{"id":63,"date":"2026-09-04T18:39:00","date_gmt":"2026-09-04T10:39:00","guid":{"rendered":"https:\/\/www.oldhamburger.cn\/?p=63"},"modified":"2026-09-04T18:39:00","modified_gmt":"2026-09-04T10:39:00","slug":"tcp-protocol-handshake-reliability-congestion-control","status":"publish","type":"post","link":"https:\/\/www.oldhamburger.cn\/index.php\/2026\/09\/04\/tcp-protocol-handshake-reliability-congestion-control\/","title":{"rendered":"TCP \u534f\u8bae\u8be6\u89e3\uff1a\u4ece\u4e09\u6b21\u63e1\u624b\u3001\u53ef\u9760\u4f20\u8f93\u5230\u62e5\u585e\u63a7\u5236"},"content":{"rendered":"

<\/p>\n

\u5f53\u6d4f\u89c8\u5668\u8bbf\u95ee\u7f51\u7ad9\u3001\u5ba2\u6237\u7aef\u8fde\u63a5\u6570\u636e\u5e93\uff0c\u6216\u8005\u7a0b\u5e8f\u901a\u8fc7 Socket \u4ea4\u6362\u6570\u636e\u65f6\uff0c\u5e95\u5c42\u7ecf\u5e38\u90fd\u79bb\u4e0d\u5f00 TCP\u3002\u6211\u4eec\u901a\u5e38\u7528\u201c\u9762\u5411\u8fde\u63a5\u3001\u53ef\u9760\u4f20\u8f93\u201d\u6982\u62ec\u5b83\uff0c\u4f46\u771f\u6b63\u6392\u67e5\u7f51\u7edc\u95ee\u9898\u65f6\uff0c\u4ec5\u8bb0\u4f4f\u4e09\u6b21\u63e1\u624b\u548c\u56db\u6b21\u6325\u624b\u8fdc\u8fdc\u4e0d\u591f\u3002<\/p>\n

\u672c\u6587\u4ee5\u73b0\u884c TCP \u4e3b\u89c4\u8303 RFC 9293 \u4e3a\u57fa\u7840\uff0c\u4ece\u62a5\u6587\u9996\u90e8\u3001\u5e8f\u5217\u53f7\u548c\u786e\u8ba4\u673a\u5236\u5f00\u59cb\uff0c\u9010\u6b65\u89e3\u91ca\u8fde\u63a5\u5efa\u7acb\u3001\u4e22\u5305\u91cd\u4f20\u3001\u6d41\u91cf\u63a7\u5236\u3001\u62e5\u585e\u63a7\u5236\u3001\u8fde\u63a5\u91ca\u653e\u53ca\u5e38\u89c1\u7f16\u7a0b\u9677\u9631\u3002\u8bfb\u5b8c\u540e\uff0c\u4f60\u5e94\u8be5\u80fd\u591f\u770b\u61c2\u4e00\u6761 TCP \u6d41\uff0c\u5e76\u77e5\u9053\u9047\u5230\u8d85\u65f6\u3001\u91cd\u4f20\u3001\u7c98\u5305\u3001TIME_WAIT \u6216 CLOSE_WAIT \u65f6\u8be5\u4ece\u54ea\u91cc\u5165\u624b\u3002<\/p>\n

\u4e00\u3001TCP \u5230\u5e95\u63d0\u4f9b\u4e86\u4ec0\u4e48<\/h2>\n

TCP \u4f4d\u4e8e\u4f20\u8f93\u5c42\u3002IP \u8d1f\u8d23\u628a\u6570\u636e\u62a5\u9001\u5f80\u76ee\u6807\u4e3b\u673a\uff0cTCP \u5219\u5728\u7aef\u70b9\u4e4b\u95f4\u63d0\u4f9b\u53ef\u9760\u3001\u6309\u5e8f\u3001\u5168\u53cc\u5de5\u7684\u5b57\u8282\u6d41<\/strong>\u3002\u5e94\u7528\u5199\u5165\u7684\u662f\u4e00\u4e32\u8fde\u7eed\u5b57\u8282\uff0cTCP \u4f1a\u6839\u636e\u8def\u5f84\u548c\u534f\u8bae\u72b6\u6001\u628a\u5b83\u4eec\u5207\u5206\u4e3a\u82e5\u5e72\u62a5\u6587\u6bb5\uff0c\u518d\u4ea4\u7ed9 IP \u53d1\u9001\u3002<\/p>\n

\u4e00\u6761 TCP \u8fde\u63a5\u901a\u5e38\u7531\u56db\u5143\u7ec4\u552f\u4e00\u6807\u8bc6\uff1a<\/p>\n

(\u6e90 IP, \u6e90\u7aef\u53e3, \u76ee\u7684 IP, \u76ee\u7684\u7aef\u53e3)<\/code><\/pre>\n
\u7f51\u7edc\u5206\u6790\u4e2d\u4e5f\u5e38\u52a0\u5165\u4f20\u8f93\u5c42\u534f\u8bae\uff0c\u79f0\u4e3a\u4e94\u5143\u7ec4\u3002\u5ba2\u6237\u7aef\u901a\u5e38\u4f7f\u7528\u4e34\u65f6\u7aef\u53e3\uff0c\u670d\u52a1\u5668\u76d1\u542c\u56fa\u5b9a\u7aef\u53e3\u3002\u4f8b\u5982\u5ba2\u6237\u7aef 192.0.2.10:52000<\/code> \u53ef\u4ee5\u8fde\u63a5\u670d\u52a1\u5668 198.51.100.8:443<\/code>\uff1b\u540c\u4e00\u4e2a\u670d\u52a1\u5668\u7aef\u53e3\u80fd\u591f\u540c\u65f6\u670d\u52a1\u5927\u91cf\u4e0d\u540c\u56db\u5143\u7ec4\u7684\u8fde\u63a5\u3002<\/p>\n
TCP \u7684\u80fd\u529b\u8fb9\u754c<\/h3>\n
    \n
  • TCP \u4fdd\u8bc1\u5b57\u8282\u6309\u5e8f\u4ea4\u7ed9\u63a5\u6536\u5e94\u7528\uff0c\u4f46\u4e0d\u4fdd\u7559\u5e94\u7528\u6d88\u606f\u8fb9\u754c<\/strong>\u3002<\/li>\n
