PATENT DOCUMENT

Abstract:
A route setting device includes: a storage in which routing information is stored; and a processor configured to execute a procedure, the procedure including: selecting a network device among a plurality of network devices forming a network over which a signal including transmission source information and destination information is transmitted, the network device changing at least one of the transmission source information and the destination information included in the signal; categorizing the network device based on a type of the changed information; and generating the routing information according to a result of the categorizing, wherein the route setting device sets the generated routing information to the network device.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-114818, filed on Jun. 3, 2014, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a route setting device and a route setting method. 
     BACKGROUND 
     With an increase in communication demand, the number of network devices that are connected to one network is increased, and a network configuration is complicated. For example, because each router within the network individually controls a route over which a packet is transferred, a packet route is difficult to flexibly configure over the network as a whole. 
     In contrast, in a network to which a software defined network technology (SDN) is applied, because a function of controlling each network devices is integrated into one piece of software, it is possible to flexibly configure a route. For example, in an open flow network (OFN), a function of controlling a packet route is separated from a relay device for the packet, and is integrated into a single network management server. It is possible for the network management server to flexibly configure the packet route over the whole network by setting the routing information indicating the transmission source of the packet to each relay device. 
     The network management server can set the routing information to a server equipped with various functions as well as the relay device within the network. The routing information, for example, is generated based on a destination address or a source address within a header of the packet. 
     For example, with regard to transfer of the packet, Japanese Laid-open Patent Publication No. 2001-352337 discloses that when the packet is relayed over different domains, the source address or the destination address of the packet is changed. 
     SUMMARY 
     According to an aspect of the invention, a route setting device includes: a storage in which routing information is stored; and a processor configured to execute a procedure, the procedure including: selecting a network device among a plurality of network devices forming a network over which a signal including transmission source information and destination information is transmitted, the network device changing at least one of the transmission source information and the destination information included in the signal; categorizing the network device based on a type of the changed information; and generating the routing information according to a result of the categorizing, wherein the route setting device sets the generated routing information to the network device. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram illustrating one example of a network including relay devices; 
         FIG. 2  is a configuration diagram illustrating one example of a network including the relay devices and servers; 
         FIG. 3  is a configuration diagram illustrating another example of the network including the relay devices and the servers; 
         FIG. 4  is a diagram illustrating one example of routing information that is set to in the relay devices; 
         FIGS. 5A to 5D  are diagrams illustrating categorization of the servers; 
         FIG. 6  is a configuration diagram illustrating one example of a network management server; 
         FIG. 7  is a configuration diagram illustrating one example of the servers within the network; 
         FIG. 8  is a configuration diagram illustrating one example of the relay devices; 
         FIG. 9  is a configuration diagram illustrating one example of the network for which the routing information is set; 
         FIG. 10  is a diagram illustrating a situation in which a destination address and a source address are changed on a packet route; 
         FIG. 11  is a flowchart illustrating processing that generates the routing information according to a first embodiment; 
         FIG. 12  is a diagram illustrating an example of generating the routing information according to the first embodiment; 
         FIG. 13  is a flowchart illustrating processing that generates the routing information according to a second embodiment; 
         FIG. 14  is a diagram illustrating an example of generating the routing information according to the second embodiment; 
         FIGS. 15A and 15B  are flowcharts illustrating processing that generates the routing information according to a third embodiment; 
         FIG. 16  is a diagram illustrating an example of generating the routing information according to the third embodiment; 
         FIG. 17  is a diagram illustrating another example of generating the routing information according to the third embodiment; 
         FIGS. 18A and 18B  are flowcharts illustrating processing that generates the routing information according to a fourth embodiment; and 
         FIG. 19  is a diagram illustrating an example of generating the routing information according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In a case where, for example, like a proxy server, a server that changes a destination address and/or source address of a packet that passes through the server is included in a network, the changed destination address and/or source address is not consistent with routing information of a network device on a route for the packet. In this case, the packet is not normally transferred over a given route and does not reach a desired destination terminal device. 
     A technology that sets suitable routing information to a network device on a signal route is described. 
       FIG. 1  is a configuration diagram illustrating one example of a network including relay devices. A network NW includes multiple relay devices (# 1  to # 7 )  2  that transfer a packet PKT as a signal. As the relay devices (# 1  to # 7 )  2 , routers are given as examples, but are not limited to these. For example, layer  2  switches may be instead used. 
     The relay devices  2  includes interfaces IFn (n:  1  to  4 ) in all paths corresponding to transfer destinations. The relay devices  2  are connected to other devices through the interfaces IFn. 
     In the present example, the relay devices (# 1  to # 4 )  2  are connected in series to one another. The relay device (# 5 )  2  is connected to the relay device (# 1 )  2  and the relay device (# 2 )  2 , and the relay device (# 6 )  2  is connected to the relay device (# 2 )  2  and the relay device (# 3 )  2 . The relay device (# 7 )  2  is connected to the relay device (# 3 )  2  and the relay device (# 4 )  2 . Furthermore, the relay device (# 1 )  2  and the relay device (# 4 )  2  are connected to a transmission source terminal device  3  and a destination terminal device  4 , respectively. 
     The transmission source terminal device  3  transmits a packet to the destination terminal device  4  through the network NW. That is, the transmission source terminal device  3  is a transmission source of the packet PKT, and the destination terminal device  4  is a destination of the packet PKT. As the transmission source terminal device  3  and the destination terminal device  4 , a personal computer and a smartphone are given as examples, but are not limited to these. 
     A header that is control information, and data are included in the packet PKT. A destination address (destination information) and a source address (transmission source information) are included in the header. The destination address and the source address indicate a destination and transmission source of a packet, respectively. When addresses of the transmission source terminal device  3  and the destination terminal device  4  are set to be “A” and “Z”, respectively, a destination address and a source address within the packet PKT indicate “A” and “Z”, respectively. Moreover, the present example of a signal that is transferred to the network NW is a packet, but the signal is not limited to this. 
     A network management server  1  as a route setting device sets packet routing information to each relay device  2  within the network NW, which is network device, based on the SDN technology, for example. The routing information indicates the destination to which the relay devices  2  transfer the packet PKT, based on at least one of the destination address and source address of the packet PKT. The network management server  1  configures a route R 1  for the packet PKT within the network NW, which, in some cases, is called a service chain, by setting the routing information. The packet PKT that is transferred along the route R 1  passes through the relay devices (# 1 , # 5 , # 2 , # 3 , # 7 , and # 4 )  2  in this sequence. 
     In  FIG. 1 , as one example, routing information K 1  that is set to the relay device (# 5 )  2  and routing information K 2  that is set to the relay device (# 3 )  2  are illustrated. The routing information K 1  and the routing information K 2  each include a “destination address”, an “output interface (IF)”, a “NEXT HOP”. 
     The “destination address” indicates a destination address of the transfer target packet PKT. The “output interface” indicates an interface that outputs the packet PKT. The “NEXT HOP” indicates the transfer destination of the packet PKT on the route R 1 . Moreover, in  FIG. 1 , the “NEXT HOP” may be expressed as a device name, but, for example, may be expressed as an Internet Protocol (IP) of the relay device  2 . 
     For example, the “destination address”, the “output interface”, and the “NEXT HOP” in the routing information K 1  for the relay device (# 5 )  2  indicate “Z”, “IF 2 ”, and the “relay device (# 2 )”, respectively. For this reason, the relay device (# 5 )  2  transfers the packet PKT of which the destination address is “Z” to the relay device (# 2 )  2  through an interface IF 2 . 
     Furthermore, the “destination address”, the “output interface”, and the “NEXT HOP” in the routing information K 2  for the relay device (# 3 )  2  indicate “Z”, “IF 3 ”, and “relay device (# 7 )”, respectively. For this reason, the relay device (# 3 )  2  transfers the packet PKT of which the destination address is “Z” to the relay device (# 7 )  2  through an interface IF 3 . Moreover, in the same manner, the routing information in which the “destination address” indicates “Z” is also set to the other relay devices  2 . 
     In this manner, the network management server  1  sets the routing information that is based on the destination address “Z” that is common to the relay devices  2  on the route R 1 . Accordingly, the packet PKT is transferred from the transmission source terminal device  3  to the destination terminal device  4  along the route R 1 . Therefore, the network management server  1  can flexibly configure the route R 1  for the packet PKT over the entire network NW with the SDN technology. 
     The network management server  1  can set the routing information to a server equipped with various functions, as well as the relay devices  2 . In  FIG. 2 , one example of the network NW including the relay devices  2  and servers  5   a  and  5   b . In  FIG. 2 , constituent elements that are the same as those illustrated in  FIG. 1  are given the same reference numerals and descriptions of them are omitted. 
     On the network NW in the present example, instead of the relay device (# 5 )  2  of  FIG. 1 , the server  5   a  equipped with a deep packet inspection (DPI) function is installed, and instead of the relay device (# 7 )  2  in  FIG. 1 , the server  5   b  equipped with a firewall function is installed. The server  5   a  monitors and analyzes the packet that is transferred over the network NW, specifies a terminal device that is the transmission source or a terminal device that is the transmission destination, specifies an application in which the packet is used, and so on. Furthermore, the server  5   b  monitors packets that pass through the server  5   b , blocks a specific packet or allows a specific packet to pass through. The servers  5   a  and  5   b  transfer the packet PKT through an interface IFm (m:  1 ,  2 ) for every path. 
