JP4765892B2 - Data transmission method, data transmission apparatus, and data transmission system for performing multilink bundle control - Google Patents

Description

  The present invention relates to a data transmission method, a data transmission device, and a data transmission system, and in particular, performs multilink bundle control using a multilink communication system that virtually handles a bundle of a plurality of lines as a single line. The present invention relates to a data transmission method, a data transmission device, and a data transmission system.

In recent years, a wireless communication system has become an important base not only for voice communication but also for large-capacity data communication, as represented by the 1x EV-DO system standardized by 3GPP2. In a wireless communication system, a wire connection section is between a wireless base station and various processing devices such as a packet processing device and a speech processing device provided in a center station. In this wired connection section, conventionally, a multilink communication method has been used in which a plurality of lines are bundled to transmit data. Usually, wireless base stations need to be widely distributed in areas where wireless services are provided. Therefore, the distance between the radio base station and the center station is often far away. Under such circumstances, public communication networks using physical lines such as T1 and E1 have mainly been used to connect radio base stations and center stations. T1 is a digital leased line standard established by the American National Standards Institute (ANSI), which multiplexes 24 64kbps lines and has a communication capacity of 1.544Mbps. E1 is a standard widely used in Europe, and is a physical line with a capacity of 2 Mbps with 32 lines of 64 kbps lines.
The amount of data or traffic between the radio base station and the center station increases as the number of subscribers accommodated in the radio base station increases. In response to such an increase in data volume or traffic, it is necessary to take measures to increase the number of physical lines connecting the radio base station to the center station. Therefore, in a communication network using physical lines such as T1 and E1, a multilink communication method is widely used in which a bundle of a plurality of lines is treated as a virtual single line. A typical multilink communication method is a multilink point-to-point protocol (Multilink PPP) disclosed in Non-Patent Document 1.

"RFC 1990-The PPP Multilink Protocol" 1990

  In the conventional multilink communication method, when a failure occurs in each physical line constituting the bundle, the failure detection is performed independently by each member link control unit at each end point. The line in which the failure is detected by the member link control unit is removed from the bundle by the multilink control unit. Thereafter, normal transmission is possible.

However, since the process of removing the member link from the bundle is performed independently at each end point, the end points at both ends of the physical line are temporarily not matched, and an inconsistent state may occur. Frames transmitted during such an inconsistent state cannot be combined, resulting in being discarded by the combining unit.
There are two methods for the member link control unit to detect a physical line failure: a method using a PPP link existence confirmation and a method using a failure detection means of the physical layer. PPP link existence confirmation has a problem that it takes a very long time to detect a member link failure and remove it from the bundle. Multilink PPP usually requires 3 to 5 seconds. Furthermore, since the multilink control unit of each endpoint operates independently, it is impossible to combine the fragment data to the original frame until the member links that make up the bundle match exactly at both endpoints. In this inconsistent period, frame discard occurs. Considering this point, in the example of Multilink PPP, although it depends on the parameter setting, a communication interruption of about 10 seconds at maximum occurs.

  In the situation where the data transmitted between the radio base station and the center station is increased in capacity as in recent years and real-time performance is also required, it is necessary to suppress communication interruptions in a short period as much as possible. For this reason, a method of shortening the health check frame transmission interval by each member link control unit and shortening the detection time of the member link failure can be considered, but there is a disadvantage that the bandwidth for the link is consumed by transmission of control data. is there.

The other method, which uses the fault detection means of the physical layer, can usually be performed in a few milliseconds, so detection in a short time is possible. However, this depends on the type of the physical layer or the operation method and setting of the relay transmission apparatus, and is not always effective. If the failure detection means possessed by the physical layer cannot be used, only the PPP link existence confirmation is available.
The present invention has been made in order to solve the above-described problems, and it is possible to reduce the time during which communication interruption occurs even when a failure occurs in a line regardless of the type of physical layer or the operation method and setting of the relay transmission apparatus. An object of the present invention is to provide a multi-link bundle control method that can be shortened as much as possible and can suppress deterioration in communication quality as much as possible.