  • TCP \u80fd\u68c0\u6d4b\u4f20\u8f93\u9519\u8bef\u5e76\u91cd\u4f20\uff0c\u4f46\u4e0d\u627f\u8bfa\u56fa\u5b9a\u5ef6\u8fdf\uff0c\u4e5f\u4e0d\u5b58\u5728\u201c\u6c38\u4e0d\u5931\u8d25\u201d\u7684\u8fde\u63a5\u3002<\/li>\n
  • TCP \u6821\u9a8c\u548c\u7528\u4e8e\u53d1\u73b0\u4f20\u8f93\u5dee\u9519\uff0c\u4e0d\u63d0\u4f9b\u673a\u5bc6\u6027\u3001\u8eab\u4efd\u8ba4\u8bc1\u6216\u9632\u7be1\u6539\u80fd\u529b\uff1b\u9700\u8981\u5b89\u5168\u901a\u4fe1\u65f6\u5e94\u5728\u4e0a\u5c42\u4f7f\u7528 TLS\u3002<\/li>\n
  • send()<\/code> \u6210\u529f\u901a\u5e38\u53ea\u8bf4\u660e\u6570\u636e\u8fdb\u5165\u4e86\u672c\u673a\u5185\u6838\u7f13\u51b2\u533a\uff0c\u4e0d\u4ee3\u8868\u5bf9\u7aef\u5e94\u7528\u5df2\u7ecf\u8bfb\u53d6\u6216\u5904\u7406\u3002<\/li>\n<\/ul>\n
    \u4e8c\u3001TCP \u9996\u90e8\u7ed3\u6784<\/h2>\n
    \n  
    \"TCP<\/div>
    TCP \u57fa\u672c\u9996\u90e8\u6700\u5c0f\u4e3a 20 \u5b57\u8282\uff0cOptions \u6700\u591a\u53ef\u628a\u9996\u90e8\u6269\u5c55\u5230 60 \u5b57\u8282\u3002<\/figcaption><\/figure>\n
    \n\n\n\n\n\n\n\n\n\n\n\n
    \u5b57\u6bb5<\/th>\n\u957f\u5ea6<\/th>\n\u4f5c\u7528<\/th>\n<\/tr>\n<\/thead>\n
    Source\/Destination Port<\/td>\n\u5404 16 \u4f4d<\/td>\n\u6807\u8bc6\u4e24\u7aef\u5e94\u7528\u8fdb\u7a0b<\/td>\n<\/tr>\n
    Sequence Number<\/td>\n32 \u4f4d<\/td>\n\u672c\u62a5\u6587\u6bb5\u7b2c\u4e00\u4e2a\u6570\u636e\u5b57\u8282\u7684\u5e8f\u53f7\uff1bSYN \u65f6\u8868\u793a\u521d\u59cb\u5e8f\u5217\u53f7<\/td>\n<\/tr>\n
    Acknowledgment Number<\/td>\n32 \u4f4d<\/td>\n\u7d2f\u8ba1\u786e\u8ba4\uff0c\u8868\u793a\u4e0b\u4e00\u6b65\u671f\u671b\u6536\u5230\u7684\u5b57\u8282\u5e8f\u53f7<\/td>\n<\/tr>\n
    Data Offset<\/td>\n4 \u4f4d<\/td>\n\u4ee5 32 \u4f4d\u5b57\u4e3a\u5355\u4f4d\u8868\u793a TCP \u9996\u90e8\u957f\u5ea6<\/td>\n<\/tr>\n
    Window<\/td>\n16 \u4f4d<\/td>\n\u63a5\u6536\u65b9\u901a\u544a\u7684\u53ef\u7528\u63a5\u6536\u7a97\u53e3<\/td>\n<\/tr>\n
    Checksum<\/td>\n16 \u4f4d<\/td>\n\u8986\u76d6 TCP \u9996\u90e8\u3001\u6570\u636e\u548c IP \u4f2a\u9996\u90e8\uff1bTCP \u6821\u9a8c\u548c\u4e0d\u53ef\u7701\u7565<\/td>\n<\/tr>\n
    Options<\/td>\n0\u201340 \u5b57\u8282<\/td>\n\u643a\u5e26 MSS\u3001\u7a97\u53e3\u6269\u5927\u3001SACK\u3001\u65f6\u95f4\u6233\u7b49\u80fd\u529b<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
    \u516b\u4e2a\u5e38\u89c1\u6807\u5fd7\u4f4d<\/h3>\n
    \n\n\n\n\n\n\n\n\n\n\n\n
    \u6807\u5fd7<\/th>\n\u542b\u4e49<\/th>\n\u5e38\u89c1\u573a\u666f<\/th>\n<\/tr>\n<\/thead>\n
    SYN<\/td>\n\u540c\u6b65\u5e8f\u5217\u53f7<\/td>\n\u5efa\u7acb\u8fde\u63a5<\/td>\n<\/tr>\n
    ACK<\/td>\n\u786e\u8ba4\u53f7\u6709\u6548<\/td>\n\u8fde\u63a5\u5efa\u7acb\u540e\u7edd\u5927\u591a\u6570\u62a5\u6587\u90fd\u4f1a\u8bbe\u7f6e<\/td>\n<\/tr>\n
    FIN<\/td>\n\u672c\u65b9\u5411\u6ca1\u6709\u66f4\u591a\u6570\u636e<\/td>\n\u6b63\u5e38\u5173\u95ed\u6216\u534a\u5173\u95ed<\/td>\n<\/tr>\n
    RST<\/td>\n\u7acb\u5373\u91cd\u7f6e\u8fde\u63a5<\/td>\n\u7aef\u53e3\u672a\u76d1\u542c\u3001\u8fde\u63a5\u72b6\u6001\u5f02\u5e38\u3001\u5e94\u7528\u4e2d\u6b62<\/td>\n<\/tr>\n
    PSH<\/td>\n\u63d0\u793a\u63a5\u6536\u7aef\u5c3d\u5feb\u5411\u5e94\u7528\u4ea4\u4ed8<\/td>\n\u4ea4\u4e92\u5f0f\u6570\u636e\uff1b\u4e0d\u80fd\u7528\u6765\u5212\u5206\u6d88\u606f<\/td>\n<\/tr>\n
    URG<\/td>\n\u7d27\u6025\u6307\u9488\u6709\u6548<\/td>\n\u73b0\u4ee3\u5e94\u7528\u8f83\u5c11\u4f7f\u7528<\/td>\n<\/tr>\n
