??????????????
????TCP???1974?????????????????30???????????????????????????协?椤�???????绻�???锟�?TCP??????绲�???????????????????????????????锟�????????????胁???
???????????????????????????????????????????????????????????4G????????????????????????????????????????????????????????????????????????????????????????????????????????????
???????????????Linux?????????????????????????????????????????????TCP???些?????????????????????
????????????????????
????????????????????????????????????些????????????TCP Fast Open (TFO)????????????????????????????????????????????????????????????????娑�?????校? Linux???3.6??????3.7???????????

?????????????TCP Fast Open: expediting web services
?????????????????
??????蔚?HTTP??????貌?????HTML??????????????????????????????(Round-Trip Time)??????????????????????????????屑???????????????????????????????????????????????????小????????贸???????????????芯???
????3.0?????????????????(initcwnd)??小?3??????????????????????????????3??MSS????1??MSS?1400????????????4K??????????10???????????13K???????
??????杈�?????校??????????????WEB?????????initcwnd???贸?10??linux???3.0?姹�????????10??????????????????????????谩?
???????????????????????????????????????????????????????些??
???????????????????????小???????未???????????4K????????????????????????????????
?????????????
????Tuning initcwnd for optimum performance
????Optimizing Your Linux Stack for Maximum Mobile Web Performance
????An Argument for Increasing TCP's Initial Congestion Window
??????????????????(Head-of-line blocking?? HOL)
????TCP协??????????????????????????FIFO?????????校????????????????????????????????????????????????????????????????????????????????????????璞�????????谓???????HOL??head-of-line blocking?????????????????????????????????????????效??

????1. ??路???貌?????
????HTTP/2????????????路??????????????????????HTTP/1.*??路???????????????????????????TCP???????????????????????TCP???协????路????????????????????????????小??????路???????????????????
????2. TCP Keepalive?????效
??????????TCP??Keepalive???????????????????????????????????????????????????效??
??????????NFS?????????????????TCP Keepalive??????????????????????????????????Keepalive??效??????????????????????
????3. ?????????????
?????????????????????????????????????????????????????????????????????????????????校??????????????????????????????????????????????协??????"No route to host"??????????????????16???????????????????????????????????锟�???????????????????????????TCPDUMP???????15??????????????"EHOSTUNREACH"??????貌?????????"No route to host"??????
???????澹�????????
???????????????????????????????????????谓???????????????????????锟�??????些????????????????????????????????????????谩?