CN101296105A - Method, system and three-layer network equipment for multicast fast switching - Google Patents

Abstract

The present invention provides a method, a system and a three-layer network device for multicast fast switching. In a virtual local area network (VLAN) of a multicast service, if the three-layer network device where the queryer is located generates a topology change notification bridge protocol data unit ( TCN BPDU) or receive TCN BPDU, then send query message in this VLAN; Layer 3 network equipment as Designated Router (DR) in this VLAN according to the query report message sent by the receiving end after receiving the query message, A link forwarding table is formed, and the multicast stream is switched to the link corresponding to the link forwarding table for sending. The present invention adopts a more reasonable method to shorten the time for multicast switching, thereby improving the continuity of multicast services.

Description

Method, system and three-layer network equipment for multicast fast switching

technical field

The invention relates to the technical field of network communication, in particular to a method, system and three-layer network equipment for multicast fast switching.

Background technique

At present, with the development of Internet TV (IPTV), video conferencing and other services, multicast services are more and more widely used on existing networks. In view of the robustness of network services, it is required to perform link backup or Equipment backup, so that when a link fails or a piece of equipment is realized, it can be switched to another link or another equipment without affecting the original business.

Figure 1 is a commonly used network architecture. As shown in Figure 1, the three-layer switch located at the core layer, that is, switch B and switch C, are mutually backed up, enabling Virtual Router Redundancy Protocol (VRRP, VirtualRouter Redundancy Protocol), spanning tree Protocol (STP, Spanning Tree Protocol), multicast routing protocol, Internet Group Management Protocol (IGMP, Internet Group Management Protocol), Multicast Listener Discovery Protocol (MLD, Multicast Listener Discovery), etc., switches A and Switch D located at the user access layer is a Layer 2 switch that enables Layer 2 multicast routing protocols, STP protocols, and so on.

In the above-mentioned network architecture, by configuring the multicast routing protocol, the multicast flow from the multicast source via switch A, switch B, and switch D finally reaches the receiving end. Since STP has been running in the virtual local area network (VLAN), after the link between switch B and switch D fails, switch B will set the port corresponding to the faulty link in itself, that is, the BD port, to a blocking state, and To set a BC port from the blocking state to the forwarding state, the time from sensing a link fault to completing the port setting is very short, usually only about 200ms to 2s. However, after the port setting is completed, the multicast stream cannot immediately reach the receiving end from the multicast source through the links of switch A, switch B, switch C, and switch D, because the forwarding table of the new link has not yet been formed. The formation process of the forwarding table of this new link needs to go through the following process: the querier of the VLAN where the switch B is located sends a query message in the VLAN to query the available links in the VLAN, and the receiving end receives the query message Reply query report message, the link experienced by the query report message is via switch D, switch C, switch B, if switch B is the designated router (DR) in the VLAN, then switch B establishes a link according to the query report message The forwarding entry of the new link.

However, since the querier sends query packets periodically, and the time interval is fixed at 60s, it may take a long time for the querier to send query packets after the port settings are completed, resulting in A long time delay is required to establish a new link forwarding entry, which causes discontinuity of the multicast service during this delay time.

In order to solve this problem, two kinds of solutions are mainly provided in the prior art. One is to reduce the time interval of the query message sent by the querier, for example, to 5s, but this will increase the number of query messages in the VLAN. Correspondingly, the flow of query report messages in the VLAN will also increase, which will cause great pressure on the processing performance of each switch. The second is to pre-configure the forwarding table entries of all ports on the switch. In this way, when the BD port is set to the blocking state and the BC port is set to the forwarding state, the forwarding table corresponding to the BC port can be used immediately without querying the report. However, it is necessary to know the multicast group used by the multicast service in advance to configure the forwarding tables of all ports on the switch in advance, and the configuration work is very complicated. It can be seen that neither of the two solutions in the prior art can reasonably reduce the multicast switching time to improve the continuity of the multicast service.

Contents of the invention

In view of this, the present invention provides a method, system and three-layer network equipment for multicast fast switching, so as to reasonably reduce the time of multicast switching, thereby improving the continuity of multicast services.

