CN101222414A - Device, system and method for realizing multicast communication - Google Patents

Abstract

The embodiment of the present invention provides a device, system and method for realizing multicast communication. The device includes an identity resolution server; the system includes: a multicast source, an access router, a receiver and an identity resolution server. The method mainly includes: the multicast source acquires and saves the mapping relationship information between EID (end host identifier) and IP addresses of all nodes; constructs and manages a multicast tree according to the EID information of all nodes; the multicast source According to the multicast tree and the IP address information of the nodes, the multicast communication is carried out with the receiver through the relay of the access router. Utilizing the present invention, the intermediate nodes in the network do not need to save the state information of the application layer multicast tree, do not need to maintain the application layer multicast tree, and are only responsible for forwarding the multicast data message, thus effectively reducing the intermediate layers of burden.

Description

Device, system and method for realizing multicast communication

technical field

The present invention relates to the communication field, in particular to a device, system and method for realizing multicast communication.

Background technique

Multicast is a technology that optimizes the use of network bandwidth resources. The use of multicast technology allows data streams to be sent from one or more data sources to multiple destinations. Unnecessary data packet duplication can be avoided, which is beneficial to reduce backbone network traffic, thereby more effectively utilizing network resources.

At present, multicast is mainly divided into two categories: IP multicast and application layer multicast (also called overlay multicast). In the traditional IP multicast model, group management protocols are used to interact between multicast receivers and multicast routers. Group management protocols include: IGMP (group management protocol for IPv4) and MLD (group management protocol for IPv6) . Between the routers, a multicast routing protocol is used to establish, update and maintain a multicast tree, and the router obtains a path for copying and distributing multicast packets based on the multicast tree. The database collected by the group management protocol is used by the multicast routing protocol to determine whether there are multicast receivers on the local subnet, so as to ensure that the multicast receivers receive the requested multicast packets.

Currently, IP multicast service models mainly include two types: ASM (Any Source Multicast) model and SSM (Specific Source Multicast) model. IP multicast has the advantages of high network utilization and can save resources of the sender itself, and is suitable for real-time and unreliable applications. However, IP multicast also has the following problems:

1. The router must save the state for each multicast group, and the scalability is poor;

2. All routers are required to support multicast routing protocols, which is not conducive to promotion and use;

3. Use a unified model to adapt to all applications, and algorithm design is difficult;

4. The management overhead of joining and exiting a multicast group is high.

The basic feature of application layer multicast is to maintain the original simple, unreliable, and unicast forwarding model of the Internet, and realize the multicast forwarding function by the end system. Application layer multicast technology needs to be based on the following prerequisites:

1. The bandwidth and forwarding resources of the network are relatively abundant, and the processing capacity of the server is the main bottleneck;

2. Members of the multicast group can provide resources for forwarding;

3. The application does not have strict requirements on performance, and can tolerate packet loss and large delay.

In the application layer multicast technology, members of a multicast group are connected to each other by building an overlay multicast tree. All multicast functions, such as group member management and packet duplication, are implemented on the terminal. When the application layer multicast protocol organizes various group members together, two topologies are constructed among them: control topology and data topology. Among them, the data topology is a multicast distribution tree, which defines the path of data distribution among group members; the control topology is a mesh structure, and its purpose is to increase the connectivity and robustness among group members.

Application layer multicast has the following advantages: only need to change the end system, easy to implement and promote; easy to optimize for specific applications. However, because the application layer multicast does not consider the routing and data forwarding of the IP layer, its efficiency is lower than that of IP multicast, and its performance such as delay and forwarding rate is lower than that of IP multicast. Currently, application layer multicast is mainly used for real-time multimedia transmission, such as video conferencing systems, media stream distribution systems (such as video broadcasting) and subscription/distribution systems.

