JP4530039B2 - Packet relay device - Google Patents

Description

The present invention relates to a multicast network in which a transmission source server is limited, and particularly to a technique for connecting terminals that cannot specify a transmission source server.

Multicast is a technique for simultaneously transmitting packets to a plurality of destinations on the Internet. Compared to sending a packet to a single destination multiple times, it can be sent to multiple destinations with a smaller amount of packets. Suitable for media communication.

Today, however, multicast networks are not so popular in the world. One of the major reasons is the complexity of multicast routing. DVMRP (
Distance Vector Multicast Routing Protocol (RFC1075) and PIM-DM (Protocol In
Multicast routing protocol such as dependent Multicast-Dense Mode: draft-ietf-pim-dm-new-v2-01.txt) is simple, but multicast traffic is also sent to segments that do not require transmission (units of network configuration) However, there is a drawback that the network utilization efficiency is poor. Therefore, PIM- overcomes this drawback
SM (Protocol Independent Multicast-Sparse Mode: RFC2362) is usually used in multicast network operations. Although PIM-SM allows multicast traffic to flow only to the minimum necessary segments, the overhead of multicast transmission tree calculation is large, so there are problems that the protocol is complicated, difficult to operate, and the load on the router increases. (Asaeda, “Source Specific Multicast
New Communication Architecture by ”, Information Processing, March 2002, Vol 43, No. 3, pp
260-265)
A promising technique proposed to eliminate this complexity is Source-Specific Multicast. In conventional n-to-n multicast communication, a multicast receiving terminal sends a request to join a group.
In source-limited multicast, when a multicast receiving terminal transmits a request to join a group, a multicast transmission source is specified at the same time. The goal is to specify the multicast source as the receiver and limit the processing to one-to-n multicast communication to simplify multicast routing (draft-ietf-ssm-over
view-00.txt). Considering that many cases where multicast is used are streaming from a small number of servers, the user needs for multicast can be satisfied even if processing is limited to 1-to-n communication.

The major difference between source-limited multicast routing and traditional multicast routing is that end-user terminals must specify their source server along with the multicast group address when joining the multicast group. . In order for an end user's terminal to participate in a source-only multicast network, the corresponding multicast group management protocol (I
IGMPv3 = Internet Group Management Protocol Version 3 for Pv4, ML for IPv6
Dv2 = Multicast Listener Discovery Version 2) must be supported.
However, there are not many terminals that support IGMPv3 and MLDv2 today. Also I
Since GMPv3 and MLDv2 have higher implementation costs than the conventional source-unlimited multicast group management protocol, it is expected that GMPv3 and MLDv2 will not be implemented in terminals that require low cost, such as information appliances.

For this reason, some proposals have been made for connecting terminals that do not support IGMPv3 and MLDv2 to a source-limited multicast network. Cisco IGMPv3
In Lite, by incorporating an IGMPv3 conversion library with limited functions into the end user terminal application, the end user terminal application
Even if v3 is not supported, it is possible to participate in a source-limited multicast network through a conversion library. Cisco URD (URL Rendezvous Di
scovery), the end user specifies the source server to the router using HTTP (Hyper Text Transfer Protocol), so even if the end user terminal or application does not support IGMPv3, the source is limited to the router A request to join a multicast network can be notified. In addition to these, by participating statically in a multicast group from a specific source for a line with the router itself, even if the end user terminal on that line does not support IGMPv3, Multicast traffic from the source can also flow (Cisco "Source-Specific Multicast with IGMPv3, IGMPv
3lite, and URD feature module, Release 12.1 (5) T ", http://www.cisco.com/u
nivercd / cc / td / doc / product / software / ios121 / 121newft / 121t / 121t5 / dtssm5t.ht
m).

One of the advantages of source-limited multicast is that network resources are prevented from being wasted due to multicast transmission from unspecified terminals because only multicast transmission from specific terminals is allowed. A proposal to improve source-only multicasting from this perspective is the multicast control protocol proposed by Sonera's Lehtonen (draft-lehtonen-magma-mcop-00.tx
t). This system can collectively manage filtering of source-limited multicast participation requests by the multicast control server by inquiring whether the multicast control device can participate when the multicast relay device receives the source-limited multicast participation request. System.
"New Communication Architecture Using Source Specific Multicast", Information Processing, March 2002, Vol 43, No. 3, pp. 260-265

