JP3141852B2 - Round-trip path detecting method, apparatus using the same, and recording medium storing the program - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a round trip path of a packet signal bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path control devices. The present invention relates to a device used and a recording medium recording the program.

[0002]

2. Description of the Related Art Conventionally, in a large-scale open packet switching network such as the Internet (hereinafter simply referred to as "network"), there is a possibility that a packet signal transferred from a sender to a destination passes. In general, there are a plurality of paths having the same path. For this reason, it is necessary to detect a path through which the packet signal actually passes for path control and the like. Then, for example, when it is detected that the packet signal is being transferred on a slow route, the route control can be performed so as to avoid the slow route. In addition,
As software for detecting an outgoing route from a sender to a destination, for example, software named “traceroute” is widely known. Here, with reference to FIG. 7, an example of a conventional method for detecting a forward path used in the above software will be briefly described. FIG. 7 is a schematic diagram of a network for explaining a conventional method for detecting a forward route.

[0003] A network 100 shown in FIG. 7 includes a trunk network 102 and first and second host computers 10 and 12 connected to each other via the trunk network 102. The trunk network 102 includes first to fourth routers 14, 16,
It consists of 18 and 20 four routers. In FIG. 7, a communication line (link) connecting the routers is indicated by a straight line.

In this conventional example, a packet transferred from a first host computer (hereinafter also referred to as “second host”) 10 to a second host computer (hereinafter also referred to as “first host”) 12. An example of detecting a signal path will be described. In this conventional example, first, the first
The host 10 creates a search packet signal destined for the second host 12.

[0005] Next, the first host 10 sets the lifetime of the search packet signal to one hop and transmits it as the first search packet signal 22. The hop number means the number of routers to which the packet signal is transferred. For example, when the survival time is 5 hops, the packet signal is sequentially transferred to the router, and the survival time is cut off at the fifth router.

A one-hop packet signal 22 with a survival time of one hop
Is transferred to the first router 14 and the lifetime expires. In this case, the first router 14 transmits the first error packet signal 22a. First error packet signal 22a
Is addressed to the first host 10 and the sender is the first router 1
4 is included. Then, the first host 10 receiving the first error packet signal 22a,
The fact that the first error packet signal 22a is transmitted from the first router 14 is recorded.

Next, the first host 10 increases the lifetime of the search packet signal by one hop and sets it to two hops. Then, this is transmitted as the second search packet signal 24. The second search packet signal 24 passes through the first router 14 and is transferred to the second router 16, and then its lifetime expires. In this case, the second router 16
An error packet signal 24a is returned to the first host 10. The first host that has received the second error packet signal 24a transmits the second error packet signal 24a to the second router 16.
Record what was sent in.

Next, the first host 10 sets the lifetime of the search packet signal to 3 hops by increasing it by one hop. Then, this is transmitted as the third search packet signal 26. The third search packet signal 26 passes through the first and second routers 14 and 16 sequentially, and
After being transferred to the router 18, its lifetime expires. In this case, the third router 18 outputs the third error packet signal 2
6a is returned to the first host 10. The first host 10 that has received the third error packet signal 26a records that the third error packet signal has been transmitted by the third router 18.

Next, the first host 10 sets the survival time of the search packet signal to 4 hops by increasing it by one hop. Then, this is transmitted as the fourth search packet signal 28. The fourth search packet signal 28 is
After being sequentially passed through the third routers 14, 16 and 18 and transferred to the second host 12, the survival time expires. In this case, the second host 12 sends the fourth error packet signal 28
a is returned to the first host 10. The first host 10 that has received the fourth error packet signal 28a records that the fourth error packet signal has been transmitted from the second host 12.

[0010] The first host 10 detects a route sequentially passing through each router as an outward route in the order in which the error packet signals are transmitted. That is, in this conventional example, the error packet signal is the first error packet signal 2
2a, the second error packet signal 24a, the third error packet signal 26a, and the fourth error packet signal 28a were transmitted in this order. Therefore, the route of the outward route is determined by the first host 1 in the order in which these error packet signals are transmitted.
0, first router 14, second router 16, third router 18
Are sequentially passed to reach the second host 12.

In this manner, the first host 10 sends the second
It is possible to detect the forward path of the packet signal reaching the host 12.

[0012]

However, in a large-scale open packet switching network such as the Internet, the forward route and the backward route of bidirectional communication do not always match. In that case, it may be necessary to detect not only the outward route but also the return route.