In recent years, with the development of wireless technology, more and more people are connected to the Internet through wireless devices, and mobile support has become an inevitable requirement for the development of the Internet. The combination of mobile and multicast will further expand the application scope of mobile and multicast, and provide a wider development space for the application of both. However, the combination of mobile and multicast brings new challenges to both. In a mobile environment, multicast not only needs to manage dynamic multicast group members, establish and maintain a multicast tree, but also needs to solve the problem of dynamic change of group member locations. However, the current multicast protocols used in the Internet generally assume that their group members are static, without considering the situation of dynamic changes in the positions of group members. If every time a group member moves, it is treated as a newly joined group member, which will bring too much overhead to the management of the multicast group and the maintenance of the multicast tree, and increase the burden on the network; Mobile will also cause switching delay, packet loss and other phenomena, which cannot meet real-time multimedia applications.

The traditional TCP/IP protocol is mainly used for communication between fixed nodes. In the traditional Internet architecture based on the TCP/IP protocol stack, the IP address is used not only as the identity of the host, but also as the location of the host. When the IP address of the host changes, the original transmission connection established by the host will be interrupted. The connection needs to be re-established, which is not conducive to supporting the mobility of the host.

At present, there are many schemes, such as HIP (Host Identifier Protocol), etc., which redesign the traditional TCP/IP protocol in order to enable the Internet to support mobility. HIP proposes a mechanism based on the separation of identity and location, which separates the dual functions of the traditional IP address, and the IP address is only used as the location identifier of the host; at the same time, a new name space is introduced: the end host identifier, using the end host identifier The identity of the host. This mechanism of separation of identity and location makes even if the IP address of the node changes, the connection at the transport layer will not be interrupted, and there is no need to re-establish the connection.

An application layer multicast solution in the prior art is: a Bayeux application layer multicast technical solution. The solution is based on the Tapestry routing mechanism. Each node in the network has a globally unique identifier ID, which is independent of the location of the node and has nothing to do with the location of the node. Each node in the network must maintain a neighbor entry. In this neighbor entry, the ID of the neighbor node and the ID of the current node have a certain number of identical bits. When forwarding the data packet, the ID of the nth hop node and the ID of the destination node have at least n bits the same. When an intermediate node forwards data packets, if the ID of the intermediate node and the ID of the destination node have n digits the same, the intermediate node queries its own neighbor entry to see if there is an ID that is n+1 with the ID of the destination node. If there are nodes with the same bit, the intermediate node takes the found node as its next-hop node, and forwards the data packet to the next-hop node at the same time.

In this scheme, a special logical structure is used to map or address multicast nodes. Each multicast session is collectively represented by <session name, UID>, where the session name describes the content of the multicast, and UID represents a special instance of the session. When establishing an overlay multicast tree, the multicast source takes itself as the root node, and each intermediate node establishes a corresponding forwarding table according to the contents of its neighbor entries, and finally forms a network-wide overlay multicast tree. A schematic diagram of a simple Bayeux overlay multicast tree is shown in Figure 1, and the numbers in the nodes in Figure 1 represent the IDs of the nodes.

In the Bayeux overlay multicast tree shown in Figure 1, if the receiver 3360 wishes to access the 7876 multicast group, then 3360 sends a join message to 7876, and the paths that the message passes through are x360, xx60, xxx0, and 7876. After receiving the join message, the multicast source 7876 returns a response message to the receiver 3360 . The multicast source, the receiver 3360, and the intermediate nodes through which the response message passes jointly construct an overlay multicast tree. Due to the asymmetry of the Tapestry routing mechanism, the path through which the receiver sends the join message is not necessarily equal to the path in the overlay multicast tree that is finally formed.

Based on the Tapestry routing mechanism, the Bayeux application layer multicast technology saves the state information of the covered multicast tree on the intermediate node, and uses the Tapestry routing mechanism to forward the message, so that multicast forwarding can be implemented using simple rules, thus Reduced state maintenance overhead and forwarding overhead, avoiding the use of routing protocols.

