QUIC-based multipath data transmission method and device, and storage medium

Abstract

The invention discloses a QUIC-based multi-path data transmission method and device and a storage medium, and belongs to the technical field of data transmission. The method comprises the following steps: packaging data to be transmitted into at least one data frame, and distributing a data packet sequence number for the data frame in a connection level packet sequence number space; selecting a target transmission path from the data transmission paths, generating a data packet, sending the data packet to a receiving end through the target transmission path, and recording a data packet sending record; and receiving an acknowledgement frame fed back by the receiving end, and determining a data packet to be retransmitted according to the acknowledgement frame and a data packet sending record. Based on the characteristic that the serial number of the connection-level data packet is monotonically increased, the to-be-retransmitted data packet is determined according to the acknowledgement frame, and a serial number packet space does not need to be allocated to each path, so that the coupling degree of data transmission is reduced, the retransmission efficiency is improved, RTT is calculated according to the acknowledgement frame, the link condition is evaluated, a reasonable sending speed is obtained, and the transmission efficiency is improved. The effect that any path is reliable in transmission is achieved.

Description

Technical Field

[0001] The present application relates to the field of data transmission technology, and in particular to a QUIC-based multipath data transmission method, device, and storage medium. Background Art

[0002] The QUIC protocol based on the User Datagram Protocol (UDP) is a secure and efficient transmission protocol that has zero round-trip time (RTT) and fast handshake, solves head-end blocking, and runs in user mode. QUIC has multiple spaces, and the data packets in each space are assigned a monotonically increasing sequence number. The sender and receiver based on the QUIC protocol will determine whether there is packet loss based on the sequence number of the data packet, and retransmit the lost data packets to ensure the reliability of data transmission.

[0003] In related technologies, in order to achieve reliable multi-path transmission of data, the QUIC protocol can allocate separate data packet sequence number spaces for different paths, calculate the data packet sequence numbers in each data packet sequence number space separately, and perform data packet retransmission when judging data packet loss based on the data packet sequence number, as well as feedback on the congestion control algorithm indicators of the path, including the impact of indicators such as RTT, packet loss rate, congestion window, and transmission speed. In this case, each data packet sequence number space needs to be managed separately during the data transmission process, and the data transmission status of the path is fed back separately by introducing an extended special confirmation frame. This will make the coupling degree of multi-path data transmission higher, resulting in lower efficiency of data retransmission.

[0004] The above contents are only used to assist in understanding the technical solution of the present application and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The main purpose of this application is to provide a QUIC-based multipath data transmission method, device and storage medium, aiming to solve the technical problem that the coupling degree of QUIC-based multipath data transmission is high, resulting in low efficiency of data retransmission and path congestion control feedback.

[0006] To achieve the above object, the present application provides a QUIC-based multipath data transmission method, which is applied to a sending end, and the method comprises the following steps: Encapsulating the data to be transmitted into at least one data frame, and assigning a monotonically increasing data packet sequence number to the data frame in a connection-level packet sequence number space; Selecting a target transmission path in the data transmission path, and generating a data packet according to the data frame, the data packet sequence number and / or the target transmission path; Sending the data packet to a receiving end through the target transmission path, and recording a data packet sending record of the target transmission path; Receive the confirmation frame fed back by the receiving end, and determine the data packet to be retransmitted according to the confirmation frame and the data packet sending record.

[0007] In one embodiment, the step of receiving the confirmation frame fed back by the receiving end and determining the data packet to be retransmitted according to the confirmation frame and the data packet sending record includes: receiving the confirmation frame, and obtaining a receiving sequence number sequence of the target transmission path in the confirmation frame; Obtaining a sending sequence number sequence of the data packet in the data packet sending record; In the packet loss determination range, the sending sequence number sequence is compared with the receiving sequence number sequence, and the data packet to be retransmitted is determined according to the comparison result.

[0008] In one embodiment, the step of comparing the sending sequence number sequence with the receiving sequence number sequence within the packet loss determination range and determining the data packet to be retransmitted according to the comparison result comprises: Determine a target sequence number sequence of the sending sequence number sequence within the packet loss determination range based on a preset retransmission threshold parameter and a maximum packet sequence number in the sending sequence number sequence; Determine the missing data packet sequence numbers of the received sequence number sequence and the target sequence number sequence by comparing the target sequence number sequence and the received sequence number sequence; Determining the data packet to be retransmitted according to the missing data packet sequence number; The data to be retransmitted in the data packet to be retransmitted is obtained, and the data to be retransmitted is added to the data to be transmitted.

[0009] In one embodiment, after the step of receiving the confirmation frame and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame, the method further includes: In the confirmation frame, determining the maximum packet sequence number of the received sequence number sequence; In the data packet sending record, determining the sending time of the target data packet with the maximum packet sequence number; The round trip delay of the target data packet is calculated according to the sending time and the receiving time of the confirmation frame.

[0010] In one embodiment, after the step of calculating the round trip delay of the target data packet according to the sending time and the receiving time of the confirmation frame, the method further includes: Determining the congestion degree of the target transmission path according to the round-trip delay, the received sequence number sequence and the data packet to be retransmitted; Calculate and adjust the sending speed and congestion window of the data packet of the target transmission path according to the congestion degree; Based on the sending speed and the congestion window, the target transmission path is controlled to perform a data packet sending action.

[0011] In one embodiment, the step of receiving the confirmation frame and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame includes: After receiving the confirmation frame fed back by the receiving end, reading the reception confirmation information in the confirmation frame; According to the reception confirmation information, obtaining the target data packet sequence number; The target data packet sequence numbers are sorted based on the sequence number sizes, and the receiving sequence number sequence is determined according to the sorting results.

