JP2015159436A - Multicast distribution system, distribution router and multicast distribution method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicast distribution system which achieves switching of a multicast distribution route, where high speed and network load impact are suppressed when a content moves between distribution servers, and to provide a distribution route and a multicast distribution method.SOLUTION: A multicast distribution system 100 holds a separation message received by a representative router (RP) in a Prune information table 155, and when a multicast group received anew matches a multicast group held in the Prune information table 155, transmits the multicast packets (S2, G1) received anew to the router 120(X) transmitted the separation message to the representative router. Upon receiving the multicast packets (S2, G1), the router 120(X) transmits the novel multicast packets (S2, G1) to the routers 120-120belonging to the multicast group G1 and the user terminals 130-130.

Description

  The present invention relates to a multicast distribution system, a distribution router, and a multicast distribution method.

For example, content distribution services represented by continuous data distribution such as audio and video are provided on an IP (Internet Protocol Network) network. For example, in an on-demand content distribution service, a network bandwidth proportional to the number of content users (also referred to as users) is required on the network, and the traffic volume increases.
Multicast is a communication mode in which distribution data transmitted from a distribution server is broadcast to a plurality of host devices, and is also called one-to-many communication. This eliminates the need for the distribution server and the distribution network to duplicately transfer packets for each receiving host, as compared with unicast, which is one-to-one communication, thereby reducing server processing load and network load (bandwidth).

  One of the changes in the environment surrounding the core network NW is an increase in video distribution channels. The increase in video distribution channels includes an increase in distribution channels (traffic) accompanying an increase in video distribution content and a temporary increase in distribution channels due to various events (such as the Olympics).

FIG. 8 is a conceptual diagram of a conventional content distribution system.
As shown in FIG. 8A, the content distribution system 1 includes a distribution server 10 that distributes content in order to provide a content distribution service. The plurality of user terminals 30 and the distribution server 10 are connected to each other by a network including a plurality of routers 20. The user terminal 30 requests content from the distribution server 10 and displays the received content on the display screen as a response to the request. Thereby, the user can view the content. The user terminal 30 periodically notifies the distribution server 10 of the viewed / unviewed state of the acquired content. The distribution server 10 monitors the content viewing status of a plurality of users during unicast distribution.

  In the content distribution system 1, in the case of unicast distribution shown in FIG. 8A, the load on the distribution server 10 increases as the number of users increases. Therefore, the distribution server 10 manages the time information, notifies the user terminal 30 of this time information together with the content, measures the timing at which multicasting is likely, and considers the user's viewing status, The unicast shown in FIG. 8 (a) is dynamically switched to the multicast shown in FIG. 8 (b). In the multicast distribution method, the router 20 copies and transfers the packet. By doing in this way, the content delivery system 1 reduces the load of the delivery server 10 and the core network NW. The content distribution system 1 can cope with not only a broadcast type service but also an on-demand type service.

As a typical multicast delivery method used in the core network NW, there is a PIM (Protocol Independent Multicast) method. There are the following three PIM methods.
In order to realize IP multicast communication, first, it is necessary to determine a distribution route (distribution tree) in the core section of the IP network for an IP packet transmitted from the distribution server into the IP network. Protocols for determining the route include PIM-DM (Protocol Independent Multicast-Dense Mode) (Non-Patent Document 1), PIM-SM (Protocol Independent Multicast-Sparse Mode) (Non-Patent Document 2), PIM-SSM (Protocol Independent Multicast-Source Specific Mode) is used (Non-Patent Document 3).

FIG. 9 is a conceptual diagram of a content distribution system based on the PIM-DM system. The same components as those in FIG. 8 are denoted by the same reference numerals.
As shown in FIG. 9, the content distribution system 1 includes a plurality of distribution servers 11 and 12 as network node devices.
The distribution servers 11 and 12 distribute contents to the plurality of user terminals 30 ₁ to 30 ₄ via the core network NW. Distribution servers 11 and 12 (S1, S2) execute multicast distribution by the PIM-DM system as a system for distributing content. In FIG. 9, two delivery servers 11 and 12 are illustrated as an example, but the number is arbitrary.

The core network NW is, for example, an IP network, and includes a plurality of routers (distribution routers) 20 ₁₁ , 20 ₁₂ , 20 ₂₁ , 20 ₂₂ , 20 _{31 to} 20 ₃₄ . In the following description, the routers 20 ₁₁ , 20 ₁₂ , 20 ₂₁ , 20 ₂₂ , 20 _{31 to} 20 ₃₄ are collectively referred to as the router 20. The number of routers 20 is arbitrary. Routers 20 _{31 to} 20 ₃₄ are examples of end routers. The end router is a router that becomes a final multicast point during multicast distribution.

The user terminals 30 ₁ to 30 ₄ are terminals used by users who view content. The user terminal 30 transmits a content distribution request to the distribution servers 11 and 12 via the core network NW, and is connected to the content request function for acquiring information on the content provider and the content provider. It is a general terminal device provided with a content reception function for receiving content and starting reproduction. The user terminals 30 ₁ to 30 ₄ are configured from, for example, a general personal computer or a portable information terminal.
User terminals 30 ₁ to 30 ₃ (30A) are terminals belonging to multicast group G that are connected to routers 20 _{31 to} 20 ₃₃ (20A) during multicast distribution. The user terminal (30B) is a terminal that does not belong to the multicast group G connected to the router 20 ₃₄ (20B) during multicast distribution. 9, the user terminal 30A is indicated by three user terminals _{30 1,} 30 2, 30 ₃ as an example, the user terminal 30B is shown in the user terminal 30 ₄ of one as an example. The number is arbitrary. Incidentally, referred to as user terminal 30 when not particularly distinguished from each user terminal ₃₀ 1 to 30 _4.

As shown by an arrow a in FIG. 9, in the PIM-DM system, the distribution server 11 (S1) distributes multicast packets to all routers 20 and user terminals 30 once. The router 20 ₃₄ (20B) in which the user terminal 30A of the multicast group G does not exist transmits a Prune message (*, G) to the upper router 20 ₂₂ (see arrow b in FIG. 9) and leaves the core network NW.

