CN113489642B

CN113489642B - PIM-SM source registration optimization method

Info

Publication number: CN113489642B
Application number: CN202110754030.1A
Authority: CN
Inventors: 蒲涛
Original assignee: Xinhe Semiconductor Technology Wuxi Co Ltd
Current assignee: Xinhe Semiconductor Technology Wuxi Co Ltd
Priority date: 2021-07-04
Filing date: 2021-07-04
Publication date: 2023-05-12
Anticipated expiration: 2041-07-04
Also published as: CN113489642A

Abstract

The invention discloses a PIM-SM source registration optimization method, wherein the registration forwarding tree creation flow is as follows: when S-DR receives the multicast data from the multicast source, no multicast forwarding list item exists at this time, the multicast data is sent to the protocol layer for registration and encapsulation, and unicast is sent to RP; when the S-DR sends a registration message, monitoring a sending port, creating a temporary forwarding table item T (S, G), wherein the forwarding port is the registration message sending port; the intermediate router monitors the forwarding of the registration message, also creates a temporary forwarding table item T (S, G), and the forwarding port is the forwarding port of the registration message. The registration multicast tree is created quickly and efficiently, the time for continuously sending the registration message is reduced, and the registration processing burden of the S-DR is lightened; registration messages from each S-DR are reduced, so that the processing load of RP is greatly relieved, and the performance bottleneck point of the whole multicast system is optimized.

Description

PIM-SM source registration optimization method

Technical Field

The invention relates to the technical field of multicast routing, in particular to a PIM-SM source registration optimization method.

Background

PIM-SM is a multicast routing technique commonly used in large networks. The method carries out the on-demand forwarding of the multicast data according to the requirements of the multicast receiving end. According to the protocol standard, the creation of the PIM-SM multicast forwarding path is divided into the following three main phases:

the first stage: creation of RPT. For creating a shared forwarding tree RPT from the multicast aggregation point RP to the receiving end.

As shown in fig. 1, S-DR is a multicast designated router on the multicast source side, and R-DR1 and R-DR2 are multicast designated routers on the receiver side. The receiver 1 and the receiver 2 apply for adding a specific multicast group to the designated routers R-DR1 and R-DR2 through IGMP protocol, trigger the R-DR1 and R-DR2 to initiate a Join message to RP, and create a forwarding table entry along the way, thereby forming a multicast forwarding path tree from RP to R-DR, called a shared tree RPT. After reaching the RP, the multicast data will be forwarded through the RPT to R-DR1 and R-DR2 and eventually to receiver 1 and receiver 2.

And a second stage: and registering a multicast source. For creating a multicast forwarding path from a multicast source to an RP, called a multicast source tree.

As shown in fig. 2, when the S-DR receives the multicast data sent by the multicast source, the flow of the multicast registration source will be triggered, the S-DR encapsulates the original multicast data into a registration message, unicast forwards the registration message to the RP, the RP receives the registration message, sends a (S, G) Join message to the S-DR, creates a (S, G) multicast forwarding table along the path, and the forwarding port is the receiving port of the (S, G) Join message, so as to finally form a multicast forwarding path from the S-DR to the RP, which is called a multicast source tree. In this process, the S-DR will continuously register and encapsulate the received multicast data, and unicast is sent to the multicast convergence point RP.

The multicast source tree, the S-DR, except for continuing to send registration messages, copies the original data and forwards the original data to the RP through the multicast source tree. And after the RP receives the original multicast data, sending a registration stopping message to the S-DR, and stopping sending the registration message. To this end, the subsequent multicast data is forwarded to the RP entirely through the multicast source tree. Finally, the shared tree RPT multicast created through phase one is forwarded to the receiver.

And a third stage: STP switching. For creating a shortest forwarding path from the multicast source to the R-DR, reducing unnecessary detours through the RP.

As shown in fig. 3, when the original multicast data arrives at R-DR, a (S, G) Join message to Source may be initiated according to a trigger condition, thereby creating a shortest multicast forwarding path from Source to R-DR, referred to as SPT. Whereas the switch from RPT to SPT forwarding paths is called SPT switch. Taking fig. 3 as an example, the shortest path tree path from the multicast source to the receiver 1 is: multicast Source- > S-DR- > R-DR1- > receiver 1.

