WO2005015837A1

WO2005015837A1 - A method and system for implementing the transmission of the data packet

Info

Publication number: WO2005015837A1
Application number: PCT/CN2004/000911
Authority: WO
Inventors: Qiang Xie; Yufa Han; Yupeng Xiong; Yong Luo
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2003-08-07
Filing date: 2004-08-06
Publication date: 2005-02-17

Abstract

This invention discloses a method and system of implementing the transmission of the data packet, this method includes the steps of: first set up a transmitting bus connected to the send port and the receive port, and set the cells which are transmitted over the transmitting bus, the send port then converts the data packets which are to be transmitted, and send the cells to the transmitting bus, and transmit the data packet corresponding to the cell according to the information carried by the cell. At the same time, this invention also discloses a system for implementing the transmission of the data packet. This invention implements the unicast, multicast of the packet transmission between the network and the user, in particularly, when the network needs to transmit a number of multiple data packet, saves the network resource, improves the transmitting performance of the network by converting the multicasting data packets into cells and transmitting over the transmitting bus to reduce the cose of the communication as the communicating device supports the same number of users.

Description

Method and system for implementing data message transmission

Technical field

The present invention relates to the field of network communication technology, and more particularly, to a method for implementing data transmission and a system based on which data transmission is implemented. Background of the invention

In the current network communication system, data message transmission methods include: unicast and multicast. Among them, multicast includes multicast and broadcast. Unicast is a point-to-point transmission method; multicast is a transmission method based on one-point transmission and specific multi-point reception; and broadcast is a transmission method based on one-point transmission and unspecified multi-point reception.

As multimedia services such as streaming media, video conferencing, and video-on-demand on the Internet become an important part of information transmission in network communication systems, more and more multicast data packets are transmitted on the network. It becomes more and more important in network communication.

Most of the existing network communication technologies are based on unicast and broadcast transmission methods. Therefore, unicast and broadcast transmission methods can be considered to realize the transmission of multicast data packets. The following is a brief description of the method of implementing multicast data message transmission using unicast and broadcast in the Internet.

When unicast is used to implement multicast, since the unicast transmission method is unicast transmission and single reception, this transmission method requires the server to copy a corresponding message for each user requesting to send a message, and The message is sent to the user. Therefore, if the transmission of multicast data messages is implemented in unicast mode, when multiple users request the same message to be sent, the server will copy a copy of the same content for each user's request. The message is sent to each user who requests the message through the network node. Obviously, a large amount of system resources will be occupied on the network due to repeated transmission of packets with the same content. In addition, this processing method requires the server in the system to repeatedly copy and send packets with the same content, which will cause a bottleneck in data transmission and waste service. Server resources and cause server processing power to decrease.

When the broadcast method is used to implement multicast, since the transmission mode of the broadcast is unicast transmission and unspecified multipoint reception, this transmission method requires that when a user of one node in the network sends a message, all other user nodes must Receive, so if the multicast data transmission is implemented in a broadcast mode, as long as one user requests a data message, the server in the system will send the data message to all users, and all users in the network To receive the data message. In fact, not all users need these data packets, so this processing method will cause unnecessary packets to be transmitted on the network, which will cause a bottleneck in data transmission and waste network resources. In addition, the current broadcast mode is implemented by copying data packets. Therefore, the system may need to copy many data packets. Obviously, this will waste network resources.

It can be known from the above description that the implementation of multicast transmission based on unicast or broadcast transmission has great limitations. Of course, unicast transmission is not suitable for broadcast, and broadcast transmission cannot be used for unicast.

For multicast, since multimedia services have become an important part of information transmission in network communication systems, the transmission of multicast data packets has become a problem that must be solved. In other words, in a network communication system where multimedia services such as streaming media, video conferencing, or video on demand are carried out, if it is desired to simply and efficiently implement data packet transmission, it is necessary to solve multicast data packets in the network well. Transmission.

The following is a detailed description of the characteristics of multicast and the method of implementing multicast data message transmission in current network communication systems.

The information transmission method adopted by multicast is single-point transmission and specific multi-point reception. This transmission method requires the server to send data packets to specific multiple receivers in the network. Therefore, when one or more users under the same network node request the same data message, the multicast server should theoretically only need to copy one message and send it to the network node. Users receive messages according to their needs. At present, the existing method for solving the transmission of multicast data messages can be implemented based on an Ethernet switching module, which is the above-mentioned network node, and the network connected to the Ethernet switching module can be an IP network. The module The specific internal connection relationship is shown in Figure 1. In FIG. 1, users 1 to 4 are connected to the switching module through a user interface in the switching module, and a multicast server is connected to the switching module through a network interface in the switching module. Based on the structure shown in FIG. 1, the multicast server sends a corresponding multicast data packet to the switching module according to the user's application, and there is only one packet; the switching module receives the multicast sent by the multicast server through the network interface. Data packets and store them in their own shared buffers; assuming that user 1 and user 4 need the multicast data messages stored in the shared buffer, the switching module copies the corresponding multicast data messages to User interface 1 and user interface 4; user 1 receives a multicast data message from user interface 1, and user 4 receives a multicast data message from user interface 4. Through the above process, the transmission of the multicast data message is completed.

The number of users connected to the switching module may increase according to needs. Therefore, the burden of copying and transmitting the switching module will increase accordingly. In this case, a cascade switching module needs to be set up. The specific connection mode based on the cascade switch module is shown in Figure 2. In FIG. 2, the switching module 1 to the switching module 5 constitute a multicast device, and the multicast server is connected to the multicast device through a network interface in the multicast device; the switching module 2 to the switching module 5 are respectively connected to the switching module 1 and exchanged Module 1 uses its cascaded switching modules 2 to 5 as its own users. Users 1, 2 are connected to switch module 2, user 3 is connected to switch module 3, user 4 is connected to switch module 4, and users 5, 6 are connected to switch module 5.

Based on the connection shown in FIG. 2, the multicast server sends corresponding multicast data packets to the multicast device according to the application data of the multicast messages of users 1 to 6, and the multicast device receives the multicast server through the network interface. Send a multicast data message, and store the data message in a shared buffer of the switching module 1. If user 1 and user 4 need the data message, switch module 1 copies and sends the data message stored in its shared buffer to the switch module. Block 2 and switching module 4; switching module 2 and switching module 4 receive the multicast data message sent by switching module 1, and store the data message in its own shared buffer; after that, switching module 2 stores itself This data message stored in the shared buffer is sent to user 1, and the switching module 4 sends this data message stored in its own shared buffer to user 4. Through the above process, the transmission of the multicast data message is completed.

For the above two solutions for transmitting multicast data packets, the following problems exist:

1) Since each multicast data message occupies a share of bandwidth, the more multicast data messages the system needs to transmit, the more data messages the switching module needs to replicate, which will inevitably reduce the switching module. Processing capacity, which limits the transmission performance of the network;

2) Many data packets transmitted in the network are duplicate data packets, that is, a large part of the data packets transmitted in the network have the same content, which will inevitably waste network resources;

3) the switching module needs to copy the multicast data message stored in its own shared buffer to the corresponding cascade switching module or user, which requires higher processing performance of the switching module;

4) For a scheme for implementing multicast transmission through cascading, if there are many users connected to a cascade switching module, and these users apply for many multicast data packets, the data transmission between the switching modules Bandwidth requirements are very high. Taking switching module 2 in FIG. 2 as an example, the more multicast data packets that need to be forwarded in this switching module, the more bandwidth is occupied between switching module 1 and switching module 2. Therefore, With a certain bandwidth, there will be a transmission bottleneck between switch module 1 and the cascaded switch module.

5) The above problems of bandwidth and processing capacity of the switching module limit the number of users supported by the communication equipment. If it is to be guaranteed that it can support the same number of users, the cost of the communication equipment needs to be increased significantly, thereby making the cost of the network equipment too high.

If the above network is an asynchronous transmission mode (ATM) network, the switching device may be an asynchronous transmission mode digital subscriber line access multiplexer (ATM DSLAM), which is within the ATM DSLAM. The department implements multicast replication through point-to-multipoint connections. As shown in FIG. 3, each network server, that is, multicast source 1, must establish a virtual connection (VC) to connect to the ATM DSLAM. Due to the use of Internet VC, the transmission of multicast data will cause the cells to be out of order due to the interleaving of multicast cells and Internet cells. Therefore, in addition to establishing a VC for Internet access on each user's remote terminal device (RTU), And also establish a dedicated multicast VC ".

The ATM DSLAM also needs to be configured with a multicast forwarding table, which specifies the correspondence between the user multicast VC "and the multicast source VC. After receiving the multicast data from the multicast source VC, the ATM DSLAM uses the multicast forwarding table. Copy the multicast data to the specified user multicast VC ".

For this solution, because the multicast forwarding table in ATM DSLAM needs to use VC's VPI / VCI to identify different multicast sources, each multicast source must be an ATM node, so it cannot implement a VC connection bearer. Multiple multicast groups. On the one hand, this causes waste of connection resources and equipment, and P reduces the flexibility and simplicity of networking. On the other hand, if new multicast sources are to be added, data configuration must be increased, so the scalability of the network is poor. .

Multicast streams and unicast service streams on the network side need to pass through different VCs to the ATM DSLAM. This is because unicast streams and multicast streams are processed differently on DSLAM. Unicast streams are only cross-connected on DSLAM. Multicast streams are based on virtual path identifiers and virtual channel identifiers. The (VPI / VCI) identifier is used for multicast forwarding. Therefore, the unicast stream and the multicast stream cannot use the same VC for downlink.