The disadvantages of the above-mentioned application layer multicast solution in the prior art are:

1: In this scheme, the relationship between nodes in the logical space does not correspond to the relationship in the actual network, that is, the relationship between nodes in the multicast tree does not correspond to the relationship in the actual network, so the relationship obtained from the multicast tree The packet forwarding path is not necessarily the shortest path, causing a large delay in packet forwarding.

2: In this solution, the intermediate node needs to save the state information of the application layer multicast tree and maintain the application layer multicast tree, so the burden on the intermediate node is increased.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a device, system and method for realizing multicast communication, so that the intermediate nodes in the network do not need to save the state information of the application layer multicast tree, and do not need to perform the application layer multicast tree Maintenance is only responsible for forwarding multicast data packets, thereby effectively reducing the burden on the middle layer.

The purpose of the embodiments of the present invention is achieved through the following technical solutions:

An identity resolution server, including:

Mapping relationship storage module: used to save the end host identifier EID and IP address of all nodes and multicast sources, and the mapping relationship information between EID and IP address;

Mapping relationship management module: used to perform at least one operation of adding, updating and deleting the EID and IP address stored in the mapping relationship saving module, and the mapping relationship information between EID and IP address;

Mapping relationship parsing module: used to query the mapping relationship information stored in the mapping relationship saving module according to the parsing request carrying EID information sent by the node, obtain the IP address information corresponding to the EID carried in the parsing request, and use the IP Address information is returned to the node.

A system for realizing multicast communication, comprising:

Multicast source: used to obtain and save the mapping relationship information between the EID and IP address of all nodes; build and manage the multicast tree according to the EID information of all nodes, and pass the interface according to the multicast tree and the IP address information of the nodes Multicast communication between the transit of the incoming router and the nodes;

Access router: Use the Open Shortest Path First OSPF protocol to transmit multicast data packets between the multicast source and receivers;

Receiver: Send a multicast join request message to the multicast source to join the corresponding multicast group; perform multicast communication between the multicast source through the relay of the access router.

A method for implementing multicast communication, comprising:

The multicast source obtains and saves the mapping relationship information between the EID and IP address of all nodes; builds and manages the multicast tree according to the EID information of all nodes;

The multicast source performs multicast communication with the receivers through the relay of the access router according to the multicast tree and the IP address information of the nodes.

As can be seen from the technical solutions provided by the above-mentioned embodiments of the present invention, the embodiments of the present invention represent the identity of the node with EID (end host identifier), and represent the location of the node with the IP address; IRS (identity resolution server) is set to Save, parse and manage the mapping relationship between EID and IP address of nodes. Compared with the prior art, it has the following advantages:

1. The intermediate nodes in the network do not need to save the state information of the application layer multicast tree, nor do they need to maintain the application layer multicast tree, but are only responsible for forwarding the multicast data packets, thus reducing the burden on the intermediate nodes .

2. At the IP layer, routers in the network use OSPF (Shortest Path First Routing Protocol) to select routes and forward multicast data packets according to the IP addresses of source nodes and destination nodes, so that the forwarding path of multicast data packets is the shortest path.

3. The multicast source establishes a multicast tree based on the identity information of the nodes. When the multicast source or receiver moves, there is no need to change the topological relationship of the multicast tree, so that both fixed nodes and mobile nodes are connected in a unified manner. Perform multicast communication.

Description of drawings

Fig. 1 is a simple Bayeux coverage multicast tree schematic diagram;

Fig. 2 is a schematic structural diagram of the IRS described in the embodiment of the present invention;

3 is a schematic diagram of the format of the information stored by the IRS according to the embodiment of the present invention;

4 is a schematic diagram of the format of an identity resolution request message and an identity resolution response message according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a system for realizing multicast communication according to an embodiment of the present invention;

FIG. 6 is a specific flowchart of a method for realizing multicast communication according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of the format of a multicast join request message according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of the format of resource records stored in the multicast group member list according to the embodiment of the present invention;

FIG. 9 is a flow chart for maintaining the multicast tree after the receiver moves according to the embodiment of the present invention;

FIG. 10 is a schematic diagram of the format of an address update message according to an embodiment of the present invention;

FIG. 11 is a flow chart of maintaining the multicast tree after the multicast source moves according to the embodiment of the present invention.

