JP4546351B2 - Multicast trace route system in IP multicast network - Google Patents

Description

  The present invention relates to a multicast trace route system for following a path between a transmission host that is a transmission source of multicast data and a reception host that receives the multicast data in an IP multicast network composed of routers, layer 3 switches, and the like. .

A PIM-SM (Protocol Independent Multicast-Sparse Mode) system is generally used as a system for transmitting video packets and audio packets to a plurality of receiving hosts scattered over a wide range.
In this PIM-SM system, multicast data from the transmission host S is transmitted in accordance with a so-called shortest path tree (SPT), and preset as shown in FIG. 6 corresponding to a plurality of reception hosts. In some cases, the packet is sent to a rendezvous point (shown with shading in FIG. 6), and each packet is copied and distributed to a plurality of receiving hosts Ra and Rb at the rendezvous point.

  Such a multicast data transmission path includes a multicast group address for identifying multicast data in a multicast routing table provided in each router shown in FIG. 6 (indicated by reference numerals R1 to R6 in FIG. 6). The management is performed by storing an interface corresponding to a receiving host that intends to receive the multicast data.

There is also a router with a switchover function that switches from the transmission path that branches at the rendezvous point as described above to the shortest path, so that when the load on the rendezvous point increases, the entire network can be processed. The load is equalized.
The condition for switching the transmission path by the switchover function described above is not specifically defined, so it is left to each router vendor. For example, when the first multicast data is received, the shortest While there is a router configured to switch to a path, a setting that does not switch to the shortest path at all may be applied.

  By the way, in the IP network, as a technique for tracing the route until the data transmitted from the transmission host reaches the reception host, using a trace route function, for example, by ICMP (Internet Control Message Protocol) There is a technique in which a control packet is sent from a receiving host to a sending host as a destination, and reachability is confirmed by whether or not a response is returned from the sending host within a predetermined time. Since the ICMP described above is originally a unicast protocol, the control packet exchanged between the receiving host and the transmitting host in the trace route function is naturally forwarded according to the unicast routing table of each router. Are sequentially transferred to reach the sending host or the receiving host.

  In addition, by multicasting the same control packet from the transmission host side, route confirmation with a plurality of reception hosts may be performed collectively. In this case, the control packet transmitted by the transmission host is transferred according to the multicast routing table of each router and transferred to each of the plurality of reception hosts. In response to the control packet transferred in this manner, a response packet is returned by the receiving host using unicast in the same manner as the general trace route described above.

Patent Document 1 describes a technique for efficiently collecting information on a path through which a connectionless packet has passed.
Japanese Unexamined Patent Publication No. 20002-247100

  As described above, in a multicast network, multicast data transmitted from a transmission host reaches a reception host via either a route passing through a rendezvous point or a so-called shortest path. However, since the timing of switching between the two routes described above is completely left to the router on the route, the route taken by the multicast data is not fixed to one of the two routes described above. It can be either.

On the other hand, as described above, in the conventional trace route technology, the routing table for unicast is referred to for the transfer of the ICMP control packet. It was only possible to check the reachability of the control packet.
For example, even if a failure occurs in this route when multicast data is delivered to the receiving host via a route that passes through the rendezvous point, the trace route technology based on the unicast routing table does not reach the shortest path. Therefore, it is impossible to detect a failure in a route through which multicast data is actually transmitted.

In this way, if the trace route control packet is sent / received through a route (shortest path) different from the route through which the multicast data actually passes, the shortest path through which the control packet is sent / received regardless of the failure of the actual route. As a result, the reachability of the multicast data transmission path may be erroneously confirmed.
On the other hand, even when trying to check reachability from the transmission host side, there is a possibility that an ICMP control packet returned by unicast from the reception host may pass through a route different from that of multicast data. For example, if a failure occurs in the transmission path (shortest path) of the response packet sent by the receiving host, the response packet is sent to the sending host because of the shortest path failure even though multicast data has arrived. Not reach. In such a case, there is a possibility that it is erroneously determined that the multicast data has not reached the receiving host.

  As described above, in the conventional technique, even when the trace route is performed mainly by the sending host side or when the trace route is performed mainly by the receiving host side, the trace route packet is transmitted between the sending host and the receiving host. Since it is not guaranteed that the round-trip path is exactly the same as the multicast data transmission path, the reachability of the multicast data transmission path cannot be correctly evaluated.

On the other hand, in the method of multicasting ICMP control packets from the sending host, the traffic on the network increases and the load on each router increases. Therefore, the reachability of the multicast data transmission path is mainly based on the receiving host. There is a need for technology that can legitimately assess
It is an object of the present invention to provide a multicast trace route system that can legitimately evaluate the reachability of a multicast data transmission path.

A first multicast trace route system according to the present invention includes a control packet generation unit and a verification unit at a reception host, a trace packet detection unit and a return unit at a transmission host, and a detection unit and a transfer unit at a router. It is prepared for.
The principle of the first multicast trace route system according to the present invention is as follows.

