BBR\u5bf9TCP\u6027\u80fd\u7684\u63d0\u5347\u662f\u5de8\u5927\u7684\uff0c\u5b83\u80fd\u66f4\u6709\u6548\u7684\u4f7f\u7528\u5f53\u4e0b\u7f51\u7edc\u73af\u5883\uff0cYoutube\u5e94\u7528\u540e\u5728\u541e\u5410\u91cf\u4e0a\u6709\u5e73\u57474%\u63d0\u5347\uff08\u5bf9\u4e8e\u65e5\u672c\u8fd9\u6837\u7684\u7f51\u7edc\u73af\u5883\u670914%\u4ee5\u4e0a\u7684\u63d0\u5347\uff09\uff1a<\/p>\n\n\n\n
\u62a5\u6587\u7684\u5f80\u8fd4\u65f6\u5ef6RTT\u964d\u4f4e\u4e8633%\uff0c\u8fd9\u6837\u5982\u89c6\u9891\u8fd9\u6837\u7684\u5927\u6587\u4ef6\u4f20\u8f93\u66f4\u5feb\uff0c\u7528\u6237\u4f53\u9a8c\u66f4\u597d\uff1a<\/p>\n\n\n\n
\u4e0d\u50cfCUBIC\u8fd9\u79cd\u57fa\u4e8e\u4e22\u5305\u505a\u62e5\u585e\u63a7\u5236\uff0c\u5e38\u5bfc\u81f4\u74f6\u9888\u8def\u7531\u5668\u5927\u91cf\u62a5\u6587\u4e22\u5931\uff0c\u6240\u4ee5\u91cd\u65b0\u7f13\u5b58\u7684\u5e73\u5747\u95f4\u9694\u65f6\u95f4\u4e5f\u6709\u4e8611%\u63d0\u5347\uff1a<\/p>\n\n\n\n
\u5728Linux4.19\u5185\u6838\u4e2d\u5df2\u7ecf\u5c06\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\u4eceCUBIC\uff08\u8be5\u7b97\u6cd5\u4ece2.6.19\u5185\u6838\u5c31\u5f15\u5165Linux\u4e86\uff09\u6539\u4e3aBBR\uff0c\u800c\u5373\u5c06\u9762\u4e16\u7684\u57fa\u4e8eUDP\u7684HTTP3\u4e5f\u4f7f\u7528\u6b64\u7b97\u6cd5\u3002\u8bb8\u591a\u505a\u5e94\u7528\u5f00\u53d1\u7684\u540c\u5b66\u53ef\u80fd\u5e76\u4e0d\u6e05\u695a\u4ec0\u4e48\u662f\u62e5\u585e\u63a7\u5236\uff0cBBR\u7b97\u6cd5\u5230\u5e95\u5728\u505a\u4ec0\u4e48\uff0c\u6211\u5728\u300aWeb\u534f\u8bae\u8be6\u89e3\u4e0e\u6293\u5305\u5b9e\u6218\u300b\u8fd9\u95e8\u8bfe\u7a0b\u4e2d\u7528\u4e866\u8282\u8bfe\u5728\u8bb2\u76f8\u5173\u5185\u5bb9\uff0c\u8fd9\u91cc\u6211\u5c1d\u8bd5\u4e0b\u7528\u4e00\u7bc7\u56fe\u7247\u6bd4\u6587\u5b57\u8fd8\u591a\u7684\u6587\u7ae0\u628a\u8fd9\u4e2a\u4e8b\u8bf4\u6e05\u695a\u3002<\/p>\n\n\n\n
TCP\u534f\u8bae\u662f\u9762\u5411\u5b57\u7b26\u6d41\u7684\u534f\u8bae\uff0c\u5b83\u5141\u8bb8\u5e94\u7528\u5c42\u57fa\u4e8eread\/write\u65b9\u6cd5\u6765\u53d1\u9001\u3001\u8bfb\u53d6\u4efb\u610f\u957f\u7684\u5b57\u7b26\u6d41\uff1a<\/p>\n\n\n\n
\u4f46TCP\u4e4b\u4e0b\u7684IP\u5c42\u662f\u57fa\u4e8e\u5757\u72b6\u7684Packet\u62a5\u6587\u6765\u5206\u7247\u53d1\u9001\u7684\uff0c\u56e0\u6b64\uff0cTCP\u534f\u8bae\u9700\u8981\u5c06\u5e94\u7528\u4ea4\u4ed8\u7ed9\u5b83\u7684\u5b57\u7b26\u6d41\u62c6\u5206\u6210\u591a\u4e2aPacket\uff08\u5728TCP\u4f20\u8f93\u5c42\u88ab\u79f0\u4e3aSegment\uff09\u53d1\u9001\uff0c\u7531\u4e8e\u7f51\u901f\u6709\u53d8\u5316\u4e14\u63a5\u6536\u4e3b\u673a\u7684\u5