    ECE\/CWR<\/td>\n\u663e\u5f0f\u62e5\u585e\u901a\u77e5\u76f8\u5173<\/td>\n\u7aef\u70b9\u548c\u7f51\u7edc\u652f\u6301 ECN \u65f6\u4f7f\u7528<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
    \u9700\u8981\u7279\u522b\u8bb0\u4f4f\uff1a\u5e8f\u5217\u53f7\u6309\u5b57\u8282<\/strong>\u8ba1\u6570\uff0c\u800c\u4e0d\u662f\u6309\u62a5\u6587\u6bb5\u8ba1\u6570\u3002SYN \u548c FIN \u5404\u81ea\u5360\u7528\u4e00\u4e2a\u5e8f\u53f7\u7a7a\u95f4\uff0c\u7eaf ACK \u4e0d\u5360\u7528\u5e8f\u53f7\u3002\u56e0\u6b64\u63e1\u624b\u65f6\u6536\u5230 Seq=x<\/code> \u7684 SYN\uff0c\u54cd\u5e94\u786e\u8ba4\u53f7\u5c31\u662f Ack=x+1<\/code>\u3002<\/p>\n
    \u4e09\u3001\u4e09\u6b21\u63e1\u624b\uff1a\u540c\u6b65\u4e24\u7aef\u7684\u5e8f\u5217\u53f7<\/h2>\n
    \n  
    \"TCP<\/div>
    \u5178\u578b TCP \u751f\u547d\u5468\u671f\uff1a\u4e09\u6b21\u63e1\u624b\u5efa\u7acb\u8fde\u63a5\uff0c\u53cc\u65b9\u5206\u522b\u7528 FIN \u5173\u95ed\u5404\u81ea\u7684\u53d1\u9001\u65b9\u5411\u3002<\/figcaption><\/figure>\n
    \u5047\u8bbe\u5ba2\u6237\u7aef\u9009\u62e9\u521d\u59cb\u5e8f\u5217\u53f7 x<\/code>\uff0c\u670d\u52a1\u5668\u9009\u62e9 y<\/code>\uff0c\u6700\u57fa\u672c\u7684\u63e1\u624b\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n
      \n
    1. \u5ba2\u6237\u7aef\u53d1\u9001 SYN, Seq=x<\/code>\uff0c\u72b6\u6001\u4ece CLOSED \u8fdb\u5165 SYN-SENT\u3002<\/li>\n
    2. \u670d\u52a1\u5668\u56de\u590d SYN+ACK, Seq=y, Ack=x+1<\/code>\uff0c\u8fdb\u5165 SYN-RECEIVED\u3002<\/li>\n
    3. \u5ba2\u6237\u7aef\u53d1\u9001 ACK, Ack=y+1<\/code>\uff0c\u53cc\u65b9\u968f\u540e\u8fdb\u5165 ESTABLISHED\u3002<\/li>\n<\/ol>\n
      \u4e09\u6b21\u63e1\u624b\u4e0d\u53ea\u662f\u786e\u8ba4\u201c\u670d\u52a1\u5668\u5728\u7ebf\u201d\u3002\u5b83\u8ba9\u53cc\u65b9\u4ea4\u6362\u5e76\u786e\u8ba4\u5404\u81ea\u7684\u521d\u59cb\u5e8f\u5217\u53f7\uff0c\u540c\u65f6\u9a8c\u8bc1\u53cc\u5411\u901a\u4fe1\u8def\u5f84\uff0c\u964d\u4f4e\u7f51\u7edc\u4e2d\u5ef6\u8fdf\u7684\u65e7 SYN \u88ab\u8bef\u8ba4\u4e3a\u65b0\u8fde\u63a5\u7684\u98ce\u9669\u3002\u7b2c\u4e8c\u6b65\u628a\u670d\u52a1\u5668\u7684 SYN \u548c\u5bf9\u5ba2\u6237\u7aef SYN \u7684 ACK \u5408\u5e76\uff0c\u6240\u4ee5\u6700\u7ec8\u662f\u4e09\u4e2a\u62a5\u6587\uff0c\u800c\u4e0d\u662f\u56db\u4e2a\u3002<\/p>\n
      \u63e1\u624b\u65f6\u901a\u5e38\u8fd8\u4f1a\u534f\u5546\u4ec0\u4e48<\/h3>\n
        \n
      • MSS\uff1a<\/strong>\u672c\u7aef\u613f\u610f\u63a5\u6536\u7684\u6700\u5927 TCP \u6570\u636e\u6bb5\u5927\u5c0f\u3002<\/li>\n
      • Window Scale\uff1a<\/strong>\u6269\u5927 16 \u4f4d Window \u5b57\u6bb5\u7684\u8868\u8fbe\u8303\u56f4\uff1b\u53ea\u80fd\u5728 SYN \u4e2d\u534f\u5546\u3002<\/li>\n
      • SACK Permitted\uff1a<\/strong>\u8868\u793a\u540e\u7eed\u53ef\u4ee5\u4f7f\u7528\u9009\u62e9\u6027\u786e\u8ba4\u3002<\/li>\n
      • Timestamps\uff1a<\/strong>\u7528\u4e8e\u66f4\u7cbe\u786e\u7684 RTT \u6d4b\u91cf\u548c\u9632\u6b62\u5e8f\u5217\u53f7\u56de\u7ed5\u9020\u6210\u6b67\u4e49\u3002<\/li>\n<\/ul>\n
        \u8fd9\u4e9b\u9009\u9879\u5982\u679c\u6ca1\u6709\u5728\u63e1\u624b\u9636\u6bb5\u534f\u5546\u6210\u529f\uff0c\u4e0d\u80fd\u5728\u8fde\u63a5\u4e2d\u9014\u968f\u610f\u5f00\u542f\u3002\u6293\u5305\u5206\u6790\u6027\u80fd\u95ee\u9898\u65f6\uff0c\u5e94\u5148\u770b SYN\/SYN-ACK \u4e2d\u53cc\u65b9\u5b9e\u9645\u8c08\u6210\u4e86\u54ea\u4e9b\u80fd\u529b\u3002<\/p>\n
        \u56db\u3001TCP \u5982\u4f55\u505a\u5230\u53ef\u9760\u4f20\u8f93<\/h2>\n
        \n  
        \"TCP<\/div>