[0012] In one embodiment, the step of selecting a target transmission path in the data transmission path and generating a data packet according to the data frame, the data packet sequence number and / or the target transmission path comprises: Encrypting the data frame to generate an encrypted data frame; Selecting the target transmission path in the data transmission path, generating the data packet sequence number and metadata of the target transmission path, and constructing a header file of the data packet according to the metadata; The data packet is generated by combining the header file and the encrypted data frame.

[0013] In addition, to achieve the above objectives, the present application also provides a QUIC-based multipath data transmission method, which is applied to a receiving end, and the method comprises the following steps: Receive a data packet sent by a sender, and determine a data packet sequence number and a target transmission path of the data packet; Obtaining a target data packet sequence number received by the target transmission path and reception confirmation information corresponding to the target data packet sequence number; Generate a confirmation frame according to the maximum packet sequence number in the target data packet sequence number and the reception confirmation information; Feedback the confirmation frame to the sending end.

[0014] In addition, to achieve the above-mentioned objectives, the present application also provides a QUIC-based multipath data transmission device, the device comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, the computer program being configured to implement the steps of the QUIC-based multipath data transmission method as described above.

[0015] In addition, to achieve the above-mentioned purpose, the present application also provides a storage medium, which is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by the processor, the steps of the QUIC-based multipath data transmission method as described above are implemented.

[0016] One or more technical solutions proposed in this application have at least the following technical effects: The present application encapsulates the data to be transmitted into at least one data frame, allocates a monotonically increasing data packet sequence number to the packet in the data frame through the connection-level packet sequence number space of the data to be transmitted, selects a target transmission path in the data transmission path, generates a data packet according to the data frame, the data packet sequence number and / or the target transmission path, sends the data packet to the receiving end through the target transmission path, records the data packet sending record of the target transmission path, receives a confirmation frame fed back by the receiving end, and determines the data packet to be retransmitted according to the confirmation frame and the data packet sending record, so that in the multi-path data transmission process based on QUIC, the data packet sequence number is allocated to the data packet through the connection-level packet sequence number space, and the data packet sending record of each path is recorded separately according to the monotonically increasing characteristic of the data packet sequence number of the data packet received on each path, without allocating a separate data packet sequence number space for each path, thereby reducing the coupling degree of data transmission and improving the efficiency of data packet retransmission in the process of realizing multi-path reliability transmission. In addition, the present application calculates the round-trip time (RTT) of the path based on the maximum data packet sequence number of the confirmation frame. It is also very important to calculate the effective transmission volume and packet loss rate that the path can carry based on the confirmation information, so as to measure the properties of the path in a reasonable and standard manner, and evaluate the congestion condition of the path accordingly, and obtain a reasonable sending speed on the path, thereby achieving the effect that any path can independently control reliable transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0019] Figure 1 This is a flowchart of the first embodiment of the multi-path data transmission method based on QUIC of the present application; Figure 2This is a flowchart of the second embodiment of the multi-path data transmission method based on QUIC of the present application; Figure 3 This is a schematic diagram of a retransmission parameter threshold involved in the second embodiment of the QUIC-based multipath data transmission method of the present application; Figure 4 This is a flowchart of the third embodiment of the QUIC-based multipath data transmission method of the present application; Figure 5 This is a flowchart of the fourth embodiment of the QUIC-based multipath data transmission method of the present application; Figure 6 This is a brief flowchart of the multi-path data transmission method based on QUIC in this application; Figure 7 It is a structural diagram of a QUIC-based multi-path data transmission device in the hardware operating environment involved in the embodiment of the present application.

[0020] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0023] The main solution of the embodiment of the present application is: encapsulate the data to be transmitted into at least one data frame, and establish a connection-level packet sequence number space for the data to be transmitted; in the connection-level packet sequence number space, assign a monotonically increasing data packet sequence number to the data frame, and select a target transmission path in the data transmission path; generate a data packet according to the data frame, the data packet sequence number and / or the target transmission path; send the data packet to the receiving end through the target transmission path, and record the data packet sending record of the target transmission path; receive a confirmation frame fed back by the receiving end, and determine the data packet to be retransmitted based on the confirmation frame and the data packet sending record.

[0024] In the related art, the Quick UDP Internet Connection Protocol (QUIC) based on the User Datagram Protocol (UDP) can assign a monotonically increasing sequence number to each data packet. The sender and receiver based on the QUIC protocol will determine whether there is packet loss based on the sequence number of the data packet, and retransmit the lost data packet to ensure the reliability of data transmission. Among them, in order to achieve multi-path reliable transmission of data, the QUIC protocol can allocate separate data packet sequence number spaces for different paths, calculate the data packet sequence numbers in each data packet sequence number space separately, and perform data packet retransmission when the data packet is judged to be lost based on the data packet sequence number. In this case, each data packet sequence number space needs to be managed separately during the data transmission process, and the data transmission status of the path is fed back separately by introducing an extended special confirmation frame. This will make the coupling degree of multi-path data transmission higher, resulting in lower efficiency of data retransmission. In addition, the separately added packet sequence number space will make the data transmission process complicated and difficult to implement, and it cannot be connected with the standard QUIC protocol, and the compatibility and scalability are low, making it difficult to popularize.