In the above process, especially in the second stage of registration process, the hardware cannot automatically package the registration message, and needs to be sent to the protocol layer for software packaging. If too many messages need to be registered and packaged, a great processing burden is caused to the S-DR and the SP, so that the performance of the whole multicast system is affected.

As can be seen from the timing diagram of the anchor registration mechanism shown in fig. 4, the registration procedure is started from the first multicast data trigger until the S-DR receives a registration stop message from the RP. After 4 message interaction (namely, registration message, (S, G) Join message, original multicast data and registration stop message interaction) processes are needed between the S-DR and the RP, the transmission of the registration message is stopped. The number of interactions is large, and most of interactions are software layer interactions, the processing time is long and unstable, a large number of registration messages are easily packaged and sent to the RP for a long time, the processing overhead of S-DR registration packaging is increased, and meanwhile, the processing burden of the RP for unpacking the registration messages is further increased. For RP, it will face registration messages from multiple S-DRs and participate in other processes of multicast routing, which is the performance bottleneck point in the multicast system, and too many registration messages will definitely make the processing burden more serious, thereby affecting the stability of the whole multicast system.

To avoid the above problems, the solutions currently adopted are:

1. the number of registration messages is reduced on the S-DR side to relieve the burden of S-DR and RP.

2. The reception of registration messages is limited on the RP to ease the processing burden.

However, in either of the above methods, the multicast data is discarded as a means, and the forwarding rate is reduced to reduce the overall forwarding performance. The multicast data cannot be forwarded as much as possible, and meanwhile, the processing load of the multicast data is lightened, so that the multicast forwarding performance of the whole system is improved.

Disclosure of Invention

The invention aims to provide a PIM-SM source registration optimization method, which reduces the processing load of S-DR and RP on registration messages and optimizes the performance of the whole multicast system while providing the maximum multicast forwarding efficiency so as to solve the problems in the background technology.

In order to achieve the above purpose, the present invention provides the following technical solutions:

the PIM-SM source registration optimization method rapidly creates a temporary multicast forwarding path tree by monitoring and utilizing a unicast registration message forwarding path, so that original multicast data is forwarded through the forwarding tree as early as possible, and the original message is reduced to be registered, packaged and forwarded as early as possible; the temporary multicast forwarding tree is created according to the forwarding of the registration message, and is called a registration forwarding tree.

The creation flow of the registration forwarding tree is as follows:

when S-DR receives the multicast data from the multicast source, no multicast forwarding list item exists at this time, the multicast data is sent to the protocol layer for registration and encapsulation, and unicast is sent to RP; when the S-DR sends a registration message, monitoring a sending port, creating a temporary forwarding table item T (S, G), wherein the forwarding port is the registration message sending port;

in addition, the Router in the middle monitors the forwarding of the registration message, and also creates a temporary forwarding table item T (S, G), and the forwarding port is the forwarding port of the registration message; thus, a multicast forwarding path from S-DR to RP, i.e. a registration forwarding tree, is formed.

Because the forwarding path of the registration forwarding tree is consistent with the forwarding path of the registration message, the registration message reaches the intermediate router before the original multicast message, the intermediate router can ensure that the T (S, G) table item on the router is issued before the original data is forwarded by a software and hardware means, so that the original multicast data is forwarded according to the table item, and finally the RP is achieved.

The optimized forwarding flow is as follows:

after the S-DR creates the T (S, G) list item, the subsequent multicast message is directly multicast-forwarded through the list item, and registration, encapsulation and transmission are not carried out any more; the time T from the first registration message to the down-sending T (S, G) table item is shorter, so that the number of registration messages generated by the prior logic is smaller;

the RP processes the registration message and the original multicast data according to standard processing logic, and triggers the (S, G) Join and the registration stop message to the S-DR; (S, G) Join will create (S, G) entries along the way with the receiving port as the forwarding port, ultimately forming a multicast source path tree from S-DR to RP; the (S, G) table item is used as a later multicast forwarding table item, and T (S, G) is not effective any more, so that the switching from the multicast registration tree to the multicast source tree is completed, and the standard processing flow is returned to be compatible with the standard multicast source registration behavior;

in order to avoid accidental loss of registration messages and periodically refreshing T (S, G) table entries, when S-DR finishes transmitting the T (S, G) table entries to the time T2 from receiving registration stop information, a certain number of original messages are copied and registered periodically, and the frequency N is configurable; periodic fixed low frequency registration does not place a processing burden on the system.