FIG. 10 is a conceptual diagram of a content distribution system based on the PIM-SM system. The same components as those in FIG. 8 are denoted by the same reference numerals.
In the PIM-SM system, as indicated by an arrow a in FIG. 10, a router 20 </ b> A in which a user terminal 30 </ b> A of a multicast group G exists (a router that wants to belong to the multicast group G) is sent to an RP (Randezvous Point) (representative router). A Join message (*, G) (participation message) is transmitted. In Figure 10, the router _{20 22} is RP (Designated Router). Incidentally, the distribution server 11, 12 and each router 20 knows in advance the distribution acquiring path information that router _{20 22} is RP (Designated Router).
The distribution server 11 (S1) transmits a multicast packet to the RP as indicated by an arrow b in FIG. For route optimization, the corresponding router _{20 21} transmits the distribution server 11 (S1) to the router _{20 11} connecting Join message (S1, G) (Join message).

FIG. 11 is a conceptual diagram of a content distribution system based on the PIM-SSM system. The same components as those in FIG. 8 are denoted by the same reference numerals.
In the PIM-SSM system, as indicated by an arrow a in FIG. 11, the router 20 </ b> A in which the user terminal 30 </ b> A of the multicast group G exists (the router that wants to belong to the multicast group G) is connected to the distribution server 11 (S <b> 1). A Join message (S1, G) (participation message) is transmitted. The distribution server 11 (S1) is directed to the routers 20 ₁₁ , 20 ₂₁ , 20 ₂₂ , 20 _{31 to} 20 ₃₄ that have transmitted the Join message (S1, G) (participation message), as indicated by an arrow b in FIG. Send a multicast packet.
Since the PIM-SSM system is an extended function of the PIM-SM system, the PIM-SM system and the PIM-SSM system can operate simultaneously. Also, specify one of the protocols in the configuration.

By the way, another popular change in the environment surrounding the core network NW is the spread of virtual servers. When virtual servers are used, physical server resources can be used efficiently.
FIG. 12 is a diagram for explaining a change in traffic exchange accompanying movement of a virtual machine.
With a software called a hypervisor (for example, a VM management control program), a virtual machine VM (Virtual Machine) serving as a plurality of virtual computers is realized on one physical server. Each virtual machine can operate an operating system independently. A virtual machine server, which is a physical server on which a plurality of virtual machines operate, is a computer such as a workstation or a personal computer. In an environment in which a plurality of virtual machine servers are connected via a network, virtual machines realized on the virtual machine server can also communicate via the network.
As shown in FIG. 12, when a virtual machine (virtual server) arranged on the physical server 41 in the station A is moved to the physical server 42 in the station B (in the case of moving between stations), traffic frequently Interchange changes.

A. Adams, J. Nicholas, W. Siadak “Protocol Independent Multicast-Dense Mode (PIM-DM): Protocol Specification (Revised)”. RFC3973 IETF January 2005 B. Fenner, M. Handley, H. Holbrook, I. Kouvelas ”Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification (Revised)”. RFC4601 IETF August 2006 H. Holbrook, B. Cain, “Source-Specific Multicast for IP”. RFC4607 IETF August 2006

  However, in the conventional multicast distribution system, when the movement of video contents of the virtualization server (movement between stations) (see FIG. 12) is supported, the load on the network becomes large, or the distribution route is switched at high speed. The problem that it is not possible occurs.

  13 is a diagram for explaining the problem of the PIM-DM system of FIG. 9, FIG. 14 is a diagram for explaining the problem of the PIM-SM system of FIG. 10, and FIG. 15 is the problem of the PIM-SSM system of FIG. It is a figure explaining.

(1) Problems of the PIM-DM system The PIM-DM system (see FIG. 9) is a system that can be switched at high speed, but is once distributed to all user terminals. For this reason, even when video content movement of the virtualization server is supported, even if video distribution is stopped at the virtualization server S1 and video distribution is started at the virtualization server S2, as shown in FIG. Video content may be distributed from the generalization servers S1 and S2. As the video content moves, extra traffic flows into the core network NW, which places a heavy load on the core network NW.

(2) Issues of the PIM-SM system In the PIM-SM system (see FIG. 10), since the representative router does not transmit a multicast packet to the route that received the leave message, the Join message needs to be received again. Will be sent after re-receiving. For this reason, high-speed switching is impossible. For example, as indicated by a in FIG. 14, the router 20 ₂₂ receives the Prune information (leave message) from the router 20 _21, and therefore transmits a multicast packet in the left direction (direction of the router 20 ₂₁ ) in FIG. 14. do not do. That is, it is impossible to perform high-speed switching of the distribution route in the RP for the route that has received the Prune information (leave message) (re-reception of the Join message is necessary).

(3) Issues of the PIM-SSM system In the PIM-SSM system (see FIG. 11), multicast packets are not distributed unless the participation message from the router and the terminal reaches the content destination router. is there. Deliver after receiving the participation message from the router. If the router and the terminal send a participation message to the content transfer destination router before moving the video content, high-speed switching is possible. However, since participation messages are transmitted all at once, a large load is applied to the router that receives the participation message. For example, as shown by reference numeral a in FIG. 15, for Join message (S2, G) unreceived from the router _{20 12} close to the virtualization server S2, does not transmit the multicast packet. As shown in FIG. 15B, if a Join message (S2, G) is received before moving the image, high-speed switching is possible, but Join is transmitted all at once and the load on the core network NW is affected. Is big. Also, high-speed switching of distribution routes due to the absence of a Join message is not possible. The influence load on the core network NW due to the Join load is large.

  The present invention has been made in view of such a background, and the present invention is capable of realizing a multicast distribution path switching with high speed and reduced network load influence when content moves between distribution servers. It is an object to provide a distribution system, a distribution router, and a multicast distribution method.

  In order to solve the above-described problem, the present invention has PIM-SM or PIM-SSM as a protocol for determining a route from a distribution server to a distribution router, and a multicast group from the distribution server via the distribution router. A multicast distribution system that distributes multicast packets to user terminals belonging to the network, and when the PIM-SM is operating, the distribution router is a representative router that is determined in advance from among the plurality of distribution routers Transfer control means and storage means, the storage means of the designated router holds a leave message for leaving the multicast distribution target, and the transfer control means of the designated router newly received The multicast group described in the multicast packet and stored in the storage means The multicast group described in the leaving message is compared and collated, and the multicast group described in the newly received multicast packet matches the multicast group described in the leaving message held in the storage means. If so, the newly received multicast packet is transmitted to the distribution router that has transmitted the leave message to the designated router, and the distribution router that has received the multicast packet is the user terminal belonging to the multicast group. A multicast packet is transmitted to

  By doing in this way, when the content moves between the distribution servers in the PIM-SM system, it is possible to realize switching of the multicast distribution path at high speed and suppressing the influence of the network load.

