On Sat, Aug 4, 2012 at 4:45 PM, Sławek Janecki <jane...@gmail.com> wrote: > I have a node.js client (10.177.62.7) requesting some data from http > rest service from server (10.177.0.1). > Client is simply using nodejs http.request() method (agent=false). > Client is on Ubuntu 11.10 box. > Why client sends FIN ACK after 475ms? Why so slow? He should send FIN > ACK immediately. > I have many situations like this. About 1% of whole traffic is request > with delayed FIN ACK. > Cpu idle on the client is about 99%, so nothing is draining CPU. > How to debug this? What could it be? Is there any sysctl option I need to > tune? > I think this behaviour is the Delayed ACK feature of RFC1122 TCP stack. > > Link to tcpdump picture (done on a client machine) : > http://i48.tinypic.com/35cpogx.png > > Can you tell why kernel delayed that FIN/ACK. > In tcpflow data there is exacly one ACK per packet comming from server. > Why kernel delayed client FIN/ACK. > It could avoid sending ACK every 'data' packet. > But it choose to delay FIN/ACK? > Is this possible? Is this a bug? > > I've also posted question on stackexchange: > http://stackoverflow.com/questions/11711218/client-sends-delayed-fin-ack-500ms-to-server > > Please help.
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