The present invention requires revising the processing logic on the S-DR and the intermediate router, the detailed processing of which is described below.

S-DR processing flow

The S-DR is mainly different from the standard PIM-SM in the process flow:

a learning flow of newly adding T (S, G) temporary list items;

(S, G) Join message processing, and updating (S, G) list items;

the periodic copies register the package.

T (S, G) learning process of S-DR, concretely as follows:

(1) When the S-DR receives the multicast data from the multicast source, the multicast data is sent to the CPU for registration and encapsulation because the forwarding rule of the multicast group is not created;

(2) After the registration message is encapsulated, the registration message is sent to the RP through unicast;

(3) S-DR monitors the forwarding of registration message, and obtains the forwarding port as the forwarding port of T (S, G);

(4) S-DR creates T (S, G) list item according to this, multicast transmitting port is the port for transmitting registration message;

(5) After the T (S, G) list item is created, the multicast data is directly forwarded according to the T (S, G) list item, and the multicast data is not uploaded to the software for registration and encapsulation.

In addition, subsequent monitoring of the registration message updates the T (S, G) table entry if a change in the transmission port is found.

2. (S, G) Join processing and (S, G) entry updating

According to the standard definition of PIM-SM, when S-DR receives the (S, G) Join information from RP, creating (S, G) list item, besides register message, original multicast message also copies a copy to make multicast forwarding according to (S, G) list item. At this time, the continuous registration message stops being sent already when the T (S, G) entry is created, and its original multicast stream starts to be forwarded also when the T (S, G) entry is created. Therefore, at this time, only the newly created (S, G) table entry is required to be used as a forwarding table, and the T (S, G) table entry is not validated any more, so that the switching of the forwarding path of the temporarily generated registry tree to the forwarding path of the multicast source tree is completed.

3. Periodic copy registration encapsulation

Considering the loss of registration messages, the RP cannot be reached, and the possible registration message forwarding paths change. After the T (S, G) entry is created, until the S-DR receives the registration stop message, i.e., within the time range T2 in fig. 7, the S-DR configures a fixed sampling encapsulation frequency according to the condition of the whole system, for example, samples 3 original packets within the interval range of every second, and sends the packets to the protocol layer for registration encapsulation, so as to maintain the forwarding entry of the registration forwarding tree between the RPs.

(II) treatment of intermediate routers

In the technical scheme of the invention, the intermediate router is introduced to learn the registration forwarding tree and maintain the final multicast source tree list item, and the main revision processing part is as follows:

newly adding a learning flow and maintenance of a T (S, G) temporary table item;

(S, G) updating and maintaining forwarding table items.

T (S, G) entry learning and maintenance

The T (S, G) learning flow of the intermediate router is as follows:

(1) The registration message from the S-DR will precede the original multicast data;

(2) The router monitors the forwarding of the registration message, and the invention is not limited to hardware or software monitoring learning;

(3) The router learns the forwarding port of the registration message and creates a T (S, G) table entry, wherein the forwarding port is the forwarding port of the registration message;

(4) The subsequently arriving multicast data will be forwarded according to the T (S, G) entry.

Furthermore, continuous registration message listening will be used to update T (S, G) entries in time.

2. Updating and maintaining (S, G) forwarding entries

As with the S-DR processing, the intermediate router performs (S, G) table item learning according to the Join message of RP according to the standard definition of PIM-SM, and the forwarding port is the receiving port of the (S, G) Join message; this (S, G) entry will serve as a forwarding entry for the subsequent original multicast data, whereas the previous T (S, G) entry is no longer valid, thus completing the switch to the multicast source tree.

Compared with the prior art, the invention has the advantages that:

1. the registration multicast tree is created quickly and efficiently, the time for continuously sending the registration message is reduced, and the registration processing burden of the S-DR is lightened;

2. registration messages from each S-DR are reduced, so that the processing load of RP is greatly relieved, and the performance bottleneck point of the whole multicast system is optimized;

3. the registration multicast tree is the same as the forwarding table item of the multicast source tree, which is favorable for hardware realization, and can rapidly realize line speed multicast forwarding under the condition of hardware support, thereby reducing a large amount of packet loss caused by software registration and increasing multicast data forwarding efficiency.