For the user RTU, at least two VCs need to be configured, which makes the terminal equipment complicated. Specifically, the RTU configuration requirements should be as simple and fixed as possible. However, to prevent the unicast data and the multicast data from being out of order, therefore, when the DSLAM is downlinked to the RTU, it needs to be carried on two VCs. Unicast data and multicast data bring some complexity to the configuration of RTU.

In addition, ATM DSLAM internally implements multicast replication through point-to-multipoint connections, which is not efficient, and multicast data is replicated within DSLAM, adding DSLAM equipment With the load of T2004 / 000911, too much multicast data can easily become a performance bottleneck.

In addition, ATM DSLAM is fixedly forwarded according to the multicast forwarding table, which prevents users from dynamically joining or leaving a multicast group. If a user needs to receive data of a certain multicast group, he must apply to the operator for service provisioning. After the operator opens this application for the user, even if the user closes the multicast terminal software on the terminal device, that is, when the user no longer needs to receive the multicast data, the ATM DSLAM will still send the multicast data to the user RTU. In addition, the multicast forwarding table is managed and configured by the network administrator, which results in inflexible service development, increases the workload of maintenance, and consumes the user's bandwidth when the user does not need it.

In summary, the existing multicast transmission method cannot fully meet the needs of multicast transmission. In addition, there is currently no transmission method that can simultaneously meet the needs of unicast, multicast, and broadcast. Summary of the invention

In view of this, the main purpose of the present invention is to provide a method for implementing data message transmission, so as to realize the transmission of data messages including unicast, multicast, and broadcast, and not to transmit multicast datagrams. Text and waste network resources.

Another object of the present invention is to provide a system for implementing data message transmission.

A method for implementing data packet transmission according to the present invention includes the following steps: a. The transmitting end converts a data packet to be sent into a cell and sends it;

b. The receiving end receives the cell, and transmits the data message corresponding to the cell according to the information carried by the cell.

Further, a transmission bus connecting the transmitting end and the receiving end may be set, the cell is a cell set to be transmitted on the transmission bus, and the cell has a corresponding VPI / VCI, and the cell may be an ATM cell ;

Then in step a, the transmitting end transmits the converted cell to the transmission bus: in step b, the receiving end receives the cell from the transmission bus. The data message includes: a unicast data message, a multicast data message, and a broadcast data message. A system for implementing data message transmission according to the present invention includes:

Network-side interface device: converts a data message sent from the network into a cell, and sends the cell and the cell identifier to the transmission bus together;

User-side interface device: Receives a cell sent by a network-side interface device to a transmission bus, and then sends the cell to a corresponding user terminal according to a cell identifier of the cell.

The user-side interface device in the system can further convert the data message sent by the user terminal into a cell, and send it to the transmission bus together with the unicast cell identifier;

The network-side interface device may further receive a cell sent by the user-side interface device to the transmission bus, and send a data packet corresponding to the cell to the network.

In the solution of the present invention, the user terminal sends the request data message of the user terminal to the network side through the transmission bus, and records related information of the request data message; the network side sends the unicast data message and multicast data message to be sent in the network After the text is converted into a cell, it is transmitted to the transmission bus; each user side connected to the transmission bus receives the cell on the transmission bus, and sends the cell to the corresponding user terminal according to the cell identifier and the requirements of the user terminal, so that In the present invention, when multiple users need the same cell, the cell does not need to be copied multiple times to transmit the cell to the corresponding user, so that the system does not transmit when a multicast data message is transmitted. The bottleneck and the package efficiently implement the transmission of multicast data messages, save network resources, and improve the transmission performance of network communication equipment, thereby reducing the cost of communication equipment when the communication equipment supports the same number of users. Alas.

In addition, the solution of the present invention also provides a processing procedure for data packet transmission of the ATM network. Since multicast packet transmission does not need to be transmitted through a multicast forwarding table, multiple multicast group data on the network side can be placed on one VC. As a result, multiple multicast streams can be provided by one multicast server, which effectively saves uplink connection resources and equipment investment, and also facilitates simplified networking. Network-side multicast data streams and unicast data streams can also be placed on a VC This saves uplink connection resources and reduces the maintenance workload of operator maintenance personnel. The user-side multicast data stream and unicast data stream can be carried on a VC, which can avoid the need to reconfigure a large number of user terminals when adding multicast services, which greatly reduces the workload of maintenance personnel. The ATM DSLAM internally implements multicasting via the ATM transmission bus, which saves system resources and improves efficiency. Moreover, each user port receives multicast data on the bus according to its own multicast group. It does not require the CPU to perform cell replication and saves Bandwidth resources inside the device.

In addition, the solution of the present invention also enables users to dynamically join or leave multicast groups as needed, and the system can control users to join multicast groups according to pre-set permissions. After users leave, the system no longer sends multicasts to them Data, reducing the bandwidth occupation of user ports and improving forwarding efficiency. Brief description of the drawings

FIG. 1 is a schematic diagram of implementing a multicast data message transmission using a switching module in the prior art; FIG. 2 is a schematic diagram of implementing a multicast data message transmission using a cascade of switching modules in the prior art;

3 is a schematic diagram of multiple multicast, wide area network, bandwidth access, and user RTU systems based on ATM DSLAM equipment in the prior art;

4 is a first system for implementing data message transmission in an embodiment of the present invention;

5 is a second system for implementing data message transmission according to an embodiment of the present invention;

FIG. 6 is a third system for implementing data packet transmission according to an embodiment of the present invention; FIG.

7 is a system for implementing data packet transmission based on IP DSLAM in an embodiment of the present invention; FIG. 8 is a schematic diagram of protocol processing in the system shown in FIG. 7;

FIG. 9 is a diagram illustrating a system for transmitting data packets based on an ATM DSLAM in an embodiment of the present invention. 10 is a flowchart of processing a downlink transmission data message in the system shown in FIG. 9; FIG. 11 is a flowchart of processing a transmission data message upstream in the system shown in FIG. 9; FIG. 12 is an ATM DSLAM in the system shown in FIG. Structure diagram of the equipment after adding relevant modules;

FIG. 13 is a processing flowchart of a user joining a multicast group in the system shown in FIG. 9. Mode of Carrying Out the Invention

The core idea of the present invention is: setting a transmission bus between a transmitting end and a receiving end, and setting a cell for transmission on the transmission bus, and the transmitting end converts a data message to be transmitted in the network into the cell, And sending the cell to the transmission bus; the receiving end receives the cell from the transmission bus, and restores the cell to a data message according to the information carried by the cell. Based on the core idea of the present invention, information transmission between a network server connected to the network side and a user terminal connected to the user side in the network can be realized.

The transmission bus used in the present invention may specifically adopt a bus based on the ATM transmission bus standard. A bus based on the ATM transmission bus standard can support a maximum of 32 transmission bus interface units at the same time, that is, the sum of the user side and the network side to which the transmission bus is connected is 32. Currently, buses based on the ATM transmission bus standard can provide shared switching capacity above IGbps.

Because the characteristic of the transmission bus is to use one bus to complete the exchange of ATM cells between the transmission bus interface units of different boards, and there can be multiple user sides connected to the transmission bus, and each user connected to the transmission bus The transmission bus interface unit on the side and the network side provides a richer cell scheduling mechanism such as three-level routing lookup. Therefore, ATM cells on the transmission bus can be implemented in each user-side and network-side transmission bus interface unit. Exchange.

The invention can realize the transmission of data messages on the transmission bus through ATM cells. ATM is a high-speed, low-latency multiplexing switching technology. ATM uses cells and provides limited error detection operations to make the network fast enough to support multi-megabit transmission rates. Therefore, the present invention utilizes the transmission characteristics of ATM cells, and converts unicast data packets and multicast data packets into ATM cells, and receives and sends them through a transmission bus. The user side and the network side connected to the transmission bus The ATM cell is then restored into a data message, and the data message is transmitted according to the destination address carried by the data message, thereby completing the transmission of the data message between the network side and the user side. In this way, when transmitting multicast data packets including multicast and broadcast, data packets can be transmitted between the network side and the user side without requiring multiple replications, thereby achieving the datagram simply and efficiently. Text transmission.

When the network is an IP network, when the network side sends data packets to the user terminal, the network side first converts unicast data packets and multicast data packets transmitted by the network server into cells, and passes them through The transmission bus is sent to the user side; the user side receives the cell from the transmission bus, and converts the cell into a corresponding data message according to the information carried by the cell, and then transmits the data to the corresponding data message. User terminal. The request data message sent from the user terminal to the network side is first converted by the user side into the corresponding cell and sent to the network side through the transmission bus; the network side receives the cell from the transmission bus, It converts it into a request data message according to the information carried by the cell, and then transmits it to the corresponding network server.

The specific method for realizing data message transmission in the present invention is implemented through the following processes:

Establish a transmission bus between the network side and the user side, and set the ATM cells for transmission on the transmission bus; establish the network side corresponding to the VC corresponding to the unicast cell identity in each user side, and the corresponding one to the multicast cell identity. VC, and the VC corresponding to the broadcast cell identifier; establishing the correspondence between the media access control (MAC) address and the VPI / VCI; and establishing the correspondence between the VPI / VCI and the cell identifier.

There can be two directions for transmitting data packets. The upstream direction refers to the direction from the user side to the network. Side, the downward direction refers to the network side to the user side.

First, the data packet transmission in the upstream direction will be described.

