JP2013192156A - Relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with a case of communication that passes through a network in which either IPv4 or IPv6 is unavailable, and to clear a dual stack problem with a format conforming to a protocol other than TCP, and to perform communication using an optimal version when IPv4 and IPv6 are compatible.SOLUTION: When a relay device 11 having a DNS-proxy function unit 21 receives an IP address from a DNS server 13 through a DNS request, the relay device 11 confirms responsiveness of a Web server 14 to the IP address for both cases of IPv4 and IPv6, without instantly returning the received IP address to a user terminal 12. The relay device 11 returns to the user terminal 12 an IP address in which response measurement is successful or an IP address of a version having more excellent response quality.

Description

  The present invention relates to a DNS-proxy device used in a mixed environment of IPv4 and IPv6.

  With the widespread use of IPv6, servers that have both conventional IPv4 and IPv6 IP addresses are increasing. However, there are still many networks that only support IPv4, and there are many environments in which responsiveness cannot be guaranteed only with IPv6.

  FIG. 5 shows a conceptual diagram of this environment, and FIG. 6 shows a conventional communication sequence in this environment. When the user terminal 12 accesses an address using FQDN (Fully Qualified Domain Name) with an Internet browser or the like, the user terminal 12 must acquire an IP address corresponding to the FQDN. For this reason, first, the user terminal 12 transmits a DNS request to the relay apparatus 11 having the DNS-proxy function (S11). Actually, the number of DNS requests is not one, but an inquiry about both IPv4 and IPv6 is made so that both IPv4 and IPv6 can be handled. Since which of IPv6 and IPv4 has priority depends on the environment, it is not particularly determined which DNS request for IPv4 or IPv6 is transmitted first.

  The relay device 11 having the DNS-proxy function relays the DNS request from the user terminal 12 and transmits it to the DNS server (S12). The DNS server 13 that has received the DNS request returns an IP address corresponding to the requested FQDN by the information it has or by an inquiry to another DNS cache server (S13). This is done for both IPv4 and Ipv6. The relay device 11 sequentially returns the IP address returned from the DNS server 13 to the user terminal 12 (S14).

  In the figure, access is made to the same DNS server 13, but IPv4 and IPv6 may be separate servers. In particular, in the case of separate servers, it is often not constant whether the DNS request of IPv4 or IPv6 is returned first.

  Here, it is assumed that name resolution for IPv6 is performed first. Then, the user terminal 12 starts connection with an IPv6 IP address (S21). At this time, the relay device 11 forwards the connection request without particularly investigating (S22). However, even if the network 15a corresponding to both IPv4 and IPv6 can pass through, the network 16 that supports only IPv4 cannot pass communication at the IP address by IPv6, and the connection fails here ( S23). If the connection is not successful, the user terminal 12 repeatedly transmits a connection request several times, but this time appears to the user in a connection waiting state (S24).

  When the predetermined number of failures has occurred, it is determined that connection with IPv6 is impossible, and a connection request using the IPv4 IP address that arrived earlier is made again (S25). If it is a connection request based on IPv4, it passes through the above IPv4 only network 16 and also passes through the network 15b corresponding to both IPv4 and IPv6, and the connection with the web server 14 is successful (S26). .

  However, since the user waits in step S24 among these, the response of the line seems to be lowered.

  In addition, cases where IPv6 and IPv4 are opposite to the above conceptual diagram and sequence diagram may occur. That is, after the IPv4 address is depleted, the network area that cannot be accessed by IPv4 and can be accessed only by IPv6 starts to increase. In this case, when the DNS request in IPv4 is first resolved, there is a case where connection fails because IPv4 cannot be reached and connection must be made again in IPv6.

  Several methods have been studied for the IPv6 / IPv4 dual stack problem. For example, the relay device 11 sends out a TCP resetter to forcibly block IPv6 communication and promptly shift to IPv4. As disclosed in Patent Document 1, the relay device 11 is originally configured with DNS in IPv6. A method of invalidating all DNS requests to the server 13 can be mentioned.

JP 2009-130501 A

  However, fallback to IPv4 by the TCP resetter, although it can reduce the waiting time to some extent, has not been eliminated, so it has not been a fundamental solution. In addition, since it only supports the TCP protocol, there was no versatility to other protocols such as UDP.