Conventionally, however, it has been difficult to detect a return route, even if a forward route can be detected. For example, in the conventional example described above, it is difficult for the first host 10 to detect the path of the packet signal returned from the second host 12 to the first host 10.

This is because the transmission of the search packet signal and the detection of the return path as in the conventional example is the second step.
This is because it is difficult to instruct the host 12 from the first host 10. For this reason, in the related art, for example, even if a problem occurs in the route control on the return route of the two-way communication, it has been difficult to find and avoid the problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a technique for detecting a round-trip route of a packet signal for bidirectional communication in a packet switching network.

[0016]

(Round Trip Detection Method) In order to achieve this object, according to the round trip detection method of the present invention, the connection is established by a packet switching network composed of a plurality of path control devices. In detecting a round-trip path of a packet signal bidirectionally communicated between the two points, a first point as a sender among the two points is set as a destination, and a second point among the two points is set. Is created as a via point, and the plurality of search packet signals are set by sequentially increasing the lifetime of the search packet signal, and are sequentially transmitted from the first point. When the lifetime of the transferred search packet signal expires, an error packet signal transmitted from the second point or the path control device is received at the first point. And, there is a path through the second point and the path control device in the order in which the error packet signal originated, as a method of detecting as the round-trip path.

As described above, according to the round-trip route detection method of the present invention, the setting is made to start from the first point which is the originator, return to the first point again via the second point. Create a search packet signal. For this reason, not only the outbound route to the second point but also the error packet signal from the route control device on the return route after passing through the second point can be received at the first point. Therefore, by following the path that sequentially passes through the path device in the order in which the error packet signal was transmitted, not only the outward path but also the return path can be detected.

In the present invention, preferably, every time an error packet signal is received, the search packet signal is transmitted by sequentially increasing the survival time until the error packet signal transmitted from the destination is received. Good.

This makes it possible to clarify the search packet signal and the error packet signal. As a result, the order in which the error packet signals are transmitted by the path control circuit and the order in which the error packet signals are received at the first point, which is the sender, can be reliably matched. Therefore, it is possible to easily analyze the round-trip route based on the transmission order of the error packet signal.

In a large-scale open packet switching network such as the Internet, the route control device sometimes has a check function for preventing transfer of an illegal packet signal. This function determines, for example, whether the direction of the sender of the packet signal and the direction of the transfer source of the packet signal as seen from the path control device match or not. Then, when the path control device determines that the packet signal does not match, the packet signal is invalidated and discarded.

On the other hand, after passing through a second point which is a waypoint,
In the search packet signal on the return path toward the first point, which is the sender, the direction of the sender and the direction of the transfer source viewed from a certain route control device do not match. Therefore, when a discard path control device having a check function exists on the return path, the search packet signal is discarded there. As a result, it becomes difficult to transfer the search packet signal from the discard path control device to the destination. In that case,
It is difficult to detect the previous return path from the discard path control device.

Therefore, in the round-trip route detection method of the present invention, preferably, the search packet signal after passing through the second point is regarded as an invalid packet because the sender of the search packet signal is not the second point. When detecting a discard path control device to discard as a signal, the first
Is set as the destination, and a re-search packet signal is set with the discard path control device set as a via point, and a plurality of re-search packet signals are sequentially increased in the lifetime of the re-search packet signal. Let me set the first
At the first point, a new error packet signal transmitted by the path control device when the survival time of the transferred re-search packet signal expires is received at the first point. In addition to the second point to the discard route control device via the second point and the route passing through the route control device in the order in which the error packet signal is transmitted, the route from the discard route control device to the first point is added. It is desirable to detect a path that passes through the path control device in the order in which the new error packet signals are transmitted, as a round-trip path.

As described above, the re-search packet signal set as a transit point by the discard route control device is not discarded by the discard route control device. As a result, if the lifetime of the re-search packet signal does not expire, the re-search packet signal returns to the first point from the discard path control device via the previous return path. As a result, at the first point, the new error packet signal transmitted from the route control means on the previous route from the discard route control device can be received.

Therefore, in addition to following the path that sequentially passes through the path control device to the discard path controller in the order in which the error packet signal was transmitted, in addition to the path in which the new error packet signal was transmitted, By sequentially following a path that sequentially passes through the path control device, a round-trip path can be detected. The discard path control device is
An error packet signal transmitted by the discard path control device that discarded the search packet signal can be detected by receiving at the first point.