When the user side receives the request data message transmitted from the user terminal, the user side converts the message into a cell according to the source MAC address in the request data message. This is because different types of data packets have different MAC addresses, so cell conversion can be performed based on the MAC address. Different types of cells have different VPI VCL after conversion

The types of data messages that the user terminal requests the IP network to send to it include unicast data messages, multicast data messages, and broadcast data messages. If the user terminal needs the IP network to send a multicast data message to itself, it needs to record the relevant information of the request data message. The relevant information includes the address information of the user terminal and the multicast group number of the multicast data message requested to be sent. . The related information may be specifically recorded on the user side or on the network side, so that the user side can forward multicast data packets according to the information. Of course, if recorded on the network side, the network side needs to send the information To the user side.

The user side adds a unicast cell identifier and the characteristic information of the destination to the cell according to the VPI / VCI of the converted cell, and passes the cell, the unicast cell identifier, and the characteristic information of the destination to the unicast message together. The VC corresponding to the meta ID is sent to the transmission bus. The characteristic information of the destination includes a port number and a slot number, and the characteristic information of the destination may also be set in a unicast cell identifier. Because the request data message sent by the user terminal can only be unicast data, the cell identifier added to the cell by the user side is the unicast cell identifier.

All ports connected to the transmission bus receive cells on the transmission bus, and determine whether to receive the cell based on the cell identifier and the characteristic information of the destination.

Since the converted cell identifier of the request data packet is a unicast cell identifier, and the characteristic information of the destination end of the cell is the characteristic information of the network side, the network side restores the received cell into a request data packet, and according to The destination MAC address of the request data message is sent to the IP network. Because the feature information of each user side and the feature information of the destination end of the cell are different, Therefore, each user side discards the received cells.

The following describes the data transmission in the downlink direction.

The network side converts the data packet into a cell according to the source MAC address of the data packet to be sent from the IP network. The network side adds the corresponding cell identifier and the characteristic information of the destination according to the VPI / VCI of the cell, and sends the cell, the cell identifier, and the characteristic information of the destination to the transmission bus together. The data messages to be sent may be unicast data messages, multicast data messages, and broadcast data messages.

When sending a cell and related information to a transmission bus, if the data packet is a unicast data packet, the network side adds a cell identifier for the cell according to the source MAC address of the unicast data packet as unicast. Cell ID. In addition, the characteristic information of the destination end corresponding to the destination MAC address of the unicast data message is also added to the cell. Then, the converted cells, the characteristic information of the destination end, and the unicast cell identifier are sent to the transmission bus through the VC corresponding to the unicast cell identifier. Similarly, the feature information of the destination can be set in the unicast cell identifier.

If the data message is a multicast data message, the network side adds a multicast cell identifier to the cell according to the source MAC address of the multicast data message, and increases the multicast group number of the multicast data message. Then, the cell, the multicast cell identifier, and the multicast group number are sent to the transmission bus through the VC corresponding to the multicast cell identifier. Here, the multicast group number may be set in the multicast cell identifier.

If the data message is a broadcast data message, the network side may add a broadcast cell identifier to the cell according to the source MAC address of the broadcast message, and correspond the cell and the broadcast cell identifier together through the broadcast cell identifier. VC is sent to the transmission bus.

Of course, there may be multiple types of data packets to be sent by the network side. In this case, the network side may determine to allow the currently sent cells according to a predetermined algorithm and a predetermined priority to avoid transmission of the cells. Data congestion occurred during the process. For example, multicast cells can be set Has the highest priority, and the unicast cell has the second highest priority. In this way, the unicast cell, the multicast cell, and the broadcast cell can be sent according to the priority.

Each user side connected to the transmission bus receives the cells on the transmission bus, and determines to transmit the cells to the corresponding user terminal according to the cell identifier and the needs of the user terminal.

Specifically, if the cell identifier received by the user side is a unicast cell identifier, each user side determines a user terminal that needs to receive the cell according to the characteristic information of the destination end of the cell, and restores the cell to a unicast datagram. And send it to the user terminal.

If the cell identifier received by the user side is a multicast cell identifier, each user side determines a user terminal that needs to receive the cell according to the recorded request information, restores the cell to a multicast data packet, and sends the packet to the User terminal. If the request information is recorded on the network side, the network side should send the request information to the user side.

If the cell identifier received by the user terminal is a broadcast cell identifier, each user side restores the cell to a broadcast data message and sends it to all user terminals connected to itself.

Of course, no matter what kind of cell is received by each user side, as long as each user side determines that all users connected to itself do not need the cell according to the characteristic information of the destination end of the cell, the user side discards the cell.

When the network is an ATM network, the data packets sent by the network side can only be unicast data packets and multicast data packets. There are no broadcast data packets. Therefore, only these two types of packets need to be addressed. Text for processing.

Specifically, in the downlink direction, that is, when the network side sends a data message to the user terminal, the data message sent is an ATM cell, and the ATM cell may include both a unicast data packet and a multicast data ^ ^: In the text, the network side needs to form the ATM cell into a corresponding Ethernet frame, and tag the Ethernet frame with a VLAN ID according to the connection information, and then perform unicast and multicast distribution on the Ethernet frame. Multicast frames are transmitted separately. The connection information refers to pre-configured exchange information on the DSLAM device, and is mainly the VPI / VCI on the ADSL port side. T N2004 / 000911 Correspondence with Ethernet VLAN ID, etc.

For a unicast frame, the Ethernet frame needs to be converted into a corresponding ATM message according to the destination MAC address or VLAN ID of the unicast frame, and according to the correspondence between the MAC address or VLAN and the user VC identifier, that is, VPI / VIC. The ATM cell is then sent to the transmission bus.

For a multicast frame, the multicast frame needs to be converted into an ATM cell according to the correspondence between the multicast group and the multicast VC identifier, and then the ATM cell is sent to the transmission bus.

The user side receives the multicast ATM cells and unicast ATM cells belonging to the port according to the preset multicast reception table and unicast reception table, and multiplexes the received cells in the original cell order, and Send the multiplexed ATM cell to the RTU through the user VC;

The RTU recovers the received ATM cells into an Ethernet frame, and then sends the Ethernet frame to the user terminal.

In the uplink direction, that is, when the user side sends data to the network side, the data packet sent by the user terminal to the user side is converted into an ATM cell by the RTU, and is carried in the user VC and sent to the user side. After the ATM cell, directly add the unicast cell identifier and the characteristic information of the destination to the cell according to the VPI / VCI of the user VC, and pass the unicast message together with the cell, the unicast cell identifier, and the characteristic information of the destination. The VC corresponding to the meta ID is sent to the transmission bus.

After receiving a cell on the transmission bus, the network side determines whether the destination characteristic information of the cell meets its own receiving conditions. If it does, the ATM cell is converted to the Ethernet of the corresponding VLAN according to the VPI / VCI of the cell. Network frame, and record the correspondence between the source MAC address of the data packet and the user VC identifier, and then convert the Ethernet frame into an ATM cell, and send the ATM cell according to the correspondence between the VLAN and the network-side VC Go to the corresponding network-side VC.

The above has described the specific process of data packet transmission. For the data transmission system, there are at least four implementation manners, and the four implementation manners are described in detail below with reference to the accompanying drawings.

Figure 4 shows the first system for data packet transmission. This system enables the network to send data packets to the user.

The transmission bus interface unit in this system leads the transmission bus interface on the backplane side, and is connected to the transmission bus through the derived transmission bus interface. The ATM universal test and operation physical layer interface is led out on the transmission bus interface unicast board ( UTOPIA), and is connected to the user equipment interface unit through the UTOPIA.

By configuring different working modes for the transmission bus interface unit, various network equipment interface units or user equipment interface units can be flexibly connected to the transmission bus interface unit through UTOPIA, so that the network side and the user side can complete the transmission and reception of ATM cells.

Multiple transmission bus interface units can be connected to the transmission bus. Each interface unit has a unique identifier, and this identifier can be the port address of each interface unit. Because the transmission bus interface unit has a priority scheduling function, the cells that need to be currently sent to the transmission bus can be determined through a predetermined algorithm and priority.

The user-side transmission bus interface unit is connected to the user equipment interface unit, and the network-side transmission bus interface unit is connected to the network equipment interface unit. The user equipment interface unit has multiple slots, each slot has a slot number, and each slot number can correspond to multiple user terminals.

In FIG. 4, three transmission bus interface units 400, 410, and 420 are connected to the transmission bus, and are respectively connected to the network equipment interface unit 430 and the user equipment interface units 440 and 450. The transmission bus interface unit 400 and the network device interface unit 430 constitute a network-side interface device; the transmission bus interface unit 410 and the user equipment interface unit 440 constitute a user-side interface device, and the transmission bus interface unit 420 and the user equipment interface unit 450 constitute a user-side Interface equipment.

When the network device interface unit 430 receives a unicast data message to be transmitted, After the unicast data packet is converted into a cell, it is transmitted to the transmission bus interface unit 400 through the dedicated VC of the unicast cell; the transmission bus interface unit 400 adds a unicast cell identifier and the cell according to the cell's VCI and VPI. Specific information of the destination of the unicast cell. The specific information is the port number and slot number of the board at the destination, and then the unicast cell, the unicast cell identifier, and the unicast port number of the destination of the unicast cell. The slot numbers are sent to the transmission bus through the VC corresponding to the unicast cell identifier. Each transmission bus interface unit 410 and 420 connected to the transmission bus receives the cell at the same time, determines that the cell is a unicast cell according to the unicast cell identifier of the cell, and determines whether the port number of the destination end of the cell is the same as that of the cell. Their own port addresses are the same. If they are the same, they are transmitted according to the slot number of the cell, and the user equipment interface unit sends them to the corresponding user terminal device according to the VPI and VCI of the cell; if they are not the same, then discard the Cell. In this embodiment, the slot number belongs to the user equipment interface unit 440, that is, the transmission bus interface unit 410 can determine that the destination port number of the cell is the same as its own port address, and then according to the slot of the cell The cell is transmitted to the user equipment interface unit 440, and the user equipment interface unit 440 converts the cell into a data message, and sends the converted data message to the corresponding user terminal according to the VP CI of the cell. device. For the transmission bus interface unit 420, it is determined that the destination port number of the cell is different from its own port address, and therefore the cell is discarded. In this way, unicast cells are transmitted between transmission bus interface units on the transmission bus.

