TWI607639B - SDN sharing tree multicast streaming system and method - Google Patents

Description

SDN shared tree group broadcast stream system and method

The invention belongs to one application to SDN (Software Defined) Networking, software-defined network) shared tree multicast streaming system and method. The multicast source establishes a multicast tree before sending the multicast stream as a path for transmitting the multicast stream, and thereby reducing the network. The waste of the road bandwidth. The method proposed by the present invention can reduce the amount of calculation required by the controller and reduce the number of flow bars required for the switch.

SDN is an emerging network architecture in recent years. Its concept is to separate the control-plane function of the network from the data-plane function, and to concentrate the control layer on the controller. The switch only retains the function of transmitting packets, and the switch needs to pass through. The controller calculates the path and the controller sets the direction of packet transmission to the switch. Therefore, the controller has comprehensive network topology information to establish an optimal multicast tree, and can process multicast messages more quickly, so that IP streaming multicast can be implemented on SDN.

Before the controller transmits the stream on the source side of the multicast network, the multicast source must be established for the source end of the multicast broadcast, so that the source end of the multicast broadcast can be transmitted to the user end. The invention designs a shared tree multicast streaming system for SDN networks. Previously applied to multicast streaming is mainly for how the switch sets the traffic bar so that the packet can be transmitted to the client, and does not consider the number of traffic bars caused by the number of multicast sources. The impact, which in turn affects the performance of the switch, does not apply to a large number of multicast source sources. A similar concept is mentioned in the following prior patents: US 8831000 (IP multicast service join process for MPLS-based virtual private cloud networking), US 8638789 (Optimal multicast forwarding in OpenFlow based networks). On the other hand, the mechanism for tree establishment is to establish a multicast tree for each multicast source, which will make the controller calculate the multicast tree for too long, and make the number of traffic bars in the switch too much. Not applicable to a large number of multicast sources.

In view of the shortcomings derived from the above-mentioned conventional methods, the inventor of the present invention has improved and innovated, and after years of painstaking research, finally successfully developed and completed the SDN shared tree group streaming system and method.

To achieve the above objective, the present invention is to design a shared tree multicast streaming system and method for an SDN network, and the multicast source side divides the adjacent multicast source trees into the same cluster before transmitting the multicast stream. As the network topology is distributed, a plurality of clusters can be automatically formed, and then a multicast tree is established for each cluster as a path for transmitting the multicast stream. By sharing the tree and setting the flow bar of the shared tree, the amount of calculation required by the controller is reduced and the number of flow bars required by the switch is reduced. If too many multicast trees are established (such as establishing a multicast tree for each multicast source), the controller will calculate the multicast tree for too long and make the number of traffic bars in the switch too much; if too few groups are established Broadcasting trees (such as building only one multicast tree for all multicast sources) will make the path of the transmission too long and overload the concentration point.

The SDN shared tree multicast stream system for achieving the above object is to bring the adjacent multicast source before the controller transmits the stream at the source end of the multicast. It is divided into a plurality of clusters. With the network topology distribution, a plurality of clusters can be automatically formed. For each cluster, a switch with the smallest distance from the source end of the cluster is set as a concentration point, so that the multicast source in the same cluster is used. The end establishes the shortest path to the centralized point, and takes the centralized point as the root, establishes the shortest path tree to all the multicast clients, and sets a traffic bar for each switch on the tree node according to the shortest path tree. If too many multicast trees are established (such as establishing a multicast tree for each multicast source), the controller will calculate the multicast tree for too long and make the number of traffic bars in the switch too much; if too few groups are established Broadcasting trees (such as building only one multicast tree for all multicast sources) will make the path of the transmission too long and overload the concentration point.

The SDN shared tree multicast stream system proposed by the invention comprises two modules: a group of broadcast tree building modules, and (2) a flow bar setting module. Before the controller transmits the stream at the source end of the multicast, the controller first uses the original topology detection module of the controller to detect the source and the location of the switch. Next, the clustering tree is used to establish a module, and a plurality of multicast trees are established so that all the source terminals and the user terminals are in the multicast tree. Finally, according to the multicast tree, the controller sets the transport packet to the client's traffic bar to the switch on the multicast tree.