Meanwhile, in a large-scale open packet switching network such as the Internet,
In some cases, a route control device that enhances the security effect, that is, a so-called firewall is installed. The firewall is usually provided on a path between a backbone network called a backbone and a network of each individual or each organization. Then, the firewall generally blocks the packet signal for which the waypoint is set.

On the other hand, the search packet signal has the second point set as a waypoint. Therefore, if a firewall (blocking route control device) exists on the route, the search packet signal is blocked there. as a result,
It becomes difficult to transfer the search packet signal from the cutoff path control device to the destination. In that case, it is difficult to detect the previous route from the cutoff route control device.

Therefore, in the round-trip route detection method according to the present invention, it is preferable that, when a route control point for blocking the search packet signal is detected because the waypoint is set, the search packet signal is transmitted to the second terminal. A point 1 is set as a destination, and a re-search packet signal set as a via point in front of the cut-off route control device and via a route control device closest to the cut-off route control device is created, and a plurality of the re-search packet signals are created. When a packet signal is set by sequentially increasing the lifetime of the search packet signal, and sequentially transmitted from the first point, and the lifetime of the transferred re-search packet signal expires. Receiving, at the first point, a new error packet signal transmitted by the path control device, and controlling the path control device from the first point to the nearest path control device to the error. In addition to the forward path that the packet signals pass in the order in which they were transmitted, the return path that passes through the path control apparatus from the nearest path control device to the first point in the order in which the new error packet signals were transmitted. Route
It is detected as a substantial round trip route.

As described above, the re-search packet signal set as the via point using the nearest route control device before the cutoff route control device starts from the first point and returns to the nearest route control device unless the survival time expires. It returns to the first point again via the means. As a result, the round trip path of the packet signal in the trunk network can be detected.

On the other hand, the cutoff path device is provided on a service line from the trunk network. Therefore, the forward route and the route from the closest route control unit usually coincide with each other. Therefore, if a round-trip route in the trunk network to the nearest route control means is detected, a round-trip route between the first point and the second point is substantially detected.

Therefore, in addition to following the path that sequentially passes through the path control device to the nearest path controller in the order in which the error packet signal was transmitted, the nearest path discard path controller in the order in which the new error packet signal was transmitted. By following a route that sequentially passes through the route control device from
A round trip path can be detected. In addition, the cutoff path control device can detect the error packet signal transmitted from the cutoff path control device that cuts off the search packet signal by receiving the error packet signal at the first point.

(Round Trip Detector) According to the round trip detector of the present invention, a packet which is bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path controllers. A round-trip path detecting device provided at a first point among two points as a sender of a packet signal to detect a round-trip path of a signal,
A search packet signal creation unit configured to set a first point as a caller as a destination of the two points as a destination and create a search packet signal set with a second point of the two points as a waypoint; The search packet signal is set by sequentially increasing the lifetime of the search packet signal,
A search packet signal transmitting unit for sequentially transmitting the search packet signal from the first point, and an error packet signal transmitted by the second point or the route control device when the lifetime of the transferred search packet signal expires. An error packet signal receiving unit that receives at a first point, a path analyzing unit that detects a path passing through the second point and the path control device in the order in which the error packet signal is transmitted as a reciprocating path, and And a storage unit for storing the reciprocating route.

As described above, according to the round-trip path detecting apparatus of the present invention, the search packet signal creation unit sets the search point in which the first point as the sender is set as the destination and the second point is set as the waypoint. Create a packet signal. For this reason, not only the outbound route to the second point but also the error packet signal from the route control device on the return route after passing through the second point can be received at the first point. Therefore, by following the path that sequentially passes through the path device in the order in which the error packet signal was transmitted, not only the outward path but also the return path can be detected.

(Recording Medium) According to the recording medium of the present invention, a reciprocating path of a packet signal bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path control devices. A process of setting a first point as a caller among the two points as a destination and generating a search packet signal in which a second point among the two points is set as a via point; The search packet signal is set by sequentially increasing the life time of the search packet signal, and is sequentially transmitted from the first point; and the survival time of the transferred search packet signal is A process of receiving, at the first point, an error packet signal transmitted from a second point or the path control device when the packet is cut off; A path through the order in which the signal originated, which records a program for executing a process of detecting as round-trip path to the computer.

