为什么客户端 tcp 有时不发送 ACK，导致重传？
这是我所拥有的：
客户端（192.168.11.121）：Windows Vista，Firefox
服务器端（192.168.11.16）：Windows 2003，在客户端上运行的我的网络服务器或 IIS
Fiddler 显示某些图像的下载时间比其他图像长得多，即使图像大小相同。我运行了客户端数据包跟踪，发现“快”和“慢”下载之间的区别在于，对于慢速下载，客户端快速接收数据但不发送 ACK，导致服务器重新传输。下面的第一个跟踪包含成功的请求和缓慢的请求。
成功的图片请求： 1132是来自浏览器的图片请求 1133-1155 是响应。当服务器发送数据包时，客户端会在数据包到达时对其进行确认
带有重传的图像请求： 1159是来自浏览器的图片请求 1160-1182 是响应。这次客户端没有确认数据包。 1183 是从客户端到服务器的重复确认 - 为什么？
我读过有关延迟 ACK 的内容，但我认为条件不适用，因为客户端应该至少确认每个其他数据包，对吗？
客户端是否认为存在丢失的数据包，因此不发送确认？是否有丢失的数据包？如果是这样，我看不到。
我已经尝试了两台客户端计算机与该服务器 - 问题都出现了。这两个客户端都可以从运行相同操作系统和网络服务器的其他服务器上正常下载图像。所以我认为这是服务器端的问题，但是什么呢？
No. Time Source Destination Protocol Info
1132 7.217259 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=6097 Ack=75896 Win=65700 Len=1016
1133 7.219314 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=75896 Ack=7113 Win=64519 Len=1460
1134 7.219318 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=77356 Ack=7113 Win=64519 Len=1460
1135 7.219339 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=78816 Win=65700 Len=0
1136 7.219654 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=78816 Ack=7113 Win=64519 Len=1460
1137 7.219656 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=80276 Ack=7113 Win=64519 Len=1460
1138 7.219659 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=81736 Ack=7113 Win=64519 Len=1460
1139 7.219675 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=83196 Win=65700 Len=0
1140 7.219978 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=83196 Ack=7113 Win=64519 Len=1460
1141 7.219980 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=84656 Ack=7113 Win=64519 Len=1460
1142 7.219991 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=86116 Win=65700 Len=0
1143 7.220310 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=86116 Ack=7113 Win=64519 Len=1460
1144 7.220313 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=87576 Ack=7113 Win=64519 Len=1460
1145 7.220315 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=89036 Ack=7113 Win=64519 Len=1460
1146 7.220327 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=90496 Win=65700 Len=0
1147 7.220645 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=90496 Ack=7113 Win=64519 Len=1460
1148 7.220647 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=91956 Ack=7113 Win=64519 Len=1460
1149 7.220649 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=93416 Ack=7113 Win=64519 Len=1460
1150 7.220662 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=94876 Win=65700 Len=0
1151 7.220976 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=94876 Ack=7113 Win=64519 Len=1460
1152 7.220978 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=96336 Ack=7113 Win=64519 Len=1460
1153 7.220989 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=97796 Win=65700 Len=0
1154 7.221316 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=97796 Ack=7113 Win=64519 Len=1460
1155 7.221319 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [PSH, ACK] Seq=99256 Ack=7113 Win=64519 Len=710
1156 7.221335 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=99966 Win=65700 Len=0
1159 7.414879 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=7113 Ack=99966 Win=65700 Len=1016
1160 7.417006 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=99966 Ack=8129 Win=65535 Len=1460
1161 7.417009 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=101426 Ack=8129 Win=65535 Len=1460
1162 7.417337 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=102886 Ack=8129 Win=65535 Len=1460
1163 7.417339 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=104346 Ack=8129 Win=65535 Len=1460
1164 7.417343 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=105806 Ack=8129 Win=65535 Len=1460
1165 7.417661 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=107266 Ack=8129 Win=65535 Len=1460
1166 7.417664 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=108726 Ack=8129 Win=65535 Len=1460
1167 7.418004 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=110186 Ack=8129 Win=65535 Len=1460
1168 7.418006 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=111646 Ack=8129 Win=65535 Len=1460
1169 7.418008 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=113106 Ack=8129 Win=65535 Len=1460
1170 7.418336 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=114566 Ack=8129 Win=65535 Len=1460
1171 7.418339 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=116026 Ack=8129 Win=65535 Len=1460
1172 7.418342 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=117486 Ack=8129 Win=65535 Len=1460
1173 7.418674 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=118946 Ack=8129 Win=65535 Len=1460
1174 7.418677 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=120406 Ack=8129 Win=65535 Len=1460