     The network management server  1  sets the routing information to the relay devices (# 1  to # 4 , and # 6 )  2  and in the servers (the network device)  5   a  and  5   b . Accordingly, the packet PKT is transferred from the transmission source terminal device  3  to the destination terminal device  4  along a route R 2 . The packet PKT that is transferred over the route  2  passes through the relay device (# 1 )  2 , the server  5   a , the relay devices (# 2 , and # 3 )  2 , the server  5   b , and the relay device (# 4 )  2 , in this sequence. 
     In  FIG. 2 , as one example, routing information K 3  that is set to in the server  5   a  and routing information K 4  that is set to the relay device (# 3 )  2  are illustrated. 
     The “destination address” the “output interface”, and the “NEXT HOP” in the routing information K 3  for the server  5   a  indicate “Z”, “IF 2 ”, and “the relay device (# 2 )”. For this reason, the server  5   a  transfers the packet PKT of which the destination address is “Z” to the relay device (# 2 )  2  through the interface IF 2 . 
     Furthermore, the “destination address”, the “output interface”, and the “NEXT HOP” in the routing information K 4  for the relay device (# 3 )  2  indicate “Z”, “IF 3 ”, and “server (firewall)”, respectively. For this reason, the relay device (# 3 )  2  transfers the packet PKT of which the destination address is “Z” to the server  5   b  through the interface IF 3 . Moreover, in the same manner, the routing information in which the “destination address” is “Z” is set to the other relay devices  2  and in the server  5   b.    
     The servers  5   a  and  5   b  do not change the destination address and source address of the packet PKT. For this reason, even though the routing information is set to the relay devices  2  and in the servers  5   a  and  5   b  within the network NW based on the common destination address “Z”, the network management server  1  normally transfers the packet PKT along the route R 2 . 
     However, in a case where, for example, like the proxy server, the server that changes the destination address or the source address of the packet PKT that passes through the server is included in the network NW, the changed destination address and/or source address is not consistent with the routing information of each device on the route for the packet PKT. In this case, the packet PKT is not normally transferred along a given route and does not reach the destination terminal device  4 . 
       FIG. 3  is a configuration diagram illustrating another example of the network NW including the relay devices  2  and the servers  5   a  to  5   c . In  FIG. 3 , constituent elements that are the same as those illustrated in  FIGS. 1 and 2  are given the same reference numerals and descriptions of them are omitted. 
     On the network NW in the present example, instead of the relay device (# 6 )  2  of  FIG. 2 , a server  5   c  equipped with a Web proxy function is installed. Instead of the terminal device, the server  5   c  has access to a Web server for the terminal device. 
     For this reason, based on a Transmission Control Protocol (TCP), the server  5   c  establishes communication sessions SN 1  between the transmission source terminal device  3  and the server  5   c  and SN 2  between the destination terminal device  4  and the server  5   c . Therefore, the server  5   c  transfers the packet received from the communication SN 1  with the transmission source terminal device  3  to the communication session SN 2  with the destination terminal device  4 . 
     At this point, a route from the transmission source terminal device  3 , through the relay devices (# 1  and # 2 )  2 , the server  5   c , the relay device (# 3 )  2 , the server  5   b , and the relay device (# 4 )  2 , to the destination terminal device  4 , in this sequence are assumed to be a route R 3 . In this case, a packet PKT  1  that is transferred from the transmission source terminal device  3  to the server  5   c , a packet PKT  2  that is transferred from the server  5   c  to the destination terminal device  4  are different in the destination address and the source address from each other. 
     In order to be based on the communication session SN 1 , the packet PKT  1  includes the destination address indicating an address “P” of the server  5   c  and the source address indicating an address “A” of the transmission source terminal device  3 . On the other hand, in order to be based on the communication session SN 2 , the packet PKT  2  includes the destination address indicating an address “Z” of the destination address terminal device  4  and the source address indicating an address “P” of the server  5   c.    
     For this reason, the server  5   c  associates the communication sessions SN 1  and SN 2  with each other, and the packet PKT  1  in the communication session SN 1  into the packet PKT  2  in the communication session SN 2 . That is, the server  5   c  changes the destination address of the packet PKT  1  from “P” to “Z”, and changes the source address of the packet PKT  1  from “A” to “P”. 
     Therefore, even though, as in the examples in  FIGS. 1 and 2 , the network management server  1  sets the routing information, which is based on the common destination address “Z”, to the relay devices (# 1  to # 4 )  2  and the servers  5   c  and  5   b  on the route R 3 , the packets PKT  1  and PKT  2  are not normally transferred. 
     Then, the network management server  1  detects the server on the route, which changes the destination address and/or source address of the packet that passes through the server, and categories the detected packets by types of information (the destination address and the source address) that are changed. The network management server  1  sets a suitable route by generating the routing information of each device within the network according to a result of the categorization by the server. 
     In  FIG. 4 , one example of routing information K 5  and routing information K 6  that are set to the relay devices (# 2  and # 3 )  2  on the network NW in  FIG. 3  is illustrated. In  FIG. 4 , constituent elements that are the same as those illustrated in  FIGS. 1 to 3  are given the same reference numerals and descriptions of them are omitted. 
     On the network NW in the present example, in addition to the route R 3  on which the server  5   c  is present, which is described above, a route R 4  on which the server  5   c  is not present is set. The packet PKT that is transferred over the route R 4  from the transmission source terminal device  3  to the destination terminal device  4  passes through the relay device (# 1 )  2 , the server  5   a , the relay devices (# 2 , and # 3 )  2 , the server  5   b , and the relay device (# 4 )  2 , in this sequence. 
     Because the packet PKT that is transferred over the route R 4  does not pass through the server  5   c , a destination address “Z” and a source address “A” thereof are not changed. On the other hand, because the packet PKT  1  that is transferred over the route R 3  passes through the server  5   c , as described above, a destination address “P” and the source address “A” are changed to the destination address “Z” and the source address “P”, respectively. 
     Therefore, the network management server  1  sets an individual routing information K 5  for the packet PKT  1  and the packet PKT on the routes R 3  and R 4 , respectively, to the relay device (# 2 )  2  that is a node adjacent to the server  5   c.    
     The “destination address”, the “output interface”, and the “NEXT HOP” in the routing information K 5  for the packet PKT on the route R 4  indicate “Z”, “IF 4 ”, and the “relay device (# 3 )”, respectively. For this reason, the relay device (# 2 )  2  transfers the packet PKT of which the destination address is “Z” to the relay device (# 3 )  2  through an interface IF 4 . 
     Furthermore, the “destination address”, the “output interface”, and the “NEXT HOP” in the routing information K 5  for the packet PKT  1  on the route R 3  indicate “P”, “IF 3 ”, and the “server (Web proxy)”, respectively. For this reason, the relay device (# 2 )  2  transfers the packet PKT  1  of which the destination address is “P”, as the packet PKT  2 , to the server  5   c  through the interface IF 3 . 
     On the other hand, the relay device (# 3 )  2  transfers the packet PKT of which the destination address is “Z”, and the packet PKT  2 , to the server  5   b  through the interface IF 3 . For this reason, the “destination address”, the “output interface”, and the “NEXT HOP” in routing information K 6  for the relay device (# 3 )  2  indicate “Z”, “IF 3 ”, and “server (firewall)”, respectively. 
     Because the suitable routing information is set in this manner, the network management server  1  searches a route between the transmission source terminal device  3  and the destination terminal device  4 , then detects the servers  5   a  to  5   c  on the route, and categories the servers  5   a  to  5   c  into four types as one example. In  FIGS. 5A to 5D , categorization of the servers is illustrated. 
     According to the present embodiment, the network management server  1  categorizes the servers  5  within the network NW into Type-1 to Type-4. The server  5  has a reception-side interface IFa that receives a packet PKTin from a different device, and a transmission-side interface IFb that transmits to a packet PKTout to the different device. The reception-side interface IFa and the transmission-side interface IFb have individual addresses “Pa” and “Pb”, respectively. 
     In  FIG. 5A , a Type-1 server  5  is illustrated. The Type-1 server  5  transmits the packet PKTin without making any change of the destination address and source address of the packet PKTin. For example, the Type-1 server  5  receives the packet PKTin of which the destination address is “Z” and of which the source address is “A” through the reception-side interface IFa, and transmits the received packet PKTin as it, as the packet PKTout, from the transmission-side interface IFb. 
     As the Type-1 server  5 , in addition to the firewall and the DPI, which are described above, a server equipped with an instruction detection system (IDS) function is given as an example. The IDS has a function of monitoring the packet that is transferred over the network and detecting a wrongful motion. 
     In  FIG. 5B , a Type-2 server  5  (first category) is illustrated. The Type-2 server  5  transmits the packet PKTin of which the source address is changed and the destination address is not changed. For example, the Type-2 server  5  receives the packet PKTin of which the destination address is “Z” and of which the source address is “A” through the reception-side interface IFa, converts the received packet PKTin into the packet PKTout of which the destination address is “Z” and of which the source address is “Pb”, and transmits the resulting packet PKTout from the transmission-side interface IFb. 