By causing a computer to read and execute the program recorded on the recording medium of the present invention, a search packet signal having a first point as a destination as a destination and a second point as a via point is set. Create For this reason, not only the outbound route to the second point but also the error packet signal from the route control device on the return route after passing through the second point can be received at the first point. Therefore, by following the path that sequentially passes through the path device in the order in which the error packet signal was transmitted, not only the outward path but also the return path can be detected.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited only to the illustrated example. <First Embodiment> In the first embodiment, the two-way communication between the first host computer 10 and the second host computer 12 in the network 100 shown in FIG. In the following, an example of detection will be described.

The processing of the round-trip route detection method according to the first embodiment is executed by the computer of the first host 10 under the control of a program. This program is provided, for example, by a recording medium. As the recording medium, for example, a magnetic disk, a semiconductor memory, or any other computer-readable medium can be used.

The first and second hosts 10 and 12
They are connected to each other via a network 100. The network 100 is connected to the first to fourth routers 1
4, 16, 18 and 20. In FIG. 1, a communication line (link) connecting the routers is indicated by a straight line.

The first host 10 has a round-trip path detecting device 40. FIG. 2 shows a round-trip path detection device 40.
Is shown. As shown in FIG. 2, the round-trip path detection device 40 includes a search packet signal creation unit 52, a search packet signal transmission unit 54, and an error packet signal reception unit 5.
6, a route analysis unit, and a storage unit. In this embodiment, the route analysis /
A storage unit 58 is provided.

Then, in this embodiment, the search packet signal creation section 52 creates a plurality of search packet signals. The search packet signal sets the first host 10 as a sender as a destination and sets the second host 12 as a waypoint.

The search packet signal transmitting section 54
The first host 1 sets a plurality of search packet signals by sequentially increasing the lifetime of the search packet signals.
Sends sequentially from 0. Then, the error packet signal receiving unit 56 receives an error packet signal transmitted from the second host 12 or the path control device when the lifetime of the transferred search packet signal expires.

The route analysis / storage unit 58 detects a route that passes through the second host 12 and the route control device in the order in which the error packet signal was transmitted as a reciprocating route, and stores the detected reciprocating route. I do.

Next, a method for detecting a round trip path will be described with reference to FIG. First, the search packet signal creation unit 52 of the round trip route detection device 40 provided in the first host 10 creates a search packet signal as described above. As described above, the search packet signal sets the first host 10 as a sender as a destination and sets the second host 12 as a waypoint (S1 in FIG. 3).

In this embodiment, the first host 10 is set as the destination in the IP address, but an imaginary port number is set as the port number following the IP address.
If a fictitious port number is set, when the search packet signal reaches the destination first packet, an error signal indicating that the corresponding port number does not exist is returned to the sender. As a result, it is possible to detect that the search packet signal has reached the destination.

Next, the search packet signal transmitting section 54 of the round trip path detecting section 40 sets the lifetime of the search packet signal to one hop, and sets this to the first search packet signal 2.
2 is transmitted (S2, S3 in FIG. 3).

Next, the packet signal 22 having a one-hop survival time is transferred to the first router 14, and then the survival time expires. In FIG. 1, the expiration of the survival time is schematically indicated by a mark “x”. And the first router 14
Sends a first error packet signal 22a. Then, the error signal receiving unit 52 of the round trip path detecting unit 40 of the first host 10 receives the first error packet signal 22a (S4 in FIG. 3).

The first error packet signal 22a includes information indicating that the destination is the first host 10 and the sender is the first router 14. Then, information that the source of the first error packet signal 22a is the first router 14 is recorded in the route analysis / storage unit 52.

Further, the route analysis / storage unit 52 determines that the search packet signal has not yet reached the destination (S6 in FIG. 3). Then, the route analysis and storage unit 52
Through the search packet signal creation unit 52,
The packet is transmitted to the search packet signal transmitting unit 54.

Next, the search packet signal transmitting unit 54
The lifetime of the search packet signal is increased by one hop and set to two hops (S2 in FIG. 3). Then, this is transmitted as the second search packet signal 24 (S3 in FIG. 3).
The second search packet signal 24 passes through the first router 14 and is transferred to the second router 16, and then its lifetime expires. In this case, the second router 16 returns the second error packet signal 24a to the first host 10. And
The first host 10 receives the second error packet signal 24a (S4 in FIG. 3). Then, the first host 10 records that the second error packet signal 24a has been transmitted by the second router 16 (S5).

