Patent Publication Number: US-2015063161-A1

Title: Relay device, communication system, and method of acquiring node setting information

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of the Japanese Patent Application No. 2013-175262, filed on Aug. 27, 2013, which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a relay device that is connected to a node and connects the node to a network. 
     2. Description of the Related Art 
     In recent years, a wireless access point (wireless AP) is installed in companies, schools, hospitals, and the like, and introduction of a wireless LAN (Local Area Network) environment has progressed. 
     The wireless LAN eliminates the need to perform LAN cable wiring, thereby facilitating network construction and network change and increasing freedom of floor layout. Further, the wireless LAN allows operation requiring network access everywhere (one&#39;s desk, conference room, meeting spot, etc.) without discrimination. These advantages have accelerated the introduction of the wireless LAN environment. 
     Further, a rapid prevalence of devices that are not provided with a wired LAN port, such as a smartphone and a tablet terminal, increases the need for introduction of the wireless LAN environment in companies and the like. 
     Further, an increased interest in a BYOD (Bring Your Own Device) an increasing trend of employees bringing their own devices to work is also cited as background of the increase in the need for introduction of the wireless LAN environment, and it is estimated that the number of companies that introduce a wireless LAN-based Network increases. 
     However, there are many issues facing the introduction of the wireless LAN, and it is a fact that many companies are concerned about an increase in an operation and maintenance load during and after the introduction and about security. 
     In general, a company or the like itself purchases spare parts of the wireless AP and replaces the wireless AP with a new one as needed. Therefore, it is required that an administrator can perform the replacement of the wireless AP without special network knowledge. However, the administrator needs to initially set in the wireless AP download destination address information or the like which is required for automatically downloading setting information (configuration information). That is, complete zero-configuration is not realized, and thus the administrator is required to have network knowledge. 
     There is disclosed JP-2009-246414-A as a prior art relating to the present technical field. This describes “A configuration transmission method for transmitting configuration stored in a server connected to a WAN through a router to a terminal connected to a LAN, wherein the router acquires the configuration from the server through an external network, the terminal transmits a first command for address request through the LAN to the router when activated, the router transmits a second command including an initial setting instruction together with an address through the LAN to the terminal, and, when receiving the second command from the router through the LAN, the terminal transmits a third command requesting the configuration through the LAN to the router, and, when receiving the third command from the terminal through the LAN, the router transmits the configuration through the LAN to the terminal” (see Abstract). 
     SUMMARY OF THE INVENTION 
     However, in the technology described in the JP-2009-246414-A, it is necessary to manually register an ID and a password for accessing an HTTP/HTTPS server in the terminal, that is, complete zero-configuration is not realized. 
     An object of the present invention is to provide a relay device capable of automatically performing initial setting of a node without the need of manual setting. 
     One typical example of the present invention is a relay device connected to a node and connecting the node to a network, the relay device being connected to a setting information storage device that stores setting information of the node through the network and having at least one physical port connected to the node, wherein when receiving an address acquisition request which is a request for acquiring an address to be set in the node from the node through the physical port, the relay device transmits, to the node, an address acquisition reply including the address to be set in the node, node information identifying the node that has transmitted the address acquisition request, and an address of the setting information storage device, transmits, to the setting information storage device, a setting information acquisition request which is a request that the node has transmitted to acquire setting information of the node and which includes the node information with the address of the setting information storage device set as a destination, and transmits, to the node, setting information which corresponds to the node information included in the setting information acquisition request and which is transmitted from the setting information storage device. 
     An effect obtained by representative aspects of the present invention disclosed in the specification is as follows. That is, there can be provided a relay device capable of automatically performing initial setting of the node. 
     Other objects, configurations, and advantages of the invention will become apparent from the following description of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view of a configuration of a network system according to a first embodiment of the present invention; 
         FIG. 2  is an explanatory view of a DHCP processing section according to first embodiment of the present invention; 
         FIG. 3  is an explanatory view of a wireless AP registration table according to the first embodiment of the present invention; 
         FIG. 4  is an explanatory view of a management server IP registration table according to the first embodiment of the present invention; 
         FIG. 5  is an explanatory view of a setting information management table according to the first embodiment of the present invention; 
         FIG. 6  is a sequence diagram of processing to be performed in the network system when the wireless AP according to the first embodiment of the present invention is replaced with a new one; 
         FIG. 7  is a format diagram of a DHCP packet according to the first embodiment of the present invention; 
         FIG. 8  is a flowchart of packet transfer processing to be executed by a packet relay device according to the first embodiment of the present invention; 
         FIG. 9  is an explanatory view of a DHCP processing section provided in a packet relay device according to a second embodiment of the present invention; 
         FIG. 10  is an explanatory view of a DHCP server according to the second embodiment; 
         FIG. 11  is a sequence diagram of processing to be performed in the network system when the wireless AP according to the second embodiment of the present invention is replaced with a new one; 
         FIG. 12  is a flowchart of packet transfer processing to be executed by the packet relay device according to the second embodiment of the present invention; 
         FIG. 13  is a flowchart of packet transfer processing to be executed by a DHCP server according to the second embodiment of the present invention; 
         FIG. 14  is an explanatory view of a DHCP processing section according to a third embodiment of the present invention; 
         FIG. 15  is a sequence diagram of processing to be performed in the network system when the wireless AP according to the third embodiment of the present invention is replaced with a new one; and 
         FIG. 16  is a flowchart of packet transfer processing to be executed by a packet relay device according to the third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings. 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to  FIGS. 1 to 8 . 
       FIG. 1  is an explanatory view of a configuration of a network system according to a first embodiment of the present invention. 
     The network system in the first embodiment 1 includes a wireless terminal  1 , a wireless access point (wireless AP (node))  10 , a packet relay device (relay device)  20 , a management server (setting information storage device)  30 , and a DHCP (Dynamic Host Configuration Protocol) server  40  (address distributor). 
     The packet relay device  20 , which is configured to connect a plurality of communication lines to each other, is connected to the wireless AP  10  and connected, through a network  50 , to the management server  30  and DHCP server  40 . The wireless AP  10  is a radio wave relay device connected by wireless to the wireless terminal  1  (e.g., a smartphone, a tablet terminal, etc.). The management server  30  stores setting information corresponding to the wireless AP  10  and transmits the setting information to the wireless AP  10  in response to a request from the wireless AP  10 . The DHCP server  40  distributes an IP address and the like to the wireless AP  10 . 