     As the Type-2 server  5 , a server equipped with a transparent proxy function, a transparent cache function, a Source based Network Address Translation (SNAT) function, and a Source based Network Address Port Translation (SNAPT) function is given as an example. The cache (web cache) has a function in which, in a case where the proxy function is performed, Web data is temporarily stored (cached), and when the terminal device attempts access again, the stored web data to the terminal device. The SNAT has a function of converting an IP address of a transmission source of a transfer target packet into a designated IP address (for example, an IP address of the transmission-side interface IFb). The SNAP has a function of converting a port number of the transmission source of the packet in addition to converting the address. 
     In  FIG. 5C , a Type-3 (a second category) server  5  is illustrated. The Type-3 server  5  transmits the packet PKTin of which the destination address is changed and the source address is not changed. For example, the Type-3 server  5  receives the packet PKTin of which the destination address is “Pa” and of which the source address is “A” through the reception-side interface IFa, converts the received packet PKTin into the packet PKTout of which the destination address is “Z” and of which the source address is “A” and transmits the resulting packet PKToutput from the transmission-side interface IFb. 
     As the Type-3 server  5 , a server equipped with a Destination based Network Address Translation (DNAT) function is given as an example. The DNAT has a function of converting an IP address of a destination of a received packet. 
     In  FIG. 5D , a Type-4 (a third category) server  5  is illustrated. The Type-4 server  5  changes the destination address and source address of the packet PKTin. For example, the Type-4 server  5  receives the packet PKTin of which the destination address is “Pa” and of which the source address is “A” through the reception-side interface IFa, converts the received packet PKTin into the packet PKTout of which the destination address is “Z” and of which the source address is “Pb” and transmits the resulting packet PKToutput from the transmission-side interface IFb. 
     As the Type-4 server  5 , a server equipped with a non-transparent proxy function or a non-transparent cache function is given as an example. 
     In this manner, regardless of functions of the servers  5 , the network management server  1  categorizes the serves  5  into Type-1 to Type-4 according to the information that, among the destination address and source address of the packet, is changed by the server  5 . As a case where the address is changed, a case where, as in the proxy server, the packet is transferred between different communication sessions, and a case where, as in the proxy server, transfer processing is performed on the IP address are given as examples. However, the network management server  1  categorizes the servers  5  based on a change type of the address of the relayed packet, without distinguishing between the two cases described above. For this reason, the network management server  1  can easily categorize the servers  5 . 
       FIG. 6  is a configuration diagram illustrating one example of the network management server  1 . The network management server  1  has a central processing unit (CPU)  10 , a read only memory (ROM)  11 , a random access memory (RAM)  12 , a hard disk drive (HDD)  13 , an input and output (I/O) unit  14 , and a communication processing unit  15 . 
     The CPU  10  is connected to the ROM  11 , the RAM  12 , the HDD  13 , the I/O unit  14 , and the communication processing unit  15  through a data bus  16 , in such a manner that a signal can be input and output between them. Included in the ROM  11  is a program that drives the CPU  10 . The RAM  12  functions as a working memory if the CPU  10 . 
     Included in the HDD  13  is a topology database (DB)  13   a , a categorization table  13   b , and routing information  13   c . The topology DB  13   a  consists of pieces of information indicating a configuration of the network NW, and is used in searching for the packet route. The categorization table  13   b  lists pieces of information indicating categories (Type-1 to Type-4) of the servers  5  within the network NW, and is used in generating the routing information  13   c.    
     The I/O unit  14  performs input and output between an input device such as a keyboard or a mouse and an output device such as a display. The communication processing unit  15  is, for example, a network interface card, and communicates with the relay devices  2  and the servers  5  within in the network NW. Moreover, a type of communication may be either of cabled communication and wireless communication. 
     When a program is read from the ROM  11 , functionally formed in the CPU  10  are a request processing unit  100 , a route search unit  101 , a routing information generation unit (a generation unit)  102 , a server categorization unit (a categorization unit)  103 , and a routing information setting unit  104 . 
     The request processing unit  100  receives a request for the packet route from a user through the I/O unit  14 . For example, designation of one or more servers  5  through which the packet passes is included in the request. Additionally, designation of the order in which the packet passes through every server  5  may be included in the request. The request processing unit  100  outputs the received request, as request information, to the route search unit  101 . 
     The route search unit  101  searches the topology DB  13   a  for the route connecting everything from the transmission source terminal device  3  to the destination terminal device  4 . Pieces of information relating to nodes within the network NW, to be more precise, the relay devices  2  and the servers  5 , and links that connect between each node are registered in the topology DB  13   a  with the nodes and the links being associated with one another. Furthermore, pieces of information on nodes to which each of the transmission source terminal device  3  and the destination terminal device  4  is connected are registered in the topology DB  13   a.    
     With the request information, the route search unit  101  searches for the route on which the designated servers  5  are present. For this reason, the route search unit  101  divides the route into a section from the transmission source terminal device  3  to a designated server among the servers  5 , a section between the designated servers  5 , and a section from the designated server  5  to the destination terminal device  4 , and searches for the route based on segments. As a search technique, a Dijkstra method is given as an example, but is not limited to this. The route search unit  101  outputs the found route, as route configuration information, to the routing information generation unit  102 . 
     Based on the route configuration information, the routing information generation unit  102  generates the routing information  13   c  for the relay devices  2  and the servers  5  on the route, and stores the generated routing information  13   c  in the HDD  13 . When the generation of the routing information  13   c  for all the relay devices  2  and all the servers  5  on the route is completed, the routing information generation unit  102  notifies the routing information setting unit  104  of this. 
     The routing information generation unit  102  generates the routing information  13   c  according to a result of the server categorization unit  103  categorizing the servers  5  on the route. The routing information generation unit  102  outputs to the server categorization unit  103  the routing information described above and device information indicating which device the routing information  13   c  is generated for. Based on the route configuration information, the device information, and the categorization table  13   b , the server categorization unit  103  detects the servers  5  on the route and categories the detected servers  5 . 
     The route configuration information, for example, indicates identification information (for example, an IP addresses) on each of the relay devices  2  or the servers  5  on the found route and a device type (the relay device  2  or the server  5 ), sequentially along the route. The device information indicates the identification information on the relay devices  2  or the servers  5  for which the routing information  13   c  is generated. Included in the categorization table  13   b  are Type-1 to Type-4 into which the serves  5  within the network NW are categorized. That is, the pieces of identification information on and the categories of the servers  5  are registered in the categorization table  13   b  with the pieces of identification information and the categories being associated with one another. 
     The server categorization unit  103  notifies the routing information generation unit  102  of a result of the categorization of the servers  5 . According to the result of the categorization of the servers  5 , the routing information generation unit  102  determines at least one of the destination address and the source address that are set as the routing information  13   c , and generates the routing information  13   c . For this reason, even though the servers on the route  5  changes at least one of the destination address and source address of the packet that passes through the servers, the routing information generation unit  102  can generate the suitable routing information  13   c . Moreover, a method of generating the routing information  13   c  will be described in detail below. 
     When the generation of the routing information  13   c  is notified from the routing information generation unit  102 , the routing information setting unit  104  reads the routing information  13   c  from the HDD  13 , and transmits the read routing information to the relay devices  2  and the serves  5  within the network NW through the communication processing unit  15 . Accordingly, the routing information  13   c  is set to the relay devices  2  and the servers  5   b.    
       FIG. 7  is a configuration diagram illustrating one example of the servers  5  within the network NW. The servers  5  each have a CPU  50 , a ROM  51 , a RAM  52 , a HDD  53 , an I/O unit  54 , and multiple interface units  55 . 
     The CPU  50  is connected to the ROM  51 , the RAM  52 , the HDD  53 , the I/O unit  54 , and the multiple interface (INF) units  55  through a data bus  56 , in such a manner that a signal can be input and output between them. Included in the ROM  51  is a program that drives the CPU  50 . The RAM  52  functions as a working memory if the CPU  50 . 
     Stored in the HDD  53  is routing information  53   a  received from the network management server  1 . The I/O unit  54  performs input and output between an input device such as a keyboard or a mouse and an output device such as a display. 
     The interface unit  55 , for example, is a network interface card, and communicates with different relay devices  2  and different servers  5  within the network NW. The interface unit  55  is installed in every interface IFm described above. 
     When a program is read from the ROM  51 , a packet processing unit  500  and a transfer processing unit  501  are functionally formed in CPU  50 . The packet processing unit  500  processes the packet received through the interface unit  55 . Contents of the processing vary with each of the servers  5 . 
     The transfer processing unit  501  transfers the packet that goes through the processing by the packet processing unit  500 , based on the routing information  53   a . The transfer processing unit  501  outputs the packet that is consistent with at least one of the destination address and the source address that are indicated by the routing information  53   a , to the interface unit  55  that corresponds to an output interface that is indicated by the routing information  53   a . Accordingly, the packet is transferred to the suitable transfer destination along the route. 
