CN100477635C - Inter-domain multicast transmission method and edge device - Google Patents

Abstract

The invention discloses a transmission method for multicast within domains to help local host and multicast resources create business connection, which comprises: on edge of the autonomous domain, the device generates and sends opposite group management protocol message to the autonomous domain with multicast resource according to received multicast route protocol packet; it translates send data to host in domain. It also discloses said edge device. In this invention, edge route on access autonomous domain realizes interactive between IGMP protocol translation unit an self multicast route protocol to represent autonomous domain and as access host for opposite.

Description

Inter-domain multicast transmission method and edge device

technical field

The invention relates to the field of multicast service transmission, in particular to an inter-domain multicast transmission method and an edge device.

Background technique

With the increasing popularity of multicast services, such as: Internet-based services such as online games, e-mail, and electronic financial management, especially the widespread use of emerging services such as IPTV (Internet Protocol TV, Interactive Network Television), making cross-autonomous domain ( A network operated by an ISP is called an autonomous domain) and multicast services are becoming increasingly popular. Among them, IPTV is a brand-new technology that utilizes broadband cable TV network and integrates Internet, multimedia, communication and other technologies to provide home users with various interactive services including digital TV. To achieve the above multicast service, it is necessary to coordinate the autonomous domains deployed by different operators to share the multicast service among them.

In the autonomous domain, information is transmitted through intra-domain multicast, and between different autonomous domains, information is transmitted through inter-domain multicast. At present, the implementation methods of inter-domain multicast mainly include MSDP (Multicast Source Discovery Protocol)/MBGP

(Multicast Border Gateway Protocol) and PIM-SSM. The former uses the MSDP protocol to spread the multicast source activity information SA to indicate which multicast sources are available, and at the same time uses MBGP to select the appropriate path for the multicast flow. However, the multicast routing protocols running between domains in this way are not It is PIM-SM. The latter is actually a simplified version of the PIM-SM protocol, which removes the registration process of the multicast source. The group management protocol running on the access side is IGMPV3 or CISCO’s IGMPV3Lite and URD protocols. Users know the address of the multicast source and directly join it to realize Receive multicast traffic.

In the above two solutions, the multicast protocols in different autonomous domains must be the same, that is, the multicast in one autonomous domain is the PIM-SM protocol, and the multicast in the other autonomous domain communicating with it must also be the PIM-SM protocol. However, if the multicast within each autonomous domain is not identical, the above inter-domain multicast transmission cannot be realized. To implement inter-domain multicast, each autonomous domain must be forced to substantially modify configurations, or even update devices, so as to unify the intra-domain multicast protocols of each autonomous domain.

Contents of the invention

The problem to be solved by the present invention is to provide an inter-domain multicast transmission method to solve the defect in the prior art that inter-domain multicast transmission cannot be performed between autonomous domains using different intra-domain multicast protocols.

In order to achieve the above object, the present invention discloses an inter-domain multicast transmission method, which is used to assist hosts in this autonomous domain and multicast sources in other autonomous domains to establish multicast service connections, including the following steps:

A. At the edge device of the autonomous domain, generate a corresponding group management protocol message according to the received multicast routing protocol message, and send the group management protocol message to the autonomous domain where the multicast source is located;

B. At the edge device of the autonomous domain, the multicast group data forwarded from the direction of the multicast source is forwarded to the direction of the host in the autonomous domain.

The group management protocol message described in step A includes: a group management protocol membership report message or a group management protocol leave message;

The group management protocol membership report message corresponds to the multicast routing join message in the multicast routing protocol message, and the group management protocol leave message corresponds to the multicast routing pruning message in the multicast routing protocol message message.

When the edge router in the autonomous domain where the multicast source is located receives the group management protocol membership report message, it collects the multicast groups in the message into a list; when the edge router in the autonomous domain where the multicast source is located receives the group management When the protocol leaves a message, the multicast group in the message is deleted from the list.

