CN101022411A - Multi-link binding protocol message zone receiving method - Google Patents

Abstract

A method for receiving multi-link binding protocol message fragments, comprising: setting a pointer and a sequence number window; receiving message fragments, and judging whether the sequence number of the received message fragments is continuous with the pointer; if the judgment result is a report If the sequence number of the message fragment is not continuous with the pointer, then judge whether the sequence number of the message fragment is located in the sequence number window; if the judgment result is that the sequence number of the message fragment is outside the sequence number window, modify the pointer to jump Change tracking. The invention reduces the dependence of the receiving end on timing IDLE message fragmentation, and also shortens the service recovery time of the receiving end. In addition, the present invention can tolerate a certain degree of mutation of the serial number of message fragments and can judge discontinuous messages, quickly track the jump of the serial number of message fragments, speed up service recovery, and improve the robustness of the system .

Description

Method for receiving multi-link bundling protocol packet fragments

technical field

The invention relates to communication technology, in particular to a method for receiving multi-link binding protocol message fragments.

Background technique

The Multilink Binding Protocol (MP, Multilink PPP) is a method of bundling multiple physical channels through the protocol. According to the protocol RFC1990, the corresponding serial number is added, and multiple physical channels are regarded as a logical channel, which provides more than a single physical channel. Greater bandwidth to meet user bandwidth requirements. In the implementation of the multi-link bundling protocol, the receiving end of the message fragments sorts the received message fragments by detecting the sequence number, so as to ensure that the logical channel uploads the message fragments to the The network layer at the receiving end handles it.

The multi-link bundling protocol internally provides an order-preserving mechanism, that is, when the link is established, the sequence number sent by the sender must start from 0. The receiving end maintains a reference sequence number locally, and compares the reference sequence number with the sequence number of the received message fragment; if the local reference sequence number of the receiving end is different from the received sequence number, the receiving end waits for After all the message fragments in the network are received, the message fragments are uploaded to the network layer.

As shown in FIG. 1 , the sender sends message fragments 0-5, and the message fragment whose sequence number is 3 is lost. Before the new packet fragment arrives at the receiving end, the receiving end will wait for fragment 3 to arrive.

In order to prevent the receiving end from waiting for too long to lose packet fragments, the existing technology provides the following two solutions:

1. The sending end regularly sends IDLE message fragments to the receiving end, so that the receiving end can quickly judge that the unreceived message fragments are lost and upload other received message fragments.

2. Set the waiting time for receiving message fragments through the timer on the receiving end. If the time for the message fragments to reach the receiving end exceeds the time set by the receiving end timer, the receiving end will judge that the message fragments are lost, and the receiving end will upload Fragmentation of other received packets.

However, the disadvantages of the above two solutions are: using method 1, the IDLE message fragments sent regularly by the sender will consume part of the bandwidth; and using method 2, once the sequence number of the message fragments received by the receiving end jumps, The receiving end uses the timer to judge that the packet fragment loss speed is too slow, the link recovery time is long, and the user needs to wait for a long time.

Contents of the invention

In order to solve the shortcomings of the prior art, the purpose of the embodiment of the present invention is to provide a multi-link bundling protocol message fragmentation receiving method, which reduces the dependence on timing IDLE message fragmentation and shortens the service recovery time of the receiving end .

In order to achieve the purpose of the above invention, the present invention provides: a method for receiving multi-link bundling protocol message fragments, including: setting pointers and sequence number windows; receiving message fragments, and judging the sequence of received message fragments Whether the number is continuous with the pointer; if the judgment result is that the serial number of the message fragment is not continuous with the pointer, then judge whether the serial number of the message fragment is in the sequence number window; if the judgment result is that the serial number of the message fragment is in Outside the serial number window, modify the pointer to track the serial number jump.

The serial number window has an upper limit position and a lower limit position; the distance between the pointer and the upper limit position is equal to the distance between the pointer and the lower limit position.