     First, the packet relay device  20  will be described. 
     The packet relay device  20  includes a packet processing section  210 , a processor  220 , a memory  230 , and physical ports  240  and  241 . The packet processing section  210 , processor  220 , memory  230 , and physical ports  240 ,  241  are connected to each other through a bus  242  and the like. 
     The physical port  240  is connected to a physical port  170  provided in the wireless AP  10 , and the physical port  241  is connected to the network  50  through a line. Unique identification information are given without overlaps to the physical ports  240  and  241 , respectively, in the packet relay device  20 , and thereby the physical ports  240  and  241  are uniquely identified by the given identification information. The physical port is hereinafter referred to merely as “port.” In the packet relay device  20 , the physical ports  240  and  241  are each used as a port to which a single independent line is connected. 
     The packet processing section  210  executes packet processing that determines a physical port to which a packet received by the packet relay device  20  is transmitted. The packet processing section  210  has a DHCP packet determination section  211 . The DHCP packet determination section  211  determines whether or not the packet received by the packet relay device  20  is a DHCP packet. A DHCP is a protocol that automatically assigns necessary information such as an IP address to various devices. Although the packet processing section  210  illustrated in  FIG. 1  is implemented in hardware, it may be implemented in software. 
     The processor  220  executes various programs and includes a DHCP processing section  221 , a wireless AP management section  222 , and a management server IP processing section  223 . 
     The DHCP processing section  221  executes DHCP processing. Details of the DHCP processing section  221  will be described later using  FIG. 2 . The wireless AP management section  222  manages a relationship between the physical port and wireless AP  10  connected to the physical port. The management server IP processing section  223  manages an IP address (address information) of the management server  30  that stores the setting information of the wireless AP  10 . 
     The DHCP processing section  221 , wireless AP management section  222 , and management server IP processing section  223  are each implemented when the processor  220  executes a program corresponding thereto. 
     The memory  230  is a storage area for storing various programs that the processor  220  executes and data that the processor  220  reads therefrom or writes thereto. The memory  230  stores a management server IP registration table  231  and a wireless AP registration table (node information management information)  232 . 
     The IP address of the management server  30  is registered in the management server IP registration table  231 , and the management server IP registration table  231  is referred to by the management server IP processing section  223 . Details of the management server IP registration table  231  will be described later using  FIG. 4 . A correspondence between the identification information of the physical port and a wireless AP name (node information) that identifies the wireless AP to be connected to the physical port is stored in the wireless AP registration table  232 . Details of the wireless AP registration table  232  will be described later using  FIG. 3 . 
     The following describes the wireless AP  10 . The wireless AP  10  includes a wireless transmission/reception section  110 , a packet transmission/reception section  120 , a device IP address management section  130 , a DHCP client processing section  140 , a management server information processing section  150 , and a configuration information setting section  160 . 
     The wireless transmission/reception section  110  receives by wireless a signal transmitted from the wireless terminal  1  and transmits a signal by wireless to the wireless terminal  1 . The packet transmission/reception section  120  receives a packet transmitted from the packet relay device  20  and transmits a packet to the packet relay device  20 . The device IP address management section  130  manages the IP address of the wireless AP  10  distributed from the DHCP server  40 . 
     The DHCP client processing section  140  executes processing relating to the DHCP packet transmitted/received between itself and DHCP server  40 . The DHCP client processing section  140  has a wireless AP information adding section  141 . When the DHCP client processing section  140  transmits the DHCP packet to the DHCP server  40 , the wireless AP information adding section  141  adds wireless AP identification information indicating that the wireless AP  10  is a DHCP client to the DHCP packet. 
     The management server information processing section  150  registers the IP address of the management server  30  that stores the setting information of the wireless AP  10  in a management server IP registration table  151  and acquires the setting information from the management server  30 . The management server information processing section  150  includes the management server IP registration table  151  and a management server inquiry section  152 . 
     The IP address of the management server  30  is registered in the management server IP registration table  151 . The management server inquiry section  152  transmits a setting information acquisition request to the management server  30  and receives the setting information from the management server  30 . 
     The configuration information setting section  160  executes setting processing for the wireless AP  10  based on the setting information acquired from the management server  30 . 
     The DHCP server  40  distributes necessary information such as address information to the DHCP client by using the DHCP. 
     The following describes the management server  30 . The management server  30  stores the setting information of the packet relay device  20  and wireless AP  10  and distributes the setting information to the packet relay device  20  and wireless AP  10 . 
     The management server  30  includes a packet transmission/reception section  310 , a processor  320 , a memory  330 , and a physical port  340 . The packet transmission/reception section  310 , processor  320 , memory  330 , and physical port  340  are connected to each other through a bus  341 . 
     The packet transmission/reception section  310  transmits/receives a packet through the network  50 . 
     The processor  320  executes various programs and includes a setting inquiry reception section  321 , a setting information management section  322 , and a setting information transmission section  323 . The setting inquiry reception section  321  receives the setting information acquisition request transmitted from the wireless AP  10 . The setting information management section  322  manages the setting information corresponding to the wireless AP  10  and searches for setting information corresponding to the setting information acquisition request received by the management server  30 . The setting information transmission section  323  transmits to the wireless AP  10  the setting information corresponding to the setting information acquisition request received by the management server  30 . 
     The setting inquiry reception section  321 , setting information management section  322 , and setting information transmission section  323  are each implemented when the processor  320  executes a program corresponding thereto. 
     The memory  330  is a storage area for storing various programs that the processor  320  executes and data that the processor  320  reads therefrom or writes thereto. The memory  330  stores a setting information management table  331 . A correspondence between the wireless AP name and setting information is registered in the setting information management table  331 . Details of the setting information management table  331  will be described later using  FIG. 5 . 
     The physical port  340  is connected to a line to be connected to the network  50 . 
       FIG. 2  is an explanatory view of the DHCP processing section  221  according to the first embodiment of the present invention. 
     The DHCP processing section  221  includes a DHCP snooping processing section  2210 , a DHCP relay processing section  2220 , and a DHCP server processing section  2230 . 
     The DHCP snooping processing section  2210  executes DHCP snooping processing. The DHCP snooping processing is processing of snooping to which physical port of the packet relay device  20  the DHCP client is connected and filtering a packet based on a result of the snooping. 