904\u7406\u6027\u80fd\u6709\u9650\uff0cTCP\u8fd8\u8981\u51b3\u5b9a\u4f55\u65f6\u53d1\u9001\u8fd9\u4e9bSegment\u3002TCP\u6ed1\u52a8\u7a97\u53e3\u89e3\u51b3\u4e86Client\u3001Server\u8fd9\u4e24\u53f0\u4e3b\u673a\u7684\u95ee\u9898\uff0c\u4f46\u6ca1\u6709\u53bb\u7ba1\u8fde\u63a5\u4e2d\u5927\u91cf\u8def\u7531\u5668\u3001\u4ea4\u6362\u673a\u8f6c\u53d1IP\u62a5\u6587\u7684\u95ee\u9898\uff0c\u56e0\u6b64\u5f53\u74f6\u9888\u8def\u7531\u5668\u7684\u8f93\u5165\u6d41\u5927\u4e8e\u5176\u8f93\u51fa\u6d41\u65f6\uff0c\u4fbf\u4f1a\u53d1\u751f\u62e5\u585e\uff1a<\/p>\n\n\n\n
\u8fd9\u867d\u7136\u662fIP\u7f51\u7edc\u5c42\u7684\u4e8b\uff0c\u4f46\u5982\u679cTCP\u57fa\u4e8e\u5206\u5c42\u539f\u5219\u4e0d\u53bb\u7ba1\uff0c\u4e92\u8054\u7f51\u4e0a\u5927\u91cf\u4e3b\u673a\u7684TCP\u7a0b\u5e8f\u4fbf\u4f1a\u9020\u6210\u7f51\u7edc\u6076\u6027\u62e5\u5835\u3002\u4e0a\u56fe\u4e2d\u74f6\u9888\u8def\u7531\u5668\u5df2\u7ecf\u9020\u6210\u4e86\u7f51\u901f\u4e0b\u964d\uff0c\u4f46\u5982\u679c\u53d1\u9001\u65b9\u4e0d\u7ba1\u4e0d\u987e\uff0c\u90a3\u4e48\u74f6\u9888\u8def\u7531\u5668\u7684\u7f13\u51b2\u961f\u5217\u586b\u6ee1\u540e\u4fbf\u4f1a\u53d1\u751f\u5927\u91cf\u4e22\u5305\uff0c\u4e14\u6b64\u65f6RTT\uff08\u62a5\u6587\u5f80\u8fd4\u65f6\u95f4\uff09\u7531\u4e8e\u5b58\u5728\u957f\u961f\u5217\u800c\u6781\u9ad8\u3002<\/p>\n\n\n\n
\u5982\u4e0a\u56fe\uff0c\u6700\u597d\u7684\u72b6\u6001\u662f\u6ca1\u6709\u961f\u5217\uff0c\u6b64\u65f6RTT\u6700\u4f4e\uff0c\u800cState2\u4e2dRTT\u5347\u9ad8\uff0c\u4f46\u6ca1\u6709\u4e22\u5305\uff0c\u5230State 3\u961f\u5217\u6ee1\u65f6\u5f00\u59cb\u53d1\u751f\u4e22\u5305\u3002<\/p>\n\n\n\n
TCP\u7684\u62e5\u585e\u63a7\u5236\u4fbf\u7528\u4e8e\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002\u5728BBR\u51fa\u73b0\u524d\uff0c\u62e5\u585e\u63a7\u5236\u5206\u4e3a\u56db\u4e2a\u90e8\u5206\uff1a\u6162\u542f\u52a8\u3001\u62e5\u585e\u907f\u514d\u3001\u5feb\u901f\u91cd\u4f20\u3001\u5feb\u901f\u6062\u590d\uff1a<\/p>\n\n\n\n
\u6162\u542f\u52a8\u5728BBR\u4e2d\u4ecd\u7136\u4fdd\u7559\uff0c\u5b83\u7684\u610f\u4e49\u662f\u5728\u4e0d\u77e5\u9053\u8fde\u63a5\u7684\u74f6\u9888\u5e26\u5bbd\u65f6\uff0c\u4ee5\u8d77\u59cb\u8f83\u4f4e\u7684\u53d1\u9001\u901f\u7387\uff0c\u4ee5\u6bcfRTT\u4e24\u500d\u7684\u901f\u5ea6\u5feb\u901f\u589e\u52a0\u53d1\u9001\u901f\u7387\uff0c\u76f4\u5230\u5230\u8fbe\u4e00\u4e2a\u9608\u503c\uff0c\u5bf9\u5e94\u4e0a\u56fe\u4e2d0-4\u79d2\u3002\u5230\u8be5\u9608\u503c\u540e\uff0c\u8fdb\u5165\u7ebf\u6027\u63d0\u9ad8\u53d1\u9001\u901f\u7387\u7684\u9636\u6bb5\uff