  Furthermore, since the method of Patent Document 1 cannot resolve all IPv6 DNS names, there is a problem that communication cannot be performed with a server that supports only IPv6 addresses.

  Furthermore, in the conventional method, if the connection between one of the IPv4 and the IPv6 is successful, even if the other version of the IP can communicate at a higher speed, the communication continues with the same version of the IP. The user's use efficiency is poor, and inconveniences that cannot be experienced by the user may be substantially given.

  Therefore, the present invention can cope with a case where a network that cannot use either IPv6 or IPv4 can be used, can solve the dual stack problem in a format compatible with protocols other than TCP, and is compatible with both IPv4 and IPv6. It is an object of the present invention to improve user convenience by enabling communication with a version with good response quality even in such a case.

In the present invention, when the relay device 11 having the DNS-proxy function unit 21 relays a DNS request and receives an IP address from the DNS server 13, it does not promptly return it to the user terminal 12.
For both IPv4 and IPv6, the relay device 11 actually connects to the web server 14 of the IP address and measures the responsiveness, and the responsiveness measurement result confirms the responsiveness. The above-mentioned problem has been solved by returning to the user terminal 12 with priority.

  That is, the relay apparatus 11 has a responsiveness measuring unit 22 for measuring and confirming responsiveness with respect to the web server 14 together with the DNS-proxy function unit 21. When the DNS-proxy function unit 21 receives an IP address from the DNS server 13 for both IPv4 and IPv6, the DNS-proxy function unit 21 temporarily passes the IP address to the responsiveness measuring unit 22 without returning it to the user terminal 12. . The responsiveness measuring unit 22 actually communicates with the web server 14 using each version of IP and measures the responsiveness. In the measurement, there are a method of simply sending a ping and a method of actually performing TCP 3-way-handake. When the responsiveness measurement unit 22 confirms that the connection and response have actually been made, the responsiveness measurement result is passed to the DNS-proxy function unit 21, and the version of the IP whose response measurement result has confirmed the connection The address is sent to the user terminal 12. As a result, even if there is a network that supports only IPv4 or IPv6 between the web server 14, the user terminal 12 can connect with the IP address of the version whose responsiveness could actually be measured. After receiving this, it is not necessary to try to construct a session that is not actually connected, and the waiting time that the user actually feels can be almost eliminated.

  If there is a network that supports only IPv4 or IPv6 with the web server 14, only the response with the corresponding version of the IP address will be returned. The returned version of the IP address is sent to the user terminal 12 as a version that allows session construction with better communication quality.

  Further, not only the comparison of required time, but also the IP address of the version with the lower error rate may be preferentially passed to the DNS-proxy function unit as having excellent response quality.

  According to the present invention, in an environment where IPv4 and IPv6 coexist, session construction is performed through a path that can be reliably connected. Therefore, it is not possible to wastefully attempt to construct a session with a version of IP that cannot be communicated and to wait for the user. Regardless of the version that can be connected, the version that can respond to the subsequent connection request at a higher speed with the web server can be selected. Response can be improved throughout the session.

Functional block and configuration diagram showing an example of an embodiment of the present invention The sequence diagram which shows the 1st example of embodiment of this invention Flow diagram when measuring responsiveness with ping and TCP Sequence diagram showing a second example of the embodiment of the present invention Conceptual diagram of an example environment in which a network that only supports IPv4 is present Sequence diagram showing an example of session establishment in the environment of FIG.

Hereinafter, the present invention will be described in detail with examples of specific embodiments.
FIG. 1 is a conceptual diagram of functional blocks of the relay device 11 according to the present invention and communication between the user terminal 12, the DNS server 13, and the web server 14.

  The relay device 11 is a relay device between the user terminal 12 and the web server 14, and is a device that functions as a gateway such as a home gateway such as a home router. Specifically, it is a device that relays HTTP communication from the user terminal 12 and HTTP communication from the web server 14 and also has a function as a DNS-proxy.

  The user terminal 12 is not particularly limited as long as it is a terminal that performs communication by IP, such as a personal computer, a smartphone, and a tablet terminal.