An SDN shared tree multicast streaming system is configured to divide a source end of a multicast broadcast into a plurality of clusters before the controller transmits the stream at the source end of the multicast group, and set an exchange with the smallest distance from the source end of the multicast broadcast for each cluster. As a centralized point, the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and uses the concentrated point as the root to establish the shortest path tree to all the multicast users, and according to the shortest path tree, for each The switch on the tree node sets a flow entry, which mainly includes a group of broadcast tree building modules, which are required to establish a transport stream under the distribution of the switch, the multicast source, and the multicast client. Sowing tree, which comprises: a group of broadcast source clustering units, which divides all the multicast source ends into a plurality of clusters; a centralized point selection unit is set after the cluster source end cluster unit to select a cluster distance to be the smallest The switch is used as a centralized point; and a shortest path tree establishing unit is disposed after the centralized point selecting unit to establish a shortest path to the cluster centralized point of all the multicast source ends in each cluster, and to cluster the centralized point For the root, establish the shortest path multicast tree to all the multicast clients; a traffic bar setting module is set after the multicast tree building module, and set the traffic bar on the switch, and the traffic bar includes a group The broadcast source-side traffic bar setting unit sends the stream packet to the cluster by setting the flow bar action for transmitting the flow (flow) to the switch using the OpenFlow protocol (OpenFlow protocol) to set the source stream in the cluster. Concentration point; a centralized point switch flow bar setting unit is to set the source stream in the cluster, and use the OpenFlow protocol to set the VLAN (Virtua) l Local Area Network (virtual area network) tag flow to the switch traffic bar action, to paste the VLAN tag to the stream packet, and send the stream packet to the user; a tree switch flow bar setting unit is To set a stream packet to the VLAN tag, use the OpenFlow protocol to set the flow of the flow to the switch to send the stream packet to the client; and a user switch flow bar setting unit, Set the stream tag on the tagged VLAN tag to remove the VLAN tag and transmit the flow to the switch by using the OpenFlow protocol to remove the VLAN tag on the stream packet and send the stream packet to the stream packet. On the requested client side.

The cluster source end cluster unit includes: a cluster selection unit, which is to calculate the distance between the cluster and the cluster, and select two clusters with the smallest cluster distance; a distance threshold comparison unit is set in the cluster selection unit. Then, according to the two clusters selected according to the cluster selection unit, whether the distance is less than the distance threshold to determine whether the cluster source end cluster unit ends; a load comparison unit is disposed after the distance threshold comparison unit to The cluster selects the two clusters selected by the unit, and whether the total traffic is less than or equal to the maximum switch capacity to determine whether the two clusters are merged. The central point selection unit includes a shortest path calculation unit for calculating a shortest path from a source end to a switch; and a minimum distance sum selection unit, which is disposed after the shortest path calculation unit to select The smallest distance sum of the switches to serve as a cluster concentration point. The shortest path tree establishing unit is a shortest path that includes two shortest path calculations to calculate a shortest path from the source end of the multicast group or the end point of the user end to the cluster set point to establish a shortest path.

An SDN shared tree multicast streaming method includes: Step 1 and topology establishment. When the controller is turned on, the topology detection module and the group management module in the controller are used to obtain the switch and the multicast source. And the distribution of the multicast client; step 2, the establishment of the multicast tree, according to the topology establishment, the source end of the multicast broadcast is divided into a plurality of clusters, and a switch with the smallest distance from the source end of the multicast broadcast is set as a centralized point for each cluster. So that the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and uses the centralized point as the root to establish the shortest path tree to all the multicast users; Step 3: Traffic bar setting, according to the group broadcast tree, Set the traffic bar to the switch on the multicast tree to transmit the multicast stream packet.

The step of establishing the multicast tree includes: step one, clustering the source end cluster, and dividing all the source end sources into a plurality of clusters; Step 2: Select a centralized point to select the switch with the smallest distance selected by each cluster in the cluster source end cluster as the cluster concentration point; Step 3, establish the shortest path tree, and set each cluster concentration point in the centralized point selection to establish The shortest path from each source to the cluster set point, and the shortest path tree from the cluster set point to all the users.

