CN1378365A - IP group broadcast route repeating optimizing method - Google Patents

Abstract

The invention relates to an IP multicast routing forwarding optimization method. In the IP forwarding device running the PIM-SM protocol, this method only uses the source address and group address (S, G) route for multicast forwarding; for non-(S, G) routes to generate virtual (S, G) routes Multicast forwarding. Using this method, PIM-SM only uses (S, G) routes to realize the forwarding function in the forwarding process, which improves the forwarding efficiency of the PIM-SM protocol, and also enables hardware devices that originally only supported the DVMRP and PIM-DM protocols to pass Replace the software and directly support the PIM-SM protocol. The method can be applied to forwarding devices such as routers or IP switches to improve the forwarding efficiency of the devices.

Description

A Method for Optimizing IP Multicast Routing and Forwarding

Field:

The invention relates to a network multicast method, in particular to an IP network multicast optimization method, which belongs to the field of computer network communication.

Background technique:

The multicast routing protocol is a routing control protocol that implements multicast message forwarding on the third layer of IP (Internet Protocol) network. The function of the multicast routing protocol is to provide routing information for the forwarding of multicast packets, that is, to indicate to the forwarding engine which direction the received multicast packets should be forwarded to. There are three types of commonly used IP multicast routing protocols: DVMRP (Distance Vector Multicast Routing Protocol), PIM-SM (Protocol Independent Multicast Routing Protocol Sparse Mode) and PIM-DM (Protocol Independent Multicast Routing Protocol Dense Mode ).

The forwarding engine is a component in the IP forwarding device that specifically executes the packet forwarding function according to the instruction of the routing table. To implement high-speed forwarding of multicast packets, the forwarding engine in the device is usually implemented by hardware. While hardware forwarding improves forwarding efficiency, it also brings some limitations, such as not being able to support complex processing well and increasing product costs. The relationship between the multicast routing protocol and the multicast forwarding engine in the device is shown in Figure 1: the arrow in the figure indicates the route submission direction, 1 is the physical interface, 2 is the link layer protocol, 3 is the IP forwarding engine, 4 is the IP layer, 5 is the TCP/UDP protocol layer, 6 is the unicast routing protocol layer, and 7 is the multicast routing protocol layer.

For the DVMRP and PIM-DM protocols, they only use (S, G) routing, and the forwarding process is relatively simple. The (S, G) route is a type of multicast route, and the route matching condition is a source address and a group address. Since these two protocols only use (S, G) routing and do not use (*, G) routing and (*, *, RP) routing, high-speed forwarding can be relatively easily realized in the forwarding engine. Wherein, (*, G) routing is a multicast routing type whose routing matching condition is a group address, and (*, *, RP) routing is a multicast routing type whose routing matching condition is a centralized point address.

However, due to the technical characteristics of the protocol itself, it is not suitable to use the DVMRP and PIM-DM protocols in many applications, but the PIM-SM protocol is required. In the design of the PIM-SM protocol, the forwarding process is cumbersome. Therefore, an IP forwarding device using a forwarding engine that only supports (S, G) routing can only run the DVMRP or PIM-DM protocol, but cannot effectively run the PIM-SM protocol. To implement the PIM-SM protocol for a forwarding engine that is not easy to support complex processing procedures, it will involve the optimization of the forwarding process.

If PIM-SM can only use (S, G) routing to realize the forwarding function in the forwarding process, it can not only improve the forwarding efficiency of the PIM-SM protocol, but also enable hardware devices that originally only support DVMRP and PIM-DM protocols to Directly support the PIM-SM protocol by replacing the software. In traditional routers, packet forwarding is implemented by software. Due to the high flexibility of software implementation, complex processing can be completed, so standard PIM-SM multicast routing and forwarding can be realized. However, the processing efficiency of software is very limited, and current high-speed routers and IP switches do not use software to implement forwarding processing.