The edge router in the autonomous domain where the multicast source is located periodically sends a general group query message to query the members of the multicast group; the edge router playing the role of host in the multicast group responds to the query by sending a response message.

The multicast routing protocol includes: sparse mode protocol independent multicast PIM-SM protocol, dense mode protocol independent multicast PIM-DM protocol or distance vector multicast routing protocol DVMRP.

The group management protocol includes Internet Group Management Protocol IGMP or Multicast Listener Discovery MLD protocol.

The present invention also discloses an edge device for realizing inter-domain multicast, which is used to establish multicast service connections between hosts in this autonomous domain and multicast sources in other autonomous domains. The edge device includes a group management protocol conversion unit. The unit converts the multicast routing protocol message into a group management protocol message, and sends the group management protocol message to other autonomous domains.

The group management protocol message includes a group management protocol membership report message or a group management protocol leave message;

The group management protocol membership report message corresponds to the multicast routing join message in the multicast routing protocol message, and the group management protocol leave message corresponds to the multicast routing pruning message in the multicast routing protocol message message.

The edge device in the autonomous domain where the multicast source is located periodically sends a general group query message to query the members of the multicast group, and the edge device in the multicast group playing the role of the host responds to the query by sending a response message.

Compared with the prior art, the present invention has the following advantages:

In the present invention, different autonomous domains regard each other as each other's access hosts; the edge router in the autonomous domain of the accessing party realizes the linkage between the IGMP protocol conversion unit and its own multicast routing protocol, and acts as the counterparty's host on behalf of its own autonomous domain. The role of the access host.

Furthermore, when the edge router receives the multicast routing protocol joining information of the autonomous domain, it triggers its own IGMP protocol unit, sends an IGMP membership report, and tells the edge routers in the adjacent autonomous domain that it wishes to receive the multicast service; otherwise, if After receiving the leave message of the multicast routing protocol in this autonomous domain, it triggers its own IGMP protocol unit, sends an IGMP leave message, and tells the edge routers in the adjacent autonomous domain that it does not want to receive multicast services. Inter-domain communication between different autonomous domains is realized through the conversion of intra-autonomous domain packets and IGMP packets.

In addition, the present invention does not need to change the multicast routing protocol and most of the related configurations in each autonomous domain, and does not involve the modification of standard protocols. It can be realized only by improving the edge routers in the autonomous domain. Therefore, it provides Greater compatibility is achieved, and the scope of application of the present invention is expanded.

Description of drawings

Fig. 1 is the flowchart of basic principle of the present invention;

Fig. 2 is a network structure diagram of a specific embodiment of the present invention;

Fig. 3 is a network structure diagram of another specific embodiment of the present invention;

Fig. 4 is a network structure diagram of another specific embodiment of the present invention.

Detailed ways

Below we will describe in detail the best implementation of the present invention with reference to the accompanying drawings. First of all, it should be pointed out that the meanings of the terms, words and claims used in the present invention should not be limited to their literal and ordinary meanings, but also include meanings and concepts that are consistent with the technology of the present invention. This is because It is up to us, as inventors, to define terms appropriately in order to best describe our inventions. Therefore, the configurations given in this specification and the accompanying drawings are only preferred implementations of the present invention, rather than enumerating all technical characteristics of the present invention. We need to recognize that there are various equivalents or modifications that could replace ours.

The inter-domain multicast transmission method provided by the present invention is used to assist hosts in this autonomous domain and multicast sources in other autonomous domains to establish multicast service connections. The basic flow is as shown in Figure 1, including the following steps:

S101. At the edge device (usually a layer-3 device, such as a router or a layer-3 switch) of the autonomous domain, generate a corresponding group management protocol message according to the received multicast routing protocol message, and send the multicast source to the autonomous The domain sends group management protocol packets.

s102. At the edge device of the autonomous domain, forward the multicast group data forwarded from the multicast source direction to the host in the autonomous domain.