The flow bar setting step includes: Step 1: setting the source traffic bar of the multicast source. For the switch on the path from the source end to the cluster centralized point, setting the traffic bar to meet the condition that the source IP is the multicast source IP. The destination IP is the multicast IP address, and the action is transmitted to the cluster centralized point; in step 2, the centralized point switch traffic bar is set, and for the cluster centralized point, the traffic bar is set to meet the condition that the packet sent from the source end of the cluster is in the cluster, and the action is performed. To paste the cluster VLAN tag and transmit it to all clients; Step 3: Tree switch traffic bar setting, for the switch on the multicast tree, set the traffic bar to meet the condition that the packet of the cluster VLAN tag, the action is transmitted to all User terminal; Step 4: User-side switch traffic bar setting, for the switch connected to the client, set the traffic bar to meet the condition that the packet of the cluster VLAN tag, the action is to remove the cluster VLAN tag on the packet, and transmit the packet to the user. end.

The step of the cluster source end cluster includes: step one: setting each multicast source as a cluster; step two, cluster selection, through Dijkstra algorithm, to calculate the distance between any two clusters, and selecting from the results Smallest distance Two clusters; step three, distance threshold comparison, to determine whether the distance between the current two clusters is less than the distance threshold, and if so, enter the load comparison; otherwise, the cluster source end cluster is ended, and the result is a plurality of clusters; Step 4: The load comparison is to determine whether the current traffic of the two clusters is less than or equal to the maximum switch capacity. If yes, the two clusters are clustered and returned to the cluster selection; otherwise, directly return to the cluster selection, and then Select the two clusters with the smallest distance.

The step of selecting a concentration point includes: step one, shortest path calculation, through Dijkstra algorithm, to calculate a shortest path from a source end to a switch; step two, minimum distance sum selection, calculation result from the shortest path , accumulate the shortest path distances of all multicast sources to the same switch under the same cluster, and select the switch with the smallest distance sum as the cluster concentration point.

The step of establishing the shortest path tree is to include two shortest path calculations to calculate the shortest path from the source end of the multicast group or the end point of the user end to the cluster set point to establish a shortest path tree.

The invention provides an SDN shared tree multicast stream system and method, which mainly relates to how a switch sets a traffic bar so that a packet can be transmitted to a user end, and does not consider the number of traffic sources caused by the number of source channels, thereby affecting Switch performance is not suitable for a large number of multicast sources. When compared with other common technologies, it has the following advantages:

1. The invention utilizes dividing the source end of the multicast into a plurality of clusters, which can be reduced The number of cluster trees.

2. The present invention utilizes a cluster shared group broadcast tree to reduce the time for the controller to calculate the group broadcast tree.