  The DNS server 13 checks the IP address corresponding to the FQDN (domain name) normally input at the user terminal 12, resolves the name in response to the inquiry from the user terminal 12, and can return the IP address It is a cache server. In addition to searching and responding from a combination of the FQDN and IP address recorded by the server itself, the name may be resolved by relaying the request to another DNS cache server.

  The web server 14 is a server having a server function of transmitting content in response to a request from the user terminal 12. Although there is only one in FIG. 1, there are actually a large number of servers on the Internet, each having a FQDN and a corresponding IP address of IPv4 or IPv6 or both.

  For communication performed between them, the relay device 11 includes a DNS-proxy function unit 21 and a responsiveness measurement unit 22 in addition to a function as a general relay device. The DNS-proxy function unit 21 obtains an IP address from the FQDN sent from the user terminal 12, that is, relays the DNS request and resolves the name (FQDN) with the DNS server 13. Further, as will be described later, the responsiveness measuring unit 22 transmits and confirms whether or not connection is possible with the web server 14 indicated by the received IP address by both IPv4 and IPv6. It is.

  Among these, each part (21, 22) of the relay apparatus 11 may be an independent chip or may be realized on software. The exchange of data between these units may be actual communication or may be exchanged on a memory space. The relay device 11 includes a processor as a processing unit for realizing these, and a volatile memory and a nonvolatile memory as a storage unit.

The processing performed by the relay device 11 will be described with reference to the sequence diagram shown in FIG.
First, when an access to an address including the FQDN is instructed from a browser or the like of the user terminal 12, the user terminal 12 obtains an IP address specified by the FQDN, in order to obtain the IP address specified by the IPv4 and IPv6. A DNS request including the message is transmitted (S111). The DNS-proxy function unit 21 of the relay apparatus 11 that has received the DNS request executes request transfer means for transferring the DNS request to the DNS server 13 for each of IPv4 and IPv6 (S112). The DNS server 13 returns an IP address corresponding to the FQDN included in the DNS request for each of IPv4 and IPv6 (S113).

  Here, the DNS-proxy function unit 21 that has received the IP address does not promptly reply to the user terminal 12, but retains the information of the IP address in a buffer (not shown), and the responsiveness measurement unit. It passes to 22 (S114). The responsiveness measuring unit 22 transmits a packet to the web server 14 specified by the received IP address, and executes responsiveness measuring means for confirming the quality of communication actually returned. (S115).

  In FIG. 2, the network 15a, 15b corresponding to both IPv4 / v6 exists between the web servers 14 and the network 16 corresponding only to IPv4 is interposed between the networks 15a, 15b. Packets of responsiveness measurement performed by specifying an IPv4 address can pass through the networks 15a, 16, 15b, reach the web server 14, and the web server 14 returns a response (S116).

  On the other hand, even if a packet for responsiveness measurement performed by designating an IP address of IPv6 can pass through the network 15a, it cannot pass through the network 16, and the web server 14 in the network 15b ahead of it. Can not reach. For this reason, since a response to the transmitted packet is not returned, the responsiveness measurement unit 22 transmits a responsiveness measurement packet in IPv6 at a predetermined interval, and determines whether a response is returned. Attempt re-measurement means is executed (S121). During this time, the above confirmation by IPv4 proceeds.

  The responsiveness measuring unit 22 that has received the response from the web server 14 by IPv4 sends the responsiveness measurement result to the DNS-proxy function unit 21 that the responsiveness can be measured and confirmed by IPv4 that has been returned quickly compared to IPv6. The response confirmation notifying means to be transmitted is executed (S117). Here, the responsiveness measuring unit 22 may receive a notification that the responsiveness has been measured and confirmed, and promptly return it to the DNS-proxy function unit 21 or return a response in IPv6 over a certain period of time. You may wait for it to come. However, if the user waits for too long, the user's bodily sensation response will decrease, so if the time that is expected to return a response to the second transmission with a version of the IP address that does not return a response has passed, the DNS-proxy function unit 21 It is desirable to respond to IPv4 response measurement results.

