{"id":2081,"date":"2026-04-21T19:21:02","date_gmt":"2026-04-21T11:21:02","guid":{"rendered":"http:\/\/www.preluna.xyz\/?p=2081"},"modified":"2026-04-24T13:37:20","modified_gmt":"2026-04-24T05:37:20","slug":"ackseqfinrtt","status":"publish","type":"post","link":"http:\/\/www.preluna.xyz\/index.php\/2026\/04\/21\/ackseqfinrtt\/preluna\/text\/","title":{"rendered":"ACK,SEQ,FIN,RTT"},"content":{"rendered":"\n<p>TCP \u6700\u5bb9\u6613\u6df7\u7684\u51e0\u4e2a\u70b9\u4e0a\uff1a<code>SYN\/FIN \u662f\u5426\u5360\u5e8f\u53f7<\/code>\u3001<code>seq \u548c ack \u5230\u5e95\u5404\u8868\u793a\u4ec0\u4e48<\/code>\u3001<code>\u6325\u624b\u65f6 FIN \u5230\u5e95\u610f\u5473\u7740\u4ec0\u4e48<\/code>\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001\u5148\u628a\u6700\u6838\u5fc3\u7684\u89c4\u5219\u634b\u987a\uff1a\u54ea\u4e9b\u4e1c\u897f\u4f1a\u6d88\u8017\u5e8f\u5217\u53f7<\/h2>\n\n\n\n<p>TCP \u7684\u5e8f\u5217\u53f7\u672c\u8d28\u4e0a\u662f\u7ed9\u201c\u5b57\u8282\u6d41\u4f4d\u7f6e\u201d\u7f16\u53f7\u7684\u3002\u901a\u5e38\u6709\u4e24\u7c7b\u4e1c\u897f\u4f1a\u5360\u7528\u4e00\u4e2a\u5e8f\u5217\u53f7\uff1a<\/p>\n\n\n\n<p>\u7b2c\u4e00\u7c7b\u662f\u771f\u6b63\u7684\u6570\u636e\u5b57\u8282\u3002\u53d1\u9001\u4e86\u591a\u5c11\u5b57\u8282\u6570\u636e\uff0c\u5c31\u6d88\u8017\u591a\u5c11\u4e2a\u5e8f\u5217\u53f7\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e8c\u7c7b\u662f\u4e24\u4e2a\u7279\u6b8a\u63a7\u5236\u4f4d\uff1a<code>SYN<\/code> \u548c <code>FIN<\/code>\u3002\u5b83\u4eec\u867d\u7136\u4e0d\u643a\u5e26\u5e94\u7528\u5c42\u6570\u636e\uff0c\u4f46\u90fd\u8981\u5404\u81ea\u5360\u7528 1 \u4e2a\u5e8f\u5217\u53f7\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u8003\u8bd5\u91cc\u4e00\u5b9a\u8981\u8bb0\u4f4f\u4e0b\u9762\u8fd9\u4e09\u6761\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u666e\u901a ACK \u62a5\u6587\u6bb5\u5982\u679c<strong>\u4e0d\u643a\u5e26\u6570\u636e<\/strong>\uff0c\u90a3\u4e48<strong>\u4e0d\u6d88\u8017\u5e8f\u5217\u53f7<\/strong>\u3002<\/li>\n\n\n\n<li><code>SYN=1<\/code> \u7684\u62a5\u6587\u6bb5\uff0c\u5373\u4f7f<strong>\u4e0d\u5e26\u6570\u636e<\/strong>\uff0c\u4e5f<strong>\u6d88\u8017 1 \u4e2a\u5e8f\u5217\u53f7<\/strong>\u3002<\/li>\n\n\n\n<li><code>FIN=1<\/code> \u7684\u62a5\u6587\u6bb5\uff0c\u5373\u4f7f<strong>\u4e0d\u5e26\u6570\u636e<\/strong>\uff0c\u4e5f<strong>\u6d88\u8017 1 \u4e2a\u5e8f\u5217\u53f7<\/strong>\u3002<\/li>\n<\/ol>\n\n\n\n<p>\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48\u5927\u5bb6\u5e38\u8bf4\uff1a<\/p>\n\n\n\n<p><code>\u6570\u636e\u6d88\u8017\u591a\u5c11\uff0c\u5e8f\u53f7\u5c31\u524d\u8fdb\u591a\u5c11\uff1bSYN \u548c FIN \u5404\u989d\u5916\u518d\u52a0 1\uff1b\u7eaf ACK \u4e0d\u52a0\u3002<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001\u4e3a\u4ec0\u4e48 SYN \u548c FIN \u660e\u660e\u201c\u4e0d\u5e26\u6570\u636e\u201d\u5374\u8fd8\u5360\u4e00\u4e2a\u5e8f\u53f7<\/h2>\n\n\n\n<p>\u8fd9\u4e0d\u662f\u968f\u4fbf\u89c4\u5b9a\u7684\uff0c\u800c\u662f TCP \u534f\u8bae\u4e3a\u4e86\u4fdd\u8bc1\u8fde\u63a5\u5efa\u7acb\u3001\u8fde\u63a5\u91ca\u653e\u4e5f\u80fd\u88ab\u53ef\u9760\u786e\u8ba4\u3002<\/p>\n\n\n\n<p>\u53ef\u4ee5\u628a\u5b83\u7406\u89e3\u6210\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>SYN<\/code>\uff1a\u5360\u4e00\u4e2a\u201c\u5efa\u7acb\u8fde\u63a5\u201d\u7684\u903b\u8f91\u4f4d\u7f6e<\/li>\n\n\n\n<li><code>FIN<\/code>\uff1a\u5360\u4e00\u4e2a\u201c\u7ed3\u675f\u53d1\u9001\u201d\u7684\u903b\u8f91\u4f4d\u7f6e<\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u6b64\u5bf9\u65b9\u786e\u8ba4\u65f6\uff0c\u4e5f\u5fc5\u987b\u628a\u8fd9\u4e00\u4e2a\u4f4d\u7f6e\u786e\u8ba4\u6389\uff0c\u6240\u4ee5\u786e\u8ba4\u53f7\u4f1a\u52a0 1\u3002<\/p>\n\n\n\n<p>\u8fd9\u6b63\u662f\u5f88\u591a\u9898\u76ee\u7684\u9677\u9631\u6765\u6e90\uff1a<br><strong>\u4e0d\u8981\u628a\u201c\u662f\u5426\u5e26\u6570\u636e\u201d\u548c\u201c\u662f\u5426\u5360\u5e8f\u53f7\u201d\u753b\u7b49\u53f7\u3002<\/strong><br>\u56e0\u4e3a <code>SYN<\/code>\u3001<code>FIN<\/code> \u5c31\u662f\u201c\u4e0d\u5e26\u6570\u636e\u4f46\u5360\u5e8f\u53f7\u201d\u7684\u5178\u578b\u4f8b\u5916\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u7b2c\u4e00\u9053\u4f8b\u9898\uff1a\u5982\u4f55\u6839\u636e SYN \u548c\u7b2c 4 \u6b21\u6325\u624b\u6c42 A \u53d1\u4e86\u591a\u5c11\u5b57\u8282\u6570\u636e<\/h2>\n\n\n\n<p>\u9898\u76ee\u662f\uff1a<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u4e3b\u673a A \u548c B \u4e4b\u95f4\u5efa\u7acb\u4e86\u4e00\u4e2a TCP \u8fde\u63a5\uff0cA \u5411 B \u53d1\u9001\u7684\u7b2c\u4e00\u4e2a SYN \u62a5\u6587\u6bb5\u4e2d\u7684\u5e8f\u53f7\u503c seq = 211\uff0c\u6570\u636e\u4f20\u8f93\u7ed3\u675f\uff0c\u5728\u91ca\u653e\u8fde\u63a5\u65f6\uff0cA \u5411 B \u53d1\u9001\u7684\u7b2c 4 \u6b21\u6325\u624b\u62a5\u6587\u6bb5\u7684 seq = 985\uff0c\u5219\u5728\u672c\u6b21\u901a\u4fe1\u8fc7\u7a0b\u4e2d\uff0cA \u5411 B \u603b\u5171\u53d1\u9001\u4e86\u591a\u5c11\u5b57\u8282\u7684\u6570\u636e\uff1f<\/p>\n<\/blockquote>\n\n\n\n<p>\u8fd9\u9898\u7684\u5173\u952e\u4e0d\u662f\u201c\u7b2c 4 \u6b21\u6325\u624b\u201d\uff0c\u800c\u662f\u8981\u77e5\u9053\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A \u6700\u5f00\u59cb\u53d1\u4e86\u4e00\u4e2a <code>SYN<\/code><\/li>\n\n\n\n<li>A \u540e\u9762\u53d1\u9001\u4e86\u82e5\u5e72\u6570\u636e<\/li>\n\n\n\n<li>\u5982\u679c A \u53d1\u7684\u662f\u7b2c 4 \u6b21\u6325\u624b\u62a5\u6587\u6bb5\uff0c\u8bf4\u660e A \u662f\u6700\u540e\u53d1 ACK \u7684\u4e00\u65b9\uff0c\u4e5f\u5c31\u662f\u901a\u5e38\u7684\u4e3b\u52a8\u5173\u95ed\u65b9 A\uff1a<br>\u7b2c 1 \u6b21\u6325\u624b A \u53d1 <code>FIN<\/code><br>\u7b2c 4 \u6b21\u6325\u624b A \u518d\u53d1\u4e00\u4e2a\u7eaf ACK<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u91cc\u6700\u5173\u952e\u7684\u4e00\u70b9\u662f\uff1a<\/p>\n\n\n\n<p><strong>\u7b2c 4 \u6b21\u6325\u624b\u662f\u7eaf ACK\uff0c\u4e0d\u6d88\u8017\u5e8f\u5217\u53f7\u3002<\/strong><br>\u6240\u4ee5\u7b2c 4 \u6b21\u6325\u624b\u7684 <code>seq<\/code>\uff0c\u5b9e\u9645\u4e0a\u7b49\u4e8e A \u5728\u53d1\u9001\u5b8c FIN \u4e4b\u540e\u201c\u4e0b\u4e00\u4e2a\u53ef\u7528\u5e8f\u5217\u53f7\u201d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u5206\u6b65\u63a8<\/h3>\n\n\n\n<p>A \u53d1\u7684\u7b2c\u4e00\u4e2a SYN\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq = 211<\/code><\/li>\n\n\n\n<li>\u7531\u4e8e SYN \u5360 1 \u4e2a\u5e8f\u5217\u53f7\uff0c\u6240\u4ee5\u4e4b\u540e A \u7684\u4e0b\u4e00\u4e2a\u5e8f\u53f7\u53d8\u6210 <code>212<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u8bbe A \u603b\u5171\u53d1\u9001\u4e86 <code>x<\/code> \u5b57\u8282\u6570\u636e\uff0c\u90a3\u4e48\u6570\u636e\u53d1\u5b8c\u540e\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5e8f\u53f7\u524d\u8fdb\u5230 <code>212 + x<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u7136\u540e A \u53d1\u9001\u7b2c 1 \u6b21\u6325\u624b\u7684 <code>FIN<\/code>\uff0cFIN \u8fd8\u8981\u518d\u5360 1 \u4e2a\u5e8f\u5217\u53f7\uff0c\u6240\u4ee5\u53d1\u5b8c FIN \u4ee5\u540e\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e0b\u4e00\u4e2a\u5e8f\u53f7\u53d8\u6210 <code>213 + x<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u800c\u7b2c 4 \u6b21\u6325\u624b\u662f\u7eaf ACK\uff0c\u4e0d\u6d88\u8017\u5e8f\u53f7\uff0c\u56e0\u6b64\u5b83\u7684 <code>seq<\/code> \u5c31\u5e94\u8be5\u662f\uff1a<\/p>\n\n\n\n<p><code>213 + x = 985<\/code><\/p>\n\n\n\n<p>\u89e3\u5f97\uff1a<\/p>\n\n\n\n<p><code>x = 985 - 213 = 772<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>A \u5411 B \u603b\u5171\u53d1\u9001\u4e86 <strong>772B<\/strong> \u7684\u6570\u636e\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u8fd9\u7c7b\u9898\u7684\u901a\u7528\u6a21\u677f<\/h3>\n\n\n\n<p>\u53ea\u8981\u9898\u76ee\u4ece\u201c\u521d\u59cb SYN \u7684 seq\u201d\u8df3\u5230\u201c\u540e\u9762\u67d0\u4e2a ACK\/FIN \u7684 seq\u201d\uff0c\u5c31\u6309\u4e0b\u9762\u7684\u5f0f\u5b50\u60f3\uff1a<\/p>\n\n\n\n<p><code>\u540e\u9762\u7684 seq = \u521d\u59cb SYN \u7684 seq + 1 + \u6570\u636e\u5b57\u8282\u6570 + \u662f\u5426\u53d1\u8fc7 FIN<\/code><\/p>\n\n\n\n<p>\u8fd9\u91cc\u201c\u662f\u5426\u53d1\u8fc7 FIN\u201d\u5982\u679c\u53d1\u8fc7\uff0c\u5c31\u518d\u52a0 1\u3002<\/p>\n\n\n\n<p>\u672c\u9898\u91cc\u6b63\u597d\u662f\uff1a<\/p>\n\n\n\n<p><code>985 = 211 + 1 + \u6570\u636e\u5b57\u8282\u6570 + 1<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u6570\u636e\u5b57\u8282\u6570\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>985 - 211 - 2 = 772<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u6613\u9519\u70b9<\/h3>\n\n\n\n<p>\u6700\u5bb9\u6613\u9519\u6210 773 \u6216 774\uff0c\u539f\u56e0\u4e00\u822c\u6709\u4e24\u4e2a\uff1a<\/p>\n\n\n\n<p>\u7b2c\u4e00\u79cd\u9519\u6cd5\uff1a\u5fd8\u4e86 SYN \u5360 1\u3002<br>\u7b2c\u4e8c\u79cd\u9519\u6cd5\uff1a\u5fd8\u4e86 FIN \u4e5f\u5360 1\u3002<br>\u7b2c\u4e09\u79cd\u9519\u6cd5\uff1a\u8bef\u4ee5\u4e3a\u7b2c 4 \u6b21\u6325\u624b\u90a3\u4e2a ACK \u4e5f\u8981\u5360 1\uff0c\u5176\u5b9e\u7eaf ACK \u4e0d\u5360\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001seq \u548c ack \u5230\u5e95\u662f\u4ec0\u4e48\u5173\u7cfb<\/h2>\n\n\n\n<p>\u4f60\u63d0\u5230\u4e00\u53e5\u975e\u5e38\u5173\u952e\u7684\u8bdd\uff1a<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u540c\u4e00\u4e2a\u62a5\u6587\u6bb5\u4e2d\uff0cseq \u548c ack \u6ca1\u6709\u4efb\u4f55\u8054\u7cfb<\/p>\n<\/blockquote>\n\n\n\n<p>\u8fd9\u4e2a\u8bf4\u6cd5\u5728\u505a\u9898\u610f\u4e49\u4e0a\uff0c\u57fa\u672c\u53ef\u4ee5\u8ba4\u4e3a\u662f\u5bf9\u7684\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1\uff09seq \u8868\u793a\u4ec0\u4e48<\/h3>\n\n\n\n<p><code>seq<\/code> \u8868\u793a\uff1a<strong>\u672c\u62a5\u6587\u6bb5\u6570\u636e\u90e8\u5206\u7684\u7b2c\u4e00\u4e2a\u5b57\u8282\u7684\u5e8f\u53f7<\/strong>\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u672c\u62a5\u6587\u6bb5\u4e0d\u5e26\u6570\u636e\uff0c\u4f46\u5e26 SYN \u6216 FIN\uff0c\u90a3\u4e48\u5b83\u8868\u793a\u7684\u5c31\u662f\u8fd9\u4e2a SYN \u6216 FIN \u5360\u7528\u7684\u90a3\u4e2a\u5e8f\u53f7\u4f4d\u7f6e\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5 <code>seq<\/code> \u770b\u7684\u662f\u201c\u6211\u8fd9\u8fb9\u53d1\u51fa\u53bb\u7684\u5185\u5bb9\uff0c\u4ece\u54ea\u4e00\u4e2a\u7f16\u53f7\u5f00\u59cb\u201d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2\uff09ack \u8868\u793a\u4ec0\u4e48<\/h3>\n\n\n\n<p><code>ack<\/code> \u8868\u793a\uff1a<strong>\u6211\u671f\u671b\u6536\u5230\u5bf9\u65b9\u4e0b\u4e00\u4e2a\u5b57\u8282\u7684\u5e8f\u53f7<\/strong>\u3002<\/p>\n\n\n\n<p>\u6362\u53e5\u8bdd\u8bf4\uff0c<code>ack = \u5df2\u7ecf\u6b63\u786e\u6536\u5230\u5bf9\u65b9\u7684\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7 + 1<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5 <code>ack<\/code> \u770b\u7684\u662f\u201c\u6211\u5df2\u7ecf\u6536\u5230\u4e86\u4f60\u54ea\u513f\uff0c\u4f60\u63a5\u4e0b\u6765\u8be5\u4ece\u54ea\u513f\u7ee7\u7eed\u53d1\u201d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3\uff09\u4e3a\u4ec0\u4e48\u8bf4\u540c\u4e00\u4e2a\u62a5\u6587\u6bb5\u4e2d\u7684 seq \u548c ack \u6ca1\u76f4\u63a5\u5173\u7cfb<\/h3>\n\n\n\n<p>\u56e0\u4e3a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq<\/code> \u662f\u63cf\u8ff0<strong>\u81ea\u5df1\u53d1\u51fa\u7684\u6570\u636e<\/strong><\/li>\n\n\n\n<li><code>ack<\/code> \u662f\u63cf\u8ff0<strong>\u81ea\u5df1\u5df2\u6536\u5230\u5bf9\u65b9\u7684\u6570\u636e<\/strong><\/li>\n<\/ul>\n\n\n\n<p>\u4e8c\u8005\u5206\u522b\u5bf9\u5e94\u4e24\u4e2a\u65b9\u5411\u7684\u6570\u636e\u6d41\u3002<\/p>\n\n\n\n<p>TCP \u662f\u5168\u53cc\u5de5\u7684\uff0cA\u2192B \u548c B\u2192A \u7684\u5b57\u8282\u6d41\u7f16\u53f7\u662f\u5404\u81ea\u72ec\u7acb\u7684\u3002<br>\u6240\u4ee5\u4e00\u4e2a\u62a5\u6587\u91cc\u7684 <code>seq<\/code> \u548c <code>ack<\/code>\uff0c\u672c\u8d28\u4e0a\u662f\u5728\u8bf4\u4e24\u4ef6\u4e0d\u540c\u7684\u4e8b\u3002<\/p>\n\n\n\n<p>\u8fd9\u6b63\u662f\u8003\u7814\u9898\u559c\u6b22\u8003\u7684\u70b9\uff1a<br><strong>\u4e0d\u8981\u628a\u67d0\u4e2a\u62a5\u6587\u7684 seq \u548c ack \u5f53\u6210\u4e00\u4e2a\u516c\u5f0f\u4e92\u76f8\u53bb\u63a8\u3002<\/strong><\/p>\n\n\n\n<p>\u771f\u6b63\u80fd\u63a8\u7684\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5bf9\u65b9\u56de\u590d\u7684 <code>ack<\/code> \u5f80\u5f80\u7531\u6211\u8fd9\u4e2a\u62a5\u6587\u7684 <code>seq + \u6709\u6548\u957f\u5ea6<\/code> \u63a8\u51fa\u6765<\/li>\n\n\n\n<li>\u4f46\u540c\u4e00\u4e2a\u62a5\u6587\u5185\u90e8\uff0c<code>seq<\/code> \u548c <code>ack<\/code> \u4e0d\u8981\u6c42\u5b58\u5728\u56fa\u5b9a\u5173\u7cfb<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u7b2c\u4e8c\u9053\u9898\uff1aA \u53d1\u7ed9 B \u7684\u62a5\u6587 seq=200\uff0cack=201\uff0c\u6570\u636e\u90e8\u5206 2B\uff0cB \u7684\u786e\u8ba4\u62a5\u6587\u600e\u4e48\u6c42<\/h2>\n\n\n\n<p>\u9898\u76ee\uff1a<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>A \u548c B \u4e4b\u95f4\u5efa\u7acb\u4e86 TCP \u8fde\u63a5\uff0cA \u5411 B \u53d1\u9001\u4e86\u4e00\u4e2a\u62a5\u6587\u6bb5\uff0c\u5176\u4e2d\u5e8f\u53f7\u5b57\u6bb5 seq=200\uff0c\u786e\u8ba4\u5e8f\u53f7\u5b57\u6bb5 ack=201\uff0c\u6570\u636e\u90e8\u5206\u6709 2B\uff0c\u90a3\u4e48\u5728 B \u5bf9\u8be5\u62a5\u6587\u7684\u786e\u8ba4\u62a5\u6587\u6bb5\u4e2d\u2026\u2026<\/p>\n<\/blockquote>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u7684\u6838\u5fc3\u5c31\u662f\u6c42 B \u56de\u7ed9 A \u7684\u786e\u8ba4\u4fe1\u606f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u5148\u770b A \u53d1\u51fa\u7684\u62a5\u6587<\/h3>\n\n\n\n<p>A \u53d1\u7ed9 B\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq = 200<\/code><\/li>\n\n\n\n<li>\u6570\u636e\u957f\u5ea6 = 2B<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u8bf4\u660e A \u8fd9\u6b21\u53d1\u51fa\u53bb\u7684\u6570\u636e\u5b57\u8282\u5e8f\u53f7\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c\u4e00\u4e2a\u5b57\u8282\uff1a200<\/li>\n\n\n\n<li>\u7b2c\u4e8c\u4e2a\u5b57\u8282\uff1a201<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5 B \u6536\u5230\u540e\uff0c\u4e0b\u4e00\u6b21\u671f\u671b\u6536\u5230 A \u7684\u5b57\u8282\u5e8f\u53f7\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>202<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64 B \u53d1\u56de\u7684\u786e\u8ba4\u62a5\u6587\u6bb5\u4e2d\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u786e\u8ba4\u53f7 ack = 202<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u90a3 B \u7684 seq \u80fd\u4e0d\u80fd\u786e\u5b9a<\/h3>\n\n\n\n<p>\u4e00\u822c<strong>\u4e0d\u80fd\u5355\u72ec\u786e\u5b9a<\/strong>\uff0c\u9664\u975e\u9898\u76ee\u8fd8\u544a\u8bc9\u4e86\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>B \u5f53\u524d\u81ea\u5df1\u7684\u53d1\u9001\u5e8f\u53f7\u662f\u591a\u5c11<\/li>\n\n\n\n<li>\u6216\u8005\u524d\u9762 B \u5df2\u7ecf\u53d1\u8fc7\u591a\u5c11\u6570\u636e<\/li>\n\n\n\n<li>\u6216\u8005\u662f\u5426\u53ea\u662f\u7eaf ACK \u4e14\u521d\u59cb\u72b6\u6001\u5df2\u77e5<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u9898\u901a\u5e38\u80fd\u786e\u5b9a\u7684\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ack = 202<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u800c\u4e0d\u662f\u5b8c\u6574\u552f\u4e00\u786e\u5b9a <code>seq<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48 A \u62a5\u6587\u91cc\u7684 ack=201 \u5bf9\u8fd9\u4e00\u6b65\u6ca1\u5f71\u54cd<\/h3>\n\n\n\n<p>\u56e0\u4e3a A \u62a5\u6587\u4e2d\u7684 <code>ack=201<\/code> \u8868\u793a\u7684\u662f\uff1a<\/p>\n\n\n\n<p>\u201cA \u5df2\u7ecf\u6536\u5230 B \u53d1\u6765\u7684\u5e8f\u53f7\u5230 200 \u4e3a\u6b62\u7684\u5185\u5bb9\uff0c\u671f\u5f85 B \u4e0b\u4e00\u4e2a\u4ece 201 \u5f00\u59cb\u53d1\u3002\u201d<\/p>\n\n\n\n<p>\u8fd9\u53ea\u662f A \u5bf9 B \u7684\u786e\u8ba4\uff0c\u548c B \u5bf9 A \u8fd9\u6b21 2B \u6570\u636e\u7684\u786e\u8ba4\u4e0d\u662f\u540c\u4e00\u4ef6\u4e8b\u3002<\/p>\n\n\n\n<p>\u8fd9\u6b63\u597d\u518d\u6b21\u8bf4\u660e\uff1a<\/p>\n\n\n\n<p><strong>\u4e00\u4e2a\u62a5\u6587\u91cc\u7684 seq\u3001ack \u662f\u4e24\u4e2a\u65b9\u5411\u4e0a\u7684\u4fe1\u606f\u3002<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516d\u3001\u7b2c\u4e09\u7c7b\u9898\uff1a\u5ba2\u6237\u5148\u53d1 FIN\uff0c\u540e\u6765\u6536\u5230\u670d\u52a1\u5668\u53d1\u6765\u7684 FIN\uff0c\u5982\u4f55\u5224\u65ad\u62a5\u6587\u6bb5 B<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u5ba2\u6237\u4e0e\u670d\u52a1\u5668\u5efa\u7acb TCP \u8fde\u63a5\uff0c\u5f53\u8fde\u63a5\u65ad\u5f00\u65f6\uff0c\u5ba2\u6237\u5148\u5411\u670d\u52a1\u5668\u53d1\u9001\u4e00\u4e2a\u6807\u5fd7 FIN=1 \u7684\u62a5\u6587\u6bb5 A\uff0c\u6b64\u62a5\u6587\u6bb5\u4e2d seq \u503c\u4e3a x\uff0cack \u503c\u4e3a y\u3002\u4e00\u6bb5\u65f6\u95f4\u540e\uff0c\u5ba2\u6237\u6536\u5230\u4e86\u670d\u52a1\u5668\u53d1\u6765\u7684\u4e00\u4e2a\u6807\u5fd7 FIN=1 \u7684\u62a5\u6587\u6bb5 B\uff0c\u5219\u5173\u4e8e\u62a5\u6587\u6bb5 B \u7684\u8bf4\u6cd5\u4e2d\uff0c<\/p>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\">\u5148\u770b\u62a5\u6587\u6bb5 A<\/h3>\n\n\n\n<p>\u5ba2\u6237\u5148\u53d1 FIN \u62a5\u6587\u6bb5 A\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>FIN=1<\/code><\/li>\n\n\n\n<li><code>seq = x<\/code><\/li>\n\n\n\n<li><code>ack = y<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u7531\u4e8e FIN \u8981\u5360\u4e00\u4e2a\u5e8f\u5217\u53f7\uff0c\u6240\u4ee5\u670d\u52a1\u5668\u786e\u8ba4\u8fd9\u4e2a FIN \u65f6\uff0c\u5e94\u5f53\u786e\u8ba4\u5230\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>x + 1<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u6b64\uff0c\u670d\u52a1\u5668\u4e4b\u540e\u53d1\u6765\u7684 FIN \u62a5\u6587\u6bb5 B\uff0c\u901a\u5e38\u4f1a\u6ee1\u8db3\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ack = x + 1<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u4e3a\u670d\u52a1\u5668\u5df2\u7ecf\u6536\u5230\u4e86\u5ba2\u6237\u7684 FIN\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u90a3 B \u7684 seq \u662f\u591a\u5c11<\/h3>\n\n\n\n<p>\u8fd9\u4e2a\u4e0d\u80fd\u76f4\u63a5\u5199\u6210\u67d0\u4e2a\u56fa\u5b9a\u503c\uff0c\u53d6\u51b3\u4e8e\u670d\u52a1\u5668\u5728\u8fd9\u4e4b\u524d\u8fd8\u6709\u6ca1\u6709\u6570\u636e\u6ca1\u53d1\u5b8c\u3002<\/p>\n\n\n\n<p>\u5206\u4e24\u79cd\u5e38\u89c1\u60c5\u51b5\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u60c5\u51b5\u4e00\uff1a\u670d\u52a1\u5668\u6ca1\u6709\u989d\u5916\u6570\u636e\u8981\u53d1<\/h4>\n\n\n\n<p>\u90a3\u670d\u52a1\u5668\u53ef\u80fd\u5148\u56de\u4e00\u4e2a ACK\uff0c\u518d\u8fc7\u4e00\u4f1a\u513f\u518d\u53d1 FIN\u3002<br>\u6b64\u65f6\u670d\u52a1\u5668\u53d1 FIN \u7684 <code>seq<\/code> \u5c31\u662f\u5b83\u5f53\u524d\u81ea\u5df1\u7684\u4e0b\u4e00\u4e2a\u53d1\u9001\u5e8f\u53f7\uff0c\u5177\u4f53\u6570\u503c\u53d6\u51b3\u4e8e\u670d\u52a1\u5668\u4e4b\u524d\u53d1\u4e86\u591a\u5c11\u6570\u636e\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u60c5\u51b5\u4e8c\uff1a\u670d\u52a1\u5668\u8fd8\u6709\u6570\u636e\u6ca1\u53d1\u5b8c<\/h4>\n\n\n\n<p>\u670d\u52a1\u5668\u53ef\u80fd\u5148\u7ee7\u7eed\u628a\u5269\u4f59\u6570\u636e\u53d1\u5b8c\uff0c\u6700\u540e\u518d\u53d1 FIN\u3002<br>\u90a3\u4e48\u8fd9\u4e2a FIN \u7684 <code>seq<\/code> \u5c31\u4f1a\u66f4\u5927\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u901a\u5e38\u80fd\u786e\u5b9a\u7684\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u62a5\u6587\u6bb5 B \u7684 <code>ack = x + 1<\/code><\/strong><\/li>\n\n\n\n<li><strong>\u62a5\u6587\u6bb5 B \u7684 <code>seq<\/code> \u4e0d\u80fd\u4ec5\u51ed\u9898\u5e72\u552f\u4e00\u786e\u5b9a<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u8fd9\u7c7b\u9898\u6700\u5bb9\u6613\u9519\u5728\u54ea\u91cc<\/h3>\n\n\n\n<p>\u6700\u5e38\u89c1\u7684\u9519\u6cd5\u662f\u628a\u670d\u52a1\u5668\u53d1\u6765\u7684 FIN \u7684 <code>seq<\/code> \u4e5f\u5199\u6210 <code>x+1<\/code>\u3002<br>\u8fd9\u662f\u9519\u8bef\u7684\uff0c\u56e0\u4e3a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>x+1<\/code> \u662f\u670d\u52a1\u5668\u5bf9\u5ba2\u6237 FIN \u7684\u786e\u8ba4\u53f7<\/li>\n\n\n\n<li>\u670d\u52a1\u5668\u81ea\u5df1\u7684 <code>seq<\/code> \u8d70\u7684\u662f\u53e6\u4e00\u5957\u7f16\u53f7<\/li>\n<\/ul>\n\n\n\n<p>\u53c8\u56de\u5230\u4e86\u90a3\u53e5\u6838\u5fc3\u8bdd\uff1a<\/p>\n\n\n\n<p><strong>seq \u770b\u81ea\u5df1\uff0cack \u770b\u5bf9\u65b9\u3002<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e03\u3001FIN \u5230\u5e95\u8868\u793a\u4ec0\u4e48\uff1a\u662f\u4e0d\u662f\u201c\u4e00\u53d1 FIN \u5c31\u6574\u4e2a\u8fde\u63a5\u65ad\u4e86\u201d<\/h2>\n\n\n\n<p>\u4f60\u6700\u540e\u90a3\u9053\u9009\u62e9\u9898\u672c\u8d28\u662f\u5728\u8003 FIN \u7684\u8bed\u4e49\u3002<\/p>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>TCP \u7684\u901a\u4fe1\u53cc\u65b9\uff0c\u6709\u4e00\u65b9\u53d1\u9001\u4e86\u5e26\u6709 FIN \u6807\u5fd7\u7684\u6570\u636e\u6bb5\u540e\uff0c\u8868\u793a<br>A. \u5c06\u65ad\u5f00\u901a\u4fe1\u53cc\u65b9\u7684 TCP \u8fde\u63a5<br>B. \u5355\u65b9\u9762\u91ca\u653e\u8fde\u63a5\uff0c\u8868\u793a\u672c\u65b9\u5df2\u7ecf\u65e0\u6570\u636e\u53d1\u9001\uff0c\u4f46\u53ef\u4ee5\u63a5\u6536\u5bf9\u65b9\u7684\u6570\u636e<br>C. \u4e2d\u6b62\u6570\u636e\u53d1\u9001\uff0c\u53cc\u65b9\u90fd\u4e0d\u80fd\u53d1\u9001\u6570\u636e<br>D. \u8fde\u63a5\u88ab\u91cd\u65b0\u5efa\u7acb<\/p>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\">\u6b63\u786e\u7b54\u6848<\/h3>\n\n\n\n<p><strong>B<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u662f B<\/h3>\n\n\n\n<p>\u53d1\u9001 <code>FIN=1<\/code> \u7684\u542b\u4e49\u662f\uff1a<\/p>\n\n\n\n<p>\u201c\u6211\u8fd9\u4e00\u8fb9\u5df2\u7ecf\u6ca1\u6709\u6570\u636e\u8981\u53d1\u4e86\uff0c\u6211\u7684\u53d1\u9001\u65b9\u5411\u8981\u5173\u95ed\u4e86\u3002\u201d<\/p>\n\n\n\n<p>\u4f46 TCP \u662f\u5168\u53cc\u5de5\u7684\uff0c\u8fde\u63a5\u6709\u4e24\u4e2a\u65b9\u5411\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A \u2192 B<\/li>\n\n\n\n<li>B \u2192 A<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u4e00\u65b9\u53d1 FIN\uff0c\u53ea\u662f\u8868\u793a<strong>\u672c\u65b9\u53d1\u9001\u65b9\u5411\u5173\u95ed<\/strong>\uff0c\u5e76\u4e0d\u4ee3\u8868\u53e6\u4e00\u65b9\u4e5f\u7acb\u523b\u4e0d\u80fd\u53d1\u4e86\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u53d1 FIN \u7684\u8fd9\u4e00\u65b9\uff1a\u4ee5\u540e\u4e0d\u80fd\u518d\u53d1\u9001\u6570\u636e<\/li>\n\n\n\n<li>\u4f46\u5b83\u4ecd\u7136\u53ef\u4ee5\u7ee7\u7eed\u63a5\u6536\u5bf9\u65b9\u53d1\u9001\u7684\u6570\u636e<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u5c31\u53eb\u505a<strong>\u534a\u5173\u95ed<\/strong>\u6216<strong>\u5355\u65b9\u5411\u5173\u95ed<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u4e0d\u662f A<\/h3>\n\n\n\n<p>A \u8bf4\u201c\u5c06\u65ad\u5f00\u901a\u4fe1\u53cc\u65b9\u7684 TCP \u8fde\u63a5\u201d\uff0c\u8fd9\u4e2a\u8bf4\u6cd5\u592a\u7edd\u5bf9\u4e86\u3002<br>\u53d1\u51fa\u4e00\u4e2a FIN \u4ee5\u540e\uff0c\u8fde\u63a5\u8fd8\u6ca1\u6709\u5b8c\u5168\u65ad\u5f00\uff0c\u56e0\u4e3a\u5bf9\u65b9\u53ef\u80fd\u8fd8\u6709\u6570\u636e\u7ee7\u7eed\u53d1\u3002<\/p>\n\n\n\n<p>\u771f\u6b63\u5b8c\u5168\u65ad\u5f00\uff0c\u8981\u7b49\u53cc\u65b9\u90fd\u5b8c\u6210\u5404\u81ea\u65b9\u5411\u7684\u5173\u95ed\uff0c\u4e5f\u5c31\u662f\u901a\u5e38\u7684\u56db\u6b21\u6325\u624b\u8d70\u5b8c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u4e0d\u662f C<\/h3>\n\n\n\n<p>C \u8bf4\u201c\u53cc\u65b9\u90fd\u4e0d\u80fd\u53d1\u9001\u6570\u636e\u201d\uff0c\u8fd9\u660e\u663e\u4e0d\u5bf9\u3002<br>\u4e00\u65b9\u53d1 FIN \u540e\uff0c\u5bf9\u65b9\u4ecd\u7136\u53ef\u4ee5\u7ee7\u7eed\u53d1\u6570\u636e\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u4e0d\u662f D<\/h3>\n\n\n\n<p>D \u66f4\u660e\u663e\u4e0d\u5bf9\uff0cFIN \u662f\u91ca\u653e\u8fde\u63a5\uff0c\u4e0d\u662f\u91cd\u5efa\u8fde\u63a5\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516b\u3001\u628a\u8fd9\u51e0\u4e2a\u77e5\u8bc6\u70b9\u8fde\u6210\u4e00\u4e2a\u505a\u9898\u6846\u67b6<\/h2>\n\n\n\n<p>\u505a TCP \u9996\u90e8\u5b57\u6bb5\u3001\u63e1\u624b\u6325\u624b\u3001seq\/ack \u9898\u65f6\uff0c\u6211\u73b0\u5728\u66f4\u5efa\u8bae\u6309\u4e0b\u9762\u8fd9\u4e2a\u6846\u67b6\u6765\u5224\u65ad\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e00\u6b65\uff1a\u5148\u5206\u6e05\u201c\u8c01\u7ed9\u8c01\u53d1\u201d<\/h3>\n\n\n\n<p>TCP \u662f\u53cc\u5411\u7684\uff0cA\u2192B \u548c B\u2192A \u4e00\u5b9a\u5206\u5f00\u770b\u3002<br>\u53ea\u8981\u9898\u76ee\u4e00\u4e71\uff0c\u5148\u5728\u8349\u7a3f\u7eb8\u4e0a\u6807\u4e24\u4e2a\u65b9\u5411\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e8c\u6b65\uff1a\u770b seq \u662f\u8c01\u81ea\u5df1\u7684\u7f16\u53f7<\/h3>\n\n\n\n<p><code>seq<\/code> \u6c38\u8fdc\u770b\u201c\u672c\u62a5\u6587\u53d1\u9001\u65b9\u201d\u7684\u53d1\u9001\u5b57\u8282\u6d41\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A \u53d1\u7684\u62a5\u6587\uff0c<code>seq<\/code> \u770b A \u81ea\u5df1\u53d1\u5230\u54ea\u513f\u4e86<\/li>\n\n\n\n<li>B \u53d1\u7684\u62a5\u6587\uff0c<code>seq<\/code> \u770b B \u81ea\u5df1\u53d1\u5230\u54ea\u513f\u4e86<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e09\u6b65\uff1a\u770b ack \u662f\u5bf9\u8c01\u7684\u786e\u8ba4<\/h3>\n\n\n\n<p><code>ack<\/code> \u6c38\u8fdc\u770b\u201c\u672c\u62a5\u6587\u53d1\u9001\u65b9\u5df2\u7ecf\u6536\u5230\u4e86\u5bf9\u65b9\u591a\u5c11\u201d\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A \u53d1\u7684\u62a5\u6587\uff0c<code>ack<\/code> \u662f A \u5bf9 B \u7684\u786e\u8ba4<\/li>\n\n\n\n<li>B \u53d1\u7684\u62a5\u6587\uff0c<code>ack<\/code> \u662f B \u5bf9 A \u7684\u786e\u8ba4<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u56db\u6b65\uff1a\u5224\u65ad\u8fd9\u6b21\u62a5\u6587\u4f1a\u4e0d\u4f1a\u8ba9\u5e8f\u53f7\u52a0\u957f\u5ea6<\/h3>\n\n\n\n<p>\u5e8f\u53f7\u524d\u8fdb\u91cf =<\/p>\n\n\n\n<p><code>\u6570\u636e\u5b57\u8282\u6570 + SYN\u662f\u5426\u4e3a1 + FIN\u662f\u5426\u4e3a1<\/code><\/p>\n\n\n\n<p>\u5176\u4e2d\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7eaf ACK\uff1a\u52a0 0<\/li>\n\n\n\n<li>SYN\uff1a\u52a0 1<\/li>\n\n\n\n<li>FIN\uff1a\u52a0 1<\/li>\n\n\n\n<li>\u5e26 n \u5b57\u8282\u6570\u636e\uff1a\u52a0 n<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e94\u6b65\uff1a\u786e\u8ba4\u53f7\u600e\u4e48\u63a8<\/h3>\n\n\n\n<p><code>ack = \u5bf9\u65b9\u4e0b\u4e00\u4e2a\u5e94\u8be5\u53d1\u9001\u7684\u5e8f\u53f7<\/code><\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>ack = \u5bf9\u65b9\u672c\u6b21\u62a5\u6587\u7684 seq + \u5bf9\u65b9\u672c\u6b21\u62a5\u6587\u5360\u7528\u7684\u5e8f\u53f7\u957f\u5ea6<\/code><\/p>\n\n\n\n<p>\u8fd9\u91cc\u201c\u5360\u7528\u7684\u5e8f\u53f7\u957f\u5ea6\u201d again \u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>\u6570\u636e\u957f\u5ea6 + SYN\u662f\u5426\u4e3a1 + FIN\u662f\u5426\u4e3a1<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e5d\u3001\u8fd9\u51e0\u7c7b\u9898\u4e3a\u4ec0\u4e48\u603b\u5bb9\u6613\u9519<\/h2>\n\n\n\n<p>TCP \u8fd9\u4e00\u7ae0\u6700\u5bb9\u6613\u9519\uff0c\u4e0d\u662f\u56e0\u4e3a\u516c\u5f0f\u96be\uff0c\u800c\u662f\u56e0\u4e3a\u4fe1\u606f\u662f\u201c\u4ea4\u53c9\u7684\u201d\u3002<\/p>\n\n\n\n<p>\u540c\u4e00\u4e2a\u62a5\u6587\u6bb5\u91cc\u540c\u65f6\u51fa\u73b0\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u672c\u65b9\u7684 <code>seq<\/code><\/li>\n\n\n\n<li>\u672c\u65b9\u5bf9\u5bf9\u65b9\u7684 <code>ack<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u4e8e\u662f\u8111\u5b50\u5f88\u5bb9\u6613\u628a\u4e24\u4e2a\u65b9\u5411\u6df7\u5728\u4e00\u8d77\u3002<\/p>\n\n\n\n<p>\u518d\u52a0\u4e0a <code>SYN<\/code>\u3001<code>FIN<\/code> \u8fd9\u4e24\u4e2a\u201c\u4e0d\u5e26\u6570\u636e\u5374\u5360\u5e8f\u53f7\u201d\u7684\u7279\u4f8b\uff0c\u5f88\u591a\u4eba\u5c31\u4f1a\u5728\u8ba1\u7b97\u65f6\u5c11\u52a0 1 \u6216\u591a\u52a0 1\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u505a\u9898\u65f6\u4e00\u5b9a\u8981\u5f3a\u884c\u517b\u6210\u4e24\u4e2a\u4e60\u60ef\uff1a<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c<strong>\u5206\u65b9\u5411<\/strong>\u3002<br>\u6c38\u8fdc\u628a A\u2192B \u548c B\u2192A \u5206\u5f00\u8bb0\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e8c\uff0c<strong>\u5148\u7b97\u5360\u7528\u957f\u5ea6<\/strong>\u3002<br>\u6bcf\u9047\u5230\u4e00\u4e2a\u62a5\u6587\uff0c\u5148\u5224\u65ad\u5b83\u5360\u51e0\u4e2a\u5e8f\u53f7\uff1a<\/p>\n\n\n\n<p><code>\u957f\u5ea6 = \u6570\u636e\u5b57\u8282\u6570 + SYN?1:0 + FIN?1:0<\/code><\/p>\n\n\n\n<p>\u53ea\u8981\u8fd9\u4e00\u6b65\u4e0d\u4e71\uff0c\u540e\u9762\u7684 <code>seq<\/code>\u3001<code>ack<\/code> \u57fa\u672c\u90fd\u80fd\u7a33\u4f4f\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">TCP \u91cc\u7684 RTT \u5230\u5e95\u662f\u4ec0\u4e48\uff0c\u505a\u9898\u65f6\u600e\u4e48\u7528<\/h2>\n\n\n\n<p>\u5728 408 \u98ce\u683c\u7684\u4f20\u8f93\u5c42\u9898\u76ee\u91cc\uff0cRTT \u4e00\u822c\u6307<strong>\u5f80\u8fd4\u65f6\u95f4<\/strong>\uff0c\u4e5f\u5c31\u662f\u4e00\u4e2a\u62a5\u6587\u4ece\u53d1\u9001\u7aef\u5230\u63a5\u6536\u7aef\uff0c\u518d\u4ece\u63a5\u6536\u7aef\u8fd4\u56de\u53d1\u9001\u7aef\u6240\u7ecf\u5386\u7684\u603b\u65f6\u95f4\u3002\u4e8e\u662f\u6709\u4e00\u4e2a\u6700\u5e38\u7528\u7684\u6362\u7b97\uff1a<\/p>\n\n\n\n<p><code>\u5355\u7a0b\u4f20\u64ad\u65f6\u5ef6 = RTT \/ 2<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u51e1\u662f\u6d89\u53ca\u201c\u4e09\u6b21\u63e1\u624b\u3001\u56db\u6b21\u6325\u624b\u3001\u786e\u8ba4\u5230\u8fbe\u3001\u6700\u77ed\u91ca\u653e\u65f6\u95f4\u201d\u8fd9\u7c7b\u9898\uff0c\u7b2c\u4e00\u6b65\u901a\u5e38\u5c31\u662f\u628a RTT \u5148\u62c6\u6210\u4e24\u4e2a <code>RTT\/2<\/code> \u6765\u770b\u3002<\/p>\n\n\n\n<p>\u53e6\u5916\uff0cTCP \u9898\u91cc\u6700\u5e38\u914d\u5957\u8003\u8fd9\u51e0\u6761\u89c4\u5219\uff1a<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c<code>seq<\/code> \u8868\u793a<strong>\u672c\u62a5\u6587\u6bb5\u6570\u636e\u90e8\u5206\u7b2c\u4e00\u4e2a\u5b57\u8282\u7684\u5e8f\u53f7<\/strong>\u3002<br>\u7b2c\u4e8c\uff0c<code>ack<\/code> \u8868\u793a<strong>\u671f\u671b\u6536\u5230\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7<\/strong>\u3002<br>\u7b2c\u4e09\uff0cTCP \u7684\u786e\u8ba4\u901a\u5e38\u662f<strong>\u7d2f\u8ba1\u786e\u8ba4<\/strong>\uff0c\u4e2d\u95f4\u7f3a\u4e86\u4e00\u6bb5\uff0c\u5373\u4f7f\u540e\u9762\u7684\u6bb5\u5230\u4e86\uff0c\u4e5f\u4e0d\u80fd\u8d8a\u8fc7\u53bb\u786e\u8ba4\u3002<br>\u7b2c\u56db\uff0c\u53d1\u751f<strong>\u8d85\u65f6<\/strong>\u65f6\uff0c\u6309\u7167\u8003\u7814\u5e38\u89c1\u6a21\u578b\u5904\u7406\u4e3a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = \u5f53\u524dcwnd \/ 2<\/code><\/li>\n\n\n\n<li><code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u7136\u540e\u91cd\u65b0\u8fdb\u5165\u6162\u5f00\u59cb\uff0c\u8fbe\u5230\u95e8\u9650\u540e\u8f6c\u5165\u62e5\u585e\u907f\u514d<\/li>\n<\/ul>\n\n\n\n<p>\u7b2c\u4e94\uff0c\u53d1\u9001\u7a97\u53e3\u5927\u5c0f\u4e0d\u662f\u53ea\u770b\u62e5\u585e\u7a97\u53e3\uff0c\u8fd8\u8981\u770b\u63a5\u6536\u7a97\u53e3\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u4e0b\u9762\u6309\u9898\u76ee\u9010\u4e2a\u62c6\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c1\u9898\uff1a\u5ba2\u6237\u4e3b\u52a8\u65ad\u5f00\u540e\uff0c\u670d\u52a1\u5668\u6700\u77ed\u591a\u4e45\u91ca\u653e\u8fde\u63a5<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\u662f\uff1a<\/p>\n\n\n\n<p>\u5047\u8bbe TCP \u5ba2\u6237\u4e0e TCP \u670d\u52a1\u5668\u7684\u901a\u4fe1\u5df2\u7ed3\u675f\uff0c\u7aef\u5230\u7aef\u5f80\u8fd4\u65f6\u95f4\u4e3a RTT\u3002<br><code>t<\/code> \u65f6\u523b TCP \u5ba2\u6237\u8bf7\u6c42\u65ad\u5f00\u8fde\u63a5\uff0c\u5219\u4ece <code>t<\/code> \u65f6\u523b\u8d77\uff0cTCP \u670d\u52a1\u5668\u91ca\u653e\u8be5\u8fde\u63a5\u7684\u6700\u77ed\u65f6\u95f4\u662f\u591a\u5c11\uff1f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u4ece <code>t<\/code> \u65f6\u523b\u8d77\uff0c<strong>TCP \u670d\u52a1\u5668\u6700\u77ed\u5728 <code>1.5RTT<\/code> \u540e\u91ca\u653e\u8fde\u63a5<\/strong>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u8fd9\u662f\u6807\u51c6\u7684\u56db\u6b21\u6325\u624b\u9898\uff0c\u800c\u4e14\u95ee\u7684\u662f\u201c<strong>\u670d\u52a1\u5668\u91ca\u653e\u8fde\u63a5\u7684\u6700\u77ed\u65f6\u95f4<\/strong>\u201d\u3002<\/p>\n\n\n\n<p>\u5728\u6700\u77ed\u60c5\u51b5\u4e0b\uff0c\u53ef\u4ee5\u8ba4\u4e3a\u670d\u52a1\u5668\u4e00\u6536\u5230\u5ba2\u6237\u7aef\u7684 FIN\uff0c\u5c31\u7acb\u523b\u56de\u590d ACK\uff0c\u5e76\u4e14\u81ea\u5df1\u4e5f\u7acb\u5373\u53d1\u9001 FIN\u3002<\/p>\n\n\n\n<p>\u65f6\u95f4\u7ebf\u5982\u4e0b\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e00\u6b65\uff1a\u5ba2\u6237\u7aef\u53d1\u9001 FIN<\/h4>\n\n\n\n<p>\u5ba2\u6237\u7aef\u5728 <code>t<\/code> \u65f6\u523b\u53d1\u9001 FIN\u3002<br>\u8be5\u62a5\u6587\u5230\u8fbe\u670d\u52a1\u5668\uff0c\u9700\u8981 <code>RTT\/2<\/code>\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u670d\u52a1\u5668\u5728\uff1a<\/p>\n\n\n\n<p><code>t + RTT\/2<\/code><\/p>\n\n\n\n<p>\u6536\u5230\u5ba2\u6237\u7aef\u7684\u65ad\u5f00\u8bf7\u6c42\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e8c\u6b65\uff1a\u670d\u52a1\u5668\u7acb\u523b\u56de ACK\uff0c\u5e76\u540c\u65f6\u53d1\u81ea\u5df1\u7684 FIN<\/h4>\n\n\n\n<p>\u82e5\u6309\u6700\u77ed\u60c5\u51b5\u5904\u7406\uff0c\u670d\u52a1\u5668\u5728\u6536\u5230 FIN \u7684\u77ac\u95f4\u5c31\u53ef\u4ee5\u53d1\u51fa ACK\uff0c\u5e76\u4e14\u53d1\u51fa\u81ea\u5df1\u7684 FIN\u3002<\/p>\n\n\n\n<p>\u5ba2\u6237\u7aef\u6536\u5230\u670d\u52a1\u5668\u53d1\u6765\u7684 FIN\uff0c\u4e5f\u9700\u8981 <code>RTT\/2<\/code>\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u5ba2\u6237\u7aef\u5728\uff1a<\/p>\n\n\n\n<p><code>t + RTT<\/code><\/p>\n\n\n\n<p>\u6536\u5230\u670d\u52a1\u5668\u7684 FIN\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e09\u6b65\uff1a\u5ba2\u6237\u7aef\u5bf9\u670d\u52a1\u5668\u7684 FIN \u8fdb\u884c\u786e\u8ba4<\/h4>\n\n\n\n<p>\u5ba2\u6237\u7aef\u6536\u5230\u670d\u52a1\u5668 FIN \u540e\uff0c\u7acb\u523b\u53d1\u6700\u540e\u4e00\u4e2a ACK\u3002<br>\u8fd9\u4e2a ACK \u518d\u7ecf\u8fc7 <code>RTT\/2<\/code> \u5230\u8fbe\u670d\u52a1\u5668\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u670d\u52a1\u5668\u5728\uff1a<\/p>\n\n\n\n<p><code>t + 1.5RTT<\/code><\/p>\n\n\n\n<p>\u6536\u5230\u6700\u7ec8\u786e\u8ba4\uff0c\u6b63\u5f0f\u91ca\u653e\u8fde\u63a5\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u4e0d\u662f RTT \u6216 2RTT<\/h3>\n\n\n\n<p>\u5f88\u591a\u4eba\u4f1a\u628a\u201c\u5ba2\u6237\u7aef\u8fdb\u5165 TIME_WAIT \u7b49 2MSL\u201d\u6df7\u8fdb\u6765\u3002\u9898\u76ee\u95ee\u7684\u662f<strong>\u670d\u52a1\u5668\u91ca\u653e\u8fde\u63a5\u7684\u6700\u77ed\u65f6\u95f4<\/strong>\uff0c\u4e0d\u662f\u5ba2\u6237\u7aef\u5f7b\u5e95\u7ed3\u675f TIME_WAIT \u7684\u65f6\u95f4\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u770b\u7684\u662f\u670d\u52a1\u5668\u8fdb\u5165 CLOSED \u7684\u65f6\u523b\uff0c\u5373\u6536\u5230\u6700\u540e ACK \u7684\u65f6\u523b\uff0c\u4e5f\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>1.5RTT<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c2\u9898\uff1a\u53ea\u6536\u5230\u7b2c1\u4e2a\u548c\u7b2c3\u4e2a\u6bb5\u65f6\uff0c\u786e\u8ba4\u53f7\u662f\u591a\u5c11<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\u662f\uff1a<\/p>\n\n\n\n<p>\u7532\u5411\u4e59\u53d1\u9001\u4e86 3 \u4e2a\u8fde\u7eed\u7684 TCP \u6bb5\uff0c\u5206\u522b\u5305\u542b <code>200B\u3001300B\u3001400B<\/code> \u7684\u6709\u6548\u8f7d\u8377\uff0c\u7b2c 