1175 7.419002 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=121866 Ack=8129 Win=65535 Len=1460
1176 7.419004 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=123326 Ack=8129 Win=65535 Len=1460
1177 7.419007 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=124786 Ack=8129 Win=65535 Len=1460
1178 7.419375 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=126246 Ack=8129 Win=65535 Len=1460
1179 7.419378 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=127706 Ack=8129 Win=65535 Len=1460
1180 7.419708 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=129166 Ack=8129 Win=65535 Len=1460
1181 7.419710 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=130626 Ack=8129 Win=65535 Len=1460
1182 7.419712 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [PSH, ACK] Seq=132086 Ack=8129 Win=65535 Len=316
1183 7.419741 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 1159#1] 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=99966 Win=65700 Len=0 SLE=132086 SRE=132402
1186 7.617479 192.168.11.16 192.168.11.121 TCP [TCP Dup ACK 1182#1] ddi-tcp-1 > 60781 [ACK] Seq=132402 Ack=8129 Win=65535 Len=0
1187 7.742696 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=99966 Ack=8129 Win=65535 Len=1460
1188 7.939708 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=101426 Win=65700 Len=0 SLE=132086 SRE=132402
1189 7.940725 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=101426 Ack=8129 Win=65535 Len=1460
1190 7.940727 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=102886 Ack=8129 Win=65535 Len=1460
1191 7.940750 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=104346 Win=65700 Len=0 SLE=132086 SRE=132402
1192 7.941698 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=104346 Ack=8129 Win=65535 Len=1460
1193 7.941700 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=105806 Ack=8129 Win=65535 Len=1460
1194 7.941712 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=107266 Win=65700 Len=0 SLE=132086 SRE=132402
1195 7.942030 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=107266 Ack=8129 Win=65535 Len=1460
1196 7.942684 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=108726 Ack=8129 Win=65535 Len=1460
1197 7.942687 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=110186 Ack=8129 Win=65535 Len=1460
1198 7.942700 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=111646 Win=65700 Len=0 SLE=132086 SRE=132402
1199 7.943015 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=111646 Ack=8129 Win=65535 Len=1460
1200 7.943651 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=113106 Ack=8129 Win=65535 Len=1460
1201 7.943653 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=114566 Ack=8129 Win=65535 Len=1460
1202 7.943664 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=116026 Win=65700 Len=0 SLE=132086 SRE=132402
1203 7.943983 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=116026 Ack=8129 Win=65535 Len=1460
1204 7.943985 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=117486 Ack=8129 Win=65535 Len=1460
1205 7.943995 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=118946 Win=65700 Len=0 SLE=132086 SRE=132402
1206 7.944665 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=118946 Ack=8129 Win=65535 Len=1460
1207 7.944667 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=120406 Ack=8129 Win=65535 Len=1460
1208 7.944681 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=121866 Win=65700 Len=0 SLE=132086 SRE=132402
1209 7.944999 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=121866 Ack=8129 Win=65535 Len=1460
1210 7.945002 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=123326 Ack=8129 Win=65535 Len=1460
1211 7.945004 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=124786 Ack=8129 Win=65535 Len=1460
1212 7.945018 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=126246 Win=65700 Len=0 SLE=132086 SRE=132402
1213 7.945330 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=126246 Ack=8129 Win=65535 Len=1460
1214 7.945333 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=127706 Ack=8129 Win=65535 Len=1460
1215 7.945344 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=129166 Win=65700 Len=0 SLE=132086 SRE=132402
1216 7.945664 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=129166 Ack=8129 Win=65535 Len=1460
1217 7.945667 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=130626 Ack=8129 Win=65535 Len=1460
1218 7.945669 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [PSH, ACK] Seq=132086 Ack=8129 Win=65535 Len=316
1219 7.945686 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=132402 Win=65700 Len=0
1220 7.945692 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 1219#1] 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=132402 Win=65700 Len=0 SLE=132086 SRE=132402