[0025] The present application encapsulates the data to be transmitted into at least one data frame, allocates a monotonically increasing connection-level data packet sequence number to the data frame through the connection-level packet sequence number space of the data to be transmitted, selects a target transmission path in the data transmission path, generates a data packet according to the data frame, the data packet sequence number and the target transmission path, sends the data packet to the receiving end through the target transmission path, records the data packet sending record of the target transmission path, receives a confirmation frame fed back by the receiving end, and determines the data packet to be retransmitted according to the confirmation frame and the data packet sending record, so that in the multi-path data transmission process based on QUIC, a data packet sequence number is allocated to the data packet through the connection-level packet sequence number space, and according to the monotonically increasing characteristic of the data packet sequence number of the data packet received on each path, the data packet sending record of each path is recorded separately without allocating a separate data packet sequence number space for each path, thereby reducing the coupling degree of data transmission and improving the efficiency of data packet retransmission in the process of realizing multi-path reliability transmission. In addition, the present application calculates the round-trip time (RTT) of the path based on the maximum data packet sequence number of the confirmation frame. It is also very important to calculate the effective transmission volume and packet loss rate that the path can carry based on the confirmation information, so as to measure the properties of the path in a reasonable and standard manner, and evaluate the congestion condition of the path accordingly, and obtain a reasonable sending speed on the path, thereby achieving the effect that any path can independently control reliable transmission.

[0026] In order to better understand the above technical solution, exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0027] It should be noted that the execution subject of this embodiment can be the sending end and receiving end of data transmission, or a computing service device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or an electronic device that can realize the above functions, a QUIC-based multi-path data transmission device, etc., which is not specifically limited in this embodiment. The following takes the sending end and receiving end of data transmission as an example to illustrate this embodiment and the following embodiments.

[0028] Based on this, the embodiment of the present application provides a multi-path data transmission method based on QUIC, which is applied to the sending end, referring to Figure 1 , Figure 1 This is a flowchart of the first embodiment of the multi-path data transmission method based on QUIC in the present application.

[0029] In this embodiment, the QUIC-based multipath data transmission method includes steps S110 to S150: Step S110: encapsulating the data to be transmitted into at least one data frame, and assigning a monotonically increasing data packet sequence number to the data frame in the connection-level packet sequence number space; Step S120: selecting a target transmission path in the data transmission path, and generating a data packet according to the data frame, the data packet sequence number and / or the target transmission path; It should be noted that the Quick UDP Internet Connections (QUIC) protocol is a transport layer protocol based on the User Datagram Protocol (UDP). It aims to provide reliable transmission services similar to the Transmission Control Protocol (TCP) through UDP, avoiding TCP's three-way handshake and congestion control problems, and solving the delay and head-end congestion control problems of the traditional TCP protocol. The QUIC protocol has the characteristics of built-in encryption and multiplexing. It also uses a connection ID to identify the connection, and includes the connection ID, packet number, encryption information, etc. in the data packet to ensure the security and reliable transmission of the data packet. Among them, the QUIC protocol is based on a fast connection establishment mechanism, which allows clients that have previously established a connection with the server to skip part of the handshake process when reconnecting, thereby significantly reducing the time required to establish a connection.

[0030] In this embodiment, the connection level is the data transmission and management performed based on the various spaces including the Initial space, Handshake space, and Data space of a single QUIC connection during the data transmission process of the QUIC protocol. The sender establishes each packet sequence number space at the connection level based on a single connection with the receiver. When the sender determines the data to be transmitted and sends the data to be transmitted to the receiver based on the QUIC protocol, the data to be transmitted will be encapsulated into multiple data frames, and after generating data packets respectively, they will be transmitted through different data transmission paths.

[0031] It should be noted that when encapsulating and sending a data packet, the sender will assign a data packet sequence number to the data packet in the packet sequence number space of the same level in the connection level based on a continuous monotonically increasing manner. Among them, each time a data packet is sent, the data packet sequence number of the next data packet of the same level will increase by one.

[0032] In one embodiment, a data packet includes two parts: a header file and an encrypted data frame. The header file contains metadata of data such as a target transmission path and a data packet sequence number. The encrypted data frame is generated by splitting the data to be transmitted and encapsulating it into a data frame and then encrypting it, which is the information actually transmitted by the encrypted data packet. After obtaining the data to be transmitted, the receiving end can segment the data to be transmitted, and after encapsulating each segment of the segmented data into a data frame, encrypt and generate an encrypted data frame, thereby generating multiple data packets based on the data to be transmitted. The encrypted data frame is assigned a target transmission path and a data packet sequence number at the same level of the connection level, and the data packet sequence number and metadata of the target transmission path are generated. A header file is constructed according to the source data, and the header file is combined with the encrypted data frame to generate a data packet.

[0033] In addition, the sending end is also equipped with a content manager. Through the content manager, the sending end can segment the data to be transmitted, determine the content of each data packet, and encapsulate the segmented data segments into data frames. And when the data packet is lost, it only needs to feedback the loss of the content in the data packet to the content manager, which will mark it as "lost" so that the "lost" content will be retransmitted first when sending data packets on any path next time.

[0034] Step S130: sending the data packet to the receiving end through the target transmission path, and recording the data packet sending record of the target transmission path; In this embodiment, in order to improve the stability and efficiency of data transmission, there are multiple links for data transmission, i.e., data transmission paths, between the sender and the receiver. The sender can send data packets to the receiver through multiple data transmission paths at the same time based on the QUIC protocol and multi-path transmission.

