CN101247253A - Multicast Transmission Method Based on Virtual Distribution Network in IP Network - Google Patents

Abstract

The invention relates to a multicast transmission method in an IP network, belonging to the technical field of computer communication. The method includes, firstly establishing a virtual distribution network for each multicast session in the IP network, the virtual distribution network is formed by connecting all user hosts participating in the multicast session and routers with a multicast function through virtual links, and It has a unique virtual distribution network identifier; then, on the virtual distribution network, the sending user host transmits the multicast data packet to all receiving user hosts by broadcasting. On the one hand, the present invention maintains the advantages of the original multicast transmission method based on the virtual distribution network, such as supporting the gradual deployment of network layer multicast, supporting the bidirectional transmission of multicast data packets, etc., and on the other hand, simplifying the virtual distribution network The configuration is conducive to supporting large-scale multicast applications and ensuring the correct transmission of multicast data packets through the broadcast mechanism.

Description

Multicast Transmission Method Based on Virtual Distribution Network in IP Network

technical field

The invention belongs to the technical field of computer communication, in particular to a multicast (Multicast) transmission method in an IP network.

Background technique

Multicast is an efficient point-to-multipoint or multipoint-to-multipoint transmission method. At present, the main services provided in the IP network, such as information retrieval, e-mail, instant messaging, etc., are based on the unicast transmission (that is, point-to-point transmission) technology of establishing data packets. However, many emerging services, such as Internet TV (IPTV), large-scale network conferencing, and large-scale distributed simulation, involve the simultaneous interaction of a large number of computers. If unicast is still used, a large amount of network bandwidth resources will be wasted, and performance is difficult to guarantee. Multicasting provides an effective point-to-multipoint and multipoint-to-multipoint transmission mechanism, which is the key to the smooth development of these services.

In order to support multicasting on IP networks, many schemes have been proposed, among which there are mainly two kinds of schemes currently being applied: IP multicasting and application layer multicasting. However, there are a series of deployment and application difficulties in IP multicast: such as the lack of progressive deployment capabilities, unmanageable and controllable multicast services, lack of scalability for inter-domain multicast, etc. These problems limit IP Large-scale deployment and application of multicast. On the other hand, the application layer multicast is difficult to meet the needs of future multicast services, such as the support for high-speed real-time video broadcast services. Therefore, there is still a need to study new network layer multicast methods.

Aiming at the problems existing in the existing IP multicast solution, the inventor of this patent proposed a "multicast transmission method based on a virtual distribution network in an IP network" and applied for a patent (application number 200710099365.4). This method is as follows: First, a virtual distribution network is established for each multicast session in the network; the virtual distribution network is formed by connecting multiple nodes in the IP network through virtual links, wherein the nodes include participating All user hosts and other selected nodes of the multicast session; two nodes connected by a virtual link are called each other's virtual neighbors; the virtual distribution network has a unique IP address identifier, which is used to distinguish Multiple virtual distribution networks; each node on the virtual distribution network establishes and maintains a distribution table, where each table entry includes at least: the identity of the virtual distribution network, the list of virtual neighbors, and the forwarding authority of control data packets between virtual neighbors Then, in the virtual distribution network, when the sending host sends business data, set the IP address of the receiving host as the IP address identifier of the virtual distribution network; each node on the virtual distribution network distributes the IP data packets until the IP The data packet is delivered to all receiving hosts in the virtual distribution network. The above-mentioned patented invention has many advantages, such as supporting the gradual deployment of multicast at the network layer, better adapting to the dynamic changes of the network structure, supporting bidirectional transmission of multicast data packets, and providing a simple and effective multicast transmission control method. These advantages facilitate the deployment of network layer multicast.

However, there is a problem in the above multicast solution: the configuration of the distribution table has a problem of scalability, which is mainly caused by the use of the set of forwarding authority flags to control the transmission of multicast data packets. As described in the implementation of this patent (Application No. 200710099365.4), each forwarding permission flag set can be represented by an N×N matrix, where N is the number of virtual neighbors of the current node on the virtual distribution network, When the number of virtual neighbors is small, the configuration of the forwarding permission flag set is relatively simple. When the number of virtual neighbors is large, a large number of forwarding flags need to be configured, and the forwarding permission flag set will also occupy more Storage space, for example, when N=20, you need to configure 20×20=400 flags, and the storage space occupied by the optical forwarding authority flag in an entry is greater than 50 bytes. If the number of N is 30, you need If 30×30=900 flags are configured, the storage space occupied by the optical forwarding authority flag in one entry is greater than 110 bytes. When the scale of the virtual distribution network is very large (such as tens of thousands of nodes), it is more complicated to configure the distribution tables on these nodes whether manually or through the protocol. Therefore, the virtual distribution network based on the forwarding authority flag set has an extended sexual issues.