1223 8.038426 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=8129 Ack=132402 Win=65700 Len=1016
1224 8.040480 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=132402 Ack=9145 Win=64519 Len=1460
1225 8.040482 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=133862 Ack=9145 Win=64519 Len=1460
1226 8.040499 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=9145 Ack=135322 Win=65700 Len=0
1227 8.040813 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=135322 Ack=9145 Win=64519 Len=1460
1228 8.040815 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=136782 Ack=9145 Win=64519 Len=1460
1229 8.040817 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=138242 Ack=9145 Win=64519 Len=1460
1230 8.040830 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=9145 Ack=139702 Win=65700 Len=0
我看到从该服务器上的 IIS 下载图像的行为相同：
No. Time Source Destination Protocol Info
287 22.257956 192.168.11.121 192.168.11.16 TCP 49387 > http [PSH, ACK] Seq=4531 Ack=86993 Win=65700 Len=869
288 22.261529 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=86993 Ack=5400 Win=65535 Len=1460
289 22.261532 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=88453 Ack=5400 Win=65535 Len=1460
290 22.261859 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=89913 Ack=5400 Win=65535 Len=1460
291 22.261861 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=91373 Ack=5400 Win=65535 Len=1460
292 22.261864 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=92833 Ack=5400 Win=65535 Len=1460
293 22.262194 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=94293 Ack=5400 Win=65535 Len=1460
294 22.262196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=95753 Ack=5400 Win=65535 Len=1460
295 22.262526 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=97213 Ack=5400 Win=65535 Len=1460
296 22.262527 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=98673 Ack=5400 Win=65535 Len=1460
297 22.262530 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=100133 Ack=5400 Win=65535 Len=1460
298 22.262858 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=101593 Ack=5400 Win=65535 Len=1460
299 22.262860 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=103053 Ack=5400 Win=65535 Len=1460
300 22.263193 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=104513 Ack=5400 Win=65535 Len=1460
301 22.263196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=105973 Ack=5400 Win=65535 Len=1460
302 22.263197 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=107433 Ack=5400 Win=65535 Len=1460
303 22.263530 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=108893 Ack=5400 Win=65535 Len=1460
304 22.263532 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=110353 Ack=5400 Win=65535 Len=1460
305 22.263534 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=111813 Ack=5400 Win=65535 Len=1460
306 22.263863 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=113273 Ack=5400 Win=65535 Len=1460
307 22.263865 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=114733 Ack=5400 Win=65535 Len=1460
308 22.264196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=116193 Ack=5400 Win=65535 Len=1460
309 22.264198 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=117653 Ack=5400 Win=65535 Len=1460
310 22.264200 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=119113 Ack=5400 Win=65535 Len=1460
311 22.264528 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=120573 Ack=5400 Win=65535 Len=1460
312 22.264531 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=122033 Ack=5400 Win=65535 Len=1460
313 22.264533 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=123493 Ack=5400 Win=65535 Len=1460
314 22.264859 192.168.11.16 192.168.11.121 TCP http > 49387 [PSH, ACK] Seq=124953 Ack=5400 Win=65535 Len=928
315 22.264886 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 287#1] 49387 > http [ACK] Seq=5400 Ack=86993 Win=65700 Len=0 SLE=124953 SRE=125881
324 22.459724 192.168.11.16 192.168.11.121 TCP [TCP Dup ACK 314#1] http > 49387 [ACK] Seq=125881 Ack=5400 Win=65535 Len=0
326 22.788166 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=86993 Ack=5400 Win=65535 Len=1460
330 22.980324 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=88453 Win=65700 Len=0 SLE=124953 SRE=125881
331 22.981699 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=88453 Ack=5400 Win=65535 Len=1460
332 22.981703 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=89913 Ack=5400 Win=65535 Len=1460
333 22.981755 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=91373 Win=65700 Len=0 SLE=124953 SRE=125881
334 22.983025 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=91373 Ack=5400 Win=65535 Len=1460
