{"id":1060,"date":"2021-12-26T22:40:20","date_gmt":"2021-12-26T14:40:20","guid":{"rendered":"https:\/\/blog.cauchyschwarz.com\/?p=1060"},"modified":"2021-12-26T22:40:24","modified_gmt":"2021-12-26T14:40:24","slug":"vegas%e7%ae%97%e6%b3%95%e7%ac%94%e8%ae%b0","status":"publish","type":"post","link":"https:\/\/blog.cauchyschwarz.com\/?p=1060","title":{"rendered":"vegas\u7b97\u6cd5\u7b14\u8bb0"},"content":{"rendered":"\n<p>\u8bba\u6587<\/p>\n\n\n\n<p><a href=\"https:\/\/cseweb.ucsd.edu\/classes\/wi01\/cse222\/papers\/brakmo-vegas-jsac95.pdf\">TCP Vegas: end to end congestion avoidance on a global Internet &#8211; Selected Areas in Communications, IEEE Journal on<\/a><\/p>\n\n\n\n<p>\u6539\u8fdb\u4e4b\u5904<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">1.New Retransmission Mechanism<\/h2>\n\n\n\n<p>\u4ee5\u524d\u7684reno\u5b9e\u73b0(\u6216\u8005\u8bf4tcp\/ip\u534f\u8bae\u6808)\u7684\u8d85\u65f6\u5b9a\u65f6\u5668\u7c92\u5ea6\u592a\u7c97(500ms)\uff0c\u53ea\u6709\u5728\u91cd\u4f20\u8d85\u65f6\u5b9a\u65f6\u5668\u6216\u80053\u6b21\u91cd\u590dack\u65f6\u624d\u4f1a\u53bb\u89e6\u53d1\u68c0\u6d4b\u91cd\u4f20\uff0c\u5bfc\u81f4\u91cd\u4f20\u7684\u5904\u7406\u975e\u5e38\u6ede\u540e\u3002<\/p>\n\n\n\n<p>Vegas\u5219\u505a\u4e86\u6539\u8fdb\uff0c\u5728\u6bcf\u6b21\u6536\u5230\u91cd\u590dack\uff0c\u6216\u8005\u662f\u91cd\u4f20\u4e4b\u540e\u7684\u7b2c1\u4e2a\u6216\u8005\u7b2c2\u4e2aack\uff0c\u4e5f\u8fdb\u884c\u91cd\u4f20\u68c0\u6d4b\uff0c\u4f7f\u5f97\u91cd\u4f20\u66f4\u52a0\u53ca\u65f6\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">2.Congestion Avoidance Mechanism<\/h2>\n\n\n\n<p>Slow-Start\u9636\u6bb5\u7684\u7b97\u6cd5\u7531\u7b2c3\u70b9Modified Slow-Start Mechanism\u63cf\u8ff0\u3002\u8fd9\u90e8\u5206\u53ea\u5bf9\u975eSlow-Start\u9636\u6bb5\u9002\u7528\u3002<\/p>\n\n\n\n<p><strong>BaseRTT<\/strong>\uff1a\u6d4b\u91cf\u5f97\u5230\u7684\u6700\u5c0fRTT\u3002<\/p>\n\n\n\n<p><strong>WindowSize<\/strong>\uff1a\u5f53\u524d\u62e5\u585e\u7a97\u53e3\u3002<\/p>\n\n\n\n<p><strong>Expected<\/strong> (sendrate)\uff1aExpected = WindowSize\/BaseRTT<\/p>\n\n\n\n<p><strong>Actual <\/strong>(sendrate)\uff1a\u8ba1\u7b97\u4e00\u4e2around\u7684\u771f\u5b9e\u53d1\u9001\u901f\u7387\u3002\u8ba1\u7b97\u65b9\u5f0f\u4e3a\uff1a\u8bb0\u5f55\u4e00\u4e2a\u5305\u4ece\u53d1\u51fa\u53bb\u5230\u6536\u5230ack\u671f\u95f4\u603b\u5171\u53d1\u9001\u4e86\u591a\u5c11byte\uff0c\u518d\u9664\u4ee5\u8fd9\u4e2a\u5305\u4ece\u53d1\u51fa\u53bb\u5230\u63a5\u6536\u5230ack\u6240\u82b1\u65f6\u95f4\u3002\u6bcf\u4e2around\u8ba1\u7b97\u4e00\u6b21\u3002<\/p>\n\n\n\n<p><strong>Diff<\/strong>\uff1aDiff = Expected &#8211; Actual<\/p>\n\n\n\n<p>Diff\u4ee3\u8868\u4e86Vegas\u4f30\u8ba1\u7684\u5f53\u524d\u8bbe\u7f6e\u53d1\u9001\u901f\u7387\u4e0e\u94fe\u8def\u74f6\u9888\u901f\u7387\u7684\u5dee\u5f02\u3002<\/p>\n\n\n\n<p>\u5982\u679cDiff &lt; 0\uff1a\u9700\u8981\u66f4\u65b0BaseRTT\u4e3a\u6700\u65b0\u7684RTT\u91c7\u6837\u503c\u3002<\/p>\n\n\n\n<p>\u5982\u679cDiff &gt;= 0\uff1a\u53e6\u5916\u5b9a\u4e49\u4e24\u4e2a\u9608\u503calpha &lt; beta\uff0c<\/p>\n\n\n\n<p>\u5f53Diff &lt; alpha\u65f6\uff0c\u5728\u4e0b\u4e00\u4e2around\u5185\u7ebf\u6027\u589e\u52a0cwnd\uff1b<\/p>\n\n\n\n<p>\u5f53Diff &gt; beta\u65f6\uff0c\u5728\u4e0b\u4e00\u4e2around\u5185\u7ebf\u6027\u51cf\u5c11cwnd\uff1b<\/p>\n\n\n\n<p>\u6863alpht &lt; Diff &lt; beta\u65f6\uff0ccwnd\u7ef4\u6301\u4e0d\u53d8\u3002<\/p>\n\n\n\n<p>\u5b9e\u9645\u5b9e\u73b0\u4e2d\u5e76\u4e0d\u662f\u4f7f\u7528Diff\uff0c\u800c\u662f\u4f7f\u7528Diff*BaseRTT\u6765\u4f30\u8ba1\u53d1\u7aef\u5411\u7f51\u7edc\u53d1\u8d85\u4e86\u591a\u5c11\u6570\u636e\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">3.Modified Slow-Start Mechanism<\/h2>\n\n\n\n<p>vegas\u5728slow-start\u9636\u6bb5\u4e0d\u662f\u548creno\u4e00\u6837\u6bcf\u4e2artt cwnd\u90fd\u5728\u7ffb\u500d\uff0c\u800c\u662f\u6bcf\u96941\u4e2artt\u518d\u5c06cwnd\u7ffb\u500d\u3002\u6bcf\u6b21\u4f7f\u7528\u65b0\u7684cwnd\u53d1\u9001\u65f6\uff0c\u8981\u6301\u7eed\u53d1\u90012\u4e2around\u7684\u65f6\u95f4\uff0c\u5e76\u4e14\u5728\u7b2c2\u4e2around\u53d1\u9001\u7ed3\u675f\u65f6\u6bd4\u8f83Expected sendrate\u548cActual sendrate\u3002\u5982\u679cActual sendrate\u6bd4Expected sendrate\u4f4e\u4e86\uff0c\u518d\u8fdb\u5165\u7ebf\u6027\u8c03\u6574cwnd\u7684\u6a21\u5f0f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u8bba\u6587 TCP Vegas: end to end congestion avoidance on a global Internet &#8211; Selected Areas in Communi&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[123],"class_list":["post-1060","post","type-post","status-publish","format-standard","hentry","category-10","tag-vegas"],"_links":{"self":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/1060","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1060"}],"version-history":[{"count":1,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/1060\/revisions"}],"predecessor-version":[{"id":1061,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=\/wp\/v2\/posts\/1060\/revisions\/1061"}],"wp:attachment":[{"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1060"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1060"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.cauchyschwarz.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1060"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}