3. The present invention utilizes a cluster shared multicast tree to reduce the number of traffic bars in the switch.

100‧‧‧Topology Detection Module

200‧‧‧Group Tree Building Module

210‧‧‧Communication source cluster unit

211‧‧‧ cluster selection unit

212‧‧‧Distance Threshold Comparison Unit

213‧‧‧Load comparison unit

220‧‧‧ Concentration point selection unit

221‧‧‧ Shortest path calculation unit

222‧‧‧Minimum distance sum selection unit

230‧‧‧ Shortest path tree building unit

300‧‧ ‧ cluster

400‧‧‧ Concentration points

500‧‧‧Group tree

510‧‧‧Group source

520‧‧‧User side

530‧‧‧ Shortest path calculation

600‧‧‧Flow bar setting module

610‧‧‧Group source source flow bar setting unit

620‧‧‧ Concentrated point exchanger flow bar setting unit

630‧‧‧ Tree exchanger flow bar setting unit

640‧‧‧Customer Switch Flow Strip Setting Unit

S7121‧‧‧ Shortest path calculation

S7122‧‧‧Small distance sum selection

S700~S720‧‧‧Process

S720~S728‧‧‧Flow bar setting process

S7111~S7116‧‧‧Communication source clustering process

S810~S850‧‧‧ Shortest path tree establishment process

Please refer to the detailed description of the present invention and its accompanying drawings, which can further understand the technical content of the present invention and its function. The related drawings are: FIG. 1 is a system architecture of an SDN shared tree multicast stream system and method according to the present invention. 2 is an architectural diagram of a multicast source end cluster unit of an SDN shared tree multicast stream system and method according to the present invention; FIG. 3 is a schematic diagram of a centralized point selection unit of an SDN shared tree multicast stream system and method according to the present invention; FIG. 4 is a structural diagram of a shortest path tree establishing unit of an SDN shared tree multicast stream system and method according to the present invention; FIG. 5 is a flowchart of a SDN shared tree multicast stream system and method according to the present invention; A flowchart of a clustering source end cluster of an SDN shared tree multicast stream system and method; FIG. 7 is a flowchart of a centralized point selection step of an SDN shared tree multicast stream system and method according to the present invention; A flowchart of establishing a shortest path tree of an SDN shared tree multicast stream system and method; FIG. 9 is a flow chart of setting a traffic bar of an SDN shared tree multicast stream system and method according to the present invention.

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Hereinafter, the present invention will be further described with reference to the accompanying drawings: Please refer to FIG. 1 , which is a system architecture diagram of an SDN shared tree multicast streaming system and method according to the present invention. The controller divides the source end of the multicast broadcast into a plurality of clusters before the controller transmits the stream at the source end of the multicast. For each cluster, set up a switch with the smallest distance from the source end of the multicast as a centralized point, so that the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and uses the centralized point as the root to establish the shortest path tree to all. The multicast client, and according to the shortest path tree, set a flow entry for each switch on the tree node, mainly including a group of broadcast tree building modules 200, which are at the source of the switch, the multicast, and The multicast network is configured to establish a multicast tree required for the transport stream, and includes: a group of broadcast source end cluster units 210, which divides all the multicast source ends into a plurality of clusters 300; and a centralized point selection unit 220. After being set to the multicast source end cluster unit 210, the switch having the smallest distance among the clusters 300 is selected as the concentration point 400; and a shortest path tree establishing unit 230 is set in the centralized point selection list. After element 220, it is used to establish the shortest path to the cluster concentration point of all the multicast source terminals in each cluster, and establish the shortest path multicast tree to all the multicast users by using the cluster concentration point as the root; The setting module 600 is disposed after the multicast tree building module 200, and sets a traffic bar on the switch, and the traffic bar includes a group of broadcast source side traffic bar setting unit 610, which is set for the source in the cluster. End stream, use the OpenFlow protocol to set the flow bar action of the flow to the switch to send the stream packet to the bundle The centralized point switch flow rate setting unit 620 is configured to set the flow label to the flow of the flow label to the switch by using the OpenFlow protocol to set the flow label to the source stream in the cluster. The stream packet is sent to the user end; the tree switch traffic bar setting unit 630 is configured to set the flow packet to the switch by using the OpenFlow protocol to set the stream packet to the labeled VLAN tag. Acting to send the stream packet to the client; and a client switch flow bar setting unit 640 is configured to remove the VLAN tag and transmit the flow to the stream tag that has been tagged with the OpenFlow protocol. The traffic bar of the switch acts to remove the VLAN tag on the stream packet and send the stream packet to the required client.

Referring to FIG. 2, which is an architecture diagram of a multicast source end cluster unit of the SDN shared tree multicast stream system and method of the present invention, where the multicast source end cluster unit 210 includes: a cluster selection unit 211, Calculating the distance between the cluster and the cluster, and selecting two clusters with the smallest cluster distance; a distance threshold comparing unit 212 is disposed after the cluster selecting unit 211 to select two clusters according to the cluster selecting unit 211, Whether the distance is less than the distance threshold to determine whether the cluster source end cluster unit ends; a load comparison unit 213 is disposed after the distance threshold comparison unit 212 to select the two clusters according to the cluster selection unit 211, the total of which is Whether the traffic is less than or equal to the maximum switch capacity to determine whether the two clusters are merged.

Referring to FIG. 3, it is an architectural diagram of a centralized point selection unit of an SDN shared tree multicast stream system and method according to the present invention. The centralized point selection unit 220 includes a shortest path calculation unit 221, which is to calculate a group. The shortest path from the source to the switch; and a minimum distance sum selection unit 222 is disposed after the shortest path calculation unit 221 to select the most The small distance sum of the exchangers to serve as a cluster concentration point.