  In order to solve the above-described problem, in the present invention, the multilink control unit of the endpoint that has detected a failure in the member link quickly removes the member link that has detected the failure from the bundle used by the own endpoint, The bundle configuration information is immediately transmitted to the opposite endpoint via another member link where no occurrence has occurred. The bundle configuration information includes the member link identifiers of all the member links constituting the bundle, and excludes the member link identifiers of the member links that have detected a failure. The member link identifier is a number or identifier that can uniquely identify each member link.

  The endpoint that has received the bundle configuration information passes the bundle configuration information to the multilink control unit in its own endpoint. The multi-link control unit immediately reconfigures the bundle using only the member link indicated in the received bundle configuration information. As a result, the bundle state can be instantaneously synchronized at both end points, and the member link in which the failure has occurred can be removed from the bundle.

  The multilink control unit of the endpoint that has detected a failure in the member link uses at least one of the member links in which no failure has occurred when transmitting the bundle configuration information. The bundle information may be broadcast using all member links in which no failure has occurred.

The bundle configuration information includes a member link identifier that uniquely identifies each member link, and includes the member link identifier of the member link that should constitute the bundle. In addition to this, the priority of each member link, or The bandwidth allocated to each member link may be included.
The endpoint that has received the bundle configuration information may control the distribution unit based on the priority of each member link specified in the bundle configuration information. Alternatively, the distribution unit may be controlled based on the allocated bandwidth of each member link specified in the bundle information.

  Alternatively, the bundle information may include a quality measurement result of each member link or a band measurement result of each member link measured by a separate means. The endpoint that has received the bundle configuration information may use the information on the quality of each member link or the band measurement result included in the bundle configuration information to control the distribution unit using an arbitrary criterion.

  According to the present invention, when a failure occurs in a member link, the endpoint that detects the failure explicitly notifies the member link that should form the bundle, so that the bundle status can be immediately updated at both endpoints. It is possible to continue communication using a member link that is synchronized and has no failure without interruption. As a result, it is possible to suppress the communication interruption when a failure occurs in a part of the lines, which has been a problem in the prior art, in a short time as much as possible, and to suppress a decrease in communication quality.

  As is clear from the above description, according to the present invention, even when a failure occurs in a part of lines constituting the multilink bundle, communication interruption can be suppressed to a short time as much as possible, and communication quality is reduced. It becomes possible to suppress.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the current technology that is the basis of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a radio communication system having a configuration in which a radio base station and a center station are connected using a multilink communication scheme.
In FIG. 1, a radio base station 100 is connected to a center station apparatus 200 via a wired line such as T1, E1. The center station apparatus 200 has a line aggregation apparatus that accommodates a line from the radio base station 100. When the signal received via the radio base station 100 is an IP packet, the center processing apparatus 200 and the packet switching apparatus 230 To the IP network. In the case of normal voice data, it is sent to the public telephone network via the voice processing device 240 and the circuit switching device 250.
In the wireless communication system as shown in FIG. 1, when the number of subscribers accommodated in the wireless base station increases, the amount of data or traffic between the wireless base station and the center station increases accordingly. In order to flexibly cope with such an increase or decrease in data amount or traffic, a multilink communication method is used in which a bundle of a plurality of lines is treated as a virtual single line. A typical multilink communication method is the multilink point-to-point protocol (Multilink PPP). Multilink PPP will be described with reference to FIG.

FIG. 2 is a diagram illustrating a configuration for performing data transmission in Multilink PPP.
The endpoint 1 in FIG. 2 corresponds to the line interface portion on the radio base station 100 side in FIG. 1, and the endpoint 2 corresponds to a part of the line aggregation device 210 of the center station apparatus 200. The member link control units 301 to 303 and 311 to 313 are provided corresponding to each physical line, and each independently performs PPP parameter negotiation, PPP link establishment, and PPP link existence confirmation.

  The multilink control unit is configured to bundle a plurality of member links into a bundle and handle it as a virtual single line. The distribution unit divides a frame to be transmitted in a bundle into fragment size units, assigns a sequence number to each fragment data, and sequentially distributes to each member link control unit. Here, the fragment size unit is the maximum transmission unit that can be transmitted by the network. In addition, the combining unit combines the fragment data received from each member link based on the sequence number assigned on the transmission side, always checks the consistency of the sequence number, and detects an abnormality in its continuity. Then, processing to discard the combined frames is performed.