A method for multicast fast switching, the method comprising:

In the virtual local area network VLAN of the multicast service, if the three-layer network device where the querier is located generates a topology change notification bridge protocol data unit TCN BPDU or receives a TCN BPDU, the query message is sent in the VLAN;

The Layer 3 network device serving as the Designated Router DR in this VLAN forms a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switches the multicast stream to the link forwarding table corresponding to the link forwarding table. send on the link.

A three-layer network device, the three-layer network device includes: a query trigger unit and a query device;

The query trigger unit is configured to send a trigger notification to the querier when the layer-3 network device generates a TCN BPDU or receives a TCN BPDU;

The queryer is configured to send a query message in the VLAN where the layer-3 network device is located after receiving the trigger notification.

A multicast fast switching system, the system includes a three-layer network device where the querier is located and a three-layer network device as a DR;

The three-layer network device where the queryer is located is used to send a query message in the VLAN where itself is located when generating a TCN BPDU or receiving a TCN BPDU;

The three-layer network device as the DR is used to form a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switch the multicast stream to the link corresponding to the link forwarding table. send on the link.

As can be seen from the above technical solutions, in the method, system and three-layer network equipment provided by the present invention, if the three-layer network equipment where the queryer is located generates a TCN BPDU or receives a TCN BPDU, then the query message is sent in the VLAN, so that The Layer 3 network device acting as the DR can form a link forwarding table and perform multicast switching according to the query report message returned by the receiving end. The present invention associates the original independent STP protocol with the IGMP or MDL protocol, and triggers the sending of the query message by monitoring the generation of TCN BPDU or the receipt of TCN BPDU, instead of IGMP as in the prior art. Or the MDL protocol runs independently and sends query messages in a fixed period. And, because the sending cycle of TCN BPDU message usually only has about 1s, far less than the sending cycle of query message, thereby shortening the time interval from network topology change to query message sending, and the present invention will not cause a large number of Increasing the amount of messages sent by the three-layer network equipment will not cause great pressure on the processing performance of the three-layer network equipment, and there is no need to perform complicated configuration work in advance. Therefore, the present invention adopts a more reasonable way to reduce the Multicast switching time, thus improving the continuity of multicast services.

Description of drawings

Figure 1 is a commonly used multicast backup network architecture diagram;

FIG. 2 is a structural diagram of a switch provided by an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The method provided by the present invention mainly includes: in the VLAN of the multicast service, if the three-layer network device where the querier is located generates a topology change notification bridge protocol data unit (TCN BPDU, Topology Change Notification Bridge Protocol Data Unit) or receives a TCN BPDU, Send the query message in this VLAN; the Layer 3 network device as DR in this VLAN forms a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switches the multicast stream to this VLAN. Send on the link corresponding to the link forwarding table.

Wherein, sending query message in this VLAN can be: generate TCN BPDU or send query message in this VLAN immediately after receiving TCN BPDU, also can wait for the set time after generating TCN BPDU or receiving TCN BPDU, After the Layer 2 network topology converges, send query packets in this VLAN. In the following descriptions, the query message is sent immediately as an example.

The network device mentioned in the above method may be a switch or a router, and the layer-3 network device may be a layer-3 switch or router. In the descriptions of the following embodiments, a switch is used as an example for description.

The above method is described in detail below. Since each switch runs the STP protocol in the VLAN of the multicast service, when the topology structure of the spanning tree converges, that is, when the topology structure is stable, the root bridge switch will periodically pass through each The port sends Bridge Protocol Data Unit (BPDU, BridgeProtocol Data Unit) to monitor the topology of the spanning tree. Once the topology of the spanning tree changes, the root bridge switch is the first to feel the topology change; when the root bridge switch monitors When the topology state of the spanning tree changes, a TCN BPDU is generated and sent through each port in the spanning tree to notify each switch that the topology of the spanning tree has changed.

That is to say, through this feature of the STP protocol, when the switch generates a TCN BPDU or receives a TCN BPDU, it indicates that the spanning tree topology in the VLAN has changed, and multicast switching is required. For STP, once the root bridge switch, root port and designated port are elected successfully, the topology structure of the spanning tree is established, and the network forwarding path in the VLAN is determined. Only the root port and designated port forward multicast streams, and the other All ports are blocked, but each port can receive STP protocol packets.