335 22.983028 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=92833 Ack=5400 Win=65535 Len=1460
336 22.983034 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=94293 Ack=5400 Win=65535 Len=1460
337 22.983085 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=95753 Win=65700 Len=0 SLE=124953 SRE=125881
338 22.984287 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=95753 Ack=5400 Win=65535 Len=1460
339 22.984290 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=97213 Ack=5400 Win=65535 Len=1460
340 22.984292 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=98673 Ack=5400 Win=65535 Len=1460
341 22.984294 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=100133 Ack=5400 Win=65535 Len=1460
342 22.984339 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=101593 Win=65700 Len=0 SLE=124953 SRE=125881
343 22.985373 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=101593 Ack=5400 Win=65535 Len=1460
344 22.985377 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=103053 Ack=5400 Win=65535 Len=1460
345 22.985382 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=104513 Ack=5400 Win=65535 Len=1460
346 22.985435 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=105973 Win=65700 Len=0 SLE=124953 SRE=125881
347 22.985706 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=105973 Ack=5400 Win=65535 Len=1460
348 22.985710 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=107433 Ack=5400 Win=65535 Len=1460
349 22.985753 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=108893 Win=65700 Len=0 SLE=124953 SRE=125881
350 22.986436 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=108893 Ack=5400 Win=65535 Len=1460
351 22.986438 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=110353 Ack=5400 Win=65535 Len=1460
352 22.986459 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=111813 Win=65700 Len=0 SLE=124953 SRE=125881
353 22.987002 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=111813 Ack=5400 Win=65535 Len=1460
354 22.987005 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=113273 Ack=5400 Win=65535 Len=1460
355 22.987011 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=114733 Ack=5400 Win=65535 Len=1460
356 22.987013 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=116193 Ack=5400 Win=65535 Len=1460
357 22.987064 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=117653 Win=65700 Len=0 SLE=124953 SRE=125881
358 22.987174 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=117653 Ack=5400 Win=65535 Len=1460
359 22.987741 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=119113 Ack=5400 Win=65535 Len=1460
360 22.987744 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=120573 Ack=5400 Win=65535 Len=1460
361 22.987747 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=122033 Ack=5400 Win=65535 Len=1460
362 22.987805 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=123493 Win=65700 Len=0 SLE=124953 SRE=125881
363 22.988171 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=123493 Ack=5400 Win=65535 Len=1460
364 22.988175 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [PSH, ACK] Seq=124953 Ack=5400 Win=65535 Len=928
365 22.988219 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=125881 Win=65700 Len=0
366 22.988236 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 365#1] 49387 > http [ACK] Seq=5400 Ack=125881 Win=65700 Len=0 SLE=124953 SRE=125881
409 25.633275 192.168.11.121 192.168.11.16 TCP 49387 > http [PSH, ACK] Seq=5400 Ack=125881 Win=65700 Len=990
Here's what I have:
Client side (192.168.11.121):Windows Vista,Firefox
Server side (192.168.11.16): Windows 2003, My web server or IIS
Fiddler running on the client shows that some images take much longer to download than others, even though images are same size. I ran a client side packet trace and found that the difference between the "fast" and "slow" downloads is that for the slow downloads, the client is receiving the data quickly but not sending ACKs, leading the server to retransmit. The first trace below contains both a successful and a slow request.
A successful image request:
1132 is the image request from the browser
1133-1155 is the response. As the server sends data packets, the client ACKs them as they arrive
An image request with retransmits:
1159 is the image request from the browser
1160-1182 is the response. This time the client is not ACKing the packets.
1183 is a duplicate ack from the client to server - why?
I have read about delayed ACKs but I don't think the conditions apply, as the client should be acking at least every other packet, right?
Does client think there is a missing packet and is therefore not sending the acks? Is there a missing packet? If so, I don't see it.
