CN100417139C - A method for uninterrupted forwarding of multicast data - Google Patents

Abstract

The invention discloses a method for uninterrupted forwarding of multicast data, and relates to the technical field of computer network communication. When the root port of the spanning tree protocol on the non-root bridge layer 3 device is switched, the non-root bridge layer 3 device sets the new root port as the multicast forwarding port, and transmits to the designated port of the root bridge layer 3 device through the new root port. Send Neighbor Discovery Protocol packets; when the root bridge Layer 3 device receives Neighbor Discovery Protocol packets, it sets the designated port as a multicast forwarding port, and responds to the new root port through the designated port. Neighbor Discovery Protocol packets; non-root bridge After the layer-3 device receives the neighbor discovery protocol message responded by the layer-3 device of the root bridge, the link between the new root port and the specified port is established, and the multicast data is forwarded continuously through the link. The method of the invention can shorten the time interval of multicast forwarding blocking caused by root port switching, reduce the time interval to 10 milliseconds, meet the real-time requirement of multicast business, and improve the efficiency of multicast forwarding.

Description

A method for uninterrupted forwarding of multicast data

[technical field]

The invention relates to the technical field of computer network communication, in particular to a method for maintaining uninterrupted forwarding of multicast data.

[Background technique]

As shown in Figure 1, it is a basic structural diagram of a computer communication network. User traffic is connected to a Layer 3 switch through the access network, and multiple Layer 3 switches converge the traffic to the upper Layer 3 switch (as indicated by the dotted box in the figure). As shown), through the aggregation function of the three-layer switch, the user's traffic is finally delivered to the Internet service provider through the core network, and the service provided by the Internet service provider for the user is transmitted to the user in the opposite direction, thereby realizing the end-to-end service connect. Among them, the connection of these three-layer switches forms the aggregation network of the access layer. Generally speaking, the VLAN (virtual local area network) connected by the three-layer switch is divided into two forms:

1. Through Layer 2 convergence, all ports of Layer 3 switches are configured as the same VLAN, and all traffic is converged to the core network through Layer 2 Ethernet switching.

2. Through the three-layer aggregation, the configuration of the inbound VLAN and the outbound VLAN of the traffic aggregated by the three-layer switch is different. IP intercommunication, the traffic is converged to the core network through three-layer IP switching.

In order to ensure the reliability of the link, a Layer 3 switch that is interconnected may configure multiple physical ports (for example, N, N≥2) in the same VLAN (multi-port VLAN), and another switch also has multiple ports. (N) are configured in this VLAN, and the N physical ports of the two switches are connected one by one. Because multicast data is sent by broadcast on the Layer 2 Ethernet link, it supports the application of multicast services. In the case of multi-port VLAN interconnection, multicast data will be broadcast on the interconnected Ethernet link. Storm, in order to prevent broadcast storms on Layer 2 Ethernet links, spanning tree protocols, such as RSTP (Rapid Spanning Tree Protocol) and MSTP (Multiple Spanning Tree Protocol), should be run on all ports of Layer 3 switches. If the Layer 3 switches are connected through Layer 3 aggregation, in order to support multicast forwarding, a multicast routing protocol, such as PIM (Protocol Independent Multicast) protocol, should be enabled on the Layer 3 switch, and the switches exchange multicast routing protocol information A multicast forwarding tree is generated on the entire network, and a multicast forwarding table is generated inside each switch to guide the forwarding of multicast data. At the same time, switches periodically send handshake messages (such as PIM HELLO messages) to maintain connectivity. In the case of multi-port VLAN, because the ports under the VLAN run the spanning tree protocol, on all the physical ports included in a VLAN interface, they can only receive multicast protocol packets from the only port at the same time, and the multicast Traffic is only sent on the port that receives the multicast routing protocol, so as to achieve the purpose of accurately forwarding multicast traffic according to the port.