[0035] In one embodiment, based on different data transmission paths, the sending end is provided with different path managers. Among them, the path manager corresponds to the data transmission path one by one, and can implement management actions such as congestion control, selection, and scheduling of the data transmission path. When the sending end sends a data packet through the QUIC protocol, it can obtain or generate metadata of the target transmission path based on the path manager of the target transmission path. The metadata includes a four-tuple, namely, source IP, source port, target IP, and target port. While sending the data packet, the path manager will associate and save the data packet sent by the target transmission path, as well as the connection-level data packet sequence number and sending time, thereby recording the data packet sending record. The path manager is used to maintain the path four-tuple, RTT, congestion window, packet sending record and other information.

[0036] Furthermore, the path manager may use the data packet sequence number as a primary key to save the data packet sending record into a database, wherein the data packet sequence numbers of the sorted data packet sending records are arranged based on size to form a sending sequence number sequence of the data packets.

[0037] For example, when the tenth data packet of the data to be transmitted is sent, the sender will assign the data packet a connection-level data packet sequence number of 10 in the connection-level packet sequence number space. Then, according to the congestion of the data transmission path, a target transmission path numbered 1001 is selected for the data packet. The path manager can associate the target transmission path number 1001 and the data packet sending time with the data packet sequence number 10, and save them in the database at the last digit of the data packet sending record of the data packet sequence number 09.

[0038] Optionally, in the path manager, the metadata of the target path can be used to guide the data packet to be transmitted on the target transmission path. During the transmission process, the data packet will pass through multiple link nodes. Among them, when the link node receives the data packet, it will read the information of the header file in the data packet, determine the target transmission path for transmitting the data packet, and the next link node of the target transmission path, so as to transmit the data packet based on the target transmission path.

[0039] Step S140: receiving a confirmation frame fed back by the receiving end, and determining the data packet to be retransmitted according to the confirmation frame and the data packet sending record.

[0040] It should be noted that in order to avoid packet loss during data transmission, the data transmission process can use a packet loss retransmission mechanism to ensure that the data to be transmitted can be sent to the receiving end intact. Based on the packet loss retransmission mechanism, the receiving end can generate an acknowledgment frame (ACK) based on the received data packet and feed the acknowledgment frame back to the sending end. The sending end can use the acknowledgment frame to promptly retransmit the data packet when it is determined that the data packet is lost, thereby ensuring the reliability of data transmission.

[0041] In this embodiment, ACK includes but is not limited to the maximum packet sequence number, the Delay field, and the reception confirmation information of the data packet. The maximum packet sequence number is the largest data packet sequence number received by the receiving end based on the target transmission path. The confirmation frame is filled with the Largest Acknowledged field as the largest packet sequence number and the Delay field used to indicate the delayed confirmation of the largest packet sequence number, and is also accompanied by the reception confirmation information of the data packets whose sequence numbers are connected before the maximum packet sequence number.

[0042] Specifically, the sender receives confirmation information, compares the sequence numbers of the data packets received by the receiver and the sequence numbers of the data packets sent by the sender, and determines which data are lost after obtaining the sequence numbers of the missing data packets, and then marks them as "need to be retransmitted" in the content manager.

[0043] The embodiment of the present application encapsulates the data to be transmitted into at least one data frame, establishes a packet sequence number space for each connection-level space of the data to be transmitted, assigns a monotonically increasing data packet sequence number to the data frame in each connection-level packet sequence number space, selects a target transmission path in the data transmission path, generates a data packet according to the data frame, the data packet sequence number and the target transmission path, sends the data packet to the receiving end through the target transmission path, records the data packet sending record of the target transmission path, receives a confirmation frame fed back by the receiving end, and determines the data packet to be retransmitted according to the confirmation frame and the data packet sending record, so that in the multi-path data transmission process based on QUIC, a data packet sequence number is assigned to the data packet through the connection-level packet sequence number space, and according to the monotonically increasing characteristic of the data packet sequence number of the data packet received on each path, the data packet sending record of each path is recorded separately without allocating a separate data packet sequence number space for each path. In the process of realizing multi-path reliability transmission, the coupling degree of data transmission is reduced and the efficiency of data packet retransmission is improved.

[0044] Based on the same inventive concept, the present application also provides a second embodiment, which is applied to the sending end, referring to Figure 2 , Figure 2 This is a flow chart of the second embodiment of the multi-path data transmission method based on QUIC of the present application.

[0045] In this embodiment, the step of receiving the confirmation frame fed back by the receiving end as described in step S150, and determining the data packet to be retransmitted according to the confirmation frame and the data packet sending record includes steps S141 to S143: Step S141: receiving the confirmation frame, and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame; In this embodiment, the receiving sequence number sequence is the sequence number of the data packets received by the receiving end, which is generated based on the size sorting. The sending sequence number sequence is generated by arranging the sequence numbers of the data packets in the data packet sending record recorded by the sending end. Among them, by comparing the receiving sequence number sequence and the sending sequence number sequence, the sending end can determine the data packets lost during the data transmission process.

[0046] As an optional implementation method for obtaining a received sequence number sequence, after receiving a confirmation frame fed back by the receiving end, the transmitting end can read the received confirmation information in the confirmation frame and obtain the target data packet sequence number corresponding to the received confirmation information. By sorting the target data packet sequence numbers based on the sequence number size, the transmitting end can determine the received sequence number sequence according to the sorting result. The received sequence number sequence is the data packet sequence number of the data packet received by the receiving end based on the target transmission path, and is determined according to the size sorting.

[0047] As another optional implementation of obtaining the received sequence number sequence, the receiving end can arrange the data packet sequence numbers based on the size in the process of generating the confirmation frame, generate the received sequence number sequence, and fill it into the confirmation frame. The sending end can also directly obtain the received sequence number sequence in the confirmation frame.