When the network device interface unit 430 receives the multicast data message to be transmitted, the multicast data message is converted and transmitted to the transmission bus interface unit 400 through the dedicated VC of the multicast cell; the transmission bus interface unit 400 according to The VCI / VPI of a cell adds a multicast cell identifier and a multicast group number to the cell, and sends the cell, the multicast cell identifier, and the multicast group number to the VC corresponding to the multicast cell identifier to the VC. On the transmission bus. Each transmission bus interface unit 410 and 420 connected to the transmission bus simultaneously interfaces the cell, determines that the cell is a multicast cell based on the cell's multicast cell identifier, and according to the recorded user request multicast data message Request letter Information and the multicast group number of the cell to determine whether the user terminal connected to itself needs the cell of the multicast group number. If the user terminal connected to the transmission bus interface unit 410 needs this cell, the transmission bus interface unit 410 Transmit it to the corresponding user equipment interface unit 440, the user equipment interface unit 440 converts the cell into a corresponding data message, and transmits the converted data message to the corresponding data message according to the VPI / VCI of the cell User terminal. If none of the user terminals connected to the transmission bus interface unit 420 need this cell, the transmission bus interface unit 420 discards the multicast cell. Thus, the transmission of multicast data between the transmission bus interface units on the transmission bus is realized.

When the network device interface unit 430 receives the broadcast data message to be transmitted, the broadcast data message is converted into a cell, and then transmitted to the transmission bus interface unit 400 through the dedicated VC of the broadcast cell; the transmission bus interface unit 400 according to The VCI / VPI of the cell adds a broadcast cell identifier to the cell, and sends the cell along with the broadcast cell identifier to the transmission bus through the VPI corresponding to the broadcast cell identifier. Each transmission bus interface unit 410 and 420 connected to the transmission bus receives the cell at the same time, determines that the cell is a broadcast cell according to the broadcast cell identifier of the cell, and then transmits the cell to users connected to itself. A device interface unit, and the user equipment interface units 440 and 450 convert the broadcast cell into a corresponding broadcast data message, and transmit the broadcast data message to all user terminal devices connected to itself. Thus, the transmission of broadcast cells between the transmission bus interface units on the transmission bus is realized.

In the above system, all transmission bus interface sheep connected to the transmission bus have an arbitration function, so as to implement data packet forwarding according to the arbitration result.

Figure 5 shows the second system for data packet transmission.

The system includes a network-side interface device 500 and a user-side interface device 510. There is only one network-side interface device on the transmission bus, and there can be multiple user-side interface devices.

The network-side interface device 500 includes a transmission bus interface unit 501, a data message processing unit 502, and an interface conversion unit 503. The transmission bus interface unit 501 has a priority scheduling function for determining a cell identifier corresponding to a cell transmitted by the data message processing unit 502, and transmitting the cell and the cell identifier to the transmission according to a predetermined algorithm and priority. A bus; the interface unit further receives a cell and a cell identifier on the transmission bus, determines a cell to be transmitted to the data packet processing unit 502 according to the cell identifier, and performs transmission.

A data message processing unit 502, configured to convert a data message transmitted by the IP network through the interface conversion unit 403 into a cell, and transmit it to a transmission bus interface unit 501 with an arbitration function together with its corresponding cell identifier; the processing The unit also restores the cells transmitted by the transmission bus interface unit 501 into a request data message, and transmits them to the IP network through the interface conversion unit 503.

The interface conversion unit 503 is configured to provide an interface between the network-side interface device and the IP network. The interface conversion unit may be a Fast Ethernet (FE) optical port, an FE electrical port, or a G-bit Ethernet optical port.

The user-side interface device 510 includes a transmission bus interface unit 511, a cell bearing unit 512, and a user terminal access unit 513. The transmission bus interface unit can be connected to multiple cell bearer units at the same time, and the cell bearer unit can also be connected to multiple user terminal access units, respectively.

The transmission bus interface unit 511 is configured to transmit the cells and the cell identifiers transmitted by the cell carrying unit 512 to the transmission bus; receive the cells on the transmission bus; and transmit the information according to the cell identifier and user requirements. The cells are transmitted to the corresponding cell carrying unit 512.

The cell carrying unit 512 is configured to transmit the ATM cells transmitted from the user terminal access unit 513 to the transmission bus interface unit 511; and carry the ATM cells transmitted from the transmission bus interface unit 511 in a predetermined frame. The VPI / VCI of the cell is transmitted to the corresponding user terminal access unit 513. The cell bearing unit may be an asymmetric digital subscriber line chip, a high-speed digital subscriber line chip, or a high-bit digital subscriber line chip. A user terminal access unit 513, configured to convert a request data message transmitted from the user terminal into a cell, and send the converted cell in a predetermined frame to the cell carrying unit 512; the access unit will also The cells carried in the predetermined frame transmitted by the cell carrying unit 512 are restored into corresponding data messages and transmitted to the user terminal.

Figure 6 shows a third system that implements data message transmission.

The difference between this system and the first system is that the user terminal in the system shown in FIG. 6 can send the ATM cell corresponding to the request data message to the transmission bus through the user side, and the network side obtains it according to the cell sent by the transmission bus. A corresponding request data message, and sending the message to the IP network according to the destination MAC address in the request data message. After receiving the request data message, the IP network returns a corresponding data message to the user terminal.

Specifically, three transmission bus interface units 600, 610, and 620 are connected to the transmission bus in FIG. 6, and they are connected to user equipment interface units 630, 640, and 650, respectively; the transmission bus interface unit 600 and data message processing Unit 630 constitutes a network-side interface device; transmission bus interface unit 610 and user equipment interface unit 640 constitute a user-side interface device; transmission bus interface unit 620 and user equipment interface unit 650 constitute a user-side interface device.

The transmission bus interface unit 600 is a transmission bus interface unit with a priority scheduling function on the network side, and the transmission bus interface unit 610 and the transmission bus interface unit 620 are transmission user interface unit on the user side.

The data packet processing unit 630 is a network equipment interface unit on the network side, and the user equipment interface unit 640 and the user equipment interface unit 650 are user equipment interface units on the user side, respectively.

The IP network 660 is connected to the data packet processing unit 630, and the user terminal 641, the user terminal 642, the user terminal 643, the user terminal 644, and the user terminal 645 are connected to the user equipment interface unit 540 and the user equipment interface unit 650, respectively.

Establish a VC for the user-side interface device and the network-side interface device. This virtual connection includes unicast. The VC corresponding to the cell identity, the VC corresponding to the multicast cell identity, and the broadcast cell identity to establish the correspondence between the VPI, the VCI, and the cell identity.

The cell identity includes a unicast cell identity, a multicast cell identity, and a broadcast cell identity. It is set that the user terminal 641 needs the IP network 660 to send a data message to it.

The user terminal 641 transmits the request data message to the user equipment interface unit 640, and the user equipment interface unit 640 converts the request data message into a cell and transmits the request data message to the transmission bus interface unit 610 through a permanent virtual connection corresponding to the unicast cell identifier.

After receiving the cell transmitted by the user equipment interface unit 640, the transmission bus interface unit 610 adds a unicast cell identifier and a port number and data of the transmission bus interface unit 600 to the slot number of the text processing unit 630, and sends the The unit and unicast cell identifier are sent to the transmission bus together with the port number and slot number. If the information carried by the received cell is a request for the IP network 660 to send a multicast data packet to it, the request information for requesting the IP network to send a multicast data packet also needs to be recorded; the request information includes the group of the requested multicast data packet Broadcast group number and user terminal address information. The request information for a multicast data message can be recorded in any component device of the system that implements the data message transmission.

Each transmission bus interface unit connected to the transmission bus receives the cells on the transmission bus at the same time. After receiving the cells, the transmission bus interface unit 600 determines according to the cell identifier that the received cells are unicast cells, multicast cells, Still broadcasting cells. If the cell identifier is a unicast cell identifier, it is determined according to the port number that it should receive the cell, and is transmitted to the data packet processing unit 620 through the permanent virtual connection corresponding to the unicast cell identifier according to the slot number; other transmissions The bus interface unit 620 discards the received cell by judging that the port number of the cell is not consistent with its own port number.

After receiving the unicast cell transmitted by the transmission bus interface unit 600, the data packet processing unit 620 restores the unicast cell to a request data packet, and according to the media access control of the request data packet The address is transmitted to the IP network 660.

The data message processing unit 630 receives a data message transmitted from the IP network 660.

The data packets transmitted by the IP network 660 include unicast data packets, multicast data packets, and broadcast data packets. ,

Since the MAC addresses of the broadcast data message, the multicast data message, and the unicast data message are different, the data message processing unit 630 can identify the type of the data message by judging the MAC address of the received data message.

The IP network 660 transmits a data message corresponding to the request data message to the data message processing unit 630 according to the request data message of the user terminal 641.

If the IP network ⁶⁶⁰ needs to send a broadcast data packet, the data packet transmission to the broadcast data packet processing unit 630.