  Further, according to the present invention, the distribution server is a plurality of virtualization servers, and the representative router receives the transfer from the distribution router on the source virtualization server side when the content moves between the virtualization servers. The leaving message is retained.

  In this way, even if video content moves between virtualized servers, it is possible to suppress the influence of the load on the network and router and perform high-speed switching of multicast distribution routes.

  Further, the present invention is characterized in that the representative router is an RP (Randezvous Point), and the RP holds Prune information as the leave message.

  In this way, when the distribution server is virtualized, it is possible to realize an extended function of the PIM-SM system that switches the multicast distribution path at high speed.

  Further, according to the present invention, when the content is moved between the plurality of distribution servers during the PIM-SSM operation, the movement-source distribution server sends the current transmission source to the movement-destination distribution server before the movement. A transmission source change message including a new transmission source, a multicast group, and a travel time is transmitted via the distribution router, and the distribution router that has received the transmission source change message includes the distribution router belonging to the multicast group, and The transmission source change message is transmitted to the user terminal, and the distribution router and the user terminal that have transmitted or received the transmission source change message have reached the travel time described in the transmission source change message. Change the distribution server of the transmission source from the current transmission source to the new transmission source, and the first multicast from the new transmission source When the packet is received, the new source and multicast group described in the source change message are compared with the new source and multicast group described in the multicast packet. A route change is performed by transmitting a multicast packet to the distribution router and the user terminal belonging to a group.

  This makes it possible to switch multicast distribution paths at high speed and with less influence on the network load when content moves between distribution servers in the PIM-SSM system.

  Further, according to the present invention, when the distribution server is a plurality of virtualization servers and there is a plan to move content between the virtualization servers, the source virtualization server may The transmission source change message is transmitted to the authentication server via the distribution server.

  In this way, even if video content moves between virtualized servers, it is possible to suppress the influence of the load on the network and router and perform high-speed switching of multicast distribution routes.

  The present invention is also a distribution router of a multicast distribution system that distributes multicast packets from a distribution server to user terminals belonging to a multicast group via a distribution router, and the distribution router includes a plurality of distribution routers. A representative router that has been determined in advance, and has a transfer control means and a storage means, wherein the storage means of the representative router holds a leave message for leaving the multicast distribution target, and the representative router The transfer control means compares the multicast group described in the newly received multicast packet with the multicast group described in the leave message held in the storage means, and describes the newly received multicast packet. Said multicast group When the multicast group described in the leave message held in the storage means matches, the newly received multicast packet is sent to the distribution router that has sent the leave message to the representative router. The distribution router that has received the multicast packet transmits the multicast packet to the user terminal belonging to the multicast group.

  By doing in this way, when the content moves between the distribution servers in the PIM-SM system, it is possible to realize switching of the multicast distribution path at high speed and suppressing the influence of the network load.

  In addition, the present invention provides PIM-SM or PIM-SSM as a protocol for determining a route from a distribution server to a distribution router, from the distribution server to a user terminal belonging to a multicast group via the distribution router. A multicast delivery method for delivering a multicast packet, the step of holding a leave message for leaving from a multicast delivery target at a representative router that is determined in advance among the plurality of delivery routers during the PIM-SM operation; Comparing the multicast group described in the newly received multicast packet with the multicast group described in the leaving message held in the storage means, and the multicast described in the newly received multicast packet glue When the multicast group described in the leaving message held in the storage means matches, the newly received multicast packet is transmitted to the distribution router that has sent the leaving message to the representative router. And a distribution router that has received the multicast packet includes a step of transmitting the multicast packet to the user terminal belonging to the multicast group.

  By doing in this way, when the content moves between the distribution servers in the PIM-SM system, it is possible to realize switching of the multicast distribution path at high speed and suppressing the influence of the network load.

  Further, in the present invention, when the content is moved between the plurality of distribution servers during the PIM-SSM operation, the movement source distribution server, before the movement, the current transmission source, A transmission source change message composed of a new transmission source, a multicast group, and a travel time is transmitted via the distribution router, and the distribution router that has received the transmission source change message has the step of belonging to the multicast group The step of transmitting the transmission source change message to the distribution router and the user terminal, and the distribution router and the user terminal that have transmitted or received the transmission source change message are transmitted at the travel time described in the transmission source change message. At the point of time, the process of changing the distribution server of the transmission source from the current transmission source to the new transmission source, A step of comparing and collating the new source and multicast group described in the source change message with the new source and multicast group described in the multicast packet when the first multicast packet from the source is received And a step of changing a route by transmitting a multicast packet to the distribution router and the user terminal belonging to the multicast group when they match.

  This makes it possible to switch multicast distribution paths at high speed and with less influence on the network load when content moves between distribution servers in the PIM-SSM system.

  According to the present invention, it is possible to provide a multicast distribution system, a distribution router, and a multicast distribution method capable of realizing switching of a multicast distribution route at a high speed and suppressing the influence of a network load when content moves between distribution servers. Can do.

It is a block diagram which shows the multicast delivery system which concerns on the 1st Embodiment of this invention. It is a figure which shows the multicast delivery system which implement | achieves the extended function of the PIM-SM system of the multicast delivery system which concerns on the 1st Embodiment of this invention. It is a functional block diagram of a representative router of the multicast distribution system according to the first embodiment of the present invention. It is a data structural example of the Prune information table of the multicast delivery system which concerns on the 1st Embodiment of this invention. It is a figure which shows the multicast delivery system which concerns on the 2nd Embodiment of this invention. It is a functional block diagram of the router of the multicast delivery system which concerns on the 2nd Embodiment of this invention. It is a data structural example of the transmission source change information table of the router of the multicast delivery system which concerns on the 2nd Embodiment of this invention. It is a conceptual diagram of the conventional content delivery system. It is a conceptual diagram of the content delivery system by a PIM-DM system. It is a conceptual diagram of the content delivery system by a PIM-SM system. It is a conceptual diagram of the content delivery system by a PIM-SSM system. It is a figure explaining the change of the traffic alternating current accompanying a virtual machine movement. It is a figure explaining the subject of the PIM-DM system of FIG. It is a figure explaining the subject of the PIM-SM system of FIG. It is a figure explaining the subject of the PIM-SSM system of FIG.