Wherein, the above-mentioned topology changes may include: a link failure in the current spanning tree, a switch failure in the current spanning tree, a change in the port status in the current spanning tree, etc. These topology changes will cause the current spanning tree to fail. The multicast stream transmission link is unavailable, and a multicast switchover is required.

For example, if switch C shown in Figure 1 is the root bridge switch, then switch C will periodically send BPDUs in the spanning tree with itself as the root bridge, and the sending interval of this BPDU is very short, usually only 1s about. If switch D does not receive the BPDU message sent by switch B within the set time, it means that the link between switch B and switch D is faulty. At this time, switch B will report the fault information to switch C. At this time , switch C perceives that the topology structure of the spanning tree with itself as the root bridge has changed, and needs to perform multicast switching, generate TCN BPDUs and send them in the spanning tree through each port.

In order to facilitate the understanding of the present invention, a brief description of the queryer is firstly given. Usually there is a querier in a VLAN, and the function of the querier is usually implemented by a certain switch in the VLAN, and which switch has the function of the querier has been determined when the network is constructed. The switch where the querier is located may be a root switch or a non-root switch.

If the switch where the querier is located is the root bridge switch, such as switch C shown in Figure 1, if the switch where the querier is located generates a TCN BPDU, it means that the topology of the spanning tree has changed, and the switch immediately passes the forwarding state The port on the VLAN sends query packets.

If the switch where the querier is located is a non-root bridge switch, such as switch B shown in Figure 1, if the switch receives the TCN BPDU sent by switch C, it means that the spanning tree topology has changed, and the switch immediately passes the forwarding state The port on the VLAN sends query packets.

Since the time interval for the root bridge switch to send BPDUs is only milliseconds, and the time for detecting changes in the topology and generating TCN BPDUs is only about 1s, this method can make the query in a short time when the topology changes. The switch sends query messages, reducing the time for forming a new link forwarding table and shortening the delay of multicast switching.

In addition, each switch in the VLAN sets the port corresponding to the failed multicast transmission path to the blocked state after learning that the topology structure of the spanning tree has changed, and uses the STP port setting strategy to select another port to set as the blocking state. Forwarding status. This part is the prior art and will not be repeated here.

After receiving the query message, the receiving end replies with a query report message, and the switch acting as the DR forms a link forwarding table according to the received query report message, and uses the link forwarding table to send the multicast stream. Wherein, the switch serving as the DR is responsible for sending the data of the multicast source to the switch of the spanning tree, and the specific switch serving as the DR is elected through the PIM protocol or other multicast protocols.

For example, switch B as shown in Figure 1, after receiving the TCN BPDU sent by switch C, sets the port BD to the blocking state, and sets the port BC to the forwarding state; if B is the DR, then B receives the query report message , form a link forwarding table according to the reply query report message, the corresponding link of the link forwarding table is switch B via switch C, switch D to the receiving end, and use the link forwarding table to send the multicast stream, if C is the DR, then after C receives the query report message, it forms a link forwarding table according to the reply query report message.

Wherein, when IPv4 is used, the above-mentioned querier is an IGMP querier, and the query message sent is an IGMP query message; when IPv6 is used, the above-mentioned querier is an MLD querier, and the query message sent is an MLD query message.

In addition, due to the change of the spanning tree topology, the switch in the spanning tree may fail. If the switch that originally served as the querier in the spanning tree fails, the query report cannot be sent on the network after the topology changes. It takes a long time to perceive that the switch serving as the querier fails, which also prolongs the time for multicast switching. In order to prevent this from happening, in the present invention, all three-layer switches that have enabled IGMP or MLD can also send query messages in the VLAN immediately when generating TCN BPDUs or receiving TCN BPDUs, and the All Layer 3 switches enabled with IGMP or MLD in the VLAN re-elect the querier. The specific election process can adopt the election method in the prior art, that is, after the three-layer switch receives the query message, it compares the source address of the query message with its own IP address, and finally selects the switch with the smallest IP address as the queryer , the query message used in the election process is the query message sent by the layer-3 switch when generating or receiving the TCN BPDU, so as to ensure that the querier election and the receiving end return the query report according to the received query message Coherence between messages. If the switch where the original querier is located does not fail, the querier will still be elected as the switch; if the switch where the original querier is located fails, a new switch will be elected as the querier.

