Abstract:
Disclosed herein is a VPN service with fully meshed virtual paths obtained with a smaller number of settings, thus facilitating expansion of the VPN service. This is attained by providing a communication device in a virtual private network (VPN) having a VPN accommodation function for connecting an intra-organization network or inter-organization network through the Internet.

Description:
This application is a continuation of international application number PCT/JP00/03980, filed Jun. 16, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a communication device having a VPN (virtual private network) accommodation function for use in the Internet. 
     BACKGROUND OF THE INVENTION 
     The Internet is a network enabling worldwide interconnection among users, the number of which is proliferating. In recent years, a variety of techniques have been developed actively to implement a VPN using the Internet. 
     The VPN, or virtual private network, is a service connecting intranets through the Internet. An example of a network configuration providing VPN is shown in  FIG. 1 . In this  FIG. 1 , a variety of network organizations including A-C are connected through routers  20 - 25  to a network  1  which is managed by a service provider. These routers are referred to as VPN edge routers. 
     Network  1  provided by the service provider generally interconnects with other networks provided by other service providers. As a VPN, a network for an organization A, as an example, is exclusively interconnected within this organization A only, separated from organizations B and C, through network  1  by the service provider. In other words, only each network inside organization A, B or C is logically interconnected. 
     Here, either a global address or a private address is used in an intranet whereas a global address is normally used in the Internet. The private address is an address to be applied in a network which is closed in the scope of an organization, and therefore an identical address may possibly be used in different organizations. 
     Accordingly, in an device accommodating VPN, it becomes necessary to provide the packet routing function for both Internet and intranet. Normally, in the direction from intranet to Internet, any packet for communication in an intranet is converted to a packet which can be processed in the Internet. In the direction from Internet to intranet, the packet format is converted in an opposite way to the above. 
     In the prior arts for performing such processing, as a first art, there is a method of either combining an IPv4 (Internet Protocol, version 4) header, the format of which includes a source address  26  and a destination address  27  shown in  FIG. 2 , with another IPv4 header, or combining with an IPv6 (Internet Protocol, version 6) header, the format of which includes a source address  28  and a destination address  29  shown in  FIG. 3 . Thus the headers are encapsulated as shown in  FIGS. 4A and 4B , respectively (corresponding to the Internet standard recommendation document, RFC 1853). Further, as a second prior art, there is a method of employing an MPLS (MultiProtocol Label Switching) shim header shown in  FIG. 5  to encapsulate both an IPv4 header and a shim header, as shown in  FIG. 4C . 
     Both of the aforementioned prior arts employ a method of establishing a packet path on the boundary between the Internet and the intranet (which is referred to as tunnel). 
     More specifically, the encapsulation technique shown in  FIG. 4  is realized by setting an IP address assigned at the boundary into an IP header for encapsulation. 
     Meanwhile, according to the encapsulation method by a shim header shown in  FIG. 4C  using a MPLS header shown in  FIG. 5 , the tunneling between both sides of the boundary is enabled by setting a unique value in a label field (Label) of the shim header on a link-by-link basis, and setting a virtual path by converting this value included in the label field in the device connecting the links. 
     However, according to the aforementioned prior arts, the number of settings in the device incorporating VPN becomes ‘the number of tunnels×2 (i.e. both end points of the tunnels)’. Therefore, there is a problem that a substantially large number of settings become necessary as the number of sites increases. 
     The number of the tunnels among N sites is (N−1)×2 in the case of a star connection network in which the number of tunnels is minimized. The number becomes N×(N−1) in case of a full mesh connection. If one site is added, it is necessary to add to two (2) settings in the case of star connection, or N settings in case of the full mesh connection. 
     In case of the star connection, the performance of a root node may cause a bottleneck. In addition, because a communication between nodes other than root has to be transmitted through the root, an identical packet has to be transmitted twice in the Internet. This raises a problem of additional bandwidth consumption, so use of full mesh connection is desirable. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a VPN service with fully meshed virtual paths obtained with smaller number of settings, thus facilitating expansion of VPN service. 
