Control device and control method for controlling communication apparatus

A control device for controlling a communication apparatus having a first operation mode in which power with which a network communication function is operable is supplied, and a second operation mode in which power with which an operation of at least part of the network communication function is restricted is supplied, the control device includes a first determination unit configured to determine whether a packet received in the second operation mode is a packet for use in generating an Internet Protocol (IP) address, and a control unit configured to, in a case where the first determination unit determines that the received packet is not a packet for use in generating an IP address, control the communication apparatus not to shift from the second operation mode to the first operation mode.

BACKGROUND

Field of the Disclosure

The present disclosure relates to a control device and a control method for controlling a communication apparatus.

Description of the Related Art

In recent years, there has been a growing demand for power saving. Thus, an apparatus having the following mechanism has come to be commonly used. The mechanism works in such a manner that when an apparatus is not used, the mechanism shifts the apparatus to a standby mode in which the amount of consumed power is kept low, and when a necessary task occurs, the mechanism shifts the apparatus to a normal mode, which is an operation state where the normal amount of power is consumed.

Further, as a method for shifting an apparatus from a standby mode to a normal mode by a remote operation, a dedicated remote controller using an infrared communication function has been generally used until now. In recent years, some of the apparatuses having a network communication function using a wired local area network (LAN) or a wireless LAN and capable of shifting from a standby mode to a normal mode by a remote operation using a network communication function have become available. A standby mode of an apparatus having such a network communication function is also sometimes referred to as a “network standby mode”.

Examples of the network standby mode include a mode in which, while all the functions of the apparatus are operable, clocks are slowed down to degrade the performance of the functions, thereby achieving a power saving state. Further, examples of the network standby mode include the mode in which the supply of power and clocks to components other than the network communication function units is stopped and the use of only part of a memory is allowed, thereby achieving further power saving. In such a case, it is also necessary to implement a small-sized program to be used in the network standby mode. This leads to the state where only part of the network communication function can be executed in the network standby mode.

Meanwhile, to communicate with another apparatus on a network, each apparatus needs to have an Internet Protocol (IP) address. Some IP addresses have an expiration date. Thus, it is necessary to manage the IP address by performing the process of extending the expiration date where necessary, and performing control so that the expired IP address is not used.

As described above, the apparatus in the network standby mode can execute only part of the network communication function due to the limitation of resources. Thus, some apparatus may not have the function of managing the IP address expiration date in the network standby mode. In other words, some of the apparatuses have the function of managing the IP address expiration date only in the normal mode.

A technique for acquiring an IP address from a Dynamic Host Configuration Protocol (DHCP) server in a normal mode, thereafter setting to a wake-up timer a time determined according to an IP address expiration date, and then shifting to a network standby mode is discussed in Japanese Patent Application Laid-Open No. 2009-27348. In Japanese Patent Application Laid-Open No. 2009-27348, if the wake-up timer has timed out, the apparatus shifts to the normal mode and transmits a request to extend the IP address expiration date.

By such a technique, the apparatus can manage the IP address expiration date without having the function of managing the IP address expiration date in the network standby mode.

As described above, an apparatus can acquire an IP address using a DHCP server. Further, the apparatus can acquire an IP address by an Internet Protocol version 6 (IPv6) address automatic configuration function, if using the IPv6 standard. In the following description, an IP address generated by the IPv6 address automatic configuration function is referred to as an “IPv6 automatic configuration address” (or simply as an “IPv6 address”).

This IPv6 automatic configuration address also has an expiration date. Thus, it is necessary to manage the IPv6 automatic configuration address so that the expired IPv6 automatic configuration address is not used.

The apparatus can generate an IP address (hereinafter referred to as a “temporary IP address”) based on prefix information attached to a router advertisement packet. Using a duplicate address detection function, the apparatus confirms whether another apparatus having the same temporary IP address is present on a network. If it is confirmed that the temporary IP address is not used by another apparatus, the apparatus newly registers the temporary IP address as an IPv6 automatic configuration address of the apparatus. At this time, the apparatus determines the expiration date of the IPv6 automatic configuration address based on prefix expiration date information attached to the router advertisement packet.