  The DNS-proxy function unit 21 that has received the response of the response measurement result executes a confirmation address response unit that returns the stored IPv4 IP address to the user terminal 12 (S118). At this point, since the environment in which the user terminal 12 can be connected to the web server 14 is already prepared, it is possible to use a packet transfer function or the like that the relay apparatus 11 normally uses, using an IPv4 IP address without waiting for a response regarding IPv6 A TCP session is constructed using the relay function (S119).

  On the other hand, the responsiveness measurement unit 22 that has confirmed that the response has not been returned although the responsiveness measurement packet is transmitted a predetermined number of times in IPv6 indicates the responsiveness measurement result indicating that the responsiveness measurement is NG. A measurement failure notification means to be returned as a response to the proxy function unit 21 is executed (S122). Upon receiving this response, the DNS-proxy function unit 21 executes request response means for notifying the user terminal 12 of an error or the IPv6 IP address received from the DNS server 13 (S123). However, since the session has already been established with IPv4 at this point, the notification of the error or the IPv6 address does not cause the user terminal 12 to make any change. That is, the communication is continued while the communication is established with the version of the IP that has received the response measurement result first.

  The responsiveness measurement packet transmitted by the responsiveness measurement unit 22 is not particularly limited as long as it is a command or protocol that can receive an IP-based response from the web server 14, and a ping is transmitted. Alternatively, a TCP session may be attempted. The use of ping is more versatile because it supports protocols other than TCP. On the other hand, some servers do not respond to Ping as a security measure, and may not respond unless TCP is used. For this reason, when both ping and TCP session construction are performed in parallel when measuring responsiveness, the responsiveness can be confirmed more reliably.

  FIG. 3 shows a flow for each of ping and TCP performed by the responsiveness measuring unit 22. These may be performed selectively or in parallel as shown in the figure.

  First, when using ping for responsiveness measurement (S211), Echo-Request is transmitted toward the IP address received from the DNS-proxy function unit 21 (S212). If Echo-Reply is returned from the web server 14 with the IP address (S213), the DNS-proxy function unit 21 is notified that the responsiveness measurement with the IP address of the version is OK (S214). If Echo-Reply does not return even after a predetermined time has elapsed (S213 → S215), Echo-Request is transmitted until the predetermined number of retransmissions is reached (S215 → S212). Generally, if there is no response after repeating about 3 or 4 times, the DNS-proxy function unit 21 is notified that the responsiveness measurement is NG (S216).

  On the other hand, when TCP is used for responsiveness measurement (S221), a packet with a “SYN” flag for starting a TCP session is transmitted to the IP address received from the DNS-proxy function unit 21 (S222). If the web server 14 can receive this, it returns a packet with the flag of “SYN / ACK”, and if the packet can be received (S223), the responsiveness measuring unit 22 “FIN” or “RST”. A packet with the flag is sent to delete the session (S224). This is just a session for measuring responsiveness, and an actual HTTP request or the like is sent from the user terminal 12, so here it is desirable to once terminate the session and release server resources. After that, the fact that the responsiveness measurement with the IP address of the version is OK is transmitted to the DNS-proxy function unit 21 (S225). If “SYN / ACK” does not return even after a predetermined time has elapsed (S223 → S226), a “SYN” packet is transmitted until the predetermined number of retransmissions is reached (S226 → S222). Generally, if there is no response after repeating about 3 or 4 times, the DNS-proxy function unit 21 is notified that the responsiveness measurement is NG (S227).

  It is desirable that the responsiveness measurement unit 22 and the relay device 11 do not leave a cache for this responsiveness measurement result. This is because the communication quality of the network changes every moment, and the previous response measurement result cannot always be reused later.

  In the sequence diagram of FIG. 2 described above, the case where the IPv4 only network 16 is interposed is described. However, in the case where the IPv6 only network is interposed, the IPv4 and IPv6 are reversed in the same manner. Connection for IPv6 in which the responsiveness is measured is performed.

  Next, FIG. 4 shows a case where a version of the IP address with better response quality is preferentially returned to the user terminal 12 when connecting to the web server 14 that can be reached by either IPv4 or IPv6. This will be described using an example. The network 15a and the network 15b between the relay device 11 and the web server 14 can communicate with both IPv4 and IPv6, but the network 15a takes time to pass through IPv4.