0c\u8be5\u9636\u6bb5\u53eb\u505a\u62e5\u585e\u907f\u514d\uff0c\u76f4\u5230\u53d1\u751f\u4e22\u5305\uff0c\u5bf9\u5e94\u4e0a\u56fe\u4e2d8-11\u79d2\u3002\u4e22\u5305\u540e\uff0c\u53d1\u901f\u901f\u7387\u5927\u5e45\u4e0b\u964d\uff0c\u9488\u5bf9\u4e22\u5305\u4f7f\u7528\u5feb\u901f\u91cd\u4f20\u7b97\u6cd5\u91cd\u9001\u53d1\u9001\uff0c\u540c\u65f6\u4e5f\u4f7f\u7528\u5feb\u901f\u6062\u590d\u7b97\u6cd5\u628a\u53d1\u9001\u901f\u7387\u5c3d\u91cf\u5e73\u6ed1\u7684\u5347\u4e0a\u6765\u3002<\/p>\n\n\n\n
\u5982\u679c\u74f6\u9888\u8def\u7531\u5668\u7684\u7f13\u5b58\u7279\u522b\u5927\uff0c\u90a3\u4e48\u8fd9\u79cd\u4ee5\u4e22\u5305\u4f5c\u4e3a\u63a2\u6d4b\u4f9d\u636e\u7684\u62e5\u585e\u7b97\u6cd5\u5c06\u4f1a\u5bfc\u81f4\u4e25\u91cd\u95ee\u9898\uff1aTCP\u94fe\u8def\u4e0a\u957f\u65f6\u95f4RTT\u53d8\u5927\uff0c\u4f46\u541e\u5410\u91cf\u7ef4\u6301\u4e0d\u53d8\u3002<\/p>\n\n\n\n
\u4e8b\u5b9e\u4e0a\uff0c\u6211\u4eec\u7684\u4f20\u8f93\u901f\u5ea6\u57283\u4e2a\u9636\u6bb5\u88ab\u4e0d\u540c\u7684\u56e0\u7d20\u9650\u5236\uff1a1\u3001\u5e94\u7528\u7a0b\u5e8f\u9650\u5236\u9636\u6bb5\uff0c\u6b64\u65f6RTT\u4e0d\u53d8\uff0c\u968f\u7740\u5e94\u7528\u7a0b\u5e8f\u5f00\u59cb\u53d1\u9001\u5927\u6587\u4ef6\uff0c\u901f\u7387\u76f4\u7ebf\u4e0a\u5347\uff1b2\u3001BDP\u9650\u5236\u9636\u6bb5\uff0c\u6b64\u65f6RTT\u5f00\u59cb\u4e0d\u65ad\u4e0a\u5347\uff0c\u4f46\u541e\u5410\u91cf\u4e0d\u53d8\uff0c\u56e0\u4e3a\u6b64\u65f6\u74f6\u9888\u8def\u7531\u5668\u5df2\u7ecf\u8fbe\u5230\u4e0a\u9650\uff0c\u7f13\u51b2\u961f\u5217\u6b63\u5728\u4e0d\u65ad\u589e\u52a0\uff1b3\u3001\u74f6\u9888\u8def\u7531\u5668\u7f13\u51b2\u961f\u5217\u9650\u5236\u9636\u6bb5\uff0c\u6b64\u65f6\u5f00\u59cb\u5927\u91cf\u4e22\u5305\u3002\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n\n\n\n
\u5982CUBIC\u8fd9\u6837\u57fa\u4e8e\u4e22\u5305\u7684\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\u5728\u7b2c2\u6761\u7070\u8272\u7ad6\u7ebf\u53d1\u751f\u4f5c\u7528\uff0c\u8fd9\u5df2\u7ecf\u592a\u665a\u4e86\uff0c\u66f4\u597d\u7684\u4f5c\u7528\u70b9\u662fBDP\u4e0a\u9650\u5f00\u59cb\u53d1\u6325\u4f5c\u7528\u65f6\uff0c\u4e5f\u5c31\u662f\u7b2c1\u6761\u7070\u8272\u7ad6\u7ebf\u3002<\/p>\n\n\n\n
\u4ec0\u4e48\u53eb\u505aBDP\u5462\uff1f\u5b83\u53eb\u505a\u5e26\u5bbd\u65f6\u5ef6\u79ef\uff0c\u4f8b\u5982\u4e00\u6761\u94fe\u8def\u7684\u5e26\u5bbd\u662f100Mbps\uff0c\u800cRTT\u662f40ms\uff0c\u90a3\u4e48<\/p>\n\n\n\n
BDP=100Mbps*0.04s=4Mb=0.5MB