Similarly, the survival time is increased by one hop at a time, and the third to seventh search packet signals 26, 2
8, 30, 32 and 34 are transmitted in sequence. And
For the third search packet signal 26, the third router 1
8 emits a third error packet signal 26a. Then, for the fourth search packet signal 28, the second host 12 as a waypoint passes through the fourth error packet signal 28a.
Outgoing. Note that the second host 12 also functions as a path control device.

In response to the fifth search packet signal 30, the third router 18 again transmits the fifth error packet signal 3
Send 0a. For the sixth search packet signal 32, the fourth router 20 outputs the sixth error packet signal 3
Send 2a. The first host 10 responds to the seventh search packet signal 34 by the seventh error packet signal 3.
Send 4a. However, the seventh error packet signal 34
“a” is an error signal not due to time out, but due to the absence of the destination port number.

Then, the route analysis /
The storage unit 52 detects a route that sequentially passes through each router and the second host 12 as an outgoing route in the order in which the error packet signals are transmitted. In other words, in this embodiment, the round-trip route is such that the first host 10, the first router 14, the second router 16, the third router 18, the second host 12, After passing through the router 18 and the fourth router 20 sequentially, the first host 1
It is detected as a route that reaches 0.

In this way, the first host 10 sends the second
It is possible to detect the forward path of the packet signal reaching the host 12.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the third router 18 has a check function for preventing transfer of an illegal packet signal.
The third router 18 determines whether the direction of the sender of the packet signal matches the direction of the transfer source of the packet signal. Specifically, when the interface 42 provided in the third router 18 receives a packet signal transmitted from a source other than the second host 12, the third router 18 discards the packet signal as invalid.

On the other hand, the search packet signal transferred to the third router 18 via the second host 12 is received by the interface 42. As a result, the third
As seen from the router 18, the direction of the first host 10 as the sender and the direction of the second host 12 as the transfer source do not match. Therefore, the search packet signal is transmitted to the third router 18.
, Is discarded.

When the packet signal is discarded,
The third router 18 sends the error packet signal to the first
Send to host 10. Therefore, the first host 10
Can detect that the third router 18 is a router that discards the packet signal.

FIG. 4 shows the path 44 of the search packet signal until it is discarded. As shown in FIG. 4, the search packet signal is not transferred beyond the third router 18 on the return path. Therefore, in the second embodiment, a re-search packet signal is created, and a route ahead of the third router 18 is detected.

Next, a method for detecting a reciprocating route in the second embodiment will be described with reference to FIG. Also in the second embodiment, first, similarly to the first embodiment, a search packet signal in which the destination is set to the first host 10 and the waypoint is set to the second host 12 is created.
In the same manner as in the first embodiment, the route to the second host 12 is detected (S11 to S15 in FIG. 5).

When the third router 18 detects that the search packet is discarded, it generates a re-search packet signal. Although the destination of this re-search packet signal remains the first host 10, the waypoint has been changed to the third router 18 (S16 in FIG. 5).

As described above, the re-search packet signal set as the waypoint through the third router 18 is not discarded in the third router 18. As a result, the re-search packet signal returns from the third router 18 to the first host 10 via the previous return route if the lifetime has not expired. FIG.
The path 46 of the re-search packet signal is shown in FIG. And
The first host 10 can receive the new error packet signal transmitted from the route control means (for example, the fourth router 20) on the route ahead of the third router 18.

The return of the re-search packet signal to the first host 10 is issued from the first host 10.
The error can be detected by receiving an error packet signal that indicates that there is no port number corresponding to the designated port number (S17 in FIG. 5).

Then, the reciprocating path detecting device 40 of the first host 10 firstly transmits the third host 10 via the second host 12 via the second host 12 in the same manner as in the first embodiment.
A path is detected that passes through the router and the second host up to the router 18 in the order in which the error packet signals were transmitted.
Further, in addition to this route, a route that passes through a router from the third router 18 to the first host 10 in the order in which the new error packet signal is transmitted is detected as a round trip route.

Specifically, from the first host 10, the first router 14, the second router 16, the third router 1
8, the second host 12, the third router 18, the fourth router 20
, And a round trip route to the first host 10 is detected.

<Third Embodiment> Next, a third embodiment will be described with reference to FIG. In the third embodiment, a firewall 48 is provided between the third router 18 and the second host 12.

