Source: http://www.google.com/patents/US7085270?dq=6,274,924
Timestamp: 2015-01-31 00:26:11
Document Index: 294176894

Matched Legal Cases: ['art 11', 'art 13', 'art 11', 'art 13', 'art 11', 'art 13', 'art 11', 'art 13', 'art 11', 'art 11', 'art 13', 'art 11', 'art 13', 'art 11', 'art 13', 'art 11', 'art 13', 'art 11']

Patent US7085270 - Address translation method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA translator includes a unit for communication with a DNS-ALG. The DNS-ALG detects a DNS query to a destination terminal, and performs once translation to IPv6. The DNS-ALG translates a destination temporary IPv6 address, in which a real address of IPv4 acquired from a DNS server of the destination terminal...http://www.google.com/patents/US7085270?utm_source=gb-gplus-sharePatent US7085270 - Address translation methodAdvanced Patent SearchPublication numberUS7085270 B2Publication typeGrantApplication numberUS 10/061,331Publication dateAug 1, 2006Filing dateFeb 4, 2002Priority dateSep 11, 2001Fee statusLapsedAlso published asDE60238659D1, EP1303106A2, EP1303106A3, EP1303106B1, US7630374, US20030048804, US20060227780Publication number061331, 10061331, US 7085270 B2, US 7085270B2, US-B2-7085270, US7085270 B2, US7085270B2InventorsHidenori Inouchi, Yukiko Takeda, Masaya Hayashi, Keisuke Takeuchi, Takamitsu SenouOriginal AssigneeHitachi, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (4), Non-Patent Citations (9), Referenced by (15), Classifications (30), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetAddress translation methodUS 7085270 B2Abstract A translator includes a unit for communication with a DNS-ALG. The DNS-ALG detects a DNS query to a destination terminal, and performs once translation to IPv6. The DNS-ALG translates a destination temporary IPv6 address, in which a real address of IPv4 acquired from a DNS server of the destination terminal is added with a virtual IPv6 prefix, to a destination temporary IPv4. The IPv6-based DNS-ALG cooperates with the translator to permit alleviation of processing load on the DNS-ALG and reduction in capacity of a translation table of large capacity. A technique is disclosed which, with the above construction, can permit mutual connection among a plurality of VPN's without exchanging the existing VPN's.
BACKGROUND OF THE INVENTION The present invention relates to techniques of mutually connecting networks conforming to the same protocol or networks conforming to different protocols.
For example, a method of using Twice NAT (Network Address Translation) (see http://www.ietf.org/rfc/rfc2663.txt, pp. 12�13) or a method of using a tunnel technique (see http://www.ietf.org/rfc/rfc2663.txt, p. 22) has been known as a technique of mutually connecting private networks through Internet to exhibit them as one VPN (Virtual Private Network). In any method, header information of an IP packet based on IPv4 and that of an IP packet also based on IPv4 are mutually translated in essentiality.
Each of the above-described examples is a technique used when a communication protocol of a network to which a terminal belongs is the same as that of a network to which a communication partner terminal belongs. When a communication protocol of a network to which a terminal belongs differs from that of a network to which a communication partner terminal belongs, NAT-PT (see http://www.ietf.org/rfc/rfc2766.txt, pp. 6�18, and http://www.ietf.org/rfc/rfc2765.txt, pp. 9�22) and SOCKS64 (see http://www.ietf.org/rfc3089.txt), for instance, have been known as a translation technique of connecting a network using, for example, IPv4 as protocol (hereinafter referred to as an �IPv4 network�) and a network using, for example, Internet Protocol version 6 as protocol (hereinafter referred to as an �IPv6 network�).
Essentially, in either method, the format of IP packet is mutually translated between IPv4 and IPv6. For example, a translation between IPv4 address and IPv6 address is carried out. A unit for performing this translation will hereinafter be called a �translator�. In the translator, for the sake of translation, correspondence relation between IPv4 address and IPv6 address must be prepared and held in advance of translation. When the correspondence relation is prepared dynamically each time that communication occurs, name resolution of DNS (Domain Name System) is used as a trigger for the preparation (see Internet RFC dictionary, published by ASCII, pp. 323�329).