Drawings

Fig. 1 is a schematic diagram of shared tree RPT creation.

Fig. 2 is a schematic diagram of multicast source tree creation.

Fig. 3 is a shortest path tree switching diagram.

Fig. 4 is a timing diagram of a multicast registration mechanism

FIG. 5 is a flow chart of the registration forwarding tree creation of the present invention

Fig. 6 is a schematic diagram of a structure of a registered forwarding path tree according to the present invention.

Fig. 7 is a flow chart of forwarding after optimization according to the present invention.

FIG. 8 is a T (S, G) learning flow chart of S-DR in the present invention.

Fig. 9 is a T (S, G) learning flow chart of the intermediate router in the present invention.

Fig. 10 is a schematic diagram of the duration of a registration message according to the conventional scheme.

Fig. 11 is a diagram of registration message duration using a registration forwarding tree in accordance with the present invention.

Detailed Description

The technical scheme of the patent is further described in detail below with reference to the specific embodiments.

In this embodiment, a temporary multicast forwarding path tree is quickly created by monitoring and using a unicast registration packet forwarding path, so that original multicast data is forwarded through the forwarding tree as early as possible, and registration, encapsulation and forwarding of the original packet are reduced as early as possible; the temporary multicast forwarding tree is created according to the forwarding of the registration message, and is called a registration forwarding tree.

1. The creation flow of the registration forwarding tree is as follows:

as shown in fig. 5, when the S-DR receives multicast data from a multicast source, no multicast forwarding table entry exists at this time, the multicast data is sent to a protocol layer for registration and encapsulation, and unicast is sent to the RP; when the S-DR sends a registration message, monitoring a sending port, creating a temporary forwarding table item T (S, G), wherein the forwarding port is the registration message sending port;

in addition, the Router in the middle monitors the forwarding of the registration message, and also creates a temporary forwarding table item T (S, G), and the forwarding port is the forwarding port of the registration message; thus, a multicast forwarding path, i.e. a registration forwarding tree, from the S-DR to the RP is formed, as shown in fig. 6.

2. The optimized forwarding flow is as follows:

as shown in fig. 7, after the S-DR creates a T (S, G) table entry, the subsequent multicast message is directly multicast-forwarded through the table entry, and no registration, encapsulation and transmission is performed; the time T from the first registration message to the down-sending T (S, G) table item is shorter, so that the number of registration messages generated by the prior logic is smaller;

S-DR processing flow

The S-DR is mainly different from the standard PIM-SM in the process flow:

a learning flow of newly adding T (S, G) temporary list items;

(S, G) Join message processing, and updating (S, G) list items;

the periodic copies register the package.

1. As shown in fig. 8, the T (S, G) learning process of S-DR is specifically as follows:

2. (S, G) Join processing and (S, G) entry updating

3. Periodic copy registration encapsulation

(II) treatment of intermediate routers

(S, G) updating and maintaining forwarding table items.

T (S, G) entry learning and maintenance

As shown in fig. 9, the T (S, G) learning flow of the intermediate router is as follows:

2. Updating and maintaining (S, G) forwarding entries

In this embodiment, the comparison analysis is performed on the duration of the conventional registration message and the duration of the registration message using the registration forwarding tree of the present invention:

fig. 10 depicts a conventional scheme registration message duration, in which registration encapsulation of multicast data from a multicast source is continuously sent to the RP over time t. t=t1+t2+t3+t4+t5+t6+t7.

Wherein T1, T3, T5, T7 are transmission times of the interactive messages, which are assumed to be fixed time Tt. And T2, T4 and T6 are software processing times of the message processing logic, and are all assumed to be fixed time Ts for comparison and analysis.

The duration of the registration message is t=4×tt+3×ts.

The time chart of the registration message after the present invention is shown in fig. 11 below, where the duration of the registration message is t1=t1, T1 is the listening learning processing time of the registration message, and is also assumed to be Ts, so t1=ts.

And periodic sampling registration message transmission time t2=t2+t3+t4=2×tt+ts. But the periodic sampling registration frequency is adjustable, and continuous registration messages can not be generated to form pressure on the system, so the influence of the registration messages can be ignored

In summary, compared with the long-time continuous registration process of the traditional scheme, the method and the device greatly shorten the continuous registration time, thereby greatly reducing registration messages in the multicast system and further improving the overall performance of the multicast system.