        \u7d2f\u8ba1 ACK \u53ea\u786e\u8ba4\u8fde\u7eed\u5b57\u8282\uff1bSACK \u80fd\u989d\u5916\u62a5\u544a\u5df2\u6536\u5230\u7684\u975e\u8fde\u7eed\u533a\u95f4\u3002<\/figcaption><\/figure>\n
        1. \u5e8f\u5217\u53f7\u3001\u7d2f\u8ba1 ACK \u4e0e\u4e71\u5e8f\u91cd\u7ec4<\/h3>\n
        \u5982\u679c\u63a5\u6536\u65b9\u5df2\u7ecf\u8fde\u7eed\u6536\u5230\u5b57\u8282 [1000, 1500)<\/code>\uff0c\u5b83\u4f1a\u56de\u590d ACK=1500<\/code>\uff0c\u610f\u601d\u662f\u201c1500 \u4e4b\u524d\u90fd\u6536\u5230\u4e86\uff0c\u8bf7\u4ece 1500 \u7ee7\u7eed\u201d\u3002\u82e5 [1500, 2000)<\/code> \u4e22\u5931\uff0c\u800c [2000, 2500)<\/code> \u5148\u5230\u8fbe\uff0c\u63a5\u6536\u65b9\u53ef\u4ee5\u7f13\u5b58\u4e71\u5e8f\u6570\u636e\uff0c\u4f46\u7d2f\u8ba1\u786e\u8ba4\u53f7\u4ecd\u4fdd\u6301 1500\u3002<\/p>\n
        \u534f\u5546 SACK \u540e\uff0c\u63a5\u6536\u65b9\u8fd8\u53ef\u4ee5\u540c\u65f6\u62a5\u544a SACK [2000, 2500)<\/code>\uff0c\u544a\u8bc9\u53d1\u9001\u65b9\u540e\u4e00\u6bb5\u5df2\u7ecf\u6536\u5230\u3002\u8fd9\u6837\u53d1\u9001\u65b9\u53ea\u9700\u8981\u8865\u53d1\u7f3a\u53e3\uff0c\u4e0d\u5fc5\u76f2\u76ee\u91cd\u4f20\u6574\u7247\u7a97\u53e3\u3002SACK \u4e0d\u4f1a\u6539\u53d8\u7d2f\u8ba1 ACK \u5b57\u6bb5\u539f\u6709\u7684\u542b\u4e49\u3002<\/p>\n
        2. \u6821\u9a8c\u548c\u3001\u53bb\u91cd\u4e0e\u6309\u5e8f\u4ea4\u4ed8<\/h3>\n
        \u63a5\u6536\u7aef\u6821\u9a8c\u62a5\u6587\uff1b\u635f\u574f\u7684\u6570\u636e\u4e0d\u4f1a\u4f5c\u4e3a\u6709\u6548\u5b57\u8282\u4ea4\u4ed8\u3002\u5e8f\u5217\u53f7\u8fd8\u8ba9\u63a5\u6536\u7aef\u8bc6\u522b\u91cd\u590d\u62a5\u6587\uff0c\u5e76\u628a\u4e71\u5e8f\u5230\u8fbe\u7684\u6570\u636e\u91cd\u65b0\u6392\u5217\u3002\u53ea\u6709\u4ece\u5f53\u524d\u671f\u671b\u5e8f\u53f7\u5f00\u59cb\u7684\u8fde\u7eed\u5b57\u8282\uff0c\u624d\u53ef\u4ee5\u6309\u5e8f\u63a8\u8fdb\u7d2f\u8ba1 ACK \u5e76\u4ea4\u7ed9\u5e94\u7528\u3002<\/p>\n
        3. \u8d85\u65f6\u91cd\u4f20\u4e0e RTO<\/h3>\n
        \u53d1\u9001\u65b9\u4e3a\u672a\u786e\u8ba4\u6570\u636e\u7ef4\u62a4\u91cd\u4f20\u8ba1\u65f6\u5668\u3002RTO \u4e0d\u662f\u56fa\u5b9a\u62cd\u8111\u888b\u503c\uff0c\u800c\u662f\u6839\u636e\u5f80\u8fd4\u65f6\u95f4 RTT \u7684\u6d4b\u91cf\u52a8\u6001\u8ba1\u7b97\u3002RFC 6298 \u7ed9\u51fa\u7684\u57fa\u672c\u601d\u8def\u662f\u5e73\u6ed1 RTT \u4e0e RTT \u6ce2\u52a8\uff1a<\/p>\n
        \u9996\u6b21\u6d4b\u91cf R\uff1a\nSRTT   = R\nRTTVAR = R \/ 2\nRTO    = SRTT + max(G, 4 \u00d7 RTTVAR)\n\n\u540e\u7eed\u6d4b\u91cf R'\uff1a\nRTTVAR = 3\/4 \u00d7 RTTVAR + 1\/4 \u00d7 |SRTT - R'|\nSRTT   = 7\/8 \u00d7 SRTT   + 1\/8 \u00d7 R'\nRTO    = SRTT + max(G, 4 \u00d7 RTTVAR)<\/code><\/pre>\n
        G<\/code> \u662f\u65f6\u949f\u7c92\u5ea6\u3002RFC 6298 \u7684\u6807\u51c6\u7b97\u6cd5\u8981\u6c42\u8ba1\u7b97\u7ed3\u679c\u5c0f\u4e8e 1 \u79d2\u65f6\u628a RTO \u5411\u4e0a\u53d6\u5230 1 \u79d2\uff0c\u5b9e\u73b0\u4e5f\u53ef\u4ee5\u91c7\u7528\u66f4\u4fdd\u5b88\u7684\u503c\u3002\u53d1\u751f RTO \u8d85\u65f6\u540e\uff0c\u91cd\u4f20\u8ba1\u65f6\u901a\u5e38\u6307\u6570\u9000\u907f\uff0c\u907f\u514d\u5728\u5df2\u7ecf\u62e5\u585e\u7684\u7f51\u7edc\u4e2d\u6301\u7eed\u52a0\u538b\u3002\u5bf9\u53d1\u751f\u8fc7\u91cd\u4f20\u7684\u6570\u636e\uff0c\u9664\u975e\u4f7f\u7528\u65f6\u95f4\u6233\u7b49\u673a\u5236\u6d88\u9664\u6b67\u4e49\uff0c\u5426\u5219\u4e0d\u80fd\u7b80\u5355\u5224\u65ad\u67d0\u4e2a ACK \u5bf9\u5e94\u539f\u59cb\u62a5\u6587\u8fd8\u662f\u91cd\u4f20\u62a5\u6587\uff0c\u56e0\u6b64\u4e0d\u80fd\u76f4\u63a5\u62ff\u6765\u91c7\u6837 RTT\u3002<\/p>\n