  In addition, each of the multilink control units 304 and 314 is controlled independently between the end point 1 and the end point 2 facing each other. With this Multilink PPP, it is possible to respond flexibly even if the data amount or traffic between the radio base station 100 and the center station apparatus 200 increases or decreases. Further, even when physical lines are added or removed, a plurality of physical lines between the radio base station 100 and the center station apparatus 200 can be handled as a virtual single bundle, which can be flexibly handled. it can. In addition, each member link control unit 301 to 303, 311 to 313 has a function of automatically responding to a physical line failure through PPP link existence confirmation.

  As described in the section of the problem to be solved by the invention, in the normal multilink communication system, when a failure occurs in each physical line constituting the bundle, the failure detection is performed independently at each endpoint. Therefore, the end points 300 and 310 at both ends of the physical line are temporarily not matched, and a mismatched state occurs. Frames transmitted during such an inconsistent state cannot be combined, resulting in discarding by the combining units 304 and 314.

Two methods for detecting a failure in each physical line constituting the bundle will be described.
The first method is PPP link existence confirmation. On each member link, periodic health check frames are sent to and received from opposite endpoints. When no more is received, it is determined that there is a member link failure. In the example of Multilink PPP, each of the member link control units 301 to 303 and 311 to 313 periodically transmits an LCP Echo Request frame to the opposite endpoint, and monitors an LCP Echo Reply that is a response from the opposite endpoint. When the LCP Echo Reply is not received for a certain period or longer, it is determined that the member link has failed, the PPP link is disconnected, and the LCP Echo Reply is reported to the multilink control units 304 and 314 in its own endpoint.

  This method has a problem that it takes time to detect a member link failure and remove it from the bundle. Normally, the transmission interval of health check frames is in seconds, and the transmission interval of LCP Echo Request in Multilink PPP is a minimum of 1 second. Considering the protection time for monitoring the reception of the health check frame, a time of several seconds elapses before the failed member link is removed from the bundle. Multilink PPP usually requires 3 to 5 seconds. Furthermore, since the multilink control unit of each endpoint operates independently, it is impossible to combine the fragment data to the original frame until the member links that make up the bundle match exactly at both endpoints. In this inconsistent period, frame discard occurs. In the example of Multilink PPP, although it depends on the parameter settings, communication interruptions of up to about 10 seconds will occur.

  In order to prevent such a long interruption of communication, it is necessary to suppress the communication interruption to a short period as much as possible. Although the method of shortening the health check frame transmission interval by each member link control unit and shortening the detection time of the member link failure can be considered, this method has another problem that the bandwidth is consumed by transmission of control data. Create points.

  The other method uses a failure detection means of the physical layer. For example, in T1 which is one of the physical layer standards, failure detection means such as LOS and LOF and alarm transfer means such as AIS and RAI are provided. LOS, LOF, AIS, and RAI are circuit information obtained by executing commands, LOS is the number of loss of signal conditions, LOF is the number of loss of frame conditions, AIS is the number of alarm indication signals, and RAI is a remote alarm. Information about the number of indications.

  Since the failure detection means by the physical layer can be normally performed in about several milliseconds, according to this method, it is possible to detect a failure in the physical line in a short time. However, as shown in FIG. 3, this method depends on the type of the physical layer or the operation method and setting of the relay transmission apparatus, and is not always effective. Therefore, when the failure detection means possessed by the physical layer cannot be used, the failure detection method based on the PPP link existence confirmation, which is the first method, must be used.

Next, the configuration of the present invention will be described with reference to FIGS.
FIG. 4 is a configuration diagram between apparatuses that perform data transmission using the multilink communication system according to the present invention.
Here, as an example, a multilink communication system is assumed in which the end point 400 and the end point 410 are connected by three physical lines 421/431, 422/432, and 423/422. Here, it is assumed that communication between each of the end points 400 and 410 has already been established for each member link, and the bundle is already configured by three member links. When the endpoint 400 transmits a frame, the multilink control unit 404 divides the frame into predetermined fragment units, generates fragment data, and performs a distribution process. By the distribution function, the fragment data is sequentially transmitted to the member link control units 401, 402, and 403. At that time, the multilink control unit 414 assigns a sequence number to each fragment data in accordance with the generation order of the fragment data. Fragment data distributed to each member link is received by the opposing end point 410 via an arbitrary number of transmission apparatuses 440. In the receiving end point 410, the member link control units 411, 412 and 413 perform the reception processing of the respective fragment data. The reception process includes frame header synchronization and transmission error detection. Each of the receiving-side member links passes the successfully received fragment data to the multilink control unit 414, and the multilink control unit 414 performs fragment combining processing based on the sequence number assigned to each fragment data. To do.