     This object is attained by providing a communication device in a virtual private network (VPN) having a VPN accommodation function for connecting an intra-organization network or inter-organization network in accordance with the present invention through the Internet. As a first embodiment of the communication device according to the present invention, the communication device includes; 
     a first means for generating a VPN address, a format of which includes both a VPN number for uniquely identifying a VPN in a certain scope and a closed address used in an organization or among organizations, either converting a packet header into a header having the above-mentioned VPN address or adding the above-mentioned VPN address to a packet header for transmission; and 
     a second means for on receiving the packet having a header of the VPN address format, either converting the received packet into a packet format equivalent to an original packet format or removing a header having VPN address format. 
     Further, as a second preferred embodiment according to the present invention, in the aforementioned first embodiment, the communication device further includes a processing means for on receiving a packet having the VPN address format, extracting a VPN number from the VPN address, comparing to a retained VPN number and discarding the packet when the comparison results in inconsistency. 
     Still further, as a third preferred embodiment, in the aforementioned first or second embodiment, a protocol used in an organization or among organizations is IPv4 (Internet Protocol, version 4), a packet having a VPN address format conforms to IPv6 (Internet Protocol, version 6), and an IPv6 header is either added to the IPv4 header or substituted for IPv4 header by the above-mentioned first means. 
     As a fourth preferred embodiment, in the aforementioned third embodiment, the VPN number is included in an NLA-ID (Next-Level Aggregation Identifier) field of the IPv6 aggregatable address format, and an IPv4 address is stored in an SLA-ID (Site-Level Aggregation Identifier) field and an Interface Identifier field. 
     Further, as a fifth preferred embodiment, in the aforementioned first or second embodiment, a protocol used in an organization or among organizations is IPv4, a packet having a VPN address format conforms to IPv6, and an IPv6 header is added to an IPv4 packet or deleted. 
     Still further, as a sixth preferred embodiment, in the aforementioned first or second embodiment, a protocol used in an organization or among organizations is IPv6, a packet having VPN address format conforms to IPv6, and a VPN address is generated using a VPN number and an SLA-ID (Site-Level Aggregation Identifier) field and an Interface Identifier field of the site-local address format or an aggregatable global address included in an address of an IP header used in an organization or among organizations, to perform address conversion. 
     Still further, as a seventh preferred embodiment, in the aforementioned first or second embodiment, VPN address in a VPN network for connecting an intra-organization network or an inter-organization network through the Internet is constituted of a Scope field indicating whether a VPN-ID is either a VPN which is closed inside an ISP or a VPN which is connected through a plurality of ISP, and a VPN number by which a VPN is uniquely identifiable in the Scope concerned. 
     Still further, as an eighth preferred embodiment, in either of the aforementioned embodiments, a VPN-ID is constituted of an IPv4 address as the VPN address. 
     Further scopes and features of the present invention will become more apparent by the following description of the embodiments with the accompanied drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of network configuration diagram constituting a virtual private network (VPN). 
         FIG. 2  shows an explanation drawing of an IPv4 header. 
         FIG. 3  shows an explanation drawing of an IPv6 header. 
         FIG. 4  shows a drawing illustrating header encapsulation. 
         FIG. 5  shows a diagram illustrating an MPLS shim header. 
         FIG. 6  shows a drawing illustrating the configuration concept of the present invention. 
         FIG. 7  shows a diagram illustrating the definition of VPN address. 
         FIG. 8  shows a typical embodiment of the present invention. 
         FIG. 9  shows an example of configuration of a VPN accommodation function portion shown in  FIG. 8 , illustrating an example of converting an IPv4 header into an IPv6 header. 
         FIG. 10  shows another exemplary configuration of the VPN accommodation function portion shown in  FIG. 8  in the example of converting an IPv4 header into an IPv6 header. 
         FIG. 11  shows a diagram illustrating an IPv6 address generated in the exemplary configurations shown in  FIGS. 8 ,  9 . 