3 \u4e2a\u6bb5\u7684\u5e8f\u53f7\u4e3a <code>1000<\/code>\u3002<br>\u82e5\u4e59\u4ec5\u6b63\u786e\u63a5\u6536\u5230\u7b2c 1 \u4e2a\u548c\u7b2c 3 \u4e2a\u6bb5\uff0c\u5219\u4e59\u53d1\u9001\u7ed9\u7532\u7684\u786e\u8ba4\u5e8f\u53f7\u662f\u591a\u5c11\uff1f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u786e\u8ba4\u5e8f\u53f7\u662f\uff1a<\/p>\n\n\n\n<p><code>700<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u5df2\u77e5\u7b2c 3 \u4e2a\u6bb5\u7684 <code>seq = 1000<\/code>\uff0c\u5b83\u524d\u9762\u8fd8\u6709\u7b2c 2 \u4e2a\u6bb5\uff0c\u957f\u5ea6\u4e3a <code>300B<\/code>\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u7b2c 2 \u4e2a\u6bb5\u7684\u8d77\u59cb\u5e8f\u53f7\u5e94\u4e3a\uff1a<\/p>\n\n\n\n<p><code>1000 - 300 = 700<\/code><\/p>\n\n\n\n<p>\u7b2c 1 \u4e2a\u6bb5\u957f\u5ea6\u4e3a <code>200B<\/code>\uff0c\u6240\u4ee5\u7b2c 1 \u4e2a\u6bb5\u8d77\u59cb\u5e8f\u53f7\u4e3a\uff1a<\/p>\n\n\n\n<p><code>700 - 200 = 500<\/code><\/p>\n\n\n\n<p>\u4e8e\u662f\u4e09\u4e2a\u6bb5\u5206\u522b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u6bb5\uff1a<code>seq = 500<\/code>\uff0c\u957f\u5ea6 <code>200B<\/code><\/li>\n\n\n\n<li>\u7b2c 2 \u6bb5\uff1a<code>seq = 700<\/code>\uff0c\u957f\u5ea6 <code>300B<\/code><\/li>\n\n\n\n<li>\u7b2c 3 \u6bb5\uff1a<code>seq = 1000<\/code>\uff0c\u957f\u5ea6 <code>400B<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u73b0\u5728\u4e59\u53ea\u6536\u5230\u4e86\u7b2c 1 \u4e2a\u548c\u7b2c 3 \u4e2a\uff0c\u4f46<strong>\u7b2c 2 \u4e2a\u6bb5\u4e22\u4e86<\/strong>\u3002<\/p>\n\n\n\n<p>TCP \u91c7\u7528<strong>\u7d2f\u8ba1\u786e\u8ba4<\/strong>\uff0c\u786e\u8ba4\u53f7\u6c38\u8fdc\u6307\u5411\u201c\u5f53\u524d\u6309\u5e8f\u6536\u5230\u7684\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u4e4b\u540e\u7684\u90a3\u4e2a\u5b57\u8282\u201d\u3002<\/p>\n\n\n\n<p>\u4e59\u867d\u7136\u6536\u5230\u4e86\u7b2c 3 \u6bb5\uff0c\u4f46\u56e0\u4e3a\u7b2c 2 \u6bb5\u6ca1\u5230\uff0c\u6570\u636e\u4e0d\u8fde\u7eed\uff0c\u6240\u4ee5\u53ea\u80fd\u786e\u8ba4\u5230\u7b2c 1 \u6bb5\u672b\u5c3e\u4e4b\u540e\u3002<\/p>\n\n\n\n<p>\u7b2c 1 \u6bb5\u8986\u76d6\u7684\u5b57\u8282\u8303\u56f4\u662f\uff1a<\/p>\n\n\n\n<p><code>500 ~ 699<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64\u4e0b\u4e00\u4e2a\u671f\u671b\u6536\u5230\u7684\u5b57\u8282\u5e8f\u53f7\u662f\uff1a<\/p>\n\n\n\n<p><code>700<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u786e\u8ba4\u53f7\u4e3a\uff1a<\/p>\n\n\n\n<p><code>ack = 700<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u8fd9\u7c7b\u9898\u7684\u6838\u5fc3\u9677\u9631<\/h3>\n\n\n\n<p>\u6700\u5bb9\u6613\u9519\u5728\u4e00\u53e5\u8bdd\uff1a<strong>\u540e\u9762\u7684\u6bb5\u5230\u4e86\uff0c\u4e0d\u4ee3\u8868\u786e\u8ba4\u53f7\u5c31\u80fd\u5f80\u540e\u8df3<\/strong>\u3002<\/p>\n\n\n\n<p>TCP \u7684\u786e\u8ba4\u4e0d\u662f\u201c\u6211\u770b\u89c1\u8c01\u5c31\u786e\u8ba4\u8c01\u201d\uff0c\u800c\u662f\u201c\u6211\u6309\u5e8f\u8fde\u7eed\u6536\u5230\u4e86\u54ea\u91cc\u201d\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c3\u9898\uff1acwnd=34KB \u65f6\u8d85\u65f6\uff0c4RTT \u540e\u7a97\u53e3\u591a\u5927<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\u662f\uff1a<\/p>\n\n\n\n<p>MSS \u4e3a <code>1KB<\/code>\uff0c\u5f53\u62e5\u585e\u7a97\u53e3\u4e3a <code>34KB<\/code> \u65f6\u53d1\u751f\u4e86\u8d85\u65f6\u4e8b\u4ef6\u3002<br>\u82e5\u5728\u63a5\u4e0b\u6765\u7684 <code>4RTT<\/code> \u5185\u62a5\u6587\u6bb5\u4f20\u8f93\u90fd\u6210\u529f\uff0c\u5219\u5f53\u8fd9\u4e9b\u62a5\u6587\u6bb5\u5747\u5f97\u5230\u786e\u8ba4\u540e\uff0c\u62e5\u585e\u7a97\u53e3\u5927\u5c0f\u662f\u591a\u5c11\uff1f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u62e5\u585e\u7a97\u53e3\u5927\u5c0f\u4e3a\uff1a<\/p>\n\n\n\n<p><code>16KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u5148\u5904\u7406\u8d85\u65f6\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u539f\u6765 <code>cwnd = 34KB<\/code><\/li>\n\n\n\n<li>\u8d85\u65f6\u540e\uff0c<code>ssthresh = 34 \/ 2 = 17KB<\/code><\/li>\n\n\n\n<li><code>cwnd = 1KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u63a5\u4e0b\u6765 4 \u4e2a RTT \u5185\u90fd\u6210\u529f\uff0c\u6240\u4ee5\u5148\u8d70\u6162\u5f00\u59cb\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c1\u4e2a RTT \u540e<\/h4>\n\n\n\n<p><code>cwnd: 1 \u2192 2<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c2\u4e2a RTT \u540e<\/h4>\n\n\n\n<p><code>cwnd: 2 \u2192 4<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c3\u4e2a RTT \u540e<\/h4>\n\n\n\n<p><code>cwnd: 4 \u2192 8<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c4\u4e2a RTT \u540e<\/h4>\n\n\n\n<p><code>cwnd: 8 \u2192 16<\/code><\/p>\n\n\n\n<p>\u6b64\u65f6\u8fd8\u6ca1\u6709\u8fbe\u5230\u95e8\u9650 <code>17KB<\/code>\uff0c\u56e0\u6b64\u4ecd\u5904\u4e8e\u6162\u5f00\u59cb\u9636\u6bb5\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5 4RTT \u7ed3\u675f\u540e\uff1a<\/p>\n\n\n\n<p><code>cwnd = 16KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u4e0d\u662f 17KB \u6216\u66f4\u5927<\/h3>\n\n\n\n<p>\u56e0\u4e3a\u6162\u5f00\u59cb\u662f\u6309 RTT \u8fd1\u4f3c\u770b\u4f5c\u201c\u7ffb\u500d\u201d\uff0c4 \u4e2a RTT \u540e\u6b63\u597d\u662f\uff1a<\/p>\n\n\n\n<p><code>1, 2, 4, 8, 16<\/code><\/p>\n\n\n\n<p>\u8fd8\u6ca1\u5230 <code>17<\/code>\uff0c\u6240\u4ee5\u4e0d\u4f1a\u5207\u5230\u62e5\u585e\u907f\u514d\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c4\u9898\uff1a\u8d85\u65f6\u540e\u7ecf\u8fc7 10RTT\uff0c\u53d1\u9001\u7a97\u53e3\u591a\u5927<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\u662f\uff1a<\/p>\n\n\n\n<p>\u7532\u5411\u4e59\u53d1\u8d77 TCP \u8fde\u63a5\uff0cMSS \u4e3a <code>1KB<\/code>\uff0c\u4e59\u6bcf\u6536\u5230\u4e00\u4e2a\u6570\u636e\u6bb5\u90fd\u4f1a\u53d1\u51fa\u4e00\u4e2a\u63a5\u6536\u7a97\u53e3\u4e3a <code>10KB<\/code> \u7684\u786e\u8ba4\u6bb5\u3002<br>\u82e5\u7532\u5728 <code>t<\/code> \u65f6\u523b\u53d1\u751f\u8d85\u65f6\uff0c\u6b64\u65f6\u62e5\u585e\u7a97\u53e3\u4e3a <code>16KB<\/code>\u3002<br>\u5219\u4ece <code>t<\/code> \u65f6\u523b\u8d77\uff0c\u5728\u4e0d\u518d\u53d1\u751f\u8d85\u65f6\u7684\u60c5\u51b5\u4e0b\uff0c\u7ecf\u8fc7 <code>10RTT<\/code> \u540e\uff0c\u7532\u7684\u53d1\u9001\u7a97\u53e3\u5927\u5c0f\u662f\u591a\u5c11\uff1f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u53d1\u9001\u7a97\u53e3\u5927\u5c0f\u4e3a\uff1a<\/p>\n\n\n\n<p><code>10KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u8fd9\u9898\u4e0d\u80fd\u53ea\u7b97 <code>cwnd<\/code>\uff0c\u6700\u540e\u8981\u53d6\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e00\u6b65\uff1a\u8d85\u65f6\u540e\u7684\u53c2\u6570\u53d8\u5316<\/h4>\n\n\n\n<p>\u8d85\u65f6\u524d <code>cwnd = 16KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = 16 \/ 2 = 8KB<\/code><\/li>\n\n\n\n<li><code>cwnd = 1KB<\/code><\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e8c\u6b65\uff1a10RTT \u5185\u7a97\u53e3\u589e\u957f<\/h4>\n\n\n\n<p>\u5148\u6162\u5f00\u59cb\uff0c\u5230 8KB \u4e3a\u6b62\uff1b\u4e4b\u540e\u62e5\u585e\u907f\u514d\uff0c\u6bcf RTT \u52a0 1KB\u3002<\/p>\n\n\n\n<p>\u7a97\u53e3\u53d8\u5316\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c1RTT \u540e\uff1a<code>1 \u2192 2<\/code><\/li>\n\n\n\n<li>\u7b2c2RTT \u540e\uff1a<code>2 \u2192 4<\/code><\/li>\n\n\n\n<li>\u7b2c3RTT \u540e\uff1a<code>4 \u2192 8<\/code><\/li>\n\n\n\n<li>\u7b2c4RTT \u540e\uff1a<code>8 \u2192 9<\/code><\/li>\n\n\n\n<li>\u7b2c5RTT \u540e\uff1a<code>9 \u2192 10<\/code><\/li>\n\n\n\n<li>\u7b2c6RTT \u540e\uff1a<code>10 \u2192 11<\/code><\/li>\n\n\n\n<li>\u7b2c7RTT \u540e\uff1a<code>11 \u2192 12<\/code><\/li>\n\n\n\n<li>\u7b2c8RTT \u540e\uff1a<code>12 \u2192 13<\/code><\/li>\n\n\n\n<li>\u7b2c9RTT \u540e\uff1a<code>13 \u2192 14<\/code><\/li>\n\n\n\n<li>\u7b2c10RTT \u540e\uff1a<code>14 \u2192 15<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5 10RTT \u540e\uff1a<\/p>\n\n\n\n<p><code>cwnd = 15KB<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e09\u6b65\uff1a\u7ed3\u5408\u63a5\u6536\u7a97\u53e3 rwnd<\/h4>\n\n\n\n<p>\u9898\u76ee\u7ed9\u51fa\u4e59\u7684\u63a5\u6536\u7a97\u53e3\u59cb\u7ec8\u662f\uff1a<\/p>\n\n\n\n<p><code>rwnd = 10KB<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64\u6700\u7ec8\u53d1\u9001\u7a97\u53e3\uff1a<\/p>\n\n\n\n<p><code>min(15KB, 10KB) = 10KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u8fd9\u9898\u6700\u5bb9\u6613\u9519\u5728\u54ea<\/h3>\n\n\n\n<p>\u6700\u5e38\u89c1\u9519\u8bef\u662f\u53ea\u7b97\u51fa\u4e86 <code>cwnd = 15KB<\/code>\uff0c\u7136\u540e\u76f4\u63a5\u628a\u5b83\u5f53\u7b54\u6848\u3002<br>\u4f46\u9898\u76ee\u95ee\u7684\u662f<strong>\u53d1\u9001\u7a97\u53e3<\/strong>\uff0c\u4e0d\u662f\u62e5\u585e\u7a97\u53e3\u3002<\/p>\n\n\n\n<p>\u53d1\u9001\u7a97\u53e3\u4e00\u5b9a\u8981\u518d\u548c\u63a5\u6536\u7a97\u53e3\u6bd4\u8f83\u4e00\u6b21\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u7b2c5\u9898\uff1a\u95e8\u9650\u521d\u59cb\u4e3a8\uff0ccwnd\u523012\u65f6\u8d85\u65f6\uff0c\u7b2c13\u6b21\u4f20\u8f93\u7a97\u53e3\u591a\u5927<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\u662f\uff1a<\/p>\n\n\n\n<p>TCP \u7684\u6162\u5f00\u59cb\u95e8\u9650\u521d\u59cb\u4e3a <code>8<\/code>\uff08\u5355\u4f4d\u4e3a\u62a5\u6587\u6bb5\uff09\uff0c\u5f53\u62e5\u585e\u7a97\u53e3\u4e0a\u5347\u5230 <code>12<\/code> \u65f6\u53d1\u751f\u8d85\u65f6\uff0cTCP \u5f00\u59cb\u6162\u5f00\u59cb\u548c\u62e5\u585e\u907f\u514d\uff0c\u5219\u7b2c 13 \u6b21\u4f20\u8f93\u65f6\u62e5\u585e\u7a97\u53e3\u5927\u5c0f\u662f\u591a\u5c11\uff1f<\/p>\n\n\n\n<p>\u8fd9\u91cc\u9898\u5e72\u91cc\u7684\u201c\u53d1\u751f\u77ed\u65f6\u201d\u5927\u6982\u7387\u5c31\u662f\u201c\u53d1\u751f\u8d85\u65f6\u201d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u6309\u8003\u7814\u5e38\u89c1\u7b80\u5316\u6a21\u578b\uff0c<strong>\u7b2c 13 \u6b21\u4f20\u8f93\u65f6\u62e5\u585e\u7a97\u53e3\u5927\u5c0f\u4e3a <code>7<\/code><\/strong>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">\u521d\u59cb\u9636\u6bb5<\/h4>\n\n\n\n<p>\u521d\u59cb\u95e8\u9650\uff1a<\/p>\n\n\n\n<p><code>ssthresh = 8<\/code><\/p>\n\n\n\n<p>\u9ed8\u8ba4\u5f00\u59cb\u65f6\uff1a<\/p>\n\n\n\n<p><code>cwnd = 1<\/code><\/p>\n\n\n\n<p>\u4e8e\u662f\u524d\u51e0\u6b21\u4f20\u8f93\u8f6e\u6b21\u7684\u7a97\u53e3\u53d8\u5316\u4e3a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c1\u6b21\uff1a<code>1<\/code><\/li>\n\n\n\n<li>\u7b2c2\u6b21\uff1a<code>2<\/code><\/li>\n\n\n\n<li>\u7b2c3\u6b21\uff1a<code>4<\/code><\/li>\n\n\n\n<li>\u7b2c4\u6b21\uff1a<code>8<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u5230\u8fbe\u95e8\u9650\u540e\u8fdb\u5165\u62e5\u585e\u907f\u514d\uff0c\u6bcf\u6b21\u52a0 1\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c5\u6b21\uff1a<code>9<\/code><\/li>\n\n\n\n<li>\u7b2c6\u6b21\uff1a<code>10<\/code><\/li>\n\n\n\n<li>\u7b2c7\u6b21\uff1a<code>11<\/code><\/li>\n\n\n\n<li>\u7b2c8\u6b21\uff1a<code>12<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6b64\u65f6\u53d1\u751f\u8d85\u65f6\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u53d1\u751f\u8d85\u65f6\u540e<\/h4>\n\n\n\n<p>\u6309\u7167\u8003\u7814\u6807\u51c6\u505a\u6cd5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = 12 \/ 2 = 6<\/code><\/li>\n\n\n\n<li><code>cwnd = 1<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u7136\u540e\u91cd\u65b0\u6162\u5f00\u59cb\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c9\u6b21\uff1a<code>1<\/code><\/li>\n\n\n\n<li>\u7b2c10\u6b21\uff1a<code>2<\/code><\/li>\n\n\n\n<li>\u7b2c11\u6b21\uff1a<code>4<\/code><\/li>\n\n\n\n<li>\u7b2c12\u6b21\uff1a<code>6<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u8fbe\u5230\u95e8\u9650\u540e\u8fdb\u5165\u62e5\u585e\u907f\u514d\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c13\u6b21\uff1a<code>7<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u4e3a\uff1a<\/p>\n\n\n\n<p><code>7<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e3a\u4ec0\u4e48\u6709\u65f6\u4f1a\u770b\u5230\u522b\u7684\u7b54\u6848<\/h3>\n\n\n\n<p>\u8fd9\u662f\u56e0\u4e3a\u4e25\u683c\u5de5\u7a0b\u5b9e\u73b0\u91cc\uff0c\u6162\u5f00\u59cb\u6309 ACK \u589e\u957f\uff0c\u53ef\u80fd\u51fa\u73b0\u201c\u4e0d\u6b63\u597d\u5361\u5728 6\u201d\u8fd9\u79cd\u60c5\u51b5\uff1b\u4f46\u5728\u8003\u7814\u9898\u91cc\uff0c\u901a\u5e38\u90fd\u6309<strong>\u8f6e\u6b21\u6a21\u578b<\/strong>\u548c<strong>\u95e8\u9650\u6574\u9f50\u5207\u6362<\/strong>\u6765\u7b97\uff0c\u4e5f\u5c31\u662f\u628a\u8fc7\u7a0b\u5199\u6210\uff1a<\/p>\n\n\n\n<p><code>1 \u2192 2 \u2192 4 \u2192 8 \u2192 9 \u2192 10 \u2192 11 \u2192 12 \u2192 \u8d85\u65f6 \u2192 1 \u2192 2 \u2192 4 \u2192 6 \u2192 7<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u9053\u9898\u7684\u6807\u51c6\u8003\u8bd5\u7b54\u6848\u4e00\u822c\u53d6 <code>7<\/code>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u8fd9 5 \u9053\u9898\u80cc\u540e\u7684\u7edf\u4e00\u505a\u9898\u6a21\u677f<\/h2>\n\n\n\n<p>\u8fd9\u51e0\u9898\u8868\u9762\u4e0a\u5206\u522b\u5728\u8003\u6325\u624b\u3001\u786e\u8ba4\u53f7\u3001\u8d85\u65f6\u3001\u62e5\u585e\u63a7\u5236\u3001\u53d1\u9001\u7a97\u53e3\uff0c\u4f46\u5b9e\u9645\u4e0a\u90fd\u53ef\u4ee5\u5f52\u5230\u4e00\u4e2a\u6a21\u677f\u91cc\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e00\u7c7b\uff1aRTT \/ \u6325\u624b\u65f6\u95f4\u9898<\/h3>\n\n\n\n<p>\u5148\u753b\u5355\u7a0b\u4f20\u64ad\u65f6\u5ef6\uff1a<\/p>\n\n\n\n<p><code>\u5355\u7a0b = RTT\/2<\/code><\/p>\n\n\n\n<p>\u518d\u6309\u62a5\u6587\u7684\u53d1\u9001\u987a\u5e8f\u5f80\u4e0b\u63a8\uff0c\u8c01\u4ec0\u4e48\u65f6\u5019\u53d1\uff0c\u4ec0\u4e48\u65f6\u5019\u5230\uff0c\u5c31\u80fd\u76f4\u63a5\u7b97\u51fa\u6765\u3002<\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u7684\u5173\u952e\u4e0d\u662f\u80cc\u56fe\uff0c\u800c\u662f\u6293\u4f4f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e00\u6b21\u5355\u5411\u4f20\u64ad\uff1a<code>RTT\/2<\/code><\/li>\n\n\n\n<li>\u4e00\u6765\u4e00\u56de\uff1a<code>RTT<\/code><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e8c\u7c7b\uff1aseq \/ ack \u9898<\/h3>\n\n\n\n<p>\u56fa\u5b9a\u4e24\u4e2a\u539f\u5219\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq<\/code>\uff1a\u672c\u6bb5\u7b2c\u4e00\u4e2a\u5b57\u8282\u7f16\u53f7<\/li>\n\n\n\n<li><code>ack<\/code>\uff1a\u671f\u671b\u6536\u5230\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u7f16\u53f7<\/li>\n<\/ul>\n\n\n\n<p>\u9047\u5230\u201c\u4e2d\u95f4\u4e22\u5931\u3001\u540e\u9762\u5148\u5230\u201d\u7684\u60c5\u51b5\uff0c\u4e00\u5b9a\u8bb0\u4f4f\uff1a<\/p>\n\n\n\n<p><strong>TCP \u91c7\u7528\u7d2f\u8ba1\u786e\u8ba4\uff0c\u786e\u8ba4\u53f7\u4e0d\u80fd\u8de8\u8fc7\u7f3a\u5931\u7684\u90a3\u4e00\u6bb5\u3002<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u4e09\u7c7b\uff1a\u8d85\u65f6\u540e\u7684 cwnd \u9898<\/h3>\n\n\n\n<p>\u76f4\u63a5\u5957\u6a21\u677f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = \u539fcwnd \/ 2<\/code><\/li>\n\n\n\n<li><code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u7136\u540e\u6162\u5f00\u59cb<\/li>\n\n\n\n<li>\u5230\u95e8\u9650\u540e\u6539\u4e3a\u62e5\u585e\u907f\u514d<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c\u56db\u7c7b\uff1a\u53d1\u9001\u7a97\u53e3\u9898<\/h3>\n\n\n\n<p>\u6700\u7ec8\u522b\u5fd8\u4e86\u8fd8\u6709\u63a5\u6536\u65b9\u9650\u5236\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u5f88\u591a\u9898\u6545\u610f\u628a <code>rwnd<\/code> \u5199\u51fa\u6765\uff0c\u5c31\u662f\u4e3a\u4e86\u5361\u8fd9\u4e00\u70b9\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u8fd9\u51e0\u7c7b\u9898\u6700\u5bb9\u6613\u51fa\u9519\u7684\u70b9<\/h2>\n\n\n\n<p>\u8fd9\u90e8\u5206\u5f88\u503c\u5f97\u5355\u72ec\u8bb0\u4e00\u4e0b\uff0c\u56e0\u4e3a\u786e\u5b9e\u662f\u9ad8\u9891\u9677\u9631\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c<strong>\u628a\u670d\u52a1\u5668\u91ca\u653e\u8fde\u63a5\u65f6\u95f4\u548c\u5ba2\u6237\u7aef TIME_WAIT \u6df7\u4e3a\u4e00\u8c08<\/strong>\u3002<br>\u670d\u52a1\u5668\u6536\u5230\u6700\u540e ACK \u5c31\u53ef\u4ee5\u91ca\u653e\uff1b\u5ba2\u6237\u7aef\u8fd8\u53ef\u80fd\u7ee7\u7eed\u7b49 2MSL\uff0c\u8fd9\u4e0d\u662f\u4e00\u56de\u4e8b\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e8c\uff0c<strong>\u628a ack \u5f53\u6210\u201c\u5df2\u6536\u5230\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7\u201d<\/strong>\u3002<br>\u5176\u5b9e <code>ack<\/code> \u662f\u201c\u4e0b\u4e00\u671f\u5f85\u5b57\u8282\u5e8f\u53f7\u201d\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e09\uff0c<strong>\u770b\u5230\u540e\u7eed\u6bb5\u5230\u4e86\uff0c\u5c31\u628a ack \u5f80\u540e\u63a8<\/strong>\u3002<br>\u7d2f\u8ba1\u786e\u8ba4\u4e0d\u5141\u8bb8\u8fd9\u6837\u505a\uff0c\u4e2d\u95f4\u65ad\u4e86\u5c31\u53ea\u80fd\u786e\u8ba4\u5230\u65ad\u70b9\u3002<\/p>\n\n\n\n<p>\u7b2c\u56db\uff0c<strong>\u8d85\u65f6\u540e\u5fd8\u8bb0\u628a cwnd \u91cd\u7f6e\u4e3a 1 MSS<\/strong>\u3002<br>\u5f88\u591a\u4eba\u53ea\u8bb0\u5f97\u95e8\u9650\u51cf\u534a\uff0c\u5fd8\u4e86\u8d85\u65f6\u7684\u6062\u590d\u52a8\u4f5c\u66f4\u731b\u70c8\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e94\uff0c<strong>\u628a cwnd \u5f53\u6210\u6700\u7ec8\u53d1\u9001\u7a97\u53e3<\/strong>\u3002<br>\u53ea\u8981\u9898\u91cc\u7ed9\u4e86 <code>rwnd<\/code>\uff0c\u5c31\u8981\u505a <code>min(cwnd, rwnd)<\/code>\u3002<\/p>\n\n\n\n<p>\u7b2c\u516d\uff0c<strong>\u4f20\u8f93\u8f6e\u6b21\u9898\u91cc\u628a\u201c\u7a97\u53e3\u589e\u957f\u540e\u7684\u503c\u201d\u548c\u201c\u672c\u8f6e\u53d1\u9001\u65f6\u4f7f\u7528\u7684\u503c\u201d\u641e\u6df7<\/strong>\u3002<br>\u8fd9\u7c7b\u9898\u5efa\u8bae\u7edf\u4e00\u6309\u201c\u7b2c k \u6b21\u4f20\u8f93\u65f6\uff0ccwnd \u662f\u591a\u5c11\u201d\u6765\u5217\u5e8f\u5217\uff0c\u522b\u5728\u8111\u4e2d\u8df3\u6765\u8df3\u53bb\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u8865\u5145\u4f8b\u9898\uff1aTCP \u4e2d RTT\u3001\u6162\u5f00\u59cb\u3001\u62e5\u585e\u7a97\u53e3\u3001\u53d1\u9001\u7a97\u53e3\u7684\u7efc\u5408\u9898<\/h2>\n\n\n\n<p>\u672c\u8d28\u4e0a\u8fd8\u662f\u56f4\u7ed5\u540c\u4e00\u5957\u89c4\u5219\u5728\u8003\uff0c\u53ea\u662f\u9898\u5e72\u6362\u4e86\u4e0d\u540c\u8bf4\u6cd5\u3002\u5148\u628a\u8fd9\u5957\u89c4\u5219\u518d\u538b\u4e00\u904d\uff0c\u540e\u9762\u6bcf\u9898\u5c31\u4f1a\u5f88\u987a\u3002<\/p>\n\n\n\n<p>\u5728 408 \u9898\u91cc\uff0c\u82e5\u9898\u76ee\u6ca1\u6709\u7279\u522b\u8bf4\u660e\uff0c\u9ed8\u8ba4\u6309\u8fd9\u79cd\u7b80\u5316\u6a21\u578b\u6765\u505a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8fde\u63a5\u5efa\u7acb\u6210\u529f\u540e\uff0c\u521d\u59cb <code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0c<code>cwnd<\/code> \u8fd1\u4f3c\u7ffb\u500d<\/li>\n\n\n\n<li>\u5230\u8fbe <code>ssthresh<\/code> \u540e\u8f6c\u5165\u62e5\u585e\u907f\u514d\uff0c\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0c<code>cwnd<\/code> \u589e\u52a0 <code>1 MSS<\/code><\/li>\n\n\n\n<li>\u53d1\u9001\u7a97\u53e3 <code>swnd = min(cwnd, rwnd)<\/code><\/li>\n\n\n\n<li>\u6ca1\u6709\u62e5\u585e\u65f6\uff0c\u51b3\u5b9a\u53d1\u9001\u7a97\u53e3\u4e0a\u9650\u7684\u5f80\u5f80\u5c31\u662f <code>rwnd<\/code><\/li>\n\n\n\n<li>\u51fa\u73b0 <code>3<\/code> \u4e2a\u5197\u4f59 ACK\uff0c\u4e00\u822c\u6309 <strong>TCP Reno \u7684\u5feb\u91cd\u4f20 + \u5feb\u6062\u590d<\/strong> \u6765\u505a<\/li>\n\n\n\n<li>\u51fa\u73b0 <strong>\u8d85\u65f6<\/strong>\uff0c\u4e00\u822c\u6309 <code>ssthresh = cwnd\/2<\/code>\uff0c<code>cwnd = 1 MSS<\/code> \u6765\u505a<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">1. \u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 20KB\uff0c\u9700\u8981\u591a\u4e45<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<p>\u5df2\u5efa\u7acb TCP \u8fde\u63a5\uff0c<code>MSS = 2KB<\/code>\uff0c\u63a5\u6536\u7a97\u53e3\u59cb\u7ec8\u4e3a <code>20KB<\/code>\uff0c<code>ssthresh = 16KB<\/code>\uff0c<code>RTT = 10ms<\/code>\uff0c\u53d1\u9001\u65f6\u5ef6\u5ffd\u7565\uff0c\u65e0\u62e5\u585e\u3002\u95ee\u7532\u7684\u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>20KB<\/code> \u7ecf\u8fc7\u591a\u4e45\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u7b54\u6848\u662f\uff1a<strong>50ms\uff08B\uff09<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u53d1\u9001\u7a97\u53e3\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u7531\u4e8e <code>rwnd = 20KB<\/code> \u6052\u5b9a\uff0c\u6240\u4ee5\u53ea\u8981\u770b <code>cwnd<\/code> \u4ec0\u4e48\u65f6\u5019\u589e\u957f\u5230 <code>20KB<\/code> \u5373\u53ef\u3002<\/p>\n\n\n\n<p>\u521d\u59cb\uff1a<\/p>\n\n\n\n<p><code>cwnd = 1 MSS = 2KB<\/code><\/p>\n\n\n\n<p>\u53c8\u56e0\u4e3a <code>ssthresh = 16KB<\/code>\uff0c\u6240\u4ee5\u5148\u6162\u5f00\u59cb\uff0c\u540e\u62e5\u585e\u907f\u514d\u3002<\/p>\n\n\n\n<p>\u6309 RTT \u6f14\u5316\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\uff1a<code>cwnd = 2KB<\/code><\/li>\n\n\n\n<li>1RTT \u540e\uff1a<code>4KB<\/code><\/li>\n\n\n\n<li>2RTT \u540e\uff1a<code>8KB<\/code><\/li>\n\n\n\n<li>3RTT \u540e\uff1a<code>16KB<\/code><\/li>\n\n\n\n<li>4RTT \u540e\uff1a<code>18KB<\/code><\/li>\n\n\n\n<li>5RTT \u540e\uff1a<code>20KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6bcf\u4e2a RTT \u662f <code>10ms<\/code>\uff0c\u6240\u4ee5\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>20KB<\/code> \u7684\u65f6\u95f4\u4e3a\uff1a<\/p>\n\n\n\n<p><code>5 \u00d7 10ms = 50ms<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u6613\u9519\u70b9<\/h3>\n\n\n\n<p>\u6700\u5bb9\u6613\u9519\u6210 <code>40ms<\/code>\u3002\u9519\u56e0\u5728\u4e8e\u628a <code>16KB<\/code> \u5230 <code>20KB<\/code> \u8fd9\u4e00\u6bb5\u8fd8\u5f53\u6210\u7ffb\u500d\u589e\u957f\u4e86\u3002\u5176\u5b9e\u5230\u8fbe\u95e8\u9650 <code>16KB<\/code> \u540e\uff0c\u5c31\u8fdb\u5165\u62e5\u585e\u907f\u514d\uff0c\u6bcf RTT \u53ea\u589e\u52a0 <code>1 MSS = 2KB<\/code>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">2. \u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u672c RTT \u53d1\u4e86 k \u4e2a\u6bb5\uff0c\u4e0b\u4e00\u4e2a RTT \u53d1\u591a\u5c11\u4e2a\u6bb5<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<p>\u67d0 TCP \u8fde\u63a5\u6b63\u5904\u4e8e\u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u5728\u67d0\u4e2a RTT \u5185\u53d1\u9001\u4e86 <code>k<\/code> \u4e2a\u6570\u636e\u6bb5\u3002\u82e5\u4ecd\u7136\u5904\u4e8e\u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u5219\u4e0b\u4e00\u4e2a RTT \u5185\u5c06\u53d1\u9001\u591a\u5c11\u4e2a\u6570\u636e\u6bb5\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u7b54\u6848\u662f\uff1a<strong>2k<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u6162\u5f00\u59cb\u7684\u6838\u5fc3\u7279\u5f81\u5c31\u662f\uff1a<strong>\u62e5\u585e\u7a97\u53e3\u6309 RTT \u8fd1\u4f3c\u6307\u6570\u589e\u957f<\/strong>\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8fd9\u4e00\u8f6e\u80fd\u53d1 <code>k<\/code> \u4e2a\u6bb5<\/li>\n\n\n\n<li>\u4e0b\u4e00\u8f6e\u5c31\u80fd\u53d1 <code>2k<\/code> \u4e2a\u6bb5<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u662f\uff1a<\/p>\n\n\n\n<p><code>2k<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u6613\u9519\u70b9<\/h3>\n\n\n\n<p>\u8fd9\u4e2a\u9898\u975e\u5e38\u57fa\u7840\uff0c\u4f46\u5f88\u5bb9\u6613\u548c\u62e5\u585e\u907f\u514d\u6df7\u6dc6\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6162\u5f00\u59cb\uff1a\u7ffb\u500d<\/li>\n\n\n\n<li>\u62e5\u585e\u907f\u514d\uff1a\u6bcf RTT \u52a0 1 \u4e2a MSS<\/li>\n<\/ul>\n\n\n\n<p>\u53ea\u8981\u770b\u5230\u9898\u5e72\u660e\u786e\u5199\u4e86\u201c\u4ecd\u7136\u4fdd\u6301\u5728\u6162\u5f00\u59cb\u9636\u6bb5\u201d\uff0c\u90a3\u5c31\u662f\u76f4\u63a5\u7ffb\u500d\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">3. cwnd = 34KB \u65f6\u6536\u5230 3 \u4e2a\u5197\u4f59 ACK\uff0c4RTT \u540e\u7a97\u53e3\u591a\u5927<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<p>\u5728\u4e00\u4e2a TCP \u8fde\u63a5\u4e2d\uff0c<code>MSS = 1KB<\/code>\uff0c\u5f53 <code>cwnd = 34KB<\/code> \u65f6\u6536\u5230\u4e86 <code>3<\/code> \u4e2a\u5197\u4f59 ACK\u3002\u82e5\u63a5\u4e0b\u6765\u7684 <code>4RTT<\/code> \u5185\u4f20\u8f93\u90fd\u6210\u529f\uff0c\u5219\u8fd9\u4e9b\u62a5\u6587\u6bb5\u90fd\u88ab\u786e\u8ba4\u540e\uff0c\u62e5\u585e\u7a97\u53e3\u5927\u5c0f\u662f\u591a\u5c11\u3002<\/p>\n\n\n\n<p>\u9009\u9879\u91cc\u6709\uff1a<code>21KB\u300120KB\u300116KB\u30018KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u6309\u8003\u7814\u91cc\u8fd9\u7c7b\u9898\u7684\u5e38\u89c4\u505a\u6cd5\uff0c\u7b54\u6848\u662f\uff1a<strong>21KB\uff08D\uff09<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u8fd9\u9898\u548c\u201c\u8d85\u65f6\u201d\u4e0d\u4e00\u6837\u3002<br>\u9898\u76ee\u660e\u786e\u8bf4\u7684\u662f\uff1a<strong>\u6536\u5230 3 \u4e2a\u5197\u4f59 ACK<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u901a\u5e38\u6309 <strong>TCP Reno \u7684\u5feb\u91cd\u4f20 + \u5feb\u6062\u590d<\/strong> \u6765\u5904\u7406\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e00\u6b65\uff1a\u8bbe\u7f6e\u95e8\u9650<\/h4>\n\n\n\n<p><code>ssthresh = 34 \/ 2 = 17KB<\/code><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e8c\u6b65\uff1a\u8fdb\u5165\u5feb\u6062\u590d<\/h4>\n\n\n\n<p>\u6536\u5230 <code>3<\/code> \u4e2a\u5197\u4f59 ACK \u540e\uff0cReno \u4e00\u822c\u4ee4\uff1a<\/p>\n\n\n\n<p><code>cwnd = ssthresh + 3 MSS = 17 + 3 = 20KB<\/code><\/p>\n\n\n\n<p>\u8fd9\u662f\u56e0\u4e3a\u90a3 <code>3<\/code> \u4e2a\u5197\u4f59 ACK \u8868\u793a\u7f51\u7edc\u4e2d\u4ecd\u6709 3 \u4e2a\u62a5\u6587\u6bb5\u79bb\u5f00\u4e86\u53d1\u9001\u65b9\u5e76\u5230\u8fbe\u4e86\u63a5\u6536\u65b9\uff0c\u53ea\u662f\u6709\u4e00\u4e2a\u4e22\u5931\u4e86\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u7b2c\u4e09\u6b65\uff1a\u540e\u7eed\u6210\u529f\u4f20\u8f93 4RTT<\/h4>\n\n\n\n<p>\u5728\u8fd9\u7c7b\u8003\u9898\u91cc\uff0c\u540e\u7eed\u901a\u5e38\u6309\u7ebf\u6027\u589e\u957f\u6765\u5904\u7406\u3002<br>\u6536\u5230\u5bf9\u91cd\u4f20\u6bb5\u7684\u786e\u8ba4\u540e\uff0c\u9000\u51fa\u5feb\u6062\u590d\uff0c\u8fdb\u5165\u62e5\u585e\u907f\u514d\uff0c<code>cwnd<\/code> \u56de\u5230 <code>ssthresh = 17KB<\/code>\uff0c\u7136\u540e\u6bcf RTT \u589e\u957f <code>1KB<\/code>\u3002<br>\u4f46\u5f88\u591a 408 \u9898\u76ee\u548c\u9009\u9879\u8bbe\u8ba1\uff0c\u662f\u76f4\u63a5\u628a\u201c3 \u4e2a\u5197\u4f59 ACK \u89e6\u53d1\u540e\u7684\u53ef\u53d1\u9001\u7a97\u53e3\u201d\u89c6\u4f5c\u540e\u7eed\u589e\u957f\u8d77\u70b9\uff0c\u7ed3\u5408\u9009\u9879\u901a\u5e38\u53d6 <strong>21KB<\/strong>\u3002<\/p>\n\n\n\n<p>\u66f4\u7a33\u59a5\u7684\u8003\u573a\u5224\u65ad\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u82e5\u9898\u76ee\u662f\u201c<strong>\u8d85\u65f6<\/strong>\u201d \u2192 \u591a\u534a\u8d70 <code>1 \u2192 2 \u2192 4 \u2192 8 \u2192 16<\/code><\/li>\n\n\n\n<li>\u82e5\u9898\u76ee\u662f\u201c<strong>3 \u4e2a\u5197\u4f59 ACK<\/strong>\u201d \u2192 \u591a\u534a\u8003 <strong>Reno \u5feb\u6062\u590d<\/strong>\uff0c\u7b54\u6848\u4f1a\u843d\u5728 <code>20KB<\/code> \u6216 <code>21KB<\/code><\/li>\n\n\n\n<li>\u7ed3\u5408\u672c\u9898\u7ed9\u7684\u6807\u51c6\u9009\u9879\uff0c\u5e38\u89c4\u7b54\u6848\u53d6 <strong>21KB<\/strong><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u8fd9\u9898\u4e3a\u4ec0\u4e48\u548c\u201c\u8d85\u65f6\u201d\u90a3\u9898\u7b54\u6848\u4e0d\u4e00\u6837<\/h3>\n\n\n\n<p>\u56e0\u4e3a\u5b83\u4eec\u89e6\u53d1\u7684\u662f\u4e24\u79cd\u4e0d\u540c\u673a\u5236\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u8d85\u65f6<\/strong>\uff1a\u8bf4\u660e\u62e5\u585e\u66f4\u4e25\u91cd\uff0c<code>cwnd<\/code> \u76f4\u63a5\u91cd\u7f6e\u4e3a <code>1 MSS<\/code><\/li>\n\n\n\n<li><strong>3 \u4e2a\u5197\u4f59 ACK<\/strong>\uff1a\u8bf4\u660e\u7f51\u7edc\u91cc\u8fd8\u6709\u6570\u636e\u5728\u6d41\u52a8\uff0c\u66f4\u53ef\u80fd\u662f\u4e2a\u522b\u62a5\u6587\u4e22\u5931\uff0c\u56e0\u6b64\u4e0d\u5fc5\u964d\u5f97\u90a3\u4e48\u72e0<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u9898\u4e0d\u4f1a\u56de\u5230 <code>1KB<\/code> \u91cd\u65b0\u6162\u5f00\u59cb\uff0c\u4e5f\u5c31\u4e0d\u4f1a\u5f97\u5230 <code>16KB<\/code> \u90a3\u79cd\u7b54\u6848\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">4. \u4e0b\u4e00\u4e2a RTT \u6700\u591a\u8fd8\u80fd\u53d1\u9001\u591a\u5c11\u6570\u636e<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<p>A \u548c B \u5efa\u7acb TCP \u8fde\u63a5\uff0c<code>MSS = 1KB<\/code>\u3002\u67d0\u65f6\u523b\uff0c<code>ssthresh = 2KB<\/code>\uff0cA \u7684 <code>cwnd = 4KB<\/code>\u3002<br>\u5728\u63a5\u4e0b\u6765\u7684 <code>1RTT<\/code> \u5185\uff0cA \u5411 B \u53d1\u9001\u4e86 <code>4KB<\/code> \u6570\u636e\u5e76\u6536\u5230\u786e\u8ba4\uff0c\u786e\u8ba4\u62a5\u6587\u4e2d\u7684\u7a97\u53e3\u5b57\u6bb5\u503c\u4e3a <code>2KB<\/code>\u3002\u95ee\u4e0b\u4e00\u4e2a RTT \u4e2d\uff0cA \u6700\u591a\u8fd8\u80fd\u53d1\u9001\u591a\u5c11\u6570\u636e\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u7b54\u6848\u662f\uff1a<strong>2KB<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u5148\u770b\u62e5\u585e\u63a7\u5236\u72b6\u6001\u3002<\/p>\n\n\n\n<p>\u56e0\u4e3a\uff1a<\/p>\n\n\n\n<p><code>cwnd = 4KB &gt; ssthresh = 2KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u6b64\u65f6\u5df2\u7ecf\u5904\u4e8e<strong>\u62e5\u585e\u907f\u514d\u9636\u6bb5<\/strong>\u3002<\/p>\n\n\n\n<p>\u5728\u62e5\u585e\u907f\u514d\u9636\u6bb5\uff0c\u7ecf\u8fc7 1RTT \u540e\uff1a<\/p>\n\n\n\n<p><code>cwnd = 4KB + 1KB = 5KB<\/code><\/p>\n\n\n\n<p>\u4f46\u9898\u76ee\u53c8\u7ed9\u4e86\u786e\u8ba4\u62a5\u6587\u4e2d\u7684\u7a97\u53e3\u5b57\u6bb5\u503c\uff1a<\/p>\n\n\n\n<p><code>rwnd = 2KB<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64\u53d1\u9001\u7a97\u53e3\u4e3a\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd) = min(5KB, 2KB) = 2KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u4e0b\u4e00\u4e2a RTT \u4e2d\uff0cA \u6700\u591a\u53d1\u9001\uff1a<\/p>\n\n\n\n<p><code>2KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u6613\u9519\u70b9<\/h3>\n\n\n\n<p>\u6700\u5bb9\u6613\u53ea\u770b <code>cwnd<\/code>\uff0c\u7b97\u51fa <code>5KB<\/code> \u5c31\u76f4\u63a5\u9009\u3002<br>\u4f46\u9898\u5e72\u4e13\u95e8\u544a\u8bc9\u4e86\u201c\u786e\u8ba4\u62a5\u6587\u4e2d\u7684\u7a97\u53e3\u5b57\u6bb5\u503c\u4e3a 2KB\u201d\uff0c\u8fd9\u5c31\u662f\u5728\u63d0\u9192\uff1a\u8fd8\u8981\u53d7\u63a5\u6536\u7a97\u53e3\u7ea6\u675f\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">5. \u53d1\u9001\u65b9\u4f55\u65f6\u80fd\u53d1\u51fa\u7b2c\u4e00\u4e2a\u201c\u5b8c\u5168\u7a97\u53e3\u201d24KB<\/h2>\n\n\n\n<p>\u9898\u76ee\u5927\u610f\uff1a<\/p>\n\n\n\n<p>\u65e0\u62e5\u585e\uff0c<code>RTT = 10ms<\/code>\uff0c\u91c7\u7528\u6162\u5f00\u59cb\uff0c<code>rwnd = 24KB<\/code>\uff0c<code>MSS = 2KB<\/code>\u3002\u95ee\u53d1\u9001\u65b9\u80fd\u53d1\u9001\u51fa\u7b2c\u4e00\u4e2a\u5b8c\u5168\u7a97\u53e3\uff0c\u4e5f\u5c31\u662f\u53d1\u9001\u7a97\u53e3\u8fbe\u5230 <code>24KB<\/code>\uff0c\u9700\u8981\u7684\u65f6\u95f4\u662f\u591a\u5c11\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7ed3\u8bba<\/h3>\n\n\n\n<p>\u7b54\u6848\u662f\uff1a<strong>40ms<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u9898\u8fc7\u7a0b<\/h3>\n\n\n\n<p>\u4ecd\u7136\u53ea\u770b <code>cwnd<\/code> \u589e\u957f\u5230\u4ec0\u4e48\u65f6\u5019\u4e0d\u5c0f\u4e8e <code>24KB<\/code>\u3002<\/p>\n\n\n\n<p>\u521d\u59cb\uff1a<\/p>\n\n\n\n<p><code>cwnd = 1 MSS = 2KB<\/code><\/p>\n\n\n\n<p>\u6162\u5f00\u59cb\u9636\u6bb5\u6bcf RTT \u7ffb\u500d\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\uff1a<code>2KB<\/code><\/li>\n\n\n\n<li>1RTT \u540e\uff1a<code>4KB<\/code><\/li>\n\n\n\n<li>2RTT \u540e\uff1a<code>8KB<\/code><\/li>\n\n\n\n<li>3RTT \u540e\uff1a<code>16KB<\/code><\/li>\n\n\n\n<li>4RTT \u540e\uff1a<code>32KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6b64\u65f6\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd) = min(32KB, 24KB) = 24KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u5230\u7b2c <code>4RTT<\/code> \u672b\uff0c\u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>24KB<\/code>\u3002<\/p>\n\n\n\n<p>\u56e0\u4e3a\uff1a<\/p>\n\n\n\n<p><code>RTT = 10ms<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u6240\u9700\u65f6\u95f4\uff1a<\/p>\n\n\n\n<p><code>4 \u00d7 10ms = 40ms<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u6613\u9519\u70b9<\/h3>\n\n\n\n<p>\u8fd9\u9898\u5bb9\u6613\u7ea0\u7ed3\u201c\u8fbe\u5230 24KB\u201d\u8fd8\u662f\u201c\u771f\u6b63\u628a 24KB \u53d1\u5b8c\u201d\u3002<br>408 \u5e38\u89c4\u505a\u6cd5\u662f\uff1a<strong>\u53d1\u9001\u7a97\u53e3\u9996\u6b21\u8fbe\u5230 24KB \u7684\u90a3\u4e2a\u65f6\u523b<\/strong> \u5c31\u7b97\u8fbe\u6210\u6761\u4ef6\uff0c\u4e5f\u5c31\u662f <code>40ms<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u8fd9\u51e0\u9053\u9898\u80cc\u540e\u7684\u7edf\u4e00\u65b9\u6cd5<\/h2>\n\n\n\n<p>\u505a\u5230\u8fd9\u91cc\uff0c\u5176\u5b9e\u89c4\u5f8b\u5df2\u7ecf\u975e\u5e38\u6e05\u695a\u4e86\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e00\u7c7b\uff1a\u95ee\u53d1\u9001\u7a97\u53e3\u4ec0\u4e48\u65f6\u5019\u8fbe\u5230\u67d0\u503c<\/h3>\n\n\n\n<p>\u5148\u7b97 <code>cwnd<\/code> \u7684\u589e\u957f\uff0c\u518d\u548c <code>rwnd<\/code> \u6bd4\u8f83\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u82e5 <code>rwnd<\/code> \u6052\u5b9a\uff0c\u5c31\u57fa\u672c\u7b49\u4ef7\u4e8e\u95ee <code>cwnd<\/code> \u4ec0\u4e48\u65f6\u5019\u957f\u5230\u90a3\u4e2a\u503c\u3002<br>\u82e5 <code>rwnd<\/code> \u53d8\u5316\uff0c\u5c31\u5fc5\u987b\u4e24\u8fb9\u4e00\u8d77\u770b\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e00\u7c7b\uff1a\u95ee\u4e0b\u4e00\u4e2a RTT \u80fd\u53d1\u591a\u5c11<\/h3>\n\n\n\n<p>\u6838\u5fc3\u4e0d\u662f\u53ea\u770b <code>cwnd<\/code>\uff0c\u800c\u662f\u770b\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u9898\u76ee\u53ea\u8981\u7ed9\u4e86\u786e\u8ba4\u62a5\u6587\u4e2d\u7684\u7a97\u53e3\u503c\uff0c\u5341\u6709\u516b\u4e5d\u5c31\u662f\u8981\u5361\u8fd9\u4e2a\u70b9\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e00\u7c7b\uff1a\u95ee\u6162\u5f00\u59cb\u9636\u6bb5\u4e0b\u4e00\u8f6e\u53d1\u591a\u5c11\u6bb5<\/h3>\n\n\n\n<p>\u8fd9\u7c7b\u662f\u6700\u76f4\u63a5\u7684\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u672c\u8f6e <code>k<\/code><\/li>\n\n\n\n<li>\u4e0b\u8f6e <code>2k<\/code><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u4e00\u7c7b\uff1a\u95ee\u5197\u4f59 ACK \u4e0e\u8d85\u65f6\u7684\u533a\u522b<\/h3>\n\n\n\n<p>\u4e00\u5b9a\u8981\u5206\u6e05\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u8d85\u65f6<\/strong>\uff1a\u964d\u5f97\u72e0\uff0c<code>cwnd<\/code> \u56de\u5230 <code>1 MSS<\/code><\/li>\n\n\n\n<li><strong>3 \u4e2a\u5197\u4f59 ACK<\/strong>\uff1a\u4e00\u822c\u6309 Reno\uff0c\u8d70\u5feb\u91cd\u4f20\u3001\u5feb\u6062\u590d\uff0c\u4e0d\u4f1a\u76f4\u63a5\u6389\u56de 1<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">TCP \u4e2d RTT\u3001seq\/ack\u3001cwnd\u3001rwnd\u3001\u6162\u5f00\u59cb\u3001\u5feb\u6062\u590d\u9898\u578b\u603b\u8868<\/h2>\n\n\n\n<p>\u6700\u8fd1\u628a TCP \u8fd9\u4e00\u5757\u53cd\u590d\u505a\u9898\u4e4b\u540e\uff0c\u4f1a\u53d1\u73b0\u5f88\u591a\u9898\u867d\u7136\u8868\u9762\u957f\u5f97\u4e0d\u4e00\u6837\uff0c\u4f46\u771f\u6b63\u53cd\u590d\u5728\u8003\u7684\u4e1c\u897f\u5176\u5b9e\u5e76\u4e0d\u591a\u3002\u6838\u5fc3\u65e0\u975e\u5c31\u662f\u4e09\u6761\u4e3b\u7ebf\uff1a\u7b2c\u4e00\u6761\u662f\u62a5\u6587\u6bb5\u91cc\u7684 <code>seq<\/code> \u548c <code>ack<\/code> \u600e\u4e48\u7406\u89e3\u3001\u600e\u4e48\u8ba1\u7b97\uff1b\u7b2c\u4e8c\u6761\u662f\u8fde\u63a5\u5efa\u7acb\u4e0e\u91ca\u653e\u8fc7\u7a0b\u4e2d\uff0c\u65f6\u95f4\u3001RTT\u3001\u62a5\u6587\u5f80\u8fd4\u600e\u4e48\u63a8\uff1b\u7b2c\u4e09\u6761\u662f\u62e5\u585e\u63a7\u5236\u4e0e\u6d41\u91cf\u63a7\u5236\uff0c\u4e5f\u5c31\u662f <code>cwnd<\/code>\u3001<code>rwnd<\/code>\u3001\u53d1\u9001\u7a97\u53e3\u3001\u6162\u5f00\u59cb\u3001\u62e5\u585e\u907f\u514d\u3001\u5feb\u91cd\u4f20\u3001\u5feb\u6062\u590d\u8fd9\u4e9b\u6982\u5ff5\u5982\u4f55\u4e32\u8d77\u6765\u3002\u53ea\u8981\u8fd9\u4e09\u6761\u4e3b\u7ebf\u80fd\u7406\u987a\uff0c\u7edd\u5927\u591a\u6570 TCP \u8ba1\u7b97\u9898\u90fd\u80fd\u843d\u5230\u56fa\u5b9a\u6a21\u677f\u91cc\u53bb\u505a\u3002<\/p>\n\n\n\n<p>\u8fd9\u4efd\u7b14\u8bb0\u5c31\u4e13\u95e8\u628a\u8fd9\u4e00\u5757\u6574\u7406\u6210\u4e00\u4e2a\u53ef\u4ee5\u76f4\u63a5\u590d\u4e60\u548c\u5237\u9898\u65f6\u7ffb\u770b\u7684\u603b\u8868\uff0c\u4e0d\u53ea\u8bb2\u201c\u662f\u4ec0\u4e48\u201d\uff0c\u66f4\u5f3a\u8c03\u201c\u600e\u4e48\u8003\u201d\u201c\u600e\u4e48\u505a\u201d\u201c\u54ea\u91cc\u5bb9\u6613\u9519\u201d\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001\u5148\u628a\u6700\u6838\u5fc3\u7684\u51e0\u4e2a\u91cf\u5f7b\u5e95\u5206\u6e05<\/h2>\n\n\n\n<p>TCP \u9898\u76ee\u6700\u5bb9\u6613\u4e71\uff0c\u5176\u5b9e\u4e0d\u662f\u56e0\u4e3a\u516c\u5f0f\u590d\u6742\uff0c\u800c\u662f\u56e0\u4e3a\u53d8\u91cf\u592a\u591a\uff0c\u770b\u8d77\u6765\u90fd\u5f88\u50cf\u3002\u6240\u4ee5\u6700\u5f00\u59cb\u4e00\u5b9a\u8981\u5148\u628a\u51e0\u4e2a\u6700\u6838\u5fc3\u7684\u91cf\u5206\u6e05\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. RTT<\/h3>\n\n\n\n<p>RTT \u662f\u5f80\u8fd4\u65f6\u95f4\uff0c\u4e5f\u5c31\u662f\u4e00\u4e2a\u62a5\u6587\u4ece\u53d1\u9001\u7aef\u51fa\u53d1\uff0c\u5230\u63a5\u6536\u7aef\uff0c\u518d\u4ece\u63a5\u6536\u7aef\u8fd4\u56de\u53d1\u9001\u7aef\u6240\u7ecf\u5386\u7684\u603b\u65f6\u95f4\u3002<\/p>\n\n\n\n<p>\u5728\u505a\u9898\u65f6\uff0c\u6700\u5e38\u7528\u7684\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>\u5355\u7a0b\u4f20\u64ad\u65f6\u5ef6 = RTT \/ 2<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u53ea\u8981\u9898\u76ee\u51fa\u73b0\u201c\u67d0\u65f6\u523b\u53d1\u9001 FIN\u201d\u201c\u67d0\u65f6\u523b\u6536\u5230 ACK\u201d\u201c\u6700\u77ed\u7ecf\u8fc7\u591a\u4e45\u5230\u8fbe\u5bf9\u7aef\u201d\u4e4b\u7c7b\u7684\u65f6\u95f4\u9898\uff0c\u7b2c\u4e00\u53cd\u5e94\u5c31\u662f\u628a\u4e00\u4e2a RTT \u62c6\u6210\u4e24\u4e2a <code>RTT\/2<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. seq<\/h3>\n\n\n\n<p><code>seq<\/code> \u6307\u7684\u662f\uff1a<strong>\u672c TCP \u62a5\u6587\u6bb5\u4e2d\u6570\u636e\u90e8\u5206\u7b2c\u4e00\u4e2a\u5b57\u8282\u7684\u5e8f\u53f7<\/strong>\u3002<\/p>\n\n\n\n<p>\u6ce8\u610f\u8fd9\u91cc\u662f\u201c\u6570\u636e\u90e8\u5206\u7b2c\u4e00\u4e2a\u5b57\u8282\u201d\u7684\u7f16\u53f7\uff0c\u4e0d\u662f\u201c\u7b2c\u51e0\u4e2a\u62a5\u6587\u6bb5\u201d\uff0c\u4e5f\u4e0d\u662f\u201c\u8fd9\u4e2a\u62a5\u6587\u6bb5\u603b\u5171\u53d1\u4e86\u591a\u5c11\u5b57\u8282\u201d\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u5982\u679c\u4e00\u4e2a\u6bb5\u7684 <code>seq = 1000<\/code>\uff0c\u800c\u5b83\u643a\u5e26 <code>400B<\/code> \u6570\u636e\uff0c\u90a3\u5b83\u8986\u76d6\u7684\u5b57\u8282\u8303\u56f4\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>1000 ~ 1399<\/code><\/p>\n\n\n\n<p>\u4e0b\u4e00\u6bb5\u5982\u679c\u7d27\u8ddf\u5728\u5b83\u540e\u9762\uff0c\u90a3\u4e48\u4e0b\u4e00\u6bb5\u7684\u8d77\u59cb\u5e8f\u53f7\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>1400<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. ack<\/h3>\n\n\n\n<p><code>ack<\/code> \u6307\u7684\u662f\uff1a<strong>\u63a5\u6536\u65b9\u4e0b\u4e00\u6b65\u671f\u671b\u6536\u5230\u7684\u5b57\u8282\u5e8f\u53f7<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u4e2a\u5b9a\u4e49\u5f88\u5173\u952e\u3002\u5b83\u4e0d\u662f\u201c\u5df2\u7ecf\u6536\u5230\u7684\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7\u201d\uff0c\u800c\u662f\u201c\u8fd8\u60f3\u6536\u5230\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7\u201d\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u5982\u679c\u67d0\u4e00\u65b9\u5df2\u7ecf\u6309\u5e8f\u6536\u5230\u4e86 <code>1 ~ 500<\/code> \u53f7\u5b57\u8282\uff0c\u90a3\u4e48\u5b83\u8fd4\u56de\u7684\u786e\u8ba4\u53f7\u5e94\u8be5\u662f\uff1a<\/p>\n\n\n\n<p><code>ack = 501<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4. rwnd<\/h3>\n\n\n\n<p><code>rwnd<\/code> \u662f\u63a5\u6536\u7a97\u53e3\uff0c\u5c5e\u4e8e<strong>\u6d41\u91cf\u63a7\u5236<\/strong>\uff0c\u672c\u8d28\u4e0a\u53cd\u6620\u7684\u662f\u63a5\u6536\u65b9\u7f13\u5b58\u8fd8\u6709\u591a\u5c11\u7a7a\u95f4\u3002<\/p>\n\n\n\n<p>\u63a5\u6536\u65b9\u901a\u8fc7 TCP \u9996\u90e8\u91cc\u7684\u201c\u7a97\u53e3\u5b57\u6bb5\u201d\u544a\u8bc9\u53d1\u9001\u65b9\uff1a\u6211\u8fd8\u80fd\u518d\u6536\u591a\u5c11\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5 <code>rwnd<\/code> \u4f53\u73b0\u7684\u662f<strong>\u63a5\u6536\u65b9\u7684\u5904\u7406\/\u7f13\u5b58\u80fd\u529b\u9650\u5236<\/strong>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">5. cwnd<\/h3>\n\n\n\n<p><code>cwnd<\/code> \u662f\u62e5\u585e\u7a97\u53e3\uff0c\u5c5e\u4e8e<strong>\u62e5\u585e\u63a7\u5236<\/strong>\uff0c\u662f\u53d1\u9001\u65b9\u81ea\u5df1\u6839\u636e\u7f51\u7edc\u62e5\u585e\u72b6\u51b5\u4f30\u8ba1\u51fa\u6765\u7684\u201c\u73b0\u5728\u6211\u6700\u591a\u8be5\u53d1\u591a\u5c11\u201d\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5 <code>cwnd<\/code> \u4f53\u73b0\u7684\u662f<strong>\u7f51\u7edc\u627f\u53d7\u80fd\u529b\u9650\u5236<\/strong>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">6. \u53d1\u9001\u7a97\u53e3 swnd<\/h3>\n\n\n\n<p>\u771f\u6b63\u51b3\u5b9a\u201c\u5f53\u524d\u8fd9\u4e00\u8f6e\u6700\u591a\u80fd\u53d1\u591a\u5c11\u201d\u7684\uff0c\u4e0d\u662f\u5355\u72ec\u770b <code>cwnd<\/code>\uff0c\u4e5f\u4e0d\u662f\u5355\u72ec\u770b <code>rwnd<\/code>\uff0c\u800c\u662f\u770b\u4e24\u8005\u4e2d\u66f4\u5c0f\u7684\u90a3\u4e2a\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u8fd9\u4e00\u53e5\u662f\u51e0\u4e4e\u6240\u6709 TCP \u7a97\u53e3\u8ba1\u7b97\u9898\u7684\u603b\u5f00\u5173\u3002\u9898\u76ee\u53ea\u8981\u540c\u65f6\u7ed9\u4e86 <code>cwnd<\/code> \u548c\u7a97\u53e3\u5b57\u6bb5\uff0c\u6700\u540e\u5c31\u4e00\u5b9a\u4e0d\u80fd\u5fd8\u8bb0\u6bd4\u8f83\u4e00\u6b21\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001seq \u548c ack \u9898\u7684\u505a\u9898\u4e3b\u7ebf<\/h2>\n\n\n\n<p>TCP \u7684 <code>seq\/ack<\/code> \u9898\uff0c\u5728\u8003\u7814\u9898\u91cc\u975e\u5e38\u9ad8\u9891\u3002\u5b83\u7684\u672c\u8d28\u5176\u5b9e\u5c31\u4e24\u6761\uff1a<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c<code>seq<\/code> \u662f\u6570\u636e\u8d77\u70b9\uff1b<br>\u7b2c\u4e8c\uff0c<code>ack<\/code> \u662f\u4e0b\u4e00\u4e2a\u60f3\u6536\u5230\u7684\u6570\u636e\u7f16\u53f7\u3002<\/p>\n\n\n\n<p>\u4f46\u771f\u6b63\u505a\u9898\u65f6\uff0c\u6700\u5bb9\u6613\u9519\u7684\u70b9\u5728\u4e8e\uff1a<strong>TCP \u7684\u786e\u8ba4\u901a\u5e38\u662f\u7d2f\u8ba1\u786e\u8ba4<\/strong>\u3002\u8fd9\u53e5\u8bdd\u5982\u679c\u6ca1\u7406\u89e3\u900f\uff0c\u9898\u76ee\u5c31\u4f1a\u53cd\u590d\u505a\u9519\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u7d2f\u8ba1\u786e\u8ba4\u662f\u4ec0\u4e48\u610f\u601d<\/h3>\n\n\n\n<p>\u6240\u8c13\u7d2f\u8ba1\u786e\u8ba4\uff0c\u5c31\u662f\u63a5\u6536\u65b9\u53ea\u80fd\u786e\u8ba4\u201c\u5df2\u7ecf\u6309\u5e8f\u8fde\u7eed\u6536\u5230\u201d\u7684\u90a3\u4e00\u90e8\u5206\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u4e2d\u95f4\u5c11\u4e86\u4e00\u6bb5\uff0c\u5373\u4f7f\u540e\u9762\u7684\u62a5\u6587\u6bb5\u5148\u5230\u4e86\uff0c\u786e\u8ba4\u53f7\u4e5f\u4e0d\u80fd\u76f4\u63a5\u8df3\u8fc7\u53bb\u3002<\/p>\n\n\n\n<p>\u4f8b\u5982\uff0c\u53d1\u9001\u65b9\u8fde\u7eed\u53d1\u9001\u4e86\u4e09\u4e2a\u6bb5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u6bb5\uff1a<code>200B<\/code><\/li>\n\n\n\n<li>\u7b2c 2 \u6bb5\uff1a<code>300B<\/code><\/li>\n\n\n\n<li>\u7b2c 3 \u6bb5\uff1a<code>400B<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u5df2\u77e5\u7b2c 3 \u6bb5\u7684 <code>seq = 1000<\/code>\uff0c\u90a3\u4e48\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 2 \u6bb5\u7684 <code>seq = 1000 - 300 = 700<\/code><\/li>\n\n\n\n<li>\u7b2c 1 \u6bb5\u7684 <code>seq = 700 - 200 = 500<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u4e8e\u662f\u4e09\u4e2a\u6bb5\u5c31\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u6bb5\uff1a<code>seq = 500<\/code>\uff0c\u8986\u76d6 <code>500 ~ 699<\/code><\/li>\n\n\n\n<li>\u7b2c 2 \u6bb5\uff1a<code>seq = 700<\/code>\uff0c\u8986\u76d6 <code>700 ~ 999<\/code><\/li>\n\n\n\n<li>\u7b2c 3 \u6bb5\uff1a<code>seq = 1000<\/code>\uff0c\u8986\u76d6 <code>1000 ~ 1399<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u5982\u679c\u63a5\u6536\u65b9\u53ea\u6536\u5230\u4e86\u7b2c 1 \u6bb5\u548c\u7b2c 3 \u6bb5\uff0c\u6ca1\u6709\u6536\u5230\u7b2c 2 \u6bb5\uff0c\u90a3\u4e48\u5b83\u867d\u7136\u201c\u770b\u89c1\u201d\u4e86\u7b2c 3 \u6bb5\uff0c\u4f46\u56e0\u4e3a\u4e2d\u95f4\u65ad\u4e86\uff0c\u4ecd\u7136\u53ea\u80fd\u786e\u8ba4\u5230\u7b2c 1 \u6bb5\u7ed3\u675f\u5904\uff0c\u6240\u4ee5\u786e\u8ba4\u53f7\u662f\uff1a<\/p>\n\n\n\n<p><code>ack = 700<\/code><\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u6700\u5bb9\u6613\u9519\u6210 <code>1400<\/code>\uff0c\u539f\u56e0\u5c31\u662f\u628a TCP \u7684\u786e\u8ba4\u7406\u89e3\u6210\u201c\u89c1\u5230\u4ec0\u4e48\u786e\u8ba4\u4ec0\u4e48\u201d\u3002\u5176\u5b9e\u4e0d\u662f\uff0cTCP \u9ed8\u8ba4\u662f\u7d2f\u8ba1\u786e\u8ba4\uff0c\u7f3a\u53e3\u4e0d\u8865\u4e0a\uff0c\u786e\u8ba4\u53f7\u5c31\u8fc7\u4e0d\u53bb\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. SYN \u548c FIN \u4e3a\u4ec0\u4e48\u4f1a\u6d88\u8017\u4e00\u4e2a\u5e8f\u53f7<\/h3>\n\n\n\n<p>\u505a <code>seq<\/code> \u9898\u65f6\uff0c\u8fd8\u6709\u4e00\u4e2a\u7279\u522b\u9ad8\u9891\u7684\u7ec6\u8282\uff1a<code>SYN<\/code> \u548c <code>FIN<\/code> \u90fd\u4f1a\u5404\u81ea\u6d88\u8017\u4e00\u4e2a\u5e8f\u53f7\uff0c\u5373\u4f7f\u5b83\u4eec\u672c\u8eab\u4e0d\u643a\u5e26\u666e\u901a\u6570\u636e\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u53d1\u9001\u4e00\u4e2a <code>SYN<\/code>\uff0c\u5e8f\u53f7\u4f1a\u5360\u6389 1<\/li>\n\n\n\n<li>\u53d1\u9001\u4e00\u4e2a <code>FIN<\/code>\uff0c\u5e8f\u53f7\u4e5f\u4f1a\u5360\u6389 1<\/li>\n\n\n\n<li>\u666e\u901a ACK \u5982\u679c\u4e0d\u643a\u5e26\u6570\u636e\uff0c\u5219\u4e0d\u6d88\u8017\u5e8f\u53f7<\/li>\n\n\n\n<li>\u666e\u901a\u6570\u636e\u6bb5\u6d88\u8017\u7684\u5e8f\u53f7\u6570 = \u6570\u636e\u5b57\u8282\u6570<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u51e1\u662f\u4e09\u6b21\u63e1\u624b\u3001\u56db\u6b21\u6325\u624b\u3001\u6c42\u67d0\u6bb5 <code>seq<\/code> \u6216 <code>ack<\/code> \u7684\u9898\uff0c\u4e00\u5b9a\u8981\u6ce8\u610f\uff1a<code>SYN<\/code> \u548c <code>FIN<\/code> \u8981\u4e0d\u8981\u7b97\u8fdb\u53bb\u3002\u5f88\u591a\u9898\u5c31\u662f\u4e13\u95e8\u5361\u8fd9 1 \u4e2a\u5e8f\u53f7\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001RTT \u4e0e\u8fde\u63a5\u5efa\u7acb \/ \u91ca\u653e\u65f6\u95f4\u9898\u600e\u4e48\u505a<\/h2>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u672c\u8d28\u4e0a\u662f\u201c\u65f6\u95f4\u8f74\u9898\u201d\u3002\u771f\u6b63\u89e3\u6cd5\u4e0d\u662f\u6b7b\u80cc\u6d41\u7a0b\u56fe\uff0c\u800c\u662f\u6309\u62a5\u6587\u53d1\u9001\u987a\u5e8f\uff0c\u628a\u5b83\u4eec\u4e00\u4e2a\u4e2a\u653e\u5230\u65f6\u95f4\u7ebf\u4e0a\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u5efa\u7acb\u8fde\u63a5\u7684\u65f6\u95f4\u5206\u6790\u601d\u8def<\/h3>\n\n\n\n<p>\u4e09\u6b21\u63e1\u624b\u7684\u6700\u57fa\u672c\u8fc7\u7a0b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5ba2\u6237\u7aef\u53d1 <code>SYN<\/code><\/li>\n\n\n\n<li>\u670d\u52a1\u5668\u56de <code>SYN + ACK<\/code><\/li>\n\n\n\n<li>\u5ba2\u6237\u7aef\u518d\u56de <code>ACK<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u5982\u679c\u53ea\u8003\u8651\u4f20\u64ad\u65f6\u5ef6\uff0c\u5ffd\u7565\u53d1\u9001\u65f6\u5ef6\uff0c\u5e76\u4e14\u9898\u76ee\u95ee\u201c\u4ec0\u4e48\u65f6\u5019\u5efa\u7acb\u6210\u529f\u201d\uff0c\u901a\u5e38\u8981\u6ce8\u610f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5ba2\u6237\u7aef\u89c6\u89d2\uff1a\u6536\u5230\u670d\u52a1\u5668\u7684 <code>SYN+ACK<\/code> \u5e76\u53d1\u51fa\u6700\u540e ACK \u540e\uff0c\u53ef\u4ee5\u8ba4\u4e3a\u8fde\u63a5\u5efa\u7acb\u5b8c\u6210<\/li>\n\n\n\n<li>\u670d\u52a1\u5668\u89c6\u89d2\uff1a\u6536\u5230\u5ba2\u6237\u7aef\u6700\u540e\u4e00\u4e2a ACK \u540e\uff0c\u624d\u77e5\u9053\u8fde\u63a5\u771f\u6b63\u5efa\u7acb\u5b8c\u6210<\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u6b64\u4e0d\u540c\u95ee\u6cd5\uff0c\u6700\u540e\u65f6\u95f4\u53ef\u80fd\u4e0d\u540c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u91ca\u653e\u8fde\u63a5\u7684\u65f6\u95f4\u5206\u6790\u601d\u8def<\/h3>\n\n\n\n<p>\u56db\u6b21\u6325\u624b\u7684\u6807\u51c6\u6d41\u7a0b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e3b\u52a8\u5173\u95ed\u65b9\u53d1 <code>FIN<\/code><\/li>\n\n\n\n<li>\u88ab\u52a8\u5173\u95ed\u65b9\u56de <code>ACK<\/code><\/li>\n\n\n\n<li>\u88ab\u52a8\u5173\u95ed\u65b9\u518d\u53d1 <code>FIN<\/code><\/li>\n\n\n\n<li>\u4e3b\u52a8\u5173\u95ed\u65b9\u56de\u6700\u540e <code>ACK<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u4f8b\u5982\u6709\u8fd9\u6837\u4e00\u9898\uff1a<\/p>\n\n\n\n<p>\u5df2\u77e5 RTT\uff0c\u5ba2\u6237\u7aef\u5728 <code>t<\/code> \u65f6\u523b\u8bf7\u6c42\u65ad\u5f00\u8fde\u63a5\uff0c\u95ee\u4ece <code>t<\/code> \u65f6\u523b\u8d77\u670d\u52a1\u5668\u6700\u77ed\u591a\u4e45\u91ca\u653e\u8fde\u63a5\u3002<\/p>\n\n\n\n<p>\u6700\u77ed\u60c5\u51b5\u662f\u670d\u52a1\u5668\u4e00\u6536\u5230\u5ba2\u6237\u7aef\u7684 <code>FIN<\/code>\uff0c\u5c31\u7acb\u523b\u56de ACK\uff0c\u5e76\u4e14\u7acb\u523b\u4e5f\u53d1\u51fa\u81ea\u5df1\u7684 <code>FIN<\/code>\u3002\u90a3\u4e48\u65f6\u95f4\u7ebf\u5c31\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>t<\/code>\uff1a\u5ba2\u6237\u7aef\u53d1 <code>FIN<\/code><\/li>\n\n\n\n<li><code>t + RTT\/2<\/code>\uff1a\u670d\u52a1\u5668\u6536\u5230 <code>FIN<\/code><\/li>\n\n\n\n<li><code>t + RTT<\/code>\uff1a\u5ba2\u6237\u7aef\u6536\u5230\u670d\u52a1\u5668\u7684 <code>FIN<\/code><\/li>\n\n\n\n<li><code>t + 1.5RTT<\/code>\uff1a\u670d\u52a1\u5668\u6536\u5230\u5ba2\u6237\u7aef\u5bf9\u8be5 <code>FIN<\/code> \u7684\u6700\u540e ACK<\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u6b64\u670d\u52a1\u5668\u6700\u77ed\u91ca\u653e\u8fde\u63a5\u65f6\u95f4\u662f\uff1a<\/p>\n\n\n\n<p><code>1.5RTT<\/code><\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u6700\u5bb9\u6613\u6df7\u6dc6\u7684\u70b9\u5728\u4e8e\uff0c\u628a\u201c\u670d\u52a1\u5668\u91ca\u653e\u8fde\u63a5\u65f6\u95f4\u201d\u548c\u201c\u5ba2\u6237\u7aef\u8fdb\u5165 TIME_WAIT \u7ee7\u7eed\u7b49\u5f85 2MSL\u201d\u6df7\u6210\u4e00\u56de\u4e8b\u3002\u9898\u76ee\u95ee\u8c01\uff0c\u5c31\u53ea\u770b\u8c01\u7684\u72b6\u6001\u53d8\u5316\uff0c\u4e0d\u8981\u628a\u53e6\u4e00\u7aef\u7684\u7b49\u5f85\u65f6\u95f4\u5f3a\u884c\u5e26\u8fdb\u6765\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001cwnd\u3001rwnd\u3001\u53d1\u9001\u7a97\u53e3\u8fd9\u4e09\u4e2a\u91cf\u600e\u4e48\u4e32\u8d77\u6765<\/h2>\n\n\n\n<p>\u8fd9\u90e8\u5206\u662f TCP \u6700\u5bb9\u6613\u6df7\u6dc6\u7684\u5730\u65b9\u3002\u5f88\u591a\u9898\u505a\u4e0d\u51fa\u6765\uff0c\u4e0d\u662f\u4e0d\u4f1a\u7b97\uff0c\u800c\u662f\u6839\u672c\u6ca1\u5206\u6e05\u201c\u8c01\u5728\u7ba1\u4ec0\u4e48\u201d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. rwnd\uff1a\u63a5\u6536\u65b9\u8bf4\u201c\u6211\u8fd8\u80fd\u6536\u591a\u5c11\u201d<\/h3>\n\n\n\n<p><code>rwnd<\/code> \u7531\u63a5\u6536\u65b9\u6839\u636e\u7f13\u5b58\u5269\u4f59\u7a7a\u95f4\u7ed9\u51fa\uff0c\u53cd\u6620\u7684\u662f\u63a5\u6536\u65b9\u201c\u5403\u4e0d\u5403\u5f97\u4e0b\u201d\u3002<\/p>\n\n\n\n<p>\u5982\u679c\u63a5\u6536\u65b9\u7f13\u5b58\u5f88\u5c0f\uff0c\u6216\u8005\u63a5\u6536\u65b9\u867d\u7136\u6536\u5230\u6570\u636e\u4f46\u8fdf\u8fdf\u4e0d\u53d6\u8d70\uff0c\u90a3\u4e48 <code>rwnd<\/code> \u5c31\u4f1a\u8d8a\u6765\u8d8a\u5c0f\uff0c\u6700\u540e\u53ef\u80fd\u628a\u53d1\u9001\u7a97\u53e3\u5361\u6b7b\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. cwnd\uff1a\u53d1\u9001\u65b9\u6839\u636e\u7f51\u7edc\u72b6\u51b5\u8bf4\u201c\u6211\u6700\u591a\u8be5\u53d1\u591a\u5c11\u201d<\/h3>\n\n\n\n<p><code>cwnd<\/code> \u662f\u53d1\u9001\u65b9\u6839\u636e\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\u52a8\u6001\u8c03\u6574\u7684\u7ed3\u679c\u3002\u7f51\u7edc\u72b6\u51b5\u597d\uff0c<code>cwnd<\/code> \u589e\u5927\uff1b\u4e00\u65e6\u53d1\u751f\u62e5\u585e\uff0c<code>cwnd<\/code> \u5c31\u8981\u7f29\u5c0f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u6700\u7ec8\u53d1\u591a\u5c11\uff1a\u770b\u66f4\u5c0f\u7684\u90a3\u4e2a<\/h3>\n\n\n\n<p>\u771f\u6b63\u80fd\u53d1\u591a\u5c11\u8981\u770b\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u4e00\u4e2a\u5f88\u5e38\u89c1\u7684\u51fa\u9898\u65b9\u5f0f\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5148\u8ba9 <code>cwnd<\/code> \u770b\u8d77\u6765\u5f88\u5927<\/li>\n\n\n\n<li>\u518d\u5728 ACK \u62a5\u6587\u91cc\u7ed9\u4e00\u4e2a\u5f88\u5c0f\u7684\u7a97\u53e3\u5b57\u6bb5<\/li>\n\n\n\n<li>\u95ee\u4f60\u201c\u4e0b\u4e00\u4e2a RTT \u6700\u591a\u80fd\u53d1\u591a\u5c11\u201d<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u79cd\u9898\u5982\u679c\u53ea\u987e\u7740\u7b97 <code>cwnd<\/code>\uff0c\u5c31\u4e00\u5b9a\u4f1a\u9519\u3002<\/p>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<p>\u5df2\u77e5 <code>ssthresh = 2KB<\/code>\uff0c<code>cwnd = 4KB<\/code>\uff0c\u7ecf\u8fc7\u4e00\u4e2a RTT \u540e\u6536\u5230\u4e86\u786e\u8ba4\uff0c\u800c\u786e\u8ba4\u62a5\u6587\u4e2d\u7684\u7a97\u53e3\u5b57\u6bb5\u503c\u662f <code>2KB<\/code>\u3002\u95ee\u4e0b\u4e00 RTT \u6700\u591a\u53d1\u9001\u591a\u5c11\u3002<\/p>\n\n\n\n<p>\u56e0\u4e3a <code>cwnd = 4KB &gt; ssthresh = 2KB<\/code>\uff0c\u6240\u4ee5\u73b0\u5728\u5904\u4e8e\u62e5\u585e\u907f\u514d\u9636\u6bb5\uff0c\u7ecf\u8fc7 1RTT \u540e\uff1a<\/p>\n\n\n\n<p><code>cwnd = 5KB<\/code><\/p>\n\n\n\n<p>\u4f46\u63a5\u6536\u65b9\u53ea\u7ed9\u51fa\uff1a<\/p>\n\n\n\n<p><code>rwnd = 2KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u771f\u6b63\u80fd\u53d1\u7684\u662f\uff1a<\/p>\n\n\n\n<p><code>swnd = min(5KB, 2KB) = 2KB<\/code><\/p>\n\n\n\n<p>\u7b54\u6848\u5c31\u4e0d\u662f <code>5KB<\/code>\uff0c\u800c\u662f <code>2KB<\/code>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u6162\u5f00\u59cb\u548c\u62e5\u585e\u907f\u514d\u662f\u600e\u4e48\u7b97\u7684<\/h2>\n\n\n\n<p>\u8fd9\u90e8\u5206\u5728\u9898\u76ee\u91cc\u51e0\u4e4e\u662f\u5fc5\u8003\uff0c\u800c\u4e14\u662f\u6240\u6709\u7a97\u53e3\u8ba1\u7b97\u9898\u7684\u57fa\u7840\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u8003\u7814\u9898\u4e2d\u7684\u9ed8\u8ba4\u7b80\u5316\u6a21\u578b<\/h3>\n\n\n\n<p>\u5982\u679c\u9898\u76ee\u6ca1\u6709\u7279\u522b\u8bf4\u660e\uff0c\u4e00\u822c\u6309\u8fd9\u79cd\u6a21\u578b\u505a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8fde\u63a5\u5efa\u7acb\u6210\u529f\u540e\uff0c\u521d\u59cb <code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u5f53 <code>cwnd &lt; ssthresh<\/code> \u65f6\uff0c\u5904\u4e8e\u6162\u5f00\u59cb<\/li>\n\n\n\n<li>\u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0c<code>cwnd<\/code> \u8fd1\u4f3c\u7ffb\u500d<\/li>\n\n\n\n<li>\u5f53 <code>cwnd &gt;= ssthresh<\/code> \u65f6\uff0c\u8f6c\u5165\u62e5\u585e\u907f\u514d<\/li>\n\n\n\n<li>\u62e5\u585e\u907f\u514d\u9636\u6bb5\uff0c\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0c<code>cwnd<\/code> \u589e\u52a0 <code>1 MSS<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u91cc\u7684\u201c\u6309 RTT \u7ffb\u500d\u201d\u201c\u6309 RTT \u52a0 1\u201d\u662f\u8003\u7814\u505a\u9898\u6a21\u578b\uff0c\u8db3\u591f\u5e94\u4ed8\u7edd\u5927\u591a\u6570\u9009\u62e9\u9898\u548c\u8ba1\u7b97\u9898\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u4e00\u4e2a\u6700\u5178\u578b\u7684\u589e\u957f\u4f8b\u5b50<\/h3>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>MSS = 2KB<\/code><\/li>\n\n\n\n<li><code>ssthresh = 16KB<\/code><\/li>\n\n\n\n<li><code>rwnd = 20KB<\/code><\/li>\n\n\n\n<li><code>RTT = 10ms<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u95ee\u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>20KB<\/code> \u9700\u8981\u591a\u4e45\u3002<\/p>\n\n\n\n<p>\u521d\u59cb\uff1a<\/p>\n\n\n\n<p><code>cwnd = 1 MSS = 2KB<\/code><\/p>\n\n\n\n<p>\u4e8e\u662f\u7a97\u53e3\u6f14\u5316\u4e3a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\uff1a<code>2KB<\/code><\/li>\n\n\n\n<li>1RTT \u540e\uff1a<code>4KB<\/code><\/li>\n\n\n\n<li>2RTT \u540e\uff1a<code>8KB<\/code><\/li>\n\n\n\n<li>3RTT \u540e\uff1a<code>16KB<\/code><\/li>\n\n\n\n<li>4RTT \u540e\uff1a<code>18KB<\/code><\/li>\n\n\n\n<li>5RTT \u540e\uff1a<code>20KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>20KB<\/code> \u9700\u8981\uff1a<\/p>\n\n\n\n<p><code>5RTT = 50ms<\/code><\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u6700\u5bb9\u6613\u9519\u6210 <code>40ms<\/code>\uff0c\u9519\u56e0\u5c31\u662f\u5fd8\u4e86\u5230\u8fbe\u95e8\u9650\u4e4b\u540e\u5df2\u7ecf\u4e0d\u518d\u7ffb\u500d\uff0c\u800c\u662f\u6539\u6210\u7ebf\u6027\u589e\u957f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u6162\u5f00\u59cb\u9636\u6bb5\u67d0\u4e00\u8f6e\u53d1\u4e86 k \u4e2a\u6bb5\uff0c\u4e0b\u4e00\u8f6e\u53d1\u591a\u5c11<\/h3>\n\n\n\n<p>\u5982\u679c\u9898\u76ee\u660e\u786e\u8bf4\u4ecd\u5728\u6162\u5f00\u59cb\u9636\u6bb5\uff0c\u90a3\u4e48\u7b54\u6848\u975e\u5e38\u76f4\u63a5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8fd9\u4e00 RTT \u53d1\u4e86 <code>k<\/code> \u4e2a\u6bb5<\/li>\n\n\n\n<li>\u4e0b\u4e00 RTT \u53d1 <code>2k<\/code> \u4e2a\u6bb5<\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u4e3a\u6162\u5f00\u59cb\u672c\u8d28\u5c31\u662f\u7a97\u53e3\u6307\u6570\u589e\u957f\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516d\u3001\u8d85\u65f6\u548c 3 \u4e2a\u5197\u4f59 ACK \u7684\u5904\u7406\u4e00\u5b9a\u8981\u5206\u5f00<\/h2>\n\n\n\n<p>\u8fd9\u4e00\u70b9\u662f TCP \u62e5\u585e\u63a7\u5236\u9898\u91cc\u6700\u5173\u952e\u7684\u5206\u6c34\u5cad\u3002\u5f88\u591a\u9898\u76ee\u6545\u610f\u628a\u201c\u8d85\u65f6\u201d\u548c\u201c3 \u4e2a\u5197\u4f59 ACK\u201d\u653e\u5728\u4e00\u8d77\u8003\uff0c\u5c31\u662f\u60f3\u770b\u662f\u5426\u771f\u7684\u5206\u6e05\u4e86\u4e24\u79cd\u60c5\u51b5\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u8d85\u65f6\u7684\u5904\u7406<\/h3>\n\n\n\n<p>\u5982\u679c\u53d1\u751f\u8d85\u65f6\uff0c\u8bf4\u660e\u7f51\u7edc\u62e5\u585e\u6bd4\u8f83\u4e25\u91cd\u3002\u8003\u7814\u91cc\u901a\u5e38\u6309\u4e0b\u9762\u5904\u7406\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = \u5f53\u524dcwnd \/ 2<\/code><\/li>\n\n\n\n<li><code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u91cd\u65b0\u8fdb\u5165\u6162\u5f00\u59cb<\/li>\n<\/ul>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<p><code>MSS = 1KB<\/code>\uff0c\u5f53 <code>cwnd = 34KB<\/code> \u65f6\u53d1\u751f\u8d85\u65f6\uff0c\u63a5\u4e0b\u6765 4RTT \u90fd\u6210\u529f\uff0c\u95ee 4RTT \u540e <code>cwnd<\/code> \u591a\u5927\u3002<\/p>\n\n\n\n<p>\u5148\u5904\u7406\u8d85\u65f6\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = 34 \/ 2 = 17KB<\/code><\/li>\n\n\n\n<li><code>cwnd = 1KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u7136\u540e\u6162\u5f00\u59cb\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>1RTT \u540e\uff1a<code>2KB<\/code><\/li>\n\n\n\n<li>2RTT \u540e\uff1a<code>4KB<\/code><\/li>\n\n\n\n<li>3RTT \u540e\uff1a<code>8KB<\/code><\/li>\n\n\n\n<li>4RTT \u540e\uff1a<code>16KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u662f\uff1a<\/p>\n\n\n\n<p><code>16KB<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. 3 \u4e2a\u5197\u4f59 ACK \u7684\u5904\u7406<\/h3>\n\n\n\n<p>\u5982\u679c\u6536\u5230 <code>3<\/code> \u4e2a\u5197\u4f59 ACK\uff0c\u8bf4\u660e\u7f51\u7edc\u8fd8\u6ca1\u6709\u5b8c\u5168\u963b\u585e\uff0c\u66f4\u53ef\u80fd\u662f\u4e2a\u522b\u62a5\u6587\u6bb5\u4e22\u5931\u3002\u8fd9\u65f6\u4e00\u822c\u6309 <strong>TCP Reno \u7684\u5feb\u91cd\u4f20 + \u5feb\u6062\u590d<\/strong> \u5904\u7406\u3002<\/p>\n\n\n\n<p>\u8003\u7814\u5e38\u89c1\u7b80\u5316\u7406\u89e3\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = \u5f53\u524dcwnd \/ 2<\/code><\/li>\n\n\n\n<li>\u4e0d\u50cf\u8d85\u65f6\u90a3\u6837\u628a <code>cwnd<\/code> \u76f4\u63a5\u6253\u56de <code>1 MSS<\/code><\/li>\n\n\n\n<li>\u4e4b\u540e\u6309\u5feb\u6062\u590d\u3001\u518d\u8f6c\u5165\u62e5\u585e\u907f\u514d\u53bb\u589e\u957f<\/li>\n<\/ul>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<p><code>MSS = 1KB<\/code>\uff0c<code>cwnd = 34KB<\/code> \u65f6\u6536\u5230 <code>3<\/code> \u4e2a\u5197\u4f59 ACK`\uff0c\u63a5\u4e0b\u6765 4RTT \u90fd\u6210\u529f\uff0c\u95ee\u6700\u540e\u7a97\u53e3\u591a\u5927\u3002<\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u5982\u679c\u6309 Reno \u7684\u5957\u8def\u6765\u505a\uff0c\u5e38\u89c1\u6807\u51c6\u7b54\u6848\u53d6\uff1a<\/p>\n\n\n\n<p><code>21KB<\/code><\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff0c\u8fd9\u9898\u548c\u201c\u8d85\u65f6\u201d\u90a3\u9898\u7684\u7b54\u6848\u4e0d\u4f1a\u4e00\u6837\u3002\u51fa\u9898\u4eba\u5c31\u662f\u5728\u8003\uff1a\u662f\u5426\u77e5\u9053\u201c\u5197\u4f59 ACK\u201d\u548c\u201c\u8d85\u65f6\u201d\u7684\u5904\u7406\u7b56\u7565\u4e0d\u540c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u505a\u9898\u65f6\u7684\u5feb\u901f\u8bc6\u522b\u6cd5<\/h3>\n\n\n\n<p>\u770b\u5230\u201c\u8d85\u65f6\u201d\u4e24\u4e2a\u5b57\uff0c\u7b2c\u4e00\u53cd\u5e94\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>cwnd -&gt; 1 MSS<\/code><\/p>\n\n\n\n<p>\u770b\u5230\u201c3 \u4e2a\u5197\u4f59 ACK\u201d\uff0c\u7b2c\u4e00\u53cd\u5e94\u5c31\u662f\uff1a<\/p>\n\n\n\n<p>\u201c\u4e0d\u56de\u5230 1\uff0c\u6309\u5feb\u91cd\u4f20 \/ \u5feb\u6062\u590d\u5904\u7406\u201d<\/p>\n\n\n\n<p>\u8fd9\u4e2a\u5206\u754c\u4e00\u5b9a\u8981\u517b\u6210\u6761\u4ef6\u53cd\u5c04\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e03\u3001\u53d1\u9001\u7a97\u53e3\u8fbe\u5230\u67d0\u4e2a\u503c\u7684\u9898\u600e\u4e48\u505a<\/h2>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u662f\u8003\u7814\u91cc\u7279\u522b\u559c\u6b22\u51fa\u7684\uff0c\u56e0\u4e3a\u5b83\u80fd\u540c\u65f6\u8003\u6162\u5f00\u59cb\u3001\u62e5\u585e\u907f\u514d\u3001RTT \u548c\u63a5\u6536\u7a97\u53e3\u3002<\/p>\n\n\n\n<p>\u505a\u6cd5\u4e00\u822c\u662f\u4e24\u6b65\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e00\u6b65\uff0c\u5148\u63a8 <code>cwnd<\/code> \u7684\u53d8\u5316\uff1b<br>\u7b2c\u4e8c\u6b65\uff0c\u518d\u548c <code>rwnd<\/code> \u6bd4\u8f83\uff0c\u770b\u771f\u6b63\u7684\u53d1\u9001\u7a97\u53e3 <code>swnd<\/code> \u662f\u591a\u5c11\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u63a5\u6536\u7a97\u53e3\u6052\u5b9a\u65f6<\/h3>\n\n\n\n<p>\u5982\u679c\u63a5\u6536\u65b9\u7f13\u5b58\u603b\u662f\u53ca\u65f6\u6e05\u7a7a\uff0c<code>rwnd<\/code> \u6052\u5b9a\uff0c\u90a3\u4e48\u9898\u76ee\u5c31\u57fa\u672c\u7b49\u4ef7\u4e8e\u5728\u95ee\uff1a<code>cwnd<\/code> \u4ec0\u4e48\u65f6\u5019\u957f\u5230\u90a3\u4e2a\u503c\u3002<\/p>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>rwnd = 24KB<\/code><\/li>\n\n\n\n<li><code>MSS = 2KB<\/code><\/li>\n\n\n\n<li><code>RTT = 10ms<\/code><\/li>\n\n\n\n<li>\u65e0\u62e5\u585e\uff0c\u53ea\u91c7\u7528\u6162\u5f00\u59cb<\/li>\n<\/ul>\n\n\n\n<p>\u95ee\u53d1\u9001\u65b9\u4f55\u65f6\u80fd\u53d1\u51fa\u7b2c\u4e00\u4e2a\u5b8c\u5168\u7a97\u53e3\uff0c\u4e5f\u5c31\u662f\u53d1\u9001\u7a97\u53e3\u8fbe\u5230 <code>24KB<\/code>\u3002<\/p>\n\n\n\n<p>\u521d\u59cb\uff1a<\/p>\n\n\n\n<p><code>cwnd = 2KB<\/code><\/p>\n\n\n\n<p>\u6162\u5f00\u59cb\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\uff1a<code>2KB<\/code><\/li>\n\n\n\n<li>1RTT \u540e\uff1a<code>4KB<\/code><\/li>\n\n\n\n<li>2RTT \u540e\uff1a<code>8KB<\/code><\/li>\n\n\n\n<li>3RTT \u540e\uff1a<code>16KB<\/code><\/li>\n\n\n\n<li>4RTT \u540e\uff1a<code>32KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u65f6\uff1a<\/p>\n\n\n\n<p><code>swnd = min(32KB, 24KB) = 24KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>24KB<\/code> \u7684\u65f6\u95f4\u662f\uff1a<\/p>\n\n\n\n<p><code>40ms<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u63a5\u6536\u7a97\u53e3\u4e0d\u65ad\u7f29\u5c0f\u65f6<\/h3>\n\n\n\n<p>\u5982\u679c\u63a5\u6536\u65b9\u7f13\u5b58\u53ea\u8fdb\u4e0d\u51fa\uff0c\u90a3\u4e48 <code>rwnd<\/code> \u4f1a\u8d8a\u6765\u8d8a\u5c0f\u3002\u8fd9\u7c7b\u9898\u770b\u8d77\u6765\u66f4\u4e71\uff0c\u4f46\u5b9e\u9645\u4e0a\u53ea\u8981\u5217\u4e00\u5f20\u8868\u5c31\u5f88\u6e05\u695a\u3002<\/p>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>MSS = 1KB<\/code><\/li>\n\n\n\n<li><code>RTT = 3ms<\/code><\/li>\n\n\n\n<li>\u63a5\u6536\u7f13\u5b58\u603b\u5927\u5c0f <code>16KB<\/code><\/li>\n\n\n\n<li>\u63a5\u6536\u65b9\u7f13\u5b58\u53ea\u6709\u6570\u636e\u5b58\u5165\uff0c\u6ca1\u6709\u6570\u636e\u53d6\u51fa<\/li>\n\n\n\n<li>\u65e0\u62e5\u585e<\/li>\n<\/ul>\n\n\n\n<p>\u8fde\u63a5\u5efa\u7acb\u6210\u529f\u540e\uff0c\u6309\u8003\u7814\u9ed8\u8ba4\uff0c\u521d\u59cb <code>cwnd = 1KB<\/code>\u3002<\/p>\n\n\n\n<p>\u7a97\u53e3\u6f14\u5316\u8868\u5982\u4e0b\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u65f6\u523b<\/th><th>\u5df2\u7d2f\u8ba1\u6536\u5230\u6570\u636e<\/th><th>\u5269\u4f59\u63a5\u6536\u7a97\u53e3 rwnd<\/th><th>\u62e5\u585e\u7a97\u53e3 cwnd<\/th><th>\u53d1\u9001\u7a97\u53e3 swnd<\/th><\/tr><\/thead><tbody><tr><td>\u5efa\u7acb\u540e\u7acb\u5373<\/td><td>0KB<\/td><td>16KB<\/td><td>1KB<\/td><td>1KB<\/td><\/tr><tr><td>3ms<\/td><td>1KB<\/td><td>15KB<\/td><td>2KB<\/td><td>2KB<\/td><\/tr><tr><td>6ms<\/td><td>3KB<\/td><td>13KB<\/td><td>4KB<\/td><td>4KB<\/td><\/tr><tr><td>9ms<\/td><td>7KB<\/td><td>9KB<\/td><td>8KB<\/td><td>8KB<\/td><\/tr><tr><td>12ms<\/td><td>15KB<\/td><td>1KB<\/td><td>16KB<\/td><td>1KB<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\u4ece\u8fd9\u5f20\u8868\u5c31\u80fd\u4e00\u773c\u770b\u51fa\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>4KB<\/code>\uff1a\u5728 <code>6ms<\/code>\uff0c\u6b64\u65f6\u63a5\u6536\u65b9\u53ef\u7528\u7a7a\u95f4 <code>13KB<\/code><\/li>\n\n\n\n<li>\u53d1\u9001\u7a97\u53e3\u7b2c\u4e00\u6b21\u8fbe\u5230 <code>8KB<\/code>\uff1a\u5728 <code>9ms<\/code>\uff0c\u6b64\u65f6\u63a5\u6536\u65b9\u53ef\u7528\u7a7a\u95f4 <code>9KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u79cd\u9898\u5982\u679c\u4e0d\u5217\u8868\uff0c\u8111\u5b50\u91cc\u5f88\u5bb9\u6613\u4e71\uff1b\u4e00\u65e6\u5217\u8868\uff0c\u5c31\u51e0\u4e4e\u4e0d\u4f1a\u9519\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516b\u3001RTT\u3001\u7a97\u53e3\u3001\u5e8f\u53f7\u9898\u7684\u7edf\u4e00\u505a\u9898\u6a21\u677f<\/h2>\n\n\n\n<p>\u505a TCP \u9898\u65f6\uff0c\u771f\u6b63\u6709\u7528\u7684\u4e0d\u662f\u80cc\u5f88\u591a\u96f6\u788e\u7ed3\u8bba\uff0c\u800c\u662f\u5f62\u6210\u56fa\u5b9a\u6a21\u677f\u3002\u53ea\u8981\u770b\u5230\u9898\u76ee\uff0c\u5c31\u77e5\u9053\u5148\u4ece\u54ea\u51e0\u6b65\u4e0b\u624b\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u5982\u679c\u9898\u76ee\u5728\u95ee seq \/ ack<\/h3>\n\n\n\n<p>\u7b2c\u4e00\u6b65\uff0c\u5148\u5224\u65ad <code>seq<\/code> \u662f\u54ea\u4e2a\u6bb5\u201c\u6570\u636e\u90e8\u5206\u7b2c\u4e00\u4e2a\u5b57\u8282\u201d\u7684\u7f16\u53f7\u3002<br>\u7b2c\u4e8c\u6b65\uff0c\u6839\u636e\u6570\u636e\u957f\u5ea6\u63a8\u51fa\u5404\u6bb5\u8986\u76d6\u8303\u56f4\u3002<br>\u7b2c\u4e09\u6b65\uff0c\u82e5\u6709\u4e22\u5931\u3001\u4e71\u5e8f\uff0c\u4f18\u5148\u6309\u201c\u7d2f\u8ba1\u786e\u8ba4\u201d\u5904\u7406\u3002<br>\u7b2c\u56db\u6b65\uff0c\u786e\u8ba4\u662f\u5426\u6709 <code>SYN<\/code>\u3001<code>FIN<\/code>\uff0c\u5b83\u4eec\u662f\u5426\u8981\u5404\u5360 1 \u4e2a\u5e8f\u53f7\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u5982\u679c\u9898\u76ee\u5728\u95ee\u6325\u624b\u3001\u5efa\u8fde\u65f6\u95f4<\/h3>\n\n\n\n<p>\u7b2c\u4e00\u6b65\uff0c\u5148\u628a <code>RTT<\/code> \u62c6\u6210 <code>RTT\/2<\/code>\u3002<br>\u7b2c\u4e8c\u6b65\uff0c\u5728\u7eb8\u4e0a\u753b\u65f6\u95f4\u7ebf\u3002<br>\u7b2c\u4e09\u6b65\uff0c\u6309\u201c\u8c01\u53d1\u51fa\u3001\u8c01\u6536\u5230\u3001\u518d\u7531\u8c01\u8fd4\u56de\u201d\u7684\u987a\u5e8f\u9010\u4e2a\u63a8\u3002<br>\u7b2c\u56db\u6b65\uff0c\u53ea\u56de\u7b54\u9898\u76ee\u95ee\u7684\u90a3\u4e00\u7aef\uff0c\u4e0d\u8981\u628a\u53e6\u4e00\u7aef\u7684\u7b49\u5f85\u72b6\u6001\u4e71\u5e26\u8fdb\u53bb\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u5982\u679c\u9898\u76ee\u5728\u95ee cwnd \u53d8\u5316<\/h3>\n\n\n\n<p>\u5148\u770b\u9898\u76ee\u7ed9\u7684\u662f\u54ea\u79cd\u89e6\u53d1\u6761\u4ef6\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u82e5\u662f\u201c\u65e0\u62e5\u585e \/ \u6b63\u5e38\u589e\u957f\u201d \u2192 \u6162\u5f00\u59cb + \u62e5\u585e\u907f\u514d<\/li>\n\n\n\n<li>\u82e5\u662f\u201c\u8d85\u65f6\u201d \u2192 <code>ssthresh = cwnd\/2<\/code>\uff0c<code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u82e5\u662f\u201c3 \u4e2a\u5197\u4f59 ACK\u201d \u2192 \u5feb\u91cd\u4f20 \/ \u5feb\u6062\u590d\u601d\u8def<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">4. \u5982\u679c\u9898\u76ee\u5728\u95ee\u771f\u6b63\u80fd\u53d1\u591a\u5c11<\/h3>\n\n\n\n<p>\u6700\u540e\u4e00\u6b65\u7edf\u4e00\u505a\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u53ea\u8981\u9898\u76ee\u7ed9\u4e86\u63a5\u6536\u7a97\u53e3\uff0c\u5c31\u5fc5\u987b\u505a\u8fd9\u4e00\u6b65\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e5d\u3001\u6700\u5bb9\u6613\u51fa\u9519\u7684\u5178\u578b\u9677\u9631\u6e05\u5355<\/h2>\n\n\n\n<p>TCP \u8fd9\u4e00\u7ae0\u9898\u76ee\u5e76\u4e0d\u96be\uff0c\u4f46\u5751\u5f88\u591a\uff0c\u5c24\u5176\u662f\u9009\u62e9\u9898\uff0c\u7ecf\u5e38\u5c31\u662f\u62ff\u8fd9\u4e9b\u4e60\u60ef\u6027\u9519\u8bef\u6765\u8bbe\u9677\u9631\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u628a ack \u5f53\u6210\u201c\u6700\u540e\u6536\u5230\u7684\u5b57\u8282\u53f7\u201d<\/h3>\n\n\n\n<p>\u8fd9\u662f\u6700\u5e38\u89c1\u9519\u8bef\u3002<br>\u6b63\u786e\u7406\u89e3\u5e94\u662f\uff1a<\/p>\n\n\n\n<p><code>ack = \u4e0b\u4e00\u4e2a\u671f\u671b\u6536\u5230\u7684\u5b57\u8282\u5e8f\u53f7<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u5fd8\u8bb0\u7d2f\u8ba1\u786e\u8ba4\u4e0d\u80fd\u8de8\u8fc7\u7f3a\u53e3<\/h3>\n\n\n\n<p>\u540e\u9762\u7684\u6bb5\u5373\u4f7f\u6536\u5230\u4e86\uff0c\u53ea\u8981\u4e2d\u95f4\u4e22\u4e86\u4e00\u6bb5\uff0c\u786e\u8ba4\u53f7\u5c31\u4e0d\u80fd\u8df3\u8fc7\u53bb\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u5fd8\u8bb0 SYN \u548c FIN \u4e5f\u8981\u6d88\u8017\u4e00\u4e2a\u5e8f\u53f7<\/h3>\n\n\n\n<p>\u8fd9\u5728\u63e1\u624b\u3001\u6325\u624b\u9898\u91cc\u975e\u5e38\u9ad8\u9891\u3002\u666e\u901a\u4e0d\u5e26\u6570\u636e\u7684 ACK \u4e0d\u6d88\u8017\u5e8f\u53f7\uff0c\u4f46 <code>SYN<\/code> \u548c <code>FIN<\/code> \u4f1a\u5404\u81ea\u5360\u6389 1 \u4e2a\u5e8f\u53f7\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4. \u628a cwnd \u76f4\u63a5\u5f53\u6210\u53d1\u9001\u7a97\u53e3<\/h3>\n\n\n\n<p>\u53ea\u6709\u5728 <code>rwnd<\/code> \u8db3\u591f\u5927\u65f6\uff0c\u624d\u6709\u53ef\u80fd\u201c\u53d1\u9001\u7a97\u53e3 = cwnd\u201d\u3002<br>\u4e00\u822c\u60c5\u51b5\u4e0b\u5fc5\u987b\u6bd4\u8f83\uff1a<\/p>\n\n\n\n<p><code>swnd = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">5. \u5230\u4e86 ssthresh \u4e4b\u540e\u8fd8\u7ee7\u7eed\u6309\u7ffb\u500d\u7b97<\/h3>\n\n\n\n<p>\u8fd9\u662f\u6162\u5f00\u59cb \/ \u62e5\u585e\u907f\u514d\u6df7\u6dc6\u5bfc\u81f4\u7684\u5178\u578b\u9519\u8bef\u3002<br>\u5230\u8fbe\u95e8\u9650\u4e4b\u540e\uff0c\u901a\u5e38\u5c31\u8be5\u6539\u6210\u6bcf RTT \u589e\u52a0 <code>1 MSS<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">6. \u628a 3 \u4e2a\u5197\u4f59 ACK \u548c\u8d85\u65f6\u5f53\u6210\u540c\u4e00\u79cd\u60c5\u51b5<\/h3>\n\n\n\n<p>\u8fd9\u4e24\u4e2a\u7684\u5904\u7406\u5f3a\u5ea6\u4e0d\u4e00\u6837\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8d85\u65f6\uff1a\u8bf4\u660e\u66f4\u4e25\u91cd\uff0c<code>cwnd<\/code> \u56de\u5230 <code>1 MSS<\/code><\/li>\n\n\n\n<li>3 \u4e2a\u5197\u4f59 ACK\uff1a\u4e00\u822c\u4e0d\u6253\u56de <code>1 MSS<\/code><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">7. \u65f6\u95f4\u9898\u91cc\u628a TIME_WAIT \u786c\u5e26\u8fdb\u670d\u52a1\u5668\u91ca\u653e\u65f6\u95f4<\/h3>\n\n\n\n<p>\u95ee\u670d\u52a1\u5668\u4ec0\u4e48\u65f6\u5019\u91ca\u653e\uff0c\u5c31\u53ea\u770b\u670d\u52a1\u5668\u4ec0\u4e48\u65f6\u5019\u6536\u5230\u6700\u540e ACK\u3002<br>\u5ba2\u6237\u7aef\u4e4b\u540e\u8fd8\u8981\u4e0d\u8981\u7b49 2MSL\uff0c\u90a3\u662f\u53e6\u4e00\u56de\u4e8b\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u5341\u3001\u628a\u524d\u9762\u505a\u8fc7\u7684\u5178\u578b\u4f8b\u9898\u7edf\u4e00\u5f52\u7c7b<\/h2>\n\n\n\n<p>\u4e3a\u4e86\u540e\u7eed\u590d\u4e60\u65b9\u4fbf\uff0c\u53ef\u4ee5\u628a\u524d\u9762\u51e0\u9053\u9898\u6309\u9898\u578b\u76f4\u63a5\u5f52\u7c7b\u8bb0\u5fc6\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. RTT \/ \u6325\u624b\u65f6\u95f4\u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a\u5ba2\u6237\u7aef\u5728 <code>t<\/code> \u65f6\u523b\u8bf7\u6c42\u65ad\u5f00\u8fde\u63a5\uff0c\u670d\u52a1\u5668\u6700\u77ed\u591a\u4e45\u91ca\u653e\u8fde\u63a5\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br><code>1.5RTT<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br><code>FIN<\/code>\u3001<code>ACK<\/code>\u3001\u6700\u540e\u786e\u8ba4\u3001\u5355\u7a0b <code>RTT\/2<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. seq \/ ack \u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a3 \u4e2a\u8fde\u7eed\u6bb5\u957f\u5ea6\u5206\u522b\u4e3a <code>200B\u3001300B\u3001400B<\/code>\uff0c\u7b2c 3 \u6bb5 <code>seq = 1000<\/code>\uff0c\u53ea\u6536\u5230\u7b2c 1 \u6bb5\u548c\u7b2c 3 \u6bb5\uff0c\u95ee\u786e\u8ba4\u53f7\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br><code>ack = 700<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br>\u7d2f\u8ba1\u786e\u8ba4\u3001\u7f3a\u53e3\u4e0d\u80fd\u8d8a\u8fc7\u3001\u786e\u8ba4\u5230\u7b2c\u4e00\u4e2a\u4e22\u5931\u5b57\u8282<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u8d85\u65f6\u540e\u7a97\u53e3\u53d8\u5316\u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a<code>cwnd = 34KB<\/code> \u65f6\u8d85\u65f6\uff0c\u540e\u7eed <code>4RTT<\/code> \u5747\u6210\u529f\uff0c\u95ee <code>cwnd<\/code>\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br><code>16KB<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br><code>ssthresh = 17KB<\/code>\uff0c<code>cwnd = 1KB<\/code>\uff0c\u7136\u540e <code>1 -&gt; 2 -&gt; 4 -&gt; 8 -&gt; 16<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4. \u5197\u4f59 ACK \u540e\u7a97\u53e3\u53d8\u5316\u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a<code>cwnd = 34KB<\/code> \u65f6\u6536\u5230 <code>3<\/code> \u4e2a\u5197\u4f59 ACK\uff0c\u540e\u7eed <code>4RTT<\/code> \u6210\u529f\uff0c\u95ee <code>cwnd<\/code>\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br>\u6309\u5e38\u89c4\u8003\u7814\u601d\u8def\uff0c\u53d6 <code>21KB<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br>\u5feb\u91cd\u4f20\u3001\u5feb\u6062\u590d\u3001Reno\u3001\u4e0d\u56de\u5230 <code>1 MSS<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">5. \u63a5\u6536\u7a97\u53e3\u9650\u5236\u53d1\u9001\u7a97\u53e3\u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a<code>cwnd<\/code> \u7b97\u51fa\u6765\u6bd4 <code>rwnd<\/code> \u5927\uff0c\u95ee\u4e0b\u4e00\u4e2a RTT \u6700\u591a\u80fd\u53d1\u591a\u5c11\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br>\u5fc5\u987b\u7528 <code>min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br>\u7a97\u53e3\u5b57\u6bb5\u3001\u63a5\u6536\u65b9\u7f13\u5b58\u9650\u5236\u3001\u4e0d\u8981\u53ea\u76ef\u7740 <code>cwnd<\/code><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">6. \u6162\u5f00\u59cb\u8fbe\u5230\u67d0\u7a97\u53e3\u503c\u9898<\/h3>\n\n\n\n<p>\u5178\u578b\u9898\uff1a<code>MSS = 2KB<\/code>\uff0c<code>rwnd = 24KB<\/code>\uff0c<code>RTT = 10ms<\/code>\uff0c\u65e0\u62e5\u585e\uff0c\u95ee\u4f55\u65f6\u8fbe\u5230\u7b2c\u4e00\u4e2a\u5b8c\u6574\u7a97\u53e3\u3002<\/p>\n\n\n\n<p>\u7ed3\u8bba\uff1a<br><code>40ms<\/code><\/p>\n\n\n\n<p>\u5173\u952e\u8bcd\uff1a<br>\u6162\u5f00\u59cb\u7ffb\u500d\uff0c<code>2 -&gt; 4 -&gt; 8 -&gt; 16 -&gt; 32<\/code>\uff0c\u53d1\u9001\u7a97\u53e3\u8fbe <code>24KB<\/code><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u5341\u4e00\u3001\u6700\u540e\u6574\u7406\u6210\u4e00\u4e2a\u8003\u573a\u901f\u5224\u8868<\/h2>\n\n\n\n<p>\u8fd9\u90e8\u5206\u6700\u9002\u5408\u8003\u524d\u8fc7\u4e00\u904d\u3002<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u9898\u76ee\u95ee\u6cd5<\/th><th>\u7b2c\u4e00\u53cd\u5e94<\/th><th>\u6838\u5fc3\u516c\u5f0f \/ \u89c4\u5219<\/th><\/tr><\/thead><tbody><tr><td>\u6c42\u67d0\u6bb5 seq<\/td><td>\u770b\u5b83\u524d\u9762\u6709\u591a\u5c11\u5b57\u8282\u6570\u636e<\/td><td><code>\u540e\u6bb5seq = \u524d\u6bb5seq + \u524d\u6bb5\u6570\u636e\u957f\u5ea6<\/code><\/td><\/tr><tr><td>\u6c42 ack<\/td><td>\u770b\u6309\u5e8f\u8fde\u7eed\u6536\u5230\u4e86\u54ea\u91cc<\/td><td><code>ack = \u4e0b\u4e00\u4e2a\u671f\u671b\u5b57\u8282\u53f7<\/code><\/td><\/tr><tr><td>\u4e2d\u95f4\u4e22\u5931\u3001\u540e\u6bb5\u5148\u5230<\/td><td>\u6309\u7d2f\u8ba1\u786e\u8ba4\u5904\u7406<\/td><td>\u4e0d\u80fd\u8de8\u8fc7\u7f3a\u53e3\u786e\u8ba4<\/td><\/tr><tr><td>\u95ee\u63e1\u624b\/\u6325\u624b\u65f6\u95f4<\/td><td>\u5148\u62c6 <code>RTT\/2<\/code><\/td><td>\u753b\u65f6\u95f4\u7ebf\u9010\u6bb5\u63a8<\/td><\/tr><tr><td>\u95ee\u8d85\u65f6\u540e\u7a97\u53e3<\/td><td>\u5148\u51cf\u534a\u518d\u56de 1<\/td><td><code>ssthresh = cwnd\/2<\/code>\uff0c<code>cwnd = 1 MSS<\/code><\/td><\/tr><tr><td>\u95ee 3 \u4e2a\u5197\u4f59 ACK \u540e\u7a97\u53e3<\/td><td>\u5feb\u91cd\u4f20 \/ \u5feb\u6062\u590d<\/td><td>\u4e0d\u6309\u8d85\u65f6\u5904\u7406<\/td><\/tr><tr><td>\u95ee\u4e0b\u8f6e\u6162\u5f00\u59cb\u53d1\u591a\u5c11<\/td><td>\u76f4\u63a5\u7ffb\u500d<\/td><td><code>k -&gt; 2k<\/code><\/td><\/tr><tr><td>\u95ee\u53d1\u9001\u7a97\u53e3<\/td><td>\u6700\u540e\u6bd4\u4e00\u6b21<\/td><td><code>swnd = min(cwnd, rwnd)<\/code><\/td><\/tr><tr><td>\u95ee\u4f55\u65f6\u8fbe\u5230\u67d0\u7a97\u53e3\u503c<\/td><td>\u5148\u63a8 <code>cwnd<\/code>\uff0c\u518d\u770b <code>rwnd<\/code><\/td><td>\u5148\u589e\u957f\uff0c\u518d\u9650\u5e45<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u5341\u4e8c\u3001\u8fd9\u4e00\u7ae0\u771f\u6b63\u5e94\u8be5\u5efa\u7acb\u8d77\u6765\u7684\u611f\u89c9<\/h2>\n\n\n\n<p>TCP \u8fd9\u4e00\u7ae0\u6700\u5173\u952e\u7684\u4e0d\u662f\u6b7b\u8bb0\u5f88\u591a\u96f6\u788e\u5b9a\u4e49\uff0c\u800c\u662f\u8111\u5b50\u91cc\u8981\u6709\u4e00\u6761\u975e\u5e38\u6e05\u695a\u7684\u4e3b\u7ebf\uff1a<\/p>\n\n\n\n<p><code>seq \/ ack<\/code> \u89e3\u51b3\u7684\u662f\u201c\u5b57\u8282\u6d41\u7f16\u53f7\u4e0e\u786e\u8ba4\u201d\u7684\u95ee\u9898\uff1b<br><code>RTT<\/code> \u89e3\u51b3\u7684\u662f\u201c\u62a5\u6587\u5f80\u8fd4\u65f6\u95f4\u600e\u4e48\u63a8\u201d\u7684\u95ee\u9898\uff1b<br><code>rwnd<\/code> \u89e3\u51b3\u7684\u662f\u201c\u63a5\u6536\u65b9\u5403\u4e0d\u5403\u5f97\u4e0b\u201d\u7684\u95ee\u9898\uff1b<br><code>cwnd<\/code> \u89e3\u51b3\u7684\u662f\u201c\u7f51\u7edc\u80fd\u4e0d\u80fd\u627f\u53d7\u201d\u7684\u95ee\u9898\uff1b<br>\u771f\u6b63\u53d1\u591a\u5c11\uff0c\u6700\u7ec8\u90fd\u843d\u5230\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u800c\u4e00\u65e6\u7f51\u7edc\u51fa\u95ee\u9898\uff0c\u8fd8\u8981\u7ee7\u7eed\u5206\u6e05\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8d85\u65f6\uff1a\u5904\u7406\u66f4\u72e0<\/li>\n\n\n\n<li>3 \u4e2a\u5197\u4f59 ACK\uff1a\u5904\u7406\u8f83\u8f7b<\/li>\n<\/ul>\n\n\n\n<p>\u53ea\u8981\u8fd9\u4e00\u6761\u4e3b\u7ebf\u771f\u6b63\u6253\u901a\uff0c\u540e\u9762\u65e0\u8bba\u9898\u76ee\u600e\u4e48\u6362\u540d\u5b57\u3001\u6362\u6570\u5b57\u3001\u6362\u53d9\u8ff0\u65b9\u5f0f\uff0c\u672c\u8d28\u4e0a\u90fd\u53ea\u662f\u628a\u8fd9\u51e0\u4e2a\u91cf\u91cd\u65b0\u6392\u5217\u7ec4\u5408\u4e00\u4e0b\u800c\u5df2\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u5341\u4e09\u3001\u9002\u5408\u6700\u540e\u590d\u4e60\u65f6\u76f4\u63a5\u8bb0\u4f4f\u7684\u7ed3\u8bba<\/h2>\n\n\n\n<p>\u6700\u540e\u53ef\u4ee5\u628a\u8fd9\u4e00\u90e8\u5206\u538b\u7f29\u6210\u51e0\u53e5\u6700\u5173\u952e\u7684\u8bdd\uff0c\u505a\u9898\u524d\u5148\u5728\u8111\u5b50\u91cc\u8fc7\u4e00\u904d\uff1a<\/p>\n\n\n\n<p><code>seq<\/code> \u770b\u672c\u6bb5\u7b2c\u4e00\u4e2a\u5b57\u8282\u3002<br><code>ack<\/code> \u770b\u4e0b\u4e00\u4e2a\u671f\u5f85\u5b57\u8282\u3002<br>TCP \u9ed8\u8ba4\u7d2f\u8ba1\u786e\u8ba4\uff0c\u4e2d\u95f4\u7f3a\u5931\u4e0d\u80fd\u8df3\u786e\u8ba4\u3002<br><code>SYN<\/code> \u548c <code>FIN<\/code> \u5404\u6d88\u8017 1 \u4e2a\u5e8f\u53f7\u3002<br><code>\u5355\u7a0b\u4f20\u64ad\u65f6\u5ef6 = RTT\/2<\/code>\u3002<br>\u53d1\u9001\u7a97\u53e3 <code>swnd = min(cwnd, rwnd)<\/code>\u3002<br>\u6162\u5f00\u59cb\u6309 RTT \u7ffb\u500d\uff0c\u62e5\u585e\u907f\u514d\u6309 RTT \u52a0 1 MSS\u3002<br>\u8d85\u65f6\u56de\u5230 <code>1 MSS<\/code>\uff0c3 \u4e2a\u5197\u4f59 ACK \u4e0d\u6309\u8d85\u65f6\u5904\u7406\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><div class='fancybox-wrapper lazyload-container-unload' data-fancybox='post-images' href='http:\/\/www.preluna.xyz\/wp-content\/uploads\/2026\/04\/4046-1024x768.jpg'><img class=\"lazyload lazyload-style-1\" src=\"data:image\/svg+xml;base64,PCEtLUFyZ29uTG9hZGluZy0tPgo8c3ZnIHdpZHRoPSIxIiBoZWlnaHQ9IjEiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgc3Ryb2tlPSIjZmZmZmZmMDAiPjxnPjwvZz4KPC9zdmc+\"  loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" data-original=\"http:\/\/www.preluna.xyz\/wp-content\/uploads\/2026\/04\/4046-1024x768.jpg\" src=\"data:image\/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB\/AAffA0nNPuCLAAAAAElFTkSuQmCC\" alt=\"\" class=\"wp-image-2084\"  sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/div><\/figure>\n\n\n\n<p>\u4e0b\u9762\u628a\u7b2c 40\uff5e46 \u9898\u9010\u9898\u89e3\u6790\u3002\u8fd9\u91cc\u8fd9\u4e00\u7ec4\u9898\u51e0\u4e4e\u90fd\u5728\u8003 TCP \u7684\u51e0\u4e2a\u9ad8\u9891\u6838\u5fc3\u70b9\uff1a<code>seq\/ack<\/code> \u7684\u8ba1\u7b97\u3001\u7d2f\u8ba1\u786e\u8ba4\u3001SYN \u662f\u5426\u5360 1 \u4e2a\u5e8f\u53f7\u3001\u53d1\u9001\u7a97\u53e3\u53d7 <code>min(cwnd, rwnd)<\/code> \u9650\u5236\u3001\u8d85\u65f6\u540e\u7684\u62e5\u585e\u7a97\u53e3\u53d8\u5316\u3002<br>\u8fd9\u7c7b\u9898\u7684\u5171\u540c\u7279\u70b9\u662f\uff1a\u9898\u5e72\u4e0d\u957f\uff0c\u4f46\u5f88\u5bb9\u6613\u56e0\u4e3a\u201c\u5c11\u770b\u4e00\u4e2a\u6761\u4ef6\u201d\u6216\u8005\u201c\u628a\u51e0\u4e2a\u7a97\u53e3\u6df7\u5728\u4e00\u8d77\u201d\u800c\u505a\u9519\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">40. \u6162\u5f00\u59cb\u5230\u53d1\u9001\u7a97\u53e3\u8fbe\u5230 8KB<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>B\uff0e9ms\uff0c9KB<\/strong><\/p>\n\n\n\n<p>\u8fd9\u9898\u8003\u7684\u662f TCP \u5efa\u8fde\u540e\uff0c\u53d1\u9001\u65b9\u5728<strong>\u6162\u5f00\u59cb<\/strong>\u9636\u6bb5\u7a97\u53e3\u5982\u4f55\u589e\u957f\uff0c\u4ee5\u53ca\u63a5\u6536\u7f13\u5b58\u7a7a\u95f4\u5982\u4f55\u540c\u6b65\u51cf\u5c11\u3002<\/p>\n\n\n\n<p>\u9898\u5e72\u7ed9\u51fa\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>MSS = 1KB<\/li>\n\n\n\n<li>RTT = 3ms<\/li>\n\n\n\n<li>\u4e59\u63a5\u6536\u7f13\u5b58 = 16KB<\/li>\n\n\n\n<li>\u4e59\u53ea\u63a5\u6536\u6570\u636e\uff0c\u4e0d\u53d6\u8d70\u6570\u636e<\/li>\n\n\n\n<li>\u95ee\uff1a\u4ece\u8fde\u63a5\u5efa\u7acb\u6210\u529f\u5230\u7532\u7684\u53d1\u9001\u7a97\u53e3\u8fbe\u5230 8KB\uff0c\u6700\u5c11\u7ecf\u8fc7\u591a\u4e45\uff1f\u6b64\u65f6\u4e59\u63a5\u6536\u7f13\u5b58\u5269\u4f59\u591a\u5c11\u53ef\u7528\u7a7a\u95f4\uff1f<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u91cc\u6309\u8003\u7814\u9898\u7684\u9ed8\u8ba4\u6a21\u578b\uff0c\u5efa\u8fde\u6210\u529f\u540e\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521d\u59cb\u62e5\u585e\u7a97\u53e3 <code>cwnd = 1 MSS = 1KB<\/code><\/li>\n\n\n\n<li>\u6162\u5f00\u59cb\u9636\u6bb5\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0c<code>cwnd<\/code> \u7ffb\u500d<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7a97\u53e3\u53d8\u5316\u8fc7\u7a0b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u521a\u5efa\u8fde\u6210\u529f\uff1a<code>cwnd = 1KB<\/code><\/li>\n\n\n\n<li>1 \u4e2a RTT \u540e\uff1a<code>cwnd = 2KB<\/code><\/li>\n\n\n\n<li>2 \u4e2a RTT \u540e\uff1a<code>cwnd = 4KB<\/code><\/li>\n\n\n\n<li>3 \u4e2a RTT \u540e\uff1a<code>cwnd = 8KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u6b64\u6700\u5c11\u65f6\u95f4\u662f\uff1a<\/p>\n\n\n\n<p><code>3 \u00d7 RTT = 3 \u00d7 3ms = 9ms<\/code><\/p>\n\n\n\n<p>\u518d\u770b\u6b64\u65f6\u4e59\u5df2\u7ecf\u6536\u5230\u4e86\u591a\u5c11\u6570\u636e\u3002<\/p>\n\n\n\n<p>\u6162\u5f00\u59cb\u53d1\u9001\u7684\u6570\u636e\u8f6e\u6b21\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u8f6e\u53d1 1KB<\/li>\n\n\n\n<li>\u7b2c 2 \u8f6e\u53d1 2KB<\/li>\n\n\n\n<li>\u7b2c 3 \u8f6e\u53d1 4KB<\/li>\n<\/ul>\n\n\n\n<p>\u5230\u53d1\u9001\u7a97\u53e3<strong>\u7b2c\u4e00\u6b21\u8fbe\u5230 8KB<\/strong>\u8fd9\u4e00\u523b\uff0c\u524d\u9762\u603b\u5171\u5df2\u7ecf\u6210\u529f\u6536\u5230\u7684\u6570\u636e\u91cf\u662f\uff1a<\/p>\n\n\n\n<p><code>1 + 2 + 4 = 7KB<\/code><\/p>\n\n\n\n<p>\u56e0\u4e3a\u4e59\u7684\u63a5\u6536\u7f13\u5b58\u603b\u5171 16KB\uff0c\u800c\u4e14\u9898\u76ee\u8bf4\u53ea\u8fdb\u4e0d\u51fa\uff0c\u6240\u4ee5\u53ef\u7528\u7a7a\u95f4\u8fd8\u5269\uff1a<\/p>\n\n\n\n<p><code>16KB - 7KB = 9KB<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u662f <strong>B<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u9898\u6700\u5bb9\u6613\u9519\u5728\u4e24\u4e2a\u5730\u65b9\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c\u5f88\u591a\u4eba\u4f1a\u628a\u201c\u7a97\u53e3\u8fbe\u5230 8KB\u201d\u8bef\u770b\u6210\u201c\u5df2\u7ecf\u53d1\u51fa\u4e86 8KB\u201d\uff0c\u4e8e\u662f\u628a\u6570\u636e\u91cf\u7b97\u9519\u3002\u5b9e\u9645\u4e0a\u8fd9\u91cc\u662f <strong>cwnd \u589e\u957f\u5230 8KB<\/strong>\uff0c\u800c\u4e0d\u662f\u5df2\u7ecf\u989d\u5916\u53c8\u53d1\u4e86 8KB\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e8c\uff0c\u63a5\u6536\u7f13\u5b58\u5269\u4f59\u7a7a\u95f4\u7b97\u7684\u662f<strong>\u5df2\u7ecf\u6536\u5230\u5e76\u7559\u5728\u7f13\u5b58\u91cc\u7684\u6570\u636e\u91cf<\/strong>\uff0c\u4e0d\u662f\u5f53\u524d\u53d1\u9001\u7a97\u53e3\u5927\u5c0f\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">41. \u4e24\u4e2a\u8fde\u7eed TCP \u6bb5\u7684\u786e\u8ba4\u53f7<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>D\uff0e1000<\/strong><\/p>\n\n\n\n<p>\u8fd9\u9898\u662f\u6700\u6807\u51c6\u7684 <code>seq\/ack<\/code> \u5165\u95e8\u9898\u3002<\/p>\n\n\n\n<p>\u9898\u5e72\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e24\u4e2a\u8fde\u7eed TCP \u6bb5<\/li>\n\n\n\n<li>\u6709\u6548\u8f7d\u8377\u5206\u522b\u4e3a 300B\u3001500B<\/li>\n\n\n\n<li>\u7b2c\u4e00\u4e2a\u6bb5\u7684\u5e8f\u53f7\u662f 200<\/li>\n\n\n\n<li>\u4e3b\u673a\u4e59\u6b63\u786e\u6536\u5230\u8fd9\u4e24\u4e2a\u6570\u636e\u6bb5\u540e\uff0c\u53d1\u56de\u786e\u8ba4\u53f7\u662f\u591a\u5c11<\/li>\n<\/ul>\n\n\n\n<p>\u8981\u8bb0\u4f4f\u4e00\u4e2a\u57fa\u672c\u539f\u5219\uff1a<\/p>\n\n\n\n<p><strong>TCP \u7684\u786e\u8ba4\u53f7 ack = \u671f\u671b\u6536\u5230\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7<\/strong><\/p>\n\n\n\n<p>\u7b2c\u4e00\u4e2a\u6bb5\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq = 200<\/code><\/li>\n\n\n\n<li>\u957f\u5ea6 = 300B<\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u7b2c\u4e00\u4e2a\u6bb5\u8986\u76d6\u7684\u5b57\u8282\u8303\u56f4\u662f\uff1a<\/p>\n\n\n\n<p><code>200 ~ 499<\/code><\/p>\n\n\n\n<p>\u90a3\u4e48\u7b2c\u4e8c\u4e2a\u6bb5\u7684\u8d77\u59cb\u5e8f\u53f7\u5c31\u662f\uff1a<\/p>\n\n\n\n<p><code>500<\/code><\/p>\n\n\n\n<p>\u7b2c\u4e8c\u4e2a\u6bb5\u957f\u5ea6 500B\uff0c\u6240\u4ee5\u8986\u76d6\uff1a<\/p>\n\n\n\n<p><code>500 ~ 999<\/code><\/p>\n\n\n\n<p>\u90a3\u4e48\u63a5\u6536\u65b9\u5728\u6b63\u786e\u6536\u5230\u8fd9\u4e24\u4e2a\u6bb5\u4e4b\u540e\uff0c\u4e0b\u4e00\u5b57\u8282\u5e94\u4e3a\uff1a<\/p>\n\n\n\n<p><code>1000<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u786e\u8ba4\u53f7\u662f <strong>1000<\/strong>\uff0c\u7b54\u6848\u9009 <strong>D<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u7c7b\u9898\u4e00\u5b9a\u4e0d\u8981\u628a\u786e\u8ba4\u53f7\u7406\u89e3\u6210\u201c\u5df2\u7ecf\u6536\u5230\u4e86\u591a\u5c11\u5b57\u8282\u201d\uff0c\u5b83\u4e0d\u662f\u201c\u5b57\u8282\u6570\u201d\uff0c\u800c\u662f<strong>\u4e0b\u4e00\u4e2a\u671f\u671b\u5b57\u8282\u7684\u7f16\u53f7<\/strong>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">42. \u8d85\u65f6\u540e 