Detailed ways

The embodiment of the present invention provides a device, system and method for realizing multicast communication. The method introduces the concept of EID, uses EID to represent the identity of a node, and uses an IP address to represent the location of a node. Set up the IRS to store, analyze and manage the mapping relationship between the EID and IP address of the node; the multicast source builds the multicast tree according to the identity information of the node.

In the embodiment of the present invention, the EID is used to represent the identity of the node, each node has a globally unique EID, and the IP address is used to represent the location of the node. The EID of each node remains unchanged, while the IP address of the node can be changed dynamically.

The embodiment of the present invention provides an IRS. The IRS is used for storing, resolving and managing the mapping relationship between EIDs and IP addresses of nodes. All nodes in the network know the EIDs and IP addresses of the IRS. The structural representation of the embodiment of IRS is as shown in Figure 2, comprises following modules:

Mapping relationship storage module: used to store EIDs and IP addresses of all nodes (including multicast sources) in the network, and mapping relationship information between EIDs and IP addresses. The mapping relationship storage module can store the above information in the database. The schematic diagram of the format of the information preserved in the mapping relationship preservation module is as shown in Figure 3, and in Figure 3, the number of resource records field refers to the number of (EID, IP) pairs recorded in the IRS; the checksum indicates that the storage content integrity.

Mapping relationship analysis module: used to analyze the mapping relationship between the EID and IP address of the node. When a node needs to resolve the EID, it sends an identity resolution request message carrying the EID information to the IRS, requesting to resolve the EID; when the IRS receives the identity resolution request message, it searches for the mapping relationship information saved by itself, and finds the information corresponding to the EID. The IP address corresponding to the EID, and then returns an identity resolution response message carrying the EID and the corresponding IP address information to the node. A schematic diagram of the format of the above identity resolution request message and identity resolution response message is shown in FIG. 4 . The description of each field in Figure 4 is as follows:

Identification field: set by the client program and returned by the server, the client program uses it to determine whether the response matches the request.

QR field: Indicates the type of message. 0 indicates an identity resolution request message, and 1 indicates an identity resolution response message.

rcode field: Indicates whether an error occurs in the parsing of the EID. Usually, a value of 0 is used to indicate no error, and a value of 1 is used to indicate an error occurs. The general situation of an error is: the specified EID to be parsed does not exist.

Number of queries field: Indicates the number of EIDs requested to be resolved. For the identity resolution response message, the value of this field is 0.

Number of resource records field: indicates the number of resolved IP addresses. For an identity resolution request packet, the value of this field is 0.

Query EID field: Indicates the EID value requested to be parsed, and the size of this field is variable. For the identity resolution response message, the value of this field is 0.

Response field: indicates the IP address information obtained after parsing the EID, and the size of this field is variable. For an identity resolution request packet, the value of this field is 0.

Mapping relationship management module: perform management operations such as adding, updating, and deleting the EIDs and IP addresses of all stored nodes (including multicast sources) and the mapping relationship between EIDs and IP addresses. After the node and the multicast source move, it sends an address update message carrying new IP address information to the IRS. After receiving the address update message, the IRS updates the IP addresses of the node and the multicast source to realize node Dynamic mapping between EID and IP address of multicast source. The mapping relationship management module specifically includes: a node address update module and a multicast source address update module.

Among them, the node address update module: used for updating the address information of the node according to the address update message carrying its latest IP address information sent by the node, the IP address information of the node, and the mapping relationship information between the EID and the IP address of the node to update;

Wherein, the multicast source address update module: used for carrying the address update message carrying its latest IP address information sent by the multicast source, the IP address information of the multicast source, and the EID and The mapping relationship information between IP addresses is updated.