  First, a DNS request for requesting FQDN resolution from the user terminal 12 to the DNS server 13 is transferred by the DNS-proxy function unit 21, and the obtained IPv4 and IPv6 IP addresses are passed to the responsiveness measuring unit 22 ( S211 to S214) are the same as S111 to S114 in the embodiment of FIG.

  The responsiveness measuring unit 22 that has received each version of the IP address measures the responsiveness of the web server 14 using the respective IP address (S215). This measurement may be a ping or TCP session as described above. Of these, IPv4 has started to measure responsiveness first, but since IPv4 has a delay in the network 15a, the responsiveness measurement reaches the web server 14 (S216) and the response is returned (S217). In this case, the arrival time with IPv6 is reversed.

  Here, the responsiveness measurement unit 22 determines that IPv6 from which the response has arrived earlier is superior in response quality, and gives priority to the IPv6 IP address and passes it to the DNS-proxy function unit 21 (S218). The DNS-proxy function unit 21 returns the IPv6 IP address to the user terminal 12 (S219). Since the user terminal 12 has acquired the IPv6 IP address, a session is established with the web server 14 using IPv6 (S220).

  On the other hand, for IPv4 that is determined to be inferior in response quality in the networks 15a and 15b, a bad (NG) message is returned to the DNS-proxy function unit 21 as a response measurement result (S221). The DNS-proxy function unit 21 returns an error or an IPv4 IP address as a response to the DNS request received from the user terminal 12 for IPv4 (S222). However, when an IPv4 IP address is returned, it is transmitted after the IPv6 IP address that has been determined to have better response quality, and the user terminal 12 constructs an IPv4 session with inferior response quality. Do not.

  Naturally, contrary to the above, in a network in which IPv6 has poorer response quality, the responsiveness measuring unit 22 determines that IPv4 is a better option, and the DNS-proxy function unit 21 is informed to the user. The responsiveness measurement result for IPv4 is preferentially passed to the terminal 12 so as to preferentially transmit the IPv4 IP address.

11 Relay device 12 User terminal 13 DNS server 14 Web server 15a, 15b Network (both supported)
16 network (supports IPv4 only)
21 DNS-proxy function part 22 Responsivity measurement part

Claims (4)

Communication between a DNS request and a resolved IP address that is provided between a user terminal and a web server and that the user terminal makes with the DNS server for name resolution of the FQDN when the user terminal accesses the web server A relay device having a DNS-proxy function unit for relaying both IPv4 and IPv6 versions,
The DNS-proxy function unit passes each of the IPv4 and IPv6 IP addresses received from the DNS server to the responsiveness measurement unit in the relay device before returning it to the user terminal.
The responsiveness measurement unit measures the responsiveness by actually connecting to the web server using the IP address of each version of IPv4 and IPv6, and passes the responsiveness measurement result to the DNS-proxy function unit. ,
The DNS-proxy function unit is a relay apparatus that returns a version IP address whose responsiveness is confirmed by the received responsiveness measurement result to the user terminal.   The responsiveness measurement unit compares the time taken to measure the responsiveness with respect to each version of IPv4 and IPv6, and gives priority to the responsiveness measurement result with respect to a version with higher response quality. The relay device according to claim 1, wherein the relay device is passed to the DNS-proxy function unit.   The relay apparatus according to claim 1, wherein the responsiveness measurement is ping transmission, TCP session establishment, or both. Communication between a DNS request and a resolved IP address that is provided between a user terminal and a web server and that the user terminal makes with the DNS server for name resolution of the FQDN when the user terminal accesses the web server When the relay device having the DNS-proxy function unit that relays both the IPv4 version and the IPv6 version selects the version to be preferentially connected to the user terminal,
The DNS-proxy function unit passes each of the IPv4 and IPv6 IP addresses received from the DNS server to the responsiveness measurement unit in the relay device before returning it to the user terminal.
The responsiveness measurement unit measures responsiveness to the web server using IP addresses of IPv4 and IPv6, and passes the responsiveness measurement result to the DNS-proxy function unit.
The DNS-proxy function unit returns the IP address of the version that has received the responsiveness measurement unit to the user terminal,
A method for selecting an optimum route that enables the user terminal to establish a session with the web server with a version of the IP having a better response measurement result.

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