[0048] Step S142: Obtaining the sending sequence number sequence of the data packet in the data packet sending record; Step S143: in the packet loss determination range, compare the sending sequence number sequence with the receiving sequence number sequence, and determine the data packet to be retransmitted according to the comparison result.

[0049] It should be noted that due to out-of-order transmission on the network, the receiving end may first receive the data packets with later sequence numbers, but fail to receive the data packets with earlier sequence numbers. Figure 3 , Figure 3 FIG. 4 is a schematic diagram of the retransmission parameter threshold involved in this embodiment. Figure 3 As shown, when the sender determines based on the confirmation frame that the receiver has received the data packet with data packet number 12 but has not yet received the data packet with data packet number 10, it cannot directly determine that the data packet with data packet number 10 is lost, and the data packet may still be in the transmission process due to disordered transmission in the network.

[0050] In this embodiment, the transmitting end is provided with a retransmission threshold parameter for resisting disordered false retransmission, which is used to determine the packet loss determination range. According to the retransmission threshold parameter, the transmitting end can determine the packet loss determination range based on the order and the maximum packet sequence number of the confirmation frame in the sorting of the sending sequence number sequence of each data transmission path. Among them, when the sending sequence number sequence is sorted from large to small, the transmitting end can first determine the order of the maximum packet sequence number in the sending sequence number sequence, and calculate the order difference between the sequence number of each data packet whose order is less than the maximum packet sequence number and the maximum packet sequence number, and judge that the data packet whose order difference is greater than the retransmission threshold parameter is within the packet loss determination range, and the data packet whose order difference is not greater than the retransmission threshold parameter is outside the packet loss determination range, thereby avoiding the transmitting end from retransmitting the data packet when the data packet is delayed due to disordered transmission, resulting in redundant transmission.

[0051] As an optional implementation, the sender obtains a target sequence number sequence of the send sequence number sequence within the packet loss determination range based on a preset retransmission threshold parameter and the maximum packet sequence number in the confirmation frame. By comparing the target sequence number sequence with the received sequence number sequence, the sender can determine the missing data packet sequence number in the received sequence number sequence compared to the target sequence number sequence, and determine the data packet to be retransmitted based on the missing data packet sequence number.

[0052] In one example, the sending sequence number sequence of the target transmission path is 14, 12, 10, 8, 5, 3, 1. The maximum packet sequence number obtained by the sender through the confirmation frame is 12, and the retransmission threshold parameter is 3. Based on the retransmission threshold parameter, the last three digits of the data packet sequence number 12, namely 10, 8 and 5, have an order difference with the maximum packet sequence number that is not greater than the retransmission parameter threshold, and are outside the packet loss judgment range. However, the order difference between 3 and 1 and the maximum packet sequence number is greater than the retransmission parameter threshold, so they are within the packet loss judgment range and serve as the target sequence number sequence. When the receiving sequence number sequence obtained by the sender is 12, 8, 5, 1, the missing data packet numbers in the receiving sequence number sequence are 10 and 3. Based on the retransmission parameter threshold and / or the packet loss judgment range, it can be determined that the data packet with data packet number 3 is the data packet to be retransmitted.

[0053] Optionally, after determining the data packet to be retransmitted, the sender can obtain the data in the data packet and use it as the data to be retransmitted. The content manager in the sender can obtain and mark the data to be retransmitted, and integrate the data to be retransmitted into the new data packet when arranging a new data packet for transmission next time. The new data packet is different from the data packet to be retransmitted, and the data packet sequence number of the connection level is reallocated.

[0054] The embodiment of the present application can determine the data packet to be retransmitted according to the missing data packet sequence number in the received sequence number sequence by acquiring and comparing the received sequence number sequence and the sent sequence number sequence, so that the sending end can quickly determine the data packet to be retransmitted and retransmit the data. At the same time, the packet loss judgment range is determined by the retransmission parameter threshold to avoid redundant transmission of data.

[0055] Since the system introduced in the second embodiment of the present application is a system used to implement the method of the first embodiment of the present application, based on the method introduced in the first embodiment of the present application, the person skilled in the art can understand the specific structure and deformation of the system, so it is not repeated here. All systems used in the method of the first embodiment of the present application belong to the scope of protection of this application.

[0056] Based on the same inventive concept, the present application also provides a third embodiment, which is applied to the sending end, referring to Figure 4 , Figure 4 This is a flow chart of the third embodiment of the multi-path data transmission method based on QUIC of the present application.

[0057] In this embodiment, after receiving the confirmation frame fed back by the receiving end as described in step S20, and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame, steps S150 to S170 are also included: Step S150: Determine the maximum packet sequence number of the received sequence number sequence in the confirmation frame; Step S160: Determine the sending time of the target data packet with the largest packet sequence number in the data packet sending record; Step S170: Calculate the round trip delay of the target data packet according to the sending time and the receiving time of the confirmation frame.

[0058] In this embodiment, the round-trip time (RTT) refers to the time required for the entire process from the sender sending data to the receiver receiving the data and returning a confirmation signal to the sender, which is used to measure network communication performance. It usually includes sending delay and processing delay.

[0059] In specific implementation, the sender can also determine the maximum packet sequence number based on the Largest Acknowledged field in the confirmation frame, and determine the sending time of the target data packet corresponding to the maximum packet sequence number in the data packet sending record. At the same time, based on the reception time of the confirmation frame and the sending time, the sender can calculate the time required from the sending of the data packet to the receiving of the confirmation frame, and use the time sample as the round-trip delay.