The present invention will be described below in conjunction with specific embodiments. In the network shown in FIG. The router 13 ; the autonomous domain 200 includes a host 21 , a router 22 connected to the host 21 and an edge router 23 . The autonomous domain 100 communicates with the autonomous domain 200 through the edge router 13 and the edge router 23 . For ease of description, it is agreed here that the interface connecting the edge router 23 to the edge router 13 is called the uplink interface, the interface connecting the edge router 23 to the internal router 22 of the autonomous domain 200 is called the downlink interface; the interface connecting the edge router 13 to the edge router 23 is called the downlink interface , the interface connecting the edge router 13 to the internal router 12 of the autonomous domain 100 is called an uplink interface.

Assume that the PIM-DM multicast routing protocol is running between the internal routers of the autonomous domain 100, and the PIM-SM multicast routing protocol is running between the internal routers of the autonomous domain 200, and the group management protocol is IGMP (in IPV4, group management The protocol is IGMP; when applied to IPV6, the group management protocol can be the corresponding multicast listening and discovery MLD protocol, the implementation methods of the two are the same, but the application environment is different).

In the PIM-DM domain, routers running the PIM-DM protocol periodically send Hello messages to discover adjacent PIM routers, determine leaf networks and leaf routers, and are responsible for electing designated routers in the multi-access network. When the multicast source starts to send multicast data, all network nodes in the domain need to receive the data, so the "diffusion-pruning" (diffusion here can also be understood as joining) method is used to forward multicast data packets. Routers along the route forward the multicast data packets to all interfaces except the RPF corresponding to the multicast source (the interface corresponding to the upstream adjacent node). If there is no multicast group member in a certain area of the network, the routers in this area will send a pruning message, prune the forwarding interface leading to this area, and establish a pruning state, and start a timer at the same time, when the timer expires, pruning The branch state changes to forwarding state again. Among them, the pruning state includes the information of the multicast source and the multicast group. When a member of the multicast group appears in the pruning area, it does not need to wait for the upstream pruning state to The state changes to forwarding state.

In the PIM-SM domain, multicast data packets are forwarded by establishing a multicast distribution tree. The multicast distribution tree is divided into a shared tree and a shortest path tree. PIM-SM completes the multicast distribution tree through the displayed join/pruning mechanism. establishment and maintenance.

When the host 21 in the autonomous domain 200 wants to watch a certain program, the host 21 will obtain the corresponding multicast address from the multicast source 11 through the protocol of the application layer, and then send the IGMP (Internet Group Management Protocol, Internet Group Management Protocol) of the corresponding group. ) membership report message; the router 22 connected to the host 21 will send the joining message of the PIM protocol to the multicast source 11 direction after receiving the IGMP membership report message; since the autonomous domain 200 is connected to the edge router of the autonomous domain 100 There are only 23, so this PIM join message must arrive at edge router 23; Edge router 23 receives the PIM join message from downlink interface, will trigger the IGMP protocol conversion unit to send the IGMP membership report message of corresponding group to edge router 13; When the router 13 finds that there is an IGMP group joining, it will use the flow corresponding to the multicast routing protocol (PIM-DM protocol in the autonomous domain 100) to guide the transmission of multicast data in the group.

When the host 21 is unwilling to watch the program, it will send the IGMP leaving message of the corresponding group; the router 22 connected to it will send the PIM pruning message of the corresponding group to the multicast source direction; Must arrive at edge router 23; Edge router 23 will trigger the IGMP protocol conversion unit to send the IGMP leaving message of corresponding group to edge router 13 when receiving the PIM pruning message from downlink interface; Edge router 13 finds that there is group to leave, will Send pruning messages in the corresponding process to truncate the corresponding multicast stream.