The DNS is a system for translating a name (character string) comprehensible to human such as a URL of Web to an IP address. Operation to translate the name to the IP address will hereinafter be called �name resolution�. Today, almost all the applications on Internet acquire an IP address of a communication partner by utilizing this DNS.
SUMMARY OF THE INVENTION An object of the present invention is to permit mutual communication between two terminals even when, under a condition that a communication protocol of a network to which a terminal belongs is the same as that of a network to which a communication partner terminal belongs, address spaces of both the networks collide with each other.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing mutual connection construction of VPN's through an IP network according to a first embodiment of the invention;
DETAILED DESCRIPTION OF THE EMBODIMENTS A first embodiment of the present invention will be described with reference to the accompanying drawings.
An instance where a terminal 4 a of VPN 5 a communicates with a terminal 4 c of VPN 5 c in FIG. 1 will be described in accordance with the sequence shown in FIGS. 14 and 15. Upon initiation of communication, the terminal 4 a makes a DNS query to a DNS server 3 a in order to obtain an address of name (assumed to be �hostC�) of the terminal 4 c (step 101). A packet format of the DNS query is shown in FIG. 6. The name hostC and the type �A� of resource record are described in QNAME 421 and QTYPE 422, respectively, in FIG. 6.
If the DNS-ALG 2 a does not know the IP address corresponding to the name hostC, it starts a processing routine shown in FIGS. 12 and 13. When QTYPE of the DNS query is �A�, the DNS-ALG 2 a modifies the QTYPE to �AAAA� (steps 62 and 103). The DNS-ALG 2 a sends the modified DNS query to the next DNS server 8 (steps 63 and 104), and waits for a DNS response (step 64). The DNS server 8 sends a DNS query to the next DNS server, that is, DNS-ALG 2 b (step 105). In case the DNS-ALG 2 b does not know the IP address corresponding to the name hostC, it starts the processing routine 60 shown in FIGS. 12 and 13. When QTYPE of the DNS query is �AAAA�, the QTYPE is modified to �A� (steps 81 and 106). The DNS-ALG 2 b sends the modified DNS query to the next DNS server 3 c (steps 82 and 107), and waits for a DNS response (step 83). The DNS server 3 c responds an IPv4 address �c� corresponding to the name hostC (steps 84 and 108).
FIG. 7 shows a format of a DNS response packet from the DNS server 3 c. Detailed formats of 43, 44 and 45 in FIG. 7 are shown in FIG. 8. The name hostC and the IP address �c� are described in NAME 51 and RDATA 54, respectively.
With reference to FIG. 14, the DNS-ALG 2 b translates the IPv4 address �c� to an IPv6 address �γ+c� for the sake of subsequent translation. The IPv6address is constructed of a virtual IPv6 prefix (γ) assigned to the VPN 5 c and the IPv4 address (c) (step 109). This address will hereinafter be called a �destination temporary IPv6 address�. The DNS-ALG 2 b modifies TYPE 52 of the DNS response from �A� to �AAAA�, and sends a DNS response having �γ+c� set in RDATA 54 to the DNS server 8 (steps 85 and 110). The DNS server 8 responds to the DNS-ALG 2 a by the destination temporary IPv6 address �γ+c� corresponding to the name hostC (steps 65 and 111).
The DNS-ALG 2 a translates this IPv6 address �γ+c� to the IPv4 address c′ for the sake of subsequent translation (step 112). This IPv4 address is a temporary address for the name hostC, and is selected from a set of IP addresses not used by the VPN 5 a. This address will hereinafter be called a �destination temporary IPv4 address�. The DNS-ALF 2 a modifies TYPE 52 of the DNS response from �AAAA� to �A�, and sends a DNS response having the destination temporary IPv4address �c′� set in RDATA 54 to the terminal 4 a via the DNS server 3 a (steps 66, 115 and 116). In this phase, a translation rule for making the correspondence between γ+c and c′ is prepared which in turn is sent to the translator 1 a (steps 67 and 113). The translator 1 a stores the translation rule in a VPN#1 translation information table 510 inside the translation information memory part 11, and sends a response to the DNS-ALG 2 a (step 114).