I have tried 2 client machines with this server - problem manifests for both. Both these clients can download images fine from other servers running same OS and webserver. So I think it's a server side problem, but what?
No. Time Source Destination Protocol Info
1132 7.217259 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=6097 Ack=75896 Win=65700 Len=1016
1133 7.219314 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=75896 Ack=7113 Win=64519 Len=1460
1134 7.219318 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=77356 Ack=7113 Win=64519 Len=1460
1135 7.219339 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=78816 Win=65700 Len=0
1136 7.219654 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=78816 Ack=7113 Win=64519 Len=1460
1137 7.219656 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=80276 Ack=7113 Win=64519 Len=1460
1138 7.219659 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=81736 Ack=7113 Win=64519 Len=1460
1139 7.219675 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=83196 Win=65700 Len=0
1140 7.219978 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=83196 Ack=7113 Win=64519 Len=1460
1141 7.219980 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=84656 Ack=7113 Win=64519 Len=1460
1142 7.219991 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=86116 Win=65700 Len=0
1143 7.220310 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=86116 Ack=7113 Win=64519 Len=1460
1144 7.220313 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=87576 Ack=7113 Win=64519 Len=1460
1145 7.220315 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=89036 Ack=7113 Win=64519 Len=1460
1146 7.220327 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=90496 Win=65700 Len=0
1147 7.220645 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=90496 Ack=7113 Win=64519 Len=1460
1148 7.220647 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=91956 Ack=7113 Win=64519 Len=1460
1149 7.220649 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=93416 Ack=7113 Win=64519 Len=1460
1150 7.220662 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=94876 Win=65700 Len=0
1151 7.220976 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=94876 Ack=7113 Win=64519 Len=1460
1152 7.220978 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=96336 Ack=7113 Win=64519 Len=1460
1153 7.220989 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=97796 Win=65700 Len=0
1154 7.221316 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=97796 Ack=7113 Win=64519 Len=1460
1155 7.221319 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [PSH, ACK] Seq=99256 Ack=7113 Win=64519 Len=710
1156 7.221335 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=7113 Ack=99966 Win=65700 Len=0
1159 7.414879 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=7113 Ack=99966 Win=65700 Len=1016
1160 7.417006 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=99966 Ack=8129 Win=65535 Len=1460
1161 7.417009 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=101426 Ack=8129 Win=65535 Len=1460
1162 7.417337 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=102886 Ack=8129 Win=65535 Len=1460
1163 7.417339 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=104346 Ack=8129 Win=65535 Len=1460
1164 7.417343 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=105806 Ack=8129 Win=65535 Len=1460
1165 7.417661 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=107266 Ack=8129 Win=65535 Len=1460
1166 7.417664 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=108726 Ack=8129 Win=65535 Len=1460
1167 7.418004 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=110186 Ack=8129 Win=65535 Len=1460
1168 7.418006 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=111646 Ack=8129 Win=65535 Len=1460
1169 7.418008 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=113106 Ack=8129 Win=65535 Len=1460
1170 7.418336 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=114566 Ack=8129 Win=65535 Len=1460
1171 7.418339 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=116026 Ack=8129 Win=65535 Len=1460
1172 7.418342 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=117486 Ack=8129 Win=65535 Len=1460
1173 7.418674 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=118946 Ack=8129 Win=65535 Len=1460
1174 7.418677 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=120406 Ack=8129 Win=65535 Len=1460
1175 7.419002 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=121866 Ack=8129 Win=65535 Len=1460
1176 7.419004 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=123326 Ack=8129 Win=65535 Len=1460
1177 7.419007 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=124786 Ack=8129 Win=65535 Len=1460