There are two problems with the conventional technique for connecting a terminal that does not support source-limited multicast to a source-limited multicast network. One is that it can only be handled by end-user computers and applications.
IGMPv3 Lite and URD have this drawback. In the case of IGMPv3 Lite, it is necessary to reconstruct the application using a conversion library. In the case of URD, the user needs to separately participate in the source-limited multicast network separately from the application. Therefore, compared with the source non-limitation type multicast network, the user's trouble is increased. This problem does not occur when the router itself participates in multicast multicast. However, in this case, even if there is no actual multicast participant, multicast traffic flows on the line where the router statically joins the multicast group. For this reason, the user is forced to be congested by unnecessary use of line bandwidth and unnecessary line cost.

The present invention solves these two problems simultaneously. That is, it is an issue to be solved by the present invention to dynamically join or leave an end user terminal that supports only source-unlimited multicast to / from a source-limited multicast network without changing the setting. .

In the present invention, a source non-restricted multicast group join request sent from the terminal to the router is converted into a source-restricted multicast group join request. For conversion, a multicast transmission source management table is used. This table manages the correspondence between the router, the multicast group address, and the multicast group management packet source terminal and the corresponding source server. This table is similar to the table used in the multicast control protocol.

Using this table, the router accommodating the end user terminal converts the source non-restricted multicast group participation request into a multicast group participation request limited to the transmission source server permitted by the network administrator. Also, when a router inquires about the existence of participants in a source-limited multicast group, the router searches the same table to confirm that participation in the multicast group from that source is permitted, and then the source is not limited Queries whether there are participants in the multicast group.

One aspect of the present invention is a packet relay apparatus that accommodates multicast client terminals, and requests for joining or leaving a multicast group from a multicast client terminal that cannot specify a multicast transmission source, and a multicast group that specifies the multicast transmission source. It is a packet relay device that converts and processes the request to join or leave. In this relay apparatus, the multicast transmission source to be specified can be determined based on the address of the multicast client terminal and the address of the multicast group requested to join or leave. More specifically, using a correspondence table of a multicast group address, a multicast client terminal address, and a corresponding multicast source address, a request to join or leave a multicast group is sent from a multicast client terminal that cannot specify a multicast source. When this occurs, refer to the correspondence table, and specify the multicast source address of the entry that includes the address of the multicast client terminal that made the join or leave request and the address of the multicast group that was requested to join or leave. And The multicast source address in the correspondence table is "Don't"
care "", it may be processed as a request to join or leave a multicast group that does not designate a multicast transmission source. The correspondence table may be built in the packet relay device, or Located in a separate device that is connected and accessible by a line.

Another aspect of the present invention is a packet relay apparatus that accommodates multicast client terminals, and a multicast client terminal that participates in a multicast group from a specific multicast transmission source is present in a certain network in response to a multicast participation inquiry. This is a packet relay device that can detect whether or not the multicast client terminal does not have a function of responding to a multicast participation inquiry for specifying a multicast transmission source. In this aspect, by searching a correspondence table of multicast group addresses, multicast client terminal addresses, and multicast source addresses corresponding to them, multicast client terminals participating in a multicast group from a specific multicast source are It can be detected whether it exists in a certain network.
Another aspect of the present invention is a packet relay apparatus that accommodates multicast client terminals, and manages correspondence between multicast groups, addresses of terminals that are clients of the multicast group, and addresses that are multicast group transmission sources. The packet relay apparatus includes a management table, and uses this table to convert a source non-restricted multicast group join request into a source-restricted multicast group join request.