The Layer 3 switch listens in real time on all ports under the VLAN to see if the multicast protocol message is received. If the port detects the multicast protocol message, it will set this port as a multicast forwarding port, and there will be no listening group. The port of the multicast protocol message is set as a blocking multicast forwarding port; if the multicast forwarding port does not receive a multicast protocol message within a period of time, the multicast forwarding port will become a blocked multicast forwarding port, thereby ensuring Multicast data can be accurately forwarded on the port.

As shown in FIG. 2 , it is a schematic diagram of layer 3 switch interconnection. Layer 3 switch L3(A) and Layer 3 switch L3(B) run the multicast routing protocol, and they are interconnected through Layer 3 interfaces with the same VLAN number. The P1 and P2 ports of Layer 3 switch L3(A) The P3 and P4 ports of L3(B) are Ethernet ports connected to the VLAN. These ports are configured in the same VLAN. The P1 port is physically connected to the P3 port, and the P2 port is physically connected to the P4 port.

Run the spanning tree protocol on ports P1, P2, P3, and P4, set the bridge ID of switch L3 (A) to be smaller than the bridge ID of switch L3 (B), the port ID corresponding to P1 is smaller than the port ID corresponding to P2, and the port corresponding to P3 ID is smaller than the port ID corresponding to P4. Through the spanning tree protocol mechanism, the switch L3 (A) is elected as the root bridge. P1 and P2 are designated ports of the spanning tree protocol. The spanning tree protocol state of the port is Forwarding (forwarding), which can receive and forward data; switch L3 (B) is a non-root bridge, P3 is a root port, the spanning tree protocol state of the port is Forwarding (forwarding), can receive and forward data, P4 is an optional port, and the spanning tree protocol state of the port is Discarding (discarding) ), cannot receive forwarded data.

The switches L3(A) and L3(B) send multicast protocol packets to each other, and the switch L3(A) can only receive the multicast protocol packets sent by the switch L3(B) from the P3 port on the P1 port. The switch L3(B) can only receive the multicast protocol packet sent by the switch L3(A) from the P1 port on the P3 port. Therefore, switches L3 (A) and L3 (B) respectively set P1 and P3 ports as multicast forwarding ports, and set P2 and P4 ports as blocking multicast forwarding ports.

During the operation of the spanning tree protocol, if the root port of the switch L3 (B) changes from P3 to P4, this root port switching operation is at the level of 10 milliseconds, and the result of the switching is that the spanning tree protocol state of the P3 port changes from Forwarding For Discarding, the spanning tree protocol status of the P4 port changes from Discarding to Forwarding. However, in this case, the P4 port cannot forward the multicast data immediately, resulting in the blocking of multicast data forwarding between switches L3(A) and L3(B). broken. Because the P4 port has not received the regular handshake message sent between the switches, the P4 port is still blocking the multicast forwarding port; under normal circumstances, the sending interval of the periodic handshake message sent between the switches is at the minute level. When the root port is switched, the switch L3(B) does not immediately send the handshake message from the P4 port, but will send the handshake message to the switch L3(A) when the next sending cycle of the handshake message stipulated by the switch L3(B) arrives. Send a handshake message, when the P2 port on the switch L3(A) receives the handshake message sent by the switch L3(B) from the P4 port for the first time, the switch L3(A) changes the P2 port from the blocking multicast forwarding port The port is forwarded for multicast, and then, when the sending cycle of the next handshake message stipulated by the switch L3(A) arrives, the handshake message will be sent to the switch L3(B), and the switch L3(B) is the first on the P4 port When the handshake message is received for the first time, the switch L3(B) changes the P4 port from the blocking multicast forwarding port to the multicast forwarding port, so far, the multicast data between the switches L3(A) and L3(B) is restored Forward. Since the P1 port does not receive a periodic handshake packet within a period of time, the P1 port will change from a multicast forwarding port to a blocking multicast forwarding port. What needs to be explained here is that when the root port is switched, it is not necessarily that the P4 port sends the handshake message to the P2 port first, and it may also be that the P2 port sends the handshake message to the P4 port first. In other words, the order of the P2 and P4 ports Sending handshake messages is random. However, regardless of whether the P2 port or the P4 port sends the handshake message first, the forwarding of multicast data between the switches L3(A) and L3(B) will be blocked at the minute level, which does not depend on the speed of the system processor. is dependent on the time specified in the agreement.