In at least one of a plurality of receiving hosts provided in a trace route system in a multicast network composed of a plurality of routers having a multicast routing table for transferring multicast data sent from a sending host to each of a plurality of receiving hosts, The control packet generation means generates a request packet including identification information indicating in a predetermined format that the packet is a control packet that requests tracking of the transmission path of multicast data, and sends the request packet to the multicast network with the transmission host as the destination. The verification means verifies the reachability of the multicast data transmission path based on the return status of the response packet from the transmission host to the request packet. The control packet generator generates the request packet by manipulating a part of an information field included in the ICMP control packet. In the transmission host, the request detection means detects the request packet from the control packet that has arrived via the multicast network. The return means returns a response packet including identification information to the receiving host in response to detection of the request packet by the detection means. In the plurality of routers, the detecting means detects a trace route packet including a request packet and a response packet from a control packet that has arrived via the multicast network. The transfer unit transfers the trace route packet based on the multicast routing table in response to the detection of the trace route packet by the detection unit.

The operation of the first multicast trace route system configured as described above is as follows.
The request packet generated by the control packet generator provided in the receiving host is detected by the detector provided in the router every time it reaches each router constituting the multicast network, and is used for transfer processing by the transfer unit. Is done. At this time, the transfer means determines the transfer destination based on the multicast routing table instead of the unicast routing table used in a general trace route, and transfers the above-described request packet. In this way, by sequentially transferring the request packet by each router based on the multicast routing table, the request packet is made to reach the sending host by following the same route as the multicast data transmission route. Can do.

  The request packet that has reached the transmission host in this way is detected by the request detection means, and in response to this, a response packet corresponding to the request packet is generated by the return means, and the reception host that is the transmission source of this request packet To the multicast network. This response packet is detected in the same way as the request packet described above by the detecting means provided in each router, and in response to this detection, the forwarding means performs forwarding processing based on the multicast routing table. Therefore, the response packet from the sending host is also transmitted to the receiving host through the same route as the multicast data transmission route, and the reachability is verified by the verification means based on whether or not the response packet is returned. .

A second multicast trace route system according to the present invention is the above-described first multicast trace route system, wherein the control packet generation means and the return means are provided with a replacement means and an address insertion means, and are compared with the detection means and the request detection means. And a transfer means is provided with an extraction means and a search means.
The principle of the second multicast trace route system according to the present invention is as follows.

  In the control packet generation means provided in the receiving host and the return means provided in the transmission host of the first multicast trace route system described above, the replacement means displays the information field indicating the protocol type in the control packet by ICMP as multicast data. It is replaced with a specific bit string indicating that it is a control packet for tracking the path of The address insertion means inserts a multicast group address indicating the multicast data to be tracked into the data portion of the control packet by ICMP. Further, in the detecting means provided in each router and the request detecting means provided in the transmission host, the collating means matches the content of the information field indicating the protocol type in the received control packet with the specific bit string described above. Sometimes, a detection result indicating that a trace route packet or a response packet has been detected is output. Further, in the transfer means provided in each router, the extraction means extracts the multicast group address from the data part of the trace route packet detected by the detection means. The search means searches the multicast routing table for the route information corresponding to the extracted multicast group address, and provides the route setting for transferring the trace route packet.

The operation of the second multicast trace route system configured as described above is as follows.
In the control packet generation means of the reception host and the return means of the transmission host, for example, the protocol field of the control packet by ICMP is replaced with a specific bit string different from any of the bit strings indicating other protocols by the replacement means, and the address insertion means By inserting an appropriate multicast group address in the data portion of the control packet, a request packet for requesting tracking of the transmission path of multicast data and a response packet for the request packet are generated.

Since the request packet and the response packet generated in this way have a specific bit string set in the protocol field, this protocol field is detected by the matching means provided in the detection means of each router or the request detection means of the sending host. Can be reliably detected by collating the above-mentioned contents with the specific bit string described above.
The multicast group address set in the data part of the request packet and the response packet generated as described above is extracted by the extraction means provided in the transfer means of the router, and the multicast routing table search process by the search means As a result, the request packet and the response packet can be transferred by reliably following the transmission path of the tracked multicast data.

A third multicast trace route system according to the present invention is the above-described first multicast trace route system, wherein the control packet generation means and the return means are provided with setting means and address insertion means, and the detection means and the request detection means are determined. And a transfer means is provided with an extraction means and a search means.
The principle of the third multicast trace route system according to the present invention is as follows.

  In the control packet generation means provided in the receiving host and the return means provided in the transmission host of the first multicast trace route system described above, the setting means sets the multicast data in the information field indicating the procedure type in the control packet by ICMP. The procedure identification information indicating the procedure type in the route tracking in a predetermined format is set. The address insertion means inserts a multicast group address indicating the multicast data to be tracked into the data portion of the control packet by ICMP. Further, in the detecting means provided in each router and the request detecting means provided in the transmission host, the determining means determines whether or not the content of the information field indicating the procedure type in the received control packet is procedure identification information. To do. Further, in the transfer means provided in each router, the extraction means extracts the multicast group address from the data part of the trace route packet detected by the detection means. The search means searches the multicast routing table for the route information corresponding to the extracted multicast group address, and provides the route setting for transferring the trace route packet.