Another aspect of the present invention is a method for converting a source-unlimited multicast group participation request into a source-limited multicast group participation request. In particular,
Allow the network administrator to the multicast network based on the multicast group address included in the request to join the multicast group from the terminal that supports only the transmission source unlimited multicast and the line where the join request has occurred. The transmission source server to be calculated is calculated from the multicast transmission source management table.
The multicast router converts the request for participation in the multicast group not limited to the transmission source into a request for participation in the multicast group from the transmission source server permitted by the network administrator. In addition, when a multicast router periodically checks whether there is a terminal that participates in a multicast group from a specific source server in a network, the multicast group address and the line on which the join request has been generated are also included. At the same time, the transmission source server permitted by the network administrator for the multicast network is calculated in the multicast transmission source management table. If the calculated transmission source server does not match the transmission source server to be examined, the multicast router determines that there is no terminal participating in the multicast address from the transmission source server on the line. When the calculated transmission source server matches the transmission source server to be examined, the multicast router does not specify the transmission source server and determines whether there is a terminal participating in the multicast group on the line. Check in a similar way. Here, whether or not a corresponding terminal is found, that is, whether or not a terminal participating in a multicast address from the transmission source server exists on the line. Another aspect is that a multicast client, a multicast relay apparatus accommodating the multicast client, a multicast group address, a multicast client address, and a multicast source address corresponding to the corresponding table, a transmission from the multicast client. When a request to join an original unspecified multicast group occurs, the source address corresponding to the multicast group address is searched from the address of the multicast client that made the join request based on the multicast source address correspondence table. This is a method for converting a request to join a multicast group for which the transmission source is not specified into a multicast group participation request for which the transmission source is specified. . In addition, in a network composed of a correspondence table of a multicast client, a multicast relay device accommodating the multicast client, a multicast group address, a multicast client address, and a multicast source address corresponding to them,
When an inquiry to join a multicast group from a specific source from a multicast relay device occurs on an interface with the multicast relay device,
This is a method of searching for a multicast source address defined by the network administrator corresponding to the multicast group from the address of the multicast relay device in the interface that transmits the participation inquiry based on the multicast source address correspondence table.

The scope of the present invention includes a network system that implements the above method and a network system that uses the above packet relay device.

By using the present invention, an end user terminal that supports only source-unlimited multicast can participate in the source-limited multicast network only by changing the multicast router that directly accommodates the end-user terminal.
Since the multicast router determines whether to join or leave the multicast based on the join request or leave request from the end user terminal, the multicast traffic will not flow to the end user when the end user no longer needs the multicast traffic.

  Embodiments of the present invention will be specifically described below.

FIG. 1 shows an overview of source limited multicast routing which is the subject of the present invention. FIG. 2 is an overall view of a source-limited multicast routing conversion apparatus using the present invention. FIG. 3 is a flowchart illustrating a method in which an edge router in a location that accommodates a terminal in a multicast network converts a non-source limited multicast group participation request into a multicast group participation request limited to a transmission source server permitted by a network administrator. FIG. 4 is a flowchart showing a method for converting an inquiry of a terminal participating in a source limited multicast group into a source non-limited multicast group participation request. 5 and 6
FIG. 7 introduces another embodiment of the present invention.

First, a general multicast communication implementation method will be described with reference to FIG. When multicast client terminal 100 joins a multicast group, terminal 1
A request to join the multicast group is transmitted to the multicast router 110 in the position that directly accommodates 00. A multicast group management protocol such as IGMPv2 or MLDv1 is used in the case of conventional source-unlimited multicast, and a multicast group management protocol such as IGMPv3 or MLDv2 is used in the case of source-limited multicast. The multicast router 110 receives a request to join the multicast group at the multicast group management packet processing unit 114 via the line 116. Multicast group management packet processor 1
14 notifies the multicast route control unit 112 of the received multicast participation request. The multicast route control unit 112 is a multicast router 121 in the transmission source direction among adjacent multicast router groups (in the case of source-limited multicast, it is a next hop router for reaching a designated source address by unicast. Source unrestricted) In the case of type multicast, it is confirmed that there has been a request to join the multicast group for the next hop router to reach the address called the rendezvous point defined by the network administrator corresponding to the group address by unicast. Notice. A multicast routing protocol such as PIM-SM is used for the group join / leave notification between the routers. At the same time, the multicast route control unit 112 sends a packet relay unit 118
Packets arrived from the router 121 to the multicast group (in the case of source-limited multicast, a condition from a specified source is added)
Is added to the line 116 where the multicast client terminal 100 is located.

By repeating this notification work and adding packet relay settings, all the multicast routers located between the multicast client terminal and the transmitting terminal in the network 120 can know the multicast route information (in the case of source-unlimited multicast, multicast Since only the multicast router between the client terminal and the rendezvous point multicast router knows the multicast route information, the multicast router between the rendezvous point and the sending terminal does not necessarily know the multicast route information. Since it is assumed that the location of the point is known, it is possible to reach the rendezvous point corresponding to the multicast group from the transmitting terminal. All the routers at the end can know the multicast route information, so when the multicast transmission server 130 in the multicast network 120 communicates with the multicast group, the terminal 100 passes through the multicast routers 122, 121, and 110. Communication will also flow.