In addition, a certain mechanism needs to be added to ensure the correctness of the set of forwarding permission flags. The forwarding permission flag set guides the multicast data packet from the sending user host to all receiving user hosts. When the forwarding permission flag configuration is correct, the multicast data packet can be transmitted correctly. However, if the forwarding permission flag set appears in the configuration If there is a problem, it will lead to a transmission failure of the multicast data packet, such as a loop (Loop), that is, the data packet is repeatedly transmitted in the network. Therefore, an additional mechanism needs to be added to this transmission method to ensure the correctness of the configuration of the forwarding permission flag set.

In order to solve the above two problems, we need to study a new virtual distribution network structure and a multicast transmission method based on this virtual distribution network.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose a simplified virtual distribution network structure and a new multicast transmission method based on this virtual distribution network. This method maintains the basis of the advantages of the original method In addition, it further simplifies the configuration process of the virtual distribution network, which is beneficial to support large-scale multicast applications and ensure the correct transmission of multicast data packets.

The multicast transmission method in the IP network proposed by the present invention is characterized in that the method is a multicast transmission method based on a virtual distribution network, comprising: first, setting up a virtual distribution network for each multicast session in the IP network; The virtual distribution network is formed by connecting multiple virtual distribution network nodes through virtual links, and the multiple virtual distribution network nodes include at least all user hosts participating in multicast sessions and one router node with multicast function , the virtual link refers to the logical transmission channel connecting the nodes of the virtual distribution network, and the two nodes connected by the virtual link are called each other's virtual neighbors; the virtual distribution network has a unique virtual distribution network identification, which is used for Distinguishing multiple virtual distribution networks in an IP network; establishing and maintaining a distribution table on some or all nodes of the virtual distribution network, said part of nodes at least including all routers on the virtual distribution network, said distribution table It consists of one or more distribution table entries, each of which corresponds to a virtual distribution network and includes at least the following content: virtual distribution network identifier, IP address of one or more virtual neighbors; and , on the virtual distribution network, the sending user host broadcasts the multicast data packet to all receiving user hosts.

Compared with the original multicast transmission method based on the virtual distribution network, the present invention maintains the advantages of the original method, such as supporting the progressive deployment of multicast, supporting the bidirectional transmission of multicast data packets, and supporting the process of multicast transmission. control etc., in addition, other beneficial effects of the present invention include:

The configuration process of the virtual distribution network is simplified, which is beneficial to support large-scale multicast applications. In this kind of virtual distribution network, each distribution table can establish a virtual distribution network as long as the virtual neighbor relationship is determined between each node, and there is no need to configure the forwarding permission flag set of each node. This will greatly simplify the configuration process of the virtual distribution network, whether it is manually configured or dynamically configured through the protocol, which is conducive to supporting large-scale multicast applications.

Ensure the correct delivery of multicast packets. In this patent, the broadcast on the virtual distribution network is used to realize the multicast on the Internet. No matter which broadcast mechanism (diffusion method, or spanning tree, etc.) Receive user host.

Description of drawings

Fig. 1 is a schematic diagram of the embodiment network of the method of the present invention and the virtual distribution network V0.

Fig. 2 is a schematic diagram of the distribution table of each node on the virtual distribution network V0 of the method of the present invention.

Fig. 3 is a schematic diagram of the transmission process of the multicast data packet in the method of the present invention (sending host H1, diffusion method).

FIG. 4 is a schematic diagram of a single spanning tree on the virtual distribution network V0 of the method of the present invention.

Fig. 5 is a schematic diagram (single spanning tree) of the distribution table of each node on the virtual distribution network V0 of the method of the present invention.

Fig. 6 is a schematic diagram of the transmission process of the multicast data packet in the method of the present invention (sending host H1, spanning tree, unidirectional).

Fig. 7 is a schematic diagram of the transmission process of the multicast data packet in the method of the present invention (sending host H4, spanning tree, bidirectional).

FIG. 8 is a schematic diagram of two spanning trees on the virtual distribution network V0 of the method of the present invention.