The operation of the third multicast trace route system configured as described above is as follows.
In the control packet generation means of the reception host and the return means of the transmission host, for example, in the control packet type (TYPE) field by ICMP, a specific bit string different from any of the bit strings indicating each information type in the trace route procedure by the setting means The procedure identification information indicating each procedure in the multicast trace route is set. Further, an appropriate multicast group address is inserted into the data portion of this control packet by the address insertion means. In this manner, a request packet for requesting tracking of the transmission path of multicast data and a response packet for the request packet are generated.

  In the trace route packet including the request packet and the response packet generated in this way, the procedure identification information represented by the bit string specific to the multicast trace route is set in the type field. A determination unit provided in the request detection unit of the host determines whether or not the content of the type field is the procedure identification information described above, and determines a control packet including the procedure identification information based on the determination result. Thus, the request packet and the response packet can be reliably detected.

  The multicast group address set in the data part of the request packet and the response packet generated as described above is extracted by the extraction means provided in the transfer means of the router, and the multicast routing table search process by the search means As a result, the request packet and the response packet can be transferred by reliably following the transmission path of the tracked multicast data.

The fourth multicast trace route system according to the present invention is the above-described first multicast trace route system, wherein the verification means includes a time measurement means and a failure detection means.
The principle of the fourth multicast trace route system according to the present invention is as follows.

  In the verification means provided in the receiving host of the first multicast trace route system described above, the time measuring means measures the elapsed time from the transmission of the request packet by the control packet generation means to the reception of the response packet for the request packet. The failure detection unit detects a failure in the transmission path of the multicast data when the elapsed time measured by the timing unit exceeds a predetermined threshold.

The operation of the fourth multicast trace route system configured as described above is as follows.
The request packet sent from the receiving host is accurately transmitted along the multicast data transmission path to the sending host, and the elapsed time until the response packet from the sending host reaches the receiving host is the verification means for the receiving host. It is measured by the time measuring means provided for. As described above, the request packet and the response packet are transmitted along the transmission path of the multicast data accurately, and the time required for going back and forth through the transmission path is, for example, between the receiving host and the transmitting host. It can be assumed in advance based on the number of hops between them. Therefore, by comparing the elapsed time measured as described above with a predetermined threshold appropriately determined by the failure detection means, it is possible to reliably detect a failure in the transmission path of the multicast data.

The fifth multicast trace route system according to the present invention is the same as the first multicast trace route system described above, wherein the transfer means is provided with an abnormality notification means and the verification means is provided with a notification detection means.
The principle of the fifth multicast trace route system according to the present invention is as follows.

  In the transfer means provided in each router of the first multicast trace route system described above, when the abnormality notification means cannot find an appropriate route from the multicast routing table, a control packet indicating an abnormality in the multicast routing table And send the control packet back to the receiving host. In the verification means provided in the receiving host, the notification detection means detects an abnormality related to the router that is the source of the control packet in response to the reception of the control packet indicating the abnormality of the multicast routing table.

The operation of the fifth multicast trace route system configured as described above is as follows.
When a request packet cannot be transferred to the sending host due to an abnormality in the multicast routing table, a control packet indicating that fact is generated and returned to the receiving host by the abnormality notifying means provided in the router, and the receiving host In response to the reception of this control packet, the notification detecting means provided in the above detects an abnormality of the source router. For example, if the IP address of the router in which an abnormality in the multicast routing table is detected is indicated in the control packet described above, information indicating the location (router) where the failure occurred on the multicast data transmission path is reliably transmitted to the receiving host. , It is possible to reliably identify the location where the abnormality occurred.

  As described above, according to the multicast trace route system according to the present invention, the transmission route through which multicast data is transmitted regardless of whether the route passing through the rendezvous point or the shortest route based on the SPT is selected. Thus, it is possible to exchange the dedicated control packet (trace route packet) with certainty, so that the reachability of the multicast data transmission path can be properly evaluated.

Further, as described in the second and third multicast trace route systems, the trace route packet described above can be generated by replacing a part of a general ICMP control packet with appropriate information. .
Further, in the fourth multicast trace route system described above, the reachability of the transmission path of the multicast data can be reliably determined based on whether or not the process of exchanging the trace route packet described above is normally completed, On the other hand, in the fifth multicast trace route system, it is possible to detect a router in which a problem has occurred in the multicast routing table. Furthermore, when confirming the reachability of the transmission path of multicast data, trace route packets are exchanged with each of a plurality of routers on this transmission path, and the paths to these routers are sequentially confirmed. As a result, it is possible to identify the fault location that has occurred on the transmission path.