\u5373\u5e73\u5747\u6bcf\u79d2\u98de\u884c\u4e2d\u7684\u62a5\u6587\u5e94\u5f53\u662f0.5MB\u3002\u56e0\u6b64Linux\u7684\u63a5\u6536\u7a97\u53e3\u7f13\u5b58\u5e38\u53c2\u8003\u6b64\u8bbe\u7f6e\uff1a<\/p>\n\n\n\n
\u7b2c1\u6761\u7070\u8272\u7ad6\u7ebf\uff0c\u662f\u74f6\u9888\u8def\u7531\u5668\u7684\u7f13\u51b2\u961f\u5217\u521a\u521a\u5f00\u59cb\u79ef\u538b\u65f6\u7684\u8282\u70b9\u3002\u968f\u7740\u5185\u5b58\u7684\u4e0d\u65ad\u964d\u4ef7\uff0c\u8def\u7531\u5668\u8bbe\u5907\u7684\u7f13\u51b2\u961f\u5217\u4e5f\u4f1a\u8d8a\u6765\u8d8a\u5927\uff0cCUBIC\u7b97\u6cd5\u4f1a\u9020\u6210\u66f4\u5927\u7684RTT\u65f6\u5ef6\uff01<\/p>\n\n\n\n
\u800cBBR\u901a\u8fc7\u68c0\u6d4bRTprop\u548cBtlBw\u6765\u5b9e\u73b0\u62e5\u585e\u63a7\u5236\u3002\u4ec0\u4e48\u662fRTprop\u5462\uff1f\u8fd9\u662f\u94fe\u8def\u7684\u7269\u7406\u65f6\u5ef6\uff0c\u56e0\u4e3aRTT\u91cc\u542b\u6709\u62a5\u6587\u5728\u8def\u7531\u5668\u961f\u5217\u91cc\u7684\u6392\u961f\u65f6\u95f4\u3001ACK\u7684\u5ef6\u8fdf\u786e\u8ba4\u65f6\u95f4\u7b49\u3002\u4ec0\u4e48\u53eb\u5ef6\u8fdf\u786e\u8ba4\u5462\uff1fTCP\u6bcf\u4e2a\u62a5\u6587\u5fc5\u987b\u88ab\u786e\u8ba4\uff0c\u786e\u8ba4\u52a8\u4f5c\u662f\u901a\u8fc7\u63a5\u6536\u7aef\u53d1\u9001ACK\u62a5\u6587\u5b9e\u73b0\u7684\uff0c\u4f46\u7531\u4e8eTCP\u548cIP\u5934\u90e8\u670940\u4e2a\u5b57\u8282\uff0c\u5982\u679c\u4e0d\u643a\u5e26\u6570\u636e\u53ea\u4e3a\u53d1\u9001ACK\u7f51\u7edc\u6548\u7387\u8fc7\u4f4e\uff0c\u6240\u4ee5\u4f1a\u8ba9\u72ec\u7acb\u7684ACK\u62a5\u6587\u7b49\u4e00\u7b49\uff0c\u770b\u770b\u6709\u6ca1\u6709\u6570\u636e\u53d1\u7684\u65f6\u5019\u987a\u4fbf\u5e26\u7ed9\u5bf9\u65b9\uff0c\u6216\u8005\u7b49\u7b49\u770b\u591a\u4e2aACK\u4e00\u8d77\u53d1\u3002\u6240\u4ee5\uff0c\u53ef\u4ee5\u7528\u4e0b\u5217\u516c\u5f0f\u8868\u793aRTT\u4e0eRTprop\u7684\u5dee\u522b\uff1a<\/p>\n\n\n\n
RTT\u6211\u4eec\u53ef\u4ee5\u6d4b\u91cf\u5f97\u51fa\uff0cRTprop\u5462\uff0c\u6211\u4eec\u53ea\u9700\u8981\u627e\u5230\u74f6\u9888\u8def\u7531\u5668\u961f\u5217\u4e3a\u7a7a\u65f6\u591a\u6b21RTT\u6d4b\u91cf\u7684\u6700\u5c0f\u503c\u5373\u53ef\uff1a<\/p>\n\n\n\n
\u800cBtlBw\u5168\u79f0\u662fbottleneck bandwith\uff0c\u5373\u74f6\u9888\u5e26\u5bbd\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u6d4b\u91cf\u5df2\u53d1\u9001\u4f46\u672aACK\u786e\u8ba4\u7684\u98de\u884c\u4e2d\u5b57\u8282\u9664\u4ee5\u98de\u884c\u65f6\u95f4deliveryRate\u6765\u6d4b\u91cf\uff1a<\/p>\n\n\n\n