        4. \u5feb\u901f\u91cd\u4f20<\/h3>\n
        \u7b49\u5f85 RTO \u53ef\u80fd\u5f88\u6162\u3002\u7ecf\u5178 RFC 5681 \u7b97\u6cd5\u4e2d\uff0c\u53d1\u9001\u65b9\u6536\u5230 3 \u4e2a\u91cd\u590d ACK \u540e\uff0c\u4f1a\u8ba4\u4e3a\u786e\u8ba4\u53f7\u5bf9\u5e94\u7684\u7f3a\u53e3\u5f88\u53ef\u80fd\u5df2\u7ecf\u4e22\u5931\uff0c\u7acb\u5373\u6267\u884c\u5feb\u901f\u91cd\u4f20\u3002\u73b0\u4ee3\u7cfb\u7edf\u53ef\u80fd\u7ed3\u5408 SACK \u548c\u66f4\u5148\u8fdb\u7684\u4e22\u5305\u68c0\u6d4b\u7b97\u6cd5\uff0c\u4f46\u201c\u91cd\u590d ACK \u8868\u793a\u540e\u7eed\u6570\u636e\u4ecd\u5728\u5230\u8fbe\u3001\u524d\u65b9\u53ef\u80fd\u6709\u7f3a\u53e3\u201d\u8fd9\u4e00\u5224\u65ad\u601d\u8def\u4ecd\u7136\u91cd\u8981\u3002<\/p>\n
        \u4e94\u3001\u6d41\u91cf\u63a7\u5236\u4e0e\u62e5\u585e\u63a7\u5236\u4e0d\u662f\u4e00\u56de\u4e8b<\/h2>\n
        \u8fd9\u4e24\u4e2a\u6982\u5ff5\u7ecf\u5e38\u6df7\u6dc6\uff0c\u4f46\u5b83\u4eec\u4fdd\u62a4\u7684\u5bf9\u8c61\u4e0d\u540c\uff1a<\/p>\n
        \n\n\n\n\n\n\n
        \u673a\u5236<\/th>\n\u6838\u5fc3\u53d8\u91cf<\/th>\n\u4fdd\u62a4\u5bf9\u8c61<\/th>\n\u4fe1\u606f\u6765\u6e90<\/th>\n<\/tr>\n<\/thead>\n
        \u6d41\u91cf\u63a7\u5236<\/td>\nrwnd<\/code><\/td>\n\u63a5\u6536\u7aef\u7f13\u51b2\u533a\u4e0e\u5904\u7406\u80fd\u529b<\/td>\n\u63a5\u6536\u65b9\u901a\u544a\u7684 Window<\/td>\n<\/tr>\n
        \u62e5\u585e\u63a7\u5236<\/td>\ncwnd<\/code><\/td>\n\u7f51\u7edc\u8def\u5f84\u4e0e\u8def\u7531\u5668\u961f\u5217<\/td>\n\u53d1\u9001\u65b9\u6839\u636e ACK\u3001\u4e22\u5305\u3001ECN \u7b49\u63a8\u65ad<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
        \u53d1\u9001\u65b9\u53ef\u4fdd\u7559\u5728\u9014\u3001\u5c1a\u672a\u786e\u8ba4\u7684\u6570\u636e\u91cf\uff0c\u53d7\u4e24\u8005\u8f83\u5c0f\u503c\u7ea6\u675f\uff1a<\/p>\n
        effective_window = min(rwnd, cwnd)<\/code><\/pre>\n
        \u63a5\u6536\u7a97\u53e3 rwnd<\/h3>\n
        \u63a5\u6536\u5e94\u7528\u6765\u4e0d\u53ca\u8bfb\u53d6\u65f6\uff0c\u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a\u9010\u6e10\u88ab\u5360\u6ee1\uff0c\u901a\u544a\u7a97\u53e3\u4f1a\u7f29\u5c0f\uff0c\u751a\u81f3\u53d8\u6210\u96f6\u3002\u53d1\u9001\u65b9\u6b64\u65f6\u505c\u6b62\u53d1\u9001\u666e\u901a\u6570\u636e\uff0c\u5e76\u901a\u8fc7\u7a97\u53e3\u63a2\u6d4b\u786e\u8ba4\u63a5\u6536\u7a97\u53e3\u4f55\u65f6\u91cd\u65b0\u6253\u5f00\u3002\u6293\u5305\u4e2d\u51fa\u73b0\u5927\u91cf ZeroWindow<\/code>\uff0c\u4f18\u5148\u68c0\u67e5\u63a5\u6536\u5e94\u7528\u662f\u5426\u5904\u7406\u8fc7\u6162\u3001\u963b\u585e\u6216\u7f13\u51b2\u533a\u8bbe\u7f6e\u4e0d\u5408\u7406\u3002<\/p>\n
        \u9996\u90e8\u4e2d\u7684 Window \u53ea\u6709 16 \u4f4d\uff0c\u6700\u5927\u539f\u59cb\u503c\u4e3a 65535\u3002Window Scale \u9009\u9879\u5141\u8bb8\u628a\u5b83\u5de6\u79fb\u6700\u591a 14 \u4f4d\uff0c\u4ee5\u9002\u5e94\u9ad8\u5e26\u5bbd\u65f6\u5ef6\u79ef\u94fe\u8def\uff1b\u7f29\u653e\u56e0\u5b50\u5728\u63e1\u624b\u4e2d\u786e\u5b9a\uff0c\u6293\u5305\u5de5\u5177\u9700\u8981\u7ed3\u5408 SYN \u624d\u80fd\u8fd8\u539f\u771f\u5b9e\u7a97\u53e3\u3002<\/p>\n
        \u62e5\u585e\u7a97\u53e3 cwnd<\/h3>\n
        cwnd<\/code> \u4f4d\u4e8e\u53d1\u9001\u7aef\uff0c\u4e0d\u76f4\u63a5\u5199\u5165 TCP \u9996\u90e8\u3002\u7ecf\u5178\u62e5\u585e\u63a7\u5236\u901a\u5e38\u5305\u542b\uff1a<\/p>\n
          \n