Further, if the apparatus already has the same IP address (IPv6 automatic configuration address) in the apparatus when generating the temporary IP address, the apparatus updates the expiration date of the IPv6 automatic configuration address already owned by the apparatus (instead of newly registering the generated temporary IP address).

As described above, in the mechanism of an IPv6 address automatic configuration, the role of a router advertisement packet differs depending on the management state of an IP address of an apparatus that has received the router advertisement packet.

In the conventional art, a wake-up timer is used according to an IP address expiration date. If the time to make a request to extend the expiration date arrives, an apparatus shifts from a network standby mode to a normal mode and performs processing. Further, the apparatus wakes up in the normal mode and then processes a packet that cannot be processed in the network standby mode. In the case of an IPv6 automatic configuration address, however, this technique alone causes a problem in the following case.

This problem arises in an apparatus not having the function of setting the wake-up timer according to the IP address expiration date for managing the IP address expiration date in the network standby mode. More specifically, every time the apparatus receives a router advertisement packet in the network standby mode, the apparatus shifts to the normal mode even if the apparatus does not actually need to shift to the normal mode. As a result, power saving effects are reduced.

More specifically, if the processing to be performed when this router advertisement packet is received is the update of an IP address expiration date, the apparatus does not need to shift to the normal mode. This is because the wake-up timer manages the IP address expiration date. Thus, the apparatus needs to shift to the normal mode only when the apparatus newly registers an IP address. If the apparatus shifts to the normal mode in other cases, this results in reduction of power saving effects.

If, on the other hand, the apparatus ignores a router advertisement packet received in the network standby mode, the following inconvenience occurs. This is a case where, in the network standby mode, prefix information is replaced with that of a router device different from the past one. Other apparatuses on a network can each generate a new IP address based on a router advertisement packet from the new router device, and other apparatuses can communicate with each other. However, in the case of the apparatus that ignores a router advertisement packet and shifts to the normal mode only by the wake-up timer, the apparatus uses an old IP address until the wake-up timer times out. As a result, communication with other apparatuses stops. In other words, the apparatus cannot receive a wake-up trigger packet transmitted from another apparatus to wake up the apparatus from the network standby mode, and an inconvenience occurs to the apparatus and a user.

SUMMARY

The present disclosure is directed to a control device for preventing a reduction in the power saving effects of a communication apparatus.

According to an aspect of the present disclosure, a control device for controlling a communication apparatus having a first operation mode in which power with which a network communication function is operable is supplied, and a second operation mode in which power with which an operation of at least part of the network communication function is restricted is supplied, the control device includes a first determination unit configured to determine whether a packet received in the second operation mode is a packet for use in generating an Internet Protocol (IP) address, and a control unit configured to, in a case where the first determination unit determines that the received packet is not a packet for use in generating an IP address, control the communication apparatus not to shift from the second operation mode to the first operation mode.

DESCRIPTION OF THE EMBODIMENTS

A communication apparatus according to exemplary embodiments of the present disclosure will be described in detail below with reference to the drawings. The technical scope of the present disclosure is determined by the appended claims, and is not limited by the following exemplary embodiments. For example, the configurations of the exemplary embodiments can be appropriately modified or changed depending on the specifications of an apparatus to which the present disclosure is applied, or various conditions (the use conditions and the use environment).

In a first exemplary embodiment, a description is given of the management of an Internet Protocol (IP) address expiration date of a communication apparatus having a power saving mode for disabling all functions except for some network functions. In the present exemplary embodiment, a projector is described as an example of the communication apparatus.

<Configuration of Functional Blocks of Projector1>

First, the configuration of functional blocks of a projector1will be described with reference toFIG. 1.