     The DHCP relay processing section  2220  executes DHCP relay processing. The DHCP relay processing is processing of receiving the DHCP packet from the DHCP client on behalf of the DHCP server  40  and relaying the DHCP packet, to the DHCP server  40  existing on a different network. 
     The DHCP server processing section  2230  executes DHCP server processing. The DHCP server processing is processing of implementing a function of the DHCP server  40  in the packet relay device  20  and automatically assigning information, such as an IP address of the DHCP client, required for network utilization to the DHCP client. 
     An administrator previously set whether to validate or invalidate the function of each of the DHCP snooping processing section  2210 , DHCP relay processing section  2220 , and DHCP server processing section  2230 . The processing section whose function has been validated executes its own processing, and the processing section whose function has been invalidated does not execute its own processing. It is assumed in the present embodiment that the function of the DHCP snooping processing section  2210  is set valid, while the functions of the DHCP relay processing section  2220  and DHCP server processing section  2230  are set invalid. Processing section setting information (not illustrated) indicating whether each of the processing sections is set valid or invalid is stored in the memory  230 . 
     The DHCP snooping processing section  2210  includes a reception port confirmation section  2211 , a wireless AP determination section  2212 , and a DHCP data adding section  2213 . 
     The reception port confirmation section  2211  identifies a physical port through which the DHCP packet is received. The wireless AP determination section  2212  determines whether or not the wireless AP identification information is stored in Options of the DHCP packet to thereby determine the DHCP client of the DHCP packet is the wireless AP  10 . 
     When it is determined by the wireless AP determination section  2212  that the DHCP client of received DHCP ACK is the wireless AP  10 , the DHCP data adding section  2213  acquires the wireless AP name from the wireless AP registration table  232  and the IP address of the management server  30  from the management server IP registration table  231  based on the identification information of the physical port identified by the reception port confirmation section  2211 . Then, the DHCP data adding section  2213  adds the acquired wireless AP name and IP address of the management server  30  to the received DHCP ACK. 
       FIG. 3  is an explanatory view of the wireless AP registration table  232  according to the first embodiment of the present invention. 
     A correspondence between the identification information of the physical port provided in the packet relay device  20  and wireless AP name based on which the wireless AP  10  connected to the physical port is identified is registered in the wireless AP registration table  232 . The wireless AP registration table  232  is previously set by an administrator. 
     The wireless AP registration table  232  has physical port identification information  301  and a wireless AP name  302 . 
     The identification information (e.g., a port number) of the physical port provided in the packet relay device  20  is registered in the physical port identification information  301 . The wireless AP name of the wireless AP  10  connected to the physical port identified by the identification information registered in the physical port identification information  301  is registered in the wireless AP name  302 . The wireless AP name is information that can identify the wireless AP  10  and is not changed when the wireless AP  10  is replaced with a new one. For example, the wireless AP name is information indicating a position at which the wireless AP  10  is installed. 
     A correspondence between a physical port “1” and a wireless AP name “A,” a correspondence between a physical port “2” and a wireless AP name “B,” and a correspondence between a physical port “3” and a wireless AP name “C” are registered in the wireless AP registration table  232  illustrated in  FIG. 3 . 
     Records corresponding to the number of the physical ports to be connected to the wireless AP  10  may be registered in the wireless AP registration table  232 ; alternatively, a configuration may be adopted, in which records corresponding to the number of all the ports provided in the packet relay device  20  are registered in the wireless AP registration table  232 , and “NULL” is registered as the wireless AP name  302  of the physical port that is not connected to the wireless AP  10 . The identification information of the physical port to be registered in the physical port identification information  301  may be any information as long as it can uniquely identify one of the physical ports provided in the packet relay device  20 . Further, the wireless AP name to be registered in the wireless AP name  302  may be any information as long as it can identify a new wireless AP  10  installed for replacement. 
       FIG. 4  is an explanatory view of the management server IP registration table  231  according to the first embodiment of the present invention. 
     The IP address of the management server  30  that stores the setting information of the wireless AP  10  is registered in the management server IP registration table  231 . The management server IP registration table  231  has a management server IP address  401 , and the IP address of the management server  30  is registered in the management server IP address  401 . Address information, such as a MAC address, of the management server  30  may be registered in the management server IP registration table  231  as long as it can identify the management server  30 . 
     The management server IP registration table  231  is previously set by an administrator. When the management server  30  that stores the setting information differs for each the wireless AP  10 , IP addresses of a plurality of management servers  30  are registered in the management server IP registration table  231 . In this case, the management server IP registration table  231  includes a wireless AP name (not illustrated) and a management server IP address  401 , and in the management server IP registration table  231 , a correspondence between the wireless AP  10  identified by the wireless AP name and IP address of the management server  30  that stores the setting information of the wireless AP  10  is registered. 
       FIG. 5  is an explanatory view of the setting information management table  331  according to the first embodiment of the present invention. 
     In the setting information management table  331 , a correspondence between the wireless AP name and setting information that the management server  30  transmits to the wireless AP  10  identified by the wireless AP name. 
     The setting information management table  331  includes a packet relay device identification information  501 , a physical port identification information  502 , a wireless AP name  503 , and setting information  504 . 
     Identification information of the packet relay device  20  to be connected to the management server  30  is registered in the packet relay device identification information  501 . Identification information of the physical port of each packet relay device  20  to which the wireless AP  10  is connected is registered in the physical port identification information  502 . The wireless AP name of the wireless AP  10  to be connected to each physical port is registered in the wireless AP name  503 . Setting information corresponding to the wireless AP  10  identified by the wireless AP name  503  is registered in the setting information  504 . The setting information includes at least one of, e.g., a radio field intensity of the wireless AP  10 , a channel for the wireless AP  10  to exchange data by wireless with the wireless terminal  1 , and an encryption/authentication method. 
     That is, the setting information management table  331  manages which wireless AP  10  is connected to which physical port of the packet relay device  20  and manages a correspondence between the wireless AP  10  and setting information of the wireless AP  10 . 
     There are registered, in the setting information management table  331  illustrated in  FIG. 5 , a correspondence among a physical port “1” of a packet relay device “SW1,” a wireless AP name “A,” and setting information “a,” a correspondence among a physical port “2” of the packet relay device “SW1,” a wireless AP name “B,” and setting information “b,” a correspondence among a physical port “3” of the packet relay device “SW1”, a wireless AP name “C,” and setting information “c,” a correspondence among a physical port “1” of a packet relay device “SW2,” a wireless AP name “L,” and setting information “1,” and a correspondence among a physical port “3” of the packet relay device “SW2,” a wireless AP name “M,” and setting information “m.” 