Chinese invention patent 00119490 discloses a broadband Ethernet multicast method. The method is a multicast protocol working on the link layer of the second layer of the network model, that is, the Ethernet protocol layer, which is an extension of the Ethernet technology. In practice, more complex multicast functions are usually implemented at the third layer, namely the network layer, specifically the IP protocol layer. The problem to be solved by the invention belongs to the third layer multicast technology.

Purpose of the invention:

In order to support the PIM-SM protocol, the functions of three routing types (S, G), (*, G) and (*, *, RP) are realized in a forwarding engine that only supports (S, G) type routing, the present invention A new method of virtual (S,G) routing is proposed, which is a special (S,G) routing used to replace (*,G) and (*,*,RP) routing in forwarding engines. Invented technical solution:

The forwarding optimization method of IP multicast routing proposed by the present invention, completes the forwarding process by the full-time forwarding engine, and processes the standard protocol function and the additional routing processing process proposed by the method by the software; the software adds the routing information to the multicast routing table according to the protocol standard and saves it , and submit it to the forwarding routing table of the forwarding engine to control the forwarding of multicast packets. In the IP forwarding device running the PIM-SM protocol, only the source address and group address (S, G) route are used for multicast forwarding; for the multicast routing forwarding of this protocol, the source address is obtained from the multicast data stream and group address information, generate a special (S, G) route and add it to the multicast routing forwarding table of the forwarding engine, replacing the multicast route (*, *, RP) that should be used by the protocol to match the centralized point address and the multicast route that matches the group address The multicast route (*, G) performs multicast forwarding.

The specific steps are: 1. When the PIM-SM protocol software submits (*, G) and (*, *, RP) types of routes to the forwarding engine, they are all ignored and not processed, and only (S, G) routes are still directly submitted to forwarding engine. 2. The forwarding engine receives the multicast data and forwards the route according to the protocol: if no corresponding forwarding route is found, or the reverse path forwarding check fails, the data packet is passed to the protocol software for processing. 3. The protocol software checks the multicast routing table after receiving the data message, if it finds the corresponding (*, G) or (*, *, RP) route, but there is no (S, G) route, then use the found route As a basis, add the source address and group address obtained from the data packet, generate (S, G) type routing, and submit it to the forwarding engine; this new (S, G) routing is called a virtual (S, G) routing. The virtual (S, G) route should not be added to the multicast routing table in the protocol software, so as not to affect the correct operation of the protocol; it can also be added to the multicast routing table, but the special flag is set to be different from the (S, G) route generated by the standard protocol. distinguish.

For the generated virtual (S, G) route, if the standard protocol also generates (S, G) route, since there can only be one route for the same (S, G) two-tuple in the forwarding engine, in the software Make some fit adjustments.

The forwarding engine uses (S, G) type routing to realize the multicast forwarding processing of the PIM-SM protocol. Therefore, for the three multicast routing protocols on the IP network, the distance vector multicast routing protocol DVMRP, the dense mode protocol independent multicast routing protocol Both PIM-DM and the sparse mode protocol-independent multicast routing protocol PIM-SM can only use (S, G) routing to implement multicast packet forwarding. The forwarding device applied in this solution is a router or an IP switch or the like. The forwarding engine in the device can be a software module or a hardware component, and the software part that performs additional processing on the PIM-SM protocol is located inside the PIM-SM protocol software module, or the driver adaptation module between the PIM-SM protocol software module and the forwarding engine middle. Beneficial effect:

The method simplifies the multicast routing and forwarding process of the PIM-SM protocol, and enables the IP forwarding device to realize high-efficiency PIM-SM multicast routing and forwarding with low implementation complexity and implementation cost under the premise of complying with the standard protocol. Although this method increases the function of software processing, the increase of system overhead is very small, and all improvements are only reflected inside the device and shielded from the outside. From the external performance of the equipment, the equipment using this technology fully complies with the PIM-SM protocol standard, and there is no compatibility problem with all network equipment that meets the standard.