The projector1includes a processing control unit10, an image processing unit11, an application processing unit12, a network communication processing unit13, an IP address management unit15, a mode shift control unit19, and a wake-up timer20. Among these components, the processing control unit10, the network communication processing unit13, and the IP address management unit15are functional units configuring a network communication function of the projector1. The projector1can operate in either of a normal mode and a network standby mode. When the projector1is in the normal mode, power is supplied so that the entire network communication function is operable. Further, when the projector1is in the network standby mode, power is supplied so that only part of the network communication function is operable. In other words, in the network standby mode, power is supplied so that the operation of part of the network communication function of the projector1is restricted. Among the functional units configuring the network communication function illustrated inFIG. 1, functional units operable even in the network standby mode include part of the processing control unit10, the network communication processing unit13, the packet determination unit14, the temporary IP address generation unit17, and the IP address comparison unit18. If the state where the projector1has no task of projecting an image continues for a predetermined time, the projector1shifts from the normal mode to the network standby mode. The projector1can connect to a network N.

The processing control unit10controls the entire processing of the projector1and controls the processing order of processing blocks.

The image processing unit11converts image data into projection data to be projected by a projection unit44inFIG. 5.

The application processing unit12executes an application program for performing processing according to an operation and an input by a user. Further, the application processing unit12also executes an application program for performing the process of managing image data or managing communication settings, which is performed voluntarily by the projector1instead of a user operation.

The network communication processing unit13executes network communication processing. More specifically, the network communication processing unit13executes Transmission Control Protocol (TCP) protocol processing, User Datagram Protocol (UDP) protocol processing, IP protocol processing, and physical layer/media access control (PHY/MAC) protocol processing. The network communication processing unit13includes a packet determination unit14.

The packet determination unit14determines whether a packet received from the network N is a packet for use in generating an IP address or a packet for use in updating an IP address expiration date.

The IP address management unit15holds an IP address of the projector1and an IP address of a communication partner apparatus. The projector1can have a plurality of IP addresses, and the IP address management unit15can also hold a plurality of IP addresses. Further, the IP address management unit15can also hold IP addresses of a plurality of communication partner apparatuses. The IP address management unit15includes an IP address registration unit16, a temporary IP address generation unit17, and an IP address comparison unit18.

The IP address registration unit16receives a request to newly hold an IP address, and performs management control so that the IP address management unit15holds the IP address for which the request is made.

The temporary IP address generation unit17generates an IP address using prefix information attached to a received packet for use in generating an IP address. The generated IP address is an IP address before being subjected to the registration management of the IP address management unit15and therefore is referred to as a “temporary IP address”.

The IP address comparison unit18compares a temporary IP address with IP addresses of the projector1held in the IP address management unit15and determines whether there is an IP address that coincides with the temporary IP address.

The mode shift control unit19controls the shift of the operation mode of the projector1. That is, the mode shift control unit19controls the shift of the operation mode between the normal mode in which power is supplied so that the entire network communication function is operable and the network standby mode in which power is supplied so that only part of the network communication function is operable.

The wake-up timer20notifies the mode shift control unit19that the time to shift from the network standby mode to the normal mode has arrived. For example, the wake-up timer20is set to a time according to an IP address expiration date.

A network configuration according to the present exemplary embodiment will be described with reference toFIG. 2. An example will be described where the projector1is connected to another communication apparatus via a network.

In the example ofFIG. 2, the projector1is connected to a first wired local area network (LAN) N1using a network interface36(illustrated inFIG. 5, e.g., a 1000BASE-T Ethernet module). On the first wired LAN N1, a first router device2is present. The first router device2is connected to the Internet3. Beyond the Internet3, a second router device4is present on a second wired LAN N2. On the second wired LAN N2, a personal computer (PC)5is present. In this network configuration, the first router device2and the second router device4are used as gateways.