        • \u6162\u542f\u52a8\uff1a<\/strong>\u4ece\u8f83\u5c0f\u7a97\u53e3\u5f00\u59cb\uff0c\u968f ACK \u5230\u6765\u5feb\u901f\u6269\u5927\u7a97\u53e3\uff0c\u6574\u4f53\u4e0a\u8fd1\u4f3c\u6bcf\u4e2a RTT \u6210\u500d\u589e\u957f\u3002<\/li>\n
        • \u62e5\u585e\u907f\u514d\uff1a<\/strong>\u8fbe\u5230\u6162\u542f\u52a8\u9608\u503c ssthresh<\/code> \u540e\u8f6c\u4e3a\u66f4\u5e73\u7f13\u7684\u589e\u957f\u3002<\/li>\n
        • \u5feb\u901f\u91cd\u4f20\uff1a<\/strong>\u7ecf\u5178\u60c5\u51b5\u4e0b\u6536\u5230 3 \u4e2a\u91cd\u590d ACK \u540e\u91cd\u4f20\u7f3a\u5931\u6bb5\u3002<\/li>\n
        • \u5feb\u901f\u6062\u590d\uff1a<\/strong>\u53d1\u73b0\u5355\u4e2a\u4e22\u5305\u65f6\u907f\u514d\u5b8c\u5168\u56de\u5230\u521d\u59cb\u53d1\u9001\u72b6\u6001\uff0c\u5e76\u5728\u4fee\u590d\u540e\u7ee7\u7eed\u4f20\u8f93\u3002<\/li>\n<\/ul>\n
          \u4e0d\u540c\u64cd\u4f5c\u7cfb\u7edf\u53ef\u4ee5\u91c7\u7528\u4e0d\u540c\u7684\u62e5\u585e\u63a7\u5236\u5b9e\u73b0\uff0c\u4f46\u53d1\u9001\u6570\u636e\u65f6\u4ecd\u5fc5\u987b\u540c\u65f6\u5c0a\u91cd\u63a5\u6536\u65b9\u7a97\u53e3\u548c\u7f51\u7edc\u62e5\u585e\u7ea6\u675f\u3002\u9ad8\u541e\u5410\u8fde\u63a5\u4e0d\u4ec5\u9700\u8981\u5e26\u5bbd\uff0c\u8fd8\u9700\u8981\u8db3\u591f\u5927\u7684\u7a97\u53e3\u8986\u76d6\u5e26\u5bbd\u65f6\u5ef6\u79ef\uff1a<\/p>\n
          BDP = bandwidth \u00d7 RTT<\/code><\/pre>\n
          \u4f8b\u5982 100 Mbit\/s\u3001RTT \u4e3a 80 ms \u7684\u8def\u5f84\uff0c\u5e26\u5bbd\u65f6\u5ef6\u79ef\u7ea6\u4e3a 1 MB\u3002\u82e5\u6709\u6548\u7a97\u53e3\u53ea\u6709 64 KB\uff0c\u5373\u4f7f\u94fe\u8def\u6ca1\u6709\u4e22\u5305\uff0c\u4e5f\u96be\u4ee5\u8dd1\u6ee1\u5e26\u5bbd\u3002<\/p>\n
          \u516d\u3001MSS\u3001MTU \u4e0e\u5206\u6bb5<\/h2>\n
          MTU \u662f\u94fe\u8def\u5c42\u4e00\u6b21\u80fd\u591f\u627f\u8f7d\u7684\u6700\u5927 IP \u5305\u5927\u5c0f\uff0cMSS \u662f TCP \u4e00\u6b21\u62a5\u6587\u6bb5\u613f\u610f\u63a5\u6536\u7684\u6700\u5927\u5e94\u7528\u6570\u636e\u5927\u5c0f\u3002\u4ee5\u5e38\u89c1\u4ee5\u592a\u7f51 MTU 1500 \u4e3a\u4f8b\uff1a<\/p>\n
            \n
          • IPv4 \u57fa\u672c\u9996\u90e8 20 \u5b57\u8282 + TCP \u57fa\u672c\u9996\u90e8 20 \u5b57\u8282\uff0c\u5178\u578b MSS \u4e3a 1460\u3002<\/li>\n
          • IPv6 \u57fa\u672c\u9996\u90e8 40 \u5b57\u8282 + TCP \u57fa\u672c\u9996\u90e8 20 \u5b57\u8282\uff0c\u5178\u578b MSS \u4e3a 1440\u3002<\/li>\n<\/ul>\n
            \u5b9e\u9645 TCP \u9009\u9879\u4f1a\u5360\u7528\u989d\u5916\u9996\u90e8\u7a7a\u95f4\uff0c\u534f\u8bae\u6808\u4f1a\u76f8\u5e94\u63a7\u5236\u6570\u636e\u957f\u5ea6\u3002\u8def\u5f84 MTU \u53d1\u73b0\u5931\u8d25\u65f6\uff0c\u53ef\u80fd\u51fa\u73b0\u63e1\u624b\u6210\u529f\u3001\u5c0f\u5305\u6b63\u5e38\u3001\u5927\u6570\u636e\u505c\u4f4f\u7684\u201cPMTU \u9ed1\u6d1e\u201d\u3002\u6392\u67e5\u65f6\u8981\u68c0\u67e5 ICMP \u662f\u5426\u88ab\u9519\u8bef\u5c4f\u853d\u3001\u96a7\u9053\u662f\u5426\u964d\u4f4e MTU\uff0c\u4ee5\u53ca MSS Clamp \u662f\u5426\u5408\u7406\u3002<\/p>\n
            \u8fd8\u8981\u6ce8\u610f\u7f51\u5361\u7684 TSO\/GSO\/GRO\/LRO \u7b49\u5378\u8f7d\u529f\u80fd\u3002\u82e5\u5728\u53d1\u9001\u4e3b\u673a\u672c\u673a\u6293\u5305\uff0c\u53ef\u80fd\u770b\u5230\u8fdc\u5927\u4e8e MTU \u7684\u201cTCP \u62a5\u6587\u201d\uff0c\u90a3\u5f80\u5f80\u53ea\u662f\u5185\u6838\u628a\u5927\u5757\u6570\u636e\u4ea4\u7ed9\u7f51\u5361\u540e\u518d\u5206\u6bb5\uff0c\u5e76\u4e0d\u4ee3\u8868\u8d85\u5927 IP \u5305\u771f\u7684\u4e0a\u4e86\u7ebf\u3002<\/p>\n