The method can be applied to an IP forwarding device using a software forwarding engine or a hardware forwarding engine. Especially when applied to hardware forwarding equipment, it can effectively reduce the design complexity of the hardware forwarding engine, reduce production costs, and improve forwarding efficiency. The method can be applied to IPV4 network and IPV6 network, and applicable product forms include various forwarding devices in the IP network, such as routers, three-layer switches, broadband access devices, IP gateways, and the like.

Description of drawings:

Figure 1 Relationship diagram between multicast routing protocol and multicast forwarding engine

Figure 2 Standard PIM-SM forwarding flowchart

Figure 3 Process flow chart of the optimized forwarding engine

Figure 4 The optimized PIM-SM protocol software-related processing flow

Example:

According to the PIM-SM protocol standard stipulated in RFC2362, the PIM-SM protocol module

A (*,*,RP) route is generated when:

-PMBR obtains new RP address information;

-RP receives PIM JOIN/PRUNE (*, *, RP) message from PMBR.

A (*,G) route is generated when:

- Receive IGMP member joining information;

- A PIM JOIN/PRUNE (*, G) join message is received.

A (S,G) route is generated when:

-The leaf node starts the SPT forwarding tree switch; (SPT is the source path tree)

- A PIM JOIN/PRUNE(S, G)RPT pruning message is received. (RPT is the centralized point path tree)

- A PIM JOIN/PRUNE (S, G) join message is received.

The above PMBR refers to the PIM multicast border router, which is a special networking node in the PIM-SM protocol. RP refers to the centralization point, which is a special networking node in the PIM-SM protocol. JOIN/PRUNE is a message type stipulated by the PIM protocol—join/prune message. Its function is for the downstream device to indicate to the upstream device the type of multicast data it needs to receive or the type of data it wants to reject. An IGMP member refers to a data receiver that joins a multicast network through the IGMP protocol. IGMP (Internet Group Management Protocol) is a protocol for managing multicast data receiver information at the edge of a multicast network.

In these cases, according to the protocol standard, these routes should be added to the multicast routing table in the protocol software for storage, and submitted to the forwarding routing table of the forwarding engine to control the forwarding of multicast packets. The standard PIM-SM forwarding process is shown in Figure 2. In the protocol specification, there is no deliberate distinction between the message forwarding process and the protocol processing process. The flowchart in FIG. 2 mainly focuses on the forwarding process, and also includes some protocol event processing triggered by the forwarding process stipulated in the protocol.

The optimized forwarding engine processing flow is shown in Figure 3, and the PIM-SM protocol software-related processing flow is shown in Figure 4. It can be seen from the figure that the optimized forwarding process has been significantly simplified.

This method uses (S, G) routing instead of (*, G) and (*, *, RP) routing for the PIM-SM protocol in the forwarding engine. Since there can only be one route for the same (S, G) tuple in the forwarding engine, some adjustments need to be made when the standard protocol also generates the (S, G) route. The adjustment rules are as follows:

1. When the protocol software submits routes to the forwarding engine, if there is a (S, G) binary in the forwarding engine

The same old route, the old route will automatically become invalid. That is, the newly submitted route overrides the old route.

2. When the (S, G) route is generated by the standard protocol protocol, it should usually be submitted to the routing engine so that the existing

The virtual (S, G) route of is invalid. But the case in 3 is an exception.

3. During the SPT tree switching process, immediately adding the (S, G) route to the forwarding engine may cause virtual

The (S, G) route was replaced prematurely, causing interruption of data flow. Should be handled according to the following rules:

- When the SPT upstream interface is consistent with the original RPT upstream interface, the (S, G) route of the SPT is not mentioned

Hand it over to the forwarding engine. (It can also be submitted in theory, but it has no practical effect.)

- When the SPT upstream interface is inconsistent with the original RPT upstream interface, the (S, G) route of the SPT is inconsistent

It can be submitted to the forwarding engine immediately, but waits for the data flow to arrive. Due to the data input interface and RPT

The upstream interface of the virtual (S, G) route is inconsistent, and an RPF check will be generated when the data packet arrives.

