EP3499820B1 8 the MPTCP,after the second device receives the first is configured to receive a first acknowledgement packet data packet from the first device by using the routing de that is from a second device and that includes an ECE vice,the second device may set,in the first acknowledge- identifier used to instruct the device to perform conges- ment packet with which the second device is to reply to tion control,where the first acknowledgement packet is the first device,an ECE identifier used to notify the first 5 an acknowledgement packet of a first data packet of a device that a sub stream in which the first data packet is first sub stream in a plurality of sub streams transmitted located may be congested.The ECE identifier is an echo on a plurality of transmission paths between the first de- identifier that is set by the second device for an ECN vice and the second device.The determining module is identifier in the data packet received by the second de- configured to determine,based on indication of the ECE vice.Therefore,after the first device receives the first 10 identifier,a first sub stream set that includes the first sub acknowledgement packet including the ECE identifier, stream and a plurality of second sub streams that meet the first device may group,into one sub stream set,sub a congestion control condition in sub streams other than streams that meet a congestion control condition in a the first sub stream in the plurality of sub streams.The plurality of sub streams transmitted on a plurality of trans- control module is configured to perform congestion con- mission paths between the first device and the second 15 trol on sub streams in the first sub stream set. device.These sub streams that meet the congestion con- [0038]In a first optional implementation of the fourth trol condition may be bandwidth-shared sub streams to aspect,the receiving module may be further configured a specific degree.To be specific,in this application,a to:after the determining module determines the first sub plurality of bandwidth-shared sub streams can be stream set,and before the control module performs con- grouped into one sub stream set to a specific degree, 20 gestion control on the sub streams in the first sub stream and congestion control can be performed on the sub set,receive a second acknowledgement packet that is streams in the sub stream set.In this way,a congestion of a data packet(hereinafter referred to as a second data control effect can be significantly improved,so that the packet)of a sub stream in the first sub stream set,that first device can perform congestion control on a sub is from the second device,and that includes the ECE stream that may be congested. 25 identifier.The determining module may be further con- [0035]In a first optional implementation of the third as- figured to detemmine,based on indication ofthe ECE iden- pect,the congestion control method provided in this ap- tifier,a second sub stream set including the sub stream, plication may further include:receiving,by the second where the second sub stream set is a subset of the first device,a second data packet from the routing device; sub stream set.The control module may be further con- making an ECE mark for a second acknowledgement 30 figured to perform congestion control on sub streams in packet with which the second device is to reply to the the second sub stream set. first device;and sending the second acknowledgement [0039]In a second optional implementation of the packet to the first device. fourth aspect,the control module may be further config- [0036]In this application,after the second device re- ured to perform congestion control on a sub stream (here- ceives the second data packet from the first device by 35 inafter referred to as a sub stream that is not in the first using the routing device,the second device may set,in sub stream set)that is other than the sub streams in the the second acknowledgement packet with which the sec- first sub stream set and that is in the plurality of sub ond device is to reply to the first device,an ECE identifier streams. used to notify the first device that a sub stream in which [0040]In a third optional implementation of the fourth the second data packet is located may be congested. 40 aspect,the control module may be further configured to The ECE identifier is an echo identifier that is set by the perform congestion control on a sub stream(hereinafter second device for an ECN identifier in the data packet referred to as a sub stream that is not in the second sub received by the second device.Therefore,after the first stream set)that is other than the sub streams in the sec- device receives the second acknowledgement packet in- ond sub stream set and that is in the plurality of sub cluding the ECE identifier,the first device may group, 45 streams. into a second sub stream set,sub streams that meet the [0041]In a fourth optional implementation of the fourth congestion control condition in a first sub stream set.In aspect,a method for determining,by the determining other words,the first device may further determine the module,the first sub stream set based on indication of second sub stream set (the second sub stream set is a the ECE identifier may include:monitoring,by the deter- subset ofthe first sub stream set)from the first sub stream 50 mining module,the sub streams other than the first sub set.In this way,the first device can determine,in relatively stream in the plurality of sub streams in a preset time high accuracy,a sub stream set on which congestion period;determining,as the plurality of second sub control is to be performed,so that a congestion control streams,sub streams that meet the congestion control effect can be significantly improved,to further improve condition in the sub streams other than the first sub MPTCP transmission performance. 