1178 7.419375 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=126246 Ack=8129 Win=65535 Len=1460
1179 7.419378 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=127706 Ack=8129 Win=65535 Len=1460
1180 7.419708 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=129166 Ack=8129 Win=65535 Len=1460
1181 7.419710 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=130626 Ack=8129 Win=65535 Len=1460
1182 7.419712 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [PSH, ACK] Seq=132086 Ack=8129 Win=65535 Len=316
1183 7.419741 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 1159#1] 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=99966 Win=65700 Len=0 SLE=132086 SRE=132402
1186 7.617479 192.168.11.16 192.168.11.121 TCP [TCP Dup ACK 1182#1] ddi-tcp-1 > 60781 [ACK] Seq=132402 Ack=8129 Win=65535 Len=0
1187 7.742696 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=99966 Ack=8129 Win=65535 Len=1460
1188 7.939708 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=101426 Win=65700 Len=0 SLE=132086 SRE=132402
1189 7.940725 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=101426 Ack=8129 Win=65535 Len=1460
1190 7.940727 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=102886 Ack=8129 Win=65535 Len=1460
1191 7.940750 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=104346 Win=65700 Len=0 SLE=132086 SRE=132402
1192 7.941698 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=104346 Ack=8129 Win=65535 Len=1460
1193 7.941700 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=105806 Ack=8129 Win=65535 Len=1460
1194 7.941712 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=107266 Win=65700 Len=0 SLE=132086 SRE=132402
1195 7.942030 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=107266 Ack=8129 Win=65535 Len=1460
1196 7.942684 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=108726 Ack=8129 Win=65535 Len=1460
1197 7.942687 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=110186 Ack=8129 Win=65535 Len=1460
1198 7.942700 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=111646 Win=65700 Len=0 SLE=132086 SRE=132402
1199 7.943015 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=111646 Ack=8129 Win=65535 Len=1460
1200 7.943651 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=113106 Ack=8129 Win=65535 Len=1460
1201 7.943653 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=114566 Ack=8129 Win=65535 Len=1460
1202 7.943664 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=116026 Win=65700 Len=0 SLE=132086 SRE=132402
1203 7.943983 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=116026 Ack=8129 Win=65535 Len=1460
1204 7.943985 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=117486 Ack=8129 Win=65535 Len=1460
1205 7.943995 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=118946 Win=65700 Len=0 SLE=132086 SRE=132402
1206 7.944665 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=118946 Ack=8129 Win=65535 Len=1460
1207 7.944667 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=120406 Ack=8129 Win=65535 Len=1460
1208 7.944681 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=121866 Win=65700 Len=0 SLE=132086 SRE=132402
1209 7.944999 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=121866 Ack=8129 Win=65535 Len=1460
1210 7.945002 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=123326 Ack=8129 Win=65535 Len=1460
1211 7.945004 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=124786 Ack=8129 Win=65535 Len=1460
1212 7.945018 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=126246 Win=65700 Len=0 SLE=132086 SRE=132402
1213 7.945330 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=126246 Ack=8129 Win=65535 Len=1460
1214 7.945333 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=127706 Ack=8129 Win=65535 Len=1460
1215 7.945344 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=129166 Win=65700 Len=0 SLE=132086 SRE=132402
1216 7.945664 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=129166 Ack=8129 Win=65535 Len=1460
1217 7.945667 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [ACK] Seq=130626 Ack=8129 Win=65535 Len=1460
1218 7.945669 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] ddi-tcp-1 > 60781 [PSH, ACK] Seq=132086 Ack=8129 Win=65535 Len=316
1219 7.945686 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=132402 Win=65700 Len=0
1220 7.945692 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 1219#1] 60781 > ddi-tcp-1 [ACK] Seq=8129 Ack=132402 Win=65700 Len=0 SLE=132086 SRE=132402
1223 8.038426 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [PSH, ACK] Seq=8129 Ack=132402 Win=65700 Len=1016