The improvement of the invention concerns only the edge router, ie the edge router 23 in this example. The invention adds an IGMP protocol conversion unit in the edge router, so that the group joining behavior of the multicast routing protocol is converted into the group joining behavior of IGMP, and the group leaving behavior of the multicast routing protocol is converted into the group leaving behavior of IGMP. The specific implementation method of the edge router is as follows:

First, a multicast group list is set and maintained in the edge router 23, and the multicast list is used to store multicast group information. When the edge router 23 receives the PIM-SM joining message of the router 22 in the autonomous domain 200, trigger The IGMP protocol conversion unit sends the IGMP membership report message of the corresponding group to the upstream interface, and stores the multicast group in the message in the multicast list; when the edge router 23 receives the PIM of the router 22 in the autonomous domain 200 - After the SM prunes the message, the IGMP protocol conversion unit is triggered to send an IGMP leave message of the corresponding group to the uplink interface, and the multicast group in the prune message is deleted from the multicast list.

When the edge router 13 receives the IGMP general query message from the uplink interface, it will traverse the multicast group list and start a countdown report timer for each multicast group with a time of 10 seconds. If the IGMP membership report message of the multicast group is not received before the timer expires, the IGMP membership report message of the corresponding group is sent.

When receiving an IGMP group-specific query message from the uplink interface, it will send several IGMP group-specific query messages. At this time, the edge router playing the role of the host responds to the query by sending a response message, and the edge router needs to respond to the IGMP membership report message within the maximum response time, because the interface connecting the edge router 13 to the edge router may also be connected to other Edge routers for hosts or other self-made systems.

The edge router 13 may also be connected to other hosts or edge routers of other autonomous domains. Therefore, when the edge router 23 receives the IGMP membership report message before the timer expires, it should suppress the membership report message the same as the host behavior: delete the multicast group corresponding to the received IGMP membership report message timer.

In addition, in order to prevent aging of the multicast address on the edge router 23, the edge router 23 needs to traverse the multicast group list periodically and send an IGMP membership report message.

There may be multiple edge routers between different autonomous domains in the present invention, as shown in Figure 3, comprising: autonomous domain 300 and autonomous domain 400, including program source 31, router 32 directly connected with program source 31, Edge router 33 and edge router 34; Autonomous domain 400 includes host 41, router 42 directly connected to host 41, edge router 43 and edge router 44; edge router 33 is connected with edge router 43, and edge router 34 is connected with edge router 44 . At this time, although the two autonomous domains are connected through multiple edge routers, for a specific multicast source, only a pair of edge routers are really functioning, because the group join protocol packets of the multicast routing protocol will follow the The unicast routing table is transmitted upwards, and finally only reaches the pair of edge routers with the shortest path. Of course, it is also possible that both edge routers need to make the improvement based on the present invention because the routers in the autonomous domain adopt the multicast message sharing technology.

An autonomous domain includes multiple routers, and a router is connected with multiple hosts, as shown in Figure 4, including an autonomous domain 500 and an autonomous domain 600, wherein the autonomous domain 500 includes a router 510, a router 520, and an edge router 530, and the router 510 connects host 511 (program source) and host 512, router 520 connects host 521 and host 522; autonomous domain 600 includes router 610, router 620 and edge router 630, router 610 connects host 611 and host 612, router 620 connects Connect host 621 and host 622; two autonomous domains communicate through edge router 530 and edge router 630.

The above-mentioned network system composed of two autonomous domains is a simplified solution for the application of the present invention, and the present invention can be applied to the network environment of three or four autonomous domains at the same time. Multicasting is carried out using the existing technology in each autonomous domain, but the inter-domain multicast transmission protocol is changed only by adding the protocol conversion function to the edge router.

The interface of the router in the present invention includes Ethernet port, POS port and other interface types that can run multicast services.

The multicast routing protocol linked with the IGMP protocol conversion unit in the present invention is not limited to PIM-SM, and may also be other protocols, such as DVMRP protocol. All multicast routing protocols have group joining and group leaving behaviors, which are basic routing protocol behaviors; the transformation method is the same, so that the IGMP protocol conversion unit and the multicast routing protocol are linked.