Therefore, in the current technical solution, when the root port of the spanning tree protocol is switched, minute-level multicast data blocking will be generated between the switches. Broadcast data blocking is not allowed.

[Content of the invention]

The technical problem to be solved in the present invention is to provide a method for uninterrupted forwarding of multicast data, in the case of interconnection between Layer 3 switches through VLANs containing multiple physical ports, and run a multicast routing protocol on the VLAN interface, Run the spanning tree protocol on all ports of the VLAN. When the root port of the spanning tree protocol changes, it can keep multicast data forwarding uninterruptedly, shorten the time interval of multicast forwarding blocking caused by root port switching, and improve multicast Forwarding efficiency.

The present invention is achieved through the following technical solutions:

A method for uninterrupted forwarding of multicast data, when the root port of the spanning tree protocol on the non-root bridge layer 3 device is switched, the steps include the following steps:

101. The layer-3 device of the non-root bridge sets the new root port as a multicast forwarding port, and the layer-3 device of the non-root bridge does not wait for the sending period of the neighbor discovery protocol message to arrive, and transmits the message to the layer-3 root port through the new root port. The designated port of the device sends neighbor discovery protocol packets;

102. When the third-layer device of the root bridge receives the neighbor discovery protocol message, it sets the designated port as a multicast forwarding port, and the third-layer device of the root bridge does not wait for the sending period of the neighbor discovery protocol message to arrive, and passes The designated port responds to the neighbor discovery protocol message to the new root port;

103. After the third-layer device of the non-root bridge receives the neighbor discovery protocol message responded by the third-layer device of the root bridge, the link between the new root port and the designated port is established, and the multicast data continues through this link. Forward.

Before step 101, it also includes: when the root port of the spanning tree protocol on the non-root bridge three-layer device is switched, the spanning tree protocol states of the new root port and the old root port are forwarding and discarding respectively.

In step 101, when the non-root bridge layer-3 device sets a new root port as a multicast forwarding port, it sets an old root port as a blocking multicast forwarding port.

In step 101, the non-root bridge three-layer device first overtimes its internal periodic Neighbor Discovery Protocol packet sending timer, and after the periodic Neighbor Discovery Protocol packet sending timer expires, it sends a new root port to the root bridge. The designated port of the layer-3 device sends neighbor discovery protocol packets.

In step 102, the three-layer device of the root bridge first times out its internal periodic Neighbor Discovery Protocol packet sending timer, and after the periodic Neighbor Discovery Protocol packet sending timer expires, it sends a message to the new The root port of the node responds to neighbor discovery protocol packets.

The improvement of the present invention is that: the three-layer equipment is a three-layer switch or router.

The improvement of the present invention is that: the neighbor discovery protocol message is a protocol-independent multicast hello message or a join message.

The improvement of the present invention is that: the spanning tree protocol is rapid spanning tree protocol or multiple spanning tree protocol.

In the present invention, when the root port of the spanning tree protocol changes, the above-mentioned technical scheme can keep the multicast data forwarding uninterruptedly, shorten the time interval of multicast forwarding blocking caused by root port switching, and make the time interval from minute to minute The level is reduced to 10 milliseconds, which meets the real-time requirements of multicast services and improves the efficiency of multicast forwarding.

[Description of drawings]

Figure 1 is a basic structural diagram of a computer communication network.

Fig. 2 is a schematic diagram of interconnection between two layer 3 switches.

Fig. 3 is a flowchart of a method for realizing uninterrupted forwarding of multicast data in the present invention.

[Detailed ways]

The present invention is further elaborated below in conjunction with accompanying drawing and embodiment:

In the present invention, the three-layer switch is docked by VLANs that include multiple physical ports, and the multicast routing protocol is run on the docked VLAN interface, and the spanning tree protocol is run on all Ethernet ports included in the docked VLAN; the state of the port It is defined as two types: multicast forwarding state and blocked multicast forwarding state.

