7 EP3499820B1 2 Description tions on Queue Management and Congestion Avoidance in the Internet"in IETF RFC2309 by B.Braden,IETF,30 TECHNICAL FIELD April 1998,refers to recommendations on Queue Man- agmenet and Congestion Avoidance. [0001]The presentinvention relates to the field of com- 5 [0008]Further,the prior art document"Random Early munications technologies,and in particular,to a conges- Detection Gateways for Congestion Avoidance"by tion control method,an apparatus,and a system Floyd.S.et.al.IEEE/ACM Transactions on networking IEEE/ACM,New York,31.August 1993 refers to random BACKGROUND early detection gateways for congestion avoidance. o [0002]In a communications system,the Multipath SUMMARY Transmission Control Protocol(Multipath Transmission Control Protocol,MPTCP)can implement multipath par- [0009]This application provides a congestion control allel data transmission. method,an apparatus,and a system,to significantly im- [0003]Currently,to improve a throughput during data 15 prove a congestion control effect. transmission performed by using the MPTCP,when data [0010]This problem is solved by the subject matter of transmission is performed between a transmit end and the independent claims.Further implemenation forms a receive end by using the MPTCP,congestion control are provided in the dependent claims. (for example,adjusting bandwidth occupied by each sub [0011]To achieve the foregoing objective,this appli- stream)needs to be performed on a plurality of data 20 cation uses the following technical solutions.According streams (a data stream transmitted on each transmission to a first aspect,a congestion control method is provided path is referred to as a sub data stream,hereinafter re- The method is applied to a process in which data trans- ferred to as a sub stream)transmitted on a plurality of mission is performed between a first device and a second transmission paths(a connection over which data trans- device by using the MPTCP.The method may include mission is performed by using the plurality of transmis- 25 receiving.by the first device,a first acknowledgement sion paths may be referred to as an MPTCP connection) packet that is from the second device and that includes between the transmit end and the receive end.When an ECE identifier used to instruct the first device to per- congestion control is performed on the plurality of data form congestion control,where the first acknowledge- streams,to ensure fairness between an MPTCP connec- ment packet is an acknowledgement packet of a first data tion and a Transmission Control Protocol (Transmission 30 packet of a first sub stream in a plurality of data streams Control Protocol.TCP)connection(when data transmis- (hereinafter referred to as a plurality of sub streams) sion is performed between the transmit end and the re transmitted on a plurality of transmission paths between ceive end by using the TCP,a connection over which the first device and the second device;determining,by data transmission is performed between the transmit end the first device based on indication of the ECE identifier. and the receive end by using a single transmission path 35 a first sub stream set that includes the first sub stream is referred to as a TCP connection)in a network,a and a plurality of second sub streams that meet a con- throughput of each MPTCP connection usually needs to gestion control condition in sub streams other than the be equal to a throughput of each TCP connection. first sub stream in the plurality of sub streams;and per- [0004]However,a plurality of sub streams are trans- forming congestion control on sub streams in the first sub mitted on each MPTCP connection,and possibly only 40 stream set. some of the plurality of sub streams share bandwidth.If [0012]In this application,the first device may use a set congestion control is simultaneously performed on the congestion control method to perform congestion control plurality of sub streams according to the foregoing meth- on the sub streams in the first sub stream set od,because it can be only ensured that a throughput of [0013]In the congestion control method provided in each MPTCP connection is equal to a throughput of each 45 this application,when data transmission is performed be- TCP connection,a throughput of the MPTCP connection tween the first device and the second device by using may not be significantly improved. the MPTCP,the first device may group,into one sub [0005]Prior art document "Revisiting congestion con- stream set,sub streams that meet the congestion control trol for multipath TCP with shared bottleneck detection" condition in the plurality of sub streams transmitted on by Ferlin Simone et al,IEEE INFOCOM 2016,10.April 50 the plurality of transmission paths between the first de- 2016 refers to a congestion control for multipath TCP vice and the second device.These sub streams that meet with a shared bottleneck detection. the congestion control condition may be bandwidth- [0006]Further,the prior art document"The Addition of shared sub streams to a specific degree.To be specific Explicit Congestion Notification (ECN)to IP"in IETF in this application,a plurality of bandwidth-shared sub RFC3168 by Ramakrishnan et.al.,Teraoptic networks, 55 streams can be grouped into one sub stream set to a 30.September 2001 refers to an addition of an explicit specific degree,and then congestion control can be per- congestion notification. formed on the sub streams in the set.In this way,a con- [0007]Further,the prior art document"Recommenda- gestion control effect can be significantly improved,to 3EP 3 499 820 B1 3 5 10 15 20 25 30 35 40 