In the third embodiment, a firewall 42 is provided between the third router 18 and the second host 12. The firewall 42 blocks a packet signal for which a via point has been set.

On the other hand, the search packet signal is set by the second host 12 as a waypoint. Therefore, the search packet signal is blocked by the firewall 42.

When the packet signal is interrupted,
The firewall 42 transmits an error packet signal to the first host 10 of the sender. Therefore, the first host 10 can detect the presence of the firewall 42.

FIG. 6 shows a path 44 of the search packet signal until the signal is cut off. As shown in FIG. 6, the firewall 42 is provided on a service line from the trunk network 102 to the second host 12. Then, the search packet signal is not transferred beyond the firewall 42. Therefore, in the third embodiment, a re-search packet signal is created to detect the return route.

In the second embodiment, first, the first
In the same manner as in the first embodiment, a search packet signal in which the destination is set to the first host 10 and the waypoint is set to the second host 12 is created, and as in the first embodiment,
The route to the third router 18 is detected.

When detecting that the firewall 42 in front of the third router 18 has blocked the search packet, it generates a re-search packet signal. In this re-search packet signal, the destination remains the first host 10,
The waypoint is changed to the third router 18 immediately before the firewall 42.

As described above, the re-search packet signal set as the waypoint through the third router 18 does not pass through the firewall 42. As a result, the re-search packet signal returns from the third router 18 to the first host 10 via the previous return route if the lifetime has not expired. FIG.
The path 46 of the re-search packet signal is shown in FIG.

The firewall 42 is provided on the service line from the trunk network 102. Therefore, the outward route ahead of the third router 18 matches the route.
For this reason, the trunk network 10 up to the third router 18
If the reciprocating route in 2 is detected, the reciprocating route between the first host 10 and the second host 12 is substantially detected.

In the first host 10, the third host
Route control means (for example, the fourth
The new error packet signal transmitted from the router 20) can be received.

Then, the reciprocating path detecting device 40 of the first host 10 first transmits an error packet signal to the router from the first host 10 to the third router 18 in the same manner as in the first embodiment. The paths that pass in the order in which they were performed are detected. Further, in addition to this route, the third router 18
A path that passes through the router from to the first host 10 in the order in which the new error packet signals are transmitted is detected as a substantial round-trip path.

Specifically, from the first host 10, the first router 14, the second router 16, the third router 1
8. The first host 10 passes through the fourth router 20 sequentially.
A substantial round trip route to is detected.

In the above embodiment, an example in which the present invention is configured under specific conditions has been described. However, the present invention can be variously modified. For example, in the above-described second embodiment, an example has been described in which the third router 18 in the immediate vicinity of the second host 12, which is the waypoint, discards the return path search packet signal. The position where the router that discards the packet signal is provided is not limited to this.

If there are a plurality of discard route control devices on the return route, the re-search packet signal set with the first discard route control device as a route point is also used by the second discard route control device. Is discarded. In that case, a re-searching packet signal with the second discard path control device as a new route point may be transmitted. Further, when the discard route control device further discards the data, the discard route control device may be sequentially set as a waypoint.

[0077]

As described above in detail, according to the present invention, starting from the first point which is the sender, the second point is returned to the first point again. Create the search packet signal set in. For this reason, not only the outbound route to the second point but also the error packet signal from the route control device on the return route after passing through the second point can be received at the first point. Therefore, by following the path that sequentially passes through the path device in the order in which the error packet signal was transmitted, not only the outward path but also the return path can be detected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the Internet for describing a first embodiment.

FIG. 2 is a block diagram illustrating a reciprocating route detection device according to the first embodiment.

FIG. 3 is a flowchart for explaining a round-trip route detection method according to the first embodiment.

FIG. 4 is a schematic diagram of the Internet for explaining a second embodiment.

FIG. 5 is a flowchart illustrating a round-trip route detection method according to a second embodiment.

FIG. 6 is a schematic diagram of the Internet for describing a third embodiment.

FIG. 7 is a schematic diagram of the Internet for explaining a conventional example.

