invention.

[0061] By deleting the connection destination information stored in the source communication device 10, relearning of the connection destination information (e.g., ARP learning) is initiated spontaneously. In conventional technology, relearning is typically initiated after a communication interruption is detected, which requires time before communication is again possible. In contrast, the control device 30a in the second embodiment erases the connection destination information stored in the source communication device 10 in accordance with the timing of switching the optical path, thereby starting relearning of the connection destination information earlier and shortening the time for communication interruption.

[0062] [Operation of the Communication System] An example of the operation of the communication system 1a during the optical path switching process will be described below. Fig. 9 is a sequence diagram showing the operation of the communication system 1a in the second embodiment of the present invention.

[0063] First, the control device 30a transmits request signals requesting transmission of setting information to the communication device 10 (here, communication device 10-1) that is the connection source, the communication device 10 (here, communication device 10-3) that will be the connection destination after switching the optical path, and the optical path switching device 20. The control device 30a then receives response signals including the setting information from the communication devices 10-1, 10-3, and the optical path switching device 20, respectively, thereby collecting the setting information of these devices (steps S201 to S203).

[0064] The setting information here includes connection destination information stored in each communication device 10, setting information related to the optical path set by the optical path switching device 20, and the like.

[0065] Next, the control device 30a starts switching the connection of the optical path. The control device 30a transmits instruction information to the optical path switching device 20 to instruct the optical path switching device 20 to execute the optical path switching (step S204). The optical path switching device 20 receives the instruction information and executes the optical path switching in accordance with the control of the control device 30a. When the optical path switching is completed, the optical path switching device 20 transmits a completion notification to the control device 30a (step S205).

[0066] Next, upon receiving the completion notification transmitted from the optical route switching device 20, the control device 30a transmits instruction information for deleting the connection destination information to the communication device 10-1, which is the source communication device (step S206). Upon receiving the instruction information transmitted from the control device 30a, the communication device 10-1, which is the source communication device, deletes the connection destination information stored therein in accordance with the control of the control device 30a. Upon completing the deletion of the connection destination information, the communication device 10-1 transmits a completion notification indicating completion to the control device 30a (step S207).

[0067] Furthermore, communication device 10-1, which is the source communication device, transmits a request signal requesting the transmission of connection information to communication device 10-3, which is the destination communication device (step S208). Note that the connection information here refers to information required for connection with communication device 10-3. Upon receiving the request signal transmitted from communication device 10-1, communication device 10-3 transmits a response signal including the connection information to communication device 10-1 (step S209).

[0068] When the communication device 10-1 receives the response signal transmitted from the communication device 10-3, it updates (adds new information or overwrites) the connection destination information stored in itself based on the connection information contained in the response signal. This updates the connection destination information after the optical path switching. Furthermore, when the control device 30a receives the completion notification transmitted from the communication device 10-1, it completes the implementation of the optical path connection switching. This completes the operation of the communication system 1a when switching the optical path, as shown in the sequence diagram of FIG. 9.

[0069] As described above, in the communication system 1a according to the second embodiment of the present invention, the control device 30a controls a plurality of communication devices 10 that communicate with each other using a hierarchical protocol, and the optical path switching device 20 that switches the optical path of the communication. When the control device 30a detects the start of path switching for the communication, it causes the optical path switching device 20 to perform path switching. The control device 30a is configured to erase information from a correspondence table (connection destination information) used in the communication device 10 that is the target of path switching (i.e., the connection source communication device 10), in which upper protocols and lower protocols are associated with each other.

[0070] By having such a configuration, the communication system 1a in the second embodiment of the present invention can erase the connection destination information stored in the communication device 10 from which the connection originates in accordance with the timing of switching the optical path, thereby encouraging the device to voluntarily re-learn the correspondence table (connection destination information) earlier, thereby further shortening the time during which communication interruptions occur.

[0071] According to the above-described embodiment, a communication control device that controls multiple communication devices that communicate with each other using a hierarchical communication protocol includes a detection unit and an update control unit. For example, the communication device is communication device 10 in the embodiment, and the communication control device is control device 30 in the embodiment. The detection unit detects the start of communication path switching. When the start of path switching is detected, the update control unit updates a correspondence table used in the communication device that is the target of path switching, which corresponds upper protocols to lower protocols.

[0072] In the above-described communication control device, the multiple communication devices may include at least a first communication device, a second communication device, and a third communication device. For example, the first communication device is communication device 10-1 in the embodiment, the second communication device is communication device 10-2 in the embodiment, and the third communication device is communication device 10-3 in the embodiment. When the communication device with which the first communication device communicates is switched from the second communication device to the third communication device, the update control unit may update the correspondence table used by the first communication device and the correspondence table used by the third communication device.