The multicast group management unit 114 of the multicast router 110 periodically checks whether there is a multicast participant on the line 116 where the terminal 100 exists in order to grasp whether the terminal 100 is participating in the multicast group. . When the terminal 100 is participating in the multicast group, the terminal 100 returns a request for participation in the multicast group in response to the confirmation inquiry. The protocols used for these exchanges are IGMPv3 and MLDv2 in the case of a source-limited multicast inquiry, and IGMPv2 and MLDv1 in the case of a source-unlimited multicast. If the terminal 100 has not joined the multicast group, the terminal 100 does not reply anything. Therefore, when the multicast participation request is interrupted for a certain period of time on the line 116, the multicast router 110 determines that there are no terminals participating in the multicast group on the line 116, and the adjacent multicast router 121 in the transmission source direction receives the multicast group. A request to leave is sent using a multicast routing protocol such as PIM-SM.

At the same time, the multicast route control unit 112 sends a router to the packet relay unit 118.
The setting for relaying the packet that has arrived from 121 to the multicast group (in the case of source-limited multicast, a condition that the specified source is further added) to the network where multicast client terminal 100 is located is deleted.

By repeating this notification work and packet relay setting deletion, the loss of route information to the multicast group in the edge router 110 spreads to all multicast routers in the network 120, so even if the multicast transmission server 130 communicates to the multicast group, the terminal The communication will not reach 100.

Multicast client terminal for source-unlimited multicast
In the case of a request for participation in source limited multicast, a multicast transmission server is included in the participation request and withdrawal request advertised from 100 to the entire network 120 via the multicast router 110.
The terminal 100 advertises 130 address / multicast group address pairs. Therefore, in the case of source-limited multicast, route control can be performed in the network 120 so that only traffic from the designated multicast transmission server 130 reaches the multicast client terminal 100. The traffic to the same multicast address from the multicast transmission server 131 that is not specified is the same as the multicast transmission server 13 in the case of source-unlimited multicast.
The multicast client terminal 100 is reached in the same manner as from 0. On the other hand, in source-limited multicast, the method of relaying multicast packets from the source server 131 does not exist in the network 120. Therefore, if the source server is different, routing is controlled so that traffic does not reach the request source even if the source server is different. Because it is done.

In order to realize source-limited multicast, the source server is set together with the multicast group address in both the communication between the multicast client terminal 100 and the multicast router 110 and the communication between the multicast router 110 and the adjacent multicast router 122. It is necessary to advertise, but the latter multicast communication protocol PIM-SM (Protocol Inde
pendent Multicast Sparse Mode (specified in IETF RFC2362) can be used to exchange information about the source server. The multicast group management protocol is used for communication between the former terminal and the multicast router. However, as explained in the section of the prior art, it is not necessary to implement the multicast group management protocol that allows all terminals to notify the source server address. I don't mean. Therefore, in order to realize source limited multicast, a multicast group management method between a terminal and a multicast router becomes a problem.

IG used for multicast group management between terminals and multicast routers
In MPv2 and MLDv1, participation request (Join), participation inquiry (Query), withdrawal request (Leave)
These three types of packets are defined, and each is used as described above.
Therefore, these three types of source-unlimited multicast group management packets
It is sufficient if it can be converted into the corresponding packet of source limited multicast. Hereinafter, a method for converting these three types of packets will be described.

Using Fig. 2, source unrestricted multicast join request (Join) and leave request (Le
A method for converting ave) to source-limited multicast will be described. The multicast transmission source management table 220 manages the correspondence of the triple group of the multicast group address column 222, the multicast participation / leave request generation source column 223, and the multicast transmission source server address column 224. In this embodiment, it is assumed that the router administrator has previously filled the contents of the multicast transmission source table 220 with appropriate contents.