FIG. 9 is a schematic diagram (two spanning trees) of the distribution table of each node on the virtual distribution network V0 of the method of the present invention.

Fig. 10 is a schematic diagram of the transmission process of the multicast data packet in the method of the present invention (sending host H4, spanning tree, bidirectional).

Fig. 11 is a schematic diagram of controlling the sending and receiving of each user host in the method of the present invention.

Fig. 12 is a schematic diagram of setting the sending and receiving authority of each virtual neighbor on the router according to the method of the present invention.

Fig. 13 is a schematic diagram of the embodiment network of the method of the present invention and the virtual distribution network V1.

Detailed ways

Method of the present invention is described in detail as follows in conjunction with accompanying drawing and embodiment:

An IP network structure of an embodiment of the method of the present invention is shown in FIG. 1 . The network in this embodiment consists of seven hosts (H1-H7) and seven routers (R1-R7). In the network of this embodiment, it is assumed that a video conference multicast session S is carried out among four hosts (host H1, host H2, host H4, and host H5). The following content describes the process of implementing the method of the present invention in this IP network. These descriptions are only illustrative illustrations of the present invention, and should not be regarded as limiting the content of the present invention.

The network in this embodiment is a network using the IP protocol. At present, the IP protocol has two versions, IPv4 and IPv6, and the multicast transmission method can be applied to both the IPv4 network and the IPv6 network. The network in this embodiment is described using the IPv4 protocol.

The method of this embodiment mainly includes the following steps:

First, a virtual distribution network V0 is established for the multicast session S, as shown in Fig. 1 . The virtual distribution network V0 is formed by connecting four user host nodes (H1, H2, H4, H5) participating in the multicast session S and three router nodes (R1, R3, R7) with multicast function through virtual links . Two nodes connected by a virtual link are called each other's virtual neighbors. Therefore, on the virtual distribution network, router R1 has three virtual neighbors (H1, R3, R7), and router R3 also has three virtual neighbors (R1, H2 and R7), the router R7 has four virtual neighbors (R1, R3, H4, H5), the user host H1 has only one virtual neighbor R1; the user host H2 has only one virtual neighbor R3, and the virtual neighbors of the user hosts H4 and H5 are both R7 .

In the IP network, a unique virtual distribution network identifier is assigned to the virtual distribution network V0, which can be used to distinguish V0 from other virtual distribution networks established in the IP network. In this embodiment, the unicast IP address of the router R1 on the virtual distribution network is used to identify V0, the method is: add a virtual network interface on the router R1, and assign a unicast IP address (166.111.64.2) to it, and then Use this IP unicast address as the identifier of the virtual distribution network V0. In this case, the router R1 is called the master node of the virtual distribution network V0.

Each node of V0 on the virtual distribution network sets a distribution table, and each entry in the distribution table corresponds to a virtual distribution network that the node joins, and includes the following content: the identity of the virtual distribution network, one or more IP address of a virtual neighbor. Figure 2 shows the distribution table of each node on the virtual distribution network, each sub-graph a, b, c, d, e, f, g is host H1, host H2, host H4, host H5, router R1, router R3, Distribution table of router R7. It is assumed here that there is only one virtual distribution network V0 in this IP network, therefore, each distribution table contains only one distribution table entry. The above-mentioned distribution tables can be established manually or automatically by agreement. Once the distribution tables on these nodes are set up, it means that the virtual distribution network is established successfully. It should be pointed out that when the user host is only used as a receiving host, the distribution table on it can be omitted, because the user host does not need to send multicast data packets to other virtual neighbors on the virtual distribution network. Therefore, the distribution table on the virtual distribution network Some user hosts do not need to set distribution tables.

Then, on the virtual distribution network V0, the sending user host transmits the multicast data packet to all receiving user hosts by means of broadcasting. In order to realize the broadcast of multicast data packets on the virtual distribution network V0, two commonly used broadcast methods are the diffusion method or the spanning tree method, which are introduced as follows:

(1) The diffusion method assumes that the sending user host is H1, and H1 directly sends the multicast packet to its virtual neighbor R1 on the virtual distribution network V0. The source address of the multicast packet is the IP address of H1, and the destination address is The IP address of R1, at the same time, in the header of the data packet, the following information is embedded in the form of IP option or new protocol header: the identification of the virtual distribution network, the address of the sending user host and the sequence number of the sending multicast data packet. Here, it is assumed that the multicast data packet to be sent is the first one, that is, its sending sequence number is 1.