[0060] Specifically, when the receiving end feeds back the confirmation frame to the sending end, it needs to feed back the confirmation frame to the sending end along the target transmission path so that the sending end can reasonably and correctly sample the round-trip delay and subsequently refer to the round-trip delay to evaluate the degree of data link congestion. At the same time, the sending end can determine the data processing time of the receiving end from receiving the data packet to sending the confirmation frame based on the Delay field in the confirmation frame.

[0061] Further, after calculating the round trip delay of the target data packet according to the sending time and the receiving time of the confirmation frame as described in step S180, steps S181-S182 are also included: Step S171: evaluating the congestion degree of the target transmission path according to the round-trip delay, the received sequence number sequence and the data packet to be retransmitted; Step S172: Calculating the sending speed and congestion window of the data packet of the target transmission path according to the congestion degree; Step S173: Based on the sending speed and the congestion window, control and adjust the target transmission path to execute the data packet sending action.

[0062] In this embodiment, when multi-path transmission is adopted, the amount of data to be transmitted is usually huge, and all the paths to be transmitted need to send data with full effort. The path manager can reasonably sample the RTT based on the confirmation frame received by the target path, and calculate the target path indicators such as the effective transmission volume and packet loss rate of the target path, and judge the congestion degree of the corresponding target transmission path on this basis, and calculate the transmission speed and congestion window in the process of sending data packets by the target transmission path. Among them, the transmission speed is the amount of data sent per unit time by the target transmission path. The path manager can control the transmission speed by adjusting the transmission volume of each transmission, that is, the amount of data of the bandwidth-delay product (BDP) of a single transmission. The congestion window reflects the current congestion status of the target transmission path, and its size determines the maximum amount of data that the sender can send without causing network congestion.

[0063] Specifically, each time the sending end receives RTT, the path manager updates the transmission speed of the target transmission path based on the packet loss rate, the transmission volume effectively carried by the path, RTT and other indicators. Among them, the path manager can determine the data packets received by the receiving end based on the received sequence number sequence, and then determine the transmission volume effectively carried by the target transmission path, and calculate the packet loss rate of the target transmission path based on the data packets to be retransmitted and the received sequence number sequence. The path manager can calculate the transmission volume effectively carried by the target transmission path, the packet loss rate and other indicators based on the information in the confirmation frame, and jointly evaluate the congestion degree of the target transmission path based on these indicators.

[0064] Optionally, the path manager can select a target transmission path for the data packet in the data transmission path based on the congestion level and economy. For example, the WiFi data transmission path with the least congestion can be selected as the target transmission path, thereby effectively improving the data transmission efficiency when the data scale is small.

[0065] According to the sending time and receiving time of the largest packet sequence number in the confirmation frame, the embodiment of the present application can sample the round-trip delay of each path in the multi-path, confirm the data packets that have been sent by each path, and judge the packets that may be lost by each path, so as to calculate the round-trip delay, effective transmission volume, packet loss rate, etc. based on the characteristics of data packets based on increment only, without ensuring that the data packets between each data packet need to be incremented by one, so as to determine the network transmission performance and congestion situation of the data transmission path. At the same time, the sending speed and congestion window of the target transmission path are further adjusted dynamically according to the network transmission performance or congestion situation.

[0066] Since the system introduced in the third embodiment of the present application is a system used to implement the method of the first embodiment of the present application, based on the method introduced in the first embodiment of the present application, the person skilled in the art can understand the specific structure and deformation of the system, so it is not repeated here. All systems used in the method of the first embodiment of the present application belong to the scope of protection of the present application.

[0067] Based on the same inventive concept, the present application also provides a fourth embodiment, which is applied to the receiving end, referring to Figure 5 , Figure 5 This is a flow chart of the fourth embodiment of the multi-path data transmission method based on QUIC of the present application.

[0068] In this embodiment, the QUIC-based multipath data transmission method includes steps S40 to S70: Step S210: receiving a data packet sent by a transmitting end, and determining a data packet sequence number and a target transmission path of the data packet; Step S220: obtaining a target data packet sequence number received by the target transmission path, and reception confirmation information corresponding to the target data packet sequence number; In this embodiment, after receiving a data packet and determining the data packet sequence number and the target transmission path according to the header of the data packet, the receiving end associates the data packet sequence number with the target transmission path and saves it, and generates reception confirmation information of the data packet sequence number. When generating a confirmation frame for receiving a data packet on the target transmission path, the data packet sequence numbers of all data packets received based on the target transmission path and the corresponding reception confirmation information are obtained.

[0069] Optionally, the receiving end is preset with a data packet number threshold and a maximum delay confirmation time threshold. When the cumulative number of data packets received on the target transmission path is greater than the data packet number threshold, and / or the delay confirmation time of the data packet due to processing or other reasons is greater than the maximum delay confirmation time threshold, the receiving end executes the step of obtaining the target data packet sequence number received on the target transmission path and the reception confirmation information corresponding to the target data packet sequence number and its subsequent steps to generate a confirmation frame and feed the confirmation frame back to the sending end.

[0070] Exemplarily, the target transmission path is provided with a max_ack_delay parameter. When receiving a data packet, the receiving end may delay the sending of an acknowledgment frame based on the max_ack_delay parameter. The receiving end may delay the receiving acknowledgment information of all data packets received during the delay period after the earliest unacknowledged data packet is received for a time equal to the max_ack_delay parameter, encapsulate and generate an ACK frame, and send it to the sending end.

[0071] Step S230: generating a confirmation frame according to the maximum packet sequence number in the target data packet sequence number and the reception confirmation information; Step S240: Feedback the confirmation frame to the sending end.