In the step of judging whether the sequence number of the message fragment is located in the sequence number window, if the result of the judgment is that the sequence number of the message fragment is located in the sequence number window, the following steps are also included: judging that the sequence number of the message fragment is Whether it is located between the upper limit position and the pointer or between the lower limit position and the pointer, if the result of the judgment is that the sequence number of the message fragment is between the upper limit position of the sequence number window and the pointer, store the message fragment into the buffer according to the sequence number; If the judgment result is that the sequence number of the message fragment is between the lower limit position of the sequence number window and the pointer, the message fragment is discarded.

In the step of judging whether the sequence number of the received message fragment is continuous with the pointer, if the judgment result is that the sequence number of the message fragment is continuous with the pointer, the following steps are also included: storing the message fragment according to the sequence number of the message fragment To the buffer; add one to the pointer value; query the continuous message fragments and reassemble the continuous message fragments into messages; upload the message; the receiver modifies the pointer Rpt to point to the maximum value of the serial number of the current continuous received message fragments .

The pointer is used to save the maximum sequence number of the fragmented fragments received continuously.

Modifying the pointer to track the sequence number jump refers to assigning the sequence number of the packet fragment to the pointer.

Storing the message fragments into the buffer according to the sequence numbers refers to calculating the modulo of the sequence numbers of the message fragments and the depth of the buffer to calculate the storage address of the message fragments in the buffer.

Buffer depth refers to the number of buffers used to temporarily store message fragments.

The distance between the upper limit position and the pointer, and the distance between the lower limit position and the pointer are half the length of the serial number space.

The beneficial effect of the embodiment of the present invention is that it can tolerate a certain degree (in the sequence number window, such as 1/2 sequence number space, the mutation of the sequence number), and the present invention can also quickly judge the non-sequential message fragmentation By tracking the jump of the serial number, the business can be restored quickly and the robustness of the system is improved. Compared with the prior art, the sequence numbers of the packet fragments sent by the sender do not necessarily start from sequence number 0.

Description of drawings

FIG. 1 is a schematic diagram of receiving fragmented packets of an existing multi-link bundling protocol;

Fig. 2 shows that in the embodiment of the present invention, the sequence number of the pointer and message fragmentation is continuous;

Fig. 3 shows the flow chart of the embodiment of multi-link bundling reception message fragmentation reception of the present invention;

Figures 4-6 are schematic diagrams showing the state in which the sequence number of the packet fragment in the sequence number window is located between the lower limit position and the pointer;

FIG. 7A-FIG. 9 are schematic diagrams showing the states of the sequence numbers of packet fragments outside the sequence number window.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the exemplary embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.

As shown in Figure 2, set the Rpt and serial number windows in the receiving end. The pointer Rpt is used to save the maximum value of the sequence numbers of the message fragments received continuously in the receiving end, that is, all the message fragments that the receiving end has received continuously (including the message fragments pointed to by the current value of Rpt and the All message fragments), so the pointer Rpt points to the end of a package that has been correctly assembled or the maximum value of the sequence number of a continuous message fragment that has not been reassembled. The sequence number window is used to indicate the relative position of the newly arrived packet fragment and the pointer Rpt in the buffer. The serial number window includes an upper limit position Hpt and a lower limit position Lpt.

According to the flow chart of the multi-link bundling protocol message fragment receiving method of the present invention shown in FIG. 3 , the implementation process of the present invention is briefly introduced.

Step 301, the receiving end receives the message fragment S' sent by the sending end;

Step 302, the receiving end compares whether the serial number of the message fragment S' is continuous with the pointer Rpt; if so, enters step 309; if not, enters step 303;

Step 303, then the receiving end judges whether the message fragment S' is located in the sequence number window; if so, enter step 306; if not, enter step 304;

Step 304, the receiving end judges that a sequence number jump occurs on the link of the message fragment S', and the receiving end sends it to the buffer for temporary storage according to the sequence number of the message fragment S', exits the process, and the receiving end continues to receive The next packet fragment;

Step 305, the receiving end performs serial number jump tracking, and assigns the serial number of the message fragment S' where the jump occurs to the pointer, so as to modify the pointer Rpt;