The description about IGMP protocol processing in the present invention is mainly about IGMPV2, but is equally applicable to IGMPV1 and IGMPV3, for IGMPV1, it can only send IGMP membership report message, and can not send leaving message, then receives multicast route In the leave message of the protocol, it does not respond to the general query message and the specified group query message from the edge router, and no longer sends the IGMP membership report message, and the others are the same as IGMPV2. IGMPV3 enhances the functions of IGMPV2, but the enhanced functions are irrelevant to the present invention, and the processing is the same as that of IGMPV2.

In addition to the linkage between the IGMP protocol conversion unit and the multicast routing protocol mentioned in the present invention, the IGMP group can also be statically configured manually.

The present invention also provides an edge router implementing inter-domain multicast, which is used to establish multicast service connections between hosts in this autonomous domain and multicast sources in other autonomous domains. The edge router includes a group management protocol conversion unit. The unit converts the multicast routing protocol message into a group management protocol message, and sends the group management protocol message to other autonomous domains. The multicast routing protocol message, including the group management protocol membership report message or the group management protocol leave message, respectively corresponds to the multicast route joining message and the multicast routing pruning message in the multicast routing protocol message. The edge router in the autonomous domain where the multicast source is located periodically sends a general group query message to query the members of the multicast group, and the edge router playing the role of host in the multicast group responds to the query by sending a response message.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be It is regarded as the protection scope of the present invention.

Claims (9)

1. A transmission method for inter-domain multicast, used to assist hosts in this autonomous domain and multicast sources in other autonomous domains to establish multicast service connections, characterized in that, comprising the following steps: A. At the edge device of the autonomous domain, generate a corresponding group management protocol message according to the received multicast routing protocol message, and send the group management protocol message to the autonomous domain where the multicast source is located; B. At the edge device of the autonomous domain, the multicast group data forwarded from the direction of the multicast source is forwarded to the direction of the host in the autonomous domain. 2. The inter-domain multicast transmission method according to claim 1, wherein the group management protocol message in step A comprises: a group management protocol membership report message or a group management protocol leave message; The group management protocol membership report message corresponds to the multicast routing join message in the multicast routing protocol message, and the group management protocol leave message corresponds to the multicast routing pruning message in the multicast routing protocol message message. 3. The transmission method of inter-domain multicast as claimed in claim 2, characterized in that, when the edge router of the autonomous domain where the multicast source is located receives the group management protocol membership report message, the multicast in the message The groups are collected into the list; when the edge router of the autonomous domain where the multicast source is located receives the leave message of the group management protocol, the multicast group in the message is deleted from the list. 4. The transmission method of inter-domain multicast as claimed in claim 2, characterized in that, the edge router of the autonomous domain where the multicast source is located periodically sends a general group query message to inquire about the members of the multicast group; The edge router acting as the master responds to the query by sending a response message. 5. The inter-domain multicast transmission method according to claim 1, wherein the multicast routing protocol comprises: a sparse mode protocol-independent multicast PIM-SM protocol, a dense mode protocol-independent multicast PIM-DM protocol or Distance Vector Multicast Routing Protocol DVMRP. 6. The inter-domain multicast transmission method according to any one of claims 1 to 5, wherein the group management protocol includes Internet Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD) protocol. 7. An edge device implementing inter-domain multicast, used to establish multicast service connections between hosts in the autonomous domain and multicast sources in other autonomous domains, characterized in that the edge device includes a group management protocol conversion unit, The unit converts the multicast routing protocol message into a group management protocol message, and sends the group management protocol message to other autonomous domains. 8. The edge device for implementing inter-domain multicast according to claim 7, wherein the group management protocol message includes a group management protocol membership report message or a group management protocol leave message; The group management protocol membership report message corresponds to the multicast routing join message in the multicast routing protocol message, and the group management protocol leave message corresponds to the multicast routing pruning message in the multicast routing protocol message message. 9. The edge device for implementing inter-domain multicast according to claim 7, wherein the edge device of the autonomous domain where the multicast source is located periodically sends a general group query message to query the members of the multicast group, and the multicast group The edge device in the master role responds to the query by sending a response message.

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