  If such a multicast trace route system is used, when a failure occurs in a service such as a video distribution service for members, the member who is a user of the service can transmit the multicast data as described above. By verifying the reachability of the service and having the service provider report it, it is possible to quickly identify the location of the failure and to promptly restore the service, so that the serviceability can be greatly improved.

  Of course, in cases such as when the IP address of the router on the transmission path is hidden, it is not necessary to pinpoint the fault location, but the fault location is sufficient to facilitate the subsequent recovery process. It is possible to obtain information that limits the range in which.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of a multicast trace route system according to the present invention.
In FIG. 1, two reception hosts 210a and 210b and a transmission host 230 are connected via a multicast network composed of six routers 220a to 220f.

  The router 220 shown in FIG. 1 includes a multicast routing table 223 together with the unicast routing table 224. The transfer control unit 225 uses the communication processing unit 221 based on the unicast routing table 224 and the multicast routing table 223. By controlling the transfer operation, the packet that has reached the router 220 is transferred to the next router 220 or the destination of the packet through an appropriate route.

In FIG. 1, the detailed configuration of only the router 220f is shown, and the detailed configuration of the other routers 220a to 220e configured in the same manner is omitted.
Further, in the receiving host 210a shown in FIG. 1, the reachability evaluation unit 214, for example, sends a request packet forming unit 212 to a predetermined later-described predetermined response in response to a path tracking request input by a user of the receiving host 210a. Instructs to form a traceroute packet with format.

FIG. 2 shows a configuration example of the trace route packet.
For example, the request packet forming unit 212 shown in FIG. 1 is first shaded in the protocol field (FIG. 2A) provided in the header of the control packet by ICMP as shown in FIG. 2), a protocol identifier indicating that the packet is a trace route packet for confirming a transmission path of multicast data (in FIG. 2A, the protocol identifier is indicated as a code “101”) is set. Further, the request packet forming unit 212 indicates in the type field provided in the data portion (shown by shading in FIG. 2A) that the request is a route trace request as information indicating the type of the trace route packet. A type identifier (for example, type code “0”) is set, and a corresponding multicast group address field (shown by shading in FIG. 2A) provided in the data portion is also being received. Appropriate multicast group address indicating the multicast group is added.

The request packet formed in this way is sent to the multicast network via the communication processing unit 211, and is first passed to the router 220f adjacent to the receiving host 210a.
In the router 220f shown in FIG. 1, the control packet extraction unit 222 sends a packet passed through an interface (shown with a circle in FIG. 1) between the router 220f and the adjacent routers 220c and 220e. The trace route packet in which the above-described specific bit string is set is detected by referring to the protocol field. Then, the multicast group address included in the detected trace route packet is extracted, transferred to the transfer control unit 225, and used for transfer control processing of this trace route packet.

  In the multicast routing table 223 shown in FIG. 1, information indicating the interface corresponding to the route to the transmission host 230 that is the transmission source of the corresponding multicast data and the reception that is the transmission destination correspond to each multicast group address. In addition to information indicating the interface corresponding to the route to the host 210, information indicating whether or not the corresponding transmission path is currently used is stored.

  Here, for example, along with the start of distribution of multicast data from the sending host 230, a transmission path for branching to the routers 220d and 220f is set by the router 220c using the router 220c as a rendezvous point, and later to the receiving host 210a. The content of the information stored in the multicast routing table 223 described above will be described by taking as an example a case where the transmission path is switched to the shortest path via the routers 220e and 220f based on the SPT. In this case, in the multicast routing table 223, the interface corresponding to the router 230c adjacent to the router 220f and the receiving host 210a in the transmission path in which the rendezvous point is set is associated with the multicast group address indicating the multicast data described above. Two pieces of information, that is, route information indicating the interface corresponding to the router 220e and the receiving host 210a adjacent to each other in the shortest path are stored. Then, information indicating that it is currently used (“forwarding”) is set as the status information corresponding to the route information indicating the shortest path, while the status information corresponding to the route information indicating the transmission route for which the rendezvous point is set. Is set to information ("prune") indicating that it is not used.

  Accordingly, the transfer control unit 225 refers to the multicast routing table 223 based on the multicast group address received from the control packet extraction unit 222 as described above, so that the multicast data transmission path that is currently valid is related. Route information can be obtained. Based on this path information, the transfer control unit 225 determines to which interface the trace route packet arrived from the receiving host 210a should be sent to the communication processing unit 221, and the communication processing unit 221 receives an appropriate interface. To send the above-described trace route packet.

  In this way, each router 220 performs transfer processing based on the multicast routing table 223 in response to reception of the trace route packet, and sequentially forwards the data to each router 220. Regardless of whether it is valid, the trace route packet sent out by the receiving host 210a can be accurately traced back on the transmission path of the multicast data, and the sending route can be made to reach the sending host 230.