The terminal 4 a receiving the DNS response starts to send IP packets to the terminal 4 c. A destination address of these packets is c′, and their source address is an IPv4 address �a� of the terminal (step 131).
As the packet arrives, the translator 1 a sends it to the data packet translation�processing part 13. Here, the retrieval is performed to the translation information memory part 11 on the basis of a circuit number through which the data is received, and the destination address c′. Then, since the entry prepared in the step 113 is found in the translation information table 510, the destination address �c′� is translated to �γ+c�. The source address is rewritten to a source temporary IPv6 address �α+a� which is added with a virtual IPv6 prefix α corresponding to the circuit number through which the data is received (step 132). The translator 1 a sends a packet in which �γ+c� and �α+a� are set in the destination and source addresses, respectively (step 133). A translator 1 b sends this packet to the data packet translation�processing part 13. Here, the virtual IPv6 prefix γ is deleted from the destination address. In order to uniquely identify the source address �α+a� inside the VPN 5 c, it is translated to an IPv4 address �a1′�. This IPv4 address is a temporary address for the source address �α+a�, and is selected from a set of IP addresses not used inside the VPN 5 c. Hereinafter, this address will be called a �source temporary IPv4 address�.
The translator 1 b prepares a translation rule for making the correspondence between �α+a� and �a1′�, and stores it in the VPN#3 translation information table 530 of the translation information memory part 11 (step 134).
The terminal 4 c receives a packet having the destination and source addresses set with �c� and �a1′�, respectively (step 135). The terminal 4 c sends an IP packet having the destination and source addresses set with �a1′� and �c�, respectively, to the terminal 4 a (step 136). As this packet arrives, the translator 1 b sends it to the data packet translation�processing part 13. Here, retrieval is performed to the translation information memory part 11 on the basis of a circuit number through which the data is received, and the destination address �a1′�. Then, since the entry prepared in the step 134 is found in the translation information table 530, the destination address �a1′� is translated to �α+a�. The source address is rewritten to a source temporary IPv6 address �γ+c� which is added with a virtual IPv6 prefix γ corresponding to the circuit number through which the data is received (step 137). The translator 1 b sends a packet with �α+a� set in the destination address and �γ+c� set in the source address (step 138).
As this packet arrives, the translator 1 a sends it to the data packet translation�processing part 13. Here, the virtual IPv6 prefix is deleted from the destination address. Retrieval is performed to the translation information memory part 11 on the basis of the virtual IPv6 prefix �α� of destination address and the source address �γ+c�. Then, since the entry prepared precedently is found in the translation information table 510, the source address is translated from �γ+c� to �c′� (step 139).
The terminal 4 a receives the packet having the destination and source addresses set with �a� and �c′�, respectively (step 140).
FIG. 16 shows a network construction according to the second embodiment of the invention. In comparison with FIG. 1, the network construction of FIG. 16 is characterized in that �communication between the DNS server 3 in the VPN 5 and the DNS-ALG 2 is carried out via the translator 1�, and in that �in mutual communication between VPN's, the DNS server to which the DNS-ALG 2 makes a query next is set with another IPv6 address inside the DNS-ALG 2�.
In the present embodiment, the DNS-ALG 2 is a multi-home node having an IPv6 address in correspondence to a VPN connected to the translator 1. In a DNS-ALG 2 a according to the present embodiment, when a DNS server queried next does not exist in a VPN that has sent a DNS query, another IPv6 address of the DNS-ALG 2 a is stored as address information of the DNS server queried next. If a DNS server queried next exist in a VPN that has sent a DNS query, a temporary IPv6 address of the DNS server present in the VPN is stored as address information of the DNS server queried next. This temporary IPv6 address is constructed of �a virtual prefix and an IPv4 address assigned to the DNS server in each VPN�.