The network configuration inFIG. 2allows, in a remote conference, image data on a monitor screen of the PC5to be transferred to the projector1via the Internet3and the transferred image data to be projected by the projector1. The network N inFIG. 1refers to the first wired LAN N1inFIG. 2. Alternatively, the network N inFIG. 1may refer to a communication network from the first wired LAN N1to the Internet3, or may refer to a communication network from the first wired LAN N1to the second wired LAN N2.

The first router device2and the second router device4are compatible with Internet Protocol version 6 (IPv6). The first router device2periodically transmits a router advertisement packet onto the wired LAN N1. Further, the second router device4periodically transmits a router advertisement packet onto the wired LAN N2. If the projector1receives the router advertisement packet transmitted from the first router device2, the projector1generates an IPv6 automatic configuration address from prefix information attached to the router advertisement packet. Further, the projector1sets the expiration date of the generated IPv6 automatic configuration address from prefix expiration date information attached to the router advertisement packet. Similarly, if the PC5receives the router advertisement packet transmitted from the second router device4, the PC5generates an IPv6 automatic configuration address from prefix information attached to the router advertisement packet and sets the expiration date of the IPv6 automatic configuration address.

The projector1and the PC5can perform network communication (communication via the network N1, the Internet3, and the network N2) using the IPv6 automatic configuration addresses respectively generated by the projector1and the PC5.

<Processing Until Projector1Shifts to Network Standby Mode>

In the following description, it is assumed that the projector1has already acquired an IPv6 automatic configuration address from the first router device2. Further, it is assumed that the projector1has already finished projection, and the state where an instruction to project an image is not given is continuing now.

If the state where an instruction to project an image is not given to the projector1continues for a predetermined time, the mode shift control unit19shifts the operation mode of the projector1from the normal mode to the network standby mode. When performing this operation mode shift processing, the mode shift control unit19determines a timer value according to an IP address having the earliest expiration date among the IP addresses of the projector1held in the IP address management unit15. For example, the mode shift control unit19determines several minutes before the expiration as a timer value, or determines a period of half the time until the expiration date as a timer value, or determines several percent of the time until the expiration date as a timer value. Then, the mode shift control unit19sets the wake-up timer20to the determined timer value. If the expiration date of the IP address is set to infinity, or if the expiration date of the IP address is set to a time having a value greater than a predetermined threshold, the mode shift control unit19may or may not set the wake-up timer20. “The wake-up timer20is not set” means that, for example, the mode shift control unit19disables the timer setting of the wake-up timer20. Further, if the expiration date of the IP address is greater than the predetermined threshold, the mode shift control unit19may set the expiration date to the threshold and then determine a timer value, or may not set the wake-up timer20.

<Processing Flow in Network Standby Mode>

Based on a flowchart inFIG. 3, the processing of the projector1in the network standby mode will be described below.

If the projector1enters the network standby mode, then in step S1, the processing control unit10confirms whether the wake-up timer20has timed out. If the wake-up timer20has timed out (YES in step S1), the processing control unit10instructs the mode shift control unit19to shift the projector1from the network standby mode to the normal mode.

If the wake-up timer20has not timed out (NO in step S1), then in step S2, the processing control unit10confirms whether the network interface36(FIG. 5) has received a packet. If the network interface36has not received a packet (NO in step S2), the processing returns to step S1. In step S1, the processing control unit10confirms the timeout of the wake-up timer20. If the network interface36has received a packet (YES in step S2), then in step S3, the network communication processing unit13causes the packet determination unit14to determine whether the received packet is a packet for use in generating an IP address. More specifically, the packet determination unit14determines whether the received packet is a packet for use in generating an IP address or a packet for use in updating an IP address expiration date. For example, in step S3, the packet determination unit14determines whether the received packet is a router advertisement packet (a type134packet of Internet Control Message Protocol for the Internet Protocol version 6 (ICMPv6)).