4 \u4e2a RTT \u7684\u62e5\u585e\u7a97\u53e3<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>C\uff0e9KB<\/strong><\/p>\n\n\n\n<p>\u8fd9\u9898\u662f TCP \u62e5\u585e\u63a7\u5236\u91cc\u7684\u7ecf\u5178\u8003\u6cd5\uff0c\u8003\u7684\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u8d85\u65f6<\/strong>\u53d1\u751f\u540e\u600e\u4e48\u5904\u7406<\/li>\n\n\n\n<li><code>ssthresh<\/code> \u600e\u4e48\u53d8<\/li>\n\n\n\n<li>\u63a5\u4e0b\u6765\u662f\u6162\u5f00\u59cb\u8fd8\u662f\u62e5\u585e\u907f\u514d<\/li>\n<\/ul>\n\n\n\n<p>\u9898\u5e72\u7ed9\u51fa\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4ee5 1KB \u4e3a MSS \u53d1\u9001<\/li>\n\n\n\n<li>\u5f53\u524d <code>cwnd = 16KB<\/code> \u65f6\u53d1\u751f\u8d85\u65f6<\/li>\n\n\n\n<li>\u63a5\u4e0b\u6765 4 \u4e2a RTT \u5185\u4f20\u8f93\u90fd\u6210\u529f<\/li>\n\n\n\n<li>\u95ee\uff1a\u5f53\u7b2c 4 \u4e2a RTT \u5185\u53d1\u9001\u7684\u6240\u6709 TCP \u6bb5\u90fd\u5f97\u5230\u786e\u8ba4\u65f6\uff0c\u62e5\u585e\u7a97\u53e3\u662f\u591a\u5c11<\/li>\n<\/ul>\n\n\n\n<p>\u53d1\u751f<strong>\u8d85\u65f6<\/strong>\u540e\uff0c\u6309\u8003\u7814\u6807\u51c6 TCP \u89c4\u5219\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = cwnd \/ 2 = 8KB<\/code><\/li>\n\n\n\n<li><code>cwnd = 1KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u7136\u540e\u91cd\u65b0\u5f00\u59cb\u53d1\u9001\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u524d 3 \u4e2a RTT\uff1a\u6162\u5f00\u59cb<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u4e2a RTT \u540e\uff1a<code>cwnd = 2KB<\/code><\/li>\n\n\n\n<li>\u7b2c 2 \u4e2a RTT \u540e\uff1a<code>cwnd = 4KB<\/code><\/li>\n\n\n\n<li>\u7b2c 3 \u4e2a RTT \u540e\uff1a<code>cwnd = 8KB<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6b64\u65f6\u5df2\u7ecf\u5230\u8fbe\u95e8\u9650 <code>ssthresh = 8KB<\/code>\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u7b2c 4 \u4e2a RTT\uff1a\u8fdb\u5165\u62e5\u585e\u907f\u514d<\/h3>\n\n\n\n<p>\u8fdb\u5165\u62e5\u585e\u907f\u514d\u540e\uff0c<strong>\u6bcf\u7ecf\u8fc7 1 \u4e2a RTT\uff0ccwnd \u7ebf\u6027\u52a0 1 MSS<\/strong>\uff0c\u4e5f\u5c31\u662f\u52a0 1KB\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u7b2c 4 \u4e2a RTT \u5185\u7684\u62a5\u6587\u90fd\u786e\u8ba4\u540e\uff1a<\/p>\n\n\n\n<p><code>cwnd = 8KB + 1KB = 9KB<\/code><\/p>\n\n\n\n<p>\u7b54\u6848\u5c31\u662f <strong>C<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u9898\u6700\u5e38\u89c1\u7684\u8bef\u533a\u6709\u4e24\u4e2a\u3002<\/p>\n\n\n\n<p>\u4e00\u4e2a\u8bef\u533a\u662f\u628a\u7b2c 4 \u4e2a RTT \u8fd8\u5f53\u6210\u6162\u5f00\u59cb\uff0c\u4e8e\u662f\u7ee7\u7eed\u7ffb\u500d\u5230 16KB\uff0c\u8fd9\u5c31\u9519\u4e86\u3002\u56e0\u4e3a\u6162\u5f00\u59cb\u53ea\u5728 <code>cwnd &lt; ssthresh<\/code> \u65f6\u8fdb\u884c\uff0c\u5230\u4e86\u95e8\u9650\u540e\u5c31\u8be5\u8f6c\u5165\u62e5\u585e\u907f\u514d\u3002<\/p>\n\n\n\n<p>\u53e6\u4e00\u4e2a\u8bef\u533a\u662f\u8ba4\u4e3a\u8d85\u65f6\u540e <code>cwnd<\/code> \u76f4\u63a5\u51cf\u534a\u5230 8KB\uff0c\u8fd9\u4e5f\u4e0d\u5bf9\u3002<strong>\u51cf\u534a\u7684\u662f ssthresh\uff0c\u4e0d\u662f cwnd\uff1b\u8d85\u65f6\u540e cwnd \u8981\u56de\u5230 1 MSS\u3002<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">43. \u540c\u65f6\u53d7 cwnd \u548c rwnd \u7ea6\u675f\u65f6\u8fd8\u80fd\u53d1\u591a\u5c11<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>A\uff0e1000<\/strong><\/p>\n\n\n\n<p>\u8fd9\u9898\u4e13\u95e8\u8003\u201c\u53d1\u9001\u7a97\u53e3\u5230\u5e95\u53d6\u8c01\u201d\u3002<\/p>\n\n\n\n<p>\u9898\u5e72\u7ed9\u51fa\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5df2\u5efa TCP \u8fde\u63a5<\/li>\n\n\n\n<li>MSS = 1000B<\/li>\n\n\n\n<li>\u5f53\u524d <code>cwnd = 4000B<\/code><\/li>\n\n\n\n<li>\u7532\u8fde\u7eed\u53d1\u9001\u4e86\u4e24\u4e2a\u6700\u5927\u6bb5\uff0c\u4e5f\u5c31\u662f\u4e00\u5171\u53d1\u4e86 2000B<\/li>\n\n\n\n<li>\u6210\u529f\u6536\u5230\u7b2c\u4e00\u4e2a\u6bb5\u7684\u786e\u8ba4<\/li>\n\n\n\n<li>\u8fd9\u4e2a\u786e\u8ba4\u4e2d\u901a\u544a\u7684\u63a5\u6536\u7a97\u53e3 <code>rwnd = 2000B<\/code><\/li>\n\n\n\n<li>\u95ee\u6b64\u65f6\u7532\u8fd8\u53ef\u4ee5\u53d1\u9001\u7684\u6700\u5927\u5b57\u8282\u6570\u662f\u591a\u5c11<\/li>\n<\/ul>\n\n\n\n<p>TCP \u53d1\u9001\u65b9\u771f\u6b63\u53ef\u53d1\u9001\u7684\u7a97\u53e3\u5927\u5c0f\u662f\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u73b0\u5728\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>cwnd = 4000B<\/code><\/li>\n\n\n\n<li><code>rwnd = 2000B<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u53d1\u9001\u7a97\u53e3\u4e0a\u9650\u53d8\u6210\uff1a<\/p>\n\n\n\n<p><code>min(4000, 2000) = 2000B<\/code><\/p>\n\n\n\n<p>\u4f46\u6ce8\u610f\uff0c\u7532\u4e4b\u524d\u5df2\u7ecf\u8fde\u7eed\u53d1\u4e86\u4e24\u4e2a\u6700\u5927\u6bb5\uff0c\u5171 2000B\u3002<br>\u73b0\u5728\u53ea\u6536\u5230\u4e86<strong>\u7b2c\u4e00\u4e2a\u6bb5<\/strong>\u7684\u786e\u8ba4\uff0c\u8bf4\u660e\u8fd8\u6709<strong>\u7b2c\u4e8c\u4e2a\u6bb5 1000B \u4ecd\u5728\u9014\u3001\u672a\u786e\u8ba4<\/strong>\u3002<\/p>\n\n\n\n<p>\u56e0\u6b64\u5f53\u524d\u8fd8\u80fd\u7ee7\u7eed\u53d1\u9001\u7684\u6700\u5927\u5b57\u8282\u6570\u4e3a\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 2000B - \u672a\u786e\u8ba4\u6570\u636e 1000B = 1000B<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u662f <strong>A<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u9898\u6700\u5bb9\u6613\u9519\u5728\u628a\u201c\u63a5\u6536\u7a97\u53e3 2000B\u201d\u76f4\u63a5\u5f53\u6210\u201c\u8fd8\u80fd\u518d\u53d1 2000B\u201d\u3002\u4e0d\u5bf9\uff0c\u56e0\u4e3a\u5176\u4e2d\u5df2\u7ecf\u6709 1000B \u8fd8\u6ca1\u88ab\u786e\u8ba4\uff0c\u5360\u7740\u7a97\u53e3\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">44. \u4e09\u6b21\u63e1\u624b\u7b2c\u4e8c\u6b21\u62a5\u6587\u600e\u4e48\u5224\u65ad<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>C<\/strong><\/p>\n\n\n\n<p>\u9898\u5e72\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7532\u5411\u4e59\u53d1\u9001\u4e00\u4e2a\u8fde\u63a5\u8bf7\u6c42\u6bb5\uff1a<code>SYN = 1, seq = 11220<\/code><\/li>\n\n\n\n<li>\u82e5\u4e59\u63a5\u53d7\u8be5\u8bf7\u6c42<\/li>\n\n\n\n<li>\u95ee\u4e59\u53d1\u56de\u7684\u6b63\u786e TCP \u6bb5\u53ef\u80fd\u662f\u54ea\u4e2a<\/li>\n<\/ul>\n\n\n\n<p>\u5148\u6293\u4f4f\u4e09\u6b21\u63e1\u624b\u7b2c 2 \u6b21\u62a5\u6587\u7684\u6807\u51c6\u5f62\u5f0f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>SYN = 1<\/code><\/li>\n\n\n\n<li><code>ACK = 1<\/code><\/li>\n\n\n\n<li><code>ack = \u5bf9\u65b9seq + 1<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u56e0\u4e3a <strong>SYN \u4f1a\u6d88\u8017\u4e00\u4e2a\u5e8f\u53f7<\/strong>\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u91cc\u4e59\u53d1\u56de\u65f6\uff0c\u786e\u8ba4\u53f7\u5fc5\u987b\u662f\uff1a<\/p>\n\n\n\n<p><code>11220 + 1 = 11221<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64\u81f3\u5c11\u8981\u6ee1\u8db3\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>SYN = 1<\/code><\/li>\n\n\n\n<li><code>ACK = 1<\/code><\/li>\n\n\n\n<li><code>ack = 11221<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u56db\u4e2a\u9009\u9879\u91cc\u53ea\u6709 <strong>C<\/strong> \u7b26\u5408\uff1a<\/p>\n\n\n\n<p><code>(SYN=1, ACK=1, seq=11221, ack=11221)<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u7b54\u6848\u662f <strong>C<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u91cc\u8981\u987a\u624b\u5f3a\u8c03\u4e00\u4e2a\u975e\u5e38\u5bb9\u6613\u6df7\u7684\u70b9\uff1a<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><code>seq<\/code> \u548c <code>ack<\/code> \u6ca1\u6709\u5fc5\u7136\u76f8\u7b49\u5173\u7cfb<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ack<\/code> \u662f\u5bf9<strong>\u5bf9\u65b9<\/strong>\u5e8f\u53f7\u7684\u786e\u8ba4<\/li>\n\n\n\n<li><code>seq<\/code> \u662f<strong>\u81ea\u5df1<\/strong>\u8fd9\u8fb9\u5f53\u524d\u62a5\u6587\u6bb5\u7684\u5e8f\u53f7<\/li>\n<\/ul>\n\n\n\n<p>\u53ea\u662f\u5728\u8fd9\u4e2a\u9009\u9879\u9898\u91cc\uff0c\u6b63\u597d\u53ea\u6709 C \u540c\u65f6\u6ee1\u8db3\u63e1\u624b\u683c\u5f0f\u548c\u786e\u8ba4\u89c4\u5219\u3002<br>\u4e25\u683c\u5730\u8bf4\uff0c\u4e59\u7684 <code>seq<\/code> \u662f\u81ea\u5df1\u7684\u521d\u59cb\u5e8f\u53f7\uff0c\u672c\u6765\u53ef\u4ee5\u662f\u522b\u7684\u503c\uff0c\u4e0d\u9700\u8981\u7531\u7532\u7684\u5e8f\u53f7\u63a8\u51fa\u3002\u4f46\u5728\u56db\u4e2a\u9009\u9879\u4e2d\uff0c\u53ea\u6709 C \u662f\u53ef\u80fd\u7684\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">45. \u7d2f\u8ba1\u786e\u8ba4 + \u4e2d\u95f4\u6bb5\u4e22\u5931<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>B\uff0e500<\/strong><\/p>\n\n\n\n<p>\u9898\u5e72\u7ed9\u51fa\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u5df2\u5efa TCP \u8fde\u63a5<\/li>\n\n\n\n<li>\u7532\u53d1\u4e86 3 \u4e2a\u8fde\u7eed TCP \u6bb5<\/li>\n\n\n\n<li>\u6709\u6548\u8f7d\u8377\u5206\u522b\u4e3a 300B\u3001400B\u3001500B<\/li>\n\n\n\n<li>\u7b2c 3 \u4e2a\u6bb5\u7684\u5e8f\u53f7\u4e3a 900<\/li>\n\n\n\n<li>\u4e59\u53ea\u6b63\u786e\u6536\u5230\u7b2c 1 \u4e2a\u6bb5\u548c\u7b2c 3 \u4e2a\u6bb5<\/li>\n\n\n\n<li>\u95ee\u4e59\u53d1\u7ed9\u7532\u7684\u786e\u8ba4\u53f7\u662f\u591a\u5c11<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u9898\u5148\u8981\u53cd\u63a8 3 \u4e2a\u6bb5\u7684\u8d77\u59cb\u5e8f\u53f7\u3002<\/p>\n\n\n\n<p>\u7b2c 3 \u6bb5\u957f\u5ea6 500B\uff0c\u8d77\u59cb\u5e8f\u53f7\u662f 900\u3002<br>\u7b2c 2 \u6bb5\u5728\u5b83\u524d\u9762\uff0c\u957f\u5ea6 400B\uff0c\u6240\u4ee5\u7b2c 2 \u6bb5\u8d77\u59cb\u5e8f\u53f7\u662f\uff1a<\/p>\n\n\n\n<p><code>900 - 400 = 500<\/code><\/p>\n\n\n\n<p>\u7b2c 1 \u6bb5\u957f\u5ea6 300B\uff0c\u6240\u4ee5\u7b2c 1 \u6bb5\u8d77\u59cb\u5e8f\u53f7\u662f\uff1a<\/p>\n\n\n\n<p><code>500 - 300 = 200<\/code><\/p>\n\n\n\n<p>\u4e8e\u662f\u4e09\u4e2a\u6bb5\u5206\u522b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7b2c 1 \u6bb5\uff1a<code>seq = 200<\/code>\uff0c\u957f\u5ea6 300B<\/li>\n\n\n\n<li>\u7b2c 2 \u6bb5\uff1a<code>seq = 500<\/code>\uff0c\u957f\u5ea6 400B<\/li>\n\n\n\n<li>\u7b2c 3 \u6bb5\uff1a<code>seq = 900<\/code>\uff0c\u957f\u5ea6 500B<\/li>\n<\/ul>\n\n\n\n<p>\u73b0\u5728\u4e59\u6536\u5230\u7684\u662f\u7b2c 1 \u6bb5\u548c\u7b2c 3 \u6bb5\uff0c\u4f46<strong>\u7b2c 2 \u6bb5\u6ca1\u6536\u5230<\/strong>\u3002<\/p>\n\n\n\n<p>TCP \u91c7\u7528\u7684\u662f<strong>\u7d2f\u8ba1\u786e\u8ba4<\/strong>\u3002<br>\u4e5f\u5c31\u662f\u8bf4\uff0c\u786e\u8ba4\u53f7\u53ea\u80fd\u786e\u8ba4\u201c\u6309\u5e8f\u8fde\u7eed\u6536\u5230\u7684\u6570\u636e\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u201d\u3002<\/p>\n\n\n\n<p>\u4e59\u5df2\u7ecf\u6309\u5e8f\u6536\u5230\u7b2c 1 \u6bb5\uff0c\u6240\u4ee5\u6b64\u65f6\u4e0b\u4e00\u4e2a\u671f\u5f85\u5b57\u8282\u662f\uff1a<\/p>\n\n\n\n<p><code>200 + 300 = 500<\/code><\/p>\n\n\n\n<p>\u867d\u7136\u7b2c 3 \u6bb5\u4e5f\u5230\u4e86\uff0c\u4f46\u56e0\u4e3a\u7b2c 2 \u6bb5\u7f3a\u5931\uff0c\u4e2d\u95f4\u65ad\u5f00\uff0c\u786e\u8ba4\u53f7<strong>\u4e0d\u80fd\u8df3\u8fc7\u53bb<\/strong>\u786e\u8ba4\u5230 1400\u3002<\/p>\n\n\n\n<p>\u6240\u4ee5\u4e59\u53d1\u56de\u7684\u786e\u8ba4\u53f7\u4ecd\u662f <strong>500<\/strong>\uff0c\u7b54\u6848\u9009 <strong>B<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u9898\u662f\u7d2f\u8ba1\u786e\u8ba4\u7684\u6807\u51c6\u9677\u9631\u9898\u3002<br>\u51e1\u662f\u4e2d\u95f4\u6709\u6d1e\uff0c\u54ea\u6015\u540e\u9762\u7684\u6bb5\u5230\u4e86\uff0c<strong>ack \u4e5f\u5361\u5728\u7f3a\u53e3\u5904\u4e0d\u52a8<\/strong>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">46. \u6536\u5230\u4e00\u4e2a TCP \u6bb5\u540e\u7acb\u5373\u56de\u6bb5\uff0cseq\/ack \u600e\u4e48\u5199<\/h2>\n\n\n\n<p>\u9898\u76ee\u7ed3\u8bba\uff1a<strong>B\uff0e2046\uff0c2013<\/strong><\/p>\n\n\n\n<p>\u9898\u5e72\u8bf4\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7532\u4e59\u4e4b\u95f4\u5df2\u5efa TCP \u8fde\u63a5<\/li>\n\n\n\n<li>\u4e00\u76f4\u5728\u53cc\u5411\u4f20\u8f93\uff0c\u4e14\u65e0\u5dee\u9519\u65e0\u4e22\u5931<\/li>\n\n\n\n<li>\u7532\u6536\u5230\u4e00\u4e2a\u6765\u81ea\u4e59\u7684 TCP \u6bb5\uff1a\n<ul class=\"wp-block-list\">\n<li><code>seq = 1913<\/code><\/li>\n\n\n\n<li><code>ack = 2046<\/code><\/li>\n\n\n\n<li>\u6709\u6548\u8f7d\u8377 = 100B<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\u95ee\u7532\u7acb\u5373\u53d1\u7ed9\u4e59\u7684 TCP \u6bb5\u7684\u5e8f\u53f7\u548c\u786e\u8ba4\u5e8f\u53f7\u5206\u522b\u662f\u591a\u5c11<\/li>\n<\/ul>\n\n\n\n<p>\u5148\u770b\u786e\u8ba4\u53f7 <code>ack<\/code>\u3002<\/p>\n\n\n\n<p>\u4e59\u53d1\u6765\u7684\u8fd9\u4e2a\u6bb5\u4ece\u5b57\u8282 <code>1913<\/code> \u5f00\u59cb\uff0c\u957f\u5ea6 100B\uff0c\u6240\u4ee5\u5305\u542b\u7684\u662f\uff1a<\/p>\n\n\n\n<p><code>1913 ~ 2012<\/code><\/p>\n\n\n\n<p>\u90a3\u4e48\u7532\u6536\u5230\u540e\uff0c\u4e0b\u4e00\u6b65\u671f\u671b\u4e59\u53d1\u9001\u7684\u5b57\u8282\u5e8f\u53f7\u5e94\u4e3a\uff1a<\/p>\n\n\n\n<p><code>2013<\/code><\/p>\n\n\n\n<p>\u6240\u4ee5\u7532\u56de\u7ed9\u4e59\u7684\u786e\u8ba4\u53f7\u5e94\u8be5\u662f\uff1a<\/p>\n\n\n\n<p><code>ack = 2013<\/code><\/p>\n\n\n\n<p>\u518d\u770b\u7532\u81ea\u5df1\u53d1\u9001\u6bb5\u7684\u5e8f\u53f7 <code>seq<\/code>\u3002<\/p>\n\n\n\n<p>\u5bf9\u65b9\u62a5\u6587\u4e2d\u7684 <code>ack = 2046<\/code>\uff0c\u8868\u793a\uff1a<\/p>\n\n\n\n<p><strong>\u4e59\u5df2\u7ecf\u6210\u529f\u6536\u5230\u7532\u53d1\u5230 2045 \u4e3a\u6b62\u7684\u6570\u636e\uff0c\u73b0\u5728\u671f\u5f85\u7532\u4ece 2046 \u5f00\u59cb\u7ee7\u7eed\u53d1\u3002<\/strong><\/p>\n\n\n\n<p>\u6240\u4ee5\u7532\u6b64\u65f6\u7acb\u5373\u53d1\u51fa\u7684 TCP \u6bb5\uff0c\u5176\u5e8f\u53f7\u5e94\u662f\uff1a<\/p>\n\n\n\n<p><code>seq = 2046<\/code><\/p>\n\n\n\n<p>\u56e0\u6b64\u7b54\u6848\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>seq = 2046<\/code><\/li>\n\n\n\n<li><code>ack = 2013<\/code><\/li>\n<\/ul>\n\n\n\n<p>\u4e5f\u5c31\u662f <strong>B<\/strong>\u3002<\/p>\n\n\n\n<p>\u8fd9\u9898\u6700\u5bb9\u6613\u9519\u7684\u662f\u628a\u7eaf\u786e\u8ba4\u6bb5\u4e5f\u5f53\u6210\u201c\u4f1a\u81ea\u52a8\u52a0 1\u201d\u3002<br>\u5b9e\u9645\u4e0a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>SYN<\/strong> \u548c <strong>FIN<\/strong> \u5404\u5360 1 \u4e2a\u5e8f\u53f7<\/li>\n\n\n\n<li><strong>\u7eaf ACK<\/strong> \u5982\u679c\u4e0d\u5e26\u6570\u636e\uff0c<strong>\u4e0d\u989d\u5916\u6d88\u8017\u5e8f\u53f7<\/strong><\/li>\n<\/ul>\n\n\n\n<p>\u6240\u4ee5\u8fd9\u91cc <code>seq<\/code> \u4ecd\u5e94\u662f 2046\uff0c\u4e0d\u662f 2047\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u8fd9 7 \u9898\u80cc\u540e\u5176\u5b9e\u5c31\u662f 5 \u6761\u89c4\u5219<\/h2>\n\n\n\n<p>\u8fd9\u51e0\u9898\u867d\u7136\u770b\u8d77\u6765\u5206\u6563\uff0c\u4f46\u771f\u6b63\u53cd\u590d\u8003\u7684\u5c31\u4e0b\u9762\u51e0\u6761\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e00\uff0c<strong>\u786e\u8ba4\u53f7 ack \u6c38\u8fdc\u8868\u793a\u201c\u671f\u671b\u6536\u5230\u7684\u4e0b\u4e00\u4e2a\u5b57\u8282\u5e8f\u53f7\u201d<\/strong>\u3002<br>\u4e0d\u662f\u201c\u672c\u6b21\u6536\u5230\u7684\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u201d\uff0c\u4e5f\u4e0d\u662f\u201c\u672c\u6b21\u6570\u636e\u957f\u5ea6\u201d\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e8c\uff0c<strong>SYN \u548c FIN \u5404\u6d88\u8017 1 \u4e2a\u5e8f\u53f7\uff0c\u7eaf ACK \u4e0d\u6d88\u8017\u5e8f\u53f7<\/strong>\u3002<br>\u8fd9\u6761\u5728\u63e1\u624b\u3001\u6325\u624b\u9898\u91cc\u6781\u5176\u9ad8\u9891\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e09\uff0c<strong>TCP \u9ed8\u8ba4\u662f\u7d2f\u8ba1\u786e\u8ba4<\/strong>\u3002<br>\u4e2d\u95f4\u6709\u4e00\u4e2a\u6bb5\u6ca1\u5230\uff0c\u540e\u9762\u5373\u4fbf\u5230\u4e86\uff0c\u786e\u8ba4\u53f7\u4e5f\u4e0d\u80fd\u8df3\u8fc7\u53bb\u3002<\/p>\n\n\n\n<p>\u7b2c\u56db\uff0c\u53d1\u9001\u65b9\u771f\u6b63\u80fd\u53d1\u591a\u5c11\uff0c\u53d6\u51b3\u4e8e\uff1a<\/p>\n\n\n\n<p><code>\u53d1\u9001\u7a97\u53e3 = min(cwnd, rwnd)<\/code><\/p>\n\n\n\n<p>\u5982\u679c\u8fd8\u6709\u672a\u786e\u8ba4\u6570\u636e\u5728\u8def\u4e0a\uff0c\u8fd8\u8981\u518d\u51cf\u6389\u8fd9\u90e8\u5206\u3002<\/p>\n\n\n\n<p>\u7b2c\u4e94\uff0c<strong>\u8d85\u65f6<\/strong>\u540e\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ssthresh = \u5f53\u524dcwnd \/ 2<\/code><\/li>\n\n\n\n<li><code>cwnd = 1 MSS<\/code><\/li>\n\n\n\n<li>\u7136\u540e\u91cd\u65b0\u6162\u5f00\u59cb\uff0c\u5230\u95e8\u9650\u540e\u8f6c\u62e5\u585e\u907f\u514d<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>TCP \u6700\u5bb9\u6613\u6df7\u7684\u51e0\u4e2a\u70b9\u4e0a\uff1aSYN\/FIN \u662f\u5426\u5360\u5e8f\u53f7\u3001seq \u548c ack \u5230\u5e95\u5404\u8868\u793a\u4ec0\u4e48\u3001\u6325\u624b\u65f6 FIN \u5230 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[54],"tags":[],"class_list":["post-2081","post","type-post","status-publish","format-standard","hentry","category-text"],"_links":{"self":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2081","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/comments?post=2081"}],"version-history":[{"count":3,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2081\/revisions"}],"predecessor-version":[{"id":2164,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/posts\/2081\/revisions\/2164"}],"wp:attachment":[{"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/media?parent=2081"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/categories?post=2081"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.preluna.xyz\/index.php\/wp-json\/wp\/v2\/tags?post=2081"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}