[0072] In this embodiment, the receiving end generates the Largest Acknowledged field of the confirmation frame based on the maximum packet sequence number received under the target transmission path, and fills the confirmation frame with the Largest Acknowledged field and its Delay field, and feeds back to the sending end the reception confirmation information of the data packets in the connection level before the maximum packet sequence number.

[0073] In an optional embodiment, the data transmission network includes multiple data transmission nodes, and data transmission can be performed between each data transmission node through multiple paths. Each data transmission node is provided with a path manager of the data transmission path with the data transmission node as the sending end. Each data transmission node can be used as both a sending end and a receiving end of a data packet. Among them, when the first data transmission node as the sending end sends data to be transmitted to the second data transmission node as the receiving end, the confirmation frame to be fed back to the second data transmission node can be encapsulated into a data packet together with the data to be transmitted, and sent to the second data transmission node, thereby realizing the functions of the sending end and the receiving end at the same time, and improving the data transmission efficiency.

[0074] It should be noted that the target transmission path determines the time to feedback the confirmation frame. After receiving any data packet, the receiving end will feedback the confirmation frame at most after the max_ack_delay parameter time has passed.

[0075] In one example, a data transmission node sends a Ping signal to other data transmission nodes at a preset interval to ensure that the data transmission node is in an activated state. The data transmission node that receives the Ping signal will feedback a confirmation frame to the data source of the Ping signal. The data transmission node can encapsulate the Ping signal in a data packet to be sent to the Ping signal data source to complete the feedback of the Ping signal.

[0076] For example, in order to help understand the implementation process of the QUIC-based multi-path data transmission method obtained by combining this embodiment with the above-mentioned embodiment 1, please refer to Figure 6 , Figure 6 A brief flowchart of a multi-path data transmission method based on QUIC is provided, specifically: After encapsulating the data packet, the sender sends the data packet to the receiver and records the sending sequence number sequence. The receiver determines the data packet sequence number of the received data packet, generates reception confirmation information, generates a confirmation frame based on the reception confirmation information, and feeds the confirmation frame back to the sender. The sender determines the receiving sequence number sequence by receiving and reading the confirmation frame. By comparing the sending sequence number sequence with the receiving sequence number sequence, the sender can determine which packets are lost and retransmit them.

[0077] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the multi-path data transmission method based on QUIC of the present application. More forms of simple transformations based on this technical concept are all within the scope of protection of the present application.

[0078] Since the system introduced in the fourth embodiment of the present application is a system used to implement the method of the first embodiment of the present application, based on the method introduced in the first embodiment of the present application, the person skilled in the art can understand the specific structure and deformation of the system, so it is not repeated here. All systems used in the method of the first embodiment of the present application belong to the scope of protection of this application.

[0079] The present application provides a QUIC-based multipath data transmission device, the device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the QUIC-based multipath data transmission method in the above-mentioned embodiment 1.

[0080] Reference below Figure 7 , which shows a schematic diagram of the structure of a QUIC-based multi-path data transmission device suitable for implementing an embodiment of the present application. The QUIC-based multi-path data transmission device in the embodiment of the present application may include but is not limited to mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), vehicle-mounted terminals (such as vehicle-mounted navigation terminals), etc., and fixed terminals such as digital TVs, desktop computers, etc. Figure 7 The QUIC-based multi-path data transmission device shown is merely an example and should not bring any limitations to the functionality and scope of use of the embodiments of the present application.

[0081] like Figure 7As shown, the QUIC-based multipath data transmission device may include a processing device 1001 (e.g., a core processor, a graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM: Read Only Memory) 1002 or a program loaded from a storage device 1003 to a random access memory (RAM: Random Access Memory) 1004. Various programs and data required for the operation of the QUIC-based multipath data transmission device are also stored in RAM1004. The processing device 1001, ROM1002, and RAM1004 are connected to each other via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems may be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; storage devices 1003 including, for example, a magnetic tape, a hard disk, etc.; and communication devices 1009. The communication device 1009 may allow a QUIC-based multipath data transmission device to communicate wirelessly or wired with other devices to exchange data. Although the figure shows a QUIC-based multipath data transmission device with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems may be implemented or have instead.

[0082] In particular, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0083] The QUIC-based multipath data transmission device provided by the present application adopts the QUIC-based multipath data transmission method in the above-mentioned embodiment, which can solve the technical problem that the coupling degree of QUIC-based multipath data transmission is high, resulting in low efficiency of data retransmission and feedback of path congestion control. Compared with the prior art, the beneficial effects of the QUIC-based multipath data transmission device provided by the present application are the same as the beneficial effects of the QUIC-based multipath data transmission method provided by the above-mentioned embodiment, and the other technical features of the QUIC-based multipath data transmission device are the same as the features disclosed in the method of the previous embodiment, which will not be repeated here.

[0084] It should be understood that the various parts disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0085] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0086] The present application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, and the computer-readable program instructions are used to execute the QUIC-based multipath data transmission method in the above-mentioned embodiment.

[0087] The computer-readable storage medium provided in the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM: Random Access Memory), a read-only memory (ROM: Read Only Memory), an erasable programmable read-only memory (EPROM: Erasable Programmable Read Only Memory or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM: CD-Read Only Memory), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, system or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency: Radio Frequency), etc., or any suitable combination of the above.

[0088] The above-mentioned computer-readable storage medium may be included in a QUIC-based multi-path data transmission device; or it may exist independently without being assembled into a QUIC-based multi-path data transmission device.