The data packet processing unit 630 converts the received data packet into a corresponding cell according to the MAC address of the received data packet. If the data packet is a unicast data packet, the cell identifies the corresponding permanent virtual connection through the unicast cell. Transmitted to the transmission bus interface unit 600; if the data message is multicast data ^ = Gen text, it is transmitted to the transmission bus interface unit 600 through the permanent virtual connection corresponding to the multicast cell identifier; if the data message is a broadcast data message Then, the permanent virtual connection corresponding to the broadcast cell identifier is transmitted to the transmission bus interface unit 600.

The transmission bus interface unit 600 receives a cell transmitted by the data packet processing unit 630 from the permanent virtual connection corresponding to the unicast cell identifier, adds a unicast cell identifier to the cell, and determines the cell according to the VPI and VCI of the cell. Its corresponding destination port number and slot number. If this unicast data message is a unicast data message sent by the IP network requested by user terminal 641, add the port number and user equipment of the transmission bus interface unit 610 to the cell The slot number of the interface unit 640; and sends the cell, the unicast cell identifier, the port number, and the slot number to the transmission bus together.

The transmission bus interface unit 600 receives a cell transmitted by the data packet processing unit 630 from the permanent virtual connection corresponding to the multicast cell identifier, and adds a multicast cell identifier and a multicast Group number; and send the cell with the multicast cell identifier and the multicast group number to the transmission bus. The transmission bus interface unit 600 receives a cell transmitted by the data message processing unit 630 from the permanent virtual connection corresponding to the broadcast cell identifier, adds a broadcast cell identifier to it, and sends the cell and the broadcast cell identifier to the transmission together. bus.

The transmission bus interface unit 600 is a transmission bus interface unit with an arbitration function. When there are multiple cells converted from data packets that need to be sent, the transmission bus interface unit 600 may determine which transmission is allowed according to a predetermined algorithm and a predetermined priority. Cell.

Each transmission bus interface unit 610 and 620 receives a cell on the transmission bus.

After receiving the cells on the transmission bus, the transmission bus interface unit 610 judges whether the received cells are unicast cells, multicast cells, or broadcast cells based on the cell identification.

If the cell identifier of the cell received by the transmission bus interface unit 610 is a unicast cell identifier, then it is determined according to the port number of the cell whether it is the same as its own port number, and if it is the same, the unicast cell is passed according to the slot number. Identifies the corresponding permanent virtual connection and transmits it to the corresponding slot in the user equipment interface unit 640. The user equipment interface unit 640 restores the cells transmitted by the transmission bus interface unit 610 to a unicast data packet, and according to the unicast data packet The destination MAC address of the text transmits the unicast data ^ ^{: the} text to the user terminal 641. If not, the received cells are discarded. The transmission bus interface unit 620 also processes the received cells according to the above method.

If the cell identifier of the cell received by the transmission bus interface unit 610 is a multicast cell identifier, transmitting the cell to the corresponding slot of the user equipment interface unit 640 according to the recorded request information of the requested multicast data message, The user equipment interface unit 640 restores the cells transmitted by the transmission bus interface unit 610 to a multicast data message, and transmits the cells to the corresponding user according to the recorded request information. The other transmission bus interface unit 620 transmits the received cell to the corresponding user through the recorded request information of the request multicast data message.

If the cell identifier of the cell received by the transmission bus interface unit 610 is a broadcast cell identifier, the cell is transmitted to each slot of the user equipment interface unit 640, and the user equipment interface unit 640 restores the cells transmitted by the transmission bus interface unit 610 into broadcast data messages, and transmits them to all user terminals connected to them. The transmission bus interface unit 620 also transmits the cells received from the transmission bus to all user terminals connected to it according to the method described above.

Figure 7 shows a fourth system for data packet transmission. This system is based on IP interface digital subscriber line access multiplexing equipment (IP DSLAM).

DSLAM is mainly composed of two service boards. These two service boards are a network interface board and a user interface board. The main role of the network interface board is to provide a network-side interface for the DSLAM to connect the DSLAM equipment with the user terminal access unit (CPE). The user interface board and the user terminal access unit together form the user-side interface equipment in the DSLAM.

Specifically, in FIG. 7, the network interface board 700 in the DSLAM includes a transmission bus interface unit 701, a data message processing unit 702, and a LANSWITCH chip 703. The network interface board 700 is a network-side interface device, and the transmission bus interface unit 701 is a transmission bus interface unit with an arbitration function on the network side. The data packet processing unit 702 and the LANSWITCH chip 703 constitute the network device interface unit of the present invention.

The user interface board 710 in the DSLAM includes a transmission bus interface unit 711, an ADSL chip 712, and an ADSL chip 713. ADSL chip 711 k CPE 730 is connected and forms a user equipment interface unit; ADSL chip 712 is connected with CPE 740 and CPE 750 and forms a user equipment interface unit. The user interface board 610 and the CPE 730, CPE 740, and CPE 750 together form a user-side interface device.

The IP network 720 is connected to the LANSWITCH chip 703, and the user terminals 731, 741, and 751 are connected to the user terminal access units CPE 730, CPE 740, and CPE 750, respectively.

After that, it is necessary to establish a VC for each CPE and the network interface board 700. The VC includes a VC corresponding to a unicast cell identifier, a VC corresponding to a multicast cell identifier, and a VC corresponding to a broadcast cell identifier. And establish the correspondence between VPI / VCI and cell identity. The cell identity includes a unicast cell identity, a multicast cell identity, and a broadcast cell identity. In the system corresponding to FIG. 7, data communication is performed between the IP network and the user terminal through a DSLAM, and a protocol processing process thereof is shown in FIG. 8.

In Figure 8, the user terminal sends a data packet to the IP network in the uplink direction, and the protocol processing method in the uplink direction is:

1) The IP network data message sent by the user terminal is processed by the computer's protocol stack, encapsulated into an Ethernet frame, and then sent to the CPE;

2) After receiving the Ethernet frame, the CPE divides the data of the IP network into standard ATM cells according to the 1483B / AAL5 protocol, and then carries the ATM cells in the ADSL frame and sends it to the user interface board. ;

3) The user interface board recovers ATM cells from the ADSL frame, and sends the ATM cells to the network interface board through the transmission bus;

4) The network interface board composes the received ATM cells into an Ethernet frame according to the 1483B / AAL5 protocol, and sends the Ethernet frame to the IP network. '

The data packet sent by the IP network to the user terminal is in the downlink direction. The protocol processing process in the downlink direction is opposite to the uplink direction, so it will not be described again.

The following describes the data packet transmission process based on the system shown in FIG. 7 in combination with the above protocol processing process.

It is set that the user terminal 731 needs the IP network 720 to send a data message to the user, then the user terminal 731 transmits a request data message to the CPE 730, and the CPE 730 converts the request data message into a cell and the cell The bearer carried in the ADSL frame is transmitted to the ADSL chip 712 through the VC corresponding to the unicast cell identifier; the ADSL chip 712 transmits the cell carried in the ADSL frame to the transmission bus interface unit 711 through the VC corresponding to the unicast cell identifier. Similarly, if the request data message is to request the IP network 720 to send a multicast data message to it, the DSLAM needs to record the request information of the multicast data message, that is, the multicast group number and user of the multicast data message. Address information of the terminal 731. The request information can be recorded in DSLAM In any of its constituent units.

The ADSL chip 712 transmits the received cell to the transmission bus interface unit 711, and the transmission bus interface unit 711 adds a unicast cell identifier, the port number of the transmission bus interface unit 711, and the data packet processing unit 730 to the cell. The slot number is sent to the transmission bus through the VC corresponding to the unicast cell together with the unicast cell identifier, the port number, and the slot number.

Each transmission bus interface unit connected to the transmission bus receives a cell on the transmission bus at the same time. After receiving the cell, the transmission bus interface unit 701 determines that the cell is a unicast cell according to the unicast cell identifier. According to the port number carried by the cell, it is determined that the local port should receive the cell, so the VC corresponding to the unicast cell identifier is transmitted to the data packet processing unit 702 according to the slot number. Of course, other transmission bus interface units connected to the transmission bus discard the cell according to the port number carried by the cell and its own port number.

After receiving the unicast cell transmitted from the transmission bus interface unit 701, the data packet processing unit 702 restores the cell to a request data packet, and according to the request data packet MAC address, sends the request through the LANSWITCH chip 703 The data is transmitted to the IP network 720.

The foregoing has described in detail the process by which a user terminal sends a request data packet to an IP network, and the following describes the process of returning a data packet by the IP network accordingly.

The IP network 720 sends a data packet to the user terminal 731, which is specifically transmitted to the data packet processing unit 702 through the LANSWITCH chip 703. The data packets transmitted by the IP network 720 may be unicast data packets, multicast data packets, and broadcast data packets. Since the MAC addresses of the unicast data message, the multicast data message, and the broadcast data message are different, the data message processing unit 702 can identify the type of the data message by determining the MAC address of the received data message.

Therefore, the IP network 720 transmits the data message corresponding to the request data message of the user terminal 731 to the data message processing unit 702 through the LANSWITCH chip 703. Data message The processing unit 702 converts the received data message into a cell according to the MAC address. Specifically, if the data message is a unicast data message, the cell should be a unicast cell and transmitted to the transmission bus interface unit 701 through the VC corresponding to the unicast cell identifier; if it is a multicast Data message, the cell should be a multicast cell, and transmitted to the transmission bus interface unit 701 through the VC corresponding to the multicast cell identifier; if it is a broadcast data message, the cell should be a broadcast cell And transmit the VC corresponding to the broadcast cell identifier to the transmission bus interface unit 701.