Referring to FIG. 4, an architecture diagram of a shortest path tree establishing unit of the SDN shared tree multicast streaming system and method according to the present invention, wherein the shortest path tree establishing unit includes a second shortest path calculation 530 to calculate a multicast source. The shortest path from the end 510 or the client 520 to the cluster concentration point 400 to establish the shortest path of the multicast tree 500.

Referring to FIG. 5, it is a flowchart of an SDN shared tree multicast stream system and method according to the present invention, and an SDN shared tree multicast stream method, including: Step 1 and topology establishment S700, when the controller is turned on, The distribution of the switch, the multicast source, and the multicast client is obtained by using the existing topology detection module and the group management module in the controller. Step 2: The cluster tree is established with S710, and the S700 is established according to the topology. The source end of the multicast broadcast is divided into a plurality of clusters, and a switch with the smallest distance from the source end of the multicast broadcast is set as a centralized point for each cluster, so that the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and concentrates The point is the root, and the shortest path tree is established to all the multicast clients. Step 3: The traffic bar is set to S720, the S710 is established according to the multicast tree, and the switch of the traffic bar in the multicast tree is set to transmit the multicast stream packet. .

The step of establishing the S710 multicast tree includes: Step 1: S711 multicast source end cluster, dividing all the multicast source ends into a plurality of clusters; Step 2, S712 centralized point selection, and grouping the source end clusters each. The cluster selects the switch with the smallest distance as the cluster set Midpoint; Step 3: S713 shortest path tree is established, each cluster point in the cluster selection will be selected, the shortest path from each source to the cluster point, and the shortest from the cluster point to all the users. Path tree.

Please refer to FIG. 9 , which is a flowchart of setting a traffic bar of an SDN shared tree multicast streaming system and method according to the present invention. The step of setting the S720 traffic bar includes: Step 1 : S721 multicast source flow bar setting, For the switch on the source to the cluster centralized point path, the S722 sets the traffic bar to meet the following conditions: the source IP is the multicast source IP address, the destination IP is the multicast IP address, and the action is transmitted to the cluster aggregation point; Second, the S723 centralized point switch traffic bar is set. For the cluster concentration point, the S724 sets the traffic bar to meet the condition: the packet sent from the source end of the cluster in the cluster, the action is to affix the cluster VLAN tag and transmit to all the clients. Step 3: S725 tree switch traffic bar setting. For the switch on the multicast tree, the S726 sets the traffic bar to meet the condition: the packet of the cluster VLAN tag, the action is transmitted to all clients; step 4, S727 client The switch traffic bar is set. For the switch connected to the client, the S728 setting traffic bar meets the condition that: the packet of the cluster VLAN tag, the action is to remove the cluster VLAN tag on the packet. Sign and send the packet to the client.

Please refer to FIG. 6 , which is a flowchart of a cluster source end cluster of an SDN shared tree multicast stream system and method according to the present invention. The step of the S711 multicast source end cluster includes: Step 1 and S7111 set each multicast group. The source is a cluster; Step 2, S7112 cluster selection, through the Dijkstra algorithm, to calculate the distance between any two clusters, select the two clusters with the smallest distance from the results; Step 3, S7113 distance threshold comparison, Determine whether the distance between the two clusters is less than the distance threshold, and if so, enter the load comparison; otherwise, end the cluster source cluster S7114, the result is a plurality of clusters; Step 4, S7115 load comparison, is to determine the current two Whether the traffic of the clusters is less than or equal to the maximum switch capacity, if so, the two clusters are clustered with the S7116 cluster and returned to the S7112 cluster selection; otherwise, directly return to the S7112 cluster selection, and reselect the two clusters with the smallest distance.

Please refer to FIG. 7 , which is a flowchart of a centralized point selection step of the SDN shared tree multicast stream system and method according to the present invention, wherein the S712 centralized point selection includes: Step 1 and shortest path calculation S7121, through the Dijkstra algorithm, To calculate the shortest path from the source end of a multicast source to a switch; step 2, the sum of the minimum distances selects S7122, and the result of the calculation from the shortest path accumulates the shortest path distance of all the multicast sources to the same switch under the same cluster. And choose the switch with the smallest distance sum as the cluster concentration point.