Based on FIG. 3, a method by which the multicast group management packet conversion unit 210 of the multicast router 110 converts the source non-limited multicast participation request from the line 116 to the source limited type will be described. When receiving the multicast participation request from the terminal 100 (step 300), the multicast group management packet conversion unit 210 determines whether the request is a source limited multicast participation request or a source non-limited multicast participation request (step 310). In the case of IPv4 IGMP and IPv6 MLD, identification is possible based on the packet length. In the case of the source limited type, the multicast group management packet conversion unit 210 transmits the source limited type multicast participation request as it is to the multicast group management packet processing unit 114 (step 350).
. If the source is not limited to the source, the multicast group management packet conversion unit 210 determines that the source address of the multicast participation request, that is, the set of the address of the terminal 100 and the multicast group address included in the multicast participation request is the multicast group management packet source field 223 and It is checked whether there is an entry in the multicast source management table 220 that matches both of the multicast group address fields 222 (step 330). If there is no entry, it means that the request to join the multicast is rejected by the network administrator, so the multicast group management packet conversion unit 210 ignores the join request (step 340).
. If there is an entry, the multicast group management packet converter 210
Checks the content of the calculated source server. If the content is “don't care”, the multicast group join request is to be processed as a source non-restricted type, and is passed to the multicast group management packet processing unit 114 as it is (step 360). Otherwise, the multicast group management packet processing unit sends a multicast participation request from the source address detected in step 330.
114 (step 370). In exactly the same manner as above, the multicast group management packet conversion 114 of the multicast router 110 converts the source non-limiting multicast leaving request from the line 116 into the source limited type.

Based on FIG. 4, a method in which the multicast group management packet conversion unit 210 of the multicast router 110 converts the source-limited multicast participation inquiry (Query) from the multicast route control unit 112 into a source non-limited type will be described. When a multicast participation inquiry for the line 116 from the multicast route control unit 112 is received via the multicast group management packet processing unit 114 (step 400), the multicast group management packet conversion unit 210 determines whether the inquiry is a source limited multicast participation inquiry. It is determined whether it is a source non-limited multicast participation inquiry (step 410). If the source is not limited, the multicast group management packet conversion processing unit 210 transmits the multicast participation inquiry as it is to the designated line 116 (step 420). In the case of the source limited type, an entry in which the multicast group address field 222 and the multicast group management packet source field 223 respectively match the multicast address included in the inquiry and the address of the line 116 to which the inquiry is sent is the multicast source management table. Whether it is included in 220 is checked (step 430). If there is no corresponding entry, it means that the multicast group has been refused operation by the network administrator, so the multicast group management packet conversion unit 210 does not send a participation inquiry (step 440). If there is an entry, it is checked whether or not the address in the transmission source server column 224 of this entry includes the source address in the source limited multicast participation inquiry (step 450). If not included, it means that the request to join the multicast is rejected by the network administrator, so the multicast participation / exit management unit does not send an inquiry (step 440).
. If it is included, the source address is approved by the network administrator, so the multicast group management packet translation unit 210 sends a non-source limited inquiry to the multicast address included in the inquiry. It may be transmitted to 116 (step 460).

In the present invention, the multicast group management packet processing unit 114 of the multicast router 110 converts the non-source-limited multicast group management packet into the source-limited multicast group management packet. Therefore, in the multicast route control unit 112 of the multicast router 110, it just looks as if a terminal supporting source limited multicast exists on the line 116. Therefore, multicast router 110 and neighboring multicast router 1
There is no need to change the path control between the terminal 22 and the terminal 22 according to the present invention. Therefore, in the present invention, it is necessary to change the terminal 1 in the multicast network 120.
Only the multicast router 110 accommodating 00.

In the present invention, the user cannot select any multicast transmission source server. In that respect, it is not a conversion technique for making source-unlimited multicast terminals completely compatible with source-limited multicast. However, as described in the section of the prior art, source-limited multicast is intended for multicast communications from a few servers such as streaming, and the streaming server is generally operated by a network administrator. There are few practical problems.

It will be described below with reference to FIGS. 5, 6 and 7 that the present invention can be realized in forms other than the embodiment described above.

In the above embodiment, the function of the multicast group management packet processing unit 114 is incorporated in the multicast router 110.
FIG. 5 shows an embodiment in which the function of the multicast group management packet processing unit 114 is removed. In this case, the multicast group management packet conversion apparatus 500 passes the packets other than the multicast group management packet as they are between the terminal 100 and the multicast router 110. When a multicast management packet is input from the line 501 or 502, the multicast group management packet conversion unit 210 converts the packet by the following processing, and then outputs the packet to the line 502 or 501. That is, the multicast join request packet and the leave request packet are converted into a source-limited multicast compatible version by the process of FIG. 3, and the multicast join / leave inquiry packet input from the multicast router 110 is converted into a source non-limited multicast compatible version by the process of FIG. It will function as a protocol converter.