45 50 55 Description TECHNICAL FIELD [0001] The present invention relates to the field of com￾munications technologies, and in particular, to a conges￾tion control method, an apparatus, and a system. BACKGROUND [0002] In a communications system, the Multipath Transmission Control Protocol (Multipath Transmission Control Protocol, MPTCP) can implement multipath par￾allel data transmission. [0003] Currently, to improve a throughput during data transmission performed by using the MPTCP, when data transmission is performed between a transmit end and a receive end by using the MPTCP, congestion control (for example, adjusting bandwidth occupied by each sub stream) needs to be performed on a plurality of data streams (a data stream transmitted on each transmission path is referred to as a sub data stream, hereinafter re￾ferred to as a sub stream) transmitted on a plurality of transmission paths (a connection over which data trans￾mission is performed by using the plurality of transmis￾sion paths may be referred to as an MPTCP connection) between the transmit end and the receive end. When congestion control is performed on the plurality of data streams, to ensure fairness between an MPTCP connec￾tion and a Transmission Control Protocol (Transmission Control Protocol, TCP) connection (when data transmis￾sion is performed between the transmit end and the re￾ceive end by using the TCP, a connection over which data transmission is performed between the transmit end and the receive end by using a single transmission path is referred to as a TCP connection) in a network, a throughput of each MPTCP connection usually needs to be equal to a throughput of each TCP connection. [0004] However, a plurality of sub streams are trans￾mitted on each MPTCP connection, and possibly only some of the plurality of sub streams share bandwidth. If congestion control is simultaneously performed on the plurality of sub streams according to the foregoing meth￾od, because it can be only ensured that a throughput of each MPTCP connection is equal to a throughput of each TCP connection, a throughput of the MPTCP connection may not be significantly improved. [0005] Prior art document "Revisiting congestion con￾trol for multipath TCP with shared bottleneck detection" by Ferlin Simone et al, IEEE INFOCOM 2016, 10. April 2016 refers to a congestion control for multipath TCP with a shared bottleneck detection. [0006] Further, the prior art document "The Addition of Explicit Congestion Notification (ECN) to IP" in IETF RFC3168 by Ramakrishnan et.al., Teraoptic networks, 30. September 2001 refers to an addition of an explicit congestion notification. [0007] Further, the prior art document "Recommenda￾tions on Queue Management and Congestion Avoidance in the Internet" in IETF RFC2309 by B. Braden, IETF, 30. April 1998, refers to recommendations on Queue Man￾agmenet and Congestion Avoidance. [0008] Further, the prior art document "Random Early Detection Gateways for Congestion Avoidance" by Floyd. S. et. al. IEEE/ACM Transactions on networking, IEEE/ACM, New York, 31. August 1993 refers to random early detection gateways for congestion avoidance. SUMMARY [0009] This application provides a congestion control method, an apparatus, and a system, to significantly im￾prove a congestion control effect. [0010] This problem is solved by the subject matter of the independent claims. Further implemenation forms are provided in the dependent claims. [0011] To achieve the foregoing objective, this appli￾cation uses the following technical solutions. According to a first aspect, a congestion control method is provided. The method is applied to a process in which data trans￾mission is performed between a first device and a second device by using the MPTCP. The method may include: receiving, by the first device, a first acknowledgement packet that is from the second device and that includes an ECE identifier used to instruct the first device to per￾form congestion control, where the first acknowledge￾ment packet is an acknowledgement packet of a first data packet of a first sub stream in a plurality of data streams (hereinafter referred to as a plurality of sub streams) transmitted on a plurality of transmission paths between the first device and the second device; determining, by the first device based on indication of the ECE identifier, a first sub stream set that includes the first sub stream and a plurality of second sub streams that meet a con￾gestion control condition in sub streams other than the first sub stream in the plurality of sub streams; and per￾forming congestion control on sub streams in the first sub stream set. [0012] In this application, the first device may use a set congestion control method to perform congestion control on the sub streams in the first sub stream set. [0013] In the congestion control method provided in this application, when data transmission is performed be￾tween the first device and the second device by using the MPTCP, the first device may group, into one sub stream set, sub streams that meet the congestion control condition in the plurality of sub streams transmitted on the plurality of transmission paths between the first de￾vice and the second device. These sub streams that meet the congestion control condition may be bandwidth￾shared sub streams to a specific degree. To be specific, in this application, a plurality of bandwidth-shared sub streams can be grouped into one sub stream set to a specific degree, and then congestion control can be per￾formed on the sub streams in the set. In this way, a con￾gestion control effect can be significantly improved, to 1 2