Please refer to FIG. 8 , which is a flowchart of establishing a shortest path tree of an SDN shared tree multicast stream system and method according to the present invention. The step of establishing a shortest path tree includes the S840 second shortest path calculation to calculate a multicast source. The shortest path from the end S810 or the client S820 to the cluster concentration point S830 to establish the shortest path tree S850.

The detailed description of the present invention is intended to be illustrative of a preferred embodiment of the invention, and is not intended to limit the scope of the invention. The patent scope of this case.

To sum up, this case is not only innovative in terms of technical thinking, but also has many of the above-mentioned functions that are not in the traditional methods of the past. It has fully complied with the statutory invention patent requirements of novelty and progressiveness, and applied for it according to law. Approved this invention patent application, in order to invent invention, to the sense of virtue.

100‧‧‧Topology Detection Module

200‧‧‧Group Tree Building Module

210‧‧‧Communication source cluster unit

220‧‧‧ Concentration point selection unit

230‧‧‧ Shortest path tree building unit

300‧‧ ‧ cluster

400‧‧‧ Concentration points

500‧‧‧Group tree

600‧‧‧Flow bar setting module

610‧‧‧Group source source flow bar setting unit

620‧‧‧ Concentrated point exchanger flow bar setting unit

630‧‧‧ Tree exchanger flow bar setting unit

640‧‧‧Customer Switch Flow Strip Setting Unit

Claims (10)