The transmission bus interface unit 701 adds a unicast cell identifier to a cell transmitted from the VC corresponding to the unicast cell identifier, and determines the port number and slot number of the corresponding transmission bus interface unit 711 according to the VPI VCI of the cell, and The port number and slot number are added to the cell, and the cell is sent to the transmission bus through the VC corresponding to the unicast cell together with the unicast cell identifier and the port number slot number.

The transmission bus interface unit 701 adds a multicast cell identifier and a multicast group number to a cell transmitted from the VC corresponding to the multicast cell identifier, and passes the cell, the multicast cell identifier, and the multicast group number together through the group. The VC corresponding to the broadcast cell identifier is sent to the transmission bus.

The transmission bus interface unit 701 adds a broadcast cell identifier to a cell transmitted from the VC corresponding to the broadcast cell identifier, and sends the cell and the broadcast cell identifier to the transmission bus through the VC corresponding to the broadcast cell identifier.

A transmission bus interface unit 711 connected to the transmission bus receives a cell on the transmission bus. Of course, other transmission bus interface units connected to the transmission bus also receive the cell.

After each transmission bus interface unit receives the cell, it judges which cell is the received cell according to the cell identifier. After determining the type of the cell, it is determined whether the interface unit receives the cell or discards the cell according to the related information of the cell.

If it is determined that the cell is a unicast cell, the transmission bus interface unit 711 determines that the port number of the cell is the same as its own port number, and then uses the VC corresponding to the unicast cell identifier to identify the cell. The data is transmitted to the ADSL chip 712 corresponding to the slot number in the cell, and the ADSL chip 712 carries the cell in an ADSL frame, and transmits it to the CPE 730 through the VC corresponding to the unicast cell identifier. The CPE 730 restores the cells in the received ADSL frame to a unicast data message, and transmits it to the user 731 according to the destination MAC address of the unicast data message. Other transmission bus interface units connected to the transmission bus discard the cell by judging that the port number of the cell is not consistent with its own port number.

If it is determined that the cell is a multicast cell, the transmission bus interface unit 711 determines that the user is a user to which the interface unit belongs according to the user address information in the recorded request information of the requested multicast data message, and therefore the The VC corresponding to the cell identification transmits the cell to the ADSL chip 712. The ADSL chip 712 carries it in an ADSL frame and transmits it to the CPE 730 through the VC corresponding to the multicast cell identifier. The CPE 730 restores the cells in the received ADSL frame to a multicast data message, and transmits it to the user terminal 731 according to the destination MAC address of the multicast data message. If the user terminal 741 also requested the multicast data message, the transmission bus interface unit 711 uses the user address information in the recorded request information of the requested multicast data message, and identifies the corresponding VC through the multicast cell. The cell is transmitted to the ADSL chip 713 to which the user terminal 741 belongs. The ADSL chip 713 carries the cell in an ADSL frame, and transmits the frame to the CPE 740 through the VC corresponding to the multicast cell identifier. The CPE 740 restores the cells in the received ADSL frame to a multicast data message, and transmits it to the user terminal 741 according to the destination MAC address of the multicast data message. If other transmission bus interface units determine that the user address in the request message does not belong to this interface unit, the cell is discarded.

If the transmission bus interface unit 711 determines that the cell is a broadcast cell according to the broadcast cell identifier, the VC corresponding to the broadcast cell identifier is transmitted to the ADSL chips 712 and 713, and the ADSL chips 712 and 713 carry the cell In the ADSL frame, the ADSL frame is transmitted to the CPEs 730, 740, and 750 through the corresponding VC of the broadcast cell identifier. CEP 730, 740 and 750 restore the cells in the ADSL frame to a broadcast data message, and transmit the broadcast data message to the user terminals 731, 741, and 751 according to the destination MAC address of the broadcast data message, respectively. Other transmission bus interface units also transmit the broadcast data message to the corresponding users in the same way.

In addition, based on the system shown in FIG. 7, dynamic joining and leaving of user terminals in multicast can also be implemented. Of course, this requires the addition of a main control module connected to the transmission bus. Specifically, the user terminal may send a data packet requesting to join a certain multicast group to the user side. After receiving the request data packet, the user side converts the request data packet into an ATM cell and sends it to the ATM cell. Transmission bus; the network side receives the ATM cell from the transmission bus, and obtains a request data message corresponding to the ATM cell, and then records the VC identifier of the user and the multicast group to be joined according to the request data message In the user table, the main control module is requested to authenticate the authority of the user through the message channel. After passing the right, the main control module determines whether there is a multicast VC for the multicast group. If it exists, it directly The user port is added to the multicast VC; otherwise, a multicast VC is established, and the user port is added to the multicast VC. Among them, a protocol processing module may be added to the system shown in FIG. 7, the ATM cell is converted into a request data message by the protocol processing module, and an authentication request is sent to the main control module.

Figure 9 shows a system for data packet transmission for ATM networks, which is based on ATM DSLAM. 9 is different from FIG. 7 in that the network interface board 900 includes a transmission bus interface unit 901, a unicast message processing unit 903, a multicast message processing unit 902, and a protocol conversion module 904. The RTU 930 is connected to the ADSL chip 912 in the user interface board 910, and the RTU 940 and 950 are connected to the ADSL chip 913. The ADSL chip completes the functions of user ADSL line adaptation, access, and convergence of multicast VC and unicast VC.

For data flow, there is no multicast data flow in the uplink direction, that is, the direction that the user side sends to the network side, and there may be unicast data flow in the downlink direction, that is, the direction that the network side sends to the user side. There may be multicast data streams. Data flow in the uplink and downlink directions The development process is explained separately.

In addition, one end of the network-side VC in FIG. 9 is terminated at the BAS device of the upper layer network, and one end is terminated at the protocol processing module, and the AVC network, the DSLAM uplink interface, and the ATM space bus are interposed in the middle. As in the prior art, multiple pieces are provided. Generally, there are multiple pieces of user VCs. One end is terminated on each RTU, and the other end is terminated on the protocol processing module. The user RTU, ADSL interface board, and ATM space bus are interposed.

First, the downlink forwarding process will be described. The processing in the downstream direction is shown in Figure 10. After entering the ATM DSLAM, the ATM cells carried on the network-side VC are first converted by the protocol conversion module from ATM to IP, and the cells are composed into Ethernet frames, and the Ethernet is based on the correspondence between the network-side VC and the VLAN. The network frame is marked with the corresponding VLAN ID, and then the Ethernet frame is unicasted and multicasted. Because the destination MAC address of the unicast frame is different from the destination MAC address of the multicast frame, the unicast can be achieved by the destination MAC address. For the distribution of multicast and multicast, the unicast frame enters the unicast message processing unit 903 in FIG. 9, and the multicast frame enters the multicast message processing unit 902 in FIG. 9.

The multicast forwarding module converts a multicast Ethernet frame into an ATM cell according to the corresponding relationship between the multicast group (1,2) and the multicast VC (VC1, VC2), and adds a multicast group number and an ATM cell to the ATM cell. The multicast cell identification, and the transmission bus interface unit 801 sends the ATM cell to the ATM bus through the multicast VC.

The unicast forwarding module converts the Ethernet frame into an ATM cell corresponding to the user VC according to the destination MAC address or VLAN of the unicast Ethernet frame. A cell identifier and destination characteristic information are added to the element, and are transmitted to the bus by the transmission bus interface unit 901 through a unicast VC.

The user-side transmission bus interface unit 911 receives the ATM cell on the transmission bus, and transmits the ATM cell to the ADSL chip. Specifically, the transmission bus interface unit 911 Determine whether the receiving conditions are met according to the feature information of the destination and the unicast / multicast identifier carried by the cell. If so, remove the unicast / multicast identifier carried in the cell, strip the feature information of the destination, and The feature information of the destination sends the cell to the corresponding ADSL chip.

The ADSL chip receives the group of speech belonging to the port according to the set multicast receiving table, and receives the unicast cells belonging to the user VC on the port according to the set unicast receiving table. The elements are multiplexed together to the user VC in the original cell order, so that a user VC can simultaneously transmit unicast cells and multicast cells. It should be pointed out that when an Ethernet frame is carried on an ATM, the cells cannot be out of order. Before the cells divided by an Ethernet frame are transmitted, the cells of other frames cannot be transmitted on the line. For example, a multicast Ethernet frame in an Ethernet frame is divided into four cells eight, B, C, and D, and a unicast Ethernet frame in the Ethernet frame is divided into four 1, 2, 3, and 4 Cells are sent by the sender in the order of ABCD1234. After the Ethernet frame reaches the receiver through multiple intermediate exchanges, the order of the cells cannot be changed.

After receiving the ATM cell sent by the ADSL chip, the RTU recovers the cell into an Ethernet frame and sends it to a user terminal such as a user computer or a set-top box.

By adopting the above method, multicast can not be completed through point-to-multipoint replication, but the internal ATM bus is used to implement multicast. Each user port receives the multicast data on the bus according to the multicast group in which it is located, without the need for the CPU to perform cell replication, which also saves the bandwidth occupied by the device. Because multiple multicast group data on the network side are carried on a VC, multiple multicast streams can be provided by one multicast server, which can effectively save uplink connection resources and equipment investment, and is also beneficial to networking. simplify. In addition, multiple user VCs can converge to one network-side VC, and the network-side VC can carry both unicast data packets and multicast data packets, which reduces maintenance costs and saves network resources.