Step 306, the receiving end judges whether the serial number of the message fragment S' is between the pointer Rpt and the upper limit position Hpt, if so, then enters step 308; if not, then enters step 307;

Step 307, the receiving end discards the message fragment S';

Step 308, the receiving end sends the message fragment S' to the buffer for temporary storage according to the sequence number of the message fragment S';

Step 309, the receiving end sends the message fragment S' to the buffer for temporary storage according to the serial number of the message fragment S' and adds 1 to the value of the pointer Rpt;

Step 310, the receiving end queries whether there are continuous message fragments that can form a message in the buffer; the receiving end searches forward and backward from the pointer Rpt to find the packet header and the packet tail respectively, if the receiving end finds the packet header and the packet tail, Then enter step 311;

Step 311, the receiving end reassembles the continuous message fragments S' into messages;

Step 312, the receiving end uploads the reassembled message to the network layer;

In step 313, the receiver modifies the pointer Rpt to point to the maximum serial number of the currently continuously received message fragments, that is, the serial number of the last message fragment searched backward when the receiver searches for the end of the packet.

In the above steps 304, 308, and 309, the receiving end takes the modulus of the serial number of the message fragment S' and the depth of the buffer to obtain the address of the message fragment temporarily stored in the buffer array, and calculates The formula shows: the address of the buffer array=serial number% (modulo) buffer length. The buffer depth refers to the number of buffers used by the receiving end to cache message fragments. The receiving end caches message fragments according to the calculated storage address.

Below in conjunction with accompanying drawing 4-9, describe above-mentioned implementation process of the present invention in more detail:

After the receiving end receives the message fragment sent by the sending end, the receiving end extracts the serial number of the message fragment, and the receiving end judges whether the serial number of the message fragment is continuous with the pointer Rpt. As shown in Figure 2, the serial number S' of the message fragment is continuous with the pointer, that is, when S'=Rpt+1, the receiving end assigns the message serial number to the pointer Rpt, indicating that the message serial number is S 'The packet fragment and its previous packet fragments have been continuously received by the receiving end. When the serial number of the message fragment received by the receiving end is continuous with the pointer, after the buffer temporarily stores the message fragment, the receiving end performs forward search and backward search at the same time according to the pointer Rpt to find the address of the message fragment. Packet header and packet tail, if the receiving end finds continuous and complete message fragments, the receiving end reassembles the continuous message fragments in the buffer into messages and uploads them to the network layer for processing, and at the same time, the found packet tails The sequence number of the fragmented packet is assigned to the pointer Rpt. This is because, as shown in Figure 3, after the receiving end receives a message fragment S' that is not continuous with the pointer Rpt, if the message fragment S' is in the sequence number window, the receiving end will not modify the pointer Rpt , however, when the receiving end searches for continuous message fragments and reassembles them into messages, the storage location of the message fragments containing the end of the packet should be the sequence of message fragments continuously received by the receiving end pointed to by the pointer Rpt The storage location for the maximum value of the number.

If the serial number of the message fragment received by the receiving end is not continuous with the pointer Rpt, as shown in Figure 4-6, the serial number of the message fragment S' is between Rpt and the lower limit position Lpt, and the receiving end will set the Packet fragments are discarded. This is because the pointer Rpt stores the maximum value of the sequence numbers of the continuously received packet fragments. If the sequence number of the packet fragment received by the receiving end is before Rpt, it means that the packet fragment should be the packet fragment considered to have been discarded in the past processing, so it must be discarded to ensure that the buffer temporarily stores Fragmented packets can be reassembled and uploaded in sequence.

What needs to be emphasized here is that in this field, the address space of the buffer at the receiving end is usually a circular space, so the relative position between the newly arrived fragment and Rpt changes, and the message fragment received by the receiving end The serial number before Rpt includes the following three situations:

(1), the pointer Rpt is in the middle of the serial number address space of the buffer, as shown in Figure 4, the relationship between the serial number window and the pointer Rpt is: lower limit position Lpt<pointer Rpt<upper limit position Hpt; then message fragmentation The relationship between the serial number S', the serial number window and the pointer Rpt is Lpt<S'<Rpt.