FIG. 17 mainly differs from FIG. 14 in that �the translator 1 a translates an address of a packet containing a message of the DNS�, and in that �the IPv6 address of the DNS-ALG 2 a differs for individual VPN's�.
A detailed description will be given with reference to FIGS. 17 and 18. The terminal 4 a makes a DNS query to a DNS server 3 a in order to resolve a name (assumed to be �hostB�) of the terminal 4 b (step 151). The DNS server 3 a (having an IPv4 address of �da4�) does not know an IP address corresponding to the name hostB, so that it makes a DNS query to the next DNS server (DNS-ALG 2 a having a temporary IPv4 address �pa4�) (step 152).
The TR-O of the translator 1 a detects a packet containing a message of the DNS, and translates the packet (step 153). A destination address is translated to an IP v6 address �α6� for the VPN 5 a in the DNS-ALG 2 a by using DNS-ALG address translation information provided for the translator 1 a. A source address is added with a virtual IPv6 prefix �α� for the VPN 5 a by referring to the virtual prefix management table 300. The TR-O of the translator 1 a sends a DNS query packet for which the address is translated, to the DNS-ALG 2 a (step 154).
When the DNS-ALG 2 a does not know the IP address corresponding to the name hostB, it modifies the DNS query through the aforementioned processing routine 60 (step 155), and transfers the DNS query (step 156). A destination for which the DNS query is forwarded is set with a different IPv6 address (IPv6 address �βb� for the VPN 5 b) assigned to the DNS-ALG 2 a. If the DNS-ALG 2 a receiving the DNS query destined for the IPv6 address �β6� for the VPN 5 b does not know the IP address corresponding to the name hostB, the DNS query modified through the aforementioned processing routine 60 is sent to the next DNS server 3 b (having a temporary IPv6 address �β+db4� (steps 157 and 158).
The TR-T of the translator 1 a detects a packet containing a message of the DNS, and translates the packet (step 159). The virtual prefix β is deleted from the destination address. The source address is translated to a temporary IPv4 address �pb4� corresponding to the IPv6 address �β6� of the DNS-ALG 2 a for the VPN 5 b by using the DNS-ALG address translation information provided for the translator 1 a. The TR-T of the translator 1 a sends the packet for which the address is translated, to the DNS server 3 b (step 160).
The DNS server 3 b responds an IPv4 address �b� for the name hostB (step 161). The TR-T of the translator 1 a detects a packet containing a message of the DNS, and translates the packet (step 162). A virtual prefix β corresponding to the VPN 5 b is added to the source address. The destination address is translated from �pb4� to �β6� by using the DNS-ALG address translation information provided for the translator 1 a. The TR-T of the translator 1 a sends the packet for which the address is translated, to the DNS-ALG 2 a (step 163).
The DNS-ALG 2 a adds the virtual prefix β to the IPv4 address �b� for the name hostB so as to rewrite the address �b� to �β+b� (step 164).
The DNS-ALG 2 a sends a DNS response having its RDATA set with �β+b�, to the IPv6 address �α6� for the VPN 5 a of the DNS-ALG 2 a (step 165).
The DNS-ALG 2 a receiving the DNS response translates the IPv6 address �β+b� to a destination temporary IPv4 address �b′� (step 166). This IPv4 address is a temporary address corresponding to the name hostB, and is selected from a set of IP addresses not used by the VPN 5 a. The DNS-ALG 2 a sends the destination temporary IPv4 address �b′� for the name hostB to the terminal 4 a via the DNS server 3 a (steps 169, 171 and 172). When detecting the DNS response sent in the step 169, the translator 1 a translates the packet (step 170). The virtual prefix α is deleted from the destination address. The source address is translated from �α6� to �pa4� by using the DNS-ALG address translation information provided for the translator 1 a. The TR-O of the translator 1 a sends the packet for which the address is translated, to the DNS 3 a (step 171).