If the received packet is a packet for use in generating an IP address (YES in step S3), the processing proceeds to step S4. In step S4, the IP address management unit15causes the temporary IP address generation unit17to generate a temporary IP address. Specifically, based on prefix information attached to the router advertisement packet, the temporary IP address generation unit17generates an IPv6 automatic configuration address and sets the generated IPv6 automatic configuration address as a temporary IP address. The temporary IP address is an IP address generated by an IPv6 address automatic configuration function.

Next, in step S5, the IP address management unit15causes the IP address comparison unit18to determine whether the temporary IP address generated in step S4coincides with an IP address already held as an IP address of the projector1. This determination is made by comparing the temporary IP address generated in step S4with an IP address already held as an IP address of the projector1.

Although the temporary IP address and an IP address already held in the projector1are compared in step S5, other pieces of information may be compared. For example, prefix information attached to the router advertisement packet and part of an IP address, such as a subnet prefix portion, already held in the projector1may be compared to determine whether the prefix information and the part of the IP address coincide with each other. In this case, a temporary IP address need not be generated in step S4.

If an IP address that coincides with the temporary IP address is found in step S5(YES in step S5), then in step S6, the IP address management unit15discards the received packet. Then, the subsequent processing on the received packet is not continued, and the processing returns to step S1. If an IP address that coincides with the temporary IP address is not found (NO in step S5), then in step S7, the IP address management unit15confirms the number of held IP addresses (the number of IP addresses) of the projector1held in the IP address management unit15and determines whether the number of held IP addresses has already reached a management upper limit (the upper limit of the number of IP addresses that can be held). If the number of held IP addresses has reached the management upper limit (YES in step S7), it is not possible to newly register an IP address even if the projector1shifts to the normal mode. Accordingly, the projector1does not shift to the normal mode, and the processing proceeds to step S6. In step S6, the IP address management unit15discards the received packet, and then, the processing returns to step S1. If the number of held IP addresses has not reached the management upper limit (the upper limit of the number of IP addresses that can be held) (NO in step S7), the mode shift control unit19shifts the projector1from the network standby mode to the normal mode. Step S7does not necessarily have to be performed subsequent to step S5. For example, step S7may be performed between steps S3and S4, or may be performed between steps S4and S5. Further, if it is determined in step S7that the number of held IP addresses has reached the management upper limit, an IP address that is not used for a predetermined period (or the oldest IP address) among the IP addresses of the projector1may be deleted to reserve an area where an IP address can be held. Then, the projector1may shift to the normal mode.

If the received packet is not a packet for use in generating an IP address (NO in step S3), the processing proceeds to step S8. In step S8, the packet determination unit14determines whether the received packet is a packet that requires a shift to the normal mode. A case where it is determined that the received packet is a packet that requires a shift to the normal mode corresponds to a case where the PC5transmits image data to the projector1, or a case where another apparatus transmits a packet as a wake-up trigger to the projector1to use the projector1. The projector1can determine a wake-up condition in advance based on a protocol type and a port number. If the projector1receives a packet satisfying this condition, the projector1can determine that the received packet is a packet serving as a wake-up trigger. If it is determined in step S8that the received packet is a packet serving as a wake-up trigger (YES in step S8), the processing control unit10instructs the mode shift control unit19to shift the projector1from the network standby mode to the normal mode. Further, if it is determined that the received packet is not a packet serving as a wake-up trigger (NO in step S8), then in step S9, the processing control unit10performs reception processing according to the received packet. Then, the processing returns to step S1.

<Processing Flow in Normal Mode>

Based on a flowchart inFIG. 4, the processing of the projector1in the normal mode will be described.

If the projector1shifts to the normal mode, then in step S21, the IP address management unit15causes the IP address registration unit16to perform IP address registration processing. Specifically, the IP address management unit15newly holds, as an IP address of the projector1, the temporary IP address generated in step S4inFIG. 3.

Then, in step S22, the application processing unit12performs application processing where necessary.