(2), the pointer Rpt is close to the top of the serial number address of the buffer, as shown in Figure 5, the relationship between the serial number window and the pointer Rpt is: upper limit position Hpt<lower limit position Lpt<pointer Rpt; then the serial number of the message fragment The relationship between S', the serial number window and the pointer Rpt is Lpt<S'<Rpt.

(3), the pointer Rpt is close to the bottom of the serial number address of the buffer, as shown in Figure 6, the relationship between the serial number window and the pointer Rpt is: pointer Rpt<upper limit position Hpt<lower limit position Lpt; then the serial number of the message fragment The relationship between S', the serial number window and the pointer Rpt can be: Rpt<S' or Rpt>S' (Rpt<S' is shown in Figure 6, but Rpt>S' is not shown).

If the sequence number S' of the message fragment received by the receiving end is not continuous with the pointer Rpt, and the sequence number S' of the message fragment is outside the sequence number window. Since the address space of the buffer is a circular space, the relationship between the sequence number of the message fragment and Rpt can refer to several situations shown in Fig. 7A, Fig. 7B, Fig. 8 and Fig. 9:

When the sequence number S' of the message fragment received by the receiving end is not continuous with the pointer Rpt and is located outside the sequence number window, the message fragments outside the sequence number window also include the following three types of situations:

(1), the pointer Rpt is in the middle of the serial number address space of the buffer, as shown in Figure 7A and 7B, the relationship between the serial number window and the pointer Rpt is: lower limit position Lpt<pointer Rpt<upper limit position Hpt; The relationship between the slice serial number S' and the serial number window is: S'<Lpt (see FIG. 7A ) or Hpt<S' (see FIG. 7B ).

(2), the pointer Rpt is close to the top of the serial number address of the buffer, as shown in Figure 8, the relationship between the serial number window and the pointer Rpt is: upper limit position Hpt<lower limit position Lpt<pointer Rpt; then the serial number of the message fragment The relationship between S' and the serial number window is Hpt<S'<Lpt.

(3), the pointer Rpt is close to the bottom of the serial number address of the buffer, as shown in Figure 9, the relationship between the serial number window and the pointer Rpt is: pointer Rpt<upper limit position Hpt<lower limit position Lpt; then the serial number of the message fragment The relationship between S' and the serial number window is Hpt<S'<Lpt.

When the sequence number of the message fragment in Fig. 7A, Fig. 7B, Fig. 8, and Fig. 9 is outside the sequence number window, the receiving end judges that the sequence number jumps. This is because, for those skilled in the art, the number of fragments of a message cannot exceed half of the length of the sequence number space. In this embodiment, if the sequence number is outside the sequence number window, it means that the difference between the sequence number S' of the currently received message fragment and the pointer Rpt, that is, the difference between S' and the current continuously received message fragment The difference between the serial numbers exceeds half the length of the serial number space. However, the usual network design will not cause the delay difference of packet fragments between links to reach such a time difference. The message fragment between the message fragment and the message fragment just received has been lost; or the message fragment cannot be reassembled for some reason, for example: the user selects one of the several links bundled as MP A local loopback is performed, and the serial numbers of the packet fragments on the loopback link are obviously asynchronous with those of the packet fragments on several other links, and the packet fragments cannot be reassembled; if the loopback link is Canceled, and the local receiving end tracks the wrong serial number, which will cause the serial number to not be tracked normally.

What needs to be emphasized here is that setting the distance between the upper limit position Hpt and the pointer Rpt and the distance between the pointer Rpt and the lower limit position Lpt to be half the length of the serial number space is a preferred embodiment of the present invention. Because the MP protocol stipulates that the sender must add continuous long sequence numbers (0~0xffffff) and short sequence numbers (0~0xfff) before the fragmented message fragmentation, which is the sequence number space. The sequence number space corresponds to the Smask stored circularly in the buffer. For those skilled in the art, the total number of fragments of a message cannot reach half of the sequence number space. It will be more accurate to use the serial number space length to set the serial number window to perform serial number jumping. For those skilled in the art, the above embodiment reveals that the setting method of the serial number window is not the only way, and those skilled in the art can set the width of the serial number window and the distance between the pointer and the upper limit position and the lower limit position according to the method disclosed in the present invention.