2 and FIG. 5 is based on the premise that the multicast transmission source management table 220 exists in the multicast router 110.
FIG. 6 introduces an embodiment in which the multicast transmission source management table is separated from the multicast router 110. 2 and 5 when the search processing of the table 220 is performed in the processing of FIGS.
In this embodiment, the internal table is drawn, but in FIG. 6, a similar search is realized by making an inquiry from the multicast router 110 to the multicast transmission source management server 600 via the network. Thereby, it is possible to collectively manage the multicast transmission source management table of each multicast router. In this case, each multicast router makes an inquiry to this server to search the multicast transmission source management table 220 described above. It is sufficient to use an existing network database search protocol such as Radius (RFC2865) as the communication protocol used for the inquiry.
FIG. 7 is an overall view of an implementation example in which the multicast transmission source management table is automatically updated by a request from the user. In the embodiment of FIGS. 2, 5, and 6, it is assumed that the multicast source management table 220 is input separately by the network administrator, but multicast source management is realized by implementing the present invention as shown in FIG. The settings in Table 220 can be semi-automated. In general, in the case where paid contents are distributed by multicast, the contract management server 700 needs to manage a contract for using paid contents with the user. The contract ledger 710 managed by the contract management server 700 includes user network information 711 and a contracted session (= a combination of a transmission source server and a multicast group address) 712, and the contents are networked to the multicast transmission source management server 600. By reflecting through the contents, it is also possible to automatically add and delete the contents of the multicast transmission source management table 220 according to a request from the user. As a protocol used for communication from the contract management server 700 to the multicast transmission source management server 600, it is sufficient to use an existing protocol such as HTTPS having a security function that prevents illegal update of the multicast transmission source management table 220. .

The block diagram which shows the whole image of the multicast routing which is the object of this invention. 1 is an overall block diagram of a source-limited multicast routing conversion apparatus using the present invention. 10 is a flowchart illustrating a method of converting a multicast participation participation input / output interface of a multicast router into a multicast group participation request limited to a transmission source server permitted by a network administrator from a source non-restricted multicast group participation request. 10 is a flowchart illustrating a method for converting an inquiry of a terminal participating in a source-limited multicast group into a source-unlimited multicast group participation request by a multicast participation leaving / input interface of the multicast router. It is the whole block diagram of the implementation which implemented the present invention by taking out the multicast participation leaving I / O interface out of the router. It is the whole block diagram of the implementation example which carried out this invention by putting out a multicast transmission source management table out of a router. It is a whole block diagram of the implementation example which updates a multicast transmission source management table automatically by the request from a user.

Explanation of symbols

100 multicast client terminals
110 Multicast router
112 Multicast route controller
114 Multicast group management packet processor
116 Multicast router line
120 network
122 Multicast router
130 Multicast sending server
131 Multicast sending server
210 Multicast group management packet converter
220 Multicast source management table
222 Multicast address field
223 Multicast group management packet source column
224 Multicast source server address field
500 Multicast group management packet converter
600 Multicast source management server
700 Contract management server.

Claims (4)

A packet relay device accommodating a multicast client terminal,
A line that can be connected to a multicast client terminal;
Corresponding information associating a multicast group address , a multicast client terminal address that is a transmission source of the multicast group participation request, and a corresponding multicast transmission source address included in the multicast group participation request from the multicast client terminal A storage unit for storing,
Whether the storage unit stores the correspondence information corresponding to the multicast group address and the multicast client terminal address corresponding to the multicast group address included in the inquiry to join the multicast group and the address of the line to which the inquiry is sent. If the corresponding correspondence information is not stored, the packet relay device that processes the multicast group as being rejected by the network administrator.   Check whether the correspondence information corresponding to the multicast group address and the multicast client terminal address corresponding to the multicast group address included in the inquiry to join the multicast group and the address of the transmission line is stored in the storage unit. If the corresponding correspondence information is stored, it is checked whether the multicast transmission source address in the correspondence information includes the multicast transmission source address in the participation inquiry. If the corresponding address is not included, 2. The packet relay apparatus according to claim 1, wherein a request to join the multicast group from the multicast client terminal is processed as being rejected by the network manager.   It is checked whether or not the multicast source address in the correspondence information includes the multicast source address in the participation inquiry. If included, the source is not limited to the multicast client terminal address included in the participation inquiry. 3. The packet relay apparatus according to claim 2, wherein a type inquiry is performed.   2. The packet relay device according to claim 1, wherein the storage unit is built in the packet relay device, or disposed in a separate device that is connected to the packet relay device via a line and accessible.

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