Each router node of the virtual distribution network needs to add the following information to the corresponding entry in the distribution table: the IP address of the sending user host H1 and the maximum sequence number of the received multicast data packet from H1. Here, for the sake of simplicity, it is assumed that the initial values of these maximum sequence numbers are all 0.

When any router node on the virtual distribution network receives a multicast data packet from one of its virtual neighbors, the process is as follows: the router node first extracts the virtual distribution network identifier from the header of the data packet and queries the distribution table to find the The distribution table entry corresponding to the virtual distribution network; then, the router finds the maximum sequence number of the received multicast data packet corresponding to the sending user host of the multicast data packet in the distribution table entry, and compares it with the The sending sequence number in the multicast data packet is compared: if the sending sequence number of the multicast data packet is greater than the maximum received sequence number, it means that the router has not forwarded the multicast data packet, and the router forwards it to the sender All other virtual neighbors except the virtual neighbor of the multicast data packet, on the other hand, adjust the received maximum sequence number to the sending sequence number of the multicast data packet; otherwise, if the sending sequence number of the multicast data packet is less than or equal to the The maximum sequence number received means that the router has forwarded the multicast data packet, and the router discards the multicast data packet.

According to the above process, when router R1 receives the multicast packet from virtual neighbor H1, it finds that the sequence number of the multicast packet (1) is greater than the received maximum sequence number (0) corresponding to the sending user host H1, so , router R1 transmits it to all other virtual neighbors (router R3 and router R7) except the virtual neighbor that sent the multicast data packet, the source address of the data packet is switched to R1, the destination address is switched to R3 or R7, and other The header information remains unchanged; in addition, router R1 updates the received maximum sequence number corresponding to H1 to 1.

Here, the present invention assumes that the delay of each physical link in the actual network is the same, therefore, the multicast data packet sent by R1 will first arrive at router R3. R3 finds that the sequence number (1) of the multicast data packet is greater than the received maximum sequence number (0) corresponding to the sending user host H1, so router R3 transmits it to all virtual neighbors except the virtual neighbor that sent the multicast data packet For all other virtual neighbors (host H2 and router R7), the source address of the data packet is switched to R3, and the destination address is switched to H2 or R7; in addition, router R3 updates the received maximum sequence number corresponding to H1 to 1.

Subsequently, router R7 also receives the multicast data packet from virtual neighbor R1. R7 finds that the sequence number (1) of the multicast data packet is greater than the received maximum sequence number (0) corresponding to the sending user host H1, so router R7 transmits it to all virtual neighbors except the virtual neighbor that sent the multicast data packet For all other virtual neighbors (host H4 and host H5 and router R3), the source address of the packet is switched to R7, and the destination address is switched to H4 or H5 or R7; in addition, router R7 updates the received maximum sequence number corresponding to H1 to 1 .

Afterwards, router R7 also receives the multicast data packet from virtual neighbor R3. R7 finds that the serial number (1) of the multicast data packet is equal to the received maximum serial number (1) corresponding to the sending user host H1, therefore, R7 directly discards the multicast data packet. Similarly, when router R3 receives duplicate multicast packets from virtual neighbor R7, it also discards them.

After the above process, the multicast data packet has been transmitted to all other user hosts, user hosts H2, H4 and H5. The diffusion process of the above multicast data packets is shown in FIG. 3 .

(II) Spanning tree method - a single tree first establishes a spanning tree that connects all nodes on the virtual distribution network, which is called the distribution tree of the virtual distribution network, and then the sending host can be transmitted to the virtual distribution network along this distribution tree All receiving user hosts.

A method of establishing a distribution tree is: first, select a root node; then send a control packet from the root node to diffuse to the entire virtual distribution network; for a node of the virtual distribution network that receives the control packet, if the first Once receiving the control packet from its virtual neighbor, it will mark the virtual neighbor sending the control packet as the upstream virtual neighbor, and mark the other virtual neighbors as the virtual neighbors outside the tree, and then the node sends confirmation information to the upstream virtual neighbor (upstream After receiving the confirmation message, the node identifies the node as a downstream virtual neighbor), and at the same time transmits the control packet to all other virtual neighbors except the upstream virtual neighbor; if the control packet is not received for the first time, then throw it away. In this way, once the control packet spreads to the entire virtual distribution network, the upstream and downstream nodes of each node have been determined, that is, a distribution tree has been established.