A multicast distribution system and the like in a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a configuration diagram showing a multicast distribution system according to the first embodiment of the present invention. This embodiment is an example of realizing an extended function of the PIM-SM system that switches a multicast distribution route at high speed when a distribution server is virtualized.
As shown in FIG. 1, the multicast distribution system 100 receives distribution servers 111 and 112 serving as distribution sources of a multi-channel multicast stream (hereinafter also abbreviated as “stream”) such as video data of television broadcasting, and the stream. A number of user terminals 130 _{1 to} 130 ₄ and a plurality of routers (distribution routers) 120 that perform relay distribution of streams between the distribution servers 111 and 112 to the user terminals 130 _{1 to} 130 ₄ are connected. User terminals 130 _{1 to} 130 ₄ and distribution servers 111 and 112 are connected to each other by a core network NW including a plurality of routers 120.
Each device of the multicast distribution system 100 is configured as a computer having a CPU (Central Processing Unit), a memory, a hard disk (storage means), and a network interface, and the computer executes a program read on the memory. Thus, each processing unit is operated.

<Distribution server>
The distribution server 111 includes a virtual machine disposed on the physical server of the station A, and the distribution server 112 includes a virtual machine disposed on the physical server of the station B.
The distribution server 111 and 112, most recently router ₁₂₀ 11, _{120 12} are connected to the router ₁₂₀ 11, _{120 12,} connected to the router ₁₂₀ 21, _{120 22} through a communication path 141, the router ₁₂₀ 21, _{120 22} Are further connected to a plurality of user terminals 130 _{1 to} 130 ₄ via routers 120 _{31 to} 120 ₃₄ .

The distribution servers 111 and 112 are servers that are flow distribution sources. As flow identification information, SSM (Source Specific Multicast), which is a (S, G) designation type, that uses a combination of the flow group and the delivery server address of the flow transmission source as identification information, specifies only the flow group. ASM (Any Source Multicast) which is a (*, G) designation type used as information. In this embodiment, the flow specific information will be described as an (S, G) designation type. Here, (S, G) is an abbreviation for (Source, Group), where the first Source indicates the address of the distribution server 111, 112 as the transmission source, and the next Group indicates the group of the flow.
The distribution servers 111 and 112 distribute the multicast stream to the plurality of user terminals 130 _{1 to} 130 ₄ via the core network NW. The distribution server 111 is a video distribution server virtualized in the station A, and the distribution server 112 is a video distribution server virtualized in the station B.

  In the present embodiment, when the distribution servers 111 and 112 are virtualized, when the video content is moved (in FIG. 1, when the distribution server 112 virtualized from the distribution server 111 virtualized the video D is moved) (several hundred ms). The PIM-SM extended function for switching the multicast distribution route is realized. In FIG. 1, two distribution servers 111 and 112 are illustrated as an example, but the number is arbitrary.

<Core network NW>
The core network NW constitutes a multicast distribution network, for example, the Internet network. The core network NW includes a PIM-DM system, a PIM-SM system, and a PIM as protocols for determining routes from the distribution servers 111 and 112 to the routers 120 ₁₁ , 120 ₁₂ , 120 ₂₁ , 120 ₂₂ , 120 _{31 to} 120 ₃₄ . -The SSM method is generally used.

<Router>
The core network NW includes a plurality of routers 120 ₁₁ , 120 ₁₂ , 120 ₂₁ , 120 ₂₂ , 120 _{31 to} 120 ₃₄ . In the following description, the routers 120 ₁₁ , 120 ₁₂ , 120 ₂₁ , 120 ₂₂ , 120 _{31 to} 120 ₃₄ are collectively referred to as the router 120. The number of routers 120 is arbitrary. Routers 120 _{31 to} 120 ₃₄ are examples of end routers. The end router is a router that becomes a final multicast point during multicast distribution. Details of the router 120 will be described later with reference to FIG.

<User terminal>
User terminals 130 _{1 to} 130 ₄ are terminals used by users who view content. The user terminal 130 transmits a content distribution request to the distribution servers 111 and 112 via the core network NW, and is connected to a content request function for acquiring information on a content provider and a content provider. It is a general terminal device provided with a content reception function for receiving content and starting reproduction. The user terminals 130 _{1 to} 130 ₄ are composed of, for example, a general personal computer or a portable information terminal.

User terminals 130 _{1 to} 130 ₃ (130A) are terminals belonging to multicast group G1 that are connected to routers 120 _{31 to} 120 ₃₃ (120A) during multicast distribution. The user terminal 130 ₄ (130B) is a terminal that does not belong to the multicast group G1 connected to the router 120 ₃₄ (120B) during multicast distribution. In FIG. 1, the user terminal 130 </ _b > A is illustrated as three user terminals 130 ₁ , 130 ₂ , and 130 ₃ as an example, and the user terminal 30 </ _b > B is illustrated as one user terminal 130 ₄ as an example. The number is arbitrary. Incidentally, it referred to as user terminal 130 when not particularly distinguished from each user terminal ₁₃₀ 1 to 130 _4.

FIG. 2 is a diagram showing a multicast distribution system that realizes an extended function of the PIM-SM system. The same components as those in FIG. 1 are denoted by the same reference numerals.
The multicast distribution system 100 receives the IP multicast packets distributed from the distribution servers 111 and 112, the plurality of routers 120 that relay the packets of the distribution servers 111 and 112, and the distribution servers 111 and 112. When the video D moves between the distribution servers 111 and 112 in a network configured with user terminals 130 including the multicast group G1 to perform, the multicast distribution route is switched at high speed.