The structural diagram of the system for implementing multicast communication according to the embodiment of the present invention is shown in FIG. 5 , including: a multicast source, a receiver, an access router, and an IRS.

Multicast source: used to manage multicast groups, use the EID of the node to build a multicast tree. The multicast tree only includes multicast sources and receivers, which is a simple end-to-end relationship and does not include intermediate nodes. The multicast source stores a multicast group member list, and the multicast group member list stores the mapping relationship between each receiver's EID and IP address. After the location moves, an address update message is sent to the IRS.

Each multicast group managed by the multicast source has its own identity mark G _EID , and the present invention uses ( _SEID , G _EID ) to represent a multicast group, wherein S _EID is the identity mark of the multicast source, and G _EID is the group The identity of the broadcast group.

Access router: The access router constitutes the middle layer node of the system described in the present invention, and the access router does not need to save the state information of the application layer multicast tree, nor does it need to maintain the application layer multicast tree, but is only responsible for packet forwarding. At the IP layer, the access router uses the traditional unicast protocol OSPF (Open Shortest Path First) to select and transmit multicast data packets, which can ensure that the information transmission path between the multicast source and the receiver is the shortest path.

Receiver: It has the EID and IP address information of the IRS, as well as the EID information of the multicast source and the EID information of the multicast group. Send an identity resolution request message to the IRS, and obtain the IP address information of the multicast source through the resolution of the IRS. Send a multicast join request message to the multicast source, join the corresponding multicast group, and receive the multicast data message sent by the multicast source. After the location moves, an address update message is sent to the IRS.

IRS: used to save, resolve and manage the mapping relationship between EID and IP address of all nodes (including multicast sources) in the network.

The specific flow of the method for realizing multicast communication described in the embodiment of the present invention is shown in Figure 6, including the following steps:

Step 61: After obtaining the EID ( _SEID ) of the multicast source and the EID ( _GEID ) of the multicast group, the receiver can determine whether to join the multicast group and whether to receive the service of the multicast group. If it is determined that the multicast group needs to be joined, the receiver sends an identity resolution request message carrying _SEID information to the IRS, requesting resolution of the _SEID .

Step 62: After receiving the above-mentioned identity resolution request message, the RS searches for the mapping relationship information between the saved EID and the IP address in its own database, finds the IP address corresponding to the above-mentioned _SEID , and then returns the carrying information to the receiver. The identity resolution response message of the found IP address information informs the receiver of the corresponding relationship between the _SEID and its IP address.

Step 63: The receiver saves the correspondence between the received _SEID and its IP address, sends a multicast join request message carrying the multicast source EID and receiver EID to the multicast source, and requests to join the multicast Group. A schematic diagram of the format of the above multicast join request message is shown in FIG. 7 .

In Fig. 7, the type field is 1, which means that the message is a multicast join request message; the packet length field represents the total length of the multicast join request message, represented by the number of bytes; the checksum field is used to detect the message Whether the file is damaged during transmission.

Step 64: After receiving the above-mentioned multicast join request message sent by the receiver, the multicast source records the receiver's EID (R _EID ). Then, the multicast source sends an identity resolution request message carrying _REID information to the IRS, requesting to resolve the _REID .

Step 65: After receiving the above-mentioned identity resolution request message, the IRS searches for the mapping relation information between the EID and the IP address stored in its database, and finds the IP address corresponding to the above-mentioned _REID . Then, an identity resolution response message carrying the found IP address information is returned to the multicast source, and the mapping relationship between the _REID and its corresponding IP address is notified to the multicast source.

Step 66: After the multicast source receives the above-mentioned identity resolution response message sent by the IRS, record the receiver's EID and IP address in the multicast group member list. A schematic diagram of the format of resource records stored in the multicast group member list is shown in FIG. 8 . In FIG. 8 , the resource record number field indicates the number of (EID, IP) pairs of receivers recorded in the multicast group member list; the checksum field indicates the integrity of the stored content.