       FIG. 8  is a configuration diagram illustrating one example of the relay devices  2 . The relay devices  2  each have a CPU  20 , a memory  21 , a communication processing unit  22 , a switch (SW)  23 , and multiple interface (INF) units  24 . 
     The CPU  20  controls the operation of all the relay devices  2 . The CPU  20  communicates with the network management server  1  through the communication processing unit  22 . The CPU  20  stores routing information  21   a  received from the network management server  1  in the memory  21 . 
     The switch  23  is connected to the multiple interface units  24 . The interface unit  24  is installed in every interface IFn described above. 
     The CPU  20  sets the routing information  21   a  stored in the memory  21  to the switch. The switch  23  exchanges the packet between each interface unit  24 , according to the routing information  21   a.    
     The switch  23  outputs the packet that is consistent with at least one of the destination address and the source address that are indicated by the routing information  21   a , to the interface unit  24  that corresponds to an output interface that is indicated by the routing information  21   a . Accordingly, the packet is transferred to the suitable transfer destination along the route. 
     Next, a method in which the network management server  1  generates the routing information will be described in detail below.  FIG. 9  is a configuration diagram illustrating one example of the network NW for which the routing information is set. In  FIG. 9 , constituent elements that are the same as those illustrated in  FIGS. 1 to 4  are given the same reference numerals and descriptions of them are omitted. 
     The network NW in the present example includes the relay devices (# 1  to # 4 )  2  and the servers  5   d  to  5   f . Instead of the servers  5   a  to  5   c  in  FIG. 4 , servers  5   d  to  5   f  are installed. The servers  5   d  to  5   f  are categorized into Type-2, Type-3, and Type-4. 
     The server  5   d  is connected to the relay devices (# 1  and # 2 )  2  through interfaces IF 1 (IFa) and IF 2 (IFb), respectively. At this point, addresses of the interfaces IF 1  and IF 2  are set to be “P 2   a ” and “P 2   b”.    
     The server  5   e  is connected to the relay devices (# 2  and # 3 )  2  through interfaces IF 1  and IF 2 , respectively. At this point, the addresses of the interfaces IF 1  and IF 2  are set to be “P 3   a ” and “P 3   b”.    
     The server  5   f  is connected to the relay devices (# 3  and # 4 )  2  through interfaces IF 1  and IF 2 , respectively. At this point, the addresses of the interfaces IF 1  and IF 2  are set to be “P 4   a ” and “P 4   b”.    
     Furthermore, the relay device (# 1 )  2  is connected to the transmission source terminal device  3  through the interface IF 1 , and is connected to the relay device (# 2 )  2  through the interface IF 2 . Additionally, the relay device (# 1 )  2  is connected to the server  5   d  through the interface IF 3 . 
     The relay device (# 2 )  2  is connected to the server  5   d  through the interface IF 1 , and is connected to the relay device (# 1 )  2  through the interface IF 2 . Additionally, the relay device (# 2 )  2  is connected to the server  5   e  through the interface IF 3 , and is connected to the relay device (# 3 )  2  through the interface IF 4 . 
     The relay device (# 3 )  2  is connected to the server  5   e  through the interface IF 1 , and is connected to the relay device (# 2 )  2  through the interface IF 2 . Additionally, the relay device (# 3 )  2  is connected to the server  5   f  through the interface IF 3 , and is connected to the relay device (# 4 )  2  through the interface IF 4 . 
     The relay device (# 4 )  2  is connected to the server  5   f  through the interface IF 1 , and is connected to the relay device (# 3 )  2  through the interface IF 2 . Additionally, the relay device (# 4 )  2  is connected to the destination terminal device  4  through the interface IF 3 . 
     The route search unit  101  searches for a packet route R 5 . The packet that is transferred over the route R 5  passes through the relay device (# 1 )  2 , the server  5   d , the relay device (# 2 )  2 , the server  5   e , the relay device (# 3 )  2 , the server  5   f , and the relay device (# 4 )  2 , in this sequence. 
     In  FIG. 10 , a situation in which the destination address and the source address are changed on the packet route R 5 . Illustrated in  FIG. 10  are a packet PKT  12  that is transferred from the transmission source terminal device  3  to the server  5   d  through the relay device (# 1 )  2 , and a packet PKT  23  that is transferred from the server  5   d  to the server  5   e  through the relay device (# 2 )  2 . Additionally illustrated in  FIG. 10  are a packet PKT  34  that is transferred from the server  5   e  to the server  5   f  through the relay device (# 3 )  2 , and a packet PKT  40  that is transferred from the server  5   f  to the destination terminal device  4  through the relay device (# 4 )  2 . 
     The Type-3 server  5   e  and the Type-4 server  5   f  change the destination addresses of the received packets PKT  23  and PKT 34 . For this reason, the destination addresses of the packets PKT  12  and PKT  23  indicate the interface IF 1  of the server  5   e , to be more precise, “P 3   a ”, and the destination address of the packet PKT  34  indicates the interface IF 1  of the server  5   f , to be more precise, “P 4   a ”. Furthermore, the destination address of the packet PKT  40  indicates the destination terminal device  4 , to be more precise, “Z”. 
     Furthermore, the Type-2 server  5   d  and the Type-4 server  5   f  change source addresses of the received packets PKT  12 , PKT 23 , and PKT 34 . For this reason, the source address of the packet PKT  12  indicates the transmission source terminal device  3 , to be more precise, “A”, and the source addresses of the packets PKT 23  and PKT 34  indicate the interface IF 2  of the server  5   d , to be more, “P 2   b ”. Furthermore, the source address of the packet PKT  40  indicates the interface IF 2  of the server  5   f , to be more precise, “P 4   b”.    
     By categorizing the servers  5   d  to  5   f  on the route R 5 , the network management server  1  recognizes information that, among the destination address and source address of the packet, is changed in the servers  5   d  to  5   f , and generates the routing information according to the changed information. A generation method according to first to fourth embodiments will be described below. 
     First Embodiment 
     According to the present embodiment, the network management server  1  searches for the Type-3 or Type-4 server  5   e  or  5   f  that is present to the destination sides (downward sides) of the relay devices  2  or the servers  5   d  to  5   f  on the route R 5 , for which the routing information is generated, or searches for the destination terminal device  4 . The network management server  1  generates the routing information, based on an address of the found Type-3 or Type-4 server  5   e  or  5   f  or an address of the found destination terminal device  4 . 
       FIG. 11  a flowchart illustrating processing that generates the routing information according to the first embodiment. First, the route search unit  101  searches for the route according to a request (an operation St 1 ). Accordingly, the route R 5  on which the indicated servers  5   d  to  5   f  are present is searched for. 
     Next, the routing information generation unit  102  determines the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated, from the relay devices  2  and the servers  5   d  to  5   f  on the route R 5  (an operation St 2 ). Next, based on the route configuration information, the server categorization unit  103  selects a device that is a node in the neighborhood in the downstream direction (in the destination side direction), of the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is generated (an operation St 3 ). 
     Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 4 ). In a case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 4 ), the server categorization unit  103  categories the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 5 ). 
     Next, in a case where, as a result of the categorization, the servers  5   d  to  5   f  are categorized into Type-3 or Type-4 (Yes in an operation St 6 ), the routing information generation unit  102  determines addresses of the servers  5   d  to  5   f  as destination addresses in the routing information (an operation St 7 ). Next, the routing information generation unit  102  generates the routing information based on the determined destination address (an operation St 8 ). 
     Furthermore, in a case where the selected device is not the servers  5   d  to  5   f  (No in the operation St 4 ), the server categorization unit  103  determines whether or not the device of which the selection is in progress is the destination terminal device  4  (an operation St  10 ). In a case where the device of which the selection is in progress is the destination terminal device  4  (Yes in the operation St  10 ), the routing information generation unit  102  determines an address “Z” of the destination terminal device  4  as the destination address in the routing information (an operation St  11 ). Next, the routing information generation unit  102  generates the routing information based on the determined destination address (an operation St 8 ). 
     In a case where the device of which the selection is in progress is not the destination terminal device  4  (No in the operation St 10 ), the server categorization unit  103  again performs the processing in the operation St 3 . In this case, the server categorization unit  103  selects the device that is a node in the neighborhood in the downstream direction, of the device of which the selection is in progress. 
     Furthermore, in a case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-2 (No in the operation St 6 ), the server categorization unit  103  again performs the processing in the operation St 3  as well. Also in this case, the server categorization unit  103  selects the device that is a node in the neighborhood, in the downstream direction, of the device of which the selection is in progress. 
     In this manner, the server categorization unit  103  searches the device on the route R 5  in the downstream direction (in the destination side direction), until the Type-3 or Type-4 server  5   e  or  5   f , or the destination terminal device  4  is detected. Then, the routing information generation unit  102  generates the routing information based on the address of Type-3 or Type-4 server  5   e ,  5   f , or the destination terminal device  4  that is first detected. 
     After the routing information is generated (the operation St 8 ), if the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is not generated are present (Yes in the operation St 9 ), the routing information generation unit  102  again performs the processing in the operation St 2 . If the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is not generated are present (No in the operation St 9 ), the routing information generation unit  102  again performs the processing in the operation St 2 . In this manner, the processing that generates the routing information is performed. 