As shown in FIG. 2, the distribution server 112 (S2) router _{120 22} connected to the nearest router _{120 12} is assumed to be RP (Designated Router). The representative router is an arbitrary router selected from a plurality of routers. Here, the distribution server 112 (S2) router _{120 22} closer to the nearest router _{120 12} is determined to RP (Designated Router). Note that the router _{120 22} is an RP, it distribution server 111 and 112 (S1, S2) and the router 120 knows in advance the distribution acquiring path information. A detailed description of FIG. 2 will be given later.

Figure 3 is a functional block diagram of a router _{120 22} is RP (Designated Router).
As illustrated in FIG. 3, the router 120 ₂₂ includes a distribution path control unit 151, a stream transmission / reception unit 152, a network interface unit 153, and a storage unit 154. The router 120 ₂₂ is configured by a computer having a communication function, and these are realized by a CPU (not shown) included in the router 120 ₂₂ executing a predetermined program.

The distribution route control unit 151 controls the distribution route of the stream.
The distribution route control unit 151 receives the Prune information and holds the received Prune information in the Prune information table 155.
The distribution route control unit 151 matches the multicast group described in the newly received multicast packet with the multicast group described in the Prun information (leave message) held in the Prun information table 155 of the storage unit 154 (comparison verification) )
When the multicast group described in the newly received multicast packet matches the multicast group described in the Prun information (leave message) held in the Prun information table 155, the distribution path control unit 151 displays the Prun information in the RP. The newly received multicast packet is transmitted to the router that has transmitted the (leave message).

The stream transmission / reception unit 152 performs stream relaying and distribution between communication ports included in the network interface unit 153 in accordance with instructions from the distribution path control unit 151.
The network interface unit 153 includes communication ports for connection with the upper router, connection with the user terminal 130, and connection with other lower routers in the group.
The storage unit 154 includes a semiconductor memory, a magnetic disk device, and the like, and includes a prune information table 155 that holds prune information (leave message).

<Prune information table>
FIG. 4 is a data configuration example of the Prune information table 155. As shown in FIG. 4, the Prune information table 155 holds a Prune transmission source, a video transmission source, and a multicast group as Prune information. In FIG. 4, the Prune transmission source is “X” indicating the router 120 ₂₁ that is the Prune transmission source when viewed from the RP. The video transmission source is a video transmission source when viewed from the RP, but here, it is assumed that the wild card is “*” as an unclear case. The multicast group is “G1” here. Since the Prune information is held in the Prune information table 155, if the Prune transmission source “X” is designated, the video transmission source “*” and the multicast group “G1” can be referred to. If “G1” is designated, the video transmission source “*” and the Prune transmission source “X” can be referred to as the reverse lookup function.

Hereinafter, a multicast distribution method of the multicast distribution system configured as described above will be described.
As illustrated in FIG. 2, the RP (representative router) is the router 120 ₂₂ , and the router X that transmits the prune information (leave message) to the RP is the router 120 ₂₁ .
<Before moving video content, etc. between virtualization servers>
The distribution server 111 (S1) transmits the multicast packet (S1, G1) to the router 120 ₂₂ (RP) as indicated by an arrow a in FIG. For route optimization, the router _{120 21,} as shown by the arrow b in FIG. 2, and transmits the to the router _{120 11} connecting the distribution server 111 (S1) Join message (S1, G1) (Join message).

<After moving video content, etc. between virtualization servers>
<Procedure 1>
When the distribution server 111 (S1) is stopped due to the movement of the video D between the distribution servers 111 and 112, as indicated by a symbol c (x mark) in FIG. 2, as indicated by an arrow d in FIG. The router 120 ₂₁ transmits Prune information (leave message) (S1, G1) to the router 120 ₂₂ (RP) with itself as a Prune source “X”. Note that the Prune information (leave message) is transmitted only once from the Prune transmission source “X” to the router 120 ₂₂ (RP).
The router 120 ₂₂ (RP), as indicated by the symbol e in FIG. 2, stores the Prun information (leave message) (S1, G1) received from the router 120 ₁₂ (Router X) in the Prun information table 155 (see FIG. 4). Hold. Here, the Prune information table 155 holds the Prune transmission source “X”, the video transmission source “*”, and the multicast group “G1”.

<Procedure 2>
The router 120 ₂₂ (RP) newly receives multicast packet information (S2, G1) from the distribution server 112 (S2) as indicated by an arrow f in FIG. The router 120 ₂₂ (RP) matches the newly received multicast packet information (S2, G1) with the Prun information (leave message) held in the Prun information table 155, as indicated by the symbol g in FIG. . Specifically, the router 120 ₂₂ (RP) refers to the Prune information table 155, and the multicast group (here, “G1”) of the newly received multicast packet information (S 2, G 1) and the Prune information table 155 The multicast information (here, “G1”) of the Prun information (leave message) is compared and collated.

<Procedure 3>
As shown by the arrow h in FIG. 2, the router 120 ₂₂ (RP) is configured to execute the prune information (leave message) in the prune information table 155 held by the multicast group of the newly received multicast packet information (S2, G1). The multicast packet (S2, G1) is transmitted to the router 120 ₂₁ (X) that transmitted the Prune information (leave message).

In the example of FIG. 4, the router 120 ₂₂ (RP) has a multicast group (here, “G1”) in the Prune information table 155 and a multicast group (here, “G1”) of the newly received multicast packet information (S2, G1). ")" Is determined to be the same, and the Prune information table 155 is reversely referred to the Prune transmission source direction from the multicast packet group to identify the Prune transmission source ("X" in this case). Then, as shown by the arrow h in FIG. 2, the router 120 ₂₂ (RP) transmits the new multicast packet information (S2, G1) to the router 120 ₂₁ (X) that is the specified Prune transmission source. . When the multicast group in the Prune information table 155 does not match the multicast group of the newly received multicast packet information, the router 120 ₂₂ (RP) does nothing. In this case, the router 120 ₂₂ (RP) performs the same process, that is, the process of “sending the multicast packet after changing the transmission source to the router that holds the leave message and transmits the leave message”.

<Procedure 4>
The router 120 ₂₁ (X) that has received the multicast packet (S2, G1), as indicated by an arrow i in FIG. 2, has routers 120 _{31 to} 120 ₃₃ belonging to the corresponding multicast group (“G1”) and user terminals. The multicast packet information (S2, G1) is transmitted to 130 _{1 to} 130 ₃ (130A).