As shown in Figure 2, two Layer 3 switches are interconnected. The Layer 3 switch L3(A) and the Layer 3 switch L3(B) run the multicast routing protocol. The two are interconnected through the Layer 3 interface with the same VLAN number. The Layer 3 switch The P1 and P2 ports of L3(A) and the P3 and P4 ports of L3(B) switch are Ethernet ports connected to the VLAN. These ports are all configured in the same VLAN, and the P1 port and the P3 port are physically connected. , the P2 port is physically connected to the P4 port.

Run the spanning tree protocol on the P1, P2, P3, and P4 ports, set the bridge ID of the three-layer switch L3 (A) to be smaller than the bridge ID of the three-layer switch L3 (B), and the port ID corresponding to P1 is smaller than the port ID corresponding to P2, The port ID corresponding to P3 is smaller than the port ID corresponding to P4. Through the spanning tree protocol mechanism, the three-layer switch L3 (A) is elected as the root bridge. P1 and P2 are designated ports of the spanning tree protocol. The spanning tree protocol state of the ports is Forwarding ( Forwarding), can receive forwarding data; Layer 3 switch L3(B) is a non-root bridge, P3 is a root port, the spanning tree protocol state of the port is Forwarding (forwarding), can receive forwarding data, P4 is an optional port, the port’s The spanning tree protocol status is Discarding (discarding), and forwarding data cannot be received.

Under normal working conditions, the three-layer switch L3(A) and the three-layer switch L3(B) respectively start the periodic handshake message sending timer, assuming that the period is m seconds (m>0 seconds), the timer Periodically through the timeout of m seconds, the three-layer switch L3 (A) and the three-layer switch L3 (B) send multicast handshake messages to each other, only in this way can the reliable intercommunication between the two three-layer switches be guaranteed. Since the multicast handshake message is sent between the P1 port and the P3 port, the P1 and P3 ports are set to the multicast forwarding state, and the P2 and P4 ports are set to the blocking multicast forwarding state.

What needs to be added here is that the multicast handshake message can be a PIM HELLO (hello) message, or a JOIN (join) message, but no matter what kind of message it is, it can be collectively referred to as a neighbor discovery protocol message. In this document, switches send Neighbor Discovery Protocol messages to each other to confirm the reachability of each other, so that multicast traffic can reach each other smoothly.

As shown in Figure 3, in order to realize the flow chart of the method for uninterrupted forwarding of multicast data, its specific process is:

Step 1: When a link failure occurs between the P1 port and the P3 port, the forwarding of the multicast stream is interrupted. When the layer-3 switch L3(B) detects this failure information, a failure occurs on the layer-3 switch L3(B). Root port switching, that is: the root port changes from P3 port (old root port) to P4 port (new root port); Layer 3 switch L3(B) immediately changes P4 port from blocking multicast forwarding state to multicast forwarding At the same time, change the P3 port from the multicast forwarding state to the blocked multicast forwarding state. At this time, the spanning tree protocol state of the P3 port is Discarding (discarding), unable to receive forwarded data, and the spanning tree protocol state of the P4 port is Forwarding (forwarding), capable of receiving forwarded data.

Second step: the three-layer switch L3 (B) immediately overtimes the periodic handshake message sending timer, does not wait for the arrival of the sending period of the multicast handshake message, and sends the multicast handshake message to the P2 port immediately on the P4 port.

Step 3: When the P2 port of the three-layer switch L3 (A) (the spanning tree protocol status of the P2 port is Forwarding (forwarding), which can receive and forward data) receives the multicast handshake message for the first time, the P2 port immediately Change from the blocked multicast forwarding state to the multicast forwarding state; the three-layer switch L3 (A) immediately times out the periodic handshake message sending timer, does not wait for the arrival of the multicast handshake message sending period, and sends P4 immediately on the P2 port The port sends a multicast handshake message.

Step 4: The P4 port receives the multicast handshake message, indicating that the three-layer switch L3 (B) and the three-layer switch L3 (A) can reach each other. At this time, the P2 and P4 ports are all set to the multicast forwarding state. The link between P2 and P4 is established, and multicast traffic is forwarded continuously through this link.