     In  FIG. 12 , an example of generating the routing information according to the present embodiment is illustrated. In  FIG. 12 , an example of generating the routing information for the relay device (# 1 )  2  and the server  5   f  is given. Moreover, in  FIG. 12 , an arrow indicates the order in which the network devices are selected by the server categorization unit  103  as detection targets. 
     In a case where a target for which the routing information is generated is determined as the relay device (# 1 )  2 , the server categorization unit  103  selects the server  5   d  that is a node in the neighborhood in the downstream direction, of the relay device (# 1 )  2  (refer to the operation St 3 ). Because, as a result of the categorization (refer to the operation St 5 ), the server  5   d  is neither Type-3 nor Type-4 (refer to No in the operation St 6 ), the server categorization unit  103  selects the relay device (# 2 )  2  that is a node in the neighborhood in the downward, of the server  5   d  (refer to the operation St 3 ). 
     Because the relay device (# 2 )  2  is neither the server (refer to No in the operations St 4 ), nor the destination terminal device  4  (refer to No in the operation St 10 ), the server categorization unit  103  selects the server  5   e  that is a node in the neighborhood in the downstream direction, of the relay device (# 2 )  2  (refer to the operation St 3 ). Because the server  5   e  is categorized into Type-3 (refer to Yes in the operation St 6 ), the routing information generation unit  102  generates the routing information based on the address “P 3   a ” OF the interface IF 1  in the upstream direction (in the direction of the transmission source), of the server  5   e  (refer to the operations St 7  and St 8 ). 
     Therefore, the “destination address” in routing information K 7  for the relay device (# 1 )  2  indicates “P 3   a ”. In a case where an address of the server  5   e  is only one without being provided to each of the interfaces IF 1  and IF 2 , the “destination address” in the routing information K 7  indicates the address of the relay device (# 1 )  2 . Moreover, the “output interface” and the “NEXT HOP” in the routing information K 7  indicate “IF 3 ” and “server (Type-2)”, respectively. 
     Furthermore, in a case where the target for which the routing information is generated is determined as the server  5   f , the server categorization unit  103  selects the relay device (# 4 )  2  that is a node in the neighborhood in the downstream direction, of the server  5   f  (refer to the operation St 3 ). Because the relay device (# 4 )  2  is neither the server (refer to No in the operation St 4 ), nor the destination terminal device  4  (refer to No in the operation St 10 ), the server categorization unit  103  selects the destination terminal device  4  that is a node in the neighborhood in the downstream direction, of the relay device (# 4 )  2  (refer to the operation St 3 ). Because the destination terminal device  4  is selected (refer to Yes in the operation St 10 ), the routing information generation unit  102  generates the routing information based on the address “Z” of the destination terminal device  4  (refer to the operations St 7  and St 8 ). 
     Therefore, the “destination address” in the routing information K 8  for the server  5   f  indicates “Z”. Moreover, the “output interface” and the “NEXT HOP” in the routing information K 8  indicate “IF 2 ” and “destination terminal device”, respectively. 
     In this manner, the server categorization unit  103  sequentially selects the detection target network devices in such a manner that the packet route starting from the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated leads to the destination (the destination terminal device  4 ) of the packet. The routing information generation unit  102  generates the routing information based on the destination address indicating Type-3 or Type-4 server  5   e  or  5   f , or the destination terminal device  4  that is first detected by the server categorization unit  103 . 
     According to the present embodiment, the routing information for the individual relay devices  2  or the individual servers  5   d  to  5   f  can be easily generated based on the result of the detection of the node (refer to  FIG. 10 ) of which the destination address is changed. 
     Second Embodiment 
     However, according to the first embodiment, because as many as the relay devices  2  and the serves  5   d  to  5   f  on the route R 5  is searched among the network devices on the route R 5 , the greater the number of devices, the more time it takes to generate the routing information. Then, as in a technique described below, with the one-time search of the network devices on the route R 5 , the time it takes to perform generation processing may be shortened by generating the routing information for the each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5 . Moreover, according to the present embodiment, it is also assumed that the routing information for each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5  is generated to configure the route R 5  over the network NW illustrated in  FIGS. 9 and 10 . 
       FIG. 13  is a flowchart illustrating processing that generates the routing information according to the second embodiment. First, the route search unit  101  searches for the route according to a request (an operation St 21 ). Accordingly, the route R 5  on which the indicated servers  5   d  to  5   f  are present is searched for. 
     Next, the routing information generation unit  102  sets the address “Z” of the destination terminal device  4  to be a temporary address ADD corresponding to the destination address in the routing information (an operation St 22 ). The temporary address ADD, as described below, is used as the destination address in the routing information for the network device on the route R 5 , and is changed to the address of the server  5   e  or  5   f  whenever Type-3 or Type-4 server  5   e  or  5   f  is detected. The temporary address ADD, for example, is temporarily stored in a storage unit, for example, such as the HDD  13 . 
     Next, based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the upstream direction (in the direction of the transmission source), of the destination terminal device  4 , as a target for which the routing information is generated (an operation St 23 ). That is, the routing information generation unit  102  selects the relay device (# 4 )  2 . 
     Next, the routing information generation unit  102  generates the routing information for a device of which the selection is in progress, with the temporary ADD serving as the destination address (an operation St 24 ). Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 25 ). 
     In a case where the device of which the selection is in progress is not the servers  5   d  to  5   f  (No in the operation St 25 ), based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the upstream direction, of the device of which the selection is in progress, as the target for which the routing information is generated (an operation St 29 ). For example, in a case where the device of which the selection is in progress is the relay device (# 4 )  2 , the routing information generation unit  102  selects the server  5   f  in the neighborhood of the relay device (# 4 )  2 . 
     Next, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the transmission source terminal device  3  (an operation St 30 ). In a case where the device of which the selection is in progress is not the transmission source terminal device  3  (No in the operation St 30 ), to be more precise, in a case where the device of which the selection is progress is the relay devices  2 , the routing information generation unit  102  again performs the processing in the operation St 24 . 
     In a case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 25 ), the server categorization unit  103  categorizes the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 26 ). Next, in a case where, as a result of the categorization, the servers  5   d  to  5   f  are categorized into Type-3 or Type-4 (Yes in the operation St 27 ), the routing information generation unit  102  sets addresses of the servers  5   d  to  5   f  to be the temporary address ADD (an operation St 28 ). That is, the routing information generation unit  102  writes the temporary address ADD in storage to the addresses of the servers  5   d  to  5   f . Thereafter, in the operation St 29 , the next-neighboring device is selected. 
     Furthermore, also in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-2 (No in the operation St 27 ), the next-neighboring device is selected in the operation St 29 . 
     Furthermore, in a case where the device that is selected in the operation St 29  is the transmission source device  3  (Yes in the operation St 30 ), because the search of all the devices on the route R 5  is ended, the routing information generation unit  102  ends the processing. 
     In  FIG. 14 , an example of generating the routing information according to the present embodiment is illustrated. Moreover, in  FIG. 14 , a dotted-line arrow indicates the order in which the network devices are selected by the routing information generation unit  102  as targets for which the routing information is generated, and a solid line arrow ADD indicates a change in a value of the temporary address described below. 
     First, the routing information generation unit  102  sets the address “Z” of the destination terminal device  4  to be the temporary address ADD (refer to the operation St 22 ), and selects the relay device (# 4 )  2  as the target for which the routing information is generated (refer to the operation St 23 ). The routing information generation unit  102  generates the routing information for the relay device (# 4 )  2  based on the temporary address ADD=“Z” (refer to the operation St 24 ). 
     Next, the routing information generation unit  102  selects the server  5   f  that is a node in the neighborhood in the upstream direction, of the relay device (# 4 )  2 , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the server  5   f  based on the temporary address ADD=“Z” (refer to the operation St 24 ). 
     Because the server  5   f  is categorized by the server categorization unit  103  into Type-4 (refer to Yes in the operation St 27 ), the routing information generation unit  102  sets the address “P 4   a ” of the server  5   f  of which the selection is in progress to be the temporary address ADD (refer to the operation St 28 ). At this time, the routing information generation unit  102  sets the address “P 4   a ” of the interface IF 1  in the upstream direction (in the direction of the transmission source), of the server  5   f , to be the temporary ADD. In the case where the address of the server  5   f  is only one without being provided to each of the interfaces IF 1  and IF 2 , the address of the server  5   f  is set to be the temporary address ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 3 )  2  that is a node in the neighborhood in the upstream direction, of the server  5   f , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the relay device (# 3 )  2  based on the temporary address ADD=“P 4   a ” (refer to the operation St 24 ). 
     Next, the routing information generation unit  102  selects the server  5   e  that is a node in the neighborhood in the upstream direction, of the relay device (# 3 )  2 , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the server  5   e  based on the temporary address ADD=“P 4   a ” (refer to the operation St 24 ). 