            \u4e03\u3001\u4e3a\u4ec0\u4e48\u4f1a\u51fa\u73b0\u201c\u7c98\u5305\u201d\u548c\u201c\u534a\u5305\u201d<\/h2>\n
            \u4e25\u683c\u5730\u8bf4\uff0c\u8fd9\u4e0d\u662f TCP \u534f\u8bae\u6545\u969c\uff0c\u800c\u662f\u5e94\u7528\u628a\u5b57\u8282\u6d41\u8bef\u5f53\u6210\u6d88\u606f\u961f\u5217\u3002\u4e24\u6b21 send()<\/code> \u7684\u6570\u636e\u53ef\u80fd\u5728\u63a5\u6536\u7aef\u4e00\u6b21 recv()<\/code> \u8fd4\u56de\uff0c\u4e5f\u53ef\u80fd\u4e00\u6b21\u53d1\u9001\u88ab\u62c6\u6210\u591a\u6b21\u63a5\u6536\u3002PSH \u6807\u5fd7\u540c\u6837\u4e0d\u80fd\u5145\u5f53\u53ef\u9760\u7684\u5e94\u7528\u6d88\u606f\u8fb9\u754c\u3002<\/p>\n
            \u5e38\u89c1\u7684\u5e94\u7528\u5c42\u5206\u5e27\u65b9\u5f0f\u6709\u4e09\u79cd\uff1a<\/p>\n
              \n
            • \u56fa\u5b9a\u957f\u5ea6\uff1a<\/strong>\u9002\u5408\u6bcf\u6761\u6d88\u606f\u5927\u5c0f\u5b8c\u5168\u4e00\u81f4\u7684\u534f\u8bae\u3002<\/li>\n
            • \u5206\u9694\u7b26\uff1a<\/strong>\u4f8b\u5982\u6587\u672c\u534f\u8bae\u6309 CRLF \u5206\u884c\uff0c\u4f46\u5fc5\u987b\u5904\u7406\u8f6c\u4e49\u548c\u6700\u5927\u957f\u5ea6\u3002<\/li>\n
            • \u957f\u5ea6\u524d\u7f00\uff1a<\/strong>\u5148\u53d1\u9001\u56fa\u5b9a\u5bbd\u5ea6\u7684\u957f\u5ea6\u5b57\u6bb5\uff0c\u518d\u53d1\u9001\u5bf9\u5e94\u5b57\u8282\u6570\u7684\u8d1f\u8f7d\uff0c\u6700\u901a\u7528\u3002<\/li>\n<\/ul>\n
              \u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5316\u7684 Python \u957f\u5ea6\u524d\u7f00\u793a\u4f8b\u3002\u91cd\u70b9\u4e0d\u662f\u8bed\u8a00\uff0c\u800c\u662f\u5fc5\u987b\u5faa\u73af\u63a5\u6536\u76f4\u5230\u62ff\u6ee1\u6307\u5b9a\u957f\u5ea6\uff0c\u5e76\u9650\u5236\u6d88\u606f\u4e0a\u9650\uff1a<\/p>\n
              import struct\n\nMAX_MESSAGE = 4 * 1024 * 1024\n\ndef recv_exact(sock, size):\n    chunks = []\n    remaining = size\n    while remaining:\n        chunk = sock.recv(remaining)\n        if not chunk:\n            raise ConnectionError(\"peer closed the connection\")\n        chunks.append(chunk)\n        remaining -= len(chunk)\n    return b\"\".join(chunks)\n\ndef send_message(sock, payload):\n    if len(payload) > MAX_MESSAGE:\n        raise ValueError(\"message is too large\")\n    sock.sendall(struct.pack(\"!I\", len(payload)) + payload)\n\ndef recv_message(sock):\n    size = struct.unpack(\"!I\", recv_exact(sock, 4))[0]\n    if size > MAX_MESSAGE:\n        raise ValueError(\"message is too large\")\n    return recv_exact(sock, size)<\/code><\/pre>\n
              !I<\/code> \u8868\u793a\u7f51\u7edc\u5b57\u8282\u5e8f\u7684 32 \u4f4d\u65e0\u7b26\u53f7\u957f\u5ea6\u3002\u751f\u4ea7\u4ee3\u7801\u8fd8\u9700\u8981\u8bfb\u5199\u8d85\u65f6\u3001\u53d6\u6d88\u673a\u5236\u3001\u5e76\u53d1\u9650\u5236\u3001\u534f\u8bae\u7248\u672c\u3001\u8ba4\u8bc1\u548c\u9519\u8bef\u54cd\u5e94\u3002<\/p>\n
              \u516b\u3001\u8fde\u63a5\u91ca\u653e\u3001\u534a\u5173\u95ed\u4e0e TIME_WAIT<\/h2>\n
              TCP \u662f\u5168\u53cc\u5de5\u7684\uff0c\u4e24\u4e2a\u53d1\u9001\u65b9\u5411\u9700\u8981\u5206\u522b\u5173\u95ed\u3002\u4e3b\u52a8\u5173\u95ed\u65b9\u53d1\u9001 FIN\uff0c\u53ea\u8868\u793a\u201c\u6211\u4e0d\u4f1a\u518d\u53d1\u9001\u6570\u636e\u201d\uff0c\u4ecd\u53ef\u7ee7\u7eed\u63a5\u6536\u5bf9\u7aef\u6570\u636e\uff0c\u8fd9\u5c31\u662f\u534a\u5173\u95ed\u3002\u56e0\u6b64\u5178\u578b\u6b63\u5e38\u5173\u95ed\u4f1a\u770b\u5230\u56db\u4e2a\u62a5\u6587\uff1a<\/p>\n