The method of the present invention realizes the uninterrupted forwarding of multicast traffic, avoids the periodic time interval between the three-layer switches that send multicast handshake messages to each other, and occurs when the non-root bridge three-layer switch detects a link layer failure. When the Ethernet port is switched (the root port is switched), the non-root bridge Layer 3 switch immediately times out the multicast handshake message cycle timer, and actively sends the multicast handshake message through the new root port, while any Ethernet port of the root bridge switch When the network port receives the multicast handshake message for the first time, the root bridge Layer 3 switch also immediately times out the multicast handshake message period timer, and sends the multicast handshake message to the non-root bridge switch, which speeds up the root bridge switch. The link establishment with the non-root bridge switch reduces the interruption time of the multicast service flow and improves the forwarding efficiency.

In addition, the layer-3 switch in the present invention can be replaced with a router. No matter it is a layer-3 switch or a router, it is a layer-3 device with a routing function. The multicast routing protocol is run on the VLAN interface, and the spanning tree protocol is run on all the Ethernet ports included in the interconnected VLAN, so that the non-stop forwarding method of the present invention can be adopted to realize the purpose of the present invention.

Claims (8)

1. the method for a multicast data uninterrupted forwarding when the root port of Spanning-Tree Protocol on the nonroot bridge three-layer equipment switches, may further comprise the steps:

101, the root port that the nonroot bridge three-layer equipment is new is set to the multicast forwarding port, described nonroot bridge three-layer equipment is not waited for the transmission cycle arrival of neighbor discovery protocol message, sends neighbor discovery protocol message by new root port to the designated port of root bridge three-layer equipment;

When 102, root bridge three-layer equipment is received described neighbor discovery protocol message, described designated port is set to the multicast forwarding port, described bridge three-layer equipment do not waited for the transmission cycle arrival of neighbor discovery protocol message, responds neighbor discovery protocol message by this designated port to described new root port;

103, after the nonroot bridge three-layer equipment is received the neighbor discovery protocol message of root bridge three-layer equipment response, described new root port and the link establishment between the described designated port, multicast packet continues to transmit by this link.

2. the method for a kind of multicast data uninterrupted forwarding according to claim 1, it is characterized in that, also comprised before step 101: when the root port of Spanning-Tree Protocol on the nonroot bridge three-layer equipment switched, the Spanning-Tree Protocol state of new root port and old root port is respectively to be transmitted and abandons.

3. the method for a kind of multicast data uninterrupted forwarding according to claim 1, it is characterized in that: in the step 101, when the new root port of nonroot bridge three-layer equipment was set to the multicast forwarding port, old root port was set to block the multicast forwarding port.

4. the method for a kind of multicast data uninterrupted forwarding according to claim 1, it is characterized in that: in the step 101, the periodicity neighbor discovery protocol message transmission timer of at first overtime its inside of nonroot bridge three-layer equipment, after described periodicity neighbor discovery protocol message transmission timer is overtime, send neighbor discovery protocol message to the designated port of root bridge three-layer equipment by new root port.

5. the method for a kind of multicast data uninterrupted forwarding according to claim 1, it is characterized in that: in the step 102, the periodicity neighbor discovery protocol message transmission timer of at first overtime its inside of root bridge three-layer equipment, after described periodicity neighbor discovery protocol message transmission timer is overtime, respond neighbor discovery protocol message to described new root port by described designated port.

6. according to the method for the arbitrary described a kind of multicast data uninterrupted forwarding of claim 1 to 5, it is characterized in that: described three-layer equipment is three-tier switch or router.

7. according to the method for the arbitrary described a kind of multicast data uninterrupted forwarding of claim 1 to 5, it is characterized in that: described neighbor discovery protocol message is your good message of protocol-independent multicast or participates in message.

8. the method for a kind of multicast data uninterrupted forwarding according to claim 1, it is characterized in that: described Spanning-Tree Protocol is RSTP or Multiple Spanning Tree Protocol.

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