[Explanation of symbols]

 Reference Signs List 10 first host computer (first host) 12 second host computer (second host) 14 first router 16 second router 18 third router 20 fourth router 22 first search packet signal 22a first error packet signal ( 1st error signal) 24 2nd search packet signal 24a 2nd error packet signal (2nd error signal) 26 3rd search packet signal 26a 3rd error packet signal (3rd error signal) 28 4th search packet signal 28a fourth error packet signal (fourth error signal) 30 fifth search packet signal 30a fifth error packet signal (fifth error signal) 32 sixth search packet signal 32a sixth error packet signal (sixth error signal) 34 packet signal for seventh search 34a seventh error packet signal (seventh error signal) 40 round-trip path detecting device Reference Signs List 42 interface 44 path of search packet signal 46 path of re-search packet signal 48 firewall 52 search packet signal creation unit 54 search packet signal transmission unit 56 error packet signal reception unit 58 path analysis / storage unit 100 network 102 trunk network

Claims (6)

(57) [Claims] In detecting a round-trip path of a packet signal that is bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path control devices, a sender of the two points is referred to as a sender. A first packet point is set as a destination, and a search packet signal is set in which the second point of the two points is set as a via point. A plurality of the search packet signals are The survival time is sequentially increased and set, and the first
And the error packet signal transmitted from the second point or the route control device is received at the first point when the survival time of the transferred search packet signal expires. And a path that passes through the second point and the path control device in the order in which the error packet signal is transmitted is detected as the round-trip path. 2. The round-trip route detection method according to claim 1, wherein each time the error packet signal is received, the survival time is sequentially increased until the error packet signal transmitted from the destination is received. A method for detecting a round trip route, wherein the search packet signal is transmitted with an increase. 3. The round-trip path detection method according to claim 1, wherein the search packet signal after passing through the second point is not a sender of the search packet signal. Therefore, when a discard route control device that discards the packet as an invalid packet signal is detected, the first point that is the sender is set as the destination, and the re-search packet that is set with the discard route control device as a via point A signal is created, a plurality of the re-search packet signals are set by sequentially increasing the lifetime of the re-search packet signal, and sequentially transmitted from the first point. Receiving at the first point a new error packet signal transmitted by the path control device when the survival time of the search packet signal expires, from the first point via the second point A path from the discard path control device to the first point, in addition to the second point to the discard path control device and a path passing through the path control device in the order in which the error packet signal is transmitted. A method for detecting a round-trip path, wherein a path that passes through a control device in the order in which the new error packet signals are transmitted is detected as the round-trip path. 4. The round-trip route detection method according to claim 1, wherein the search packet signal is transmitted when a route control device that blocks the search packet signal is detected because a route point is set. The first point, which is the user, is set as a destination, and a re-search packet signal is set as a via point in front of the cutoff path control device and the route control device closest to the cutoff path control device, and The re-search packet signal of the above is set by sequentially increasing the survival time of the search packet signal, and sequentially transmitted from the first point. Receiving, at the first point, a new error packet signal transmitted by the route control device when the time has expired; and controlling the route control device from the first point to the nearest route control device. In addition to the forward path in which the error packet signal is transmitted in the order in which the error packet signal is transmitted, the signal passes through the path control device from the nearest path control device to the first point in the order in which the new error packet signal is transmitted. A return path detection method, wherein the return path is detected as a substantial return path. 5. A packet signal among two points for detecting a round-trip path of a packet signal bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path control devices. A round-trip route detection device provided at a first point as a sender of the two points, wherein the first point as a sender among the two points is set as a destination, and a second point among the two points is set as a destination. A search packet signal creation unit for creating a search packet signal set as a via point; and setting the plurality of search packet signals by sequentially increasing the lifetime of the search packet signal.
And a search packet signal transmitting unit that sequentially transmits the error packet signal transmitted by the second point or the route control device when the lifetime of the transferred search packet signal expires. An error packet signal receiving unit that receives at a first point; a path analyzing unit that detects a path that passes through the second point and the path control device in the order in which the error packet signal is transmitted as the round-trip path; And a storage unit for storing the detected round trip route. 6. In detecting a round-trip path of a packet signal that is bidirectionally communicated between two points connected to each other by a packet switching network constituted by a plurality of path control devices, a sender of the two points may be used as a sender. Setting a first point as a destination and generating a search packet signal with the second point of the two points set as a via point; and transmitting the plurality of search packet signals to the search packet. The survival time of the signal is sequentially increased and set, and the first
And transmitting the error packet signal transmitted by the second point or the path control device when the survival time of the transferred search packet signal expires at the first point. A program for causing a computer to execute a process of receiving, and a process of detecting, as the round trip route, a route that passes through the second point and the route control device in the order in which the error packet signal is transmitted is recorded. A recording medium characterized by the above-mentioned.