55 stream in the plurality of sub streams;and determining [0037]According to a fourth aspect,a device is provid- the first sub stream and the plurality of second sub ed.The device includes a receiving module,a determin- streams as the first sub stream set. ing module,and a control module.The receiving module [0042]In a fifth optional implementation of the fourth 6EP 3 499 820 B1 6 5 10 15 20 25 30 35 40 45 50 55 the MPTCP, after the second device receives the first data packet from the first device by using the routing de￾vice, the second device may set, in the first acknowledge￾ment packet with which the second device is to reply to the first device, an ECE identifier used to notify the first device that a sub stream in which the first data packet is located may be congested. The ECE identifier is an echo identifier that is set by the second device for an ECN identifier in the data packet received by the second de￾vice. Therefore, after the first device receives the first acknowledgement packet including the ECE identifier, the first device may group, into one sub stream set, sub streams that meet a congestion control condition in a plurality of sub streams transmitted on a plurality of trans￾mission paths between the first device and the second device. These sub streams that meet the congestion con￾trol 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 congestion control can be performed on the sub streams in the sub stream set. In this way, a congestion control effect can be significantly improved, so that the first device can perform congestion control on a sub stream that may be congested. [0035] In a first optional implementation of the third as￾pect, the congestion control method provided in this ap￾plication may further include: receiving, by the second device, a second data packet from the routing device; making an ECE mark for a second acknowledgement packet with which the second device is to reply to the first device; and sending the second acknowledgement packet to the first device. [0036] In this application, after the second device re￾ceives the second data packet from the first device by using the routing device, the second device may set, in the second acknowledgement packet with which the sec￾ond device is to reply to the first device, an ECE identifier used to notify the first device that a sub stream in which the second data packet is located may be congested. The ECE identifier is an echo identifier that is set by the second device for an ECN identifier in the data packet received by the second device. Therefore, after the first device receives the second acknowledgement packet in￾cluding the ECE identifier, the first device may group, into a second sub stream set, sub streams that meet the congestion control condition in a first sub stream set. In other words, the first device may further determine the second sub stream set (the second sub stream set is a subset of the first sub stream set) from the first sub stream set. In this way, the first device can determine, in relatively high accuracy, a sub stream set on which congestion control is to be performed, so that a congestion control effect can be significantly improved, to further improve MPTCP transmission performance. [0037] According to a fourth aspect, a device is provid￾ed. The device includes a receiving module, a determin￾ing module, and a control module. The receiving module is configured to receive a first acknowledgement packet that is from a second device and that includes an ECE identifier used to instruct the device to perform conges￾tion control, where the first acknowledgement packet is an acknowledgement packet of a first data packet of a first sub stream in a plurality of sub streams transmitted on a plurality of transmission paths between the first de￾vice and the second device. The determining module is configured to determine, 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 congestion control condition in sub streams other than the first sub stream in the plurality of sub streams. The control module is configured to perform congestion con￾trol on sub streams in the first sub stream set. [0038] In a first optional implementation of the fourth aspect, the receiving module may be further configured to: after the determining module determines the first sub stream set, and before the control module performs con￾gestion control on the sub streams in the first sub stream set, receive a second acknowledgement packet that is of a data packet (hereinafter referred to as a second data packet) of a sub stream in the first sub stream set, that is from the second device, and that includes the ECE identifier. The determining module may be further con￾figured to determine, based on indication of the ECE iden￾tifier, a second sub stream set including the sub stream, where the second sub stream set is a subset of the first sub stream set. The control module may be further con￾figured to perform congestion control on sub streams in the second sub stream set. [0039] In a second optional implementation of the fourth aspect, the control module may be further config￾ured to perform congestion control on a sub stream (here￾inafter referred to as a sub stream that is not in the first sub stream set) that is other than the sub streams in the first sub stream set and that is in the plurality of sub streams. [0040] In a third optional implementation of the fourth aspect, the control module may be further configured to perform congestion control on a sub stream (hereinafter referred to as a sub stream that is not in the second sub stream set) that is other than the sub streams in the sec￾ond sub stream set and that is in the plurality of sub streams. [0041] In a fourth optional implementation of the fourth aspect, a method for determining, by the determining module, the first sub stream set based on indication of the ECE identifier may include: monitoring, by the deter￾mining module, the sub streams other than the first sub stream in the plurality of sub streams in a preset time period; determining, as the plurality of second sub streams, sub streams that meet the congestion control condition in the sub streams other than the first sub stream in the plurality of sub streams; and determining the first sub stream and the plurality of second sub streams as the first sub stream set. [0042] In a fifth optional implementation of the fourth 7 8