\u65e9\u57281979\u5e74Leonard Kleinrock\u5c31\u63d0\u51fa\u4e86\u7b2c1\u6761\u7ad6\u7ebf\u662f\u6700\u597d\u7684\u62e5\u585e\u63a7\u5236\u70b9\uff0c\u4f46\u88abJeffrey M. Jaffe\u8bc1\u660e\u4e0d\u53ef\u80fd\u5b9e\u73b0\uff0c\u56e0\u4e3a\u6ca1\u6709\u529e\u6cd5\u5224\u65adRTT\u53d8\u5316\u5230\u5e95\u662f\u4e0d\u662f\u56e0\u4e3a\u94fe\u8def\u53d8\u5316\u4e86\uff0c\u4ece\u800c\u4e0d\u540c\u7684\u8bbe\u5907\u74f6\u9888\u5bfc\u81f4\u7684\uff0c\u8fd8\u662f\u74f6\u9888\u8def\u7531\u5668\u4e0a\u7684\u5176\u4ed6TCP\u8fde\u63a5\u7684\u6d41\u91cf\u53d1\u751f\u4e86\u5927\u7684\u53d8\u5316\u3002\u4f46\u6211\u4eec\u6709\u4e86RTprop\u548cBtlBw\u540e\uff0c\u5f53RTprop\u5347\u9ad8\u65f6\u6211\u4eec\u4fbf\u5f97\u5230\u4e86BtlBw\uff0c\u8fd9\u4fbf\u627e\u5230\u7b2c1\u6761\u7070\u8272\u7ad6\u7ebf\u6700\u597d\u7684\u62e5\u585e\u63a7\u5236\u70b9\uff0c\u4e5f\u6709\u4e86\u540e\u7eed\u53d1\u9001\u901f\u7387\u7684\u4f9d\u636e\u3002<\/p>\n\n\n\n
\u57fa\u4e8eBBR\u7b97\u6cd5\uff0c\u7531\u4e8e\u74f6\u9888\u8def\u7531\u5668\u7684\u961f\u5217\u4e3a\u7a7a\uff0c\u6700\u76f4\u63a5\u7684\u5f71\u54cd\u5c31\u662fRTT\u5927\u5e45\u4e0b\u964d\uff0c\u53ef\u4ee5\u770b\u5230\u4e0b\u56fe\u4e2dCUBIC\u7ea2\u8272\u7ebf\u6761\u7684RTT\u6bd4BBR\u8981\u9ad8\u5f88\u591a\uff1a<\/p>\n\n\n\n
\u800c\u56e0\u4e3a\u6ca1\u6709\u4e22\u5305\uff0cBBR\u4f20\u8f93\u901f\u7387\u4e5f\u4f1a\u6709\u5927\u5e45\u63d0\u5347\uff0c\u4e0b\u56fe\u4e2d\u63d2\u5165\u7684\u56fe\u4e3aCDF\u7d2f\u79ef\u6982\u7387\u5206\u5e03\u51fd\u6570\uff0c\u4eceCDF\u4e2d\u53ef\u4ee5\u5f88\u6e05\u6670\u7684\u770b\u5230CUBIC\u4e0b\u5927\u90e8\u5206\u8fde\u63a5\u7684\u541e\u5410\u91cf\u90fd\u66f4\u4f4e\uff1a<\/p>\n\n\n\n
\u5982\u679c\u94fe\u8def\u53d1\u751f\u4e86\u5207\u6362\uff0c\u65b0\u7684\u74f6\u9888\u5e26\u5bbd\u5347\u5927\u6216\u8005\u53d8\u5c0f\u600e\u4e48\u529e\u5462\uff1fBBR\u4f1a\u5c1d\u8bd5\u5468\u671f\u6027\u7684\u63a2\u6d4b\u65b0\u7684\u74f6\u9888\u5e26\u5bbd\uff0c\u8fd9\u4e2a\u5468\u671f\u503c\u4e3a1.25\u30010.75\u30011\u30011\u30011\u30011\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n\n\n\n
1.25\u4f1a\u4f7f\u5f97BBR\u5c1d\u8bd5\u53d1\u9001\u66f4\u591a\u7684\u98de\u884c\u4e2d\u62a5\u6587\uff0c\u800c\u5982\u679c\u4ea7\u751f\u4e86\u961f\u5217\u79ef\u538b\uff0c0.75\u5219\u4f1a\u91ca\u653e\u961f\u5217\u3002\u4e0b\u56fe\u4e2d\u662f\u5148\u4ee510Mbps\u7684\u94fe\u8def\u4f20\u8f93TCP\uff0c\u5728\u7b2c20\u79d2\u7f51\u7edc\u5207\u6362\u5230\u4e86\u66f4\u5feb\u768440Mbps\u94fe\u8def\uff0c\u7531\u4e8e1.25\u7684\u5b58\u5728BBR\u5f88\u5feb\u53d1\u73b0\u4e86\u66f4\u5927\u7684\u5e26\u5bbd\uff0c\u800c\u7b2c40\u79d2\u53c8\u5207\u6362\u56de\u4e8610Mbps\u94fe\u8def\uff0c2\u79d2\u5185\u7531\u4e8eRTT\u7684\u5feb\u901f\u589e\u52a0BBR\u8c03\u4f4e\u4e86\u53d1\u9001\u901f\u7387\uff0c\u53ef\u4ee5\u770b\u5230\u7531\u4e8e\u6709\u4e86pacing_gain\u5468\u671f\u53d8\u6362BBR\u5de5\u4f5c\u5f97\u5f88\u597d\u3002<\/p>\n\n\n\n