  The establishment of each member link and the configuration of the bundle take the following procedure. When the member link control unit 401 of the end point 400 detects that the physical line 421 is usable, the member link control unit 401 transmits a member link establishment message to the member link control unit 411 of the opposite end point 410. Similarly, when the member link control unit 411 of the end point 410 detects that the physical line 431 is usable, it transmits a member link establishment message to the member link control unit 401 of the opposite end point 400. After the member link control unit 401 and the member link control unit 411 receive each other's member link establishment message, parameter negotiation for member link operation is performed as necessary, and member links are established on both sides. In addition, the member link establishment message includes a number or identifier that can uniquely identify the member link, and thereafter, the multilink control units 404 and 414 can uniquely identify each member link. After the communication on the member link is established, the member link notifies the multilink control unit in its own endpoint, and the multilink control unit configures the bundle by sequentially incorporating the established member links into the bundle.

Hereinafter, Example 1 of the present invention will be specifically described with reference to FIGS. 4 and 5.
Example 1 is an example of a multilink bundle control method when a failure occurs in a member link.
Since the configuration of FIG. 4 and the operation of each element have been described above, a description thereof will be omitted.
FIG. 5 is a flowchart of an operation when a failure occurs in the physical line 431 directly connected to the end point 410 as an example.
The member link control unit 411 detects that a failure has occurred in the physical line 431 by the failure detection means of the physical layer (step 501). Along with this, the multilink control unit 414 of the end point 410 quickly removes the physical line 431 from the bundle (step 502). However, since an arbitrary number of transmission apparatuses are deployed between the opposite end points and the physical layer type in the middle of the transmission path is different, or because there is no alarm transfer capability of the physical layer, the end point 400 In the member link control unit 401, the same physical layer failure detection means cannot be used. The multilink control unit 414 of the end point 410 transmits bundle configuration information using one or both of the member links 431 and 433 in which no failure has occurred (steps 503 and 504).

FIG. 6 is a diagram illustrating an example of bundle configuration information.
The bundle configuration information includes the identifiers of all the member links that should form the bundle, and does not include the identifiers of the member links that should be removed from the bundle.
In the endpoint 400, the bundle is reconfigured using only the member link whose member link identifier is included in the received bundle configuration information, and the member link whose member link identifier is not included in the bundle configuration information is immediately Remove from the bundle (step 505). Thereby, communication is continued using the bundle comprised by either one or both of the member link 431 and the member link 433 in both the endpoints 410 and 400. When bundle configuration information is received, the bundle is immediately reconfigured by reflecting the information regardless of which member link control unit has received the bundle configuration information. On the bundle configuration information transmission side, exactly the same information is transmitted via a single or multiple member links in which no failure has occurred, so depending on the delay difference of the transmission path that constitutes each member link, It is conceivable to receive duplicates. However, since the transmission side only transmits the same information to each member link in duplicate, the information is immediately reflected based on the bundle configuration information that can be received earliest.

  Specifically, a table for storing bundle configuration information is prepared in the multilink control unit, and if the same bundle configuration information is received later, whether the process is terminated without writing to the table. Only writing to the table is performed, and the flow shown in FIG. 5 is not performed. The table and storage unit for storing the bundle configuration information may not be in the multilink control unit.

  With the above method, when a failure occurs in a line, the bundle configuration state at both endpoints can be quickly synchronized, and communication disconnection can be suppressed in a short time.

Next, a second embodiment of the present invention will be specifically described with reference to FIGS. 4 and 7.
The operation when a failure occurs in the member link is the same as in the first embodiment. In the second embodiment, a multilink bundle control method when a member link is established and when a member link failure is recovered will be described.