     Because the server  5   e  is categorized by the server categorization unit  103  into Type-3 (refer to Yes in the operation St 27 ), the routing information generation unit  102  sets the address “P 3   a ” of the server  5   f  of which the selection is in progress to be the temporary address ADD (refer to the operation St 28 ). At this time, the routing information generation unit  102  sets the address “P 3   a ” of the interface IF 1  in the upstream direction (in the direction of the transmission source), of the server  5   e , to be the temporary ADD. In the case where the address of the server  5   e  is only one without being provided to each of the interfaces IF 1  and IF 2 , the address of the server  5   e  is set to be the temporary address ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 2 )  2  that is a node in the neighborhood in the upstream direction, of the server  5   e , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the relay device (# 2 )  2  based on the temporary address ADD=“P 3   a ” (refer to the operation St 24 ). 
     Next, the routing information generation unit  102  selects the server  5   d  that is a node in the neighborhood in the upstream direction, of the relay device (# 2 )  2 , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the server  5   d  based on the temporary address ADD=“P 3   a ” (refer to the operation St 24 ). 
     Because the server  5   d  is categorized by the server categorization unit  103  into Type-2 (refer to No in the operation St 27 ), the routing information generation unit  102  does not change the temporary ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 1 )  2  that is a node in the neighborhood in the upstream direction, of the server  5   d , as the target for which the routing information is generated (refer to the operation St 29 ). The routing information generation unit  102  generates the routing information for the relay device (# 1 )  2  based on the temporary address ADD=“P 3   a ” (refer to the operation St 24 ). Next, the routing information generation unit  102  selects the transmission source terminal device  3  that is a node in the neighborhood in the upstream direction, the relay device (# 1 )  2 , but because the transmission source terminal device  3  is not the target for which the routing information is generated, ends the search (refer to Yes in the operation St 30 ). 
     In this manner, the routing information generation unit  102  sequentially selects the network device for which the routing information is generated, in such a manner that the packet route R 5  starting from the destination terminal device  4  leads to the transmission source terminal device  3 . When a network device for which the routing information is generated is categorized into Type-3 or Type-4, the routing information generation unit  102  generates the routing information for a network device for which the routing information is generated, which is selected after the Type-3- or Type-4-categorized network device, based on the destination address indicating the Type-3- or Type-4-categorized network device. 
     According to the present embodiment, because, with the one-time search of the network devices on the route R 5 , the routing information for each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5  can be generated, the time it takes to perform the generation processing can be shortened. 
     Third Embodiment 
     According to the first and second embodiments, the technique is given in which the routing information is generated based on only the destination address among the destination address and the source address, but the routing information may be generated based on both of the destination address and the source address. In this case, the relay devices  2  and the servers  5   d  to  5   f  on the route R 5  specify the transfer target packet based on both of the destination address and the source address. For this reason, the transmission source terminal device  3  and the destination terminal device  4  can perform bidirectional communicate over the route R 5 . 
     According to the present embodiment, the network management server  1  determines the destination address with the same technique as that employed according to the first embodiment, and determines the source address with a technique similar to that employed according to the first embodiment. Moreover, according to the present embodiment, it is also assumed that the routing information for each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5  is generated to configure the route R 5  on the network NW illustrated in  FIGS. 9 and 10 . 
       FIGS. 15A and 15B  are flowcharts illustrating the processing that generates the routing information according to a third embodiment. First, the route search unit  101  searches for the route according to a request (an operation St 31 ). Accordingly, the route R 5  on which the indicated servers  5   d  to  5   f  are present is searched for. 
     Next, the routing information generation unit  102  determines the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated, from the relay devices  2  and the servers  5   d  to  5   f  on the route R 5  (an operation St 32 ). Next, based on the route configuration information, the server categorization unit  103  selects a device that is a node in the neighborhood in the downstream direction (in the destination side direction), of the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is generated (an operation St 33 ). 
     Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 34 ). In the case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 34 ), the server categorization unit  103  categories the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 35 ). 
     Next, in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-3 or Type-4 (Yes in the operation St 36 ), the routing information generation unit  102  determines the addresses of the servers  5   d  to  5   f  as the destination address in the routing information (an operation St 37 ). 
     Furthermore, in the case where the selected device is not the servers  5   d  to  5   f  (No in the operation St 34 ), the server categorization unit  103  determines whether or not the device of which the selection is in progress is the destination terminal device  4  (an operation St 45 ). In the case where the device of which the selection is in progress is the destination terminal device  4  (Yes in the operation St 45 ), the routing information generation unit  102  determines an address “Z” of the destination terminal device  4  as the destination address in the routing information (an operation St 46 ). 
     In the case where the device of which the selection is in progress is not the destination terminal device  4  (No in the operation St 45 ), the server categorization unit  103  again performs the processing in the operation St 33 . In this case, the server categorization unit  103  selects the device that is a node in the neighborhood in the downstream direction, of the device of which the selection is in progress. 
     Furthermore, in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-2 (No in the operation St 36 ), the server categorization unit  103  again performs the processing in the operation St 33  as well. Also in this case, the server categorization unit  103  selects the device that is a node in the neighborhood, in the downstream direction, of the device of which the selection is in progress. 
     In this manner, the server categorization unit  103  searches the device on the route R 5  in the downstream direction, until the Type-3 or Type-4 server  5   e  or  5   f , or the destination terminal device  4  is detected. Then, the routing information generation unit  102  determines the address of Type-3 or Type-4 server  5   e  or  5   f , or the destination device  4  that is first detected, as the destination address in the routing information. Moreover, the processing here is the same as that illustrated in  FIG. 11 , in terms of contents. 
     After the destination address in the routing information is determined (the operation St 37 ), based on the route configuration information, the routing information generation unit  102  selects the device that is a node in the neighborhood in the upstream direction (in the direction of the transmission source), of the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated (an operation St 38 ). 
     Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 39 ). In the case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 39 ), the server categorization unit  103  categories the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 40 ). 
     Next, in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-2 or Type-4 (Yes in the operation St 41 ), the routing information generation unit  102  determines the addresses of the servers  5   d  to  5   f  as the source address in the routing information (an operation St 42 ). Next, the routing information generation unit  102  generates the routing information based on the determined destination address and transmission address (an operation St 43 ). 
     Furthermore, in the case where the selected device is not the servers  5   d  to  5   f  (No in the operation St 39 ), the server categorization unit  103  determines whether or not the device of which the selection is in progress is the transmission source terminal device  3  (an operation St 47 ). In a case where the device of which the selection is in progress is the transmission source terminal device  3  (Yes in the operation St 47 ), the routing information generation unit  102  determines the address “A” of the transmission source terminal device  3  as the destination address in the routing information (an operation St 48 ). Next, the routing information generation unit  102  generates the routing information based on the determined destination address and transmission address (an operation St 43 ). 
     In a case where the device of which the selection is in progress is not the transmission source terminal device  3  (No in the operation St 47 ), the server categorization unit  103  again performs the processing in the operation St 38 . In this case, the server categorization unit  103  selects the device that is a node in the neighborhood in the upstream direction, of the device of which the selection is in progress. 
     Furthermore, in a case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-3 (No in the operation St 41 ), the server categorization unit  103  again performs the processing in the operation St 38  as well. Also in this case, the server categorization unit  103  selects the device that is a node in the neighborhood in the upstream direction, of the device of which the selection is in progress. 
     In this manner, the server categorization unit  103  searches the device on the route R 5  in the upstream direction, until the Type-2 or Type-4 server  5   d  or  5   f , or the transmission source terminal device  3  is detected. Then, the routing information generation unit  102  determines the address of Type-2 or Type-4 server  5   d  or  5   f , or the destination device  4  that is first detected, as the source address in the routing information. 
     After the routing information is generated (the operation St 43 ), if the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is not generated are present (Yes in the operation St 44 ), the routing information generation unit  102  again performs the processing in the operation St 32 . If the relay devices  2  and the servers  5   d  to  5   f  for which the routing information is not generated are not present (No in the operation St 44 ), the routing information generation unit  102  ends the processing. In this manner, the processing that generates the routing information is performed. 
     In  FIG. 16 , an example of generating the routing information according to the present embodiment is illustrated. In  FIG. 16 , an example of generating the routing information for the relay device (# 1 )  2  is given. Moreover, in  FIG. 16 , an arrow indicates the order in which the network devices are selected by the server categorization unit  103  as the detection targets. 
     In the case where a target for which the routing information is generated is determined as the relay device (# 1 )  2 , the server categorization unit  103  selects the server  5   d  that is a node in the neighborhood in the downstream direction, of the relay device (# 1 )  2  (refer to the operation St 33 ). Because, as the result of the categorization (refer to the operation St 35 ), the server  5   d  is neither Type-3 nor Type-4 (refer to No the operation St 36 ), the server categorization unit  103  selects the relay device (# 2 )  2  that is a node in the neighborhood in the downward, of the server  5   d  (refer to the operation St 33 ). 
     Because neither the relay device (# 2 )  2  is neither the server (refer to No in the operation St 34 ) nor the destination terminal device  4  (refer to No in the operation St 45 ), the server categorization unit  103  selects the server  5   e  that is a node in the neighborhood in the downstream direction, of the relay device (# 2 )  2  (refer to the operation St 33 ). Because the server  5   e  is categorized into Type-3 (refer to Yes in the operation St 36 ), the routing information generation unit  102  determines the address “P 3   a ” of the interface IF 1  in the upstream direction (in the direction of the transmission source), of the server  5   e , as the destination address in the routing information (refer to the operations St 37 ). 