         FIG. 12  shows an example of configuration of the VPN accommodation function portion shown in  FIG. 8 , illustrating an example of encapsulating an IPv4 packet with an IPv6 header. 
         FIG. 13  shows another example of configuration of the VPN accommodation function portion shown in  FIG. 8  in an example of encapsulating an IPv4 packet with an IPv6 header. 
         FIG. 14  shows an example of configuration of a VPN accommodation function portion shown in  FIG. 8 , illustrating an example of employing IPv6 in the intranet. 
         FIG. 15  shows another example of configuration of the VPN accommodation function portion shown in  FIG. 8  in an example of employing IPv6 in the intranet. 
         FIG. 16  shows a diagram illustrating a VPN address corresponding to the configurations shown in  FIGS. 14 ,  15 . 
         FIG. 17  shows a diagram illustrating an address used in a site-local address format. 
         FIG. 18  shows an example of an aggregatable global address. 
         FIG. 19  shows a diagram illustrating an example of a VPN address having a scope as an application example of the present invention. 
         FIG. 20  shows a diagram illustrating an example of a VPN address employing an IPv4 global address, as an application example of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiment of the present invention is described hereinafter referring to the charts and drawings, wherein like numerals or symbols refer to like parts. It is to be noted that these charts and drawings illustrating the embodiments are attached for explaining the present invention. The scope of the protection in the present invention is not to be limited to these illustrations. 
       FIG. 6  is a drawing illustrating the configuration concept of the present invention. In  FIG. 6 , a VPN accommodation function portion  32  according to the present invention is provided between an Internet router function portion  30  and a VPN router function portion  31 . 
     This VPN accommodation function portion  32  has a function of either converting a header of a packet for transmission into a header having a VPN address format, or encapsulating by including a header of the VPN address format. VPN accommodation function portion  32  also has a function of converting a packet to an identical format of an original packet or deleting a header having the VPN address format on receiving a packet having the VPN address format. 
     In the description of the present invention, a VPN address format shown in  FIG. 7  is defined. A header conforming to the address format is generated by adding an ID for identifying a VPN, i.e. a VPN number  34  to an IP address  33  for use in an intranet. 
     VPN number  34  is a number uniquely assigned in a certain region. This region may be the whole region of the Internet or a region of an Internet service provider (ISP). The address in the structure according to the present invention is distinguished from an address of other type by an FP (Format Prefix)  35 . 
     According to the present invention, when compared to the case of a full mesh network producing better efficiency, the number of settings required for performing VPN can be reduced to N in contrast to N×(N−1) in the prior art. For the reference, the number required for a star connection in the prior art is (N−1)×2. Namely, according to the present invention, a full mesh network can be obtained with the number of settings smaller than in the case of star connection in the prior art. 
     Also, in the case of adding a site in a full mesh network, according to the present invention, only one setting is need, in contrast to N settings required in the prior art. 
     In regard to processing for performing normal routing in the Internet, path establishment on a link-by-link basis is necessary in the method employing MPLS shim header. In contrast, according to the present invention, it is only necessary for route switching to use an existing protocol like RIP (Routing Information Protocol) widely in use having abundant operational results, as well as OSPF (Open Shortest Path First), IS-IS (Intermediate System-Intermediate System) or BGP (Border gateway Protocol), which are modified so as to conform to the Internet protocol IPv6. 
     Therefore, such a protocol as employed in MPLS which requires to set label value is not needed. Here, by combining the technique of encapsulating an IPv6 packet with an IPv4 header, it becomes not necessary that all network device of service provider conform to IPv6. 
     Now, a typical embodiment of the present invention is described hereafter referring to the example shown in  FIG. 8 , in which an IPv4 address (either global address or private address) is used in the intranet, and an IPv6 address is used in the Internet. 
     In the example shown in this  FIG. 8 , a router function portion (on Internet side)  30 , a router function portion (on VPN side)  31  and a VPN accommodation function portion  32  are provided as a VPN edge router  20 . A router  300  is a router function portion for connecting between VPN edge routers  20 . 