If the check fails, the forwarding engine will hand over the message to the protocol software for processing. At this time, the (S, G) of SPT

The route is submitted to the forwarding engine to replace the virtual (S, G) route.

- When the device on the SPT has no (*, G) route (ie not in the RPT tree), the (S, G) route

It can be submitted to the routing engine immediately; it can also not be submitted until the data stream arrives

Due to the mismatch, the forwarding engine will hand over the message to the protocol software for processing. At this time, the (S, G) of SPT

The route is submitted to the forwarding engine.

Claims (9)

1. an IP group broadcast route repeating optimizing method is finished forwarding process by the forwarding engine sole duty, and the additional lanes that is proposed by software processes standard agreement function and this method is by processing procedure; Software adds multicast routing table by consensus standard with routing iinformation to be preserved, and is submitted to the converting route of forwarding engine, is used to control the forwarding of multicast message.It is characterized in that: in operation PIM-SM protocol of I P forwarding unit, only use source address and group address promptly (S, G) route is carried out multicast forwarding; Multicast routing forwarding for this agreement, among multicast traffic stream, obtain source address and group address message, generate special (S, G) route adds the multicast route forwarding table of forwarding engine, the multicast path that replaces dot address in the set of matches that this agreement should adopt originally is by (*, *, RP) and the coupling group address multicast path by (* G) carries out multicast forwarding.

2. IP group broadcast route repeating optimizing method according to claim 1 is characterized in that: (* is G) with (* to the forwarding engine submission for the PIM-SM protocol software, *, RP) during the route of type, all ignore and do not add processing, have only that (S, G) route still directly is submitted to forwarding engine.

3. IP group broadcast route repeating optimizing method according to claim 2 is characterized in that: the protocol software is checked multicast routing table after receiving data message, if find corresponding (*, G) or (*, *, RP) route, and do not have (S, G) route, then the route to find adds the source address and the group address that obtain from data message, generates (S, G) the type route is submitted to forwarding engine; This is new, and (S, G) route is virtual (S, G) route.

4. IP group broadcast route repeating optimizing method according to claim 3, it is characterized in that: for the virtual (S that is generated, G) route, if standard agreement has also generated (S, G) route, because (S, G) can only there be a route in two tuples, therefore carry out some and cooperate and adjust in software for same in the forwarding engine.

5. according to claim 3 or 4 described IP group broadcast route repeating optimizing methods, it is characterized in that: virtual (S, G) route should not add the multicast routing table in the protocol software, in order to avoid influence the true(-)running of agreement.

6. according to claim 3 or 4 described IP group broadcast route repeating optimizing methods, it is characterized in that: virtual (S, G) route adds multicast routing table, but be provided with distinctive mark and standard agreement generation (S, G) route is distinguished.

7. according to the described IP group broadcast route repeating optimizing method of one of arbitrary claim of claim 1-6, it is characterized in that: forwarding engine uses (S, G) multicast forwarding of type route implementing PIM-SM agreement is handled, therefore for three kinds of multicast routing protocols on the IP network, distance vector multicast routing protocol DVMRP, Protocol Independent Multicast-Dense Mode Routing Protocol PIM-DM, Protocol Independent Multicast-Sparse Mode Routing Protocol PIM-SM, can only use (S, G) route implementing multicast message forwarding.

8. according to the described IP group broadcast route repeating optimizing method of one of arbitrary claim of claim 1-7, it is characterized in that: forwarding unit is router or IP switch etc.

9. according to the described IP group broadcast route repeating optimizing method of one of arbitrary claim of claim 1-8, it is characterized in that: the forwarding engine in the equipment can be software module or hardware component, the software section that the PIM-SM agreement is carried out additional treatments is positioned at PIM-SM protocol software inside modules, or in the driving adaptation module between PIM-SM protocol software module and the forwarding engine.

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