After the application processing ends, then in step S23, the processing control unit10determines whether there is an application that has not yet been processed. If there is still an application that should be processed (YES in step S23), the processing returns to step S22. In step S22, the application processing unit12performs application processing on this application. Then, if there is no application that should be processed (NO in step S23), then in step S24, the mode shift control unit19sets the wake-up timer20and shifts the projector1from the normal mode to the network standby mode.

Based on the above-mentioned flow, the projector1operates in either of the normal mode and the network standby mode.

<Effects of First Exemplary Embodiment>

As described above, according to the present exemplary embodiment, in step S3, the packet determination unit14determines whether the received packet is a packet for use in generating an IP address or a packet for use in updating an IP address expiration date. If this determination is YES, then in step S4, the temporary IP address generation unit17generates a temporary IP address. In step S5, the IP address comparison unit18determines whether the temporary IP address coincides with an IP address already held in the projector1. Then, if this determination is YES, the projector1does not shift to the normal mode, and the IP address management unit15discards the received packet. Thus, if a router advertisement packet is received in the network standby mode, the projector1does not immediately shift to the normal mode, but first determines whether it is necessary to generate and register an IP address. If it is necessary to newly register an IP address, the projector1shifts to the normal mode. If not, the projector1does not shift to the normal mode, and remains in the network standby mode. Thus, the projector1shifts to the normal mode only if necessary. If not, the projector1can avoid shifting to the normal mode. By such control of the operation mode, it is possible to prevent a reduction in the power saving effects of the projector1.

Further, even if it is determined that it is not necessary to generate an IP address (NO in step S3), then in step S8, the packet determination unit14determines whether the projector1should shift to the normal mode for a reason other than the generation of an IP address. Thus, if the projector1should shift to a normal mode, the projector1shifts to the normal mode without fail.

The present exemplary embodiment is useful particularly in a case where the projector1does not have the function of managing the IP address expiration date in the network standby mode.

FIG. 5illustrates the hardware configuration of the projector1. The projector1includes a network communication unit30and an application system unit40.

The network communication unit30can communicate with another communication apparatus (e.g., the PC5inFIG. 2) via a network. The application system unit40controls the network communication unit30, thereby outputting, from a projection unit44, image data received from another communication apparatus.

The network communication unit30includes a communication control unit31, a local random-access memory (RAM)32, a protocol processing unit33, and a bus bridge34. These hardware modules are connected to each other by a local bus35. The local bus35is connected to a system bus48of the application system unit40by the bus bridge34.

A network interface36connects the network and the projector1and is a terminal for physical input and output from and to the network. The network interface36is, for example, a wireless LAN module compatible with the wireless LAN 802.11ac standard, or a 1000BASE-T Ethernet module for a wired LAN. In the present exemplary embodiment, the network interface36is a 1000BASE-T Ethernet module.

The communication control unit31transmits and receives, for example, packets compliant with TCP/IP to and from another communication apparatus via the network. The local RAM32temporarily stores (buffers) data (transmission data and reception data) necessary for the communication control unit31to transmit and receive packets. The protocol processing unit33performs various types of protocol processing for performing communication compliant with TCP/IP. For example, the protocol processing unit33performs the header analysis of a received packet, transmission flow control, congestion control, and communication error control. Further, the protocol processing unit33also controls a power supply control unit46(described below).

The application system unit40includes a central processing unit (CPU)41, a read-only memory (ROM)42, a RAM43, a projection unit44, a user interface45, a power supply control unit46, and a clock47. These hardware modules are connected together by the system bus48.

The CPU41reads and executes a program stored in the ROM42, thereby controlling the application system unit40to project an image. For example, the CPU41executes a program stored in the ROM42, thereby performing the processes of the steps inFIGS. 3 and 5. The functions of the respective functional blocks inFIG. 1are achieved by the CPU41executing a program stored in the ROM42.

The RAM43is used as a work memory for the CPU41to read and execute a program. The RAM43stores, for example, image data before being processed by the image processing unit11(FIG. 1). The RAM43can function as an image data storage unit.