[0073] The communication control device may further include a switching control unit. When the correspondence table has been updated, the switching control unit may cause a switching device that relays communications between multiple communication devices to perform path switching. For example, the switching device is the optical path switching device 20 in the embodiment.

[0074] In the above-described communication control device, the upper protocol may be an IP address and the lower protocol may be a MAC address. Alternatively, the upper protocol may be HTTP and the lower protocol may be an IP address. Alternatively, the upper protocol may be a MAC address and the lower protocol may be a physical interface. Alternatively, the upper protocol may be a layer 2 protocol and the lower protocol may be a layer 3 protocol.

[0075] According to the above-described embodiment, a communication control device that controls multiple communication devices that communicate with each other using a hierarchical communication protocol includes a detection unit and a deletion control unit. For example, the communication devices are communication device 10 in the embodiment, and the communication control device is control device 30a in the embodiment. The detection unit detects the start of communication path switching. When the start of path switching is detected, the deletion control unit deletes information included in a correspondence table used in the communication device that is the target of path switching, which corresponds upper protocols to lower protocols.

[0076] In the above-described communication control device, the multiple communication devices may include at least a first communication device, a second communication device, and a third communication device. For example, the first communication device is communication device 10-1 in the embodiment, the second communication device is communication device 10-2 in the embodiment, and the third communication device is communication device 10-3 in the embodiment. The deletion control unit may delete information included in the correspondence table used by the first communication device when the communication device with which the first communication device communicates is switched from the second communication device to the third communication device.

[0077] The communication device 10, the optical path switching device 20, and the control devices 30 and 30a in the above-described embodiments may be partially or entirely implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within a computer system serving as a server or client. The program may be for implementing some of the functions described above, or may be capable of implementing the functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0078] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0079] 1, 1a communication system, 10, 10-1 to 10-3 communication device, 20 optical path switching device, 30, 30a control device, 100 network device, 130 deletion unit, 131 address cache, 140 interconnection topology determination unit, 150 address cache update control unit

Claims

1. A communication control device that controls a plurality of communication devices that communicate with each other using a communication protocol having a hierarchical structure, comprising: a detection unit that detects the start of a route switch for the communication; and an update control unit that, when the start of the route switch is detected, updates a correspondence table used in the communication device that is the target of the route switch, in which higher-level protocols are associated with lower-level protocols.

2. The communication control device according to claim 1, wherein the plurality of communication devices include at least a first communication device, a second communication device, and a third communication device, and the update control unit updates the correspondence table used by the first communication device and the correspondence table used by the third communication device when the communication device with which the first communication device communicates is switched from the second communication device to the third communication device.

3. The communication control device according to claim 1, further comprising a switching control unit that, when updating of the correspondence table is completed, causes a switching device that relays the communications by the plurality of communication devices to execute the path switching.

4. The communication control device according to claim 1, wherein the upper protocol is an IP (Internet Protocol) address, and the lower protocol is a MAC (Media Access Control) address.

5. A communication control device that controls a plurality of communication devices that communicate with each other using a communication protocol having a hierarchical structure, comprising: a detection unit that detects the start of a route switch for the communication; and an erasure control unit that, when the start of the route switch is detected, erases information contained in a correspondence table used in the communication device that is the target of the route switch, in which higher-level protocols are associated with lower-level protocols.

6. A communication control device as described in claim 5, wherein the plurality of communication devices include at least a first communication device, a second communication device, and a third communication device, and the deletion control unit deletes the information contained in the correspondence table used by the first communication device when the communication device with which the first communication device communicates is switched from the second communication device to the third communication device.

7. A communication control method by a computer that controls multiple communication devices that communicate with each other using a communication protocol with a hierarchical structure, comprising: a detection step of detecting the start of a route switch for the communication; and an update control step of, when the start of the route switch is detected, updating a correspondence table used in the communication device that is the target of the route switch, the correspondence table in which upper protocols and lower protocols are associated.

8. A communication control method by a computer that controls multiple communication devices that communicate with each other using a communication protocol with a hierarchical structure, comprising: a detection step of detecting the start of a route switch for the communication; and an erasure control step of erasing information contained in a correspondence table used in the communication device that is the target of the route switch, where the correspondence table associates upper protocols with lower protocols, when the start of the route switch is detected.

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