     The setting information management table  331  is previously set by an administrator. Further, the correspondence between the identification information of the physical port of the packet relay device  20  and the wireless AP name may be automatically registered in the wireless AP registration table  232  of each packet relay device  20 . Specifically, the management server  30  transmits, to the packet relay device  20  identified by the identification information registered in the packet relay device identification information  501 , a correspondence between the identification information of the physical port registered in the physical port identification information  502  of the setting information management table  331  and the wireless AP name registered in the wireless AP name  503  of the setting information management table  331 . When receiving the correspondence transmitted from the management server  30 , the packet relay device  20  registers the received correspondence in the wireless AP registration table  232 . 
     The identification information of the packet relay device  20  to be registered in the packet relay device identification information  501  may be any information as long as it can uniquely identify the packet relay device  20 . Further, the identification information of the physical port to be registered in the physical port identification information  502  may be any information as long as it can uniquely identify the physical port provided in the packet relay device  20 . Further, the wireless AP name to be registered in the wireless AP name  503  may be any information as long as it can identify a new wireless AP  10  installed for replacement. The setting information to be registered in the setting information  504  may be arbitrary setting information. 
       FIG. 6  is a sequence diagram of processing to be performed in the network system when the wireless AP  10  according to the first embodiment of the present invention is replaced with a new one. 
     When the new wireless AP  10  is connected to the packet relay device  20 , the DHCP client processing section  140  of the wireless AP  10  transmits, in a broadcast manner, DHCP Discover so as to acquire an IP address from the DHCP server  40  ( 601 ). This allows the DHCP client processing section  140  to transmit the DHCP Discover over the network in the same segment. The DHCP Discover transmitted from the wireless AP  10  is transmitted to the network  50  through the packet relay device  20 . 
     When receiving the DHCP Discover transmitted in step  601 , the DHCP server  40  transmits, to the DHCP client, DHCP Offer including an IP address that the DHCP client (wireless AP  10 ) can use (602). The DHCP client is a device to which the DHCP Discover is transmitted and refers to, in the present embodiment, the new wireless AP  10 . 
     When the IP address included in the DHCP Offer received by the wireless AP  10  as the DHCP client is appropriate, the wireless AP information adding section  141  adds the wireless AP identification information to a DHCP request (address acquisition request) which is a request for acquiring the IP address set in the wireless AP  10 , and the DHCP client processing section  140  transmits the DHCP request including the wireless AP identification information ( 603 ). Although details will be described using  FIG. 7 , the wireless AP identification information is stored in Options of the DHCP request. 
     When the DHCP request transmitted in step  603  is received by the packet relay device  20 , the DHCP processing section  221  of the packet relay device  20  identifies the physical port through which the DHCP request is received and stores the identification information of the identified physical port and then transmits the DHCP request to the network  50  ( 604 ). 
     When receiving the DHCP request transmitted in step  604 , the DHCP server  40  transmits DHCP ACK (address acquisition reply) corresponding to the received DHCP request ( 605 ). The DHCP ACK includes the IP address of the DHCP client. 
     When the DHCP ACK transmitted in step  605  is received by the packet relay device  20 , the DHCP processing section  221  of the packet relay device  20  adds, to the received DHCP ACK, the wireless AP name corresponding to the identification information of the physical port through which the DHCP request corresponding to the received DHCP ACK is received and IP address of the management server  30  and transmits the DHCP ACK including the wireless AP name and IP address of the management server  30  to the wireless AP  10  ( 606 ). The wireless AP name corresponding to the identification information of the physical port through which the DHCP request corresponding to the received DHCP ACK is received is identified by the wireless AP management section  222  referring to the wireless AP registration table  232 , and the IP address of the management server  30  is identified by the management server IP processing section  223  referring to the management server IP registration table  231 . Although details will be described using  FIG. 7 , the wireless AP name and IP address of the management server  30  are stored in Options of the DHCP ACK. 
     When the DHCP ACK transmitted in step  606  is received by the wireless AP  10 , the device IP address management section  130  of the wireless AP  10  stores the IP address of the wireless AP  10  included in the received DHCP ACK, and the management server information processing section  150  registers the IP address of the management server  30  included in the received DHCP ACK in the management server IP registration table  151 . 
     Then, the management server inquiry section  152  of the wireless AP  10  transmits the setting information acquisition request including the stored wireless AP name with the IP address of the management server  30  registered in the management server IP registration table  151  set as a destination ( 607 ). 
     When the setting information acquisition request transmitted in step  607  is received by the management server  30 , the setting information management section  322  of the management server  30  refers to the setting information management table  331  and identifies setting information corresponding to the wireless AP name included in the received setting information acquisition request, and the setting information transmission section  323  transmits the identified setting information to the wireless AP  10  ( 608 ). 
     Specifically, the setting information management section  322  refers to the setting information management table  331  and identifies setting information registered in the setting information  504  in the record in which the wireless AP name included in the received setting information acquisition request is registered in the wireless AP name  503 . Alternatively, the setting information management section  322  may identify, by referring to the refers to the setting information management table  331 , setting information registered in the setting information  504  in the record in which the identification information of the packet relay device  20  as a transmission source of the setting information acquisition request is registered in the packet relay device identification information  501  and in which the wireless AP name included in the received setting information acquisition request is registered in the wireless AP name  503 . 
     When the setting information transmitted in step  608  is received by the wireless AP  10 , the configuration information setting section  160  of the wireless AP  10  executes various settings based on the received setting information. 
       FIG. 7  is a format diagram of the DHCP packet according to the first embodiment of the present invention. 
     The DHCP packet includes the DHCP Discover, DHCP Offer, DHCP request, and DHCP ACK to be exchanged between the wireless AP  10  and DHCP server  40 . 
     The format of the DHCP packet is defined as illustrated in  FIG. 7 . Information unique to the present embodiment is stored in an undefined area of Options of the DHCP packet, and the resultant DHCP packet is transmitted. The information unique to the present embodiment includes, e.g., the wireless AP identification information to be added to the DHCP request to be transmitted in step  603 , wireless AP name and IP address of the management server  30  to be added to the DHCP ACK to be transmitted in step  606 , and the like. 