Step 67: During actual multicast communication, the multicast source sends a multicast data packet to the receiver through the router according to the receiver's EID and IP address recorded in the multicast group member list. The header of the multicast data message should contain the multicast group EID field, so that the receiver can confirm that the data message is a multicast data message, and also make the receiver confirm which multicast group the data message belongs to. message.

The sending mechanism of multicast data packets is the same as that of ordinary data packets, and no additional processing is required. The routers in the network use the OSPF routing protocol to select and forward the above data packets.

Step 68: If the receiver wants to leave the above-mentioned multicast group and no longer receive the multicast data message of the above-mentioned multicast group, the receiver sends an identity resolution request message carrying the _SEID information to the IRS, requesting to resolve the _SEID ; IRS After receiving the identity resolution request message, search for the IP address corresponding to the _SEID . Then, send an identity resolution response message carrying the found IP address to the receiver, and tell the receiver the mapping relationship between the _SEID and its corresponding IP address.

Step 69: After obtaining the IP address of the multicast source, the receiver sends a multicast leave message carrying the EID of the multicast source and the EID of the receiver to the multicast source. A schematic diagram of the format of the multicast leave message is shown in FIG. 7 above. In Fig. 7, the type field is 2, which means that the message is a multicast leaving message; the packet length field indicates the total length of the multicast leaving message, expressed in bytes; the checksum field is used to detect whether the message is in the Whether it was damaged during transmission.

Step 610: After the multicast source receives the multicast leave message, obtain the receiver EID information carried in it, delete the corresponding receiver EID and its IP address in the multicast group member list, and no longer give the receiver to send multicast data packets.

When the receiver moves, the multicast tree in the above multicast tree needs to be maintained accordingly. The specific maintenance process flow is shown in Figure 9, including the following steps:

Step 91 , the receiver sends an address update message carrying its new IP address to the IRS and the multicast source, and informs the IRS and the multicast source of its new address. The format of the above address update message is shown in FIG. 10 . Among them, the packet length field indicates the total length of the address update message, expressed in bytes; the checksum field is used to detect whether the message is damaged during transmission.

Step 92, after the IRS receives the above-mentioned address update message, it updates the recipient's IP address information stored in its database, replaces the recipient's original IP address with the recipient's new IP address, and realizes the connection between the recipient's EID and the IP address in the database. Dynamic mapping between.

After the multicast source receives the above address update message, it updates the multicast group member list saved by itself, and replaces the original IP address of the receiver with the new IP address of the receiver, so as to realize the EID and IP address of the receiver in the multicast group member list. Dynamic mapping between.

Step 93: The multicast source uses the new IP address of the receiver to send a multicast data packet to the receiver.

When the multicast source moves, the multicast tree in the above multicast tree needs to be maintained accordingly. The specific maintenance process is shown in Figure 11, including the following steps:

Step 111 , the multicast source sends the above address update message carrying its new IP address to the IRS, and tells the IRS its new address.

Step 112, after the IRS receives the address update message, it updates the multicast source IP address information stored in its database, replaces the original IP address of the multicast source with the new IP address of the multicast source, and realizes the multicast source EID in the database. and dynamic mapping between IP addresses.

Step 113, the multicast source uses its new IP address to send multicast data packets to the members of the multicast group.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (12)