              A \u2192 B: FIN + ACK\nB \u2192 A: ACK\nB \u2192 A: FIN + ACK\nA \u2192 B: ACK<\/code><\/pre>\n
              \u7b2c\u4e8c\u4e2a ACK \u53ef\u4ee5\u548c\u540e\u7eed FIN \u5408\u5e76\uff0c\u6240\u4ee5\u5e76\u975e\u6bcf\u6b21\u6293\u5305\u90fd\u4e25\u683c\u51fa\u73b0\u56db\u4e2a\u72ec\u7acb\u62a5\u6587\uff1b\u53cc\u65b9\u4e5f\u53ef\u80fd\u540c\u65f6\u53d1\u9001 FIN\u3002\u5e94\u7528\u53ef\u4ee5\u4f7f\u7528 shutdown()<\/code> \u53ea\u5173\u95ed\u4e00\u4e2a\u65b9\u5411\uff0c\u518d\u7ee7\u7eed\u8bfb\u53d6\u5bf9\u7aef\u5269\u4f59\u54cd\u5e94\u3002<\/p>\n
              TIME_WAIT \u4e3a\u4ec0\u4e48\u5b58\u5728<\/h3>\n
              \u5178\u578b\u60c5\u51b5\u4e0b\uff0c\u53d1\u9001\u6700\u540e ACK \u7684\u4e3b\u52a8\u5173\u95ed\u65b9\u8fdb\u5165 TIME-WAIT\uff0c\u5e76\u7b49\u5f85 2 MSL\u3002\u8fd9\u6837\u65e2\u80fd\u5728\u6700\u540e ACK \u4e22\u5931\u3001\u5bf9\u7aef\u91cd\u53d1 FIN \u65f6\u518d\u6b21\u56de\u5e94\uff0c\u4e5f\u80fd\u8ba9\u7f51\u7edc\u4e2d\u5c5e\u4e8e\u65e7\u8fde\u63a5\u7684\u5ef6\u8fdf\u62a5\u6587\u81ea\u7136\u6d88\u5931\uff0c\u907f\u514d\u6c61\u67d3\u968f\u540e\u590d\u7528\u76f8\u540c\u56db\u5143\u7ec4\u7684\u65b0\u8fde\u63a5\u3002<\/p>\n
              \u5927\u91cf TIME_WAIT \u4e0d\u4e00\u5b9a\u662f\u6545\u969c\uff0c\u5b83\u9996\u5148\u8bf4\u660e\u7cfb\u7edf\u521b\u5efa\u4e86\u5927\u91cf\u77ed\u8fde\u63a5\u4e14\u672c\u7aef\u7ecf\u5e38\u4e3b\u52a8\u5173\u95ed\u3002\u4f18\u5148\u8003\u8651\u8fde\u63a5\u590d\u7528\u3001HTTP Keep-Alive \u6216\u8fde\u63a5\u6c60\uff0c\u5e76\u786e\u8ba4\u5173\u95ed\u8d23\u4efb\u662f\u5426\u5408\u7406\u3002\u4e0d\u8981\u5728\u4e0d\u4e86\u89e3\u8bed\u4e49\u548c\u5b89\u5168\u5f71\u54cd\u65f6\u901a\u8fc7\u7c97\u66b4\u7f29\u77ed\u7b49\u5f85\u65f6\u95f4\u6765\u63a9\u76d6\u67b6\u6784\u95ee\u9898\u3002<\/p>\n
              CLOSE_WAIT \u53c8\u610f\u5473\u7740\u4ec0\u4e48<\/h3>\n
              \u6536\u5230\u5bf9\u7aef FIN \u540e\uff0c\u672c\u7aef\u56de\u590d ACK \u5e76\u8fdb\u5165 CLOSE-WAIT\u3002\u82e5\u8be5\u72b6\u6001\u957f\u671f\u5927\u91cf\u5806\u79ef\uff0c\u901a\u5e38\u662f\u672c\u7aef\u5e94\u7528\u5df2\u7ecf\u77e5\u9053\u5bf9\u65b9\u5173\u95ed\uff0c\u5374\u8fdf\u8fdf\u6ca1\u6709\u8c03\u7528 close()<\/code> \u91ca\u653e\u81ea\u5df1\u7684\u65b9\u5411\uff0c\u5e38\u89c1\u539f\u56e0\u662f\u5f02\u5e38\u8def\u5f84\u9057\u6f0f\u5173\u95ed\u3001\u7ebf\u7a0b\u963b\u585e\u6216\u8d44\u6e90\u751f\u547d\u5468\u671f\u7ba1\u7406\u9519\u8bef\u3002<\/p>\n
              RST \u662f\u5f02\u5e38\u4e2d\u6b62<\/h3>\n
              RST \u4f1a\u7acb\u5373\u7ec8\u6b62\u8fde\u63a5\uff0c\u4e0d\u50cf FIN \u90a3\u6837\u5b8c\u6210\u6709\u5e8f\u5173\u95ed\u3002\u8fde\u63a5\u4e0d\u5b58\u5728\u3001\u76ee\u6807\u7aef\u53e3\u672a\u76d1\u542c\u3001\u5e94\u7528\u8bbe\u7f6e\u5f3a\u5236\u5173\u95ed\uff0c\u6216\u4e00\u7aef\u6536\u5230\u65e0\u6cd5\u5339\u914d\u5f53\u524d\u72b6\u6001\u7684\u62a5\u6587\u65f6\uff0c\u90fd\u53ef\u80fd\u770b\u5230 RST\u3002\u6392\u67e5\u65f6\u5fc5\u987b\u7ed3\u5408 RST \u7531\u54ea\u4e00\u7aef\u53d1\u51fa\u4ee5\u53ca\u5b83\u4e4b\u524d\u7684\u62a5\u6587\u4e0a\u4e0b\u6587\u3002<\/p>\n
              \u4e5d\u3001\u8d85\u65f6\u3001Keepalive \u4e0e\u5e94\u7528\u5fc3\u8df3<\/h2>\n
              TCP \u4e0d\u4f1a\u81ea\u52a8\u7ed9\u4e1a\u52a1\u63d0\u4f9b\u4e00\u4e2a\u4e07\u80fd\u8d85\u65f6\u3002\u53ef\u9760\u7f51\u7edc\u7a0b\u5e8f\u81f3\u5c11\u9700\u8981\u533a\u5206\uff1a<\/p>\n