Here, the distribution tree with R1 as the root node is shown in Figure 4, where links on the distribution tree are marked with thick dashed lines, and other links that do not belong to the distribution tree are marked with thin dashed lines (two subgraphs (a), (b ) is the same, but adjusted the display effect). On each node of the distribution tree, it is necessary to mark whether its virtual neighbor is an upstream virtual neighbor or a downstream virtual neighbor, and mark a virtual neighbor that is neither an upstream virtual neighbor nor a downstream virtual neighbor as an out-of-tree virtual neighbor (in the specific implementation can be marked with 2 bits, for example, 00 represents the upstream virtual neighbor, 01 represents the downstream virtual neighbor, and 1x represents the virtual neighbor outside the tree). Save the marked results to the corresponding entries in the distribution table, as shown in Figure 5. Each subgraph a, b, c, d, e, f, g is the distribution table of host H1, host H2, host H4, host H5, router R1, router R3, and router R7 respectively.

After the distribution tree is established, any user host can use this distribution tree to transmit multicast data packets. Here, there are two transmission modes: one-way transmission mode and two-way transmission mode, examples are as follows:

(2a) One-way transmission method

Assume that the sending user host is H1. H1 can use unidirectional transmission to transmit multicast data packets along the distribution tree to all receiving hosts. The detailed transmission process is as follows:

H1 first sends the multicast data packet to the root node R1 of the distribution tree, the source address of the multicast data packet is the address of H1, and the destination address is the identifier of the virtual distribution network V0. Since the identifier of the virtual distribution network is the unicast IP address of the router R1, the data packet is sent to R1.

After receiving the multicast data packet, R1 can judge that the data packet is to be sent to the virtual distribution network V0 according to its destination address. Therefore, R1 searches its own distribution table, finds the distribution table entry corresponding to the virtual distribution network V0, and obtains R1 The downstream virtual neighbors: user host H1, router R3 and router R7. From the source address of the packet, R1 can know that the multicast data packet comes from the user host H1, therefore, R1 directly forwards the multicast data packet to other downstream virtual neighbors: router R3 and router R7.

The source address of the data packet sent by R1 to router R3 is R1, and the destination address is R3. In addition, R1 also needs to insert the virtual distribution network identifier into the multicast data packet in the form of an IP option (IP Option) or a new protocol header. head. Obviously, the packet will be routed to R3. After receiving the data packet, R3 can extract the virtual distribution network identifier from the header of the multicast data packet, then search the distribution table, find the distribution table entry corresponding to the virtual distribution network identifier, and extract the downstream virtual distribution network identifier from the entry. Neighbor H2, finally R3 sends the multicast data packet to the user host H2, wherein the source address of the multicast data packet is switched to R3, and the destination address is switched to H2.

Similarly, the process of R1 sending the data packet to R7 is similar. After receiving the multicast data packet, R7 further sends it to its downstream virtual neighbors: user host H4 and user host H5.

In this way, the multicast data packet sent by H1 reaches all other user hosts (H2, H4 and H5) on the virtual distribution network along the distribution tree. The above transmission process is shown in FIG. 6 .

(2b) Two-way transmission method

The sending user host can also send the multicast data packet to all other user hosts in a two-way transmission mode. Here, it is assumed that the sending user host in a two-way transmission mode is H4.

The sending user host H4 first sends the multicast data packet to its upstream virtual neighbor R7. The source address of the multicast data packet is the address of H4, and the destination address is the address of R7. In addition, H4 needs to identify the virtual distribution network as An IP option (IP Option) or a new protocol header is inserted into the header of the multicast packet. After R7 receives the multicast data packet, it can extract the virtual distribution network identifier from the header of the multicast data packet, then search the distribution table, find the distribution table entry corresponding to the virtual distribution network identifier, and obtain the corresponding distribution table entry from the entry. Extract its upstream virtual neighbor and downstream virtual neighbor, where the upstream virtual neighbor is R1, and the downstream virtual neighbors are R4 and R5. Since the multicast data packet comes from the downstream virtual neighbor R4, the router R7 sends the multicast data packet to other virtual neighbors R1 and R5. The source address of the multicast packet sent by R7 to R1 is R7, and the destination address is R1. In addition, R7 also needs to insert the identity of the virtual distribution network into the multicast data in the form of an IP option (IP Option) or a new protocol header. The header of the package. When router R1 receives the multicast data packet, it judges that the multicast data packet comes from its downstream virtual neighbor R7, so router R1 sends the multicast data packet to other downstream virtual neighbors: router R3 and user host H1 . Similarly, after receiving the multicast data packet, router R3 forwards it to its downstream virtual neighbor H2. In this way, the multicast data packet is transmitted from user host H4 to all other user hosts H1, H2 and H5. The above transmission process is shown in FIG. 7 .