While the preferred embodiments of the present patent have been described in detail, the present patent is not limited to the above embodiments, and various changes may be made without departing from the spirit of the present patent within the knowledge of one of ordinary skill in the art.

Claims

The PIM-SM source registration optimization method rapidly creates a temporary multicast forwarding path tree, namely a registration forwarding tree by monitoring and utilizing a unicast registration message forwarding path, and is characterized in that the creation flow of the registration forwarding tree is as follows: when S-DR receives the multicast data from the multicast source, no multicast forwarding list item exists at this time, the multicast data is sent to the protocol layer for registration and encapsulation, and unicast is sent to RP; when the S-DR sends a registration message, monitoring a sending port, creating a temporary forwarding table item T (S, G), wherein the forwarding port is the registration message sending port; the Router in the middle monitors the forwarding of the registration message, and also creates a temporary forwarding table item T (S, G), and the forwarding port is the forwarding port of the registration message.
2. The PIM-SM source registration optimization method of claim 1, wherein the S-DR differs from the standard PIM-SM process flow mainly in that:

a learning flow of newly adding T (S, G) temporary list items;

(S, G) Join message processing, and updating (S, G) list items;

the periodic copies register the package.
3. The PIM-SM source registration optimization method of claim 1, wherein the intermediate router is introduced to learn a registered forwarding tree and maintain a final multicast source tree table entry, and wherein the main revision processing portion is as follows:

newly adding a learning flow and maintenance of a T (S, G) temporary table item;

(S, G) updating and maintaining forwarding table items.
4. The PIM-SM source registration optimization method of claim 2, wherein the T (S, G) learning process of S-DR is specifically as follows:

(1) When the S-DR receives the multicast data from the multicast source, the multicast data is sent to the CPU for registration and encapsulation because the forwarding rule of the multicast group is not created;

(2) After the registration message is encapsulated, the registration message is sent to the RP through unicast;

(3) S-DR monitors the forwarding of registration message, and obtains the forwarding port as the forwarding port of T (S, G);

(4) S-DR creates T (S, G) list item according to this, multicast transmitting port is the port for transmitting registration message;

(5) After the T (S, G) list item is created, the multicast data is directly forwarded according to the T (S, G) list item, and the multicast data is not uploaded to the software for registration and encapsulation.
5. The PIM-SM source registration optimization method of claim 2, wherein the RP processes the registration message and the original multicast data in compliance with standard processing logic, and when the S-DR receives the (S, G) Join message from the RP, creates a (S, G) table entry, and in addition to the registration message, the original multicast message will copy a copy to be multicast forwarded according to the (S, G) table entry; at this time, the continuous registration message stops being sent when the T (S, G) table entry is created, and the original multicast stream starts to be forwarded when the T (S, G) table entry is created; at this time, the newly created (S, G) table entry is taken as a forwarding table, and the T (S, G) table entry is no longer effective, so that the switching of the temporarily generated forwarding path of the registry tree to the forwarding path of the multicast source tree is completed.
6. The PIM-SM source registration optimization method of claim 2, wherein after the T (S, G) entries are created, the S-DR configures a fixed sampling encapsulation frequency according to the overall system situation until the S-DR receives a registration stop message within a time range from a periodic registration message transmission time T2, and the periodic fixed low-frequency registration does not cause a processing burden to the system.
7. The PIM-SM source registration optimization method of claim 3, wherein a T (S, G) learning flow of the intermediate router is as follows:

(1) The registration message from the S-DR will precede the original multicast data;

(2) The router monitors the forwarding of the registration message, and the method comprises hardware or software monitoring learning;

(3) The router learns the forwarding port of the registration message and creates a T (S, G) table entry, wherein the forwarding port is the forwarding port of the registration message;

(4) The subsequently arriving multicast data will be forwarded according to the T (S, G) entry.
8. The PIM-SM source registration optimization method of claim 3, wherein the intermediate router performs (S, G) entry learning according to the Join message of the RP according to standard definition of the PIM-SM, and the forwarding port is a receiving port of the (S, G) Join message; this (S, G) entry will serve as a forwarding entry for the subsequent original multicast data, whereas the previous T (S, G) entry is no longer valid, thus completing the switch to the multicast source tree.