       FIG. 8  is a flowchart of packet transfer processing to be executed by the packet relay device  20  according to the first embodiment of the present invention. 
     The packet transfer processing is executed when the packet relay device  20  receives a packet. 
     When the packet relay device  20  receives a packet, the DHCP packet determination section  211  determines whether or not the received packet is a DHCP request ( 801 ). 
     When it is determined in step  801  that the received packet is the DHCP request, the DHCP processing section  221  refers to not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP Snooping processing section  2210  is set valid ( 802 ). 
     When it is determined in step  802  that the DHCP Snooping processing section  2210  is set valid, the reception port confirmation section  2211  of the DHCP Snooping processing section  2210  identifies, based on the received DHCP request, the physical port through which the DHCP request is received and associates the identification information of the identified physical port and Transaction ID of the DHCP request with each other for storage in the memory  230  ( 803 ). 
     The packet processing section  210  transmits the received DHCP request to the network  50  ( 804 ), and this routine is ended. 
     On the other hand, when it is determined in step  802  that the DHCP Snooping processing section  2210  is set invalid, the flow proceeds to step  804 , where the packet processing section  210  transmits the received request to the network  50 , and this routine is ended. 
     When it is determined in step  801  that the received packet is not the DHCP request, the DHCP packet determination section  211  determines whether or not the received packet is the DHCP ACK ( 805 ). 
     When it is determined in step  805  that the received packet is the DHCP ACK, the DHCP processing section  221  refers to the not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP Snooping processing section  2210  is set valid ( 806 ). 
     When it is determined in step  806  that the DHCP Snooping processing section  2210  is set valid, the reception port confirmation section  2211  of the DHCP Snooping processing section  2210  acquires the Transaction ID of the DHCP ACK and identifies the identification information of the physical port associated with the acquired Transaction ID ( 807 ). The identification information of the physical port identified in step  807  is the identification information of the physical port through which the DHCP request corresponding to the received DHCP ACK is received. 
     Then, the wireless AP determination section  2212  of the DHCP processing section  221  determines whether or not the DHCP client of the received DHCP ACK is the wireless AP  10  ( 808 ). Specifically, the wireless AP determination section  2212  determines that the DHCP client of the received DHCP ACK is the wireless AP  10  when the wireless AP identification information is stored in the Options of the received DHCP ACK. 
     When it is determined in step  808  that the DHCP client of the received DHCP ACK is the wireless AP  10 , the DHCP data adding section  2213  of the DHCP Snooping processing section  2210  adds, to the Options of the DHCP ACK, the wireless AP name corresponding to the physical port identified in step  807  and IP address of the management server  30  ( 809 ). 
     Specifically, the wireless AP management section  222  acquires, from the records of the wireless AP registration table  232 , the wireless AP name registered in the wireless AP name  302  in the record in which the identification information of the physical port that the reception port confirmation section  2211  identifies in step  807  is registered in the physical port identification information  301 . Further, the management server IP processing section  223  refers to the management server IP registration table  231  and acquires the IP address of the management server  30 . Then, the DHCP data adding section  2213  adds, to the DHCP ACK, the wireless AP name acquired by the wireless AP management section  222  and IP address of the management server  30  acquired by the management server IP processing section  223 . 
     Then, the packet processing section  210  transmits, to the wireless AP  10 , the DHCP ACK to which the wireless AP name and IP address of the management server  30  are added in step  809  ( 810 ), and this routine is ended. 
     When it is determined in step  806  that the DHCP Snooping processing section  2210  is set invalid, and when it is determined in step  808  that the DHCP client of the received DHCP ACK is not the wireless AP  10 , the flow proceeds to step  810 , where the packet processing section  210  transmits the DHCP ACK to the DHCP client, and this routine is ended. 
     When it is determined in step  805  that the received packet is not the DHCP ACK, the packet processing section  210  transmits the received packet in step  810 , and this routine is ended. 
     As described above, according to the present embodiment, when the wireless AP  10  is replaced with a new wireless AP  10 , the packet relay device  20  transmits, to the new wireless AP  10 , the DHCP ACK corresponding to the DHCP request transmitted from the new wireless AP  10 , including therein the wireless AP name of the new wireless AP  10  and IP address of the management server  30 . Thus, even when the wireless AP  10  is replaced with a new wireless AP  10 , it is possible to acquire the setting information of the new wireless AP  10  from the management server  30  only by connecting the new wireless AP  10  to the packet relay device  20 , thereby allowing initial setting of the new wireless AP  10  to be automatically performed without manual intervention. 
     Further, it is not necessary to make special settings for the DHCP server  40 , allowing the network system of the present embodiment to be easily incorporated in the existing network. 
     Second Embodiment 
     A second embodiment of the present invention will be described with reference to  FIGS. 9 to 13 . 
     In the first embodiment, the packet relay device  20  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK; while in the second embodiment, the DHCP server  40  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK. 
     The management server IP registration table  231  and wireless AP registration table  232 , which are stored in the memory  230  of the packet relay device  20  in the network system of the first embodiment, are stored in a memory  430  (see  FIG. 10 ) of the DHCP server  40  in a network system of the second embodiment. Thus, the packet relay device  20  of the present embodiment does not include the wireless AP management section  222  and management server IP processing section  223 . Further, the DHCP processing section  221  of the packet relay device  20  and DHCP server  40  differ from those of the first embodiment, so the DHCP processing section  221  of the packet relay device  20  and DHCP server  40  of the present embodiment will be described with reference to  FIG. 9  and  FIG. 10 , respectively. The wireless AP  10  and management server  30  of the present embodiment are the same as those of the first embodiment, so descriptions thereof will be omitted. 
       FIG. 9  is an explanatory view of a DHCP processing section  221  provided in the packet relay device  20  according to the second embodiment of the present invention. 
     The DHCP processing section  221  includes a DHCP Snooping processing section  2210 , a DHCP relay processing section  2220 , and a DHCP server processing section  2230 . 
     The DHCP Snooping processing section  2210  differs from the DHCP Snooping processing section  2210  of the first embodiment and does not include the reception port confirmation section  2211 , wireless AP determination section  2212 , and DHCP data adding section  2213 . 
     The DHCP relay processing section  2220  includes a DHCP data deleting section  2221 . The DHCP data deleting section  2221  deletes, before transmission of the DHCP Offer and DHCP ACK, Option  82  information that the packet relay device  20  embeds in the DHCP Discover and DHCP request. The Option  82  information is information for the packet relay device  20  to notify the DHCP server  40  of the physical port through which the DHCP Discover and DHCP request from the DHCP client is received. 