The processing in the uplink direction is shown in Figure 11. Specifically, the Ethernet frame sent by the user terminal is decomposed into ATM cells by the RTU and sent to the ADSL chip through the user VC. The ADSL chip sends the ATM cell to the user-side transmission bus interface unit. After receiving the ATM cell, the transmission bus interface unit directly adds a unicast cell identifier to the ATM cell according to the VPI VCI of the user VC. And the characteristic information of the destination, and send the cell, the unicast cell identifier, and the characteristic information of the destination to the transmission bus together.

The transmission bus interface unit on the network side determines that the received ATM cell is the cell it should receive according to the characteristic information of the destination end of the cell, and then sends the ATM cell to the unicast message processing module and the unicast message processing module. Convert the ATM cell into an Ethernet frame according to the cell's VPI / VCI, record the correspondence between the source MAC address and the user's VC identifier, and then send the Ethernet frame to the protocol conversion module. The protocol conversion module then uses the VLAN and The corresponding relationship of the network VC converts the Ethernet frame into ATM cells, and sends the ATM cells to the network-side VC, and the network-side VC sends the ATM cells to the ATM network. Of course, if the user VC corresponds to the network VC, the unicast message processing module may not perform Ethernet frame conversion on the ATM cell and learn the source MAC address. Instead, the unicast message processing module may perform the mapping based on the correspondence between the user VC and the network VC Send the ATM cell directly to the network-side VC.

Similarly, the transmission bus interface unit connected to the transmission bus on the network side has a priority scheduling function, and implements cell transmission according to the arbitration function.

In addition, the data multiplexing in the upstream channel is jointly completed by the ATM backplane bus and the bus interface chip. There are multiple bus interface chips on the bus, and there is only one arbiter at the same time. It needs to be set. When each interface chip connected to the transmission bus needs to send data to the transmission bus, it must obtain the token given by the arbiter; the token can be handed over after a complete frame of data is sent. This ensures that the services of multiple ADSL interface boards are aggregated into the strict framing in the protocol processing module, and no cell disorder occurs. The point between the protocol processing module and the uplink interface board is a point-to-point channel, and there is no problem of multiplexing multiple data streams.

The multiplexing method of sending data on different ports of the same ADSL interface board is still statistically complex. use. The bus interface chip sends the cells of each ADSL port in a round-robin manner. Each port sends a complete frame before sending data for the next port. This ensures that when an ADSL interface board is sent to the bus, it is also sent in frames, and no cell disorder occurs.

It can be seen from the above that ATM DSLAM internally implements multicasting through the ATM space bus, which saves system resources and improves efficiency. Multicast is not completed through point-to-multipoint replication, but instead uses the internal ATM space bus to implement multicast. Each user port receives the multicast data on the bus according to the multicast group in which it is located. It does not require the CPU to perform cell replication, and saves Bandwidth occupied by the device.

Based on the structure shown in Figure 9, on the network side, multiple multicast group data can be carried on a VC. In this way, multiple multicast streams can be provided by a multicast server to effectively save uplink connections. Investment in resources and equipment is also conducive to simplification of networking; network-side multicast data streams and unicast data streams can also be carried on a VC to save uplink connection resources and reduce the maintenance workload of operator maintenance personnel. On the user terminal side, the multicast data stream and unicast data stream can be carried on one VC, which is of great significance for simplifying the configuration of the terminal. The unicast data and multicast data on the terminal side are carried on one VC, which can avoid the increase of When starting a multicast service, a large number of user terminals need to be reconfigured, which can also greatly reduce the workload of maintenance personnel.

In addition, the network interface board shown in FIG. 9 can also add a protocol processing module, and add a single board as a master control module on the transmission bus.

The main control module provides functions such as authentication of user multicast rights, management of user multicast channels, management of multicast users, data configuration, and provision of uplink interfaces.

The protocol processing module performs functions such as protocol conversion between ATM and Ethernet, capture of IGMP application messages, IGMP querier, and IGMP PROXY. If a protocol processing module is set, the module can also implement multicast and unicast data. Of the diversion. Among them, the IGMP request is a module implemented using high-speed logic and works at the bottom. It mainly captures the message according to the format of the IGMP application message and reports it to the high-level software. IGMP querier is a high-level software implementation A function is to periodically send a general group query to all ADSL users to determine the user's multicast group joining status. In addition, when receiving an IGMP leave message from the user, send a specific group query to confirm the multicast Whether there are other users of the group. The IGMP PROXY module is also a function implemented by high-level software. It mainly performs proxy services for user requests and leave messages reported to the multicast router, and responds to general group queries and specific group queries sent by the multicast router on behalf of ADSL users. The main purpose is It is to reduce the traffic impact on the multicast router and improve the multicast efficiency.

The ATM DSLAM equipment after adding the main control module and protocol processing module can be set in the form shown in Figure 12.

Based on the above settings, users connected to ATM DSLAM devices can also dynamically join or leave multicast groups as needed, and after users leave, ATM DSLAM no longer sends multicast data to the user port.

Specifically, the process for a user to join a multicast group is shown in Figure 13, and the specific process is as follows: After the user opens a multicast application, the computer sends a message requesting to join a multicast group, and the request message is The RTU is decomposed into ATM cells and exchanged to the network-side protocol processing module through the corresponding user VC. The protocol processing module forms the ATM cells into an Ethernet frame, that is, according to the protocol carried on the ATM by the Ethernet frame RFC1483B, restore the frame of 1483B into an Ethernet frame; the underlying hardware logic recognizes this message according to the standard IGMP protocol, and captures it to the software of the protocol processing module. The software uses the request message to identify the user VC ID and the user request The joined multicast group is recorded in the user table, and at the same time, a high-level message is sent to the main control module through the message channel, requesting the authorization of the user. After the main control module passes the authentication, it sends a response to the protocol processing module. Establish a multicast VC connection for this multicast group, send a message to notify the ADSL interface board, and then add the user port To the multicast VC in.

There are two types of processing for users leaving a multicast group. One is provided by the protocol processing module. T N2004 / 000911

The function of the IGMP querier sends a multicast general query to all ADSL users through the user VC at a certain interval. If a user does not send a response message for a long time, the user is considered to have left the multicast group. The other is that when a user computer supporting the IGMP V2 protocol leaves a multicast group, it sends a leave multicast group message to the upper-layer network. After capturing the message, the protocol processing module determines that the user has left a specific multicast group. Broadcast group.

After determining that a user leaves a multicast group, the protocol processing module sends a high-level message to the main control module, and the main control module sends a message to the user interface board to delete the user port from the corresponding multicast VC. In this way, the user will No more data messages will be received from this multicast group.

For all the above systems, the interface unit connected to the transmission bus will have a priority scheduling function, but for the user-side transmission bus interface unit, the data packets transmitted to the transmission bus may only be unicast data packets Therefore, the priority scheduling function of the interface unit can be disabled.

The above are only preferred embodiments of the solution of the present invention, and are not intended to limit the protection scope of the present invention.

Claims

Claim

1. A method for implementing data packet transmission, characterized in that the method includes the following steps:

a. The sender converts the data message to be sent into a cell and sends it out;

b. The receiving end receives the cell and transmits the data packet corresponding to the cell according to the information carried by the cell.

2. The method according to claim 1, further comprising: setting a transmission bus connecting a transmitting end and a receiving end, wherein the cell is a cell set on a transmission bus, and the information Yuan has corresponding VPI / VCI;

In step a, the transmitting end transmits the converted cells to a transmission bus:

In step b, the receiving end receives the cell from a transmission bus.

3. The method according to claim 1 or 2, wherein the data message comprises: a unicast data message, a multicast data message, and a broadcast data message.

4. The method according to claim 3, wherein the cells are asynchronous transmission mode ATM cells;

The method further includes: establishing a dedicated channel corresponding to the cell identifier of the transmitting end and the receiving end, establishing a correspondence between the source medium access control MAC address in the data message and the virtual path identifier and virtual channel identifier VPI VCI of the VC, and Establish the correspondence between the cell identifier and the VPI / VCI of the VC.

5. The method according to claim 4, wherein the cell identity comprises: a unicast cell identity, a multicast cell identity, and a broadcast cell identity.

6. The method according to claim 5, wherein the unicast cell identifier includes characteristic information of a destination end of the unicast cell, and the multicast cell identifier includes a multicast group number.

7. The method according to claim 4, wherein the sending end is a network side, the receiving end is a user side, and the network is an IP network; The step a includes: the network side converts the data packet into a VPI / VCI cell according to the MAC address of the data packet to be sent, and determines a corresponding cell identifier according to the VPI VCI of the cell, and thereafter And sending the cell and the cell identifier together through a dedicated channel corresponding to the cell identifier.

8. The method according to claim 7, wherein in the step a, before the network side sends the cell and the cell identifier, the network side further comprises: the network side determines the current according to a predetermined algorithm and cell priority. The cell and the cell identifier are allowed to be sent, and then the sending operation is performed.

9. The method according to claim 7, wherein in step b, the receiving end transmitting the data message corresponding to the cell according to the information carried by the cell, comprising:

Each user side judges whether the cell is a unicast cell ID, a multicast cell ID or a broadcast cell ID according to the cell ID of the received cell;

If it is a unicast cell identifier, each user side determines whether it corresponds to the cell identifier according to the cell identifier of the cell, and if so, determines a user terminal that needs to receive the cell according to the cell identifier. And restore the cell to a unicast data message and transmit to the user terminal; otherwise, discard the cell;

If the cell is a multicast identifier, each user-side user terminal according to the pre-recorded information request data packet to determine whether there is a user terminal needs to receive the cell, and the cell is a reduction of the multicast data ¹ ^ gen Transmit the text to the user terminal; otherwise, discard the cell;

If it is a broadcast cell identifier, each user side restores the cell to a broadcast data message and transmits it to all user terminals.