  In this way, the trace route packet for requesting the tracking of the transmission path arrives at the transmission host 230 shown in FIG. 1, and in the course of reception processing by the communication processing unit 231, the request packet detection unit 232 is based on the protocol field described above. Is detected, the response packet forming unit 233 forms a trace route packet indicating a response to the request packet.

  At this time, the response packet forming unit 233 sets a unique protocol identifier in the protocol field of the control packet by ICMP as well as the route tracking in the data unit in the same manner as the request packet forming process in the request packet forming unit 212 described above. A trace route packet is formed by adding and processing a type identifier indicating a response and a multicast group address, and sending the packet to the multicast network via the communication processing unit 231.

  The response packet sent to the multicast network in this way is detected by the control packet extraction unit 222 provided in each router 220 on the same transmission path as the multicast data according to the same procedure as the transfer of the request packet described above. Are transferred according to the multicast routing table 223. That is, the response packet described above is first transferred to the router 220e based on the multicast routing table 223 provided in the router 220a, and then returned to the receiving host 210a via the router 220f.

  Accordingly, a response packet arrives at the communication processing unit 211 of the receiving host 210a shown in FIG. 1 within a certain time after instructing the transmission of the request packet described above, and this response packet is detected by the response packet detection unit 213. The reachability evaluation unit 214 determines that the reachability of the multicast data transmission path has been confirmed, and can notify the user to that effect. On the other hand, if the response packet is not returned even after the estimated time for the round-trip time of the control packet has elapsed, the reachability evaluation unit 214 determines that some failure has occurred in the multicast data transmission path. And notify the user.

  Thus, according to the multicast trace route system shown in FIG. 1, dedicated trace route packets are exchanged through the same route as the transmission route through which multicast data is transmitted from the transmission host to the reception host. Thus, the reachability of the multicast data transmission path is evaluated, so the reachability of the multicast data transmission path can be reliably and properly determined.

Note that the trace route packet according to the present invention can be realized by an extended format of the control packet by ICMP.
For example, as shown in FIG. 2B, in the request packet forming unit 212 and the response packet forming unit 233, the type field of the control packet (Tracert) by ICMP (shown with shading in FIG. 2B) (See Fig. 2 (c)) to indicate that it is a trace route related to the transmission path of multicast data, and a field for setting a multicast group address is provided in the data part to form a trace route packet May be.
(Second Embodiment)
FIG. 3 shows a second embodiment of the multicast trace route system according to the present invention.

3 that are the same as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG. 1 and description thereof is omitted.
The receiving host 210a illustrated in FIG. 3 includes a control packet detection unit 215, a tracking control unit 216, and an evaluation notification unit 217 instead of the response packet detection unit 213 and the reachability evaluation unit 214 illustrated in FIG. Has been. On the other hand, each router 220 shown in FIG. 3 includes a control packet forming unit 226 in addition to each unit shown in FIG.

  The tracking control unit 216 shown in FIG. 3 controls the transmission operation of the request packet by the request packet forming unit 212 based on, for example, the tracking instruction from the user and the detection result by the control packet detection unit 215 to transmit the request packet. The path tracking process is controlled, and the information obtained by this tracking process is passed to the evaluation notification unit 217 for use in the reachability evaluation process for the transmission path of multicast data.

Also, in the router 220f shown in FIG. 3, the control packet forming unit 226 receives the information indicating the state of the transmission path in the router 220 in accordance with the instruction from the transfer control unit 225, and the type of the trace route packet in the above-described format. A reply packet set in the field is formed and returned to the transmission source of the request packet via the communication processing unit 221.
FIG. 4 is a flowchart showing the tracking operation regarding the transmission path of multicast data. FIG. 5 is a flowchart showing the trace route packet transfer operation.

In response to the tracking request from the user, the tracking control unit 216 shown in FIG. 3 first instructs the request packet forming unit 212 to form a request packet whose lifetime (TTL) is 1 (step of FIG. 4). In response to this, the request packet forming unit 212 forms the request packet as described above and sends it to the multicast network (step 302).
When the request packet sent in this way reaches the router 220 and is detected by the control packet extraction unit 222 (step 311 in FIG. 5), the transfer control unit 225 sets the type field of the extracted packet. Based on the generated code, it is determined that the packet is a request packet (step 312), and then the lifetime of the request packet is confirmed.

  When the lifetime of the request packet detected in step 311 described above is a numerical value “1” (affirmative determination in step 313), the transfer control unit 225 discards the request packet, and sends the request packet to the control packet forming unit 226. A reply packet in which a code indicating arrival at the own router is set in the type field is formed (step 314). At this time, for example, the control packet forming unit 226 adds a code indicating the control information “Time Exceeded” in the general trace route function to the type field newly provided in the data portion as shown in FIG. A reply packet can be formed by setting as a code indicating arrival at the own router. A reply packet can also be formed by setting the control information as shown in FIG. 2C in the type field of the control packet by ICMP.