Still taking the architecture shown in Figure 1 as an example, when switch B and switch C perceive the spanning tree topology changes, that is, when they generate or receive TCN BPDUs, they both send query messages in the VLAN and re-query The election of the querier, if the original querier is switch C, if switch C fails, switch B will be re-elected as the querier, if switch C does not fail, the re-elected switch C will still be the querier. In this way, as long as the Layer 3 switch senses the topology change of the spanning tree, it will send the query message in the VLAN, thus avoiding the multicast switching delay problem caused by the failure of the switch where the original querier is located.

The above is the description of the method of the present invention, and the system and switch provided by the present invention are described below. The system provided by the present invention mainly includes: the layer-3 network device where the queryer is located and the layer-3 network device as PIMDR.

Among them, the layer-3 network device where the querier is located is used to send query messages in the VLAN where it is located when generating TCN BPDUs or receiving TCN BPDUs.

As a layer 3 network device of the DR, it is used to form a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switch the multicast stream to the link corresponding to the link forwarding table to send on.

In addition, the system may also include: other layer-3 network devices other than the layer-3 network device where the querier is located, for sending a query message in the VLAN where it is located when generating a TCN BPDU or receiving a TCN BPDU, and Rerun the election of the querier.

At this time, the layer-3 network device where the querier is located is also used to participate in the re-election of the querier by using the received query message.

FIG. 2 is a structural diagram of a layer-3 network device provided by an embodiment of the present invention. As shown in FIG. 2 , the layer-3 network device may include: a query trigger unit 201 and a queryer 202 .

The query trigger unit 201 is configured to send a trigger notification to the queryer 202 when the layer-3 network device generates a TCN BPDU or receives a TCN BPDU.

The queryer 202 is configured to send a query message in the VLAN where the layer-3 network device is located after receiving the trigger notification.

Since the layer-3 network device in the network may also serve as a root bridge in addition to being a querier, at this time, the layer-3 network device may also include: a topology monitoring unit 203 and a topology notification unit 204 .

The topology monitoring unit 203 is configured to periodically send BPDUs to monitor the spanning tree topology structure with the Layer 3 network device as the root bridge.

The topology notification unit 204 is configured to generate a TCN BPDU when the topology monitoring unit 203 detects that the spanning tree topology changes, and send the TCN BPDU in the spanning tree through each port.

In addition, all network devices in the network have a port setting function when the network topology changes. At this time, the Layer 3 network device may further include: a port setting unit 205 .

The query trigger unit 201 is also configured to send a setting notification to the port setting unit 205 when the layer-3 network device generates a TCN BPDU or receives a TCN BPDU.

The port setting unit 205 is configured to set the corresponding port according to the port setting policy of the STP after receiving the setting notification.

In addition, the layer-3 network device may also serve as a PIM DR at the same time, therefore, the layer-3 network device may also include: a forwarding table forming unit 206 and a multicast stream sending unit 207.

A forwarding table forming unit 206, configured to form a link forwarding table according to the received query report message.

The multicast stream sending unit 207 is configured to switch the multicast stream to the link corresponding to the link forwarding table for sending.

In addition, when the three-layer network device can be used to implement the technical solution for preventing the failure of the three-layer network device where the queryer is located, the three-layer network device can also include: a query message forwarding unit 208, configured to receive the query message and Forward the query message to the next-hop network device;

The election unit 209 is configured to use the query message received by the query message forwarding unit 208 to re-elect the querier.

The specific election process can adopt the election method in the prior art, that is, after the three-tier network device receives the query message, it will compare the source address of the query message with its own IP address, and finally select the three-tier network with the smallest IP address The device acts as an interrogator.