     VPN router function portion  31  has a routing table  501 , while router function portion  30  and router  300  have routing tables  502  and  503 , respectively. A destination address and a source address are described in an IPv4 packet header referring to these routing tables. 
       FIG. 9  is a configuration block diagram of VPN accommodation function portion  32  according to the present invention. 
     When packet communication is carried out from one site in a VPN to another site in the VPN, an IPv4 packet for use in the originating site is transmitted to VPN accommodation function portion  32  in VPN edge router  20 . 
     In VPN accommodation function portion  32 , IP addresses (both source address and destination address) included in the IPv4 packet are extracted in an IPv4 address extraction portion  320 . 
     Using a VPN-ID (number) being set in a VPN-ID retention portion  321  in advance for identifying the VPN of interest, a VPN address in the form of IPv6 for the Internet is generated by combining a VPN-ID  40  with an IPv4 address  41  in a VPN address generation portion  322 , as shown in  FIG. 11 . 
     The IPv6 VPN address thus generated is used for an IPv6 header address to be added in an IPv6 header addition portion  324  after an IPv4 header is deleted in an IPv4 header deletion portion  323 , as shown in  FIG. 9 . Thus the IPv4 header is converted into an IPv6 header. 
     The IPv6 packet thus converted is transferred to VPN accommodation function portion  32  in VPN edge router  20  to which the destination site is connected through the Internet  1 . This VPN accommodation function portion  32  is explained also referring to  FIG. 9 . In  FIG. 9 , an IPv6 packet is input to an IPv6 packet address extraction portion  325 . 
     The IPv6 address extracted in IPv6 address extraction portion  325  is input to VPN-ID/IPv4 address separation portion  326  to separate the IPv4 address. The separated IPv4 address is then used as an address in the IPv4 header to be added in IPv4 header addition portion  328  to a packet of which IPv6 header is deleted in an IPv6 header deletion portion  327 . Thus the packet concerned is returned to an IPv4 packet. 
       FIG. 6B  shows an aspect of header conversion between intranet and the Internet corresponding to the aforementioned description referring to  FIG. 9 . 
     In the above description, it may also be possible to check whether the VPN-ID of the packet input to VPN accommodation function portion  32  coincides with a predetermined VPN-ID. In such a case, VPN accommodation function portion  32  is configured as shown in  FIG. 10 . Namely, a comparison circuit  329  is additionally provided compared to the configuration shown in  FIG. 9 . 
     Using this comparison circuit  329 , a predetermined VPN number corresponding to the VPN of interest retained in VPN-ID retention portion  321  is compared to the VPN-ID separated in VPN-ID/IPv4 address separation portion  326 . 
     As the result of this comparison, if the VPN numbers are different, the packet is discarded in an IPv4 header addition portion because the packet has no relation with the VPN of interest. This enables to prevent any packet from flowing in or flowing out from/to a different VPN, thus enabling to improve security. 
     Further, as a result of VPN accommodation function portion  32  outputting a route including up to an IPv4 prefix shown in  FIG. 11 , routing by IPv6 is carried out according to routing table  502  shown in  FIG. 8 . 
     In the above description, a case of converting an IPv4 header into an IPv6 header is shown. However, in place of this conversion processing, it is also possible to employ the aforementioned encapsulation method. 
     In such a case, the configurations of VPN accommodation function portion  32  shown in  FIGS. 9 ,  10  are replaced by the configurations shown in  FIGS. 12 ,  13 , respectively. In the configurations shown in  FIGS. 12 ,  13 , IPv4 header deletion portion  323  and IPv4 header addition portion  328  become unnecessary. 
     Namely, an IPv6 VPN address generated in VPN address generation portion  322  is added to an IPv4 packet in IPv6 header addition portion  324  to encapsulate. Therefore, IPv4 header deletion portion  323  is not required in  FIGS. 12 ,  13 . 