  The member link establishment method is as described above. The member link establishment message is transmitted and received between the opposing member link control units, and parameter negotiation for member link operation is performed as necessary. Establish. Each time a new member is established, the multilink control unit transmits bundle configuration information using all member links that constitute the bundle, including its own member link (steps 701, 702, 703, 704, 705). 706).

FIG. 8 shows an example of bundle configuration information.
The bundle configuration information includes the identifiers of all the member links that should form the bundle, and does not include the identifiers of the member links that should be removed from the bundle. Further, the bundle configuration information may include the priority and bandwidth of each member link. Alternatively, it may include an effective band that takes into account the delay time of each member link and the transmission error rate measured by a separate means.

  The opposing endpoint confirms that the bundle is configured using only the member link whose member link identifier is included in the received bundle configuration information, and if there is a difference, the received bundle configuration information Reconfigure the bundle based on it. When the received bundle configuration information includes the priority and band for each member link, fragment data distribution control is performed based on the priority and band information. Alternatively, priority and bandwidth information may be used after each member link is multiplied by a predetermined weight.

  Note that when the initial member link is established, if the bundle information is transmitted immediately, the member link established immediately after cannot be reflected in the bundle information, and there is a possibility that the member link establishment and removal may be repeated. It is desirable to provide a certain delay between establishment and bundle configuration information transmission.

  The case where the member link failure is recovered is the same as the case of the member link establishment. When the member link control unit detects the recovery of the line failure and the member link is reestablished, the bundle configuration information is transmitted using all the member links constituting the bundle including the self member link ( Steps 707, 708, 709). The bundle configuration information includes all member link identifiers that should constitute the bundle, including the member links that have recovered from the failure. Similarly, the bundle configuration information may include the priority and bandwidth of each member link. Alternatively, it may include an effective band that takes into account the delay time of each member link and the transmission error rate measured by a separate means.

  With the above method, when a failure occurs in a line, the bundle configuration state at both endpoints can be quickly synchronized, and communication disconnection can be suppressed in a short time. In addition, when a new member link is established or when a member link failure is recovered, it is possible to reliably synchronize the bundle configuration state at both endpoints. By using quality measurement results such as priority and bandwidth, or delay time and effective bandwidth, it is possible to perform advanced multilink distribution control.

It is a figure explaining the radio | wireless communications system with which the radio base station and the center station were connected using the multilink communication system. It is a figure explaining the structure for performing the data transmission in Multilink PPP. It is a figure for demonstrating the subject in the conventional multilink communication system. It is a block diagram for demonstrating the multilink communication system of Example 1. FIG. 4 is a flowchart illustrating an operation of an endpoint when a line failure is detected in the first embodiment. It is a figure which shows the example of bundle structure information in Example 1. FIG. 4 is a flowchart illustrating the operation of an endpoint when a member link is established, a line failure is detected, and a line failure is recovered in the first embodiment. It is a figure which shows the example of bundle structure information in Example 2. FIG.

Explanation of symbols

400, 410 End points 401, 402, 403, 411, 412, 413 Member link control unit 404, 414 Multilink control unit and distribution unit, and 421, 422, 423, 431, 432, 433 Physical lines constituting the multilink bundle

Claims (10)