The DNS-ALG 2 a prepares a translation rule for making the correspondence between �β+b� and �b′�, and sends it to the translator 1 a (step 167). The translator 1 a stores the translation rule in the VPN#1 translation information table 510 of the translation information memory part 11, and sends a response to the DNS-ALG 2 a (step 168).
FIG. 18 mainly differs from FIG. 15 in that �the translator 1 translates the destination address and the source address (step 182), causes a packet to undergo routing inside the translator (step 184), and again translates the destination address and the source address (step 185)�.
The terminal 4 a starts to send IP packets to the terminal 4 b. The destination address of these packets is b′, and their source address is the IPv4 address �a� of the terminal (step 181).
As the packet arrives, the translator 1 a sends it to the data packet translation�processing part 13. Here, retrieval is performed to the translation information memory part 11 on the basis of a circuit number through which the data is received, and the destination address b′. Then, since the entry prepared in the step 167 is found in the translation information table 510, the destination address is translated from �b′� to �β+b�. The source address is added with the virtual IPv6 prefix α corresponding to the circuit number through which the data is received (step 182).
The translator 1 a sends a packet in which �β+b� is set in the destination address and �α+a� is set in the source address (step 183). This packet is subjected to routing inside the translator 1 a (step 184).
The translator 1 a sends this packet to the data packet translation�processing part 13. Here, the virtual IPv6 prefix β is deleted from the destination address. The translator 1 a translates the source address �α+a� to the IPv4 address �a�. This IPv4 address is a temporary address corresponding to the IPv6 address �α+a�, and is selected from a set of IP addresses not used by the VPN 5 b. The translator 1 a prepares a translation rule for making the correspondence between �α+a� and �a′�, and stores it in the VPN#2 translation information table 520 of the translation information memory part 11 (step 185).
The terminal 4 b receives a packet having �b� and �a′� set in the destination and source addresses, respectively (step 186).
The terminal 4 b sends to the terminal 4 a a packet having �a′� and �b� set in the destination and source addresses (step 187).
As this packet arrives, the translator 1 a sends it to the data packet translation�processing part 13. Here, retrieval is performed to the translation information memory part 11 on the basis of a circuit number through which the data is received, and the destination address �a′�. Then, since the entry prepared in the step 185 is found in the translation information table 520, the destination address is translated from �a′� to �α+a�. The source address is added with a virtual IPv6 prefix �β� corresponding to the circuit number through with the data is received (step 188).
The translator 1 a causes the packet having �α+a� and �β+b� set in the destination and source addresses, respectively, to undergo routing inside the translator 1 a (steps 189 and 190).
The translator 1 a sends this packet to the data packet translation�processing part 13. The virtual IPv6 prefix α is deleted from the destination address �α+a�. When retrieval is performed to the translation information memory part 11 on the basis of the destination virtual IPv6 prefix α and the source address �β+b�, the entry prepared in advance is found in the translation information table 510, so that the source address is translated from �β+b� to �b′� (step 191).
The terminal 4 a receives a packet having �a� set in the destination address and �b′� set in the source address (step 192).
FIG. 19 shows the network construction according to the third embodiment of the invention. In comparison with FIG. 16, the present embodiment is characterized in that �a plurality of VPN's share a DNS-ALG in common�, and in that �a plurality of translators share the DNS-ALG in common�. A DNS-ALG 2 a in the present embodiment has the function of separately setting transfer destinations for name resolution in respect of individual domains. Specifically, the correspondence relation between a domain name of each VPN and a temporary IPv6 address of a DNS server existing in the VPN is managed as address information of a DNS sever to be queried next. This temporary IPv6 address is constructed of �a virtual prefix and an IPv4 address assigned to the DNS server in each VPN�.