<Procedure 5>
The router 120 ₂₁ (X) transmits a Join message (S2, G1) (participation message) to the router 120 ₂₂ (RP) as indicated by an arrow j in FIG.

As described above, in the multicast distribution system 100, the RP (representative router) is described in the storage unit 154 that holds the received prune information (leave message) in the prune information table 155 and the newly received multicast packet. A distribution route control unit 151 that matches the multicast group and the multicast group described in the Prune information (leave message) held in the Prune information table 155, and the distribution route control unit 151 adds a newly received multicast packet to the received multicast packet. When the described multicast group matches the multicast group described in the Prun information (leave message) held in the Prun information table 155, the rule that sent the Prun information (leave message) to the RP For other ₁₂₀ 21 (X), and transmits the newly received multicast packet (S2, G1). The router 120 ₂₁ (X) that has received the multicast packet (S2, G1) transmits a new multicast packet (S2, G1) to 120 _{31 to} 120 ₃₃ and user terminals 130 _{1 to} 130 ₃ belonging to the multicast group G1. .

  In this way, the present multicast distribution method extends the PIM-SM method, holds the PruPrune information (leave message) by the RP, and transmits a new multicast packet to the router that has transmitted the Prun information (leave message).

As a result, when the video content moves between the distribution servers 111 and 112 (S1, S2) in the PIM-SM system, it is possible to switch the multicast distribution route with high speed and reduced NW load influence.
In particular, even if video content moves between virtualized servers, it is possible to suppress the influence of the load on the network or router and to perform high-speed (within several hundred ms) switching of multicast distribution paths.

(Second Embodiment)
FIG. 5 is a diagram showing a multicast distribution system according to the second embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals.
In the present embodiment, when the distribution servers 211 and 212 are virtualized, when the video content is moved (in FIG. 1, when the distribution server 112 virtualized from the distribution server 211 virtualized the video D is moved) (several hundred ms). The PIM-SSM extended function for switching the multicast distribution route is realized.

As shown in FIG. 5, the multicast distribution system 200 includes distribution servers 211 and 212 serving as distribution sources of a multi-channel multicast stream such as video data of television broadcasting, and a large number of user terminals 130 _{1 to} 130 ₄ that receive the stream. A plurality of routers 220 that perform relay distribution of streams between the distribution servers 211 and 212 and the user terminals 130 _{1 to} 130 ₄ are connected. User terminals 130 _{1 to} 130 ₄ and distribution servers 211 and 212 are connected to each other by a core network NW including a plurality of routers 220.

<Distribution server>
The distribution server 211 includes a virtual machine disposed on the physical server of the station A, and the distribution server 212 includes a virtual machine disposed on the physical server of the station B.
The distribution server 211 and 212, the most recent server-side router ₂₂₀ 11, _{220 12} are connected to the router ₂₂₀ 11, _{220 12,} connected to the router ₂₂₀ 21, _{220 22} through a communication path 141, the router _{220 21} , 220 ₂₂ are further connected to a plurality of user terminals 130 _{1 to} 130 ₄ via routers 220 _{31 to} 220 ₃₄ .
The distribution servers 211 and 212 distribute the multicast stream to the plurality of user terminals 130 _{1 to} 130 ₄ via the core network NW. The distribution server 211 is a video distribution server virtualized in the station A, and the distribution server 212 is a video distribution server virtualized in the station B. In FIG. 5, two distribution servers 211 and 212 are illustrated as an example, but the number is arbitrary.
The distribution servers 211 and 212 transmit a PIM message (Change) (transmission source change message) notifying that the transmission source is to be changed at the time of.

<Router>
FIG. 6 is a functional block diagram of the router 220 ₂₁ . Since the hardware configuration of the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₄ shown in FIG. 5 is substantially the same, the router 220 ₂₁ will be described as a representative.
As illustrated in FIG. 6, the router 220 ₂₁ includes a distribution path control unit 251, a stream transmission / reception unit 152, a network interface unit 153, and a storage unit 254. The configuration of the stream transmission / reception unit 152 and the network interface unit 153 is the same as that of the stream transmission / reception unit 152 and the network interface unit 153 in FIG.
The delivery route control unit 251 controls the delivery route of the stream.
When the delivery path control unit 251 receives the PIM message (Change), the delivery path control unit 251 transmits the PIM message (Change) to the routers 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) belonging to the multicast group G1.
The distribution route control unit 251 changes the transmission server of the transmission source from the current transmission source to the new transmission source when the movement time described in the PIM message (Change) is reached.
When receiving the first multicast packet from the new transmission source, the distribution path control unit 251 receives the new transmission source and multicast group described in the PIM message (Change) and the new transmission source and multicast described in the multicast packet. When the groups are compared and collated, the route is changed by transmitting a multicast packet to the routers 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) belonging to the multicast group G1.
The storage unit 254 includes a semiconductor memory, a magnetic disk device, and the like, and includes a transmission source change information table 250 that holds a PIM message (Change) transmitted from the distribution server of the movement source before movement.

The routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₄ are all assumed to be synchronized in time. Therefore, the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₄ can simultaneously change the route at the same preset time.

In the following description, the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₄ are collectively referred to as the router 220. The number of routers 220 is arbitrary. Routers 220 _{31 to} 220 ₃₄ are examples of end routers. The end router is a router that becomes a final multicast point during multicast distribution.

<Sender change information table>
FIG. 7 is a data configuration example of the transmission source change information table 250 of the routers 220 ₂₁ and 220 ₂₂ . As shown in FIG. 7, the transmission source change information table 250 holds message type, current transmission source, new transmission source, multicast group, and movement time as transmission source change information. This message type is a message to change the transmission source.
The transmission source change information held in the transmission source change information table 250 is a PIM message (Change) that tells the distribution server 211 to the router 220 ₂₁ to change the transmission source at the time of. The PIM message (Change) is not in the conventional PIM-SSM system, but is first introduced by the present inventor in this embodiment.