     Next, the routing information generation unit  102  selects the transmission source terminal device  3  that is a node in the neighborhood in the upstream direction, of the relay device (# 1 )  2  for which the routing information is generated (refer to the operation St 38 ). For this reason, the routing information generation unit  102  determines the address “A” of the transmission source terminal device  3  as the source address in the routing information (refer to an operation St 48 ). The routing information generation unit  102  generates routing information K 9  based on the destination address “P 3   a ” and the source address “A” that are determined (refer to the operation St 43 ). Moreover, the “output interface” and the “NEXT HOP” in the routing information K 9  indicate “IF 3 ” and “server (Type-2)”, respectively. 
     In  FIG. 17 , another example of generating the routing information according to the present embodiment is illustrated. In  FIG. 17 , an example of generating the routing information for the server  5   f  is given. Moreover, in  FIG. 17 , an arrow indicates the order in which the network devices are selected by the server categorization unit  103  as detection targets. 
     In the case where the target for which the routing information is generated is determined as the server  5   f , the server categorization unit  103  selects the relay device (# 4 )  2  that is a node in the neighborhood in the downstream direction, of the server  5   f  (refer to the operation St 33 ). Because the relay device (# 4 )  2  is neither the server (refer to No in the operation St 34 ), nor the destination terminal device  4  (refer to No in the operation St 45 ), the server categorization unit  103  selects the destination terminal device  4  that is a node in the neighborhood in the downstream direction, of the relay device (# 4 )  2  (refer to the operation St 33 ). For this reason, the routing information generation unit  102  determines the address “Z” of the destination address terminal device  4  as the destination address in the routing information (refer to an operation St 46 ). 
     Next, the routing information generation unit  102  selects the relay device (# 3 )  2  that is a node in the neighborhood in the upstream direction, of the server  5   f  for which the routing information is generated (refer to the operation St 38 ). 
     Because neither the relay device (# 3 )  2  is neither the server (refer to No in the operation St 39 ) nor the transmission source terminal device  3  (refer to No in the operation St 47 ), the server categorization unit  103  selects the server  5   e  that is a node in the neighborhood in the upstream direction, of the relay device (# 3 )  2  (refer to the operation St 38 ). Because the server  5   e  is categorized into Type-3 (refer to No in the operation St 41 ), the routing information generation unit  102  selects the relay device (# 2 )  2  that is a node in the neighborhood in the downward, of the server  5   e  (refer to the operation St 38 ). 
     Because neither the relay device (# 2 )  2  is neither the server (refer to No in the operation St 39 ) nor the transmission source terminal device  3  (refer to No in the operation St 47 ), the server categorization unit  103  selects the server  5   d  that is a node in the neighborhood in the upstream direction, of the relay device (# 3 )  2  (refer to the operation St 38 ). Because the server  5   d  is categorized into Type-2 (refer to Yes in the operation St 41 ), the routing information generation unit  102  determines the address “P 2   b ” of the interface IF 2  in the downstream direction (in the direction of the destination), of the server  5   d , as the destination address in the routing information (refer to the operations St 42 ). 
     The routing information generation unit  102  generates routing information K 10  based on the destination address “Z” and the source address “P 2   b ” that are determined (refer to the operation St 43 ). Moreover, the “output interface” and the “NEXT HOP” in the routing information K 10  indicate “IF 2 ” and “destination terminal device”, respectively. 
     In this manner, the server categorization unit  103  sequentially selects the detection target network devices in such a manner that the packet route starting from the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated leads to the destination (the destination terminal device  4 ) of the packet. The routing information generation unit  102  generates the routing information based on the destination address indicating Type-3 or Type-4 server  5   e  or  5   f , or the destination terminal device  4  that is first detected by the server categorization unit  103 . 
     Additionally, the server categorization unit  103  sequentially selects the detection target network devices in such a manner that the packet route starting from the relay devices  2  or the servers  5   d  to  5   f  for which the routing information is generated leads to the transmission source (the transmission source terminal device  3 ) of the packet. The routing information generation unit  102  generates the routing information based on the destination source address indicating Type-2 or Type-4 server  5   d  or  5   f , or the transmission source terminal device  3  that is first detected by the server categorization unit  103 . 
     According to the present embodiment, the routing information for the individual relay devices  2  or the individual servers  5   d  to  5   f  can be easily generated based on the result of the detection of the node (refer to  FIG. 10 ) of which the destination address and the source address are changed. 
     Fourth Embodiment 
     However, according to the third embodiment, because as many as the relay devices  2  and the serves  5   d  to  5   f  on the route R 5  is searched among the network devices on the route R 5 , the greater the number of devices, the more time it takes to generate the routing information. Then, as in a technique described below, with the one-at-a-time search of the network devices on the route R 5  in the upstream direction and in the downstream direction, the time it takes to perform the generation processing may be shortened by generating the routing information for the each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5 . 
     According to the present embodiment, the network management server  1  determines the destination address with the same technique as that employed according to the second embodiment, and determines the source address with a technique similar to that employed according to the second embodiment. Moreover, according to the present embodiment, it is also assumed that the routing information for each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5  is generated to configure the route R 5  on the network NW illustrated in  FIGS. 9 and 10 . 
       FIGS. 18A and 18B  are flowcharts illustrating processing that generates the routing information according to the fourth embodiment. First, the route search unit  101  searches for the route according to a request (an operation St 51 ). Accordingly, the route R 5  on which the indicated servers  5   d  to  5   f  are present is searched for. 
     Next, the routing information generation unit  102  sets the address “Z” of the destination terminal device  4  to be a temporary address ADD corresponding to the destination address in the routing information (an operation St 52 ). The temporary address ADD, for example, is temporarily stored in a storage unit, for example, such as the HDD  13 . 
     Next, based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the upstream direction (in the direction of the transmission source), of the destination terminal device  4 , as a target for which the routing information is generated (an operation St 53 ). That is, the routing information generation unit  102  selects the relay device (# 4 )  2 . 
     Next, the routing information generation unit  102  determines the temporary ADD as the destination address in the routing information for the device of which the selection is in progress, and stores the resulting destination address in the storage unit, for example, such as the HDD  13  (an operation St 54 ). Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 55 ). 
     In the case where the device of which the selection is in progress is not the servers  5   d  to  5   f  (No in the operation St 55 ), based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the upstream direction, of the device of which the selection is in progress, as the target for which the routing information is generated (an operation St 59 ). For example, in a case where the device of which the selection is in progress is the relay device (# 4 )  2 , the routing information generation unit  102  selects the server  5   f  in the neighborhood of the relay device (# 4 )  2 . 
     Next, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the transmission source terminal device  3  (an operation St 60 ). In the case where the device of which the selection is in progress is not the transmission source terminal device  3  (No in the operation St 60 ), to be more precise, in a case where the device of which the selection is progress is the relay devices  2 , the routing information generation unit  102  again performs the processing in the operation St 54 . 
     In the case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 55 ), the server categorization unit  103  categorizes the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 56 ). Next, in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-3 or Type-4 (Yes in the operation St 57 ), the routing information generation unit  102  sets addresses of the servers  5   d  to  5   f  to be the temporary address ADD (an operation St 58 ). That is, the routing information generation unit  102  writes the temporary address ADD in storage to the addresses of the servers  5   d  to  5   f . Thereafter, in the operation St 59 , the next-neighboring device is selected. 
     Furthermore, also in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-2 (No in the operation St 57 ), the next-neighboring device is selected in the operation St 59 . 
     Furthermore, in a case where the device that is selected in the operation St 59  is the transmission source device  3  (Yes in the operation St 60 ), because the search of all the devices on the route R 5  in the upstream direction is ended, the routing information generation unit  102  next searches all the devices on the route R 5  in the downlink direction. Moreover, the processing here is the same as that illustrated in  FIG. 13 , in terms of contents. 
     Next, the routing information generation unit  102  sets the address “A” of the transmission source terminal device  3  to be the temporary address ADD corresponding to the source address in the routing information (an operation St 61 ). 
     Next, based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the down direction (in the direction of the destination), of the transmission source terminal device  3 , as the target for which the routing information is generated (an operation St 62 ). That is, the routing information generation unit  102  selects the relay device (# 1 )  2 . 
     Next, the routing information generation unit  102  determines the temporary ADD as the source address in the routing information for the device of which the selection is in progress, and stores the resulting source address in the storage unit, for example, such as the HDD  13  (an operation St 63 ). Next, based on the route configuration information, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the servers  5   d  to  5   f  (an operation St 64 ). 
     In the case where the device of which the selection is in progress is not the servers  5   d  to  5   f  (No in the operation St 64 ), based on the route configuration information, the routing information generation unit  102  selects a device that is a node in the neighborhood in the downstream direction, of the device of which the selection is in progress, as the target for which the routing information is generated (an operation St 68 ). For example, in the case where the device of which the selection is in progress is the relay device (# 1 )  2 , the routing information generation unit  102  selects the server  5   d  in the neighborhood of the relay device (# 1 )  2 . 