pacing_gain\u5468\u671f\u8fd8\u6709\u4e2a\u4f18\u70b9\uff0c\u5c31\u662f\u53ef\u4ee5\u4f7f\u591a\u6761\u521d\u59cb\u901f\u5ea6\u4e0d\u540c\u7684TCP\u94fe\u8def\u5feb\u901f\u7684\u5e73\u5747\u5206\u4eab\u5e26\u5bbd\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u540e\u542f\u52a8\u7684\u8fde\u63a5\u7531\u4e8e\u8fc7\u9ad8\u4f30\u8ba1BDP\u4ea7\u751f\u961f\u5217\u79ef\u538b\uff0c\u65e9\u5148\u8fde\u63a5\u7684BBR\u4fbf\u4f1a\u5728\u6570\u4e2a\u5468\u671f\u5185\u5feb\u901f\u964d\u4f4e\u53d1\u9001\u901f\u7387\uff0c\u6700\u7ec8\u7531\u4e8e\u4e0d\u4ea7\u751f\u961f\u5217\u79ef\u538b\u4e0bRTT\u662f\u4e00\u81f4\u7684\uff0c\u6545\u5e73\u8861\u65f65\u6761\u94fe\u8def\u5747\u5206\u4e86\u5e26\u5bbd\uff1a<\/p>\n\n\n\n
\u6211\u4eec\u518d\u6765\u770b\u770b\u6162\u542f\u52a8\u9636\u6bb5\uff0c\u4e0b\u56fe\u7f51\u7edc\u662f10Mbps\u300140ms\uff0c\u56e0\u6b64\u672a\u786e\u8ba4\u7684\u98de\u884c\u5b57\u8282\u6570\u5e94\u4e3a10Mbps*0.04s=0.05MB\u3002\u7ea2\u8272\u7ebf\u6761\u662fCUBIC\u7b97\u6cd5\u4e0b\u5df2\u53d1\u9001\u5b57\u8282\u6570\uff0c\u800c\u84dd\u8272\u662fACK\u5df2\u786e\u8ba4\u5b57\u8282\u6570\uff0c\u7eff\u8272\u5219\u662fBBR\u7b97\u6cd5\u4e0b\u7684\u5df2\u53d1\u9001\u5b57\u8282\u6570\u3002\u663e\u7136\uff0c\u6700\u521dCUBIC\u4e0eBBR\u7b97\u6cd5\u76f8\u540c\uff0c\u57280.25\u79d2\u65f6\u98de\u884c\u5b57\u8282\u6570\u663e\u7136\u8fdc\u8d85\u8fc7\u4e860.05MB\u5b57\u8282\u6570\uff0c\u5927\u7ea6\u5728 0.1MB\u5b57\u8282\u6570\u4e5f\u5c31\u662f2\u500dBDP\uff1a<\/p>\n\n\n\n
\u5927\u7ea6\u57280.3\u79d2\u65f6\uff0cCUBIC\u5f00\u59cb\u7ebf\u6027\u589e\u52a0\u62e5\u585e\u7a97\u53e3\uff0c\u800c\u5230\u4e860.5\u79d2\u540eBBR\u5f00\u59cb\u964d\u4f4e\u53d1\u9001\u901f\u7387\uff0c\u5373\u6392\u7a7a\u74f6\u9888\u8def\u7531\u5668\u7684\u62e5\u585e\u961f\u5217\uff0c\u52300.75\u79d2\u65f6\u98de\u884c\u5b57\u8282\u6570\u8c03\u6574\u5230\u4e86BDP\u5927\u5c0f\uff0c\u8fd9\u662f\u6700\u5408\u9002\u7684\u53d1\u9001\u901f\u7387\u3002<\/p>\n\n\n\n
\u5f53\u7e41\u5fd9\u7684\u7f51\u7edc\u51fa\u73b0\u5927\u5e45\u4e22\u5305\u65f6\uff0cBBR\u7684\u8868\u73b0\u4e5f\u8fdc\u597d\u4e8eCUBIC\u7b97\u6cd5\u3002\u4e0b\u56fe\u4e2d\uff0c\u4e22\u5305\u7387\u4ece0.001%\u523050%\u65f6\uff0c\u53ef\u4ee5\u770b\u5230\u7eff\u8272\u7684BBR\u8fdc\u597d\u4e8e\u7ea2\u8272\u7684CUBIC\u3002\u5927\u7ea6\u5f53\u4e22\u5305\u7387\u52300.1%\u65f6\uff0cCUBIC\u7531\u4e8e\u4e0d\u505c\u7684\u89e6\u53d1\u62e5\u585e\u7b97\u6cd5\uff0c\u6240\u4ee5\u541e\u5410\u91cf\u6781\u901f\u964d\u523010Mbps\u53ea\u6709\u539f\u5148\u76841\/10\uff0c\u800cBBR\u76f4\u52305%\u4e22\u5305\u7387\u624d\u51fa\u73b0\u660e\u663e\u7684\u541e\u5410\u91cf\u4e0b\u964d\u3002<\/p>\n\n\n\n