Hereinafter, a multicast distribution method of the multicast distribution system configured as described above will be described.
A router 220 ₂₁ shown in FIG. 5 is a router connected to the nearest router 220 ₁₁ of the distribution server 211, and a router 220 ₂₂ shown in FIG. 5 is a router connected to the nearest router 220 ₁₂ of the delivery server 212. is there. Information is transmitted and received between the distribution server 211 (S 1) and the distribution server 212 (S 2) through a route to the router 220 ₁₁ , the router 220 ₂₁ , the router 220 ₂₂ , and the router 220 ₁₂ .

In the following description, the router 220 ₂₁ shown in FIG. 5 receives the PIM message (Change) from the distribution server of the movement source before moving, and the router 220 ₂₂ receives the PIM message (from the router 220 ₂₁ ). It is assumed that the router receives (Change) and relays it to each router.

<Procedure 1>
When the distribution server 211 (S1) is to be stopped with the movement of the video D between the distribution servers 211 and 212, as shown by the symbol a (x) in FIG. 5, the distribution server 211 (S1) Prior to the stop, the PIM message (Change) is transmitted to the moving destination of the video content (that is, the distribution server 212 (S2)). The PIM message (Change) is transmission source change information that informs that the transmission source is changed at the time of.

Since the distribution server 211 (S1) knows that it will move to the distribution server 212 (S2) at “movement time” ○ hour Δmin, the PIM is sent to the distribution server 212 (S2) at an appropriate timing before the movement. A message (Change) is transmitted.
Transmission of the PIM message (Change) from the distribution server 211 (S1) to the destination (distribution server 212 (S2)) is performed by the distribution server 211 (S1), as indicated by an arrow b in FIG. (see FIG. 7), first sent to the router _{220 11,} as shown by the arrow c in FIG. 5, the router _{220 11} transmits to the router _{220 21.} Then, the router _{220 21,} as shown by the arrow d in FIG. 5, and sends the source modification information received from the router _{220 11} (see FIG. 7) to the router _{220 22,} router _{220 22} arrow e in FIG. 5 as shown in f, through the router _{220 12} transmits to distribution server 212 (S2).

  As a result, the distribution server 211 (S1) transmits a PIM message (Change) to the distribution server 212 (S2), which is the moving destination of the video content, in advance before stopping itself.

<Procedure 2>
The routers 220 ₂₁ and 220 ₂₂ that have received the PIM message (Change), as indicated by an arrow g in FIG. 5, have the lower routers 220 _{31 to} 220 ₃₃ belonging to the corresponding multicast group (here, “G1”) and The PIM message (Change) is copied and transmitted to the user terminals 130 _{1 to} 130 ₃ .

<Procedure 3>
As shown by the arrow h in FIG. 5, all routers and user terminals that have received the PIM message (Change) transmit when the “movement time” indicated by the PIM message (Change) is reached. The source is changed from “current sender” to “new sender”. In this case, the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) that have received the PIM message (Change) have the transmission source as the distribution server 211 (S1). ) To the distribution server 212 (S2).
Each router is similar to the operation of the conventional PIM-SSM system unless it receives a PIM message (Change) from the upper router.

<Procedure 4>
When the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) that have received the PIM message (Change) receive multicast packets after changing the distribution destination Confirm the transmission source and multicast group, and transmit to the corresponding router and user terminal.
Specifically, the routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) that received the PIM message (Change) are the first from the new transmission source. When a new multicast packet and a multicast group described in the PIM message (Change) are compared with the new transmission source and the multicast group described in the multicast packet, and A route is changed by transmitting a multicast packet to a lower router toward a user terminal belonging to the multicast group.

In the case of FIG. 5, as indicated by the arrow i in FIG. 5, the router that originally does not hold the path information (S1, G1) sends the packet (S2, G1) to the router that has received the PIM message (Change). Send. That is, it is the same as the transmission of Join (S2, G1).
Further, as indicated by an arrow j in FIG. 5, the router originally holding the path information (S1, G1) transmits the packet (S2, G1) to the distribution destination of the original packet (S1, G1). .
That is, the routers 220 ₁₁ and 220 ₁₂ that have received the PIM message (Change) transmit the PIM message (Change) to the routers 220 _{31 to} 220 ₃₃ that originally distributed the video.

  As described above, the multicast distribution system 200 does not start the route change triggered by the movement between the distribution servers 211 (S1) and 212 (S2), but moves between the distribution servers 211 (S1) and 212 (S2). Prior to this, a PIM message (Change) is transmitted to the corresponding router and user terminal so that the corresponding router and user terminal are switched to the distribution server 212 (S2) side, and preparations for rewriting to the new transmission source are made. deep. Then, when the “movement time” ○ hour Δmin is reached, the corresponding router and user terminal switch to multicast packet reception from the distribution server 212 (S2) as the new transmission source. Therefore, when the “movement time” ○ hour Δmin is reached, all of the corresponding routers and user terminals are switched to multicast packet reception from the distribution server 212 (S2).

As described above, the multicast distribution system 200 is configured so that the distribution server 211 (S1) at the movement source sends the current transmission source, the new transmission source, the multicast group, and the distribution group to the distribution server 212 (S2) at the movement destination before movement. A PIM message (Change) including the movement time is transmitted via the routers 220 ₁₁ , 220 ₂₁ , 220 ₂₂ , and 220 ₁₂ .
The routers 220 ₁₁ and 220 ₁₂ that have received the PIM message (Change) transmit the PIM message (Change) to the routers 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) belonging to the multicast group G1. The routers 220 ₁₁ , 220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₃ and user terminals 130 _{1 to} 130 ₃ (130A) that have transmitted or received the PIM message (Change) are described in the PIM message (Change). When the movement time comes, the transmission server of the transmission source is changed from the current transmission source to the new transmission source. When the first multicast packet from the new source is received, the new source and multicast group described in the PIM message (Change) are compared with the new source and multicast group described in the multicast packet. If they match, the route is changed by transmitting a multicast packet to the routers 220 _{31 to} 220 ₃₃ and the user terminals 130 _{1 to} 130 ₃ (130A) belonging to the multicast group G1.

Thereby, for the PIM-SSM system, when the video content moves between the distribution servers 211 and 212 (S1, S2), it is possible to switch the multicast distribution route with high speed and suppressing the influence of the NW load.
In particular, even if video content moves between virtualized servers, it is possible to suppress the influence of the load on the network or router and to perform high-speed (within several hundred ms) switching of multicast distribution paths.