As can be seen from the above description, in the method, system and layer-3 network equipment provided by the present invention, if the layer-3 network equipment where the querier is located generates TCN BPDU or receives TCN BPDU, then send query message in VLAN, so that The Layer 3 network device acting as the DR can form a link forwarding table and perform multicast switching according to the query report message returned by the receiving end. The present invention associates the original independent STP protocol with the IGMP or MLD protocol, and triggers the sending of the query message by monitoring the generation of TCN BPDU or the receipt of TCN BPDU, instead of IGMP as in the prior art. Or the MDL protocol runs independently and sends query messages in a fixed period. And, because the sending cycle of TCN BPDU message usually only has about 1s, far less than the sending cycle of query message, thereby shortening the time interval from network topology change to query message sending, and the present invention will not cause a large number of Increasing the amount of messages sent by the three-layer network equipment will not cause great pressure on the processing performance of the three-layer network equipment, and there is no need to perform complicated configuration work in advance. Therefore, the present invention adopts a more reasonable way to reduce the Multicast switching time, thus improving the continuity of multicast services.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (10)

1. A method for multicast fast switching, characterized in that the method comprises: In the virtual local area network VLAN of the multicast service, if the three-layer network device where the querier is located generates a topology change notification bridge protocol data unit TCN BPDU or receives a TCN BPDU, the query message is sent in the VLAN; The Layer 3 network device serving as the Designated Router DR in this VLAN forms a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switches the multicast stream to the link forwarding table corresponding to the link forwarding table. send on the link. 2. The method according to claim 1, further comprising: the root bridge switch in the VLAN detects that the spanning tree topology with itself as the root bridge occurs by periodically sending bridge protocol data unit BPDUs When changing, generate the TCN BPDU, and send the TCN BPDU in the spanning tree through each port. 3. The method according to claim 2, wherein the change in the spanning tree topology comprises: a link failure in the spanning tree, a failure in a network device in the spanning tree, or a failure in the spanning tree The port status of a network device in the tree changes. 4. The method according to claim 1, characterized in that the method further comprises: other than the Layer 3 network device where the querier is located, other devices that enable Internet Group Management Protocol IGMP or Multicast Listener Discovery Protocol MLD When the three-layer network equipment of generation TCN BPDU or receive TCN BPDU, also send inquiry message in described VLAN; 5. A three-layer network device, characterized in that the three-layer network device includes: a query trigger unit and a query device; The query trigger unit is configured to send a trigger notification to the querier when the layer-3 network device generates a TCN BPDU or receives a TCN BPDU; The queryer is configured to send a query message in the VLAN where the layer-3 network device is located after receiving the trigger notification. 6. The three-layer network device according to claim 5, further comprising: a topology monitoring unit and a topology notification unit; The topology monitoring unit is configured to periodically send BPDUs to monitor the spanning tree topology using the Layer 3 network device as the root bridge; The topology notification unit is configured to generate the TCN BPDU when the topology monitoring unit detects that the topology structure of the spanning tree changes, and send the TCN BPDU in the spanning tree through each port. 7. The three-layer network device according to claim 5, wherein the three-layer network device further comprises: a forwarding table forming unit and a multicast stream sending unit; The forwarding table forming unit is configured to form a link forwarding table according to the received query report message; The multicast flow sending unit is configured to switch the multicast flow to the link corresponding to the link forwarding table for sending. 8. The three-layer network device according to claim 5, characterized in that, the three-layer network device further comprises: a query message forwarding unit, configured to receive the query message and forward the received query message to the next One-hop network equipment; The election unit is configured to use the query message received by the query message forwarding unit to re-elect the querier. 9. A system for multicast fast switching, characterized in that the system includes a layer-3 network device where the queryer is located and a layer-3 network device as the DR; The three-layer network device where the queryer is located is used to send a query message in the VLAN where itself is located when generating a TCN BPDU or receiving a TCN BPDU; The three-layer network device as the DR is used to form a link forwarding table according to the query report message sent by the receiving end after receiving the query message, and switch the multicast stream to the link corresponding to the link forwarding table. send on the link. 10. The system according to claim 9, characterized in that the system further comprises: other layer-3 network devices enabled with IGMP or MLD other than the layer-3 network device where the querier is located, for When generating TCN BPDU or receiving TCN BPDU, send a query message in the VLAN where it is located, and re-elect the querier; The layer-3 network device where the querier is located is also used to participate in the re-election of the querier by using the received query message.

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