(III) Spanning tree method - multiple trees

In the above-mentioned unidirectional transmission or multi-directional transmission, all sending user hosts transmit multicast data packets to all other nodes on the virtual distribution network through a distribution tree. In this embodiment, multiple distribution trees can be established on a virtual distribution network, and different sending user hosts can select different distribution trees to improve the transmission performance of packets. Figure 8 shows two distribution trees established on the virtual distribution network, wherein sub-graph 8(a) is the aforementioned distribution tree T0 with R1 as the root node, and sub-graph 8(b) is based on R7 as the root node Distribution tree T1, where links on the distribution tree are marked with thick dashed lines, and other links that do not belong to the distribution tree are marked with thin dashed lines.

Figure 9 shows the distribution tables that are stored on each node, where the subgraphs a, b, c, d, e, f, and g are respectively host H1, host H2, host H4, host H5, router R1, and router R3 , the distribution table of the router R7. In order to distinguish different distribution trees belonging to the same virtual distribution network, it is necessary to assign an identifier to each distribution tree. A simple method is to follow the order in which the distribution trees are established. For example, the identifier for T0 is 0, and the identifier for T1 is 1. ,So on and so forth. For each node on the virtual distribution network, the upstream virtual neighbors and downstream virtual neighbors of the distribution trees T0 and T1 need to be marked respectively.

For the sending user host H4, a distribution tree is first selected. Since the root node of the distribution tree T1 is closer to the sending user host H4 than the root node of T0, H4 chooses the distribution tree T1 to improve the transmission performance of the packet. After selecting the distribution tree, the sending user host can still choose whether to use one-way transmission or two-way transmission to transmit multicast data packets. Here, it is assumed that H4 uses two-way transmission to transmit multicast data packets:

The sending user host H4 sends the multicast data packet to its upstream virtual neighbor on T1, that is, the router R7, wherein the source address of the multicast data packet is the address of H4, the destination address is the address of R7, and the virtual distribution network and the identifier of the adopted distribution tree T1 are stored in the header of the multicast data packet (using IP option or new protocol header). After receiving the multicast data packet, R7 extracts the virtual distribution network identifier from the header of the multicast data packet, finds the corresponding distribution table item, then extracts the identifier of the distribution tree, and finds the upstream and downstream virtual neighbors corresponding to T1: there are 4 downstream virtual neighbors in total. The neighbors are R1, R3, H4 and H5 respectively. Since the multicast packet came from H4, R7 delivers it to all other downstream virtual neighbors: R1, R3, and H5. The source address of the multicast data packet sent by R7 to R1 and R3 is R7, the destination address is R1 and R3 respectively, and at the same time, the identity of the virtual distribution network and the identity of the distribution tree T1 used are saved in the header of the multicast data packet (using IP options or new protocol headers). After receiving the multicast data packet, R1 sends it to the downstream virtual neighbor H1 on the distribution tree T1. After receiving the multicast data packet, R3 sends it to the downstream virtual neighbor H2 on the distribution tree T1. The above transmission process is shown in FIG. 10 . Comparing Fig. 10 and Fig. 7, it is obvious that when the sending user host H4 adopts the distribution tree T1 to transmit the multicast data packet, it can save delay compared with the transmission using the distribution tree T0.

In the above-described embodiment, the topology of the virtual distribution network V0 is a mesh, and the method of the present invention can also directly establish a tree-shaped virtual distribution network, that is, the established virtual distribution network is a virtual distribution tree, in this case , the sending user host can directly use the virtual distribution tree to transmit multicast data packets, and there is no need for the process of establishing a spanning tree on the virtual distribution network. The process is similar and will not be repeated here.