The reply packet formed in this way is sent by the communication processing unit 221 to the reception host (step 315 in FIG. 5) and detected by the control packet detection unit 215 of the reception host 210a shown in FIG.
In response to the detection of the return packet, the tracking control unit 216 proceeds to step 305 as an affirmative determination of step 303 in FIG. 4, and further proceeds to step 306 based on the information set in the type field of the return packet. The tracking state of the transmission path indicated by this reply packet is determined.

  In the reply packet described above, the arrival of the request packet up to the router 220f is indicated by the control information set in the type field (affirmative determination in step 306), so that the tracking control unit 216 confirms the arrival of the router (here Then, in order to trace the transmission path ahead of the router 220f), the lifetime is extended (step 307), the process returns to step 302, the request packet forming unit 212 forms a request packet, and the communication processing unit 211 is used. To send.

  When the request packet whose lifetime has been extended in this way arrives at the router 220f and is extracted by the control packet extraction unit 222, the transfer control unit 225 determines this request as a negative determination in step 313 shown in FIG. Performs packet transfer processing. At this time, the transfer control unit 225 decrements the lifetime (step 316) and, based on the multicast group address extracted by the control packet extraction unit 222, goes back from the multicast routing table 223 to the transmission host 230 side. The transfer destination for the search is searched (step 317).

  For example, if the multicast routing table 223 corresponding to the multicast group address described above is normally formed in the router 220f, an appropriate transfer destination (for example, an interface with the router 220e) is searched in step 317 described above. As a positive determination in step 318, the transfer control unit 225 causes the request packet to be transferred to the searched transfer destination via the communication processing unit 221 (step 319), and completes the transfer process related to the request packet.

  In response to the request packet transferred in this way, the adjacent router 220e performs the above-described processing from step 311 to step 315, and the reply packet formed in this process reaches the receiving host 210a. The arrival to the router 220e is confirmed, and in response to this, the receiving host 210a sends out a request packet with an extended lifetime.

In this way, by sequentially sending request packets with extended lifetimes and confirming the arrival of the trace route packet by the return packet from each router 220, each router 220 on the multicast data transmission path can be reached. This transmission path can be traced back from the reception host 210a side to the transmission host 230 while sequentially confirming the reachability of the transmission host.
Then, when a reply packet is returned from the adjacent router 220 and a response packet from the transmission host 230 is returned with respect to the request packet transferred in this way along the transmission path, the transfer control unit 225. The process proceeds to step 321 as a negative determination of step 312 shown in FIG. 5, and transfers this reply packet or response packet to the receiving host 210 side designated as the destination via the communication processing unit 221.

  The response packets sent by the sending host 230 in this way are sequentially transferred in the multicast network, and when the packet reaches the receiving host 210 (for example, the receiving host 210a) that is the source of the request packet, it is shown in FIG. As an affirmative determination in step 305 shown in FIG. 4, the tracking control unit 216 sends an evaluation result indicating that the reachability of the transmission path of the multicast data from the transmission host 230 to its own device is confirmed via the evaluation notification unit 217. The user is notified (step 306) and the tracking process is terminated.

  On the other hand, when a reply packet or a response packet is not returned even after a predetermined time has elapsed since each request packet was sent (No determination in step 303), the tracking control unit 216 indicates that a failure has been detected in the transmission path. The evaluation result is notified to the user via the evaluation notification unit 217 (step 309), and the process is terminated. Here, for example, if the evaluation result passed to the evaluation notification unit 217 by the tracking control unit 216 includes information indicating the lifetime applied to the last transmitted request packet, the reachability is confirmed by the user. Information about the section can be provided. Furthermore, when the reply packet is received, the source address is collected, and the collected source address is used together with the evaluation result for the processing of the evaluation notification unit 217, so that the location where the failure has occurred can be identified more accurately. can do.

As described above, in the multicast trace route system shown in FIG. 3, in the process of tracing the transmission path of multicast data, for example, when a failure occurs in the interface between the router 220f and the router 220c, this failure Sufficient information can be obtained in order to accurately limit the location where the occurrence occurs.
Further, in this multicast trace route system, even when the arrival of the transmission path cannot be realized due to an abnormality occurring in any of the multicast routing tables 223 provided in each router 220, the cause can be accurately determined.

  For example, in the multicast routing table 223 provided in the router 220e, when the route information corresponding to the multicast group address of the tracked transmission route is not normally formed, an appropriate transfer destination cannot be searched in step 317. This is a negative determination in step 318 shown in FIG. At this time, the transfer control unit 225 causes the control packet forming unit 226 to form a reply packet including control information indicating that there is an error in the multicast routing table (step 320), and sends the reply packet via the communication processing unit 221. The message is sent to the receiving host 210a (step 315), and the process is terminated.

  When the reply packet sent in this way reaches the receiving host 210a, the tracking control unit 216 proceeds to step 308 as a negative determination in step 306, and the router (in this case, the router of the reply packet) 220e), the user is notified of the evaluation result indicating that an error has occurred in the multicast routing table 223 via the evaluation notification unit 217, and the process is terminated.