     Next, the server categorization unit  103  determines whether or not the device of which the selection is in progress is the destination terminal device  4  (an operation St 69 ). In the case where the device of which the selection is in progress is not the destination terminal device  4  (No in the operation St 69 ), to be more precise, in a case where the device of which the selection is progress is the relay devices  2 , the routing information generation unit  102  again performs the processing in the operation St 63 . 
     In the case where the device of which the selection is in progress is the servers  5   d  to  5   f  (Yes in the operation St 64 ), the server categorization unit  103  categorizes the servers  5   d  to  5   f  based on the categorization table  13   b  (an operation St 65 ). Next, in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-2 or Type-4 (Yes in the operation St 66 ), the routing information generation unit  102  sets addresses of the servers  5   d  to  5   f  to be the temporary address ADD (an operation St 67 ). That is, the routing information generation unit  102  writes the temporary address ADD in storage to the addresses of the servers  5   d  to  5   f . Thereafter, in the operation St 68 , the next-neighboring device is selected. 
     Furthermore, also in the case where, as the result of the categorization, the servers  5   d  to  5   f  are categorized into Type-1 or Type-3 (No in the operation St 66 ), the next-neighboring device is selected in the operation St 68 . 
     Furthermore, in a case where the device selected in the operation St 68  is the destination terminal device  4  (Yes in the operation St 69 ), because all the devices on the route R 5  in the downstream direction is ended, the routing information for each of the device is generated based on the destination address and the source address that are stored (an operation St 70 ). In this manner, the processing that generates the routing information is performed. 
     In  FIG. 19 , an example of generating the routing information according to the present embodiment is illustrated. A technique of determining the destination address in the routing information according to the present embodiment is the same as that employed according to the second embodiment. Because the example of generating the routing information using the technique is described above referring to  FIG. 14 ,  FIG. 19  illustrates only a technique of determining the source address in the routing information. Moreover, in  FIG. 19 , a dotted-line arrow indicates the order in which the network devices are selected by the routing information generation unit  102  as targets for which the routing information is generated, and a solid line arrow ADD indicates a change in a value of the temporary address described below. 
     First, the routing information generation unit  102  sets the address “A” of the transmission source terminal device  3  to be the temporary address ADD (refer to the operation St 61 ), and selects the relay device (# 1 )  2  as the target for which the routing information is generated (refer to the operation St 62 ). The routing information generation unit  102  stores the temporary address ADD=“A” as the source address in the routing information for the relay device (# 1 )  2  (refer to the operation St 63 ). 
     Next, the routing information generation unit  102  selects the server  5   d  that is a node in the neighborhood in the downstream direction, of the relay device (# 1 )  2 , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“A” as the source address in the routing information for the server  5   d  (refer to the operation St 63 ). 
     Because the server  5   d  is categorized by the server categorization unit  103  into Type-2 (refer to Yes in the operation St 66 ), the routing information generation unit  102  sets the address “P 2   b ” of the server  5   d  of which the selection is in progress to be the temporary address ADD (refer to the operation St 67 ). At this time, the routing information generation unit  102  sets the address “P 2   b ” of the interface IF 2  in the downstream direction (in the direction of the destination), of the server  5   d , to be the temporary ADD. In the case where the address of the server  5   d  is only one without being provided to each of the interfaces IF 1  and IF 2 , the address of the server  5   d  is set to be the temporary address ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 2 )  2  that is a node in the neighborhood in the downstream direction, of the server  5   d , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“P 2   b ” as the source address in the routing information for the relay device (# 2 )  2  (refer to the operation St 63 ). 
     Next, the routing information generation unit  102  selects the server  5   e  that is a node in the neighborhood in the downstream direction, of the relay device (# 2 )  2 , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“P 2   b ” as the source address in the routing information for the server  5   e  (refer to the operation St 63 ). 
     Because the server  5   e  of which the selection is in progress is categorized by the server categorization unit  103  into Type-3 (refer to No&#39;s in the operations St 64 , St 65 , and St 66 ), the routing information generation unit  102  does not change the temporary address ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 3 )  2  that is a node in the neighborhood in the downstream direction, of the server  5   e , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“P 2   b ” as the source address in the routing information for the relay device (# 3 )  2  (refer to the operation St 63 ). 
     Next, the routing information generation unit  102  selects the server  5   f  that is a node in the neighborhood in the downstream direction, of the relay device (# 3 )  2 , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“P 2   b ” as the source address in the routing information for the server  5   f  (refer to the operation St 63 ). 
     Because the server  5   f  is categorized by the server categorization unit  103  into Type-4 (refer to Yes in the operation St 66 ), the routing information generation unit  102  sets the address “P 4   b ” of the server  5   f  of which the selection is in progress to be the temporary address ADD (refer to the operation St 67 ). At this time, the routing information generation unit  102  sets the address “P 4   b ” of the interface IF 2  in the downstream direction (in the direction of the destination), of the server  5   d , to be the temporary ADD. In the case where the address of the server  5   f  is only one without being provided to each of the interfaces IF 1  and IF 2 , the address of the server  5   f  is set to be the temporary address ADD. 
     Next, the routing information generation unit  102  selects the relay device (# 4 )  2  that is a node in the neighborhood in the downstream direction, of the server  5   f , as the target for which the routing information is generated (refer to the operation St 68 ). The routing information generation unit  102  stores the temporary address ADD=“P 4   b ” as the source address in the routing information for the relay device (# 4 )  2  (refer to the operation St 63 ). 
     Next, the routing information generation unit  102  selects the destination terminal device  4  that is a node in the neighborhood in the downstream direction, of the relay device (# 4 )  2 . However, because the destination terminal device  4  is not the target for which the routing information is generated, the routing information generation unit  102  ends the search and generates the routing information for each of the devices based on the destination address and the source address that are stored (refer to the operation St 70 ). Moreover, the technique of determining the destination address is as is described referring to  FIG. 14 . 
     In this manner, the routing information generation unit  102  sequentially selects the network device for which the routing information is generated, in such a manner that the packet route R 5  starting from the destination terminal device  4  leads to the transmission source terminal device  3 . When a network device for which the routing information is generated is categorized into Type-3 or Type-4, the routing information generation unit  102  generates the routing information for a network device for which the routing information is generated, which is selected after the Type-3- or Type-4-categorized network device, based on the destination address indicating the Type-3- or Type-4-categorized network device. 
     Additionally, the routing information generation unit  102  sequentially the network device for which the routing information is generated, in such a manner that the packet route R 5  starting from the transmission source terminal device  3  leads to the destination terminal device  4 . When a network device for which the routing information is generated is categorized into Type-2 or Type-4, the routing information generation unit  102  generates the routing information for a network device for which the routing information is generated, which is selected after the Type-2- or Type-4-categorized network device, based on the source address indicating the Type-2- or Type-4-categorized network device. 
     According to the present embodiment, because, with the one-at-a-time search of the network devices on the route R 5  in the upstream direction and in the downstream direction, the routing information for each of the relay devices  2  and each of the servers  5   d  to  5   f  on the route R 5  can be generated, the time it takes to perform the generation processing can be shortened. 
     As described so far, the route setting device (the network management server)  1  according to the embodiments sets the routing information indicating the transmission source of the signal for each of the multiple network devices on the route over which the packet including the destination information (the destination address) indicating the destination and the transmission source information (the source address) indicating the transmission source is transferred, based on at least one of the destination address and the transmission source information. The route setting device  1  has a categorization unit (the server categorization unit)  103 , and a generation unit (the routing information generation unit)  102 . 
     Among the multiple networks devices (the relay devices  2  and the servers  5   d  to  5   f ), the categorization unit  103  detects the network devices (servers  5   d  to  5   f ) that change at last one of the destination information and the transmission source information on the signal that passes through the network devices (servers  5   d  to  5   f ), and categorizes the network devices by a type of the information that is changed. The generation unit  102  generates the routing information according to the result of the categorization by the categorization unit  103 . 
     With the configuration described above, among the network devices on the signal route, the network devices that change at least one of the destination information and the transmission source information on the signal are categorized by the type of the information that is changed. The routing information is generated according to the result of the categorization of the network device. For this reason, even though at least one of the destination information and the transmission source information on the signal is changed by a specific network device, the routing information is generated in such a manner that the routing information is consistent with the destination information or the transmission source information that is changed. 
     Therefore, with the route setting device  1  according to the embodiment, the suitable routing information can be set to the network device on the signal route. 
     Furthermore, a route setting method according to the embodiment is one in which the routing information indicating the transmission destination of the signal is set to each of the plurality of network devices on the route over which the packet including the destination information (the destination address) indicating the destination and the transmission source information (the source address) indicating the transmission source is transferred as the signal. The method of setting the route includes the following procedures. 
     A procedure (1): Among the network devices (the relay devices  2 , and the relay devices  5   d  to  5   f ) the network device is detected that changes at least one of the destination information and the transmission source information on the signal that passes through the network device. 
     A procedure (2): The network devices are categorized by the type of the information that is changed. 
     A procedure (3): The routing information is generated according to the result of the categorization. 
     The route setting method according to the embodiment includes the same configuration as the route setting device described above and thus accomplishes an operational effect of which contents is the same as those described above. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.