The DNS-ALG 2 a has, in place of the processing routine 60, the function of performing name resolution with �A� and �AAAA� regardless of the value of QTYPE of name hostB. A translator 1 in the present embodiment has, in addition to the function of the translator 1 in the first embodiment, DNS-ALG address translation information, a function of monitoring a packet containing a message of a DNS, and a function of translating an address of the packet containing a message of a DNS.
An instance will now be described in which a terminal 4 a existing in a VPN 5 a resolves a name of a terminal 4 b existing in a VPN 5 b. In the present embodiment, a translator 1 a holds the correspondence relation between the IPv6 address �alg6� of the DNS-ALG 2 a and the temporary IPv6 assigned to the DNS-ALG 2 a for the sake of identifying the DNS-ALG inside the VPN in respect of the individual VPN's.
The terminal 4 a makes a DNS query in order to obtain an address of the name (assumed to be �hostB�) of the terminal 4 b. A DNS server 3 a cannot resolve the name hostB, and therefore it sends the DNS query to the next DNS server (DNS-ALG 2 a). A packet header of this DNS query has the destination address set with a temporary IPv4 address �pa4� assigned to the DNS-ALG 2 a by means of the VPN 5 a, and has the source address set with an IPv4 address �da4� of the DNS 3 a. When detecting this DNS query, the translator 1 a translates the destination address from �pa4� to an IPv6 address �alg6� of the DNS-ALG 2 a by referring to the DNS-ALG address translation information. The source address is added with an IPv6 prefix α for the VPN 5 a so as to be rewritten to �α+da4�.
When the DNS-ALG 2 a receiving the aforementioned DNS query does not know an IP address for the name hostB, it makes a query to the next DNS server. In this phase, for the purpose of resolving the name hostB, a temporary IPv6 address �β+db4� is set as the DNS server to be queried next. The �β+db4� is a temporary IPv6 address of a DNS server 3 b of the VPN 5 b. The DNS-ALG 2 a sends the DNS query to the DNS server 3 b, and waits for a response. This DNS query has the IPv6 address �alg6� of the DNS-ALG 2 a and the �β+db4� set in the source and destination addresses, respectively.
The translator 1 a detects a packet of the aforementioned DNS query, and translates the source address (i.e., the IPv6 address �alg6� of the DNS-ALG 2 a) to the temporary virtual IPv4 address �pb4� for identifying the DNS-ALG 2 a inside the VPN 5 b by using the DNS-ALG address translation information for each VPN. In the destination address, the prefix β is deleted so that �β+db4� may be rewritten to �db4�.
The DNS server 3 b responds to the DNS-ALG 2 a with the IPv4 address �b� for the name hostB.
The DNS-ALG 2 a rewrites the IPv4 address �b� to the destination temporary IPv6 address �β+b� for the sake of subsequent translation, and thereafter translates �β+b� to the destination temporary IPv4 address �b′�. The IPv4 address �b′� is a temporary address for the name hostB, and is selected from a set of IP addresses not used by the VPN 5 a. The DNS-ALG 2 a sends the destination temporary IPv4 address �b′� for the name hostB to the terminal 4 a via the DNS server 3 a. The subsequent processing flow is the same as that in the second embodiment.
FIG. 20 shows the network construction according to the fourth embodiment of the invention. In comparison with FIG. 16, the network construction of FIG. 20 is characterized in that �an L2SW 7 multiplexes circuits 17 a and 17 b of a translator provided for individual VPN's 5�. The L2SW 7 in the present embodiment has a VPN management table 320 shown in FIG. 21.
FIG. 22 shows a network construction according to the fifth embodiment of the invention. In comparison with FIG. 16, the network construction of FIG. 22 is characterized in that �a plurality of VPN's 5 a and 5 b are accommodated by a circuit 17 a of a translator 1 a�, and in that �the translator 1 a includes, in place of the virtual prefix management table 300 shown in FIG. 9, a virtual prefix management table 310 shown in FIG. 10, and identifies a VPN from L2 information�.
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