The projection unit44includes a lens, a light source lamp, and a liquid crystal panel. The projection unit44emits light from the light source lamp, passes the light through the liquid crystal panel, and projects the light from the lens.

The user interface45is used by the user to perform various inputs and operations. For example, the user can perform an operation such as setting the image quality of a projection image, using the user interface45.

The power supply control unit46performs power supply control and reset processing on various hardware modules of the application system unit40. Further, the power supply control unit46operates based on an instruction from the protocol processing unit33.

When the projector1is in the normal mode, the power supply control unit46enters the state where power is supplied to various hardware modules of the application system unit40. In the normal mode, the projector1can receive image data from another communication apparatus and project an image.

In the network standby mode, the power supply control unit46does not supply power to various hardware modules of the application system unit40. In the network standby mode, the projector1is in a low power consumption state. In the network standby mode, the power consumption of the projector1is reduced as compared with the normal mode. In the network standby mode, the projector1cannot project image data received from another communication apparatus. However, even in the network standby mode, power is supplied to the network communication unit30. Thus, the projector1can receive a request to start communication or projection, or an Address Resolution Protocol (ARP) packet from another communication apparatus via the network. The request to start communication is, for example, a connection request packet for a TCP connection (a TCP/SYN packet). If the projector1receives an ARP packet addressed to an IP address of the projector1, the projector1notifies a partner apparatus having transmitted the ARP packet of the MAC address of the projector1. If the projector1is operating in the normal mode, a program corresponding to each of the functional blocks illustrated inFIG. 1is loaded into the RAM43or the local RAM32and executed by the CPU41, the communication control unit31, or the protocol processing unit33. Then, if the projector1shifts to the network standby mode, the programs corresponding to the functions operable even in the network standby mode among the functional blocks illustrated inFIG. 1are copied from the ROM42or the RAM43into the local RAM32. Consequently, in the projector1, part of the network communication function is operable even in the network standby mode, i.e., in the state where power is not supplied to the application system unit40.

The hardware modules41to46may operate according to a clock signal from the clock47.

Although a projector has been described as an example of the communication apparatus in the above exemplary embodiment, the communication apparatus according to the present disclosure is not limited to a projector. The present disclosure can be applied to any apparatus capable of operating in two or more operation modes (operation modes different in power consumption) and receiving a router advertisement packet. For example, a printing apparatus, a display apparatus, or a sound apparatus can also be used as the communication apparatus. In this case, the projection unit44inFIG. 5is replaced with an output unit (e.g., a printing unit) appropriate for the output of the communication apparatus. The communication apparatus may be, for example, a camera, a smartphone, a printer, a mobile phone, a PC, a video camera, a smartwatch, or a personal digital assistant (PDA).

Further, the connection between the communication apparatus1and another communication apparatus may be wired or wireless, or may be a connection not via the Internet.

In step S3, it is determined whether the received packet is a packet for use in generating an IP address or a packet for use in updating an IP address expiration date. Alternatively, it may be only determined whether the received packet is a packet for use in generating an IP address.

The functional blocks illustrated inFIG. 1are merely illustrative. Alternatively, a plurality of functional blocks may be included in a single functional block, or any one of the functional blocks may be divided into blocks for performing a plurality of functions. Yet alternatively, at least one of the functional blocks may be implemented as hardware. If the functional blocks are implemented as hardware, a dedicated circuit may be automatically generated on a field-programmable gate array (FPGA) from a program for achieving each step, for example, using a predetermined compiler. Further, a gate array circuit may be formed and achieved as hardware just as in the case of the FPGA. Further, the functional blocks may be achieved by an application-specific integrated circuit (ASIC).

Other Embodiments

While the present disclosure has been described with reference to exemplary embodiments, the scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2016-182954, filed Sep. 20, 2016, which is hereby incorporated by reference herein in its entirety.