In order to control the sending and receiving of user hosts, each router node on the virtual distribution network can set two permission flags for each virtual neighbor (occupying 1 bit respectively): the permission of the node to receive data packets from the virtual neighbor and the permission of the node to send data packets to the virtual neighbor. Permission for virtual neighbors to send packets. Assume that the goal of multicast transmission control is: user host H4 can send multicast data packets in a two-way transmission mode, and other user hosts are prohibited from sending; user host H2 is not allowed to receive, but other user hosts can receive. The control goal is as follows: Figure 11 shows. In order to achieve the above goals, the authority flags in the distribution tables on routers R1, R3 and R7 can be set, as shown in Figure 12, each subgraph a, b, c is the distribution table of router R1, router R3 and router R7 respectively, where "Acceptable" means that the node can only receive data packets from the virtual neighbor; "Can send" means that the node can only send data packets to the virtual neighbor; The virtual neighbor sends data packets, and "forbidden to send and receive" means that the node cannot receive data packets from the virtual neighbor and cannot send data packets to the virtual neighbor.

In the above-mentioned implementation scheme, the identification of the virtual distribution network is identified by an IP unicast address, and the uniqueness of the entire network assigned by the IP unicast address can ensure the uniqueness of the identification of the virtual distribution network in the IP network, of course , the virtual distribution network can also be identified in other ways, such as using an IP multicast address or even a new identifier, as long as this identification method can ensure that each virtual distribution network is distinguished in the IP network.

For a multicast session S, in addition to establishing the above-mentioned virtual distribution network V0, one or more backup virtual distribution networks can also be established. For example, a virtual distribution network V1 for backup can be established, as shown in Figure 13, the virtual distribution network is composed of four user hosts (H1, H2, H4 and H5) participating in the multicast session S and a router R1 , all user hosts have one and only one virtual neighbor, that is, router R1. The router R1 is also the master node of the virtual distribution network V1. A new virtual network interface is established on the router R1 and a unicast address is assigned to identify the virtual distribution network V1. When the virtual distribution network V0 fails to work, for example, the multicast forwarding function of the router R7 fails, the sending host H1 can select the virtual distribution network V1 to transmit the multicast data packet.

Claims (9)

1, the multi-cast transmission method in a kind of IP network is characterized in that, this method is based on the multi-cast transmission method of virtual distribution networks, comprising: at first, set up a virtual distribution networks for each multicast conversation in IP network; Described virtual distribution networks is formed by connecting by virtual link by a plurality of virtual distribution networks nodes, described a plurality of virtual distribution networks node comprises subscriber's main station and 1 router node with multicast function of all participation multicast conversations at least, described virtual link is meant that the logic that connects virtual distribution networks node transmits passage, is called the other side's empty neighbours mutually by two nodes of virtual link connection; Virtual distribution networks has a unique virtual distribution networks sign, is used for distinguishing a plurality of virtual distribution networks in the IP network; At the part of nodes of this virtual distribution networks or all set up and safeguard a distributing list on the node, described part of nodes comprises the all-router on the virtual distribution networks at least, described distributing list is made up of distribution list item more than 1 or 1, and each distribution list item correspondence wherein a virtual distribution networks and comprised following content at least: virtual distribution networks identifies, empty neighbours' IP address more than 1 or 1; Then, on this virtual distribution networks, send subscriber's main station and adopt broadcast mode that multicast packets is sent to all reception subscriber's main stations.

2, multi-cast transmission method as claimed in claim 1, it is characterized in that, described on virtual distribution networks, sending subscriber's main station employing broadcast mode is diffusion method with methods that multicast packets is sent to all reception subscriber's main stations, specifically comprise: send subscriber's main station and send multicast packets, comprised sending sequence number of this packet in the described multicast packets to its all empty neighbours; Each node on the virtual distribution networks is after receiving multicast packets, judge whether to receive multicast packets from the same sequence number of same transmission subscriber's main station, if receive, then abandon this multicast packets, if do not receive, then this node is transmitted to every other empty neighbours except that the empty neighbours that send this packet with this multicast packets, and all that are sent in the virtual distribution networks up to this multicast packets receive subscriber's main stations.