CUBIC\u9020\u6210\u74f6\u9888\u8def\u7531\u5668\u7684\u7f13\u51b2\u961f\u5217\u8d8a\u6765\u8d8a\u6ee1\uff0cRTT\u65f6\u5ef6\u5c31\u4f1a\u8d8a\u6765\u8d8a\u5927\uff0c\u800c\u64cd\u4f5c\u7cfb\u7edf\u5bf9\u4e09\u6b21\u63e1\u624b\u7684\u5efa\u7acb\u662f\u6709\u6700\u5927\u65f6\u95f4\u9650\u5236\u7684\uff0c\u8fd9\u5bfc\u81f4\u5efaCUBIC\u4e0b\u7684\u7f51\u7edc\u6781\u7aef\u62e5\u585e\u65f6\uff0c\u65b0\u8fde\u63a5\u5f88\u96be\u5efa\u7acb\u6210\u529f\uff0c\u5982\u4e0b\u56fe\u4e2dRTT\u4e2d\u4f4d\u6570\u8fbe\u5230 100\u79d2\u65f6 Windows\u4fbf\u5f88\u96be\u5efa\u7acb\u6210\u529f\u65b0\u8fde\u63a5\uff0c\u800c200\u79d2\u65f6Linux\/Android\u4e5f\u65e0\u6cd5\u5efa\u7acb\u6210\u529f\u3002<\/p>\n\n\n\n
BBR\u7b97\u6cd5\u7684\u4f2a\u4ee3\u7801\u5982\u4e0b\uff0c\u8fd9\u91cc\u5305\u62ec\u4e24\u4e2a\u6d41\u7a0b\uff0c\u6536\u5230ACK\u786e\u8ba4\u4ee5\u53ca\u53d1\u9001\u62a5\u6587\uff1a<\/p>\n\n\n\n
function onAck(packet)
rtt = now – packet.sendtime
update_min_filter(RTpropFilter, rtt)
delivered += packet.size
delivered_time = now
deliveryRate = (delivered – packet.delivered) \/ (delivered_time – packet.delivered_time)
if (deliveryRate > BtlBwFilter.currentMax || ! packet.app_limited)
update_max_filter(BtlBwFilter, deliveryRate)
if (app_limited_until > 0)
app_limited_until = app_limited_until – packet.size
\u8fd9\u91cc\u7684app_limited_until\u662f\u5728\u5141\u8bb8\u53d1\u9001\u65f6\u89c2\u5bdf\u662f\u5426\u6709\u53d1\u9001\u4efb\u52a1\u51b3\u5b9a\u7684\u3002\u53d1\u9001\u62a5\u6587\u65f6\u4f2a\u7801\u4e3a\uff1a<\/p>\n\n\n\n
function send(packet)
bdp = BtlBwFilter.currentMax \u00d7 RTpropFilter.currentMin
if (inflight >= cwnd_gain \u00d7 bdp)
\/\/ wait for ack or retransmission timeout
return
if (now >= nextSendTime)
packet = nextPacketToSend()
if (! packet)
app_limited_until = inflight
return
packet.app_limited = (app_limited_until > 0)
packet.sendtime = now
packet.delivered = delivered
packet.delivered_time = delivered_time
ship(packet)
nextSendTime = now + packet.size \/ (pacing_gain \u00d7 BtlBwFilter.currentMax)
timerCallbackAt(send, nextSendTime)
pacing_gain\u4fbf\u662f\u51b3\u5b9a\u94fe\u8def\u901f\u7387\u8c03\u6574\u7684\u5173\u952e\u5468\u671f\u6570\u7ec4\u3002<\/p>\n\n\n\n