10. The method according to claim 4, wherein the transmitting end is a user side, and the receiving end is a network side; and the network is an IP network.

The step a includes: the user side converts the request data packet transmitted from the user terminal into A cell, and transmitting the cell together with the unicast cell identifier to a network side through a dedicated channel corresponding to the unicast cell identifier;

In step b, the network side sends the data packet according to a destination MAC address of the data packet.

11. The method according to claim 10, wherein the information carried in the request data message is a request multicast data message;

The method further includes: recording related information of the request data message on the network side or the user side;

The related information includes: address information of the user terminal, and a multicast group number of the requested multicast data message.

12. The method according to claim 1, wherein the cell is an ATM cell, the sending end is a network side, and the receiving end is a user side; the network is an ATM network; and step a includes: : The network side composes the ATM cells sent from the ATM network into an Ethernet frame, adds the VL AN ID to the Ethernet frame, and then multicasts the multicast frame in the Ethernet frame according to the correspondence between the multicast group and the multicast VC. Convert it into ATM cells, and set the cell identifier and destination characteristic information for the ATM cell, and then send it to the transmission bus; according to the correspondence between the identification information of the Ethernet and the VC identifier of the user, the unicast in the Ethernet frame The frame is converted into an ATM cell, and a multicast group number and a multicast cell are set for the ATM cell, and then sent to the transmission bus;

In step b, the receiving end transmitting the data message corresponding to the cell according to the information carried by the cell includes: after the user side determines to receive the ATM cell, and according to the multicast group number or the destination end's The characteristic information will form the Ethernet frame by removing the ATM cells of the related information, and forward the composed Ethernet frame according to the destination MAC address in the frame.

13. The method according to claim 12, wherein the user side is connected to the RTU through a user VC; The user side forwarding the Ethernet frame according to the destination MAC address in the frame includes: the user side sends the corresponding ATM cell to the RTU according to the destination MAC address, and the RTU converts the received ATM cell into an Ethernet frame and send.

14. The method according to claim 1, wherein the cell is an ATM cell, the sending end is a user side, and the receiving end is a network side; the network is an ATM network; and the user side passes the user VC is connected to RTU;

The step a includes: the RTU connected to the user side converts the data message sent by the user terminal into an ATM cell and sends it to the user side, and the user side adds a unicast message to the cell according to the VPI / VCI of the user VC Element identification, characteristic information of the destination, and sending the cell, unicast cell identification, and characteristic information of the destination to the transmission bus;

In step b, the receiving end transmitting the data packet corresponding to the cell according to the information carried by the cell includes: the network side determines to receive the cell according to the characteristic information of the destination end of the ATM cell, and according to the The VPI / VCI of the cell converts the ATM cell into an Ethernet frame corresponding to the VLAN, and records the correspondence between the source MAC address of the Ethernet frame and the user VC identifier, and then converts the Ethernet frame into an ATM cell. The ATM cell is transmitted to the corresponding ATM network.

15. The method according to claim 10 or 14, wherein the data message sent by the user terminal is an IGMP application message requesting to join the multicast;

In step b, after receiving the cell, the receiving end further includes: judging whether the data message corresponding to the cell is an IGMP application message for applying to join the multicast,

If yes, record the relevant information of the message and authenticate the user terminal; determine whether the multicast VC exists after the authentication is passed, and if so, add the user terminal to the multicast VC In; otherwise, establish a multicast VC for the user terminal;

If not, continue.

16. The method according to claim 10 or 14, wherein the user terminal The Ethernet frame sent by the UE is an IGMP application message requesting to leave the multicast. In step b, after the receiving end receives the cell, it further includes: determining whether the data message corresponding to the cell is the request to leave the group. The IGMP application message broadcasted, if yes, delete the user terminal from the corresponding multicast VC; otherwise, continue.

17. The method according to claim 7, 10, 12 or 14, further comprising: sending, by the network side, a universal multicast query to all user terminals at a certain time, if the user terminal is at a set time If no response message is sent, it is determined that the user has left the multicast group; otherwise, the query is continued.

18. A system for implementing data message transmission, comprising: a network-side interface device: converting a data message sent from a network into a cell, and sending the cell together with a cell identifier to a transmission bus;

User-side interface device: receiving a cell sent by a network-side interface device to a transmission bus, and sending the cell to a corresponding user terminal according to a cell identifier of the cell.

19. The system according to claim 18, wherein:

The user-side interface device further converts the data message sent by the user terminal into a cell, and sends it to the transmission bus together with the unicast cell identifier;

The network-side interface device further receives a cell sent by the user-side interface device to the transmission bus, and sends a data message corresponding to the cell to the network.

20. The system according to claim 19, wherein the user-side interface device comprises:

User equipment interface unit: used to convert a data message transmitted from a user terminal into a cell and transmit it to a transmission bus interface unit connected to itself; and restore the cell transmitted by the transmission bus interface unit to a datagram And send it to the corresponding user terminal;

Transmission bus interface unit: It has a priority scheduling function, and is used to send the cells transmitted by the user equipment interface unit and the corresponding cell identifiers to the transmission bus together; The cell on the transmission bus is described, and the cell is sent to the user equipment interface unit according to the cell identifier.

21. The system according to claim 20, wherein the user equipment interface unit comprises:

User terminal access unit: configured to convert a data message transmitted by the user terminal into a cell, and send the cell bearer to a cell bearer in a predetermined frame; and bearer transmitted from the cell bearer The cells in the predetermined frame are restored into data messages and transmitted to the user terminal;

Cell carrying unit: used to transmit a cell transmitted by a user terminal access unit through a predetermined frame to a transmission bus interface module; and transmit a cell transmitted by the transmission bus interface module

22. The system according to claim 21, wherein the cell carrying unit is: an asymmetric digital subscriber line chip, or a high-speed digital subscriber line chip, or a high-bit digital subscriber line sleeve.

23. The system according to claim 19, wherein the network-side interface device comprises:

Data message processing unit: used to convert a data message transmitted from the network into a cell, and transmit the cell and the corresponding cell identifier to a transmission bus interface unit with an arbitration function; and the arbitration function is provided. The cells transmitted by the transmission bus interface unit are restored as data packets and transmitted to the network;

Transmission bus interface unit: It has a priority scheduling function for determining a cell identifier corresponding to a cell transmitted by the data message processing unit, and determining whether to allow the cell and the cell according to a predetermined algorithm and priority. The identification is transmitted to the transmission bus; and a cell on the transmission bus is received, and a cell to be transmitted to the data message processing unit is determined according to the cell identifier corresponding to the cell, and the cell is transmitted to the data processing unit .

24. The system according to claim 19 or 23, wherein the network-side interface device further comprises: an interface conversion unit: configured to connect the network-side interface device to a network.

25. The system according to claim 24, wherein the interface conversion unit is a Fast Ethernet FE optical port, or a FE electrical port, or a G-bit Ethernet optical port.

26. The system according to claim 19, wherein the network is an ATM network, and the network-side interface device further comprises:

Protocol conversion module: used to form ATM cells transmitted from the ATM network into an Ethernet frame, tag the Ethernet frame with a VLAN ID, and send the unicast frame in the processed Ethernet frame to the unicast message processing unit, Send the multicast frame to the multicast message processing unit; and convert the information sent by the unicast message processing module into ATM cells and send it to the network-side VC;

Unicast message processing unit: receives a unicast frame sent by a protocol conversion module, converts the unicast frame into an ATM cell according to the correspondence between the destination MAC address in the frame and the user VC identifier, and sends the ATM cell to the transmission bus interface Unit; and forward the unicast information sent by the transmission bus interface unit;

A multicast message processing unit: receiving a multicast frame sent by a protocol conversion module, converting the multicast frame into an ATM cell according to a correspondence relationship between a multicast group and a multicast VC, and sending the ATM cell to a transmission bus interface unit; And forward the multicast information sent by the transmission bus interface unit;

Transmission bus interface unit: It has the function of priority scheduling, and is used to receive ATM cells from unicast message processing unit and multicast message processing unit, and send the received ATM cells to the transmission bus; and The ATM cells on it are sent to the unicast message processing module.

27. The system according to claim 19 or 26, wherein the system further comprises:

A main control module: configured to perform authentication processing on a request data packet received by a network side, and After the authentication is passed, the user terminal sending the request data message is added to the multicast VC; the transmission bus interface unit in the network-side interface device further includes: a protocol processing unit: used to determine that the transmission bus interface unit receives the Whether the data message corresponding to the ATM cell is an IGMP application message, and sends the determined IGMP application message to the main control module. When it is determined that the data message is not an IGMP application message, the The broadcast information is sent to the unicast message processing module, and the multicast information is sent to the multicast message processing module.

28. The system according to claim 27, wherein the protocol processing unit comprises: an IGMP application message capture processing module, an IGMP application message querier, or an IGMP PROXY module, configured to send an IGMP application message to the IGMP application message. The protocol processing unit provides information for users to join or leave the multicast group.

29. The system according to claim 26 ', characterized in that: there is more than one user VC in the system, one end of the user VC is terminated on the RTU connected to the user terminal, and the other end is terminated on the network side A transmission bus interface unit, which passes through a user RTU, a user-side transmission bus interface unit, and a transmission bus;

There is a network-side VC in the system. One end of the network-side VC is terminated on the BAS device of the ATM network, and the other end is terminated on the transmission bus interface unit on the network side, and the ATM network and the transmission bus interface unit on the network side are passed in the middle.