Data in which the transmission side data transmission device and the reception side data transmission device are connected by a plurality of physical lines, a link formed by the plurality of physical lines is configured as a bundle, and communication is performed using the multilink communication method as a virtual one link. A data transmission apparatus in a transmission system, wherein each of the plurality of physical lines is accommodated, and a plurality of member link control units for controlling link establishment and link release by the physical lines, and the plurality of member link control units And when transmitting data, the transmission data is divided into fragment data of a size that can be transmitted on the physical line, a number is assigned to the divided fragment data and distributed to the plurality of member link control units. The fragment data received via the physical line is added by the data transmission device on the sending side. And a multilink control unit for confirming the consistency of the number, and the multilink control unit establishes the link using an identifier that can uniquely identify the plurality of physical lines. Bundle information including the identifiers of all physical lines with established links, which is information relating to link establishment and release of the plurality of physical lines using the identifiers. The multilink control unit in the transmission side data transmission device stores the physical line from the bundle and establishes a link or links when a failure occurs in any of the plurality of physical lines. after the establishment of the performing time release and links, and transmitting the bundle information via at least one physical line has been established link The multi-link control unit in the data transmission apparatus of the counterpart reconstructs bundle on the basis of the bundle information received, the transmission side data transmission device, both of the receiving side data transmission device, characterized in that to match the bundle configuration A data transmission device. 2. The data transmission apparatus according to claim 1, wherein at the time of establishing the link, the bundle information is transmitted after a predetermined delay time has elapsed after the establishment of the link.   An attribute of each physical line is stored in the storage unit in association with an identifier of the physical line with which the link is established, and the multilink control unit distributes fragment data based on the attribute. The data transmission apparatus according to claim 1.   4. The data transmission apparatus according to claim 3, wherein the attribute of the physical line is a priority for each physical line, information on an allocated band, a delay, or a transmission error rate. The transmission side and the reception side are connected by a plurality of physical lines, and at the time of data transmission, the transmission data is divided into fragment data of a size that can be transmitted by the physical line, and a number is assigned to the divided fragment data, and the plurality of physical lines And by combining the fragment data received via the plurality of physical lines based on the number assigned on the transmission side and confirming the consistency of the numbers, the links of the plurality of physical lines are bundled A data transmission method configured to perform communication by regarding it as a virtual one link, and performing establishment of the link and release of the link by using an identifier capable of uniquely identifying the plurality of physical lines; established in which the physical link is information relating to establishment and release of a link of said plurality of physical lines using the identifier Stores the bundle information including a line all the identifiers, multilink control unit in the transmission side data transmission device, when a failure in any one of the plurality of physical lines occurs, removing the physical line from the bundle The multi-link control unit in the opposing data transmission apparatus transmits the bundle information via at least one physical line with which the link is established each time the link is established or the link is released and after the link is established. A data transmission method characterized in that a bundle is reconfigured based on the received bundle information and the bundle configuration is matched in both the transmission side data transmission apparatus and the reception side data transmission apparatus . The bundle information including the identifiers of all the physical lines with which the link is established is transmitted when a link is established, after a predetermined delay time has elapsed after the link is established. Data transmission method.   6. The data according to claim 5, wherein an attribute of each physical line is stored in association with an identifier of the physical line with which the link is established, and fragment data is distributed based on the attribute. Transmission method.   8. The data transmission method according to claim 7, wherein the attribute of the physical line is a priority for each physical line, information on an allocated band, a delay, or a transmission error rate. The data transmission device on the transmission side and the data transmission device on the reception side are connected by a plurality of physical lines, a link formed by these physical lines is configured as a bundle, and communication is performed using the multilink communication method as a single virtual link. A data transmission system for performing transmission, wherein the transmission side and reception side data transmission devices accommodate each of the plurality of physical lines, and control a plurality of member link control units for establishing a link and releasing the link by the physical line Connected to the plurality of member link control units, and at the time of data transmission, the transmission data is divided into fragment data having a size that can be transmitted through the physical line, and the divided fragment data is assigned a number to the plurality of member links. In addition to allocating to the control unit, the fragment data received via the plurality of physical lines A multi-link control unit that combines based on the number assigned by the data transmission device and checks the consistency of the number, and the multi-link control unit has an identifier that can uniquely identify the plurality of physical lines. The link establishment and link release control is performed using the identifier, and the identifiers of all physical lines with established links, which are information relating to link establishment and release of the plurality of physical lines, are used. storing bundle data in a storage unit including a keep, multilink control unit in the transmission side data transmission device, when a failure in any one of the plurality of physical lines occurs, thereby removing the physical line from the bundle , after time and link establishment to perform establishment or unlink link before via at least one physical line that has been established for the link The multi-link control unit in the opposing data transmission device transmits the bundle information, reconfigures the bundle based on the received bundle information, and bundles both in the transmission side data transmission device and the reception side data transmission device. A data transmission system characterized by being a data transmission device having a matching configuration . The opposing data transmission apparatus releases the link for the physical line not included in the received physical line of the link and stores the bundle information including the received physical line of the link in the storage unit. 10. The data transmission system according to claim 9, wherein by storing, the information on the physical line with which the link is established is matched in both the transmission side data transmission apparatus and the reception side data transmission apparatus.

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