An SDN (Software Defined Networking) shared tree multicast streaming system is configured by the controller to divide the source end of the multicast broadcast into a plurality of clusters before transmitting the stream at the source end of the multicast broadcast, and set up a cluster for each cluster. A switch with the smallest distance from the source end of the multicast broadcast is used as a centralized point, so that the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and the centralized point is used as the root to establish the shortest path tree to all the multicast clients. According to the shortest path tree, a flow entry is set for each switch on the tree node, which mainly includes: a group of broadcast tree building modules, which are distributed on the switch, the multicast source, and the multicast client. Next, the multicast tree required for the transport stream is established, which comprises: a group of broadcast source clustering units, which divides all the multicast source ends into a plurality of clusters; and a centralized point selection unit is set at the source end of the multicast broadcast. After the cluster unit, the switch having the smallest cluster distance is selected as the concentration point; and a shortest path tree establishing unit is disposed after the set point selecting unit, All the multicast source sources in each cluster establish the shortest path to the cluster concentration point, and use the cluster concentration point as the root to establish the shortest path multicast tree to all the multicast users; a traffic bar setting module is set in After the cluster tree establishes a module, and sets a traffic bar on the switch, it includes: a group of broadcast source-side traffic bar setting units, configured to set the source-side stream in the cluster, and utilize OpenFlow protocol (OpenFlow) Agreement) sets the flow bar action of transmitting flow (flow) to the switch to send the stream packet to the cluster concentration point; A centralized switch flow bar setting unit is configured to set a flow to the switch of the VLAN (Virtual Local Area Network) tag by using the OpenFlow protocol to set the source stream in the cluster. , the VLAN tag is attached to the stream packet, and the stream packet is sent to the user end; a tree switch flow bar setting unit is configured to set the flow packet for the tagged VLAN tag, and use the OpenFlow protocol to set the flow to be transmitted. The flow bar to the switch acts to send the stream packet to the client; and a client switch flow bar setting unit is configured to set the VLAN tag to the streamed packet, and use the OpenFlow protocol to remove the VLAN. The tag also transmits a flow bar action to the switch to remove the VLAN tag on the stream packet and send the stream packet to the required client. The SDN shared tree multicast stream system according to claim 1, wherein the multicast source cluster unit comprises: a cluster selection unit, which calculates the distance between the cluster and the cluster, and selects the cluster. The minimum two clusters; a distance threshold comparison unit is disposed after the cluster selection unit to select whether the distance is less than the distance threshold according to the two clusters selected by the cluster selection unit to determine the cluster source end cluster Whether the unit ends; a load comparison unit is disposed after the distance threshold comparison unit to determine whether the two clusters are equal to or greater than the maximum switch capacity according to the two clusters selected by the cluster selection unit Consolidate. For example, the SDN shared tree multicast stream system described in claim 1 of the patent scope, The central point selection unit includes: a shortest path calculation unit for calculating a shortest path from a source end to a switch; and a minimum distance sum selection unit, which is disposed after the shortest path calculation unit. To select the switch with the smallest distance sum as the cluster concentration point. The SDN shared tree multicast stream system as described in claim 1, wherein the shortest path tree establishing unit includes two shortest path calculations to calculate a shortest path of the source source or the client to the cluster concentration point. To establish a shortest path to the multicast tree. An SDN shared tree multicast streaming method includes: Step 1 and topology establishment. When the controller is turned on, the topology detection module and the group management module in the controller are used to obtain a switch and a multicast source. The distribution of the end and the multicast client; step 2, the establishment of the multicast tree, according to the topology, the source end of the multicast is divided into a plurality of clusters, and a switch with the smallest distance from the source end of the multicast is set for each cluster as Concentration point, so that the source end of the multicast group in the same cluster establishes the shortest path to the centralized point, and uses the centralized point as the root to establish the shortest path tree to all the multicast users; Step 3: Traffic bar setting, according to the multicast The tree establishes a switch that sets the traffic bar on the multicast tree to transmit the multicast stream packet. The method for establishing an SDN shared tree multicast stream according to claim 5, wherein the step of establishing the multicast tree includes: step 1: grouping the source end cluster, and dividing all the source sources into a plurality of clusters. ; Step 2: Selecting a centralized point, selecting the switch with the smallest selection distance of each cluster in the cluster end cluster as the cluster concentration point; Step 3, establishing the shortest path tree, and selecting each cluster concentration point in the centralized point selection Establish the shortest path from each source to the cluster set point and establish the shortest path tree from the cluster set point to all the users. The SDN shared tree multicast stream method as described in claim 5, wherein the step of setting the traffic bar includes: Step 1: setting the source traffic bar of the multicast source, for the source to the cluster concentration point The switch on the path sets the traffic bar to meet the condition that the source IP is the multicast source IP address, the destination IP is the multicast IP address, and the action is transmitted to the cluster aggregation point; step 2, the centralized point switch traffic bar setting, for the cluster concentration Point, set the traffic bar to meet the conditions for the packet sent from the source end of the cluster, the action is to paste the cluster VLAN tag, and transmit to all the users; Step 3, the tree switch traffic bar setting, for the multicast tree The switch sets the flow bar to meet the conditions of the packet of the cluster VLAN tag, and the action is transmitted to all the users; the fourth step is to set the traffic bar of the user switch, and for the switch connected to the client, the traffic bar is set to meet the condition of the cluster VLAN tag. Packet, the action is to remove the cluster VLAN tag on the packet and send the packet to the client. The SDN shared tree multicast stream method as described in claim 6, wherein the step of the cluster source end cluster includes: Step 1: Set each multicast source to be a cluster; Step 2, Cluster selection, through Dijkstra algorithm, to calculate the distance between any two clusters, select the two clusters with the smallest distance from the result; Step 3, Distance Threshold comparison to determine whether the distance between the two clusters is less than the distance threshold, and if so, enter the load comparison; otherwise, the cluster source end cluster is ended, and the result is a plurality of clusters; step four, the load comparison, Determine whether the traffic of the current two clusters is less than or equal to the maximum switch capacity. If so, the two clusters are clustered and returned to the cluster selection; otherwise, directly return to the cluster selection, and reselect the two clusters with the smallest distance. . For example, the SDN shared tree multicast stream method described in claim 6 wherein the step of selecting a centralized point includes: step one, shortest path calculation, and calculating a multicast source to a certain by Dijkstra algorithm The shortest path of the switch; step 2, the minimum distance sum selection, from the result of the shortest path calculation, accumulate the shortest path distance of all the multicast sources to the same switch under the same cluster, and select the switch with the smallest distance sum As the focus of the cluster. The SDN shared tree multicast stream method as described in claim 6, wherein the step of establishing the shortest path tree includes two shortest path calculations to calculate the shortest source of the multicast source or the minimum of the user end to the cluster concentration point. Path to establish the shortest path tree.