In addition, among the processes described in the above embodiments, all or part of the processes described as being automatically performed can be manually performed, or the processes described as being manually performed All or a part of the above can be automatically performed by a known method. In addition, the processing procedures, control procedures, specific names, and information including various data and parameters shown in the above-described document and drawings can be arbitrarily changed unless otherwise specified.
Further, each component of each illustrated apparatus is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or a part of the distribution / integration may be functionally or physically distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Further, each of the above-described configurations, functions, and the like may be realized by software for interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function is stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), an IC (Integrated Circuit) card, an SD (Secure Digital) card, an optical disk, etc. It can be held on a recording medium. Further, in this specification, the processing steps describing time-series processing are not limited to processing performed in time series according to the described order, but are not necessarily performed in time series, either in parallel or individually. The processing (for example, parallel processing or object processing) is also included.

100, 200 multicast distribution system 111, 112, 211, 212 distribution server 120 ₁₁ , 120 ₁₂ , 120 ₂₁ , 120 ₂₂ , 120 _{31 to} 120 ₃₄ , 220 ₁₁ ,
220 ₁₂ , 220 ₂₁ , 220 ₂₂ , 220 _{31 to} 220 ₃₄ router (distribution router)
130 _{1 to} 130 ₄ User terminals 151 251 Distribution route control unit (transfer control means)
152 Stream transmission / reception unit 153 Network interface unit 154, 254 Storage unit (storage unit)
155 Prune information table 250 Source change information table NW Core network RP Representative router

Claims (8)

Multicast that has PIM-SM or PIM-SSM as a protocol for determining a route from a distribution server to a distribution router, and distributes multicast packets from the distribution server to user terminals belonging to a multicast group via the distribution router A distribution system,
During the PIM-SM operation,
The distribution router has a transfer control means and a storage means when the distribution router is a representative router determined in advance from among the plurality of distribution routers,
The storage means of the designated router holds a leave message for leaving the multicast distribution target,
The transfer control means of the representative router is:
A comparison is made between the multicast group described in the newly received multicast packet and the multicast group described in the leaving message held in the storage means,
When the multicast group described in the newly received multicast packet matches the multicast group described in the leave message held in the storage means,
Send the newly received multicast packet to the distribution router that has sent the leave message to the designated router,
The distribution router that has received the multicast packet
A multicast distribution system, wherein a multicast packet is transmitted to the user terminals belonging to the multicast group. The distribution server is a plurality of virtualization servers,
2. The multicast according to claim 1, wherein the representative router holds the leaving message received from the distribution router on the source virtualization server side when the content moves between the virtualization servers. 3. Distribution system. The multicast distribution system according to claim 1 or 2, wherein the representative router is an RP (Randezvous Point), and the RP holds Prune information as the leave message. During the PIM-SSM operation,
When moving content between a plurality of the distribution servers,
Before the move, the distribution server of the movement source
A transmission source change message including a current transmission source, a new transmission source, a multicast group, and a movement time is transmitted to the movement destination distribution server via the distribution router,
The distribution router that has received the source change message
Sending the source change message to the distribution router and the user terminal belonging to the multicast group;
The distribution router and the user terminal that have transmitted or received the transmission source change message,
When the travel time described in the transmission source change message is reached, the transmission server of the transmission source is changed from the current transmission source to the new transmission source,
When the first multicast packet from the new source is received, the new source and multicast group described in the source change message are compared with the new source and multicast group described in the multicast packet. The multicast distribution system according to claim 1, wherein, when they match, a route change is performed by transmitting a multicast packet to the distribution router and the user terminal belonging to the multicast group. The distribution server is a plurality of virtualization servers,
When there is a plan to move content between the virtualization servers, the source virtualization server sends the source change message to the destination virtualization server via the distribution server before the migration. The multicast distribution system according to claim 4, wherein transmission is performed. A distribution router of a multicast distribution system that distributes multicast packets from a distribution server to user terminals belonging to a multicast group via a distribution router,
The distribution router has a transfer control means and a storage means when the distribution router is a representative router determined in advance from among the plurality of distribution routers,
The storage means of the designated router holds a leave message for leaving the multicast distribution target,
The transfer control means of the representative router is:
A comparison is made between the multicast group described in the newly received multicast packet and the multicast group described in the leaving message held in the storage means,
When the multicast group described in the newly received multicast packet matches the multicast group described in the leave message held in the storage means,
Send the newly received multicast packet to the distribution router that has sent the leave message to the designated router,
The distribution router that has received the multicast packet
A distribution router for transmitting a multicast packet to the user terminal belonging to the multicast group. Multicast that has PIM-SM or PIM-SSM as a protocol for determining a route from a distribution server to a distribution router, and distributes multicast packets from the distribution server to user terminals belonging to a multicast group via the distribution router A delivery method,
At the time of the PIM-SM operation, in the representative router that is determined in advance from among the plurality of distribution routers,
Holding a leave message for leaving the multicast distribution target;
Comparing the multicast group described in the newly received multicast packet with the multicast group described in the leaving message held in the storage means;
The distribution router that has transmitted the leave message to the designated router when the multicast group described in the newly received multicast packet matches the multicast group described in the leave message held in the storage means A step of transmitting the newly received multicast packet;
In the distribution router that has received the multicast packet,
A multicast distribution method comprising a step of transmitting a multicast packet to the user terminal belonging to the multicast group. When moving content between the plurality of distribution servers during the PIM-SSM operation,
In the distribution server of the movement source, before the movement,
A transmission source change message composed of a current transmission source, a new transmission source, a multicast group, and a movement time, is transmitted to the distribution server of the movement destination via the distribution router;
In the distribution router that has received the source change message,
Transmitting the source change message to the distribution router and the user terminal belonging to the multicast group;
The distribution router and the user terminal that have transmitted or received the transmission source change message,
Changing the distribution server of the transmission source from the current transmission source to the new transmission source when the travel time described in the transmission source change message is reached;
When the first multicast packet from the new source is received, the new source and multicast group described in the source change message are compared with the new source and multicast group described in the multicast packet. Process,
The multicast distribution method according to claim 7, further comprising a step of changing a route by transmitting a multicast packet to the distribution router and the user terminal belonging to the multicast group when they match.

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