1224 8.040480 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=132402 Ack=9145 Win=64519 Len=1460
1225 8.040482 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=133862 Ack=9145 Win=64519 Len=1460
1226 8.040499 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=9145 Ack=135322 Win=65700 Len=0
1227 8.040813 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=135322 Ack=9145 Win=64519 Len=1460
1228 8.040815 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=136782 Ack=9145 Win=64519 Len=1460
1229 8.040817 192.168.11.16 192.168.11.121 TCP ddi-tcp-1 > 60781 [ACK] Seq=138242 Ack=9145 Win=64519 Len=1460
1230 8.040830 192.168.11.121 192.168.11.16 TCP 60781 > ddi-tcp-1 [ACK] Seq=9145 Ack=139702 Win=65700 Len=0
I see the same behavior downloading images from IIS on this server:
No. Time Source Destination Protocol Info
287 22.257956 192.168.11.121 192.168.11.16 TCP 49387 > http [PSH, ACK] Seq=4531 Ack=86993 Win=65700 Len=869
288 22.261529 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=86993 Ack=5400 Win=65535 Len=1460
289 22.261532 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=88453 Ack=5400 Win=65535 Len=1460
290 22.261859 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=89913 Ack=5400 Win=65535 Len=1460
291 22.261861 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=91373 Ack=5400 Win=65535 Len=1460
292 22.261864 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=92833 Ack=5400 Win=65535 Len=1460
293 22.262194 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=94293 Ack=5400 Win=65535 Len=1460
294 22.262196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=95753 Ack=5400 Win=65535 Len=1460
295 22.262526 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=97213 Ack=5400 Win=65535 Len=1460
296 22.262527 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=98673 Ack=5400 Win=65535 Len=1460
297 22.262530 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=100133 Ack=5400 Win=65535 Len=1460
298 22.262858 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=101593 Ack=5400 Win=65535 Len=1460
299 22.262860 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=103053 Ack=5400 Win=65535 Len=1460
300 22.263193 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=104513 Ack=5400 Win=65535 Len=1460
301 22.263196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=105973 Ack=5400 Win=65535 Len=1460
302 22.263197 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=107433 Ack=5400 Win=65535 Len=1460
303 22.263530 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=108893 Ack=5400 Win=65535 Len=1460
304 22.263532 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=110353 Ack=5400 Win=65535 Len=1460
305 22.263534 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=111813 Ack=5400 Win=65535 Len=1460
306 22.263863 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=113273 Ack=5400 Win=65535 Len=1460
307 22.263865 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=114733 Ack=5400 Win=65535 Len=1460
308 22.264196 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=116193 Ack=5400 Win=65535 Len=1460
309 22.264198 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=117653 Ack=5400 Win=65535 Len=1460
310 22.264200 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=119113 Ack=5400 Win=65535 Len=1460
311 22.264528 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=120573 Ack=5400 Win=65535 Len=1460
312 22.264531 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=122033 Ack=5400 Win=65535 Len=1460
313 22.264533 192.168.11.16 192.168.11.121 TCP http > 49387 [ACK] Seq=123493 Ack=5400 Win=65535 Len=1460
314 22.264859 192.168.11.16 192.168.11.121 TCP http > 49387 [PSH, ACK] Seq=124953 Ack=5400 Win=65535 Len=928
315 22.264886 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 287#1] 49387 > http [ACK] Seq=5400 Ack=86993 Win=65700 Len=0 SLE=124953 SRE=125881
324 22.459724 192.168.11.16 192.168.11.121 TCP [TCP Dup ACK 314#1] http > 49387 [ACK] Seq=125881 Ack=5400 Win=65535 Len=0
326 22.788166 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=86993 Ack=5400 Win=65535 Len=1460
330 22.980324 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=88453 Win=65700 Len=0 SLE=124953 SRE=125881
331 22.981699 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=88453 Ack=5400 Win=65535 Len=1460
332 22.981703 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=89913 Ack=5400 Win=65535 Len=1460
333 22.981755 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=91373 Win=65700 Len=0 SLE=124953 SRE=125881
334 22.983025 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=91373 Ack=5400 Win=65535 Len=1460
335 22.983028 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=92833 Ack=5400 Win=65535 Len=1460