     The DHCP server processing section  2230  is the same as that of the first embodiment, so descriptions thereof will be omitted. 
     In the second embodiment, a function of the DHCP Snooping processing section  2210  for identifying the physical port through which the DHCP packet from the DHCP client is received and a function of the DHCP relay processing section  2220  are set valid. 
       FIG. 10  is an explanatory view of the DHCP server  40  according to the second embodiment. 
     The DHCP server  40  includes a packet transmission/reception section  410 , a processor  420 , a memory  430 , and a physical port  440 . The packet transmission/reception section  410 , processor  420 , memory  430 , and physical port  440  are connected to each other through a bus  441 . 
     The packet transmission/reception section  410  executes packet transmission/reception processing performed by the DHCP server  40 . 
     The processor  420  executes various programs and includes a DHCP processing section  421 , a wireless AP management section  422 , and a management server IP processing section  423 . 
     The DHCP processing section  421  executes processing of distributing an IP address to the DHCP client. The DHCP processing section  421  includes a reception port confirmation section  4211 , a wireless AP determination section  4212 , and a DHCP data adding section  4213 . 
     The reception port confirmation section  4211  identifies the physical port through which the packet relay device  20  receives the DHCP packet from the DHCP client in the same manner as the reception port confirmation section  2211  of the first embodiment. The wireless AP determination section  4212  refers to the DHCP packet and determines whether or not the DHCP client of the DHCP packet is the wireless AP  10  in the same manner as the wireless AP determination section  2212  of the first embodiment. The DHCP data adding section  4213  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK in the same manner as the DHCP data adding section  2213  of the first embodiment. 
     The wireless AP management section  422  and management server IP processing section  423  are the same as the wireless AP management section  222  of the first embodiment and management server IP processing section  223  of the first embodiment, respectively, so descriptions thereof will be omitted. 
     The memory  430  is a storage area for storing various programs that the processor  420  executes and data that the processor  420  reads therefrom or writes thereto. The memory  430  stores a management server IP registration table  431  and a wireless AP registration table  432 . The management server IP registration table  431  and wireless AP registration table  432  are same as the management server IP registration table  231  of the first embodiment and wireless AP registration table  232  of the first embodiment, respectively, so descriptions thereof will be omitted. 
       FIG. 11  is a sequence diagram of processing to be performed in the network system when the wireless AP  10  according to the second embodiment of the present invention is replaced with a new one. In  FIG. 11 , the same reference numerals are given to the same processing as those in  FIG. 6  of the first embodiment, and descriptions thereof will be omitted. 
     When receiving the DHCP request transmitted from the wireless AP  10  in step  603 , the packet relay device  20  uses a function of Option  82  of the DHCP relay processing section  2220  to add, to the DHCP request, the Option  82  information including an MAC address thereof and identification information of the physical port through which the DHCP request is received and transmits the resultant DHCP request to the network  50  ( 1101 ). 
     When the DHCP request is received by the DHCP server  40 , the DHCP processing section  421  of the DHCP server  40  refers to the Option  82  included in the received DHCP request and identifies the physical port through which the packet relay device  20  receives the DHCP request. Then, the wireless AP management section  422  refers to the wireless AP registration table  432  and acquires the wireless AP name corresponding to the identification information of the identified physical port, and the management server IP processing section  423  refers to the management server IP registration table  431  and acquires the IP address of the management server  30 . Then, the DHCP processing section  421  transmits the DHCP ACK including the acquired wireless AP name and acquired IP address of the management server  30  ( 1102 ). 
     When the DHCP ACK transmitted in step  1102  is received by the packet relay device  20 , the DHCP data deleting section  2221  provided in the DHCP relay processing section  2220  of the DHCP processing section  221  deletes the Option  82  information of the received DHCP ACK and transmits the resultant DHCP ACK to the wireless AP  10  ( 1103 ). 
     In the manner as described above, the DHCP server  40  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK and transmits the resultant DHCP ACK. The packet relay device  20  only needs to validate the function of the Option  82 , and it is not necessary to make special settings for the packet relay device  20 . This allows the network system of the present embodiment to be easily incorporated in the existing network. 
       FIG. 12  is a flowchart of packet transfer processing to be executed by the packet relay device  20  according to the second embodiment of the present invention. In  FIG. 12 , the same reference numerals are given to the same processing as those in  FIG. 8  of the first embodiment, and descriptions thereof will be omitted. 
     When it is determined in step  801  that the received packet is the DHCP request, the DHCP processing section  221  refers to not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP relay processing section  2220  is set valid ( 1201 ). 
     When it is determined in step  1201  that the DHCP relay processing section  2220  is set valid, the DHCP relay processing section  2220  uses the function of the Option  82  to add, to the received DHCP request, the Option  82  information including the identification information of the physical port (physical port connected to the DHCP client) through which the packet relay device  20  receives the DHCP request and MAC address of the packet relay device  20  ( 1202 ), and the flow proceeds to step  804 . In step  804 , the packet processing section  210  transmits the DHCP request including the Option  82  information to the network  50 . 
     On the other hand, when it is determined in step  1201  that the DHCP relay processing section  2220  is set invalid, the flow proceeds to step  804 , where the packet processing section  210  transmits the received request to the network  50 . 
     When it is determined in step  805  that the received packet is the DHCP ACK, the DHCP processing section  221  refers to the not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP relay processing section  2220  is set valid ( 1203 ). 
     When it is determined in step  1203  that the DHCP relay processing section  2220  is set valid, the DHCP data deleting section  2221  of the DHCP relay processing section  2220  deletes the Option  82  information of the received DHCP ACK ( 1204 ), and the flow proceeds to step  810 . In step  810 , the packet processing section  210  transmits the received DHCP ACK to the wireless AP  10 . 
     On the other hand, when it is determined in step  1203  that the DHCP relay processing section  2220  is set invalid, the flow proceeds to step  810 , where the packet processing section  210  transmits the received DHCP ACK to the wireless AP  10 . 
     Thus, when receiving the DHCP request, the packet relay device  20  can notify the DHCP server  40  of the identification information of the physical port through which the DHCP request is received and can delete the Option  82  information of the DHCP ACK received from the DHCP server  40 . 