1. An identity resolution server, characterized in that, comprising: Mapping relationship storage module: used to save the end host identifier EID and IP address of all nodes and multicast sources, and the mapping relationship information between EID and IP address; Mapping relationship management module: used to perform at least one operation of adding, updating and deleting the EID and IP address stored in the mapping relationship saving module, and the mapping relationship information between EID and IP address; Mapping relationship parsing module: used to query the mapping relationship information stored in the mapping relationship saving module according to the parsing request carrying EID information sent by the node, obtain the IP address information corresponding to the EID carried in the parsing request, and use the IP Address information is returned to the node. 2. The identity resolution server according to claim 1, wherein the mapping relationship management module specifically includes: Node address update module: used to update the IP address information of the node and the mapping relationship information between the EID and IP address of the node according to the address update message sent by the node carrying its latest IP address information ; Multicast source address update module: used for address update message carrying its latest IP address information sent by the multicast source, the IP address information of the multicast source, and the EID and IP address of the multicast source Update the mapping relationship information between them. 3. A system for realizing multicast communication, characterized in that, comprising: Multicast source: used to obtain and save the mapping relationship information between the EID and IP address of all nodes; build and manage the multicast tree according to the EID information of all nodes, and pass the interface according to the multicast tree and the IP address information of the nodes Multicast communication between the transit of the incoming router and the nodes; Access router: Use the Open Shortest Path First OSPF protocol to transmit multicast data packets between the multicast source and receivers; Receiver: Send a multicast join request message to the multicast source to join the corresponding multicast group; perform multicast communication between the multicast source through the relay of the access router. 4. the system realizing multicast communication according to claim 3, is characterized in that, described system also comprises: Identity resolution server: used to save, resolve and manage the EIDs and IP addresses of all nodes and multicast sources in the network, as well as the mapping relationship information between EIDs and IP addresses. 5. A method for realizing multicast communication, comprising: The multicast source obtains and saves the mapping relationship information between the EID and IP address of all nodes; builds and manages the multicast tree according to the EID information of all nodes; The multicast source performs multicast communication with the receivers through the relay of the access router according to the multicast tree and the IP address information of the nodes. 6. The method for realizing multicast communication according to claim 5, wherein the method specifically comprises: The globally unique EID is used to represent the identity of the node, and the IP address is used to represent the location of the node. The EID of each node remains unchanged, and its IP address changes dynamically when the node moves. 7. The method for realizing multicast communication according to claim 5, wherein the method specifically comprises: The access router uses the OSPF protocol to transfer the multicast data message between the multicast source and the receiver. 8. The method for realizing multicast communication according to claim 5, 6 or 7, wherein the method specifically comprises: Set up an identity resolution server, and use the identity resolution server to save, resolve and manage the EIDs and IP addresses of all nodes and multicast sources in the network, as well as the mapping relationship information between EIDs and IP addresses. 9. The method for realizing multicast communication according to claim 8, wherein the method specifically comprises: The receiver sends an identity resolution request message carrying the multicast source EID information to the identity resolution server, and the identity resolution server searches for the mapping relationship information between the EID and the IP address it stores according to the multicast source EID information, and finds The IP address corresponding to the multicast source EID information returns an identity resolution response message carrying the found IP address information to the receiver. 10. The method for realizing multicast communication according to claim 9, characterized in that, the method specifically comprises: According to the obtained IP address information of the multicast source, the receiver sends a multicast join request message carrying the multicast source EID and receiver EID to the multicast source. After receiving the multicast join request message, the multicast source sends The identity resolution server sends an identity resolution request message carrying the recipient's EID information; After the identity resolution server receives the identity resolution request message, it finds the IP address corresponding to the receiver's EID, and returns an identity resolution response message carrying the found IP address information to the multicast source; The multicast source saves the received mapping relationship between the receiver's EID and the IP address, and according to the multicast tree and the receiver's IP address, through the transit of the access router and the Communication of multicast data packets between receivers. 11. The method for realizing multicast communication according to claim 8, characterized in that, the method specifically comprises: When the receiver needs to leave the multicast group, the receiver sends a multicast leave message carrying the multicast source EID and the receiver EID to the multicast source; the multicast source receives the After the multicast leave message, the saved EID and IP address of the receiver are deleted, and the multicast data message is no longer sent to the receiver. 12. the method for realizing multicast communication according to claim 8, is characterized in that, described method also comprises: When the multicast source or the receiver moves in place, it sends an address update message carrying its latest IP address to the identity resolution server. After receiving the address update message, the identity resolution server sends the multicast The IP address of the source or receiver is updated.

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