336 22.983034 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=94293 Ack=5400 Win=65535 Len=1460
337 22.983085 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=95753 Win=65700 Len=0 SLE=124953 SRE=125881
338 22.984287 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=95753 Ack=5400 Win=65535 Len=1460
339 22.984290 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=97213 Ack=5400 Win=65535 Len=1460
340 22.984292 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=98673 Ack=5400 Win=65535 Len=1460
341 22.984294 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=100133 Ack=5400 Win=65535 Len=1460
342 22.984339 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=101593 Win=65700 Len=0 SLE=124953 SRE=125881
343 22.985373 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=101593 Ack=5400 Win=65535 Len=1460
344 22.985377 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=103053 Ack=5400 Win=65535 Len=1460
345 22.985382 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=104513 Ack=5400 Win=65535 Len=1460
346 22.985435 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=105973 Win=65700 Len=0 SLE=124953 SRE=125881
347 22.985706 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=105973 Ack=5400 Win=65535 Len=1460
348 22.985710 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=107433 Ack=5400 Win=65535 Len=1460
349 22.985753 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=108893 Win=65700 Len=0 SLE=124953 SRE=125881
350 22.986436 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=108893 Ack=5400 Win=65535 Len=1460
351 22.986438 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=110353 Ack=5400 Win=65535 Len=1460
352 22.986459 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=111813 Win=65700 Len=0 SLE=124953 SRE=125881
353 22.987002 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=111813 Ack=5400 Win=65535 Len=1460
354 22.987005 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=113273 Ack=5400 Win=65535 Len=1460
355 22.987011 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=114733 Ack=5400 Win=65535 Len=1460
356 22.987013 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=116193 Ack=5400 Win=65535 Len=1460
357 22.987064 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=117653 Win=65700 Len=0 SLE=124953 SRE=125881
358 22.987174 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=117653 Ack=5400 Win=65535 Len=1460
359 22.987741 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=119113 Ack=5400 Win=65535 Len=1460
360 22.987744 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=120573 Ack=5400 Win=65535 Len=1460
361 22.987747 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=122033 Ack=5400 Win=65535 Len=1460
362 22.987805 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=123493 Win=65700 Len=0 SLE=124953 SRE=125881
363 22.988171 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [ACK] Seq=123493 Ack=5400 Win=65535 Len=1460
364 22.988175 192.168.11.16 192.168.11.121 TCP [TCP Retransmission] http > 49387 [PSH, ACK] Seq=124953 Ack=5400 Win=65535 Len=928
365 22.988219 192.168.11.121 192.168.11.16 TCP 49387 > http [ACK] Seq=5400 Ack=125881 Win=65700 Len=0
366 22.988236 192.168.11.121 192.168.11.16 TCP [TCP Dup ACK 365#1] 49387 > http [ACK] Seq=5400 Ack=125881 Win=65700 Len=0 SLE=124953 SRE=125881
409 25.633275 192.168.11.121 192.168.11.16 TCP 49387 > http [PSH, ACK] Seq=5400 Ack=125881 Win=65700 Len=990
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您已经在服务器端（192.168.11.16）运行了监控程序，对吗？
所以你不能直接看到客户端收到了什么数据包。
但是数据包编号 1183（来自客户端 192.168.11.121 的选择性确认）告诉了我们所需要的一切：
客户端从开始到 99966 以及 132086-132401 确认字节。
客户端未收到数据包 1160-1181。收到数据包 1156 和 1182。因此 ack 1183 是由数据包 1182 触发的
。问题不在于服务器或客户端应用程序。
数据包 1160-1181 在主机之间丢失的可能原因有很多。
我们只能开始提问：
两个捕获的问题似乎非常相似：只有最后一个（较小的）数据包通过而没有重传。所以这可能是某种 PMTU 和“不分段”问题。或者只是网卡或交换机损坏。
You have run monitoring program in server side (192.168.11.16), right?
So you don't directly see what packets the client received.
But packet number 1183 (selective ack from client 192.168.11.121) tells all what we need:
Client acknowledge bytes from the begin to 99966, and 132086-132401.
Client did not receive packets 1160-1181. Packets 1156 and 1182 where received. So the ack 1183 was triggered by packet 1182.
The problem is not in server or client application.
There are lot of possible reasons, why packets 1160-1181 were lost between hosts.
We can only start quessing:
Both captured problems seem to be wery similar: Only the last (smaller) packet pass without retransmit. So this could be some kind of PMTU and 'don't fragment' problem. Or just a broken NIC or switch.