       FIG. 13  is a flowchart of packet transfer processing to be executed by the DHCP server  40  according to the second embodiment of the present invention. 
     The packet transfer processing is executed when the DHCP server  40  receives a packet. 
     When the DHCP server  40  receives a packet, the packet transmission/reception section  410  determines whether or not the received packet is the DHCP request ( 1301 ). 
     When it is determined in step  1301  that the received packet is the DHCP request, the reception port confirmation section  4211  of the DHCP processing section  421  identifies the physical port of the packet relay device  20  through which the DHCP request is received based on the Option  82  information of the received DHCP request ( 1302 ). 
     Then, the wireless AP determination section  4212  of the DHCP processing section  421  determines whether or not the DHCP client of the received DHCP request is the wireless AP  10  ( 1303 ). A determination method of step  1303  is the same as that of step  808  of  FIG. 8 , so descriptions thereof will be omitted. 
     When it is determined in step  1303  that the DHCP client of received DHCP request is the wireless AP  10 , the DHCP data adding section  4213  of the DHCP processing section  421  adds, to the Options of the DHCP ACK, the acquired wireless AP name corresponding to the physical port identified in step  1302  and IP address of the management server  30  ( 1304 ). 
     Specifically, the wireless AP management section  422  acquires, from the records of the wireless AP registration table  432 , the wireless AP name registered in the wireless AP name  302  in the record in which the identification information of the physical port that the reception port confirmation section  4211  identifies in step  1302  is registered in the physical port identification information  301 . Further, the management server IP processing section  423  refers to the management server IP registration table  431  and acquires the IP address of the management server  30 . Then, the DHCP data adding section  4213  adds, to the DHCP ACK, the wireless AP name acquired by the wireless AP management section  422  and IP address of the management server  30  acquired by the management server IP processing section  423 . 
     Then, the packet transmission/reception section  410  transmits the DHCP ACK to the network  50  ( 1305 ), and this routine is ended. 
     On the other hand, when it is determined in step  1303  that the DHCP client of the received DHCP request is not the wireless AP  10 , the flow proceeds to step  1305 , where the packet transmission/reception section  410  transmits the DHCP ACK, and this routine is ended. 
     When it is determined in step  1301  that the received packet is not the DHCP request, the packet transmission/reception section  410  determines whether or not the received packet is the DHCP Discover ( 1306 ). 
     When it is determined in step  1306  that the received packet is the DHCP Discover, the DHCP processing section  421  identifies the IP address that the DHCP client that has transmitted the DHCP Discover can use, and the packet transmission/reception section  410  transmits the DHCP Offer including the identified IP address ( 1307 ), and this routine is ended. 
     On the other hand, when it is determined in step  1306  that the received packet is not the DHCP Discover, which means that the received packet is the DHCP packet but a normal packet, so the packet transmission/reception section  410  transfers the received packet ( 1308 ), and this routine is ended. 
     As described above, according to the present embodiment, when the wireless AP  10  is replaced with a new wireless AP  10 , the DHCP server  40  transmits, to the new wireless AP  10 , the DHCP ACK corresponding to the DHCP request transmitted from the new wireless AP  10 , including therein the wireless AP name of the new wireless AP  10  and IP address of the management server  30 . Thus, even when the wireless AP  10  is replaced with a new wireless AP  10 , it is possible to acquire the setting information of the new wireless AP  10  from the management server  30  only by connecting the new wireless AP  10  to the packet relay device  20 , thereby allowing initial setting of the new wireless AP  10  to be automatically performed without manual intervention. 
     Further, it is not necessary to make special settings for the packet relay device  20 , allowing the network system of the present embodiment to be easily incorporated in the existing network. 
     Third Embodiment 
     A third embodiment of the present invention will be described with reference to  FIGS. 14 to 16 . 
     In the present embodiment, the function of the DHCP server  40  is implemented in the packet relay device  20 , and the packet relay device  20  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK and transmits the resultant DHCP ACK to the wireless AP  10 . 
     Since the function of the DHCP server  40  is implemented in the packet relay device  20 , a network system of the present embodiment need not be provided with the DHCP server  40 . Accordingly, in the present embodiment, the DHCP processing section  221  of the packet relay device  20  differs from that of the first embodiment. Hereinafter, a configuration of the DHCP processing section  221  according to the present embodiment will be described with reference to  FIG. 14 . 
       FIG. 14  is an explanatory view of the DHCP processing section  221  according to the third embodiment of the present invention. 
     The DHCP processing section  221  includes a DHCP Snooping processing section  2210 , a DHCP relay processing section  2220 , and a DHCP server processing section  2230 . 
     The DHCP Snooping processing section  2210  differs from the DHCP Snooping processing section  2210  of the first embodiment and does not include the reception port confirmation section  2211 , wireless AP determination section  2212 , and DHCP data adding section  2213 . 
     The DHCP relay processing section  2220  is the same as the DHCP relay processing section  2220  of the first embodiment, so descriptions thereof will be omitted. 
     The DHCP server processing section  2230  differs from that of the first embodiment and includes a reception port confirmation section  2231 , a wireless AP determination section  2232 , a DHCP data adding section  2233 , and an IP address distribution section  2234 . 
     The reception port confirmation section  2231  identifies the physical port through which the packet relay device  20  receives the DHCP packet from the DHCP client in the same manner as the reception port confirmation section  2211  of the first embodiment. The wireless AP determination section  2232  refers to the DHCP packet and determines whether or not the DHCP client of the DHCP packet is the wireless AP  10  in the same manner as the wireless AP determination section  2212  of the first embodiment. The DHCP data adding section  2233  adds the wireless AP name and IP address of the management server  30  to the DHCP ACK in the same manner as the DHCP data adding section  2213  of the first embodiment. 
     The IP address distribution section  2234  manages and determines the IP address to be distributed to the DHCP client. 
     In the present embodiment, the function of the DHCP server processing section  2230  is set valid. 
       FIG. 15  is a sequence diagram of processing to be performed in the network system when the wireless AP  10  according to the third embodiment of the present invention is replaced with a new one. In  FIG. 15 , the same reference numerals are given to the same processing as those in FIG.  6  of the first embodiment, and descriptions thereof will be omitted. 
     When the DHCP Discover transmitted from the wireless AP  10  is received by the packet relay device  20  in step  601 , the DHCP server processing section  2230  provided in the DHCP processing section  221  of the packet relay device  20  transmits the DHCP Offer to the wireless AP  10  ( 1501 ). 