  As described above, according to the multicast trace route system according to the present invention, it is possible to check the reachability of the multicast data transmission path accurately from the receiving host side to the sending host. In the field of video content distribution services and the like, when a transmission path failure occurs, it is possible to isolate the failure part at an early stage to improve the efficiency of the recovery work.

  Of course, since the operation from the receiving host side is necessary, the cooperation of the user is indispensable. However, as described above, in the multicast trace route system according to the present invention, in the process of sending and receiving the trace route packet, Since various kinds of information useful for identification can be collected, it is possible to guarantee a quick recovery operation, so that the user's burden can be sufficiently met.

  As a technology for confirming the reachability of the transmission path from each monitoring base to the transmission host that sends the video of the monitoring camera in a system that distributes video captured by the monitoring camera to multiple monitoring bases via a multicast network It is also possible to use this, and this makes it possible to improve the reliability of such a monitoring system.

It is a figure which shows 1st Embodiment of the multicast trace route system concerning this invention. It is a figure which shows the structural example of a trace route packet. It is a figure which shows 2nd Embodiment of the multicast trace route system concerning this invention. It is a flowchart showing the tracking operation | movement regarding the transmission path | route of multicast data. It is a flowchart showing the transfer operation | movement of a trace route packet. It is explanatory drawing of a multicast network.

Explanation of symbols

210 receiving host 211, 221, 231 communication processing unit 212 request packet forming unit 213 response packet detecting unit 214 reachability evaluating unit 215 control packet detecting unit 216 tracking control unit 217 evaluation notifying unit 220 router 222 control packet extracting unit 223 multicast routing table 224 Unicast routing table 225 Transfer control unit 226 Control packet formation unit 230 Transmission host 232 Request packet detection unit 233 Response packet formation unit

Claims (9)