3, multi-cast transmission method as claimed in claim 1, it is characterized in that, described on virtual distribution networks, sending subscriber's main station adopts broadcast mode that multicast packets is sent to all methods that receive subscriber's main station for generating the tree method, specifically comprise: at first, on this virtual distribution networks, set up a distribution tree that connects all nodes on the virtual distribution networks; The root node of described distribution tree is any one virtual distribution networks node; Form the upstream and downstream relation between two on the described distribution tree adjacent virtual distribution networks nodes, virtual distribution networks node is labeled as the empty neighbours in upstream with the empty neighbours near root node on the distribution tree, will be labeled as the empty neighbours in downstream away from the empty neighbours of root node; Then, on the distribution tree of being set up, send subscriber's main station and adopt one-way transmission mode or two-way load mode to send multicast packets to all reception main frames;

Described one-way transmission mode is: send the root node that subscriber's main station at first sends to multicast packets distribution tree, then from root node, each virtual distribution networks node that receives multicast packets is transmitted to the empty neighbours in its downstream with it, is sent to all reception subscriber's main stations of virtual distribution networks up to this multicast packets;

Described two-way load mode is: send subscriber's main station and multicast packets is directly sent to empty neighbours in upstream and the empty neighbours in all downstreams of oneself, each virtual distribution networks node that receives multicast packets is transmitted to the empty neighbours of other upstream and downstream except the empty neighbours that send this multicast packets on the distribution tree with it, is sent to all reception subscriber's main stations of virtual distribution networks up to this multicast packets.

4, multi-cast transmission method as claimed in claim 3 is characterized in that, also is included in the distribution tree of setting up in this virtual distribution networks more than 1; Each distribution tree has different root nodes; Each distribution tree all has a unique distribution tree sign, is used for distinguishing the different distribution trees on the same virtual distribution networks; Mark empty neighbours in the pairing upstream of each distribution tree and the empty neighbours in downstream on each virtual distribution networks node; Sending subscriber's main station selects wherein one or more distribution trees to transmit multicast packets to all reception subscriber's main stations.

5, multi-cast transmission method as claimed in claim 1, it is characterized in that, described virtual distribution networks constitutes a virtual distribution tree, virtual distribution networks node is the node of this virtual distribution tree, the root node of this virtual distribution tree is any one virtual distribution networks node, and two nodes that virtual link connects on the virtual distribution networks form the empty neighborhood of upstream and downstream on this virtual distribution tree; Sending subscriber's main station on described virtual distribution networks adopts broadcast mode that methods that multicast packets is sent to all reception subscriber's main stations are as follows: the transmission subscriber's main station adopts one-way transmission mode or two-way load mode to send multicast packets to all and receives main frame;

Described one-way transmission mode is: send the root node that subscriber's main station at first sends to multicast packets virtual distribution tree, then from root node, each virtual distribution networks node that receives multicast packets is transmitted to the empty neighbours in its downstream with it, is sent to all reception subscriber's main stations of virtual distribution networks up to this multicast packets;

Described two-way load mode is: send subscriber's main station and multicast packets is directly sent to empty neighbours in upstream and the empty neighbours in all downstreams of oneself, each virtual distribution networks node that receives multicast packets is transmitted to the empty neighbours of other upstream and downstream except the empty neighbours that send this multicast packets on the virtual distribution tree with it, is sent to all reception subscriber's main stations of virtual distribution networks up to this multicast packets.

6, as claim 1,2,3,4 or 5 described multi-cast transmission methods, it is characterized in that, comprise also in the described distribution list item that this node receives the authority of packet from each empty neighbour; In the transport process of multicast packets, each node on the virtual distribution networks will check that earlier it receives the authority of packet from this void neighbours after the multicast packets of receiving from certain empty neighbour, if authority permission, then this packet is transmitted, otherwise, this packet abandoned.

7, as claim 1,2,3,4 or 5 described multi-cast transmission methods, it is characterized in that, comprise also in the described distribution list item that this node sends the authority of packet to each empty neighbour; In the transport process of multicast packets, each node on the virtual distribution networks is before sending to multicast packets certain empty neighbour, check that earlier it sends the authority of packet to this void neighbours, if authority permission, then can send multicast packets to this void neighbours, otherwise, do not send this packet.

As claim 1,2,3,4 or 5 described multi-cast transmission methods, it is characterized in that 8, described virtual distribution networks sign is represented with an ip multicast address, perhaps represents with the IP unicast address of any one node on the virtual distribution networks.

9, as claim 1,2,3,4 or 5 described multi-cast transmission methods, it is characterized in that, also be included in the IP network to each multicast conversation and set up virtual distribution networks more than 1, the node of these virtual distribution networks has included all subscriber's main stations of participating in this multicast conversation, but comprises different router node collection; Sending subscriber's main station selects one or more virtual distribution networks to transmit multicast packets to all reception subscriber's main stations.

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