     When the DHCP request transmitted from the wireless AP  10  is received by the packet relay device  20  in step  603 , the DHCP server processing section  2230  of the packet relay device  20  identifies the physical port through which the DHCP request is received and determines the IP address to be distributed to the DHCP client. Further, since the DHCP client of the received DHCP request is the wireless AP  10 , the DHCP server processing section  2230  transmits the DHCP ACK including the wireless AP name corresponding to the identification information of the identified physical port, IP address of the management server  30 , and IP address to be distributed ( 1502 ). 
     Thus, even when the wireless AP  10  is replaced with a new wireless AP  10  in the configuration in which the function of the DHCP server  40  is implemented in the packet relay device  20 , it is possible to acquire the setting information of the new wireless AP  10  from the management server  30  only by connecting the new wireless AP  10  to the packet relay device  20 . 
       FIG. 16  is a flowchart of packet transfer processing to be executed by the packet relay device  20  according to the third embodiment of the present invention. In  FIG. 16 , the same reference numerals are given to the same processing as those in  FIG. 8  of the first embodiment, and descriptions thereof will be omitted. 
     When it is determined in step  801  that the received packet is the DHCP request, the DHCP processing section  221  refers to the not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP server processing section  2230  is set valid ( 1601 ). 
     When it is determined in step  1601  that the DHCP server processing section  2230  is set valid, the reception port confirmation section  2231  of the DHCP server processing section  2230  identifies, based on the received DHCP request, the physical port through which the DHCP request is received ( 1602 ). 
     Then, the wireless AP determination section  2232  of the DHCP server processing section  2230  determines whether or not the DHCP client of the received DHCP request is the wireless AP  10  ( 1603 ). 
     When it is determined in step  1603  that the DHCP client of the received DHCP request is the wireless AP  10 , the DHCP data adding section  2233  of the DHCP server processing section  2230  adds, to the DHCP ACK, the wireless AP name corresponding to the physical port identified in step  1602  and IP address of the management server  30  ( 1604 ). The processing in step  1604  is the same as that in step  809  of  FIG. 8 , so descriptions thereof will be omitted. 
     Then, the IP address distribution section  2234  determines the IP address to be distributed to the wireless AP  10  which is the DHCP client, the DHCP data adding section  2233  adds the IP address determined by the IP address distribution section  2234  to the DHCP ACK, and the packet processing section  210  transmits the resultant DHCP ACK to the wireless AP  10  ( 1605 ), and this routine is ended. 
     On the other hand, when it is determined in step  1603  that the DHCP client of the received DHCP request is not the wireless AP  10 , the flow proceeds to step  1605 , where the IP address distribution section  2234  determines the IP address to be distributed to the DHCP client, the DHCP data adding section  2233  adds the IP address determined by the IP address distribution section  2234  to the DHCP ACK, and the packet processing section  210  transmits the resultant DHCP ACK to the DHCP client, and this routine is ended. 
     When it is determined in step  1601  that the DHCP server processing section  2230  is set invalid, the packet processing section  210  transmits the received DHCP request to an external DHCP server  40  ( 1606 ), and this routine is ended. 
     When it is determined in step  801  that the received packet is not the DHCP request, the DHCP packet determination section  211  determines whether or not the received packet is the DHCP Discover ( 1607 ). 
     When it is determined in step  1607  that the received packet is the DHCP Discover, the DHCP processing section  221  refers to the not illustrated processing section setting information stored in the memory  230  and determines whether or not the DHCP server processing section  2230  is set valid ( 1608 ). 
     When it is determined in step  1608  that the DHCP server processing section  2230  is set valid, the DHCP processing section  221  identifies the IP address that the DHCP client that has transmitted the DHCP Discover can use, and the packet processing section  210  transmits the DHCP Offer including the identified IP address ( 1609 ), and this routine is ended. 
     On the other hand, when it is determined in step  1608  that the DHCP server processing section  2230  is set invalid, the packet processing section  210  transmits the received DHCP Discover to the external DHCP server  40  ( 1610 ), and this routine is ended. 
     When it is determined in step  1607  that the received packet is not the DHCP Discover, which means that the received packet is not the DHCP packet but a normal packet, so the packet processing section  210  transfers the received packet ( 1611 ), and this routine is ended. 
     As described above, according to the present embodiment, when the wireless AP  10  is replaced with a new wireless AP  10 , the packet relay device  20  in which the function of the DHCP server  40  is implemented transmits, to the new wireless AP  10 , the DHCP ACK corresponding to the DHCP request transmitted from the new wireless AP  10 , including therein the wireless AP name of the new wireless AP  10  and IP address of the management server  30 . Thus, even when the wireless AP  10  is replaced with a new wireless AP  10 , it is possible to acquire the setting information of the new wireless AP  10  from the management server  30  only by connecting the new wireless AP  10  to the packet relay device  20 , thereby allowing initial setting of the new wireless AP  10  to be automatically performed without manual intervention. 
     In the above first to third embodiments, the wireless AP  10  is used as an example of a node for acquiring the setting information; however, the node for acquiring the setting information is not limited to the wireless AP  10 . For example, the node may be a monitoring camera. In this case, the setting information to be stored in the management server  30  includes, e.g., a resolution of the monitoring camera, an imaging thereof, and the like. 
     Further, in the above first to third embodiments, the IP address is distributed to the node by using the DHCP; however, the IP address may be distributed using any other protocols. 
     Further, the network system according to the present invention is not limited to that illustrated in  FIG. 1  but may have any configuration. The number of the packet relay devices  20 , number of lines for connecting the devices, etc., may be arbitrarily selected. Further, a path for exchanging data among the devices may be arbitrarily constructed. 
     The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above embodiments are detailed to make the present invention easily understood and are not limited to an embodiment having all the explained constitutions. Part of the constitution of a certain embodiment may be substituted by the constitution of another embodiment, and the constitution of another embodiment may be added to the constitution of a certain embodiment. The addition, deletion or substitution of another constitution may be carried out on part of the constitution of an embodiment. 
     In addition, each configuration, function, processing section, processing means, and the like in the above embodiments may be realized in hardware, for example, by designing some or all of them using integrated circuits. Further, each configuration, function, and the like may be realized in software by a processor analyzing and executing a program for realizing each function. Information such as a program, a table, or a file for realizing each function may be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.