[0089] The above-mentioned computer-readable storage medium carries one or more programs. When the above-mentioned one or more programs are executed by a QUIC-based multi-path data transmission device, the QUIC-based multi-path data transmission device: encapsulates the data to be transmitted into at least one data frame, and uses the connection-level packet sequence number space of the data to be transmitted; assigns a monotonically increasing data packet sequence number to the data frame in the connection-level packet sequence number space, and selects a target transmission path in the data transmission path; generates a data packet according to the data frame, the data packet sequence number and / or the target transmission path; sends the data packet to the receiving end through the target transmission path, and records the data packet sending record of the target transmission path; receives the confirmation frame fed back by the receiving end, and determines the data packet to be retransmitted according to the confirmation frame and the data packet sending record.

[0090] Computer program code for performing the operations of the present application may be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0091] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each square box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two square boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0092] The modules involved in the embodiments described in this application may be implemented by software or hardware, wherein the name of the module does not constitute a limitation on the unit itself in some cases.

[0093] The readable storage medium provided in the present application is a computer-readable storage medium, which stores computer-readable program instructions (i.e., computer programs) for executing the above-mentioned QUIC-based multipath data transmission method, and can solve the technical problem that the coupling degree of QUIC-based multipath data transmission is high, resulting in low efficiency of data retransmission and feedback of path congestion control. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in the present application are the same as the beneficial effects of the QUIC-based multipath data transmission method provided in the above-mentioned embodiment, and will not be repeated here.

[0094] The above descriptions are only some embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A multipath data transmission method based on QUIC, characterized in that: Applied to the sending end, the method comprises the following steps: Encapsulating the data to be transmitted into at least one data frame, and assigning a monotonically increasing data packet sequence number to the data frame in a connection-level packet sequence number space; Selecting a target transmission path in the data transmission path, and generating a data packet according to the data frame, the data packet sequence number and / or the target transmission path; Sending the data packet to a receiving end through the target transmission path, and recording a data packet sending record of the target transmission path; Receive the confirmation frame fed back by the receiving end, and determine the data packet to be retransmitted according to the confirmation frame and the data packet sending record.

2. The method according to claim 1, characterized in that The step of receiving the confirmation frame fed back by the receiving end and determining the data packet to be retransmitted according to the confirmation frame and the data packet sending record comprises: receiving the confirmation frame, and obtaining a receiving sequence number sequence of the target transmission path in the confirmation frame; Obtaining a sending sequence number sequence of the data packet in the data packet sending record; In the packet loss determination range, the sending sequence number sequence is compared with the receiving sequence number sequence, and the data packet to be retransmitted is determined according to the comparison result.

3. The method according to claim 2, characterized in that The step of comparing the sending sequence number sequence with the receiving sequence number sequence in the packet loss determination range and determining the data packet to be retransmitted according to the comparison result comprises: Determine a target sequence number sequence of the sending sequence number sequence within the packet loss determination range based on a preset retransmission threshold parameter and a maximum packet sequence number in the sending sequence number sequence; Determine the missing data packet sequence numbers of the received sequence number sequence and the target sequence number sequence by comparing the target sequence number sequence and the received sequence number sequence; Determining the data packet to be retransmitted according to the missing data packet sequence number; The data to be retransmitted in the data packet to be retransmitted is obtained, and the data to be retransmitted is added to the data to be transmitted.

4. The method according to claim 2, characterized in that After the step of receiving the confirmation frame and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame, the method further includes: In the confirmation frame, determining the maximum packet sequence number of the received sequence number sequence; In the data packet sending record, determining the sending time of the target data packet with the maximum packet sequence number; The round trip delay of the target data packet is calculated according to the sending time and the receiving time of the confirmation frame.

5. The method according to claim 4, characterized in that After the step of calculating the round trip delay of the target data packet according to the sending time and the receiving time of the confirmation frame, the method further includes: Determining the congestion degree of the target transmission path according to the round-trip delay, the received sequence number sequence and the data packet to be retransmitted; Calculate and adjust the sending speed and congestion window of the data packet of the target transmission path according to the congestion degree; Based on the sending speed and the congestion window, the target transmission path is controlled to perform a data packet sending action.

6. The method according to claim 2, characterized in that The step of receiving the confirmation frame and obtaining the receiving sequence number sequence of the target transmission path in the confirmation frame includes: After receiving the confirmation frame fed back by the receiving end, reading the reception confirmation information in the confirmation frame; According to the reception confirmation information, obtaining the target data packet sequence number; The target data packet sequence numbers are sorted based on the sequence number sizes, and the receiving sequence number sequence is determined according to the sorting results.

7. The method according to claim 1, characterized in that The step of selecting a target transmission path in the data transmission path and generating a data packet according to the data frame, the data packet sequence number and / or the target transmission path comprises: Encrypting the data frame to generate an encrypted data frame; Selecting the target transmission path in the data transmission path, generating the data packet sequence number and metadata of the target transmission path, and constructing a header file of the data packet according to the metadata; The data packet is generated by combining the header file and the encrypted data frame.

8. A multipath data transmission method based on QUIC, characterized in that: Applied to the receiving end, the method comprises the following steps: Receive a data packet sent by a sender, and determine a data packet sequence number and a target transmission path of the data packet; Acquire a target data packet sequence number sequence received by the target transmission path, and reception confirmation information corresponding to the target data packet sequence number sequence; Generate a confirmation frame according to the maximum packet sequence number in the target data packet sequence number sequence and the reception confirmation information; Feedback the confirmation frame to the sending end.

9. A multipath data transmission device based on QUIC, characterized in that: The device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the QUIC-based multipath data transmission method according to any one of claims 1 to 8.

10. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by the processor, the steps of the QUIC-based multipath data transmission method as described in any one of claims 1 to 8 are implemented.

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