     Also, in  FIGS. 12 ,  13 , the IPv6 address included in a signal input from the Internet is extracted in IPv6 address extraction portion  325 , while the IPv4 address remains unchanged. Therefore, IPv4 address addition portion  328  is not required also. 
     This situation is shown in  FIG. 6C , taking the header conversion shown in  FIG. 4A  as an example. 
     The foregoing description is based on the intranet employing IPv4. When IPv6 is employed in the intranet, a similar operation can be achieved by handling as an IPv4 address a subnet ID, or a data under a site prefix, included in a site-local address (i.e. a local address not connected to the Internet). 
       FIGS. 14 ,  15  show examples of configuration block diagram of VPN accommodation function portion  32  when IPv6 is used in the intranet, which respectively correspond to  FIGS. 9 ,  10 . As shown in  FIGS. 14 ,  15 , IPv6 address extraction portions  330 ,  332  and address substitution portions  331 ,  333  are provided for handling IPv6 addresses. 
       FIG. 16  shows an explanation drawing of a VPN address corresponding to the configurations shown in  FIGS. 14 ,  15 . In these  FIGS. 14 ,  15 , a VPN address is generated by the address conversion using a VPN-ID  40  shown in this  FIG. 16 , a subnet ID/SLA  42  in the site-local address format or the aggregatable global address format and an Interface ID field  43  in an IP header address used in an organization or among organizations. 
     This address conversion is performed in address substitution portion  331  shown in  FIGS. 14 ,  15 . 
     Here, an exemplary address in the site-local address format is shown in  FIG. 17 . In this  FIG. 17 , field I denotes a global address, and field II denotes an address in an organization having a subnet ID and an interface ID. 
       FIG. 18  shows an example of an aggregatable global address, in which field I includes global address, and field II includes Site-Level Aggregation ID and Interface ID. 
     Further, as an application of the present invention, it is possible to use VPN address shown in  FIG. 19 . Here,  FIG. 19A  shows a case of employing IPv4 in the intranet, while  FIG. 19B  shows a case of employing IPv6 in the intranet. 
     In  FIG. 19 , there is provided a scope field  44  which stores a flag indicating whether or not VPN-ID  45  is a VPN closed in a service provider. In the case of closed VPN in the service provider, it becomes possible for the service provider to assign VPN-ID  45 . 
     As another application of the present invention, a VPN address shown in  FIG. 20  may be used.  FIG. 20A  shows the case of IPv4 employed in the intranet, while  FIG. 20B  shows the case of IPv6 employed in the intranet. 
       FIG. 20  shows an example that using an IPv4 global address as a VPN-ID inevitably results in obtaining a unique VPN-ID  45 . For example, using an IPv4 global address assigned to an organization produces a unique address. At the same time, this makes it unnecessary to manage for maintaining VPN-ID  45  uniquely. 
     INDUSTRIAL APPLICABILITY 
     As having been described, according to the present invention, a VPN service can be achieved with a remarkably reduced number of settings compared to other methods. This brings about less possibility of setting errors or operational mistake and therefore an operator may provide the service safely. 
     Because of the reduced number of settings against end user demands, the service may be provided in a short preparation period. In addition, according to the present invention, a simple functional addition in an edge router is only required. For routers on users&#39; side and routers not located on user boundary, routers for general use may be used without need of modification, thus facilitating installation. 
     Further, when considering multi-vender connection using routers of multi-venderproducts, the method requires only a unicast routing protocol of general use having sufficient actual operation results, such as RIP, OSPF, IS-IS or BGP. Any peculiar protocol such as MPLS label distribution protocol is not necessary. Therefore, multi-vender connection may be achieved easily. 
     Moreover, the service may be introduced even when addresses assigned in an organization is overlapped. 
     To conclude, the present invention brings about a large effect, greatly contributing for the expansion of VPN services on the Internet. 
     The foregoing description of the embodiments is not intended to limit the invention to the particular details of the examples illustrated. Any suitable modification and equivalents may be resorted to the scope of the invention. All features and advantages of the invention which fall within the scope of the invention are covered by the appended claims.