BBR\u7b97\u6cd5\u5bf9\u7f51\u7edc\u4e16\u754c\u7684\u62e5\u585e\u63a7\u5236\u6709\u91cd\u5927\u610f\u4e49\uff0c\u5c24\u5176\u672a\u6765\u53ef\u4ee5\u60f3\u89c1\u8def\u7531\u5668\u7684\u961f\u5217\u4e00\u5b9a\u4f1a\u8d8a\u6765\u8d8a\u5927\u3002HTTP3\u653e\u5f03\u4e86TCP\u534f\u8bae\uff0c\u8fd9\u610f\u5473\u7740\u5b83\u9700\u8981\u5728\u5e94\u7528\u5c42\uff08\u5404\u6846\u67b6\u4e2d\u95f4\u4ef6\uff09\u4e2d\u57fa\u4e8eBBR\u7b97\u6cd5\u5b9e\u73b0\u62e5\u585e\u63a7\u5236\uff0c\u6240\u4ee5\uff0cBBR\u7b97\u6cd5\u5176\u5b9e\u79bb\u6211\u4eec\u5f88\u8fd1\u3002\u7406\u89e3BBR\uff0c\u6211\u4eec\u4fbf\u80fd\u66f4\u597d\u7684\u5e94\u5bf9\u7f51\u7edc\u62e5\u585e\u5bfc\u81f4\u7684\u6027\u80fd\u95ee\u9898\uff0c\u4e5f\u4f1a\u5bf9\u672a\u6765\u7684\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\u53d1\u5c55\u8109\u7edc\u66f4\u6e05\u6670\u3002
\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014
\u7248\u6743\u58f0\u660e\uff1a\u672c\u6587\u4e3aCSDN\u535a\u4e3b\u300c\u9676\u8f89\u300d\u7684\u539f\u521b\u6587\u7ae0\uff0c\u9075\u5faaCC 4.0 BY-SA\u7248\u6743\u534f\u8bae\uff0c\u8f6c\u8f7d\u8bf7\u9644\u4e0a\u539f\u6587\u51fa\u5904\u94fe\u63a5\u53ca\u672c\u58f0\u660e\u3002
\u539f\u6587\u94fe\u63a5\uff1ahttps:\/\/blog.csdn.net\/russell_tao\/article\/details\/98723451<\/p>\n","protected":false},"excerpt":{"rendered":"
BBR\u5bf9TCP\u6027\u80fd\u7684\u63d0\u5347\u662f\u5de8\u5927\u7684\uff0c\u5b83\u80fd\u66f4\u6709\u6548\u7684\u4f7f\u7528\u5f53\u4e0b\u7f51\u7edc\u73af\u5883\uff0cYoutube\u5e94\u7528\u540e\u5728\u541e\u5410\u91cf\u4e0a\u6709\u5e73\u57474%\u63d0\u5347\uff08 … \u9605\u8bfb\u66f4\u591a<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_kadence_starter_templates_imported_post":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-496","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/posts\/496","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=496"}],"version-history":[{"count":1,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/posts\/496\/revisions"}],"predecessor-version":[{"id":497,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=\/wp\/v2\/posts\/496\/revisions\/497"}],"wp:attachment":[{"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=496"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=496"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/airy.cn\/WordPress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=496"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}