U.S.Patent Dec.8,2020 Sheet 6 of 9 US10,862,817B2 CONT. CONT. CONT. FROM FROM FROM FIG.6A FIG.6A FIG.6A S113.The routing device receives the second data packet S114.The routing device determines that an average queue length of a data packet queue is greater than or equal to the first preset threshold and is less than or equal to the second preset threshold S115.The routing device makes a congestion mark for the second data packet,and adds the second data packet to the data packet queue S116.The routing device sends the second data packet to the second device S117.The second device receives the second data packet S118.The second device makes an ECE mark for a second acknowledgement packet S119.The second device sends the second acknowledgement packet to the first device S120.The first device receives the second acknowledgement packet S121.The first device determines a second sub stream set S111a.The first device performs congestion control on sub streams in the second sub stream set FIG.6BU.S. Patent Dec. 8. 2 2020 Sheet 6 of 9 US 10,862,817 B2 CONT . CONT . CONT . FROM FROM FROM FIG . 6A FIG . 6A FIG . 6A Y S113 . The routing device receives the second data packet S114 . The routing device determines that an average queue length of a data packet queue is greater than or equal to the first preset threshold and is less than or equal to the second preset threshold S115 . The routing device makes a congestion mark for the second data packet , and adds the second data packet to the data packet queue S116 . The routing device sends the second data packet to the second device S117 . The second device receives the second data packet S118 . The second device makes an ECE mark for a second acknowledgement packet S119 . The second device sends the second acknowledgement packet to the first device S120 . The first device receives the second acknowledgement packet S121 . The first device determines a second sub stream set Silla . The first device performs congestion control on sub streams in the second sub stream set FIG . 6B