Among them, according to the MP protocol: the structure of the long sequence number and the short sequence number is as follows:

Table 1 Long serial number structure

0xff 0x03 0x00 0x3d B|E|0|0|0|0|0|0| Sequence Sequence Sequence

Table 2 Short sequence structure

0xff 0x03 0x00 0x3d B|E|0|0|Sequence Sequence

It can be seen from the above structure that as long as the starting address of the cache is known and the long and short sequence number settings are known, the sequence number of the message fragment can be retrieved. This content is the same as the prior art, so it will not be described in detail here.

The present invention also solves the problem of judging the loss of message fragments by the timer at the receiving end or by sending IDLE (sequence number only) message fragments to determine the loss of message fragments, which leads to long-term waiting of the link and recovery of the link It takes a long time and user data is easy to be lost in large quantities.

The beneficial effect of the present invention is that it can tolerate a certain degree (such as the mutation of the serial number in the 1/2 serial number space in the serial number window), and the present invention can also quickly judge non-sequential message fragments to track the sequence The number jumps, so as to quickly restore the service and improve the robustness of the system. Compared with the prior art, when the sender starts sending message fragments, the starting sequence number of the message fragments does not necessarily start from 0.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. A method for receiving multi-link bundling protocol message fragments, characterized in that, comprising: Set pointer and serial number window; Receive message fragments, and judge whether the sequence number of the received message fragments is continuous with the pointer; If the judgment result is that the serial number of the message fragment is not continuous with the pointer, then judge whether the serial number of the message fragment is located in the serial number window; If the judgment result is that the sequence number of the message fragment is outside the sequence number window, modify the pointer to track the sequence number jump. 2. The method according to claim 1, wherein the serial number window has an upper limit position and a lower limit position; the distance between the pointer and the upper limit position is equal to the distance between the pointer and the lower limit position. 3. The method according to claim 2, wherein, in the step of judging whether the sequence number of the message fragmentation is located in the sequence number window, if the result of the judgment is that the sequence number of the message fragmentation is located in the sequence number window , also includes the following steps: Determine whether the sequence number of the message fragment is located between the upper limit position and the pointer or between the lower limit position and the pointer; If the judgment result is that the sequence number of the message fragment is located between the upper limit position of the sequence number window and the pointer, store the message fragment into the buffer according to the sequence number; If the judgment result is that the sequence number of the message fragment is between the lower limit position of the sequence number window and the pointer, the message fragment is discarded. 4. The method according to claim 1, wherein, in the step of judging whether the serial number of the message fragmentation received is continuous with the pointer, if the judgment result is that the serial number of the message fragmentation is continuous with the pointer, also Include the following steps: Store the message fragments to the buffer according to the sequence number of the message fragments; Increment the pointer value by one; Query continuous message fragments and reassemble continuous message fragments into messages; upload message; Modify the pointer to point to the maximum value of the sequence number of the currently continuously received message fragments. 5. The method according to claim 1, wherein the pointer is used to store the maximum value of serial numbers of the fragments of the continuously received packets. 6 . The method according to claim 1 , wherein modifying the pointer to track sequence number jumps refers to assigning the sequence number of the message fragment to the pointer. 7 . 7. The method according to claim 4 or 6, wherein storing the message fragments into the buffer according to the serial number refers to: calculating the message fragmentation modulo the serial number of the message fragment and the depth of the buffer; The storage address of the slice in the buffer. 8. The method according to claim 7, wherein the buffer depth refers to the number of buffers used to temporarily store message fragments. 9. The method according to claim 8, wherein the distance between the upper limit position and the pointer, and the distance between the lower limit position and the pointer are half of the length of the serial number space.

Images