In a trace route system in a multicast network composed of a plurality of routers having a multicast routing table for transferring multicast data sent from a sending host to each of a plurality of receiving hosts,
At least one of the plurality of receiving hosts is
Control packet generation means for generating a request packet including identification information indicating in a predetermined format that the packet is a control packet for requesting tracking of the transmission path of the multicast data, and sending the request packet to the multicast network with the transmission host as a destination When,
Verification means for verifying the reachability of the multicast data transmission path based on the return status of the response packet from the transmission host to the request packet;
The control packet generation means generates the request packet by manipulating a part of an information field included in an ICMP control packet,
The sending host is
Request detection means for detecting the request packet from a control packet reached via the multicast network;
In response to detection of the request packet by the detection means, a return means for returning a response packet including the identification information to the receiving host,
The plurality of routers are:
Detecting means for detecting a trace route packet including the request packet and the response packet from a control packet reached via the multicast network;
A multicast trace route system comprising: transfer means for transferring the trace route packet based on the multicast routing table in response to detection of the trace route packet by the detection means. The multicast trace route system according to claim 1,
The control packet generating means provided in the receiving host and the return means provided in the transmitting host are:
Replacement means for replacing the information field indicating the protocol type in the control packet by ICMP with a specific bit string indicating that the packet is a control packet for tracking the path of multicast data;
Address insertion means for inserting a multicast group address indicating multicast data to be tracked into the data portion of the control packet by the ICMP,
The detection means provided in the router and the request detection means provided in the transmission host are:
A verification unit that outputs a detection result indicating that a request packet or a response packet is detected when the content of the information field indicating the protocol type in the received control packet matches the specific bit string described above,
Transfer means provided in each of the routers,
Extraction means for extracting a multicast group address from the data portion of the trace route packet detected by the detection means;
A multicast trace route system, comprising: search means for searching for route information corresponding to the extracted multicast group address from the multicast routing table and for setting a route for transferring the trace route packet. The multicast trace route system according to claim 1,
The control packet generating means provided in the receiving host and the return means provided in the transmitting host are:
Setting means for setting procedure identification information indicating a procedure type in the path tracking of multicast data in a predetermined format in an information field indicating the procedure type in a control packet by ICMP;
Address insertion means for inserting a multicast group address indicating multicast data to be tracked into the data portion of the control packet by the ICMP,
The detection means provided in the router and the request detection means provided in the transmission host are:
Determining means for determining whether or not the content of the information field indicating the procedure type in the received control packet is the procedure identification information;
Transfer means provided in each of the routers,
Extraction means for extracting a multicast group address from the data portion of the trace route packet detected by the detection means;
A multicast trace route system, comprising: search means for searching for route information corresponding to the extracted multicast group address from the multicast routing table and for setting a route for transferring the trace route packet. The multicast trace route system according to claim 1,
The verification means provided in the receiving host includes:
Time measuring means for measuring an elapsed time from transmission of a request packet by the control packet generating means to reception of a response packet to the request packet;
A multicast trace route system, comprising: failure detection means for detecting a failure in a transmission path of the multicast data when the elapsed time measured by the time measuring means exceeds a predetermined threshold value. The multicast trace route system according to claim 1,
Transfer means provided in each of the routers,
When an appropriate route cannot be retrieved from the multicast routing table, a control packet indicating an abnormality in the multicast routing table is generated, and an abnormality notification means for returning the control packet to a receiving host is provided.
The verification means provided in the receiving host includes:
A multicast trace route system, comprising: a notification detection unit that detects an abnormality related to a router that is a source of the control packet in response to reception of a control packet indicating an abnormality in the multicast routing table.   In a trace route system in a multicast network composed of a plurality of routers having a multicast routing table for transferring multicast data sent from a sending host to each of a plurality of receiving hosts,
  At least one of the plurality of receiving hosts is
  Control packet generation means for generating a request packet including identification information indicating in a predetermined format that the packet is a control packet for requesting tracking of the transmission path of the multicast data, and sending the request packet to the multicast network as the destination When,
  Verification means for verifying the reachability of the multicast data transmission path based on the return status of the response packet from the transmission host to the request packet;
  The sending host is
  Request detection means for detecting the request packet from a control packet reached via the multicast network;
  In response to detection of the request packet by the detection means, a return means for returning a response packet including the identification information to the receiving host,
  The plurality of routers are:
  Detecting means for detecting a trace route packet including the request packet and the response packet from a control packet reached via the multicast network;
  Transfer means for transferring the trace route packet based on the multicast routing table in response to detection of the trace route packet by the detection means;
  The control packet generating means provided in the receiving host and the return means provided in the transmitting host are:
  Replacement means for replacing the information field indicating the protocol type in the control packet by ICMP with a specific bit string indicating that the packet is a control packet for tracking the path of multicast data;
  Address insertion means for inserting a multicast group address indicating multicast data to be tracked into the data portion of the control packet by the ICMP,
  The detection means provided in the router and the request detection means provided in the transmission host are:
  A verification unit that outputs a detection result indicating that a request packet or a response packet is detected when the content of the information field indicating the protocol type in the received control packet matches the specific bit string described above,
  Transfer means provided in each of the routers,
  Extraction means for extracting a multicast group address from the data portion of the trace route packet detected by the detection means;
  Search means for searching for route information corresponding to the extracted multicast group address from the multicast routing table and for setting a route for transferring the trace route packet is provided.
  Multicast trace route system characterized by that.   In a trace route system in a multicast network composed of a plurality of routers having a multicast routing table for transferring multicast data sent from a sending host to each of a plurality of receiving hosts,
  At least one of the plurality of receiving hosts is
  Control packet generation means for generating a request packet including identification information indicating in a predetermined format that the packet is a control packet for requesting tracking of the transmission path of the multicast data, and sending the request packet to the multicast network with the transmission host as a destination When,
  Verification means for verifying the reachability of the multicast data transmission path based on the return status of the response packet from the transmission host to the request packet;
  The sending host is
  Request detection means for detecting the request packet from a control packet reached via the multicast network;
  In response to detection of the request packet by the detection means, a return means for returning a response packet including the identification information to the receiving host,
  The plurality of routers are:
  Detecting means for detecting a trace route packet including the request packet and the response packet from a control packet reached via the multicast network;
  Transfer means for transferring the trace route packet based on the multicast routing table in response to detection of the trace route packet by the detection means;
  The control packet generating means provided in the receiving host and the return means provided in the transmitting host are:
  Setting means for setting procedure identification information indicating a procedure type in the path tracking of multicast data in a predetermined format in an information field indicating the procedure type in a control packet by ICMP;
  Address insertion means for inserting a multicast group address indicating multicast data to be tracked into the data portion of the control packet by the ICMP,
  The detection means provided in the router and the request detection means provided in the transmission host are:
  Determining means for determining whether or not the content of the information field indicating the procedure type in the received control packet is the procedure identification information;
  Transfer means provided in each of the routers,
  Extraction means for extracting a multicast group address from the data portion of the trace route packet detected by the detection means;
  Search means for searching for route information corresponding to the extracted multicast group address from the multicast routing table and for setting a route for transferring the trace route packet is provided.
  Multicast trace route system characterized by that.   In the multicast trace route system according to claim 6 or 7,
  The verification means provided in the receiving host includes:
  Time measuring means for measuring an elapsed time from transmission of a request packet by the control packet generating means to reception of a response packet to the request packet;
  A failure detection unit that detects a failure in the transmission path of the multicast data when the elapsed time measured by the timing unit exceeds a predetermined threshold value
  Multicast trace route system characterized by that. In the multicast trace route system according to claim 6 or 7,
  Transfer means provided in each of the routers,
  When an appropriate route cannot be retrieved from the multicast routing table, a control packet indicating an abnormality in the multicast routing table is generated, and an abnormality notification means for returning the control packet to a receiving host is provided.
  The verification means provided in the receiving host includes:
  In response to reception of a control packet indicating an abnormality in the multicast routing table, a notification detection unit is provided for detecting an abnormality related to a router that is a source of the control packet.
  Multicast trace route system characterized by that.

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